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LU-4509 ptlrpc: re-enqueue ptlrpcd worker
[fs/lustre-release.git] / lustre / ptlrpc / client.c
index 0913e85..d920faa 100644 (file)
@@ -1,6 +1,4 @@
-/* -*- mode: c; c-basic-offset: 8; indent-tabs-mode: nil; -*-
- * vim:expandtab:shiftwidth=8:tabstop=8:
- *
+/*
  * GPL HEADER START
  *
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  * GPL HEADER END
  */
 /*
- * Copyright  2008 Sun Microsystems, Inc. All rights reserved
+ * Copyright (c) 2002, 2010, Oracle and/or its affiliates. All rights reserved.
  * Use is subject to license terms.
+ *
+ * Copyright (c) 2011, 2013, Intel Corporation.
  */
 /*
  * This file is part of Lustre, http://www.lustre.org/
  * Lustre is a trademark of Sun Microsystems, Inc.
  */
 
+/** Implementation of client-side PortalRPC interfaces */
+
 #define DEBUG_SUBSYSTEM S_RPC
 #ifndef __KERNEL__
 #include <errno.h>
 
 #include "ptlrpc_internal.h"
 
+static int ptlrpc_send_new_req(struct ptlrpc_request *req);
+static int ptlrpcd_check_work(struct ptlrpc_request *req);
+
+/**
+ * Initialize passed in client structure \a cl.
+ */
 void ptlrpc_init_client(int req_portal, int rep_portal, char *name,
                         struct ptlrpc_client *cl)
 {
@@ -57,7 +65,11 @@ void ptlrpc_init_client(int req_portal, int rep_portal, char *name,
         cl->cli_reply_portal   = rep_portal;
         cl->cli_name           = name;
 }
+EXPORT_SYMBOL(ptlrpc_init_client);
 
+/**
+ * Return PortalRPC connection for remore uud \a uuid
+ */
 struct ptlrpc_connection *ptlrpc_uuid_to_connection(struct obd_uuid *uuid)
 {
         struct ptlrpc_connection *c;
@@ -65,9 +77,12 @@ struct ptlrpc_connection *ptlrpc_uuid_to_connection(struct obd_uuid *uuid)
         lnet_process_id_t         peer;
         int                       err;
 
+       /* ptlrpc_uuid_to_peer() initializes its 2nd parameter
+        * before accessing its values. */
+       /* coverity[uninit_use_in_call] */
         err = ptlrpc_uuid_to_peer(uuid, &peer, &self);
         if (err != 0) {
-                CERROR("cannot find peer %s!\n", uuid->uuid);
+                CNETERR("cannot find peer %s!\n", uuid->uuid);
                 return NULL;
         }
 
@@ -81,37 +96,58 @@ struct ptlrpc_connection *ptlrpc_uuid_to_connection(struct obd_uuid *uuid)
 
         return c;
 }
+EXPORT_SYMBOL(ptlrpc_uuid_to_connection);
 
-static inline struct ptlrpc_bulk_desc *new_bulk(int npages, int type, int portal)
+/**
+ * Allocate and initialize new bulk descriptor on the sender.
+ * Returns pointer to the descriptor or NULL on error.
+ */
+struct ptlrpc_bulk_desc *ptlrpc_new_bulk(unsigned npages, unsigned max_brw,
+                                        unsigned type, unsigned portal)
 {
-        struct ptlrpc_bulk_desc *desc;
+       struct ptlrpc_bulk_desc *desc;
+       int i;
 
-        OBD_ALLOC(desc, offsetof (struct ptlrpc_bulk_desc, bd_iov[npages]));
-        if (!desc)
-                return NULL;
+       OBD_ALLOC(desc, offsetof(struct ptlrpc_bulk_desc, bd_iov[npages]));
+       if (!desc)
+               return NULL;
 
-        spin_lock_init(&desc->bd_lock);
-        cfs_waitq_init(&desc->bd_waitq);
-        desc->bd_max_iov = npages;
-        desc->bd_iov_count = 0;
-        LNetInvalidateHandle(&desc->bd_md_h);
-        desc->bd_portal = portal;
-        desc->bd_type = type;
+       spin_lock_init(&desc->bd_lock);
+       init_waitqueue_head(&desc->bd_waitq);
+       desc->bd_max_iov = npages;
+       desc->bd_iov_count = 0;
+       desc->bd_portal = portal;
+       desc->bd_type = type;
+       desc->bd_md_count = 0;
+       LASSERT(max_brw > 0);
+       desc->bd_md_max_brw = min(max_brw, PTLRPC_BULK_OPS_COUNT);
+       /* PTLRPC_BULK_OPS_COUNT is the compile-time transfer limit for this
+        * node. Negotiated ocd_brw_size will always be <= this number. */
+       for (i = 0; i < PTLRPC_BULK_OPS_COUNT; i++)
+               LNetInvalidateHandle(&desc->bd_mds[i]);
 
-        return desc;
+       return desc;
 }
 
+/**
+ * Prepare bulk descriptor for specified outgoing request \a req that
+ * can fit \a npages * pages. \a type is bulk type. \a portal is where
+ * the bulk to be sent. Used on client-side.
+ * Returns pointer to newly allocatrd initialized bulk descriptor or NULL on
+ * error.
+ */
 struct ptlrpc_bulk_desc *ptlrpc_prep_bulk_imp(struct ptlrpc_request *req,
-                                              int npages, int type, int portal)
+                                             unsigned npages, unsigned max_brw,
+                                             unsigned type, unsigned portal)
 {
-        struct obd_import *imp = req->rq_import;
-        struct ptlrpc_bulk_desc *desc;
+       struct obd_import *imp = req->rq_import;
+       struct ptlrpc_bulk_desc *desc;
 
-        ENTRY;
-        LASSERT(type == BULK_PUT_SINK || type == BULK_GET_SOURCE);
-        desc = new_bulk(npages, type, portal);
-        if (desc == NULL)
-                RETURN(NULL);
+       ENTRY;
+       LASSERT(type == BULK_PUT_SINK || type == BULK_GET_SOURCE);
+       desc = ptlrpc_new_bulk(npages, max_brw, type, portal);
+       if (desc == NULL)
+               RETURN(NULL);
 
         desc->bd_import_generation = req->rq_import_generation;
         desc->bd_import = class_import_get(imp);
@@ -125,68 +161,67 @@ struct ptlrpc_bulk_desc *ptlrpc_prep_bulk_imp(struct ptlrpc_request *req,
 
         return desc;
 }
+EXPORT_SYMBOL(ptlrpc_prep_bulk_imp);
 
-struct ptlrpc_bulk_desc *ptlrpc_prep_bulk_exp(struct ptlrpc_request *req,
-                                              int npages, int type, int portal)
+/*
+ * Add a page \a page to the bulk descriptor \a desc.
+ * Data to transfer in the page starts at offset \a pageoffset and
+ * amount of data to transfer from the page is \a len
+ */
+void __ptlrpc_prep_bulk_page(struct ptlrpc_bulk_desc *desc,
+                            struct page *page, int pageoffset, int len, int pin)
 {
-        struct obd_export *exp = req->rq_export;
-        struct ptlrpc_bulk_desc *desc;
-
-        ENTRY;
-        LASSERT(type == BULK_PUT_SOURCE || type == BULK_GET_SINK);
-
-        desc = new_bulk(npages, type, portal);
-        if (desc == NULL)
-                RETURN(NULL);
-
-        desc->bd_export = class_export_get(exp);
-        desc->bd_req = req;
+       LASSERT(desc->bd_iov_count < desc->bd_max_iov);
+       LASSERT(page != NULL);
+       LASSERT(pageoffset >= 0);
+       LASSERT(len > 0);
+       LASSERT(pageoffset + len <= PAGE_CACHE_SIZE);
 
-        desc->bd_cbid.cbid_fn  = server_bulk_callback;
-        desc->bd_cbid.cbid_arg = desc;
+       desc->bd_nob += len;
 
-        /* NB we don't assign rq_bulk here; server-side requests are
-         * re-used, and the handler frees the bulk desc explicitly. */
+       if (pin)
+               page_cache_get(page);
 
-        return desc;
+       ptlrpc_add_bulk_page(desc, page, pageoffset, len);
 }
+EXPORT_SYMBOL(__ptlrpc_prep_bulk_page);
 
-void ptlrpc_prep_bulk_page(struct ptlrpc_bulk_desc *desc,
-                           cfs_page_t *page, int pageoffset, int len)
+/**
+ * Uninitialize and free bulk descriptor \a desc.
+ * Works on bulk descriptors both from server and client side.
+ */
+void __ptlrpc_free_bulk(struct ptlrpc_bulk_desc *desc, int unpin)
 {
-        LASSERT(desc->bd_iov_count < desc->bd_max_iov);
-        LASSERT(page != NULL);
-        LASSERT(pageoffset >= 0);
-        LASSERT(len > 0);
-        LASSERT(pageoffset + len <= CFS_PAGE_SIZE);
+       int i;
+       ENTRY;
 
-        desc->bd_nob += len;
-
-        ptlrpc_add_bulk_page(desc, page, pageoffset, len);
-}
-
-void ptlrpc_free_bulk(struct ptlrpc_bulk_desc *desc)
-{
-        ENTRY;
+       LASSERT(desc != NULL);
+       LASSERT(desc->bd_iov_count != LI_POISON); /* not freed already */
+       LASSERT(desc->bd_md_count == 0);         /* network hands off */
+       LASSERT((desc->bd_export != NULL) ^ (desc->bd_import != NULL));
 
-        LASSERT(desc != NULL);
-        LASSERT(desc->bd_iov_count != LI_POISON); /* not freed already */
-        LASSERT(!desc->bd_network_rw);         /* network hands off or */
-        LASSERT((desc->bd_export != NULL) ^ (desc->bd_import != NULL));
+       sptlrpc_enc_pool_put_pages(desc);
 
-        sptlrpc_enc_pool_put_pages(desc);
+       if (desc->bd_export)
+               class_export_put(desc->bd_export);
+       else
+               class_import_put(desc->bd_import);
 
-        if (desc->bd_export)
-                class_export_put(desc->bd_export);
-        else
-                class_import_put(desc->bd_import);
+       if (unpin) {
+               for (i = 0; i < desc->bd_iov_count ; i++)
+                       page_cache_release(desc->bd_iov[i].kiov_page);
+       }
 
-        OBD_FREE(desc, offsetof(struct ptlrpc_bulk_desc,
-                                bd_iov[desc->bd_max_iov]));
-        EXIT;
+       OBD_FREE(desc, offsetof(struct ptlrpc_bulk_desc,
+                               bd_iov[desc->bd_max_iov]));
+       EXIT;
 }
+EXPORT_SYMBOL(__ptlrpc_free_bulk);
 
-/* Set server timelimit for this req */
+/**
+ * Set server timelimit for this req, i.e. how long are we willing to wait
+ * for reply before timing out this request.
+ */
 void ptlrpc_at_set_req_timeout(struct ptlrpc_request *req)
 {
         __u32 serv_est;
@@ -197,17 +232,22 @@ void ptlrpc_at_set_req_timeout(struct ptlrpc_request *req)
 
         if (AT_OFF) {
                 /* non-AT settings */
+                /**
+                 * \a imp_server_timeout means this is reverse import and
+                 * we send (currently only) ASTs to the client and cannot afford
+                 * to wait too long for the reply, otherwise the other client
+                 * (because of which we are sending this request) would
+                 * timeout waiting for us
+                 */
                 req->rq_timeout = req->rq_import->imp_server_timeout ?
-                        obd_timeout / 2 : obd_timeout;
-                lustre_msg_set_timeout(req->rq_reqmsg, req->rq_timeout);
-                return;
+                                  obd_timeout / 2 : obd_timeout;
+        } else {
+                at = &req->rq_import->imp_at;
+                idx = import_at_get_index(req->rq_import,
+                                          req->rq_request_portal);
+                serv_est = at_get(&at->iat_service_estimate[idx]);
+                req->rq_timeout = at_est2timeout(serv_est);
         }
-
-        at = &req->rq_import->imp_at;
-        idx = import_at_get_index(req->rq_import,
-                                  req->rq_request_portal);
-        serv_est = at_get(&at->iat_service_estimate[idx]);
-        req->rq_timeout = at_est2timeout(serv_est);
         /* We could get even fancier here, using history to predict increased
            loading... */
 
@@ -215,6 +255,7 @@ void ptlrpc_at_set_req_timeout(struct ptlrpc_request *req)
            reqmsg*/
         lustre_msg_set_timeout(req->rq_reqmsg, req->rq_timeout);
 }
+EXPORT_SYMBOL(ptlrpc_at_set_req_timeout);
 
 /* Adjust max service estimate based on server value */
 static void ptlrpc_at_adj_service(struct ptlrpc_request *req,
@@ -224,17 +265,13 @@ static void ptlrpc_at_adj_service(struct ptlrpc_request *req,
         unsigned int oldse;
         struct imp_at *at;
 
-        /* do estimate only if is not in recovery */
-        if (!(req->rq_send_state & (LUSTRE_IMP_FULL | LUSTRE_IMP_CONNECTING)))
-                return;
-
         LASSERT(req->rq_import);
         at = &req->rq_import->imp_at;
 
         idx = import_at_get_index(req->rq_import, req->rq_request_portal);
         /* max service estimates are tracked on the server side,
            so just keep minimal history here */
-        oldse = at_add(&at->iat_service_estimate[idx], serv_est);
+        oldse = at_measured(&at->iat_service_estimate[idx], serv_est);
         if (oldse != 0)
                 CDEBUG(D_ADAPTTO, "The RPC service estimate for %s ptl %d "
                        "has changed from %d to %d\n",
@@ -266,7 +303,7 @@ static void ptlrpc_at_adj_net_latency(struct ptlrpc_request *req,
                       CFS_DURATION_T"\n", service_time,
                       cfs_time_sub(now, req->rq_sent));
 
-        oldnl = at_add(&at->iat_net_latency, nl);
+        oldnl = at_measured(&at->iat_net_latency, nl);
         if (oldnl != 0)
                 CDEBUG(D_ADAPTTO, "The network latency for %s (nid %s) "
                        "has changed from %d to %d\n",
@@ -280,13 +317,12 @@ static int unpack_reply(struct ptlrpc_request *req)
 {
         int rc;
 
-        /* Clear reply swab mask; we may have already swabbed an early reply */
-        req->rq_rep_swab_mask = 0;
-
-        rc = lustre_unpack_msg(req->rq_repmsg, req->rq_replen);
-        if (rc) {
-                DEBUG_REQ(D_ERROR, req, "unpack_rep failed: %d", rc);
-                return(-EPROTO);
+        if (SPTLRPC_FLVR_POLICY(req->rq_flvr.sf_rpc) != SPTLRPC_POLICY_NULL) {
+                rc = ptlrpc_unpack_rep_msg(req, req->rq_replen);
+                if (rc) {
+                        DEBUG_REQ(D_ERROR, req, "unpack_rep failed: %d", rc);
+                        return(-EPROTO);
+                }
         }
 
         rc = lustre_unpack_rep_ptlrpc_body(req, MSG_PTLRPC_BODY_OFF);
@@ -297,7 +333,7 @@ static int unpack_reply(struct ptlrpc_request *req)
         return 0;
 }
 
-/*
+/**
  * Handle an early reply message, called with the rq_lock held.
  * If anything goes wrong just ignore it - same as if it never happened
  */
@@ -309,11 +345,11 @@ static int ptlrpc_at_recv_early_reply(struct ptlrpc_request *req)
         ENTRY;
 
         req->rq_early = 0;
-        spin_unlock(&req->rq_lock);
+       spin_unlock(&req->rq_lock);
 
-        rc = sptlrpc_cli_unwrap_early_reply(req, &early_req);
-        if (rc) {
-                spin_lock(&req->rq_lock);
+       rc = sptlrpc_cli_unwrap_early_reply(req, &early_req);
+       if (rc) {
+               spin_lock(&req->rq_lock);
                 RETURN(rc);
         }
 
@@ -328,86 +364,133 @@ static int ptlrpc_at_recv_early_reply(struct ptlrpc_request *req)
 
         sptlrpc_cli_finish_early_reply(early_req);
 
-        spin_lock(&req->rq_lock);
+       if (rc != 0) {
+               spin_lock(&req->rq_lock);
+               RETURN(rc);
+       }
 
-        if (rc == 0) {
-                /* Adjust the local timeout for this req */
-                ptlrpc_at_set_req_timeout(req);
-
-                olddl = req->rq_deadline;
-                /* server assumes it now has rq_timeout from when it sent the
-                   early reply, so client should give it at least that long. */
-                req->rq_deadline = cfs_time_current_sec() + req->rq_timeout +
-                            ptlrpc_at_get_net_latency(req);
-
-                DEBUG_REQ(D_ADAPTTO, req,
-                          "Early reply #%d, new deadline in "CFS_DURATION_T"s "
-                          "("CFS_DURATION_T"s)", req->rq_early_count,
-                          cfs_time_sub(req->rq_deadline,
-                                       cfs_time_current_sec()),
-                          cfs_time_sub(req->rq_deadline, olddl));
-        }
+       /* Adjust the local timeout for this req */
+       ptlrpc_at_set_req_timeout(req);
 
-        RETURN(rc);
+       spin_lock(&req->rq_lock);
+       olddl = req->rq_deadline;
+       /* server assumes it now has rq_timeout from when it sent the
+        * early reply, so client should give it at least that long. */
+       req->rq_deadline = cfs_time_current_sec() + req->rq_timeout +
+                          ptlrpc_at_get_net_latency(req);
+
+       DEBUG_REQ(D_ADAPTTO, req,
+                 "Early reply #%d, new deadline in "CFS_DURATION_T"s "
+                 "("CFS_DURATION_T"s)", req->rq_early_count,
+                 cfs_time_sub(req->rq_deadline, cfs_time_current_sec()),
+                 cfs_time_sub(req->rq_deadline, olddl));
+
+       RETURN(rc);
+}
+
+struct kmem_cache *request_cache;
+
+int ptlrpc_request_cache_init()
+{
+       request_cache = kmem_cache_create("ptlrpc_cache",
+                                         sizeof(struct ptlrpc_request),
+                                         0, SLAB_HWCACHE_ALIGN, NULL);
+       return request_cache == NULL ? -ENOMEM : 0;
+}
+
+void ptlrpc_request_cache_fini()
+{
+       kmem_cache_destroy(request_cache);
 }
 
+struct ptlrpc_request *ptlrpc_request_cache_alloc(int flags)
+{
+       struct ptlrpc_request *req;
+
+       OBD_SLAB_ALLOC_PTR_GFP(req, request_cache, flags);
+       return req;
+}
+
+void ptlrpc_request_cache_free(struct ptlrpc_request *req)
+{
+       OBD_SLAB_FREE_PTR(req, request_cache);
+}
+
+/**
+ * Wind down request pool \a pool.
+ * Frees all requests from the pool too
+ */
 void ptlrpc_free_rq_pool(struct ptlrpc_request_pool *pool)
 {
-        struct list_head *l, *tmp;
-        struct ptlrpc_request *req;
+       cfs_list_t *l, *tmp;
+       struct ptlrpc_request *req;
 
-        LASSERT(pool != NULL);
+       LASSERT(pool != NULL);
 
