LU-13802 ptlrpc: correctly remove inflight request

[fs/lustre-release.git] / lustre / ptlrpc / client.c

/*
 * GPL HEADER START
 *
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 only,
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License version 2 for more details (a copy is included
 * in the LICENSE file that accompanied this code).
 *
 * You should have received a copy of the GNU General Public License
 * version 2 along with this program; If not, see
 * http://www.gnu.org/licenses/gpl-2.0.html
 *
 * GPL HEADER END
 */
/*
 * Copyright (c) 2002, 2010, Oracle and/or its affiliates. All rights reserved.
 * Use is subject to license terms.
 *
 * Copyright (c) 2011, 2017, Intel Corporation.
 */
/*
 * This file is part of Lustre, http://www.lustre.org/
 */

/** Implementation of client-side PortalRPC interfaces */

#define DEBUG_SUBSYSTEM S_RPC

#include <linux/delay.h>
#include <linux/random.h>

#include <lnet/lib-lnet.h>
#include <obd_support.h>
#include <obd_class.h>
#include <lustre_lib.h>
#include <lustre_ha.h>
#include <lustre_import.h>
#include <lustre_req_layout.h>

#include "ptlrpc_internal.h"

static void ptlrpc_prep_bulk_page_pin(struct ptlrpc_bulk_desc *desc,
                                      struct page *page, int pageoffset,
                                      int len)
{
        __ptlrpc_prep_bulk_page(desc, page, pageoffset, len, 1);
}

static void ptlrpc_prep_bulk_page_nopin(struct ptlrpc_bulk_desc *desc,
                                        struct page *page, int pageoffset,
                                        int len)
{
        __ptlrpc_prep_bulk_page(desc, page, pageoffset, len, 0);
}

static void ptlrpc_release_bulk_page_pin(struct ptlrpc_bulk_desc *desc)
{
        int i;

        for (i = 0; i < desc->bd_iov_count ; i++)
                put_page(desc->bd_vec[i].bv_page);
}

static int ptlrpc_prep_bulk_frag_pages(struct ptlrpc_bulk_desc *desc,
                                       void *frag, int len)
{
        unsigned int offset = (unsigned long)frag & ~PAGE_MASK;

        ENTRY;
        while (len > 0) {
                int page_len = min_t(unsigned int, PAGE_SIZE - offset,
                                     len);
                struct page *p;

                if (!is_vmalloc_addr(frag))
                        p = virt_to_page((unsigned long)frag);
                else
                        p = vmalloc_to_page(frag);
                ptlrpc_prep_bulk_page_nopin(desc, p, offset, page_len);
                offset = 0;
                len -= page_len;
                frag += page_len;
        }

        RETURN(desc->bd_nob);
}

const struct ptlrpc_bulk_frag_ops ptlrpc_bulk_kiov_pin_ops = {
        .add_kiov_frag  = ptlrpc_prep_bulk_page_pin,
        .release_frags  = ptlrpc_release_bulk_page_pin,
};
EXPORT_SYMBOL(ptlrpc_bulk_kiov_pin_ops);

const struct ptlrpc_bulk_frag_ops ptlrpc_bulk_kiov_nopin_ops = {
        .add_kiov_frag  = ptlrpc_prep_bulk_page_nopin,
        .release_frags  = ptlrpc_release_bulk_noop,
        .add_iov_frag   = ptlrpc_prep_bulk_frag_pages,
};
EXPORT_SYMBOL(ptlrpc_bulk_kiov_nopin_ops);

static int ptlrpc_send_new_req(struct ptlrpc_request *req);
static int ptlrpcd_check_work(struct ptlrpc_request *req);
static int ptlrpc_unregister_reply(struct ptlrpc_request *request, int async);

/**
 * Initialize passed in client structure \a cl.
 */
void ptlrpc_init_client(int req_portal, int rep_portal, const char *name,
                        struct ptlrpc_client *cl)
{
        cl->cli_request_portal = req_portal;
        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,
                                                    u32 refnet)
{
        struct ptlrpc_connection *c;
        struct lnet_nid self;
        struct lnet_processid peer;
        int err;