-        spin_lock(&pool->prp_lock);
-        list_for_each_safe(l, tmp, &pool->prp_req_list) {
-                req = list_entry(l, struct ptlrpc_request, rq_list);
-                list_del(&req->rq_list);
-                LASSERT(req->rq_reqbuf);
-                LASSERT(req->rq_reqbuf_len == pool->prp_rq_size);
-                OBD_FREE(req->rq_reqbuf, pool->prp_rq_size);
-                OBD_FREE(req, sizeof(*req));
-        }
-        spin_unlock(&pool->prp_lock);
-        OBD_FREE(pool, sizeof(*pool));
+       spin_lock(&pool->prp_lock);
+       cfs_list_for_each_safe(l, tmp, &pool->prp_req_list) {
+               req = cfs_list_entry(l, struct ptlrpc_request, rq_list);
+               cfs_list_del(&req->rq_list);
+               LASSERT(req->rq_reqbuf);
+               LASSERT(req->rq_reqbuf_len == pool->prp_rq_size);
+               OBD_FREE_LARGE(req->rq_reqbuf, pool->prp_rq_size);
+               ptlrpc_request_cache_free(req);
+       }
+       spin_unlock(&pool->prp_lock);
+       OBD_FREE(pool, sizeof(*pool));
 }
+EXPORT_SYMBOL(ptlrpc_free_rq_pool);
 
+/**
+ * Allocates, initializes and adds \a num_rq requests to the pool \a pool
+ */
 void ptlrpc_add_rqs_to_pool(struct ptlrpc_request_pool *pool, int num_rq)
 {
         int i;
         int size = 1;
 
-        while (size < pool->prp_rq_size + SPTLRPC_MAX_PAYLOAD)
+        while (size < pool->prp_rq_size)
                 size <<= 1;
 
-        LASSERTF(list_empty(&pool->prp_req_list) || size == pool->prp_rq_size,
+        LASSERTF(cfs_list_empty(&pool->prp_req_list) ||
+                 size == pool->prp_rq_size,
                  "Trying to change pool size with nonempty pool "
                  "from %d to %d bytes\n", pool->prp_rq_size, size);
 
-        spin_lock(&pool->prp_lock);
-        pool->prp_rq_size = size;
-        for (i = 0; i < num_rq; i++) {
-                struct ptlrpc_request *req;
-                struct lustre_msg *msg;
-
-                spin_unlock(&pool->prp_lock);
-                OBD_ALLOC(req, sizeof(struct ptlrpc_request));
-                if (!req)
-                        return;
-                OBD_ALLOC_GFP(msg, size, CFS_ALLOC_STD);
-                if (!msg) {
-                        OBD_FREE(req, sizeof(struct ptlrpc_request));
-                        return;
+       spin_lock(&pool->prp_lock);
+       pool->prp_rq_size = size;
+       for (i = 0; i < num_rq; i++) {
+               struct ptlrpc_request *req;
+               struct lustre_msg *msg;
+
+               spin_unlock(&pool->prp_lock);
+               req = ptlrpc_request_cache_alloc(__GFP_IO);
+               if (!req)
+                       return;
+               OBD_ALLOC_LARGE(msg, size);
+               if (!msg) {
+                       ptlrpc_request_cache_free(req);
+                       return;
                 }
                 req->rq_reqbuf = msg;
                 req->rq_reqbuf_len = size;
                 req->rq_pool = pool;
-                spin_lock(&pool->prp_lock);
-                list_add_tail(&req->rq_list, &pool->prp_req_list);
-        }
-        spin_unlock(&pool->prp_lock);
-        return;
+               spin_lock(&pool->prp_lock);
+               cfs_list_add_tail(&req->rq_list, &pool->prp_req_list);
+       }
+       spin_unlock(&pool->prp_lock);
+       return;
 }
+EXPORT_SYMBOL(ptlrpc_add_rqs_to_pool);
 
+/**
+ * Create and initialize new request pool with given attributes:
+ * \a num_rq - initial number of requests to create for the pool
+ * \a msgsize - maximum message size possible for requests in thid pool
+ * \a populate_pool - function to be called when more requests need to be added
+ *                    to the pool
+ * Returns pointer to newly created pool or NULL on error.
+ */
 struct ptlrpc_request_pool *
 ptlrpc_init_rq_pool(int num_rq, int msgsize,
                     void (*populate_pool)(struct ptlrpc_request_pool *, int))
@@ -421,21 +504,25 @@ ptlrpc_init_rq_pool(int num_rq, int msgsize,
         /* Request next power of two for the allocation, because internally
            kernel would do exactly this */
 
-        spin_lock_init(&pool->prp_lock);
+       spin_lock_init(&pool->prp_lock);
         CFS_INIT_LIST_HEAD(&pool->prp_req_list);
-        pool->prp_rq_size = msgsize;
+        pool->prp_rq_size = msgsize + SPTLRPC_MAX_PAYLOAD;
         pool->prp_populate = populate_pool;
 
         populate_pool(pool, num_rq);
 
-        if (list_empty(&pool->prp_req_list)) {
+        if (cfs_list_empty(&pool->prp_req_list)) {
                 /* have not allocated a single request for the pool */
                 OBD_FREE(pool, sizeof (struct ptlrpc_request_pool));
                 pool = NULL;
         }
         return pool;
 }
+EXPORT_SYMBOL(ptlrpc_init_rq_pool);
 
+/**
+ * Fetches one request from pool \a pool
+ */
 static struct ptlrpc_request *
 ptlrpc_prep_req_from_pool(struct ptlrpc_request_pool *pool)
 {
@@ -445,21 +532,21 @@ ptlrpc_prep_req_from_pool(struct ptlrpc_request_pool *pool)
         if (!pool)
                 return NULL;
 
-        spin_lock(&pool->prp_lock);
+       spin_lock(&pool->prp_lock);
 
-        /* See if we have anything in a pool, and bail out if nothing,
-         * in writeout path, where this matters, this is safe to do, because
-         * nothing is lost in this case, and when some in-flight requests
-         * complete, this code will be called again. */
-        if (unlikely(list_empty(&pool->prp_req_list))) {
-                spin_unlock(&pool->prp_lock);
-                return NULL;
-        }
+       /* See if we have anything in a pool, and bail out if nothing,
+        * in writeout path, where this matters, this is safe to do, because
+        * nothing is lost in this case, and when some in-flight requests
+        * complete, this code will be called again. */
+       if (unlikely(cfs_list_empty(&pool->prp_req_list))) {
+               spin_unlock(&pool->prp_lock);
+               return NULL;
+       }
 
-        request = list_entry(pool->prp_req_list.next, struct ptlrpc_request,
-                             rq_list);
-        list_del_init(&request->rq_list);
-        spin_unlock(&pool->prp_lock);
+       request = cfs_list_entry(pool->prp_req_list.next, struct ptlrpc_request,
+                                rq_list);
+       cfs_list_del_init(&request->rq_list);
+       spin_unlock(&pool->prp_lock);
 
         LASSERT(request->rq_reqbuf);
         LASSERT(request->rq_pool);
@@ -473,15 +560,18 @@ ptlrpc_prep_req_from_pool(struct ptlrpc_request_pool *pool)
         return request;
 }
 
+/**
+ * Returns freed \a request to pool.
+ */
 static void __ptlrpc_free_req_to_pool(struct ptlrpc_request *request)
 {
-        struct ptlrpc_request_pool *pool = request->rq_pool;
+       struct ptlrpc_request_pool *pool = request->rq_pool;
 
-        spin_lock(&pool->prp_lock);
-        LASSERT(list_empty(&request->rq_list));
-        LASSERT(!request->rq_receiving_reply);
-        list_add_tail(&request->rq_list, &pool->prp_req_list);
-        spin_unlock(&pool->prp_lock);
+       spin_lock(&pool->prp_lock);
+       LASSERT(cfs_list_empty(&request->rq_list));
+       LASSERT(!request->rq_receiving_reply);
+       cfs_list_add_tail(&request->rq_list, &pool->prp_req_list);
+       spin_unlock(&pool->prp_lock);
 }
 
 static int __ptlrpc_request_bufs_pack(struct ptlrpc_request *request,
@@ -530,27 +620,27 @@ static int __ptlrpc_request_bufs_pack(struct ptlrpc_request *request,
 
         ptlrpc_at_set_req_timeout(request);
 
-        spin_lock_init(&request->rq_lock);
-        CFS_INIT_LIST_HEAD(&request->rq_list);
-        CFS_INIT_LIST_HEAD(&request->rq_timed_list);
-        CFS_INIT_LIST_HEAD(&request->rq_replay_list);
-        CFS_INIT_LIST_HEAD(&request->rq_mod_list);
-        CFS_INIT_LIST_HEAD(&request->rq_ctx_chain);
-        CFS_INIT_LIST_HEAD(&request->rq_set_chain);
-        CFS_INIT_LIST_HEAD(&request->rq_history_list);
-        CFS_INIT_LIST_HEAD(&request->rq_exp_list);
-        cfs_waitq_init(&request->rq_reply_waitq);
-        request->rq_xid = ptlrpc_next_xid();
-        atomic_set(&request->rq_refcount, 1);
-
-        lustre_msg_set_opc(request->rq_reqmsg, opcode);
-
-        RETURN(0);
+       spin_lock_init(&request->rq_lock);
+       CFS_INIT_LIST_HEAD(&request->rq_list);
+       CFS_INIT_LIST_HEAD(&request->rq_timed_list);
+       CFS_INIT_LIST_HEAD(&request->rq_replay_list);
+       CFS_INIT_LIST_HEAD(&request->rq_ctx_chain);
+       CFS_INIT_LIST_HEAD(&request->rq_set_chain);
+       CFS_INIT_LIST_HEAD(&request->rq_history_list);
+       CFS_INIT_LIST_HEAD(&request->rq_exp_list);
+       init_waitqueue_head(&request->rq_reply_waitq);
+       init_waitqueue_head(&request->rq_set_waitq);
+       request->rq_xid = ptlrpc_next_xid();
+       cfs_atomic_set(&request->rq_refcount, 1);
+
+       lustre_msg_set_opc(request->rq_reqmsg, opcode);
+
+       RETURN(0);
 out_ctx:
-        sptlrpc_cli_ctx_put(request->rq_cli_ctx, 1);
+       sptlrpc_cli_ctx_put(request->rq_cli_ctx, 1);
 out_free:
-        class_import_put(imp);
-        return rc;
+       class_import_put(imp);
+       return rc;
 }
 
 int ptlrpc_request_bufs_pack(struct ptlrpc_request *request,
@@ -566,23 +656,57 @@ int ptlrpc_request_bufs_pack(struct ptlrpc_request *request,
 }
 EXPORT_SYMBOL(ptlrpc_request_bufs_pack);
 
+/**
+ * Pack request buffers for network transfer, performing necessary encryption
+ * steps if necessary.
+ */
 int ptlrpc_request_pack(struct ptlrpc_request *request,
                         __u32 version, int opcode)
 {
-        return ptlrpc_request_bufs_pack(request, version, opcode, NULL, NULL);
-}
+       int rc;
+       rc = ptlrpc_request_bufs_pack(request, version, opcode, NULL, NULL);
+       if (rc)
+               return rc;
+
+       /* For some old 1.8 clients (< 1.8.7), they will LASSERT the size of
+        * ptlrpc_body sent from server equal to local ptlrpc_body size, so we
+        * have to send old ptlrpc_body to keep interoprability with these
+        * clients.
+        *
+        * Only three kinds of server->client RPCs so far:
+        *  - LDLM_BL_CALLBACK
+        *  - LDLM_CP_CALLBACK
+        *  - LDLM_GL_CALLBACK
+        *
+        * XXX This should be removed whenever we drop the interoprability with
+        *     the these old clients.
+        */
+       if (opcode == LDLM_BL_CALLBACK || opcode == LDLM_CP_CALLBACK ||
+           opcode == LDLM_GL_CALLBACK)
+               req_capsule_shrink(&request->rq_pill, &RMF_PTLRPC_BODY,
+                                  sizeof(struct ptlrpc_body_v2), RCL_CLIENT);
+
+       return rc;
+}
+EXPORT_SYMBOL(ptlrpc_request_pack);
 
+/**
+ * Helper function to allocate new request on import \a imp
+ * and possibly using existing request from pool \a pool if provided.
+ * Returns allocated request structure with import field filled or
+ * NULL on error.
+ */
 static inline
 struct ptlrpc_request *__ptlrpc_request_alloc(struct obd_import *imp,
                                               struct ptlrpc_request_pool *pool)
 {
-        struct ptlrpc_request *request = NULL;
+       struct ptlrpc_request *request = NULL;
 
-        if (pool)
-                request = ptlrpc_prep_req_from_pool(pool);
+       if (pool)
+               request = ptlrpc_prep_req_from_pool(pool);
 
-        if (!request)
-                OBD_ALLOC_PTR(request);
+       if (!request)
+               request = ptlrpc_request_cache_alloc(__GFP_IO);
 
         if (request) {
                 LASSERTF((unsigned long)imp > 0x1000, "%p", imp);
@@ -599,6 +723,12 @@ struct ptlrpc_request *__ptlrpc_request_alloc(struct obd_import *imp,
         return request;
 }
 
+/**
+ * Helper function for creating a request.
+ * Calls __ptlrpc_request_alloc to allocate new request sturcture and inits
+ * buffer structures according to capsule template \a format.
+ * Returns allocated request structure pointer or NULL on error.
+ */
 static struct ptlrpc_request *
 ptlrpc_request_alloc_internal(struct obd_import *imp,
                               struct ptlrpc_request_pool * pool,
@@ -615,27 +745,49 @@ ptlrpc_request_alloc_internal(struct obd_import *imp,
         return request;
 }
 
+/**
+ * Allocate new request structure for import \a imp and initialize its
+ * buffer structure according to capsule template \a format.
+ */
 struct ptlrpc_request *ptlrpc_request_alloc(struct obd_import *imp,
                                             const struct req_format *format)
 {
         return ptlrpc_request_alloc_internal(imp, NULL, format);
 }
+EXPORT_SYMBOL(ptlrpc_request_alloc);
 
+/**
+ * Allocate new request structure for import \a imp from pool \a pool and
+ * initialize its buffer structure according to capsule template \a format.
+ */
 struct ptlrpc_request *ptlrpc_request_alloc_pool(struct obd_import *imp,
                                             struct ptlrpc_request_pool * pool,
                                             const struct req_format *format)
 {
         return ptlrpc_request_alloc_internal(imp, pool, format);
 }
+EXPORT_SYMBOL(ptlrpc_request_alloc_pool);
 
+/**
+ * For requests not from pool, free memory of the request structure.
+ * For requests obtained from a pool earlier, return request back to pool.
+ */
 void ptlrpc_request_free(struct ptlrpc_request *request)
 {
-        if (request->rq_pool)
-                __ptlrpc_free_req_to_pool(request);
-        else
-                OBD_FREE_PTR(request);
+       if (request->rq_pool)
+               __ptlrpc_free_req_to_pool(request);
+       else
+               ptlrpc_request_cache_free(request);
 }
+EXPORT_SYMBOL(ptlrpc_request_free);
 
+/**
+ * Allocate new request for operatione \a opcode and immediatelly pack it for
+ * network transfer.
+ * Only used for simple requests like OBD_PING where the only important
+ * part of the request is operation itself.
+ * Returns allocated request or NULL on error.
+ */
 struct ptlrpc_request *ptlrpc_request_alloc_pack(struct obd_import *imp,
                                                 const struct req_format *format,
                                                 __u32 version, int opcode)
@@ -652,7 +804,15 @@ struct ptlrpc_request *ptlrpc_request_alloc_pack(struct obd_import *imp,
         }
         return req;
 }
+EXPORT_SYMBOL(ptlrpc_request_alloc_pack);
 
+/**
+ * Prepare request (fetched from pool \a poolif not NULL) on import \a imp
+ * for operation \a opcode. Request would contain \a count buffers.
+ * Sizes of buffers are described in array \a lengths and buffers themselves
+ * are provided by a pointer \a bufs.
+ * Returns prepared request structure pointer or NULL on error.
+ */
 struct ptlrpc_request *
 ptlrpc_prep_req_pool(struct obd_import *imp,
                      __u32 version, int opcode,
@@ -674,7 +834,11 @@ ptlrpc_prep_req_pool(struct obd_import *imp,
         }
         return request;
 }
+EXPORT_SYMBOL(ptlrpc_prep_req_pool);
 
+/**
+ * Same as ptlrpc_prep_req_pool, but without pool
+ */
 struct ptlrpc_request *
 ptlrpc_prep_req(struct obd_import *imp, __u32 version, int opcode, int count,
                 __u32 *lengths, char **bufs)
@@ -682,79 +846,128 @@ ptlrpc_prep_req(struct obd_import *imp, __u32 version, int opcode, int count,
         return ptlrpc_prep_req_pool(imp, version, opcode, count, lengths, bufs,
                                     NULL);
 }
+EXPORT_SYMBOL(ptlrpc_prep_req);
 
+/**
+ * Allocate and initialize new request set structure.
+ * Returns a pointer to the newly allocated set structure or NULL on error.
+ */
 struct ptlrpc_request_set *ptlrpc_prep_set(void)
 {
-        struct ptlrpc_request_set *set;
+       struct ptlrpc_request_set *set;
+
+       ENTRY;
+       OBD_ALLOC(set, sizeof *set);
+       if (!set)
+               RETURN(NULL);
+       cfs_atomic_set(&set->set_refcount, 1);
+       CFS_INIT_LIST_HEAD(&set->set_requests);
+       init_waitqueue_head(&set->set_waitq);
+       cfs_atomic_set(&set->set_new_count, 0);
+       cfs_atomic_set(&set->set_remaining, 0);
+       spin_lock_init(&set->set_new_req_lock);
+       CFS_INIT_LIST_HEAD(&set->set_new_requests);
+       CFS_INIT_LIST_HEAD(&set->set_cblist);
+       set->set_max_inflight = UINT_MAX;
+       set->set_producer     = NULL;
+       set->set_producer_arg = NULL;
+       set->set_rc           = 0;
+
+       RETURN(set);
+}
+EXPORT_SYMBOL(ptlrpc_prep_set);
 
-        ENTRY;
-        OBD_ALLOC(set, sizeof *set);
-        if (!set)
-                RETURN(NULL);
-        CFS_INIT_LIST_HEAD(&set->set_requests);
-        cfs_waitq_init(&set->set_waitq);
-        set->set_remaining = 0;
-        spin_lock_init(&set->set_new_req_lock);
-        CFS_INIT_LIST_HEAD(&set->set_new_requests);
-        CFS_INIT_LIST_HEAD(&set->set_cblist);
+/**
+ * Allocate and initialize new request set structure with flow control
+ * extension. This extension allows to control the number of requests in-flight
+ * for the whole set. A callback function to generate requests must be provided
+ * and the request set will keep the number of requests sent over the wire to
+ * @max_inflight.
+ * Returns a pointer to the newly allocated set structure or NULL on error.
+ */
+struct ptlrpc_request_set *ptlrpc_prep_fcset(int max, set_producer_func func,
+                                            void *arg)
+
+{
+       struct ptlrpc_request_set *set;
+
+       set = ptlrpc_prep_set();
+       if (!set)
+               RETURN(NULL);
 
-        RETURN(set);
+       set->set_max_inflight  = max;
+       set->set_producer      = func;
+       set->set_producer_arg  = arg;
+
+       RETURN(set);
 }
+EXPORT_SYMBOL(ptlrpc_prep_fcset);
 
-/* Finish with this set; opposite of prep_set. */
+/**
+ * Wind down and free request set structure previously allocated with
+ * ptlrpc_prep_set.
+ * Ensures that all requests on the set have completed and removes
+ * all requests from the request list in a set.
+ * If any unsent request happen to be on the list, pretends that they got
+ * an error in flight and calls their completion handler.
+ */
 void ptlrpc_set_destroy(struct ptlrpc_request_set *set)
 {
-        struct list_head *tmp;
-        struct list_head *next;
+        cfs_list_t       *tmp;
+        cfs_list_t       *next;
         int               expected_phase;
         int               n = 0;
         ENTRY;
 