        /*
         * ptlrpc_uuid_to_peer() initializes its 2nd parameter
         * before accessing its values.
         */
        err = ptlrpc_uuid_to_peer(uuid, &peer, &self, refnet);
        if (err != 0) {
                CNETERR("cannot find peer %s!\n", uuid->uuid);
                return NULL;
        }

        c = ptlrpc_connection_get(&peer, &self, uuid);
        if (c) {
                memcpy(c->c_remote_uuid.uuid,
                       uuid->uuid, sizeof(c->c_remote_uuid.uuid));
        }

        CDEBUG(D_INFO, "%s -> %p\n", uuid->uuid, c);

        return c;
}

/**
 * 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 int nfrags,
                                         unsigned int max_brw,
                                         enum ptlrpc_bulk_op_type type,
                                         unsigned int portal,
                                         const struct ptlrpc_bulk_frag_ops *ops)
{
        struct ptlrpc_bulk_desc *desc;
        int i;

        LASSERT(ops->add_kiov_frag != NULL);

        if (max_brw > PTLRPC_BULK_OPS_COUNT)
                RETURN(NULL);

        if (nfrags > LNET_MAX_IOV * max_brw)
                RETURN(NULL);

        OBD_ALLOC_PTR(desc);
        if (!desc)
                return NULL;

        OBD_ALLOC_LARGE(desc->bd_vec,
                        nfrags * sizeof(*desc->bd_vec));
        if (!desc->bd_vec)
                goto out;

        spin_lock_init(&desc->bd_lock);
        init_waitqueue_head(&desc->bd_waitq);
        desc->bd_max_iov = nfrags;
        desc->bd_iov_count = 0;
        desc->bd_portal = portal;
        desc->bd_type = type;
        desc->bd_md_count = 0;
        desc->bd_nob_last = LNET_MTU;
        desc->bd_frag_ops = ops;
        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++)
                LNetInvalidateMDHandle(&desc->bd_mds[i]);

        return desc;
out:
        OBD_FREE_PTR(desc);
        return NULL;
}

/**
 * Prepare bulk descriptor for specified outgoing request \a req that
 * can fit \a nfrags * 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,
                                              unsigned int nfrags,
                                              unsigned int max_brw,
                                              unsigned int type,
                                              unsigned int portal,
                                              const struct ptlrpc_bulk_frag_ops
                                                *ops)
{
        struct obd_import *imp = req->rq_import;
        struct ptlrpc_bulk_desc *desc;

        ENTRY;
        LASSERT(ptlrpc_is_bulk_op_passive(type));

        desc = ptlrpc_new_bulk(nfrags, max_brw, type, portal, ops);
        if (!desc)
                RETURN(NULL);

        desc->bd_import = class_import_get(imp);
        desc->bd_req = req;

        desc->bd_cbid.cbid_fn  = client_bulk_callback;
        desc->bd_cbid.cbid_arg = desc;

        /* This makes req own desc, and free it when she frees herself */
        req->rq_bulk = desc;

        return desc;
}
EXPORT_SYMBOL(ptlrpc_prep_bulk_imp);

void __ptlrpc_prep_bulk_page(struct ptlrpc_bulk_desc *desc,
                             struct page *page, int pageoffset, int len,
                             int pin)
{
        struct bio_vec *kiov;

        LASSERT(desc->bd_iov_count < desc->bd_max_iov);
        LASSERT(page != NULL);
        LASSERT(pageoffset >= 0);
        LASSERT(len > 0);
        LASSERT(pageoffset + len <= PAGE_SIZE);

        kiov = &desc->bd_vec[desc->bd_iov_count];

        if (((desc->bd_iov_count % LNET_MAX_IOV) == 0) ||
             ((desc->bd_nob_last + len) > LNET_MTU)) {
                desc->bd_mds_off[desc->bd_md_count] = desc->bd_iov_count;
                desc->bd_md_count++;
                desc->bd_nob_last = 0;
                LASSERT(desc->bd_md_count <= PTLRPC_BULK_OPS_COUNT);
        }

        desc->bd_nob_last += len;
        desc->bd_nob += len;

        if (pin)
                get_page(page);

        kiov->bv_page = page;
        kiov->bv_offset = pageoffset;
        kiov->bv_len = len;

        desc->bd_iov_count++;
}
EXPORT_SYMBOL(__ptlrpc_prep_bulk_page);

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_refs == 0);         /* network hands off */
        LASSERT((desc->bd_export != NULL) ^ (desc->bd_import != NULL));
        LASSERT(desc->bd_frag_ops != NULL);

        sptlrpc_pool_put_desc_pages(desc);

        if (desc->bd_export)
                class_export_put(desc->bd_export);
        else
                class_import_put(desc->bd_import);

        if (desc->bd_frag_ops->release_frags != NULL)
                desc->bd_frag_ops->release_frags(desc);

        OBD_FREE_LARGE(desc->bd_vec,
                       desc->bd_max_iov * sizeof(*desc->bd_vec));
        OBD_FREE_PTR(desc);
        EXIT;
}
EXPORT_SYMBOL(ptlrpc_free_bulk);

/**
 * 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)
{
        struct obd_device *obd;

        LASSERT(req->rq_import);
        obd = req->rq_import->imp_obd;

        if (obd_at_off(obd)) {
                /* 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;
        } else {
                struct imp_at *at = &req->rq_import->imp_at;
                timeout_t serv_est;
                int idx;

                idx = import_at_get_index(req->rq_import,
                                          req->rq_request_portal);
                serv_est = obd_at_get(obd, &at->iat_service_estimate[idx]);
                /*
                 * Currently a 32 bit value is sent over the
                 * wire for rq_timeout so please don't change this
                 * to time64_t. The work for LU-1158 will in time
                 * replace rq_timeout with a 64 bit nanosecond value
                 */
                req->rq_timeout = at_est2timeout(serv_est);
        }
        /*
         * We could get even fancier here, using history to predict increased
         * loading...
         *
         * Let the server know what this RPC timeout is by putting it in the
         * 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,
                                  timeout_t serv_est)
{
        int idx;
        timeout_t oldse;
        struct imp_at *at;
        struct obd_device *obd;

        LASSERT(req->rq_import);
        obd = req->rq_import->imp_obd;
        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 = obd_at_measure(obd, &at->iat_service_estimate[idx], serv_est);
        if (oldse != 0) {
                unsigned int at_est = obd_at_get(obd,
                                                &at->iat_service_estimate[idx]);
                CDEBUG(D_ADAPTTO,
                       "The RPC service estimate for %s ptl %d has changed from %d to %d\n",
                       req->rq_import->imp_obd->obd_name,
                       req->rq_request_portal,
                       oldse, at_est);
        }
}

/**
 * Returns Expected network latency per remote node (secs).
 *
 * \param[in] req       ptlrpc request
 *
 * \retval      0 if AT(Adaptive Timeout) is off
 * \retval      >0 (iat_net_latency) latency per node
 */
int ptlrpc_at_get_net_latency(struct ptlrpc_request *req)
{
        struct obd_device *obd = req->rq_import->imp_obd;

        return obd_at_off(obd) ?
               0 : obd_at_get(obd, &req->rq_import->imp_at.iat_net_latency);
}

/* Adjust expected network latency */
void ptlrpc_at_adj_net_latency(struct ptlrpc_request *req,
                               timeout_t service_timeout)
{
        time64_t now = ktime_get_real_seconds();
        struct imp_at *at;
        timeout_t oldnl;
        timeout_t nl;
        struct obd_device *obd;