         /* Requests on the set should either all be completed, or all be new */
-        expected_phase = (set->set_remaining == 0) ?
+        expected_phase = (cfs_atomic_read(&set->set_remaining) == 0) ?
                          RQ_PHASE_COMPLETE : RQ_PHASE_NEW;
-        list_for_each (tmp, &set->set_requests) {
+        cfs_list_for_each (tmp, &set->set_requests) {
                 struct ptlrpc_request *req =
-                        list_entry(tmp, struct ptlrpc_request, rq_set_chain);
+                        cfs_list_entry(tmp, struct ptlrpc_request,
+                                       rq_set_chain);
 
                 LASSERT(req->rq_phase == expected_phase);
                 n++;
         }
 
-        LASSERT(set->set_remaining == 0 || set->set_remaining == n);
+        LASSERTF(cfs_atomic_read(&set->set_remaining) == 0 || 
+                 cfs_atomic_read(&set->set_remaining) == n, "%d / %d\n",
+                 cfs_atomic_read(&set->set_remaining), n);
 
-        list_for_each_safe(tmp, next, &set->set_requests) {
+        cfs_list_for_each_safe(tmp, next, &set->set_requests) {
                 struct ptlrpc_request *req =
-                        list_entry(tmp, struct ptlrpc_request, rq_set_chain);
-                list_del_init(&req->rq_set_chain);
+                        cfs_list_entry(tmp, struct ptlrpc_request,
+                                       rq_set_chain);
+                cfs_list_del_init(&req->rq_set_chain);
 
                 LASSERT(req->rq_phase == expected_phase);
 
                 if (req->rq_phase == RQ_PHASE_NEW) {
-
-                        if (req->rq_interpret_reply != NULL) {
-                                ptlrpc_interpterer_t interpreter =
-                                        req->rq_interpret_reply;
-
-                                /* higher level (i.e. LOV) failed;
-                                 * let the sub reqs clean up */
-                                req->rq_status = -EBADR;
-                                interpreter(NULL, req, &req->rq_async_args,
-                                            req->rq_status);
-                        }
-                        set->set_remaining--;
+                        ptlrpc_req_interpret(NULL, req, -EBADR);
+                        cfs_atomic_dec(&set->set_remaining);
                 }
 
-                req->rq_set = NULL;
+               spin_lock(&req->rq_lock);
+               req->rq_set = NULL;
+               req->rq_invalid_rqset = 0;
+               spin_unlock(&req->rq_lock);
+
                 ptlrpc_req_finished (req);
         }
 
-        LASSERT(set->set_remaining == 0);
+        LASSERT(cfs_atomic_read(&set->set_remaining) == 0);
 
-        OBD_FREE(set, sizeof(*set));
+        ptlrpc_reqset_put(set);
         EXIT;
 }
+EXPORT_SYMBOL(ptlrpc_set_destroy);
 
+/**
+ * Add a callback function \a fn to the set.
+ * This function would be called when all requests on this set are completed.
+ * The function will be passed \a data argument.
+ */
 int ptlrpc_set_add_cb(struct ptlrpc_request_set *set,
                       set_interpreter_func fn, void *data)
 {
@@ -766,53 +979,75 @@ int ptlrpc_set_add_cb(struct ptlrpc_request_set *set,
 
         cbdata->psc_interpret = fn;
         cbdata->psc_data = data;
-        list_add_tail(&cbdata->psc_item, &set->set_cblist);
+        cfs_list_add_tail(&cbdata->psc_item, &set->set_cblist);
 
         RETURN(0);
 }
+EXPORT_SYMBOL(ptlrpc_set_add_cb);
 
+/**
+ * Add a new request to the general purpose request set.
+ * Assumes request reference from the caller.
+ */
 void ptlrpc_set_add_req(struct ptlrpc_request_set *set,
                         struct ptlrpc_request *req)
 {
-        /* The set takes over the caller's request reference */
-        list_add_tail(&req->rq_set_chain, &set->set_requests);
-        req->rq_set = set;
-        set->set_remaining++;
+       LASSERT(cfs_list_empty(&req->rq_set_chain));
+
+       /* The set takes over the caller's request reference */
+       cfs_list_add_tail(&req->rq_set_chain, &set->set_requests);
+       req->rq_set = set;
+       cfs_atomic_inc(&set->set_remaining);
+       req->rq_queued_time = cfs_time_current();
+
+       if (req->rq_reqmsg != NULL)
+               lustre_msg_set_jobid(req->rq_reqmsg, NULL);
+
+       if (set->set_producer != NULL)
+               /* If the request set has a producer callback, the RPC must be
+                * sent straight away */
+               ptlrpc_send_new_req(req);
 }
+EXPORT_SYMBOL(ptlrpc_set_add_req);
 
 /**
- * Lock so many callers can add things, the context that owns the set
- * is supposed to notice these and move them into the set proper.
+ * Add a request to a request with dedicated server thread
+ * and wake the thread to make any necessary processing.
+ * Currently only used for ptlrpcd.
  */
-int ptlrpc_set_add_new_req(struct ptlrpcd_ctl *pc,
+void ptlrpc_set_add_new_req(struct ptlrpcd_ctl *pc,
                            struct ptlrpc_request *req)
 {
         struct ptlrpc_request_set *set = pc->pc_set;
+        int count, i;
 
-        /*
-         * Let caller know that we stopped and will not handle this request.
-         * It needs to take care itself of request.
-         */
-        if (test_bit(LIOD_STOP, &pc->pc_flags))
-                return -EALREADY;
-
-        spin_lock(&set->set_new_req_lock);
-        /*
-         * The set takes over the caller's request reference.
-         */
-        list_add_tail(&req->rq_set_chain, &set->set_new_requests);
-        req->rq_set = set;
-        spin_unlock(&set->set_new_req_lock);
-
-        /*
-         * Let thead know that we added something and better it to wake up
-         * and process.
-         */
-        cfs_waitq_signal(&set->set_waitq);
-        return 0;
-}
+        LASSERT(req->rq_set == NULL);
+       LASSERT(test_bit(LIOD_STOP, &pc->pc_flags) == 0);
+
+       spin_lock(&set->set_new_req_lock);
+       /*
+        * The set takes over the caller's request reference.
+        */
+       req->rq_set = set;
+       req->rq_queued_time = cfs_time_current();
+       cfs_list_add_tail(&req->rq_set_chain, &set->set_new_requests);
+       count = cfs_atomic_inc_return(&set->set_new_count);
+       spin_unlock(&set->set_new_req_lock);
+
+       /* Only need to call wakeup once for the first entry. */
+       if (count == 1) {
+               wake_up(&set->set_waitq);
+
+               /* XXX: It maybe unnecessary to wakeup all the partners. But to
+                *      guarantee the async RPC can be processed ASAP, we have
+                *      no other better choice. It maybe fixed in future. */
+               for (i = 0; i < pc->pc_npartners; i++)
+                       wake_up(&pc->pc_partners[i]->pc_set->set_waitq);
+       }
+}
+EXPORT_SYMBOL(ptlrpc_set_add_new_req);
 
-/*
+/**
  * Based on the current state of the import, determine if the request
  * can be sent, is an error, or should be delayed.
  *
@@ -836,99 +1071,104 @@ static int ptlrpc_import_delay_req(struct obd_import *imp,
         } else if (imp->imp_state == LUSTRE_IMP_NEW) {
                 DEBUG_REQ(D_ERROR, req, "Uninitialized import.");
                 *status = -EIO;
-                LBUG();
-        } else if (imp->imp_state == LUSTRE_IMP_CLOSED) {
-                DEBUG_REQ(D_ERROR, req, "IMP_CLOSED ");
+       } else if (imp->imp_state == LUSTRE_IMP_CLOSED) {
+               /* pings may safely race with umount */
+               DEBUG_REQ(lustre_msg_get_opc(req->rq_reqmsg) == OBD_PING ?
+                         D_HA : D_ERROR, req, "IMP_CLOSED ");
+               *status = -EIO;
+        } else if (ptlrpc_send_limit_expired(req)) {
+                /* probably doesn't need to be a D_ERROR after initial testing */
+                DEBUG_REQ(D_ERROR, req, "send limit expired ");
                 *status = -EIO;
         } else if (req->rq_send_state == LUSTRE_IMP_CONNECTING &&
                    imp->imp_state == LUSTRE_IMP_CONNECTING) {
                 /* allow CONNECT even if import is invalid */ ;
-                if (atomic_read(&imp->imp_inval_count) != 0) {
+                if (cfs_atomic_read(&imp->imp_inval_count) != 0) {
                         DEBUG_REQ(D_ERROR, req, "invalidate in flight");
                         *status = -EIO;
                 }
-        } else if ((imp->imp_invalid && (!imp->imp_recon_bk)) ||
-                                         imp->imp_obd->obd_no_recov) {
-                /* If the import has been invalidated (such as by an OST
-                 * failure), and if the import(MGC) tried all of its connection
-                 * list (Bug 13464), the request must fail with -ESHUTDOWN.
-                 * This indicates the requests should be discarded; an -EIO
-                 * may result in a resend of the request. */
-                if (!imp->imp_deactive)
-                          DEBUG_REQ(D_ERROR, req, "IMP_INVALID");
-                *status = -ESHUTDOWN; /* bz 12940 */
-        } else if (req->rq_import_generation != imp->imp_generation) {
+       } else if (imp->imp_invalid || imp->imp_obd->obd_no_recov) {
+               if (!imp->imp_deactive)
+                       DEBUG_REQ(D_NET, req, "IMP_INVALID");
+               *status = -ESHUTDOWN; /* bz 12940 */
+       } else if (req->rq_import_generation != imp->imp_generation) {
                 DEBUG_REQ(D_ERROR, req, "req wrong generation:");
                 *status = -EIO;
         } else if (req->rq_send_state != imp->imp_state) {
                 /* invalidate in progress - any requests should be drop */
-                if (atomic_read(&imp->imp_inval_count) != 0) {
+                if (cfs_atomic_read(&imp->imp_inval_count) != 0) {
                         DEBUG_REQ(D_ERROR, req, "invalidate in flight");
                         *status = -EIO;
                 } else if (imp->imp_dlm_fake || req->rq_no_delay) {
                         *status = -EWOULDBLOCK;
-                } else {
-                        delay = 1;
-                }
-        }
+               } else if (req->rq_allow_replay &&
+                         (imp->imp_state == LUSTRE_IMP_REPLAY ||
+                          imp->imp_state == LUSTRE_IMP_REPLAY_LOCKS ||
+                          imp->imp_state == LUSTRE_IMP_REPLAY_WAIT ||
+                          imp->imp_state == LUSTRE_IMP_RECOVER)) {
+                       DEBUG_REQ(D_HA, req, "allow during recovery.\n");
+               } else {
+                       delay = 1;
+               }
+       }
 
-        RETURN(delay);
+       RETURN(delay);
 }
 
-static int ptlrpc_check_reply(struct ptlrpc_request *req)
+/**
+ * Decide if the eror message regarding provided request \a req
+ * should be printed to the console or not.
+ * Makes it's decision on request status and other properties.
+ * Returns 1 to print error on the system console or 0 if not.
+ */
+static int ptlrpc_console_allow(struct ptlrpc_request *req)
 {
-        int rc = 0;
-        ENTRY;
-
-        /* serialise with network callback */
-        spin_lock(&req->rq_lock);
-
-        if (ptlrpc_client_replied(req))
-                GOTO(out, rc = 1);
-
-        if (req->rq_net_err && !req->rq_timedout) {
-                spin_unlock(&req->rq_lock);
-                rc = ptlrpc_expire_one_request(req, 0);
-                spin_lock(&req->rq_lock);
-                GOTO(out, rc);
-        }
+        __u32 opc;
+        int err;
 
-        if (req->rq_err)
-                GOTO(out, rc = 1);
+        LASSERT(req->rq_reqmsg != NULL);
+        opc = lustre_msg_get_opc(req->rq_reqmsg);
 
-        if (req->rq_resend)
-                GOTO(out, rc = 1);
+        /* Suppress particular reconnect errors which are to be expected.  No
+         * errors are suppressed for the initial connection on an import */
+        if ((lustre_handle_is_used(&req->rq_import->imp_remote_handle)) &&
+            (opc == OST_CONNECT || opc == MDS_CONNECT || opc == MGS_CONNECT)) {
 
-        if (req->rq_restart)
-                GOTO(out, rc = 1);
+                /* Suppress timed out reconnect requests */
+                if (req->rq_timedout)
+                        return 0;
 
-        if (ptlrpc_client_early(req)) {
-                ptlrpc_at_recv_early_reply(req);
-                GOTO(out, rc = 0); /* keep waiting */
+                /* Suppress unavailable/again reconnect requests */
+                err = lustre_msg_get_status(req->rq_repmsg);
+                if (err == -ENODEV || err == -EAGAIN)
+                        return 0;
         }
 
-        EXIT;
- out:
-        spin_unlock(&req->rq_lock);
-        DEBUG_REQ(D_NET, req, "rc = %d for", rc);
-        return rc;
+        return 1;
 }
 
+/**
+ * Check request processing status.
+ * Returns the status.
+ */
 static int ptlrpc_check_status(struct ptlrpc_request *req)
 {
         int err;
         ENTRY;
 
         err = lustre_msg_get_status(req->rq_repmsg);
-        if (lustre_msg_get_type(req->rq_repmsg) == PTL_RPC_MSG_ERR) {
-                struct obd_import *imp = req->rq_import;
-                __u32 opc = lustre_msg_get_opc(req->rq_reqmsg);
-                LCONSOLE_ERROR_MSG(0x011,"an error occurred while communicating"
-                                " with %s. The %s operation failed with %d\n",
-                                libcfs_nid2str(imp->imp_connection->c_peer.nid),
-                                ll_opcode2str(opc), err);
-                RETURN(err < 0 ? err : -EINVAL);
-        }
+       if (lustre_msg_get_type(req->rq_repmsg) == PTL_RPC_MSG_ERR) {
+               struct obd_import *imp = req->rq_import;
+               __u32 opc = lustre_msg_get_opc(req->rq_reqmsg);
+               if (ptlrpc_console_allow(req))
+                       LCONSOLE_ERROR_MSG(0x011, "%s: Communicating with %s,"
+                                          " operation %s failed with %d.\n",
+                                          imp->imp_obd->obd_name,
+                                          libcfs_nid2str(
+                                          imp->imp_connection->c_peer.nid),
+                                          ll_opcode2str(opc), err);
+               RETURN(err < 0 ? err : -EINVAL);
+       }
 
         if (err < 0) {
                 DEBUG_REQ(D_INFO, req, "status is %d", err);
@@ -941,7 +1181,34 @@ static int ptlrpc_check_status(struct ptlrpc_request *req)
 }
 
 /**
+ * save pre-versions of objects into request for replay.
+ * Versions are obtained from server reply.
+ * used for VBR.
+ */
+static void ptlrpc_save_versions(struct ptlrpc_request *req)
+{
+        struct lustre_msg *repmsg = req->rq_repmsg;
+        struct lustre_msg *reqmsg = req->rq_reqmsg;
+        __u64 *versions = lustre_msg_get_versions(repmsg);
+        ENTRY;
+
+        if (lustre_msg_get_flags(req->rq_reqmsg) & MSG_REPLAY)
+                return;
+
+        LASSERT(versions);
+        lustre_msg_set_versions(reqmsg, versions);
+        CDEBUG(D_INFO, "Client save versions ["LPX64"/"LPX64"]\n",
+               versions[0], versions[1]);
+
+        EXIT;
+}
+
+/**
  * Callback function called when client receives RPC reply for \a req.
+ * Returns 0 on success or error code.
+ * The return alue would be assigned to req->rq_status by the caller
+ * as request processing status.
+ * This function also decides if the request needs to be saved for later replay.
  */
 static int after_reply(struct ptlrpc_request *req)
 {
@@ -952,36 +1219,90 @@ static int after_reply(struct ptlrpc_request *req)
         long timediff;
         ENTRY;
 
-        LASSERT(!req->rq_receiving_reply);
-        LASSERT(obd);
-        LASSERT(req->rq_nob_received <= req->rq_repbuf_len);
+        LASSERT(obd != NULL);
+        /* repbuf must be unlinked */
+        LASSERT(!req->rq_receiving_reply && !req->rq_must_unlink);
+
+        if (req->rq_reply_truncate) {
+                if (ptlrpc_no_resend(req)) {
+                        DEBUG_REQ(D_ERROR, req, "reply buffer overflow,"
+                                  " expected: %d, actual size: %d",
+                                  req->rq_nob_received, req->rq_repbuf_len);
+                        RETURN(-EOVERFLOW);
+                }
+
+                sptlrpc_cli_free_repbuf(req);
+                /* Pass the required reply buffer size (include
+                 * space for early reply).
+                 * NB: no need to roundup because alloc_repbuf
+                 * will roundup it */
+                req->rq_replen       = req->rq_nob_received;
+                req->rq_nob_received = 0;
+               spin_lock(&req->rq_lock);
+               req->rq_resend       = 1;
+               spin_unlock(&req->rq_lock);
+                RETURN(0);
+        }
 
         /*
          * NB Until this point, the whole of the incoming message,
          * including buflens, status etc is in the sender's byte order.
          */
-
         rc = sptlrpc_cli_unwrap_reply(req);
         if (rc) {
                 DEBUG_REQ(D_ERROR, req, "unwrap reply failed (%d):", rc);
                 RETURN(rc);
         }
 
-        /*
-         * Security layer unwrap might ask resend this request.
-         */
-        if (req->rq_resend)
-                RETURN(0);
-
-        rc = unpack_reply(req);
-        if (rc)
-                RETURN(rc);
-
-        do_gettimeofday(&work_start);
-        timediff = cfs_timeval_sub(&work_start, &req->rq_arrival_time, NULL);
-        if (obd->obd_svc_stats != NULL)
-                lprocfs_counter_add(obd->obd_svc_stats, PTLRPC_REQWAIT_CNTR,
-                                    timediff);
+       /*
+        * Security layer unwrap might ask resend this request.
+        */
+       if (req->rq_resend)
+               RETURN(0);
+
+       rc = unpack_reply(req);
+       if (rc)
+               RETURN(rc);
+
+       /* retry indefinitely on EINPROGRESS */
+       if (lustre_msg_get_status(req->rq_repmsg) == -EINPROGRESS &&
+           ptlrpc_no_resend(req) == 0 && !req->rq_no_retry_einprogress) {
+               time_t  now = cfs_time_current_sec();
+
+               DEBUG_REQ(D_RPCTRACE, req, "Resending request on EINPROGRESS");
+               req->rq_resend = 1;
+               req->rq_nr_resend++;
+
+               /* allocate new xid to avoid reply reconstruction */
+               if (!req->rq_bulk) {
+                       /* new xid is already allocated for bulk in
+                        * ptlrpc_check_set() */
+                       req->rq_xid = ptlrpc_next_xid();
+                       DEBUG_REQ(D_RPCTRACE, req, "Allocating new xid for "
+                                 "resend on EINPROGRESS");
+               }
+
+               /* Readjust the timeout for current conditions */
+               ptlrpc_at_set_req_timeout(req);
+               /* delay resend to give a chance to the server to get ready.
+                * The delay is increased by 1s on every resend and is capped to
+                * the current request timeout (i.e. obd_timeout if AT is off,
+                * or AT service time x 125% + 5s, see at_est2timeout) */
+               if (req->rq_nr_resend > req->rq_timeout)
+                       req->rq_sent = now + req->rq_timeout;
+               else
+                       req->rq_sent = now + req->rq_nr_resend;
+
+               RETURN(0);
+       }
+
+       do_gettimeofday(&work_start);
+       timediff = cfs_timeval_sub(&work_start, &req->rq_arrival_time, NULL);
+       if (obd->obd_svc_stats != NULL) {
+               lprocfs_counter_add(obd->obd_svc_stats, PTLRPC_REQWAIT_CNTR,
+                                   timediff);
+               ptlrpc_lprocfs_rpc_sent(req, timediff);
+       }
 
         if (lustre_msg_get_type(req->rq_repmsg) != PTL_RPC_MSG_REPLY &&
             lustre_msg_get_type(req->rq_repmsg) != PTL_RPC_MSG_ERR) {
@@ -990,7 +1311,8 @@ static int after_reply(struct ptlrpc_request *req)
                 RETURN(-EPROTO);
         }
 