        LASSERT(req->rq_import);
        obd = req->rq_import->imp_obd;

        if (service_timeout > now - req->rq_sent + 3) {
                /*
                 * b=16408, however, this can also happen if early reply
                 * is lost and client RPC is expired and resent, early reply
                 * or reply of original RPC can still be fit in reply buffer
                 * of resent RPC, now client is measuring time from the
                 * resent time, but server sent back service time of original
                 * RPC.
                 */
                CDEBUG_LIMIT((lustre_msg_get_flags(req->rq_reqmsg) &
                              MSG_RESENT) ?  D_ADAPTTO : D_WARNING,
                             "Reported service time %u > total measured time %lld\n",
                             service_timeout, now - req->rq_sent);
                return;
        }

        /* Network latency is total time less server processing time,
         * st rounding
         */
        nl = max_t(timeout_t, now - req->rq_sent - service_timeout, 0) + 1;
        at = &req->rq_import->imp_at;

        oldnl = obd_at_measure(obd, &at->iat_net_latency, nl);
        if (oldnl != 0) {
                timeout_t timeout = obd_at_get(obd, &at->iat_net_latency);

                CDEBUG(D_ADAPTTO,
                       "The network latency for %s (nid %s) has changed from %d to %d\n",
                       req->rq_import->imp_obd->obd_name,
                       obd_uuid2str(&req->rq_import->imp_connection->c_remote_uuid),
                       oldnl, timeout);
        }
}

static int unpack_reply(struct ptlrpc_request *req)
{
        int rc;

        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: rc = %d",
                                  rc);
                        return -EPROTO;
                }
        }

        rc = lustre_unpack_rep_ptlrpc_body(req, MSG_PTLRPC_BODY_OFF);
        if (rc) {
                DEBUG_REQ(D_ERROR, req, "unpack ptlrpc body failed: rc = %d",
                          rc);
                return -EPROTO;
        }
        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
 */
static int ptlrpc_at_recv_early_reply(struct ptlrpc_request *req)
__must_hold(&req->rq_lock)
{
        struct ptlrpc_request *early_req;
        timeout_t service_timeout;
        time64_t olddl;
        int rc;

        ENTRY;
        req->rq_early = 0;
        spin_unlock(&req->rq_lock);

        rc = sptlrpc_cli_unwrap_early_reply(req, &early_req);
        if (rc) {
                spin_lock(&req->rq_lock);
                RETURN(rc);
        }

        rc = unpack_reply(early_req);
        if (rc != 0) {
                sptlrpc_cli_finish_early_reply(early_req);
                spin_lock(&req->rq_lock);
                RETURN(rc);
        }

        /*
         * Use new timeout value just to adjust the local value for this
         * request, don't include it into at_history. It is unclear yet why
         * service time increased and should it be counted or skipped, e.g.
         * that can be recovery case or some error or server, the real reply
         * will add all new data if it is worth to add.
         */
        req->rq_timeout = lustre_msg_get_timeout(early_req->rq_repmsg);
        lustre_msg_set_timeout(req->rq_reqmsg, req->rq_timeout);

        /* Network latency can be adjusted, it is pure network delays */
        service_timeout = lustre_msg_get_service_timeout(early_req->rq_repmsg);
        ptlrpc_at_adj_net_latency(req, service_timeout);

        sptlrpc_cli_finish_early_reply(early_req);

        spin_lock(&req->rq_lock);
        olddl = req->rq_deadline;
        /*
         * server assumes it now has rq_timeout from when the request
         * arrived, so the client should give it at least that long.
         * since we don't know the arrival time we'll use the original
         * sent time
         */
        req->rq_deadline = req->rq_sent + req->rq_timeout +
                           ptlrpc_at_get_net_latency(req);

        /* The below message is checked in replay-single.sh test_65{a,b} */
        /* The below message is checked in sanity-{gss,krb5} test_8 */
        DEBUG_REQ(D_ADAPTTO, req,
                  "Early reply #%d, new deadline in %llds (%llds)",
                  req->rq_early_count,
                  req->rq_deadline - ktime_get_real_seconds(),
                  req->rq_deadline - olddl);