-        OBD_FAIL_TIMEOUT(OBD_FAIL_PTLRPC_PAUSE_REP, obd_fail_val);
+        if (lustre_msg_get_opc(req->rq_reqmsg) != OBD_PING)
+                CFS_FAIL_TIMEOUT(OBD_FAIL_PTLRPC_PAUSE_REP, cfs_fail_val);
         ptlrpc_at_adj_service(req, lustre_msg_get_timeout(req->rq_repmsg));
         ptlrpc_at_adj_net_latency(req,
                                   lustre_msg_get_service_time(req->rq_repmsg));
@@ -1023,11 +1345,13 @@ static int after_reply(struct ptlrpc_request *req)
         /*
          * Store transno in reqmsg for replay.
          */
-        req->rq_transno = lustre_msg_get_transno(req->rq_repmsg);
-        lustre_msg_set_transno(req->rq_reqmsg, req->rq_transno);
+        if (!(lustre_msg_get_flags(req->rq_reqmsg) & MSG_REPLAY)) {
+                req->rq_transno = lustre_msg_get_transno(req->rq_repmsg);
+                lustre_msg_set_transno(req->rq_reqmsg, req->rq_transno);
+        }
 
-        if (req->rq_import->imp_replayable) {
-                spin_lock(&imp->imp_lock);
+        if (imp->imp_replayable) {
+               spin_lock(&imp->imp_lock);
                 /*
                  * No point in adding already-committed requests to the replay
                  * list, we will just remove them immediately. b=9829
@@ -1035,12 +1359,18 @@ static int after_reply(struct ptlrpc_request *req)
                 if (req->rq_transno != 0 &&
                     (req->rq_transno >
                      lustre_msg_get_last_committed(req->rq_repmsg) ||
-                     req->rq_replay))
+                     req->rq_replay)) {
+                        /** version recovery */
+                        ptlrpc_save_versions(req);
                         ptlrpc_retain_replayable_request(req, imp);
-                else if (req->rq_commit_cb != NULL) {
-                        spin_unlock(&imp->imp_lock);
-                        req->rq_commit_cb(req);
-                        spin_lock(&imp->imp_lock);
+               } else if (req->rq_commit_cb != NULL &&
+                          list_empty(&req->rq_replay_list)) {
+                       /* NB: don't call rq_commit_cb if it's already on
+                        * rq_replay_list, ptlrpc_free_committed() will call
+                        * it later, see LU-3618 for details */
+                       spin_unlock(&imp->imp_lock);
+                       req->rq_commit_cb(req);
+                       spin_lock(&imp->imp_lock);
                 }
 
                 /*
@@ -1050,59 +1380,82 @@ static int after_reply(struct ptlrpc_request *req)
                         imp->imp_peer_committed_transno =
                                 lustre_msg_get_last_committed(req->rq_repmsg);
                 }
-                ptlrpc_free_committed(imp);
-                spin_unlock(&imp->imp_lock);
-        }
 
-        RETURN(rc);
+               ptlrpc_free_committed(imp);
+
+               if (!cfs_list_empty(&imp->imp_replay_list)) {
+                       struct ptlrpc_request *last;
+
+                       last = cfs_list_entry(imp->imp_replay_list.prev,
+                                             struct ptlrpc_request,
+                                             rq_replay_list);
+                       /*
+                        * Requests with rq_replay stay on the list even if no
+                        * commit is expected.
+                        */
+                       if (last->rq_transno > imp->imp_peer_committed_transno)
+                               ptlrpc_pinger_commit_expected(imp);
+               }
+
+               spin_unlock(&imp->imp_lock);
+       }
+
+       RETURN(rc);
 }
 
+/**
+ * Helper function to send request \a req over the network for the first time
+ * Also adjusts request phase.
+ * Returns 0 on success or error code.
+ */
 static int ptlrpc_send_new_req(struct ptlrpc_request *req)
 {
-        struct obd_import     *imp;
+        struct obd_import     *imp = req->rq_import;
         int rc;
         ENTRY;
 
         LASSERT(req->rq_phase == RQ_PHASE_NEW);
-        if (req->rq_sent && (req->rq_sent > cfs_time_current_sec()))
+        if (req->rq_sent && (req->rq_sent > cfs_time_current_sec()) &&
+            (!req->rq_generation_set ||
+             req->rq_import_generation == imp->imp_generation))
                 RETURN (0);
 
         ptlrpc_rqphase_move(req, RQ_PHASE_RPC);
 
-        imp = req->rq_import;
-        spin_lock(&imp->imp_lock);
-
-        req->rq_import_generation = imp->imp_generation;
-
-        if (ptlrpc_import_delay_req(imp, req, &rc)) {
-                spin_lock(&req->rq_lock);
-                req->rq_waiting = 1;
-                spin_unlock(&req->rq_lock);
-
-                DEBUG_REQ(D_HA, req, "req from PID %d waiting for recovery: "
-                          "(%s != %s)", lustre_msg_get_status(req->rq_reqmsg),
-                          ptlrpc_import_state_name(req->rq_send_state),
-                          ptlrpc_import_state_name(imp->imp_state));
-                LASSERT(list_empty(&req->rq_list));
-                list_add_tail(&req->rq_list, &imp->imp_delayed_list);
-                atomic_inc(&req->rq_import->imp_inflight);
-                spin_unlock(&imp->imp_lock);
-                RETURN(0);
-        }
-
-        if (rc != 0) {
-                spin_unlock(&imp->imp_lock);
-                req->rq_status = rc;
-                ptlrpc_rqphase_move(req, RQ_PHASE_INTERPRET);
-                RETURN(rc);
-        }
-
-        LASSERT(list_empty(&req->rq_list));
-        list_add_tail(&req->rq_list, &imp->imp_sending_list);
-        atomic_inc(&req->rq_import->imp_inflight);
-        spin_unlock(&imp->imp_lock);
-
-        lustre_msg_set_status(req->rq_reqmsg, cfs_curproc_pid());
+       spin_lock(&imp->imp_lock);
+
+       if (!req->rq_generation_set)
+               req->rq_import_generation = imp->imp_generation;
+
+       if (ptlrpc_import_delay_req(imp, req, &rc)) {
+               spin_lock(&req->rq_lock);
+               req->rq_waiting = 1;
+               spin_unlock(&req->rq_lock);
+
+               DEBUG_REQ(D_HA, req, "req from PID %d waiting for recovery: "
+                         "(%s != %s)", lustre_msg_get_status(req->rq_reqmsg),
+                         ptlrpc_import_state_name(req->rq_send_state),
+                         ptlrpc_import_state_name(imp->imp_state));
+               LASSERT(cfs_list_empty(&req->rq_list));
+               cfs_list_add_tail(&req->rq_list, &imp->imp_delayed_list);
+               cfs_atomic_inc(&req->rq_import->imp_inflight);
+               spin_unlock(&imp->imp_lock);
+               RETURN(0);
+       }
+
+       if (rc != 0) {
+               spin_unlock(&imp->imp_lock);
+               req->rq_status = rc;
+               ptlrpc_rqphase_move(req, RQ_PHASE_INTERPRET);
+               RETURN(rc);
+       }
+
+       LASSERT(cfs_list_empty(&req->rq_list));
+       cfs_list_add_tail(&req->rq_list, &imp->imp_sending_list);
+       cfs_atomic_inc(&req->rq_import->imp_inflight);
+       spin_unlock(&imp->imp_lock);
+
+       lustre_msg_set_status(req->rq_reqmsg, current_pid());
 
         rc = sptlrpc_req_refresh_ctx(req, -1);
         if (rc) {
@@ -1110,41 +1463,76 @@ static int ptlrpc_send_new_req(struct ptlrpc_request *req)
                         req->rq_status = rc;
                         RETURN(1);
                 } else {
-                        req->rq_wait_ctx = 1;
+                       spin_lock(&req->rq_lock);
+                       req->rq_wait_ctx = 1;
+                       spin_unlock(&req->rq_lock);
                         RETURN(0);
                 }
         }
 
-        CDEBUG(D_RPCTRACE, "Sending RPC pname:cluuid:pid:xid:nid:opc"
-               " %s:%s:%d:"LPU64":%s:%d\n", cfs_curproc_comm(),
-               imp->imp_obd->obd_uuid.uuid,
-               lustre_msg_get_status(req->rq_reqmsg), req->rq_xid,
-               libcfs_nid2str(imp->imp_connection->c_peer.nid),
-               lustre_msg_get_opc(req->rq_reqmsg));
+       CDEBUG(D_RPCTRACE, "Sending RPC pname:cluuid:pid:xid:nid:opc"
+              " %s:%s:%d:"LPU64":%s:%d\n", current_comm(),
+              imp->imp_obd->obd_uuid.uuid,
+              lustre_msg_get_status(req->rq_reqmsg), req->rq_xid,
+              libcfs_nid2str(imp->imp_connection->c_peer.nid),
+              lustre_msg_get_opc(req->rq_reqmsg));
 
         rc = ptl_send_rpc(req, 0);
         if (rc) {
                 DEBUG_REQ(D_HA, req, "send failed (%d); expect timeout", rc);
-                req->rq_net_err = 1;
+               spin_lock(&req->rq_lock);
+               req->rq_net_err = 1;
+               spin_unlock(&req->rq_lock);
                 RETURN(rc);
         }
         RETURN(0);
 }
 
-/* this sends any unsent RPCs in @set and returns TRUE if all are sent */
+static inline int ptlrpc_set_producer(struct ptlrpc_request_set *set)
+{
+       int remaining, rc;
+       ENTRY;
+
+       LASSERT(set->set_producer != NULL);
+
+       remaining = cfs_atomic_read(&set->set_remaining);
+
+       /* populate the ->set_requests list with requests until we
+        * reach the maximum number of RPCs in flight for this set */
+       while (cfs_atomic_read(&set->set_remaining) < set->set_max_inflight) {
+               rc = set->set_producer(set, set->set_producer_arg);
+               if (rc == -ENOENT) {
+                       /* no more RPC to produce */
+                       set->set_producer     = NULL;
+                       set->set_producer_arg = NULL;
+                       RETURN(0);
+               }
+       }
+
+       RETURN((cfs_atomic_read(&set->set_remaining) - remaining));
+}
+
+/**
+ * this sends any unsent RPCs in \a set and returns 1 if all are sent
+ * and no more replies are expected.
+ * (it is possible to get less replies than requests sent e.g. due to timed out
+ * requests or requests that we had trouble to send out)
+ */
 int ptlrpc_check_set(const struct lu_env *env, struct ptlrpc_request_set *set)
 {
-        struct list_head *tmp;
+        cfs_list_t *tmp, *next;
         int force_timer_recalc = 0;
         ENTRY;
 
-        if (set->set_remaining == 0)
+        if (cfs_atomic_read(&set->set_remaining) == 0)
                 RETURN(1);
 
-        list_for_each(tmp, &set->set_requests) {
+        cfs_list_for_each_safe(tmp, next, &set->set_requests) {
                 struct ptlrpc_request *req =
-                        list_entry(tmp, struct ptlrpc_request, rq_set_chain);
+                        cfs_list_entry(tmp, struct ptlrpc_request,
+                                       rq_set_chain);
                 struct obd_import *imp = req->rq_import;
+                int unregistered = 0;
                 int rc = 0;
 
                 if (req->rq_phase == RQ_PHASE_NEW &&
@@ -1154,7 +1542,12 @@ int ptlrpc_check_set(const struct lu_env *env, struct ptlrpc_request_set *set)
 
                 /* delayed send - skip */
                 if (req->rq_phase == RQ_PHASE_NEW && req->rq_sent)
-                        continue;
+                       continue;
+
+               /* delayed resend - skip */
+               if (req->rq_phase == RQ_PHASE_RPC && req->rq_resend &&
+                   req->rq_sent > cfs_time_current_sec())
+                       continue;
 
                 if (!(req->rq_phase == RQ_PHASE_RPC ||
                       req->rq_phase == RQ_PHASE_BULK ||
@@ -1169,20 +1562,20 @@ int ptlrpc_check_set(const struct lu_env *env, struct ptlrpc_request_set *set)
                         LASSERT(req->rq_next_phase != req->rq_phase);
                         LASSERT(req->rq_next_phase != RQ_PHASE_UNDEFINED);
 
-                        /* 
+                        /*
                          * Skip processing until reply is unlinked. We
                          * can't return to pool before that and we can't
                          * call interpret before that. We need to make
                          * sure that all rdma transfers finished and will
-                         * not corrupt any data. 
+                         * not corrupt any data.
                          */
                         if (ptlrpc_client_recv_or_unlink(req) ||
                             ptlrpc_client_bulk_active(req))
                                 continue;
-                     
-                        /* 
+
+                        /*
                          * Turn fail_loc off to prevent it from looping
-                         * forever. 
+                         * forever.
                          */
                         if (OBD_FAIL_CHECK(OBD_FAIL_PTLRPC_LONG_REPL_UNLINK)) {
                                 OBD_FAIL_CHECK_ORSET(OBD_FAIL_PTLRPC_LONG_REPL_UNLINK,
@@ -1193,9 +1586,9 @@ int ptlrpc_check_set(const struct lu_env *env, struct ptlrpc_request_set *set)
                                                      OBD_FAIL_ONCE);
                         }
 
-                        /* 
-                         * Move to next phase if reply was successfully 
-                         * unlinked. 
+                        /*
+                         * Move to next phase if reply was successfully
+                         * unlinked.
                          */
                         ptlrpc_rqphase_move(req, req->rq_next_phase);
                 }
@@ -1206,33 +1599,48 @@ int ptlrpc_check_set(const struct lu_env *env, struct ptlrpc_request_set *set)
                 if (req->rq_phase == RQ_PHASE_INTERPRET)
                         GOTO(interpret, req->rq_status);
 
-                /* 
-                 * Note that this also will start async reply unlink. 
+                /*
+                 * Note that this also will start async reply unlink.
                  */
                 if (req->rq_net_err && !req->rq_timedout) {
                         ptlrpc_expire_one_request(req, 1);
 
-                        /* 
-                         * Check if we still need to wait for unlink. 
+                        /*
+                         * Check if we still need to wait for unlink.
                          */
                         if (ptlrpc_client_recv_or_unlink(req) ||
                             ptlrpc_client_bulk_active(req))
                                 continue;
+                        /* If there is no need to resend, fail it now. */
+                        if (req->rq_no_resend) {
+                                if (req->rq_status == 0)
+                                        req->rq_status = -EIO;
+                                ptlrpc_rqphase_move(req, RQ_PHASE_INTERPRET);
+                                GOTO(interpret, req->rq_status);
+                        } else {
+                                continue;
+                        }
                 }
 
                 if (req->rq_err) {
-                        req->rq_replied = 0;
+                       spin_lock(&req->rq_lock);
+                       req->rq_replied = 0;
+                       spin_unlock(&req->rq_lock);
                         if (req->rq_status == 0)
                                 req->rq_status = -EIO;
                         ptlrpc_rqphase_move(req, RQ_PHASE_INTERPRET);
                         GOTO(interpret, req->rq_status);
                 }
 
-                /* ptlrpc_queue_wait->l_wait_event guarantees that rq_intr
-                 * will only be set after rq_timedout, but the synchronous IO
-                 * waiting path sets rq_intr irrespective of whether ptlrpcd
-                 * has seen a timeout.  our policy is to only interpret
-                 * interrupted rpcs after they have timed out */
+                /* ptlrpc_set_wait->l_wait_event sets lwi_allow_intr
+                 * so it sets rq_intr regardless of individual rpc
+                 * timeouts. The synchronous IO waiting path sets 
+                 * rq_intr irrespective of whether ptlrpcd
+                 * has seen a timeout.  Our policy is to only interpret
+                 * interrupted rpcs after they have timed out, so we
+                 * need to enforce that here.
+                 */
+
                 if (req->rq_intr && (req->rq_timedout || req->rq_waiting ||
                                      req->rq_wait_ctx)) {
                         req->rq_status = -EINTR;
@@ -1248,42 +1656,50 @@ int ptlrpc_check_set(const struct lu_env *env, struct ptlrpc_request_set *set)
                                 if (!ptlrpc_unregister_reply(req, 1))
                                         continue;
 
-                                spin_lock(&imp->imp_lock);
-
-                                if (ptlrpc_import_delay_req(imp, req, &status)){
-                                        spin_unlock(&imp->imp_lock);
+                               spin_lock(&imp->imp_lock);
+                               if (ptlrpc_import_delay_req(imp, req, &status)){
+                                       /* put on delay list - only if we wait
+                                        * recovery finished - before send */
+                                       cfs_list_del_init(&req->rq_list);
+                                       cfs_list_add_tail(&req->rq_list,
+                                                         &imp->
+                                                         imp_delayed_list);
+                                       spin_unlock(&imp->imp_lock);
                                         continue;
                                 }
 
                                 if (status != 0)  {
                                         req->rq_status = status;
-                                        ptlrpc_rqphase_move(req, 
+                                        ptlrpc_rqphase_move(req,
                                                 RQ_PHASE_INTERPRET);
-                                        spin_unlock(&imp->imp_lock);
-                                        GOTO(interpret, req->rq_status);
-                                }
-                                if (req->rq_no_resend && !req->rq_wait_ctx) {
-                                        req->rq_status = -ENOTCONN;
-                                        ptlrpc_rqphase_move(req, 
-                                                RQ_PHASE_INTERPRET);
-                                        spin_unlock(&imp->imp_lock);
-                                        GOTO(interpret, req->rq_status);
-                                }
-
-                                list_del_init(&req->rq_list);
-                                list_add_tail(&req->rq_list,
-                                              &imp->imp_sending_list);
-
-                                spin_unlock(&imp->imp_lock);
-
-                                req->rq_waiting = 0;
-
-                                if (req->rq_timedout||req->rq_resend) {
-                                        /* This is re-sending anyways, 
-                                         * let's mark req as resend. */
-                                        req->rq_resend = 1;
-                                        lustre_msg_add_flags(req->rq_reqmsg,
-                                                             MSG_RESENT);
+                                       spin_unlock(&imp->imp_lock);
+                                       GOTO(interpret, req->rq_status);
+                               }
+                               if (ptlrpc_no_resend(req) &&
+                                   !req->rq_wait_ctx) {
+                                       req->rq_status = -ENOTCONN;
+                                       ptlrpc_rqphase_move(req,
+                                                           RQ_PHASE_INTERPRET);
+                                       spin_unlock(&imp->imp_lock);
+                                       GOTO(interpret, req->rq_status);
+                               }
+
+                               cfs_list_del_init(&req->rq_list);
+                               cfs_list_add_tail(&req->rq_list,
+                                                 &imp->imp_sending_list);
+
+                               spin_unlock(&imp->imp_lock);
+
+                               spin_lock(&req->rq_lock);
+                               req->rq_waiting = 0;
+                               spin_unlock(&req->rq_lock);
+
+                               if (req->rq_timedout || req->rq_resend) {
+                                       /* This is re-sending anyways,
+                                        * let's mark req as resend. */
+                                       spin_lock(&req->rq_lock);
+                                       req->rq_resend = 1;
+                                       spin_unlock(&req->rq_lock);
                                         if (req->rq_bulk) {
                                                 __u64 old_xid;
 
@@ -1307,88 +1723,94 @@ int ptlrpc_check_set(const struct lu_env *env, struct ptlrpc_request_set *set)
                                 if (status) {
                                         if (req->rq_err) {
                                                 req->rq_status = status;
-                                                req->rq_wait_ctx = 0;
-                                                force_timer_recalc = 1;
-                                        } else {
-                                                req->rq_wait_ctx = 1;
-                                        }
+                                               spin_lock(&req->rq_lock);
+                                               req->rq_wait_ctx = 0;
+                                               spin_unlock(&req->rq_lock);
+                                               force_timer_recalc = 1;
+                                       } else {
+                                               spin_lock(&req->rq_lock);
+                                               req->rq_wait_ctx = 1;
+                                               spin_unlock(&req->rq_lock);
+                                       }
+
+                                       continue;
+                               } else {
+                                       spin_lock(&req->rq_lock);
+                                       req->rq_wait_ctx = 0;
+                                       spin_unlock(&req->rq_lock);
+                               }
+
+                               rc = ptl_send_rpc(req, 0);
+                               if (rc) {
+                                       DEBUG_REQ(D_HA, req,
+                                                 "send failed: rc = %d", rc);
+                                       force_timer_recalc = 1;
+                                       spin_lock(&req->rq_lock);
+                                       req->rq_net_err = 1;
+                                       spin_unlock(&req->rq_lock);
+                                       continue;
+                               }
+                               /* need to reset the timeout */
+                               force_timer_recalc = 1;
+                       }
+
+                       spin_lock(&req->rq_lock);
+
+                       if (ptlrpc_client_early(req)) {
+                               ptlrpc_at_recv_early_reply(req);
+                               spin_unlock(&req->rq_lock);
+                               continue;
+                       }
+
+                       /* Still waiting for a reply? */
+                       if (ptlrpc_client_recv(req)) {
+                               spin_unlock(&req->rq_lock);
+                               continue;
+                       }
+
+                       /* Did we actually receive a reply? */
+                       if (!ptlrpc_client_replied(req)) {
+                               spin_unlock(&req->rq_lock);
+                               continue;
+                       }
+
+                       spin_unlock(&req->rq_lock);
+
+                        /* unlink from net because we are going to
+                         * swab in-place of reply buffer */
+                        unregistered = ptlrpc_unregister_reply(req, 1);
+                        if (!unregistered)
+                                continue;
 
-                                        continue;
-                                } else {
-                                        req->rq_wait_ctx = 0;
-                                }
+                        req->rq_status = after_reply(req);
+                        if (req->rq_resend)
+                                continue;
 
-                                rc = ptl_send_rpc(req, 0);
-                                if (rc) {
-                                        DEBUG_REQ(D_HA, req, "send failed (%d)",
-                                                  rc);
-                                        force_timer_recalc = 1;
-                                        req->rq_net_err = 1;
-                                }
-                                /* need to reset the timeout */
-                                force_timer_recalc = 1;
+                        /* If there is no bulk associated with this request,
+                         * then we're done and should let the interpreter
+                         * process the reply. Similarly if the RPC returned
+                         * an error, and therefore the bulk will never arrive.
+                         */
+                        if (req->rq_bulk == NULL || req->rq_status < 0) {
+                                ptlrpc_rqphase_move(req, RQ_PHASE_INTERPRET);
+                                GOTO(interpret, req->rq_status);
                         }
 
-                        spin_lock(&req->rq_lock);
-
-                        if (ptlrpc_client_early(req)) {
-                                ptlrpc_at_recv_early_reply(req);
-                                spin_unlock(&req->rq_lock);
-                                continue;
-                        }
-
-                        /* Still waiting for a reply? */
-                        if (ptlrpc_client_recv(req)) {
-                                spin_unlock(&req->rq_lock);
-                                continue;
-                        }
-
-                        /* Did we actually receive a reply? */
-                        if (!ptlrpc_client_replied(req)) {
-                                spin_unlock(&req->rq_lock);
-                                continue;
-                        }
-
-                        spin_unlock(&req->rq_lock);
-
-                        req->rq_status = after_reply(req);
-                        if (req->rq_resend) {
-                                /* Add this req to the delayed list so
-                                   it can be errored if the import is
-                                   evicted after recovery. */
-                                spin_lock(&imp->imp_lock);
-                                list_del_init(&req->rq_list);
-                                list_add_tail(&req->rq_list,
-                                              &imp->imp_delayed_list);
-                                spin_unlock(&imp->imp_lock);
-                                continue;
-                        }
-
-                        /* If there is no bulk associated with this request,
-                         * then we're done and should let the interpreter
-                         * process the reply. Similarly if the RPC returned
-                         * an error, and therefore the bulk will never arrive.
-                         */
-                        if (req->rq_bulk == NULL || req->rq_status != 0) {
-                                ptlrpc_rqphase_move(req, RQ_PHASE_INTERPRET);
-                                GOTO(interpret, req->rq_status);
-                        }
-
-                        ptlrpc_rqphase_move(req, RQ_PHASE_BULK);
-                }
+                        ptlrpc_rqphase_move(req, RQ_PHASE_BULK);
+                }
 
                 LASSERT(req->rq_phase == RQ_PHASE_BULK);
                 if (ptlrpc_client_bulk_active(req))
                         continue;
 
-                if (!req->rq_bulk->bd_success) {
-                        /* The RPC reply arrived OK, but the bulk screwed
-                         * up!  Dead wierd since the server told us the RPC
-                         * was good after getting the REPLY for her GET or
-                         * the ACK for her PUT. */
-                        DEBUG_REQ(D_ERROR, req, "bulk transfer failed");
-                        LBUG();
-                }
+               if (req->rq_bulk->bd_failure) {
+                       /* The RPC reply arrived OK, but the bulk screwed
+                        * up!  Dead weird since the server told us the RPC
+                        * was good after getting the REPLY for her GET or
+                        * the ACK for her PUT. */
+                       DEBUG_REQ(D_ERROR, req, "bulk transfer failed");
+                       req->rq_status = -EIO;
+               }
 
                 ptlrpc_rqphase_move(req, RQ_PHASE_INTERPRET);
 
@@ -1397,8 +1819,11 @@ int ptlrpc_check_set(const struct lu_env *env, struct ptlrpc_request_set *set)
 
                 /* This moves to "unregistering" phase we need to wait for
                  * reply unlink. */
-                if (!ptlrpc_unregister_reply(req, 1))
+                if (!unregistered && !ptlrpc_unregister_reply(req, 1)) {
+                        /* start async bulk unlink too */
+                        ptlrpc_unregister_bulk(req, 1);
                         continue;
+                }
 
                 if (!ptlrpc_unregister_bulk(req, 1))
                         continue;
@@ -1407,71 +1832,88 @@ int ptlrpc_check_set(const struct lu_env *env, struct ptlrpc_request_set *set)
                  * finished. */
                 LASSERT(!req->rq_receiving_reply);
 
-                if (req->rq_interpret_reply != NULL) {
-                        ptlrpc_interpterer_t interpreter =
-                                req->rq_interpret_reply;
-                        req->rq_status = interpreter(env, req,
-                                                     &req->rq_async_args,
-                                                     req->rq_status);
-                }
-                ptlrpc_rqphase_move(req, RQ_PHASE_COMPLETE);
-
-                CDEBUG(D_RPCTRACE, "Completed RPC pname:cluuid:pid:xid:nid:"
-                       "opc %s:%s:%d:"LPU64":%s:%d\n", cfs_curproc_comm(),
-                       imp->imp_obd->obd_uuid.uuid,
-                       lustre_msg_get_status(req->rq_reqmsg), req->rq_xid,
-                       libcfs_nid2str(imp->imp_connection->c_peer.nid),
-                       lustre_msg_get_opc(req->rq_reqmsg));
-
-                spin_lock(&imp->imp_lock);
-                /* Request already may be not on sending or delaying list. This
-                 * may happen in the case of marking it errorneous for the case
-                 * ptlrpc_import_delay_req(req, status) find it impossible to 
-                 * allow sending this rpc and returns *status != 0. */
-                if (!list_empty(&req->rq_list)) {
-                        list_del_init(&req->rq_list);
-                        atomic_dec(&imp->imp_inflight);
-                }
-                spin_unlock(&imp->imp_lock);
-
-                set->set_remaining--;
-                cfs_waitq_signal(&imp->imp_recovery_waitq);
+                ptlrpc_req_interpret(env, req, req->rq_status);
+
+               if (ptlrpcd_check_work(req)) {
+                       atomic_dec(&set->set_remaining);
+                       continue;
+               }
+               ptlrpc_rqphase_move(req, RQ_PHASE_COMPLETE);
+
+               CDEBUG(req->rq_reqmsg != NULL ? D_RPCTRACE : 0,
+                       "Completed RPC pname:cluuid:pid:xid:nid:"
+                       "opc %s:%s:%d:"LPU64":%s:%d\n",
+                       current_comm(), imp->imp_obd->obd_uuid.uuid,
+                       lustre_msg_get_status(req->rq_reqmsg), req->rq_xid,
+                       libcfs_nid2str(imp->imp_connection->c_peer.nid),
+                       lustre_msg_get_opc(req->rq_reqmsg));
+
+               spin_lock(&imp->imp_lock);
+               /* Request already may be not on sending or delaying list. This
+                * may happen in the case of marking it erroneous for the case
+                * ptlrpc_import_delay_req(req, status) find it impossible to
+                * allow sending this rpc and returns *status != 0. */
+               if (!cfs_list_empty(&req->rq_list)) {
+                       cfs_list_del_init(&req->rq_list);
+                       cfs_atomic_dec(&imp->imp_inflight);
+               }
+               spin_unlock(&imp->imp_lock);
+
+               cfs_atomic_dec(&set->set_remaining);
+               wake_up_all(&imp->imp_recovery_waitq);
+
+               if (set->set_producer) {
+                       /* produce a new request if possible */
+                       if (ptlrpc_set_producer(set) > 0)
+                               force_timer_recalc = 1;
+
+                       /* free the request that has just been completed
+                        * in order not to pollute set->set_requests */
+                       cfs_list_del_init(&req->rq_set_chain);
+                       spin_lock(&req->rq_lock);
+                       req->rq_set = NULL;
+                       req->rq_invalid_rqset = 0;
+                       spin_unlock(&req->rq_lock);
+
+                       /* record rq_status to compute the final status later */
+                       if (req->rq_status != 0)
+                               set->set_rc = req->rq_status;
+                       ptlrpc_req_finished(req);
+               }
         }
 
         /* If we hit an error, we want to recover promptly. */
-        RETURN(set->set_remaining == 0 || force_timer_recalc);
+        RETURN(cfs_atomic_read(&set->set_remaining) == 0 || force_timer_recalc);
 }
+EXPORT_SYMBOL(ptlrpc_check_set);
 
-/* Return 1 if we should give up, else 0 */
+/**
+ * Time out request \a req. is \a async_unlink is set, that means do not wait
+ * until LNet actually confirms network buffer unlinking.
+ * Return 1 if we should give up further retrying attempts or 0 otherwise.
+ */
 int ptlrpc_expire_one_request(struct ptlrpc_request *req, int async_unlink)
 {
-        struct obd_import *imp = req->rq_import;
-        int rc = 0;
-        ENTRY;
+       struct obd_import *imp = req->rq_import;
+       int rc = 0;
+       ENTRY;
 
-        DEBUG_REQ(D_ERROR|D_NETERROR, req,
-                  "%s (sent at "CFS_TIME_T", "CFS_DURATION_T"s ago)",
-                  req->rq_net_err ? "network error" : "timeout",
-                  req->rq_sent, cfs_time_sub(cfs_time_current_sec(),
-                  req->rq_sent));
-
-        if (imp) {
-                LCONSOLE_WARN("Request x"LPU64" sent from %s to NID %s "
-                              CFS_DURATION_T"s ago has timed out "
-                              "(limit "CFS_DURATION_T"s).\n", req->rq_xid,
-                              req->rq_import->imp_obd->obd_name,
-                              libcfs_nid2str(imp->imp_connection->c_peer.nid),
-                              cfs_time_sub(cfs_time_current_sec(), req->rq_sent),
-                              cfs_time_sub(req->rq_deadline, req->rq_sent));
-        }
+       spin_lock(&req->rq_lock);
+       req->rq_timedout = 1;
+       spin_unlock(&req->rq_lock);
+
+       DEBUG_REQ(D_WARNING, req, "Request sent has %s: [sent "CFS_DURATION_T
+                 "/real "CFS_DURATION_T"]",
+                  req->rq_net_err ? "failed due to network error" :
+                     ((req->rq_real_sent == 0 ||
+                       cfs_time_before(req->rq_real_sent, req->rq_sent) ||
+                       cfs_time_aftereq(req->rq_real_sent, req->rq_deadline)) ?
+                      "timed out for sent delay" : "timed out for slow reply"),
+                  req->rq_sent, req->rq_real_sent);
 
         if (imp != NULL && obd_debug_peer_on_timeout)
                 LNetCtl(IOC_LIBCFS_DEBUG_PEER, &imp->imp_connection->c_peer);
 
-        spin_lock(&req->rq_lock);
-        req->rq_timedout = 1;
-        spin_unlock(&req->rq_lock);
-
         ptlrpc_unregister_reply(req, async_unlink);
         ptlrpc_unregister_bulk(req, async_unlink);
 
@@ -1483,6 +1925,8 @@ int ptlrpc_expire_one_request(struct ptlrpc_request *req, int async_unlink)
                 RETURN(1);
         }
 
+        cfs_atomic_inc(&imp->imp_timeouts);
+
         /* The DLM server doesn't want recovery run on its imports. */
         if (imp->imp_dlm_fake)
                 RETURN(1);
@@ -1495,16 +1939,16 @@ int ptlrpc_expire_one_request(struct ptlrpc_request *req, int async_unlink)
                 DEBUG_REQ(D_RPCTRACE, req, "err -110, sent_state=%s (now=%s)",
                           ptlrpc_import_state_name(req->rq_send_state),
                           ptlrpc_import_state_name(imp->imp_state));
-                spin_lock(&req->rq_lock);
-                req->rq_status = -ETIMEDOUT;
-                req->rq_err = 1;
-                spin_unlock(&req->rq_lock);
-                RETURN(1);
+               spin_lock(&req->rq_lock);
+               req->rq_status = -ETIMEDOUT;
+               req->rq_err = 1;
+               spin_unlock(&req->rq_lock);
+               RETURN(1);
         }
 
         /* if a request can't be resent we can't wait for an answer after
            the timeout */
-        if (req->rq_no_resend) {
+        if (ptlrpc_no_resend(req)) {
                 DEBUG_REQ(D_RPCTRACE, req, "TIMEOUT-NORESEND:");
                 rc = 1;
         }
@@ -1514,21 +1958,27 @@ int ptlrpc_expire_one_request(struct ptlrpc_request *req, int async_unlink)
         RETURN(rc);
 }
 
+/**
+ * Time out all uncompleted requests in request set pointed by \a data
+ * Callback used when waiting on sets with l_wait_event.
+ * Always returns 1.
+ */
 int ptlrpc_expired_set(void *data)
 {
         struct ptlrpc_request_set *set = data;
-        struct list_head          *tmp;
+        cfs_list_t                *tmp;
         time_t                     now = cfs_time_current_sec();
         ENTRY;
 
         LASSERT(set != NULL);
 
-        /* 
-         * A timeout expired. See which reqs it applies to... 
+        /*
+         * A timeout expired. See which reqs it applies to...
          */
-        list_for_each (tmp, &set->set_requests) {
+        cfs_list_for_each (tmp, &set->set_requests) {
                 struct ptlrpc_request *req =
-                        list_entry(tmp, struct ptlrpc_request, rq_set_chain);
+                        cfs_list_entry(tmp, struct ptlrpc_request,
+                                       rq_set_chain);
 
                 /* don't expire request waiting for context */
                 if (req->rq_wait_ctx)
@@ -1539,7 +1989,7 @@ int ptlrpc_expired_set(void *data)
                        !req->rq_waiting && !req->rq_resend) ||
                       (req->rq_phase == RQ_PHASE_BULK)))
                         continue;
-  
+
                 if (req->rq_timedout ||     /* already dealt with */
                     req->rq_deadline > now) /* not expired */
                         continue;
@@ -1549,80 +1999,91 @@ int ptlrpc_expired_set(void *data)
                 ptlrpc_expire_one_request(req, 1);
         }
 
-        /* 
-         * When waiting for a whole set, we always to break out of the
+        /*
+         * When waiting for a whole set, we always break out of the
          * sleep so we can recalculate the timeout, or enable interrupts
          * if everyone's timed out.
          */
         RETURN(1);
 }
+EXPORT_SYMBOL(ptlrpc_expired_set);
 
+/**
+ * Sets rq_intr flag in \a req under spinlock.
+ */
 void ptlrpc_mark_interrupted(struct ptlrpc_request *req)
 {
-        spin_lock(&req->rq_lock);
-        req->rq_intr = 1;
-        spin_unlock(&req->rq_lock);
+       spin_lock(&req->rq_lock);
+       req->rq_intr = 1;
+       spin_unlock(&req->rq_lock);
 }
+EXPORT_SYMBOL(ptlrpc_mark_interrupted);
 
+/**
+ * Interrupts (sets interrupted flag) all uncompleted requests in
+ * a set \a data. Callback for l_wait_event for interruptible waits.
+ */
 void ptlrpc_interrupted_set(void *data)
 {
         struct ptlrpc_request_set *set = data;
-        struct list_head *tmp;
+        cfs_list_t *tmp;
 
         LASSERT(set != NULL);
-        CERROR("INTERRUPTED SET %p\n", set);
+        CDEBUG(D_RPCTRACE, "INTERRUPTED SET %p\n", set);
 
-        list_for_each(tmp, &set->set_requests) {
+        cfs_list_for_each(tmp, &set->set_requests) {
                 struct ptlrpc_request *req =
-                        list_entry(tmp, struct ptlrpc_request, rq_set_chain);
+                        cfs_list_entry(tmp, struct ptlrpc_request,
+                                       rq_set_chain);
 
-                if (req->rq_phase != RQ_PHASE_RPC && 
+                if (req->rq_phase != RQ_PHASE_RPC &&
                     req->rq_phase != RQ_PHASE_UNREGISTERING)
                         continue;
 
                 ptlrpc_mark_interrupted(req);
         }
 }
+EXPORT_SYMBOL(ptlrpc_interrupted_set);
 
-/** 
- * Get the smallest timeout in the set; this does NOT set a timeout. 
+/**
+ * Get the smallest timeout in the set; this does NOT set a timeout.
  */
 int ptlrpc_set_next_timeout(struct ptlrpc_request_set *set)
 {
-        struct list_head      *tmp;
+        cfs_list_t            *tmp;
         time_t                 now = cfs_time_current_sec();
         int                    timeout = 0;
         struct ptlrpc_request *req;
         int                    deadline;
         ENTRY;
 
-        SIGNAL_MASK_ASSERT(); /* XXX BUG 1511 */
+        cfs_list_for_each(tmp, &set->set_requests) {
+                req = cfs_list_entry(tmp, struct ptlrpc_request, rq_set_chain);
 
-        list_for_each(tmp, &set->set_requests) {
-                req = list_entry(tmp, struct ptlrpc_request, rq_set_chain);
-
-                /* 
-                 * Request in-flight? 
+                /*
+                 * Request in-flight?
                  */
                 if (!(((req->rq_phase == RQ_PHASE_RPC) && !req->rq_waiting) ||
                       (req->rq_phase == RQ_PHASE_BULK) ||
                       (req->rq_phase == RQ_PHASE_NEW)))
                         continue;
 