        RETURN(rc);
}

static struct kmem_cache *request_cache;

int ptlrpc_request_cache_init(void)
{
        request_cache = kmem_cache_create("ptlrpc_cache",
                                          sizeof(struct ptlrpc_request),
                                          0, SLAB_HWCACHE_ALIGN, NULL);
        return request_cache ? 0 : -ENOMEM;
}

void ptlrpc_request_cache_fini(void)
{
        kmem_cache_destroy(request_cache);
}

struct ptlrpc_request *ptlrpc_request_cache_alloc(gfp_t 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 ptlrpc_request *req;

        LASSERT(pool != NULL);

        spin_lock(&pool->prp_lock);
        while ((req = list_first_entry_or_null(&pool->prp_req_list,
                                               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_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
 */
int ptlrpc_add_rqs_to_pool(struct ptlrpc_request_pool *pool, int num_rq)
{
        int i;
        int size = 1;

        while (size < pool->prp_rq_size)
                size <<= 1;

        LASSERTF(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);

        pool->prp_rq_size = size;
        for (i = 0; i < num_rq; i++) {
                struct ptlrpc_request *req;
                struct lustre_msg *msg;

                req = ptlrpc_request_cache_alloc(GFP_NOFS);
                if (!req)
                        return i;
                OBD_ALLOC_LARGE(msg, size);
                if (!msg) {
                        ptlrpc_request_cache_free(req);
                        return i;
                }
                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 num_rq;
}
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,
                    int (*populate_pool)(struct ptlrpc_request_pool *, int))
{
        struct ptlrpc_request_pool *pool;

        OBD_ALLOC_PTR(pool);
        if (!pool)
                return NULL;

        /*
         * Request next power of two for the allocation, because internally
         * kernel would do exactly this
         */
        spin_lock_init(&pool->prp_lock);
        INIT_LIST_HEAD(&pool->prp_req_list);
        pool->prp_rq_size = msgsize + SPTLRPC_MAX_PAYLOAD;
        pool->prp_populate = populate_pool;

        populate_pool(pool, num_rq);

        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)
{
        struct ptlrpc_request *request;
        struct lustre_msg *reqbuf;

        if (!pool)
                return NULL;

        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;
        }

        request = list_first_entry(&pool->prp_req_list, struct ptlrpc_request,
                                   rq_list);
        list_del_init(&request->rq_list);
        spin_unlock(&pool->prp_lock);

        LASSERT(request->rq_reqbuf);
        LASSERT(request->rq_pool);

        reqbuf = request->rq_reqbuf;
        memset(request, 0, sizeof(*request));
        request->rq_reqbuf = reqbuf;
        request->rq_reqbuf_len = pool->prp_rq_size;
        request->rq_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;

        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);
}

void ptlrpc_add_unreplied(struct ptlrpc_request *req)
{
        struct obd_import *imp = req->rq_import;
        struct ptlrpc_request *iter;

        assert_spin_locked(&imp->imp_lock);
        LASSERT(list_empty(&req->rq_unreplied_list));

        /* unreplied list is sorted by xid in ascending order */
        list_for_each_entry_reverse(iter, &imp->imp_unreplied_list,
                                    rq_unreplied_list) {
                LASSERT(req->rq_xid != iter->rq_xid);
                if (req->rq_xid < iter->rq_xid)
                        continue;
                list_add(&req->rq_unreplied_list, &iter->rq_unreplied_list);
                return;
        }
        list_add(&req->rq_unreplied_list, &imp->imp_unreplied_list);
}

void ptlrpc_assign_next_xid_nolock(struct ptlrpc_request *req)
{
        req->rq_xid = ptlrpc_next_xid();
        ptlrpc_add_unreplied(req);
}

static inline void ptlrpc_assign_next_xid(struct ptlrpc_request *req)
{
        spin_lock(&req->rq_import->imp_lock);
        ptlrpc_assign_next_xid_nolock(req);
        spin_unlock(&req->rq_import->imp_lock);
}

static atomic64_t ptlrpc_last_xid;