-                /* 
-                 * Already timed out. 
+                /*
+                 * Already timed out.
                  */
                 if (req->rq_timedout)
                         continue;
 
-                /* 
-                 * Waiting for ctx. 
+                /*
+                 * Waiting for ctx.
                  */
                 if (req->rq_wait_ctx)
                         continue;
 
                 if (req->rq_phase == RQ_PHASE_NEW)
                         deadline = req->rq_sent;
+               else if (req->rq_phase == RQ_PHASE_RPC && req->rq_resend)
+                       deadline = req->rq_sent;
                 else
                         deadline = req->rq_sent + req->rq_timeout;
 
@@ -1633,24 +2094,35 @@ int ptlrpc_set_next_timeout(struct ptlrpc_request_set *set)
         }
         RETURN(timeout);
 }
+EXPORT_SYMBOL(ptlrpc_set_next_timeout);
 
+/**
+ * Send all unset request from the set and then wait untill all
+ * requests in the set complete (either get a reply, timeout, get an
+ * error or otherwise be interrupted).
+ * Returns 0 on success or error code otherwise.
+ */
 int ptlrpc_set_wait(struct ptlrpc_request_set *set)
 {
-        struct list_head      *tmp;
+        cfs_list_t            *tmp;
         struct ptlrpc_request *req;
         struct l_wait_info     lwi;
         int                    rc, timeout;
         ENTRY;
 
-        if (list_empty(&set->set_requests))
+       if (set->set_producer)
+               (void)ptlrpc_set_producer(set);
+       else
+               cfs_list_for_each(tmp, &set->set_requests) {
+                       req = cfs_list_entry(tmp, struct ptlrpc_request,
+                                            rq_set_chain);
+                       if (req->rq_phase == RQ_PHASE_NEW)
+                               (void)ptlrpc_send_new_req(req);
+               }
+
+        if (cfs_list_empty(&set->set_requests))
                 RETURN(0);
 
-        list_for_each(tmp, &set->set_requests) {
-                req = list_entry(tmp, struct ptlrpc_request, rq_set_chain);
-                if (req->rq_phase == RQ_PHASE_NEW)
-                        (void)ptlrpc_send_new_req(req);
-        }
-
         do {
                 timeout = ptlrpc_set_next_timeout(set);
 
@@ -1658,28 +2130,70 @@ int ptlrpc_set_wait(struct ptlrpc_request_set *set)
                  * req times out */
                 CDEBUG(D_RPCTRACE, "set %p going to sleep for %d seconds\n",
                        set, timeout);
-                lwi = LWI_TIMEOUT_INTR(cfs_time_seconds(timeout ? timeout : 1),
-                                       ptlrpc_expired_set,
-                                       ptlrpc_interrupted_set, set);
-                rc = l_wait_event(set->set_waitq,
-                                  ptlrpc_check_set(NULL, set), &lwi);
+
+                if (timeout == 0 && !cfs_signal_pending())
+                        /*
+                         * No requests are in-flight (ether timed out
+                         * or delayed), so we can allow interrupts.
+                         * We still want to block for a limited time,
+                         * so we allow interrupts during the timeout.
+                         */
+                        lwi = LWI_TIMEOUT_INTR_ALL(cfs_time_seconds(1), 
+                                                   ptlrpc_expired_set,
+                                                   ptlrpc_interrupted_set, set);
+                else
+                        /*
+                         * At least one request is in flight, so no
+                         * interrupts are allowed. Wait until all
+                         * complete, or an in-flight req times out. 
+                         */
+                        lwi = LWI_TIMEOUT(cfs_time_seconds(timeout? timeout : 1),
+                                          ptlrpc_expired_set, set);
+
+                rc = l_wait_event(set->set_waitq, ptlrpc_check_set(NULL, set), &lwi);
+
+                /* LU-769 - if we ignored the signal because it was already
+                 * pending when we started, we need to handle it now or we risk
+                 * it being ignored forever */
+               if (rc == -ETIMEDOUT && !lwi.lwi_allow_intr &&
+                   cfs_signal_pending()) {
+                       sigset_t blocked_sigs =
+                                          cfs_block_sigsinv(LUSTRE_FATAL_SIGS);
+
+                       /* In fact we only interrupt for the "fatal" signals
+                        * like SIGINT or SIGKILL. We still ignore less
+                        * important signals since ptlrpc set is not easily
+                        * reentrant from userspace again */
+                       if (cfs_signal_pending())
+                               ptlrpc_interrupted_set(set);
+                       cfs_restore_sigs(blocked_sigs);
+               }
 
                 LASSERT(rc == 0 || rc == -EINTR || rc == -ETIMEDOUT);
 
                 /* -EINTR => all requests have been flagged rq_intr so next
                  * check completes.
-                 * -ETIMEOUTD => someone timed out.  When all reqs have
+                 * -ETIMEDOUT => someone timed out.  When all reqs have
                  * timed out, signals are enabled allowing completion with
                  * EINTR.
                  * I don't really care if we go once more round the loop in
                  * the error cases -eeb. */
-        } while (rc != 0 || set->set_remaining != 0);
+                if (rc == 0 && cfs_atomic_read(&set->set_remaining) == 0) {
+                        cfs_list_for_each(tmp, &set->set_requests) {
+                                req = cfs_list_entry(tmp, struct ptlrpc_request,
+                                                     rq_set_chain);
+                               spin_lock(&req->rq_lock);
+                               req->rq_invalid_rqset = 1;
+                               spin_unlock(&req->rq_lock);
+                        }
+                }
+        } while (rc != 0 || cfs_atomic_read(&set->set_remaining) != 0);
 
-        LASSERT(set->set_remaining == 0);
+        LASSERT(cfs_atomic_read(&set->set_remaining) == 0);
 
-        rc = 0;
-        list_for_each(tmp, &set->set_requests) {
-                req = list_entry(tmp, struct ptlrpc_request, rq_set_chain);
+        rc = set->set_rc; /* rq_status of already freed requests if any */
+        cfs_list_for_each(tmp, &set->set_requests) {
+                req = cfs_list_entry(tmp, struct ptlrpc_request, rq_set_chain);
 
                 LASSERT(req->rq_phase == RQ_PHASE_COMPLETE);
                 if (req->rq_status != 0)
@@ -1694,9 +2208,9 @@ int ptlrpc_set_wait(struct ptlrpc_request_set *set)
                 struct ptlrpc_set_cbdata *cbdata, *n;
                 int err;
 
-                list_for_each_entry_safe(cbdata, n,
+                cfs_list_for_each_entry_safe(cbdata, n,
                                          &set->set_cblist, psc_item) {
-                        list_del_init(&cbdata->psc_item);
+                        cfs_list_del_init(&cbdata->psc_item);
                         err = cbdata->psc_interpret(set, cbdata->psc_data, rc);
                         if (err && !rc)
                                 rc = err;
@@ -1706,7 +2220,16 @@ int ptlrpc_set_wait(struct ptlrpc_request_set *set)
 
         RETURN(rc);
 }
+EXPORT_SYMBOL(ptlrpc_set_wait);
 
+/**
+ * Helper fuction for request freeing.
+ * Called when request count reached zero and request needs to be freed.
+ * Removes request from all sorts of sending/replay lists it might be on,
+ * frees network buffers if any are present.
+ * If \a locked is set, that means caller is already holding import imp_lock
+ * and so we no longer need to reobtain it (for certain lists manipulations)
+ */
 static void __ptlrpc_free_req(struct ptlrpc_request *request, int locked)
 {
         ENTRY;
@@ -1717,27 +2240,25 @@ static void __ptlrpc_free_req(struct ptlrpc_request *request, int locked)
 
         LASSERTF(!request->rq_receiving_reply, "req %p\n", request);
         LASSERTF(request->rq_rqbd == NULL, "req %p\n",request);/* client-side */
-        LASSERTF(list_empty(&request->rq_list), "req %p\n", request);
-        LASSERTF(list_empty(&request->rq_set_chain), "req %p\n", request);
-        LASSERTF(list_empty(&request->rq_exp_list), "req %p\n", request);
+        LASSERTF(cfs_list_empty(&request->rq_list), "req %p\n", request);
+        LASSERTF(cfs_list_empty(&request->rq_set_chain), "req %p\n", request);
+        LASSERTF(cfs_list_empty(&request->rq_exp_list), "req %p\n", request);
         LASSERTF(!request->rq_replay, "req %p\n", request);
-        LASSERT(request->rq_cli_ctx);
 
         req_capsule_fini(&request->rq_pill);
 
         /* We must take it off the imp_replay_list first.  Otherwise, we'll set
          * request->rq_reqmsg to NULL while osc_close is dereferencing it. */
         if (request->rq_import != NULL) {
-                if (!locked)
-                        spin_lock(&request->rq_import->imp_lock);
-                list_del_init(&request->rq_mod_list);
-                list_del_init(&request->rq_replay_list);
-                if (!locked)
-                        spin_unlock(&request->rq_import->imp_lock);
+               if (!locked)
+                       spin_lock(&request->rq_import->imp_lock);
+               cfs_list_del_init(&request->rq_replay_list);
+               if (!locked)
+                       spin_unlock(&request->rq_import->imp_lock);
         }
-        LASSERTF(list_empty(&request->rq_replay_list), "req %p\n", request);
+        LASSERTF(cfs_list_empty(&request->rq_replay_list), "req %p\n", request);
 
-        if (atomic_read(&request->rq_refcount) != 0) {
+        if (cfs_atomic_read(&request->rq_refcount) != 0) {
                 DEBUG_REQ(D_ERROR, request,
                           "freeing request with nonzero refcount");
                 LBUG();
@@ -1753,28 +2274,40 @@ static void __ptlrpc_free_req(struct ptlrpc_request *request, int locked)
                 class_import_put(request->rq_import);
                 request->rq_import = NULL;
         }
-        if (request->rq_bulk != NULL)
-                ptlrpc_free_bulk(request->rq_bulk);
+       if (request->rq_bulk != NULL)
+               ptlrpc_free_bulk_pin(request->rq_bulk);
 
         if (request->rq_reqbuf != NULL || request->rq_clrbuf != NULL)
                 sptlrpc_cli_free_reqbuf(request);
 
-        sptlrpc_req_put_ctx(request, !locked);
+        if (request->rq_cli_ctx)
+                sptlrpc_req_put_ctx(request, !locked);
 
         if (request->rq_pool)
                 __ptlrpc_free_req_to_pool(request);
         else
-                OBD_FREE(request, sizeof(*request));
-        EXIT;
+               ptlrpc_request_cache_free(request);
+       EXIT;
 }
 
 static int __ptlrpc_req_finished(struct ptlrpc_request *request, int locked);
+/**
+ * Drop one request reference. Must be called with import imp_lock held.
+ * When reference count drops to zero, reuqest is freed.
+ */
 void ptlrpc_req_finished_with_imp_lock(struct ptlrpc_request *request)
 {
-        LASSERT_SPIN_LOCKED(&request->rq_import->imp_lock);
-        (void)__ptlrpc_req_finished(request, 1);
+       LASSERT(spin_is_locked(&request->rq_import->imp_lock));
+       (void)__ptlrpc_req_finished(request, 1);
 }
+EXPORT_SYMBOL(ptlrpc_req_finished_with_imp_lock);
 
+/**
+ * Helper function
+ * Drops one reference count for request \a request.
+ * \a locked set indicates that caller holds import imp_lock.
+ * Frees the request whe reference count reaches zero.
+ */
 static int __ptlrpc_req_finished(struct ptlrpc_request *request, int locked)
 {
         ENTRY;
@@ -1789,9 +2322,9 @@ static int __ptlrpc_req_finished(struct ptlrpc_request *request, int locked)
         }
 
         DEBUG_REQ(D_INFO, request, "refcount now %u",
-                  atomic_read(&request->rq_refcount) - 1);
+                  cfs_atomic_read(&request->rq_refcount) - 1);
 
-        if (atomic_dec_and_test(&request->rq_refcount)) {
+        if (cfs_atomic_dec_and_test(&request->rq_refcount)) {
                 __ptlrpc_free_req(request, locked);
                 RETURN(1);
         }
@@ -1799,76 +2332,85 @@ static int __ptlrpc_req_finished(struct ptlrpc_request *request, int locked)
         RETURN(0);
 }
 
+/**
+ * Drops one reference count for a request.
+ */
 void ptlrpc_req_finished(struct ptlrpc_request *request)
 {
         __ptlrpc_req_finished(request, 0);
 }
+EXPORT_SYMBOL(ptlrpc_req_finished);
 
+/**
+ * Returns xid of a \a request
+ */
 __u64 ptlrpc_req_xid(struct ptlrpc_request *request)
 {
         return request->rq_xid;
 }
 EXPORT_SYMBOL(ptlrpc_req_xid);
 
-/* Disengage the client's reply buffer from the network
+/**
+ * Disengage the client's reply buffer from the network
  * NB does _NOT_ unregister any client-side bulk.
  * IDEMPOTENT, but _not_ safe against concurrent callers.
  * The request owner (i.e. the thread doing the I/O) must call...
+ * Returns 0 on success or 1 if unregistering cannot be made.
  */
 int ptlrpc_unregister_reply(struct ptlrpc_request *request, int async)
 {
-        int                rc;
-        cfs_waitq_t       *wq;
-        struct l_wait_info lwi;
+       int                rc;
+       struct l_wait_info lwi;
 
-        /* 
-         * Might sleep. 
-         */
-        LASSERT(!in_interrupt());
+       /*
+        * Might sleep.
+        */
+       LASSERT(!in_interrupt());
 
-        /* 
-         * Let's setup deadline for reply unlink. 
-         */
-        if (OBD_FAIL_CHECK(OBD_FAIL_PTLRPC_LONG_REPL_UNLINK) && 
+       /*
+        * Let's setup deadline for reply unlink.
+        */
+        if (OBD_FAIL_CHECK(OBD_FAIL_PTLRPC_LONG_REPL_UNLINK) &&
             async && request->rq_reply_deadline == 0)
                 request->rq_reply_deadline = cfs_time_current_sec()+LONG_UNLINK;
 
-        /* 
-         * Nothing left to do. 
+        /*
+         * Nothing left to do.
          */
         if (!ptlrpc_client_recv_or_unlink(request))
                 RETURN(1);
 
         LNetMDUnlink(request->rq_reply_md_h);
 
-        /* 
-         * Let's check it once again. 
+        /*
+         * Let's check it once again.
          */
         if (!ptlrpc_client_recv_or_unlink(request))
                 RETURN(1);
 
-        /* 
-         * Move to "Unregistering" phase as reply was not unlinked yet. 
+        /*
+         * Move to "Unregistering" phase as reply was not unlinked yet.
          */
         ptlrpc_rqphase_move(request, RQ_PHASE_UNREGISTERING);
 
-        /* 
-         * Do not wait for unlink to finish. 
+        /*
+         * Do not wait for unlink to finish.
          */
         if (async)
                 RETURN(0);
 
-        /* 
+        /*
          * We have to l_wait_event() whatever the result, to give liblustre
          * a chance to run reply_in_callback(), and to make sure we've
-         * unlinked before returning a req to the pool. 
+         * unlinked before returning a req to the pool.
          */
-        if (request->rq_set != NULL)
-                wq = &request->rq_set->set_waitq;
-        else
-                wq = &request->rq_reply_waitq;
-
         for (;;) {
+#ifdef __KERNEL__
+               /* The wq argument is ignored by user-space wait_event macros */
+               wait_queue_head_t *wq = (request->rq_set != NULL) ?
+                                       &request->rq_set->set_waitq :
+                                       &request->rq_reply_waitq;
+#endif
                 /* Network access will complete in finite time but the HUGE
                  * timeout lets us CWARN for visibility of sluggish NALs */
                 lwi = LWI_TIMEOUT_INTERVAL(cfs_time_seconds(LONG_UNLINK),
@@ -1879,7 +2421,7 @@ int ptlrpc_unregister_reply(struct ptlrpc_request *request, int async)
                         ptlrpc_rqphase_move(request, request->rq_next_phase);
                         RETURN(1);
                 }
-  
+
                 LASSERT(rc == -ETIMEDOUT);
                 DEBUG_REQ(D_WARNING, request, "Unexpectedly long timeout "
                           "rvcng=%d unlnk=%d", request->rq_receiving_reply,
@@ -1887,86 +2429,145 @@ int ptlrpc_unregister_reply(struct ptlrpc_request *request, int async)
         }
         RETURN(0);
 }
+EXPORT_SYMBOL(ptlrpc_unregister_reply);
 
-/* caller must hold imp->imp_lock */
-void ptlrpc_free_committed(struct obd_import *imp)
+static void ptlrpc_free_request(struct ptlrpc_request *req)
 {
-        struct list_head *tmp, *saved;
-        struct ptlrpc_request *req;
-        struct ptlrpc_request *last_req = NULL; /* temporary fire escape */
-        ENTRY;
+       spin_lock(&req->rq_lock);
+       req->rq_replay = 0;
+       spin_unlock(&req->rq_lock);
+
+       if (req->rq_commit_cb != NULL)
+               req->rq_commit_cb(req);
+       cfs_list_del_init(&req->rq_replay_list);
+
+       __ptlrpc_req_finished(req, 1);
+}
+
+/**
+ * the request is committed and dropped from the replay list of its import
+ */
+void ptlrpc_request_committed(struct ptlrpc_request *req, int force)
+{
+       struct obd_import       *imp = req->rq_import;
 
-        LASSERT(imp != NULL);
+       spin_lock(&imp->imp_lock);
+       if (cfs_list_empty(&req->rq_replay_list)) {
+               spin_unlock(&imp->imp_lock);
+               return;
+       }
 
-        LASSERT_SPIN_LOCKED(&imp->imp_lock);
+       if (force || req->rq_transno <= imp->imp_peer_committed_transno)
+               ptlrpc_free_request(req);
+
+       spin_unlock(&imp->imp_lock);
+}
+EXPORT_SYMBOL(ptlrpc_request_committed);
+
+/**
+ * Iterates through replay_list on import and prunes
+ * all requests have transno smaller than last_committed for the
+ * import and don't have rq_replay set.
+ * Since requests are sorted in transno order, stops when meetign first
+ * transno bigger than last_committed.
+ * caller must hold imp->imp_lock
+ */
+void ptlrpc_free_committed(struct obd_import *imp)
+{
+       struct ptlrpc_request   *req, *saved;
+       struct ptlrpc_request   *last_req = NULL; /* temporary fire escape */
+       bool                     skip_committed_list = true;
+       ENTRY;
+
+       LASSERT(imp != NULL);
+       LASSERT(spin_is_locked(&imp->imp_lock));
 
 
         if (imp->imp_peer_committed_transno == imp->imp_last_transno_checked &&
             imp->imp_generation == imp->imp_last_generation_checked) {
-                CDEBUG(D_RPCTRACE, "%s: skip recheck: last_committed "LPU64"\n",
+                CDEBUG(D_INFO, "%s: skip recheck: last_committed "LPU64"\n",
                        imp->imp_obd->obd_name, imp->imp_peer_committed_transno);
-                EXIT;
-                return;
+               RETURN_EXIT;
         }
         CDEBUG(D_RPCTRACE, "%s: committing for last_committed "LPU64" gen %d\n",
                imp->imp_obd->obd_name, imp->imp_peer_committed_transno,
                imp->imp_generation);
+
+       if (imp->imp_generation != imp->imp_last_generation_checked)
+               skip_committed_list = false;
+
         imp->imp_last_transno_checked = imp->imp_peer_committed_transno;
         imp->imp_last_generation_checked = imp->imp_generation;
 
-        list_for_each_safe(tmp, saved, &imp->imp_replay_list) {
-                req = list_entry(tmp, struct ptlrpc_request, rq_replay_list);
-
+       cfs_list_for_each_entry_safe(req, saved, &imp->imp_replay_list,
+                                    rq_replay_list) {
                 /* XXX ok to remove when 1357 resolved - rread 05/29/03  */
                 LASSERT(req != last_req);
                 last_req = req;
 
+                if (req->rq_transno == 0) {
+                        DEBUG_REQ(D_EMERG, req, "zero transno during replay");
+                        LBUG();
+                }
                 if (req->rq_import_generation < imp->imp_generation) {
                         DEBUG_REQ(D_RPCTRACE, req, "free request with old gen");
                         GOTO(free_req, 0);
                 }
 
-                if (req->rq_replay) {
-                        DEBUG_REQ(D_RPCTRACE, req, "keeping (FL_REPLAY)");
-                        continue;
-                }
-
                 /* not yet committed */
                 if (req->rq_transno > imp->imp_peer_committed_transno) {
                         DEBUG_REQ(D_RPCTRACE, req, "stopping search");
                         break;
                 }
 
-                DEBUG_REQ(D_RPCTRACE, req, "commit (last_committed "LPU64")",
+               if (req->rq_replay) {
+                       DEBUG_REQ(D_RPCTRACE, req, "keeping (FL_REPLAY)");
+                       cfs_list_move_tail(&req->rq_replay_list,
+                                          &imp->imp_committed_list);
+                       continue;
+               }
+
+                DEBUG_REQ(D_INFO, req, "commit (last_committed "LPU64")",
                           imp->imp_peer_committed_transno);
 free_req:
-                spin_lock(&req->rq_lock);
-                req->rq_replay = 0;
-                spin_unlock(&req->rq_lock);
-                if (req->rq_commit_cb != NULL)
-                        req->rq_commit_cb(req);
-                list_del_init(&req->rq_replay_list);
-                __ptlrpc_req_finished(req, 1);
+               ptlrpc_free_request(req);
         }
 
+       if (skip_committed_list)
+               GOTO(out, 0);
+
+       cfs_list_for_each_entry_safe(req, saved, &imp->imp_committed_list,
+                                    rq_replay_list) {
+               LASSERT(req->rq_transno != 0);
+               if (req->rq_import_generation < imp->imp_generation) {
+                       DEBUG_REQ(D_RPCTRACE, req, "free stale open request");
+                       ptlrpc_free_request(req);
+               }
+       }
+out:
         EXIT;
-        return;
 }
 
 void ptlrpc_cleanup_client(struct obd_import *imp)
 {
         ENTRY;
         EXIT;
-        return;
 }
+EXPORT_SYMBOL(ptlrpc_cleanup_client);
 
+/**
+ * Schedule previously sent request for resend.
+ * For bulk requests we assign new xid (to avoid problems with
+ * lost replies and therefore several transfers landing into same buffer
+ * from different sending attempts).
+ */
 void ptlrpc_resend_req(struct ptlrpc_request *req)
 {
         DEBUG_REQ(D_HA, req, "going to resend");
         lustre_msg_set_handle(req->rq_reqmsg, &(struct lustre_handle){ 0 });
         req->rq_status = -EAGAIN;
 
-        spin_lock(&req->rq_lock);
+       spin_lock(&req->rq_lock);
         req->rq_resend = 1;
         req->rq_net_err = 0;
         req->rq_timedout = 0;
@@ -1979,71 +2580,57 @@ void ptlrpc_resend_req(struct ptlrpc_request *req)
                        old_xid, req->rq_xid);
         }
         ptlrpc_client_wake_req(req);
-        spin_unlock(&req->rq_lock);
+       spin_unlock(&req->rq_lock);
 }
+EXPORT_SYMBOL(ptlrpc_resend_req);
 
 /* XXX: this function and rq_status are currently unused */
 void ptlrpc_restart_req(struct ptlrpc_request *req)
 {
-        DEBUG_REQ(D_HA, req, "restarting (possibly-)completed request");
-        req->rq_status = -ERESTARTSYS;
+       DEBUG_REQ(D_HA, req, "restarting (possibly-)completed request");
+       req->rq_status = -ERESTARTSYS;
 
-        spin_lock(&req->rq_lock);
-        req->rq_restart = 1;
-        req->rq_timedout = 0;
-        ptlrpc_client_wake_req(req);
-        spin_unlock(&req->rq_lock);
-}
-
-static int expired_request(void *data)
-{
-        struct ptlrpc_request *req = data;
-        ENTRY;
-
-        /* 
-         * Some failure can suspend regular timeouts.
-         */
-        if (ptlrpc_check_suspend())
-                RETURN(1);
-
-        /* 
-         * Deadline may have changed with an early reply. 
-         */
-        if (req->rq_deadline > cfs_time_current_sec())
-                RETURN(1);
-
-        RETURN(ptlrpc_expire_one_request(req, 0));
-}
-
-static void interrupted_request(void *data)
-{
-        struct ptlrpc_request *req = data;
-        DEBUG_REQ(D_HA, req, "request interrupted");
-        spin_lock(&req->rq_lock);
-        req->rq_intr = 1;
-        spin_unlock(&req->rq_lock);
+       spin_lock(&req->rq_lock);
+       req->rq_restart = 1;
+       req->rq_timedout = 0;
+       ptlrpc_client_wake_req(req);
+       spin_unlock(&req->rq_lock);
 }
+EXPORT_SYMBOL(ptlrpc_restart_req);
 
+/**
+ * Grab additional reference on a request \a req
+ */
 struct ptlrpc_request *ptlrpc_request_addref(struct ptlrpc_request *req)
 {
         ENTRY;
-        atomic_inc(&req->rq_refcount);
+        cfs_atomic_inc(&req->rq_refcount);
         RETURN(req);
 }
+EXPORT_SYMBOL(ptlrpc_request_addref);
 
+/**
+ * Add a request to import replay_list.
+ * Must be called under imp_lock
+ */
 void ptlrpc_retain_replayable_request(struct ptlrpc_request *req,
                                       struct obd_import *imp)
 {
-        struct list_head *tmp;
+       cfs_list_t *tmp;
 
-        LASSERT_SPIN_LOCKED(&imp->imp_lock);
+       LASSERT(spin_is_locked(&imp->imp_lock));
+
+        if (req->rq_transno == 0) {
+                DEBUG_REQ(D_EMERG, req, "saving request with zero transno");
+                LBUG();
+        }
 
         /* clear this for new requests that were resent as well
            as resent replayed requests. */
         lustre_msg_clear_flags(req->rq_reqmsg, MSG_RESENT);
 
         /* don't re-add requests that have been replayed */
-        if (!list_empty(&req->rq_replay_list))
+        if (!cfs_list_empty(&req->rq_replay_list))
                 return;
 
         lustre_msg_add_flags(req->rq_reqmsg, MSG_REPLAY);
@@ -2051,9 +2638,10 @@ void ptlrpc_retain_replayable_request(struct ptlrpc_request *req,
         LASSERT(imp->imp_replayable);
         /* Balanced in ptlrpc_free_committed, usually. */
         ptlrpc_request_addref(req);
-        list_for_each_prev(tmp, &imp->imp_replay_list) {
+        cfs_list_for_each_prev(tmp, &imp->imp_replay_list) {
                 struct ptlrpc_request *iter =
-                        list_entry(tmp, struct ptlrpc_request, rq_replay_list);
+                        cfs_list_entry(tmp, struct ptlrpc_request,
+                                       rq_replay_list);
 
                 /* We may have duplicate transnos if we create and then
                  * open a file, or for closes retained if to match creating
@@ -2070,245 +2658,56 @@ void ptlrpc_retain_replayable_request(struct ptlrpc_request *req,
                                 continue;
                 }
 
-                list_add(&req->rq_replay_list, &iter->rq_replay_list);
+                cfs_list_add(&req->rq_replay_list, &iter->rq_replay_list);
                 return;
         }
 
-        list_add_tail(&req->rq_replay_list, &imp->imp_replay_list);
+        cfs_list_add(&req->rq_replay_list, &imp->imp_replay_list);
 }
+EXPORT_SYMBOL(ptlrpc_retain_replayable_request);
 
+/**
+ * Send request and wait until it completes.
+ * Returns request processing status.
+ */
 int ptlrpc_queue_wait(struct ptlrpc_request *req)
 {
-        int rc = 0;
-        int brc;
-        struct l_wait_info lwi;
-        struct obd_import *imp = req->rq_import;
-        cfs_duration_t timeout = CFS_TICK;
-        long timeoutl;
+        struct ptlrpc_request_set *set;
+        int rc;
         ENTRY;
 
         LASSERT(req->rq_set == NULL);
         LASSERT(!req->rq_receiving_reply);
 
-        /* for distributed debugging */
-        lustre_msg_set_status(req->rq_reqmsg, cfs_curproc_pid());
-        LASSERT(imp->imp_obd != NULL);
-        CDEBUG(D_RPCTRACE, "Sending RPC pname:cluuid:pid:xid:nid:opc "
-               "%s:%s:%d:"LPU64":%s:%d\n", cfs_curproc_comm(),
-               imp->imp_obd->obd_uuid.uuid,
-               lustre_msg_get_status(req->rq_reqmsg), req->rq_xid,
-               libcfs_nid2str(imp->imp_connection->c_peer.nid),
-               lustre_msg_get_opc(req->rq_reqmsg));
-
-        /* Mark phase here for a little debug help */
-        ptlrpc_rqphase_move(req, RQ_PHASE_RPC);
-
-        spin_lock(&imp->imp_lock);
-        req->rq_import_generation = imp->imp_generation;
-restart:
-        if (ptlrpc_import_delay_req(imp, req, &rc)) {
-                list_del_init(&req->rq_list);
-                list_add_tail(&req->rq_list, &imp->imp_delayed_list);
-                atomic_inc(&imp->imp_inflight);
-                spin_unlock(&imp->imp_lock);
-
-                DEBUG_REQ(D_HA, req, "\"%s\" waiting for recovery: (%s != %s)",
-                          cfs_curproc_comm(),
-                          ptlrpc_import_state_name(req->rq_send_state),
-                          ptlrpc_import_state_name(imp->imp_state));
-                lwi = LWI_INTR(interrupted_request, req);
-                rc = l_wait_event(req->rq_reply_waitq,
-                                  (req->rq_send_state == imp->imp_state ||
-                                   req->rq_err || req->rq_intr),
-                                  &lwi);
-                DEBUG_REQ(D_HA, req, "\"%s\" awake: (%s == %s or %d/%d == 1)",
-                          cfs_curproc_comm(),
-                          ptlrpc_import_state_name(imp->imp_state),
-                          ptlrpc_import_state_name(req->rq_send_state),
-                          req->rq_err, req->rq_intr);
-
-                spin_lock(&imp->imp_lock);
-                list_del_init(&req->rq_list);
-                atomic_dec(&imp->imp_inflight);
-
-                if (req->rq_err) {
-                        /* rq_status was set locally */
-                        rc = -EIO;
-                }
-                else if (req->rq_intr) {
-                        rc = -EINTR;
-                }
-                else if (req->rq_no_resend) {
-                        spin_unlock(&imp->imp_lock);
-                        GOTO(out, rc = -ETIMEDOUT);
-                }
-                else {
-                        GOTO(restart, rc);
-                }
-        }
-
-        if (rc != 0) {
-                spin_unlock(&imp->imp_lock);
-                req->rq_status = rc; // XXX this ok?
-                GOTO(out, rc);
-        }
-
-        if (req->rq_resend) {
-                lustre_msg_add_flags(req->rq_reqmsg, MSG_RESENT);
-
-                if (req->rq_bulk != NULL) {
-                        ptlrpc_unregister_bulk(req, 0);
-
-                        /* bulk requests are supposed to be
-                         * idempotent, so we are free to bump the xid
-                         * here, which we need to do before
-                         * registering the bulk again (bug 6371).
-                         * print the old xid first for sanity.
-                         */
-                        DEBUG_REQ(D_HA, req, "bumping xid for bulk: ");
-                        req->rq_xid = ptlrpc_next_xid();
-                }
-
-                DEBUG_REQ(D_HA, req, "resending: ");
-        }
-
-        /* XXX this is the same as ptlrpc_set_wait */
-        LASSERT(list_empty(&req->rq_list));
-        list_add_tail(&req->rq_list, &imp->imp_sending_list);
-        atomic_inc(&imp->imp_inflight);
-        spin_unlock(&imp->imp_lock);
-
-        rc = sptlrpc_req_refresh_ctx(req, 0);
-        if (rc) {
-                if (req->rq_err) {
-                        /* we got fatal ctx refresh error, directly jump out
-                         * thus we can pass back the actual error code.
-                         */
-                        spin_lock(&imp->imp_lock);
-                        list_del_init(&req->rq_list);
-                        atomic_dec(&imp->imp_inflight);
-                        spin_unlock(&imp->imp_lock);
-
-                        CERROR("Failed to refresh ctx of req %p: %d\n",
-                               req, rc);
-                        GOTO(out, rc);
-                }
-                /* simulating we got error during send rpc */
-                goto after_send;
-        }
-
-        rc = ptl_send_rpc(req, 0);
-        if (rc)
-                DEBUG_REQ(D_HA, req, "send failed (%d); recovering", rc);
-repeat:
-        timeoutl = req->rq_deadline - cfs_time_current_sec();
-        timeout = (timeoutl <= 0 || rc) ? CFS_TICK :
-                cfs_time_seconds(timeoutl);
-        DEBUG_REQ(D_NET, req,
-                  "-- sleeping for "CFS_DURATION_T" ticks", timeout);
-        lwi = LWI_TIMEOUT_INTR(timeout, expired_request, interrupted_request,
-                               req);
-        brc = l_wait_event(req->rq_reply_waitq, ptlrpc_check_reply(req), &lwi);
-        if (brc == -ETIMEDOUT && ((req->rq_deadline > cfs_time_current_sec()) ||
-                                 ptlrpc_check_and_wait_suspend(req)))
-                goto repeat;
-
-after_send:
-        CDEBUG(D_RPCTRACE, "Completed RPC pname:cluuid:pid:xid:nid:opc "
-               "%s:%s:%d:"LPU64":%s:%d\n", cfs_curproc_comm(),
-               imp->imp_obd->obd_uuid.uuid,
-               lustre_msg_get_status(req->rq_reqmsg), req->rq_xid,
-               libcfs_nid2str(imp->imp_connection->c_peer.nid),
-               lustre_msg_get_opc(req->rq_reqmsg));
-
-        /* If the reply was received normally, this just grabs the spinlock
-         * (ensuring the reply callback has returned), sees that
-         * req->rq_receiving_reply is clear and returns. */
-        ptlrpc_unregister_reply(req, 0);
-
-        spin_lock(&imp->imp_lock);
-        list_del_init(&req->rq_list);
-        atomic_dec(&imp->imp_inflight);
-        spin_unlock(&imp->imp_lock);
-
-        if (req->rq_err) {
-                DEBUG_REQ(D_RPCTRACE, req, "err rc=%d status=%d",
-                          rc, req->rq_status);
-                GOTO(out, rc = rc ? rc : -EIO);
-        }
-
-        if (req->rq_intr) {
-                /* Should only be interrupted if we timed out. */
-                if (!req->rq_timedout)
-                        DEBUG_REQ(D_ERROR, req,
-                                  "rq_intr set but rq_timedout not");
-                GOTO(out, rc = -EINTR);
-        }
-
-        /* Resend if we need to */
-        if (req->rq_resend) {
-                /* ...unless we were specifically told otherwise. */
-                if (req->rq_no_resend)
-                        GOTO(out, rc = -ETIMEDOUT);
-                spin_lock(&imp->imp_lock);
-                goto restart;
-        }
-
-        if (req->rq_timedout) {                 /* non-recoverable timeout */
-                GOTO(out, rc = -ETIMEDOUT);
+        set = ptlrpc_prep_set();
+        if (set == NULL) {
+                CERROR("Unable to allocate ptlrpc set.");
+                RETURN(-ENOMEM);
         }
 
-        if (!ptlrpc_client_replied(req)) {
-                /* How can this be? -eeb */
-                DEBUG_REQ(D_ERROR, req, "!rq_replied: ");
-                LBUG();
-                GOTO(out, rc = req->rq_status);
-        }
+       /* for distributed debugging */
+       lustre_msg_set_status(req->rq_reqmsg, current_pid());
 
-        rc = after_reply(req);
-        /* NB may return +ve success rc */
-        if (req->rq_resend) {
-                spin_lock(&imp->imp_lock);
-                goto restart;
-        }
-
- out:
-        if (req->rq_bulk != NULL) {
-                if (rc >= 0) {
-                        /* success so far.  Note that anything going wrong
-                         * with bulk now, is EXTREMELY strange, since the
-                         * server must have believed that the bulk
-                         * tranferred OK before she replied with success to
-                         * me. */
-                        lwi = LWI_TIMEOUT(timeout, NULL, NULL);
-                        brc = l_wait_event(req->rq_reply_waitq,
-                                           !ptlrpc_client_bulk_active(req),
-                                           &lwi);
-                        LASSERT(brc == 0 || brc == -ETIMEDOUT);
-                        if (brc != 0) {
-                                LASSERT(brc == -ETIMEDOUT);
-                                DEBUG_REQ(D_ERROR, req, "bulk timed out");
-                                rc = brc;
-                        } else if (!req->rq_bulk->bd_success) {
-                                DEBUG_REQ(D_ERROR, req, "bulk transfer failed");
-                                rc = -EIO;
-                        }
-                }
-                if (rc < 0)
-                        ptlrpc_unregister_bulk(req, 0);
-        }
+        /* add a ref for the set (see comment in ptlrpc_set_add_req) */
+        ptlrpc_request_addref(req);
+        ptlrpc_set_add_req(set, req);
+        rc = ptlrpc_set_wait(set);
+        ptlrpc_set_destroy(set);
 
-        LASSERT(!req->rq_receiving_reply);
-        ptlrpc_rqphase_move(req, RQ_PHASE_INTERPRET);
-        cfs_waitq_signal(&imp->imp_recovery_waitq);
         RETURN(rc);
 }
+EXPORT_SYMBOL(ptlrpc_queue_wait);
 
 struct ptlrpc_replay_async_args {
         int praa_old_state;
         int praa_old_status;
 };
 
+/**
+ * Callback used for replayed requests reply processing.
+ * In case of succesful reply calls registeresd request replay callback.
+ * In case of error restart replay process.
+ */
 static int ptlrpc_replay_interpret(const struct lu_env *env,
                                    struct ptlrpc_request *req,
                                    void * data, int rc)
@@ -2317,7 +2716,7 @@ static int ptlrpc_replay_interpret(const struct lu_env *env,
         struct obd_import *imp = req->rq_import;
 
         ENTRY;
-        atomic_dec(&imp->imp_replay_inflight);
+        cfs_atomic_dec(&imp->imp_replay_inflight);
 
         if (!ptlrpc_client_replied(req)) {
                 CERROR("request replay timed out, restarting recovery\n");
@@ -2329,9 +2728,41 @@ static int ptlrpc_replay_interpret(const struct lu_env *env,
              lustre_msg_get_status(req->rq_repmsg) == -ENODEV))
                 GOTO(out, rc = lustre_msg_get_status(req->rq_repmsg));
 
-        /* The transno had better not change over replay. */
-        LASSERT(lustre_msg_get_transno(req->rq_reqmsg) ==
-                lustre_msg_get_transno(req->rq_repmsg));
+        /** VBR: check version failure */
+        if (lustre_msg_get_status(req->rq_repmsg) == -EOVERFLOW) {
+               /** replay was failed due to version mismatch */
+               DEBUG_REQ(D_WARNING, req, "Version mismatch during replay\n");
+               spin_lock(&imp->imp_lock);
+               imp->imp_vbr_failed = 1;
+               imp->imp_no_lock_replay = 1;
+               spin_unlock(&imp->imp_lock);
+               lustre_msg_set_status(req->rq_repmsg, aa->praa_old_status);
+        } else {
+                /** The transno had better not change over replay. */
+                LASSERTF(lustre_msg_get_transno(req->rq_reqmsg) ==
+                         lustre_msg_get_transno(req->rq_repmsg) ||
+                         lustre_msg_get_transno(req->rq_repmsg) == 0,
+                         LPX64"/"LPX64"\n",
+                         lustre_msg_get_transno(req->rq_reqmsg),
+                         lustre_msg_get_transno(req->rq_repmsg));
+        }
+
+       spin_lock(&imp->imp_lock);
+       /** if replays by version then gap occur on server, no trust to locks */
+       if (lustre_msg_get_flags(req->rq_repmsg) & MSG_VERSION_REPLAY)
+               imp->imp_no_lock_replay = 1;
+       imp->imp_last_replay_transno = lustre_msg_get_transno(req->rq_reqmsg);
+       spin_unlock(&imp->imp_lock);
+        LASSERT(imp->imp_last_replay_transno);
+
+        /* transaction number shouldn't be bigger than the latest replayed */
+        if (req->rq_transno > lustre_msg_get_transno(req->rq_reqmsg)) {
+                DEBUG_REQ(D_ERROR, req,
+                          "Reported transno "LPU64" is bigger than the "
+                          "replayed one: "LPU64, req->rq_transno,
+                          lustre_msg_get_transno(req->rq_reqmsg));
+                GOTO(out, rc = -EINVAL);
+        }
 
         DEBUG_REQ(D_HA, req, "got rep");
 
@@ -2353,13 +2784,9 @@ static int ptlrpc_replay_interpret(const struct lu_env *env,
          * Errors while replay can set transno to 0, but
          * imp_last_replay_transno shouldn't be set to 0 anyway
          */
-        if (req->rq_transno > 0) {
-                spin_lock(&imp->imp_lock);
-                LASSERT(req->rq_transno <= imp->imp_last_replay_transno);
-                imp->imp_last_replay_transno = req->rq_transno;
-                spin_unlock(&imp->imp_lock);
-        } else
+        if (req->rq_transno == 0)
                 CERROR("Transno is 0 during replay!\n");
+
         /* continue with recovery */
         rc = ptlrpc_import_recovery_state_machine(imp);
  out:
@@ -2367,19 +2794,22 @@ static int ptlrpc_replay_interpret(const struct lu_env *env,
 
         if (rc != 0)
                 /* this replay failed, so restart recovery */
-                ptlrpc_connect_import(imp, NULL);
+                ptlrpc_connect_import(imp);
 
         RETURN(rc);
 }
 
+/**
+ * Prepares and queues request for replay.
+ * Adds it to ptlrpcd queue for actual sending.
+ * Returns 0 on success.
+ */
 int ptlrpc_replay_req(struct ptlrpc_request *req)
 {
         struct ptlrpc_replay_async_args *aa;
         ENTRY;
 
         LASSERT(req->rq_import->imp_state == LUSTRE_IMP_REPLAY);
-        /* Not handling automatic bulk replay yet (or ever?) */
-        LASSERT(req->rq_bulk == NULL);
 
         LASSERT (sizeof (*aa) <= sizeof (req->rq_async_args));
         aa = ptlrpc_req_async_args(req);
@@ -2397,97 +2827,111 @@ int ptlrpc_replay_req(struct ptlrpc_request *req)
         /* Readjust the timeout for current conditions */
         ptlrpc_at_set_req_timeout(req);
 
+        /* Tell server the net_latency, so the server can calculate how long
+         * it should wait for next replay */
+        lustre_msg_set_service_time(req->rq_reqmsg,
+                                    ptlrpc_at_get_net_latency(req));
         DEBUG_REQ(D_HA, req, "REPLAY");
 
-        atomic_inc(&req->rq_import->imp_replay_inflight);
+        cfs_atomic_inc(&req->rq_import->imp_replay_inflight);
         ptlrpc_request_addref(req); /* ptlrpcd needs a ref */
 
-        ptlrpcd_add_req(req, PSCOPE_OTHER);
+        ptlrpcd_add_req(req, PDL_POLICY_LOCAL, -1);
         RETURN(0);
 }
+EXPORT_SYMBOL(ptlrpc_replay_req);
 
+/**
+ * Aborts all in-flight request on import \a imp sending and delayed lists
+ */
 void ptlrpc_abort_inflight(struct obd_import *imp)
 {
-        struct list_head *tmp, *n;
+        cfs_list_t *tmp, *n;
         ENTRY;
 
         /* Make sure that no new requests get processed for this import.
          * ptlrpc_{queue,set}_wait must (and does) hold imp_lock while testing
          * this flag and then putting requests on sending_list or delayed_list.
          */
-        spin_lock(&imp->imp_lock);
+       spin_lock(&imp->imp_lock);
 
         /* XXX locking?  Maybe we should remove each request with the list
          * locked?  Also, how do we know if the requests on the list are
          * being freed at this time?
          */
-        list_for_each_safe(tmp, n, &imp->imp_sending_list) {
+        cfs_list_for_each_safe(tmp, n, &imp->imp_sending_list) {
                 struct ptlrpc_request *req =
-                        list_entry(tmp, struct ptlrpc_request, rq_list);
+                        cfs_list_entry(tmp, struct ptlrpc_request, rq_list);
 
                 DEBUG_REQ(D_RPCTRACE, req, "inflight");
 
-                spin_lock (&req->rq_lock);
-                if (req->rq_import_generation < imp->imp_generation) {
-                        req->rq_err = 1;
-                        req->rq_status = -EINTR;
-                        ptlrpc_client_wake_req(req);
-                }
-                spin_unlock (&req->rq_lock);
-        }
+               spin_lock(&req->rq_lock);
+               if (req->rq_import_generation < imp->imp_generation) {
+                       req->rq_err = 1;
+                       req->rq_status = -EIO;
+                       ptlrpc_client_wake_req(req);
+               }
+               spin_unlock(&req->rq_lock);
+       }
 
-        list_for_each_safe(tmp, n, &imp->imp_delayed_list) {
-                struct ptlrpc_request *req =
-                        list_entry(tmp, struct ptlrpc_request, rq_list);
+       cfs_list_for_each_safe(tmp, n, &imp->imp_delayed_list) {
+               struct ptlrpc_request *req =
+                       cfs_list_entry(tmp, struct ptlrpc_request, rq_list);
 
-                DEBUG_REQ(D_RPCTRACE, req, "aborting waiting req");
+               DEBUG_REQ(D_RPCTRACE, req, "aborting waiting req");
 
-                spin_lock (&req->rq_lock);
-                if (req->rq_import_generation < imp->imp_generation) {
-                        req->rq_err = 1;
-                        req->rq_status = -EINTR;
-                        ptlrpc_client_wake_req(req);
-                }
-                spin_unlock (&req->rq_lock);
-        }
+               spin_lock(&req->rq_lock);
+               if (req->rq_import_generation < imp->imp_generation) {
+                       req->rq_err = 1;
+                       req->rq_status = -EIO;
+                       ptlrpc_client_wake_req(req);
+               }
+               spin_unlock(&req->rq_lock);
+       }
 
-        /* Last chance to free reqs left on the replay list, but we
-         * will still leak reqs that haven't committed.  */
-        if (imp->imp_replayable)
-                ptlrpc_free_committed(imp);
+       /* Last chance to free reqs left on the replay list, but we
+        * will still leak reqs that haven't committed.  */
+       if (imp->imp_replayable)
+               ptlrpc_free_committed(imp);
 
-        spin_unlock(&imp->imp_lock);
+       spin_unlock(&imp->imp_lock);
 
-        EXIT;
+       EXIT;
 }
+EXPORT_SYMBOL(ptlrpc_abort_inflight);
 
+/**
+ * Abort all uncompleted requests in request set \a set
+ */
 void ptlrpc_abort_set(struct ptlrpc_request_set *set)
 {
-        struct list_head *tmp, *pos;
+        cfs_list_t *tmp, *pos;
 
         LASSERT(set != NULL);
 
-        list_for_each_safe(pos, tmp, &set->set_requests) {
+        cfs_list_for_each_safe(pos, tmp, &set->set_requests) {
                 struct ptlrpc_request *req =
-                        list_entry(pos, struct ptlrpc_request, rq_set_chain);
+                        cfs_list_entry(pos, struct ptlrpc_request,
+                                       rq_set_chain);
 
-                spin_lock(&req->rq_lock);
-                if (req->rq_phase != RQ_PHASE_RPC) {
-                        spin_unlock(&req->rq_lock);
-                        continue;
-                }
+               spin_lock(&req->rq_lock);
+               if (req->rq_phase != RQ_PHASE_RPC) {
+                       spin_unlock(&req->rq_lock);
+                       continue;
+               }
 
-                req->rq_err = 1;
-                req->rq_status = -EINTR;
-                ptlrpc_client_wake_req(req);
-                spin_unlock(&req->rq_lock);
-        }
+               req->rq_err = 1;
+               req->rq_status = -EINTR;
+               ptlrpc_client_wake_req(req);
+               spin_unlock(&req->rq_lock);
+       }
 }
 
 static __u64 ptlrpc_last_xid;
 static spinlock_t ptlrpc_last_xid_lock;
 
-/* Initialize the XID for the node.  This is common among all requests on
+/**
+ * Initialize the XID for the node.  This is common among all requests on
  * this node, and only requires the property that it is monotonically
  * increasing.  It does not need to be sequential.  Since this is also used
  * as the RDMA match bits, it is important that a single client NOT have
@@ -2495,7 +2939,7 @@ static spinlock_t ptlrpc_last_xid_lock;
  * NOT want to have an XID per target or similar.
  *
  * To avoid an unlikely collision between match bits after a client reboot
- * (which would cause old to be delivered into the wrong buffer) we initialize
+ * (which would deliver old data into the wrong RDMA buffer) initialize
  * the XID based on the current time, assuming a maximum RPC rate of 1M RPC/s.
  * If the time is clearly incorrect, we instead use a 62-bit random number.
  * In the worst case the random number will overflow 1M RPCs per second in
@@ -2504,39 +2948,209 @@ static spinlock_t ptlrpc_last_xid_lock;
 #define YEAR_2004 (1ULL << 30)
 void ptlrpc_init_xid(void)
 {
-        time_t now = cfs_time_current_sec();
+       time_t now = cfs_time_current_sec();
 
-        spin_lock_init(&ptlrpc_last_xid_lock);
-        if (now < YEAR_2004) {
-                ll_get_random_bytes(&ptlrpc_last_xid, sizeof(ptlrpc_last_xid));
-                ptlrpc_last_xid >>= 2;
-                ptlrpc_last_xid |= (1ULL << 61);
-        } else {
-                ptlrpc_last_xid = (now << 20);
-        }
+       spin_lock_init(&ptlrpc_last_xid_lock);
+       if (now < YEAR_2004) {
+               cfs_get_random_bytes(&ptlrpc_last_xid, sizeof(ptlrpc_last_xid));
+               ptlrpc_last_xid >>= 2;
+               ptlrpc_last_xid |= (1ULL << 61);
+       } else {
+               ptlrpc_last_xid = (__u64)now << 20;
+       }
+
+       /* Need to always be aligned to a power-of-two for mutli-bulk BRW */
+       CLASSERT((PTLRPC_BULK_OPS_COUNT & (PTLRPC_BULK_OPS_COUNT - 1)) == 0);
+       ptlrpc_last_xid &= PTLRPC_BULK_OPS_MASK;
 }
 
+/**
+ * Increase xid and returns resulting new value to the caller.
+ *
+ * Multi-bulk BRW RPCs consume multiple XIDs for each bulk transfer, starting
+ * at the returned xid, up to xid + PTLRPC_BULK_OPS_COUNT - 1. The BRW RPC
+ * itself uses the last bulk xid needed, so the server can determine the
+ * the number of bulk transfers from the RPC XID and a bitmask.  The starting
+ * xid must align to a power-of-two value.
+ *
+ * This is assumed to be true due to the initial ptlrpc_last_xid
+ * value also being initialized to a power-of-two value. LU-1431
+ */
 __u64 ptlrpc_next_xid(void)
 {
-        __u64 tmp;
-        spin_lock(&ptlrpc_last_xid_lock);
-        tmp = ++ptlrpc_last_xid;
-        spin_unlock(&ptlrpc_last_xid_lock);
-        return tmp;
+       __u64 next;
+
+       spin_lock(&ptlrpc_last_xid_lock);
+       next = ptlrpc_last_xid + PTLRPC_BULK_OPS_COUNT;
+       ptlrpc_last_xid = next;
+       spin_unlock(&ptlrpc_last_xid_lock);
+
+       return next;
 }
+EXPORT_SYMBOL(ptlrpc_next_xid);
 
+/**
+ * Get a glimpse at what next xid value might have been.
+ * Returns possible next xid.
+ */
 __u64 ptlrpc_sample_next_xid(void)
 {
 #if BITS_PER_LONG == 32
-        /* need to avoid possible word tearing on 32-bit systems */
-        __u64 tmp;
-        spin_lock(&ptlrpc_last_xid_lock);
-        tmp = ptlrpc_last_xid + 1;
-        spin_unlock(&ptlrpc_last_xid_lock);
-        return tmp;
+       /* need to avoid possible word tearing on 32-bit systems */
+       __u64 next;
+
+       spin_lock(&ptlrpc_last_xid_lock);
+       next = ptlrpc_last_xid + PTLRPC_BULK_OPS_COUNT;
+       spin_unlock(&ptlrpc_last_xid_lock);
+
+       return next;
 #else
-        /* No need to lock, since returned value is racy anyways */
-        return ptlrpc_last_xid + 1;
+       /* No need to lock, since returned value is racy anyways */
+       return ptlrpc_last_xid + PTLRPC_BULK_OPS_COUNT;
 #endif
 }
 EXPORT_SYMBOL(ptlrpc_sample_next_xid);
+
+/**
+ * Functions for operating ptlrpc workers.
+ *
+ * A ptlrpc work is a function which will be running inside ptlrpc context.
+ * The callback shouldn't sleep otherwise it will block that ptlrpcd thread.
+ *
+ * 1. after a work is created, it can be used many times, that is:
+ *         handler = ptlrpcd_alloc_work();
+ *         ptlrpcd_queue_work();
+ *
+ *    queue it again when necessary:
+ *         ptlrpcd_queue_work();
+ *         ptlrpcd_destroy_work();
+ * 2. ptlrpcd_queue_work() can be called by multiple processes meanwhile, but
+ *    it will only be queued once in any time. Also as its name implies, it may
+ *    have delay before it really runs by ptlrpcd thread.
+ */
+struct ptlrpc_work_async_args {
+       int   (*cb)(const struct lu_env *, void *);
+       void   *cbdata;
+};
+
+static void ptlrpcd_add_work_req(struct ptlrpc_request *req)
+{
+       /* re-initialize the req */
+       req->rq_timeout         = obd_timeout;
+       req->rq_sent            = cfs_time_current_sec();
+       req->rq_deadline        = req->rq_sent + req->rq_timeout;
+       req->rq_reply_deadline  = req->rq_deadline;
+       req->rq_phase           = RQ_PHASE_INTERPRET;
+       req->rq_next_phase      = RQ_PHASE_COMPLETE;
+       req->rq_xid             = ptlrpc_next_xid();
+       req->rq_import_generation = req->rq_import->imp_generation;
+
+       ptlrpcd_add_req(req, PDL_POLICY_ROUND, -1);
+}
+
+static int work_interpreter(const struct lu_env *env,
+                           struct ptlrpc_request *req, void *data, int rc)
+{
+       struct ptlrpc_work_async_args *arg = data;
+
+       LASSERT(ptlrpcd_check_work(req));
+       LASSERT(arg->cb != NULL);
+
+       rc = arg->cb(env, arg->cbdata);
+
+       list_del_init(&req->rq_set_chain);
+       req->rq_set = NULL;
+
+       if (atomic_dec_return(&req->rq_refcount) > 1) {
+               atomic_set(&req->rq_refcount, 2);
+               ptlrpcd_add_work_req(req);
+       }
+       return rc;
+}
+
+static int worker_format;
+
+static int ptlrpcd_check_work(struct ptlrpc_request *req)
+{
+       return req->rq_pill.rc_fmt == (void *)&worker_format;
+}
+
+/**
+ * Create a work for ptlrpc.
+ */
+void *ptlrpcd_alloc_work(struct obd_import *imp,
+                        int (*cb)(const struct lu_env *, void *), void *cbdata)
+{
+       struct ptlrpc_request         *req = NULL;
+       struct ptlrpc_work_async_args *args;
+       ENTRY;
+
+       might_sleep();
+
+       if (cb == NULL)
+               RETURN(ERR_PTR(-EINVAL));
+
+        /* copy some code from deprecated fakereq. */
+        req = ptlrpc_request_cache_alloc(__GFP_IO);
+        if (req == NULL) {
+                CERROR("ptlrpc: run out of memory!\n");
+                RETURN(ERR_PTR(-ENOMEM));
+        }
+
+        req->rq_send_state = LUSTRE_IMP_FULL;
+        req->rq_type = PTL_RPC_MSG_REQUEST;
+        req->rq_import = class_import_get(imp);
+        req->rq_export = NULL;
+        req->rq_interpret_reply = work_interpreter;
+        /* don't want reply */
+        req->rq_receiving_reply = 0;
+        req->rq_must_unlink = 0;
+        req->rq_no_delay = req->rq_no_resend = 1;
+       req->rq_pill.rc_fmt = (void *)&worker_format;
+
+       spin_lock_init(&req->rq_lock);
+       CFS_INIT_LIST_HEAD(&req->rq_list);
+       CFS_INIT_LIST_HEAD(&req->rq_replay_list);
+       CFS_INIT_LIST_HEAD(&req->rq_set_chain);
+       CFS_INIT_LIST_HEAD(&req->rq_history_list);
+       CFS_INIT_LIST_HEAD(&req->rq_exp_list);
+       init_waitqueue_head(&req->rq_reply_waitq);
+       init_waitqueue_head(&req->rq_set_waitq);
+       atomic_set(&req->rq_refcount, 1);
+
+       CLASSERT (sizeof(*args) <= sizeof(req->rq_async_args));
+       args = ptlrpc_req_async_args(req);
+       args->cb     = cb;
+       args->cbdata = cbdata;
+
+       RETURN(req);
+}
+EXPORT_SYMBOL(ptlrpcd_alloc_work);
+
+void ptlrpcd_destroy_work(void *handler)
+{
+        struct ptlrpc_request *req = handler;
+
+        if (req)
+                ptlrpc_req_finished(req);
+}
+EXPORT_SYMBOL(ptlrpcd_destroy_work);
+
+int ptlrpcd_queue_work(void *handler)
+{
+       struct ptlrpc_request *req = handler;
+
+        /*
+         * Check if the req is already being queued.
+         *
+         * Here comes a trick: it lacks a way of checking if a req is being
+         * processed reliably in ptlrpc. Here I have to use refcount of req
+         * for this purpose. This is okay because the caller should use this
+         * req as opaque data. - Jinshan
+         */
+       LASSERT(atomic_read(&req->rq_refcount) > 0);
+       if (atomic_inc_return(&req->rq_refcount) == 2)
+               ptlrpcd_add_work_req(req);
+       return 0;
+}
+EXPORT_SYMBOL(ptlrpcd_queue_work);