static void ptlrpc_reassign_next_xid(struct ptlrpc_request *req)
{
        spin_lock(&req->rq_import->imp_lock);
        list_del_init(&req->rq_unreplied_list);
        ptlrpc_assign_next_xid_nolock(req);
        spin_unlock(&req->rq_import->imp_lock);
        DEBUG_REQ(D_RPCTRACE, req, "reassign xid");
}

void ptlrpc_get_mod_rpc_slot(struct ptlrpc_request *req)
{
        struct client_obd *cli = &req->rq_import->imp_obd->u.cli;
        __u32 opc;
        __u16 tag;

        opc = lustre_msg_get_opc(req->rq_reqmsg);
        tag = obd_get_mod_rpc_slot(cli, opc);
        lustre_msg_set_tag(req->rq_reqmsg, tag);
        ptlrpc_reassign_next_xid(req);
}
EXPORT_SYMBOL(ptlrpc_get_mod_rpc_slot);

void ptlrpc_put_mod_rpc_slot(struct ptlrpc_request *req)
{
        __u16 tag = lustre_msg_get_tag(req->rq_reqmsg);

        if (tag != 0) {
                struct client_obd *cli = &req->rq_import->imp_obd->u.cli;
                __u32 opc = lustre_msg_get_opc(req->rq_reqmsg);

                obd_put_mod_rpc_slot(cli, opc, tag);
        }
}
EXPORT_SYMBOL(ptlrpc_put_mod_rpc_slot);

int ptlrpc_request_bufs_pack(struct ptlrpc_request *request,
                             __u32 version, int opcode, char **bufs,
                             struct ptlrpc_cli_ctx *ctx)
{
        int count;
        struct obd_import *imp;
        __u32 *lengths;
        int rc;

        ENTRY;

        count = req_capsule_filled_sizes(&request->rq_pill, RCL_CLIENT);
        imp = request->rq_import;
        lengths = request->rq_pill.rc_area[RCL_CLIENT];

        if (ctx) {
                request->rq_cli_ctx = sptlrpc_cli_ctx_get(ctx);
        } else {
                rc = sptlrpc_req_get_ctx(request);
                if (rc)
                        GOTO(out_free, rc);
        }
        sptlrpc_req_set_flavor(request, opcode);

        rc = lustre_pack_request(request, imp->imp_msg_magic, count,
                                 lengths, bufs);
        if (rc)
                GOTO(out_ctx, rc);

        lustre_msg_add_version(request->rq_reqmsg, version);
        request->rq_send_state = LUSTRE_IMP_FULL;
        request->rq_type = PTL_RPC_MSG_REQUEST;

        request->rq_req_cbid.cbid_fn  = request_out_callback;
        request->rq_req_cbid.cbid_arg = request;

        request->rq_reply_cbid.cbid_fn  = reply_in_callback;
        request->rq_reply_cbid.cbid_arg = request;

        request->rq_reply_deadline = 0;
        request->rq_bulk_deadline = 0;
        request->rq_req_deadline = 0;
        request->rq_phase = RQ_PHASE_NEW;
        request->rq_next_phase = RQ_PHASE_UNDEFINED;

        request->rq_request_portal = imp->imp_client->cli_request_portal;
        request->rq_reply_portal = imp->imp_client->cli_reply_portal;

        ptlrpc_at_set_req_timeout(request);

        lustre_msg_set_opc(request->rq_reqmsg, opcode);

        /* Let's setup deadline for req/reply/bulk unlink for opcode. */
        if (cfs_fail_val == opcode) {
                time64_t *fail_t = NULL, *fail2_t = NULL;

                if (CFS_FAIL_CHECK(OBD_FAIL_PTLRPC_LONG_BULK_UNLINK)) {
                        fail_t = &request->rq_bulk_deadline;
                } else if (CFS_FAIL_CHECK(OBD_FAIL_PTLRPC_LONG_REPL_UNLINK)) {
                        fail_t = &request->rq_reply_deadline;
                } else if (CFS_FAIL_CHECK(OBD_FAIL_PTLRPC_LONG_REQ_UNLINK)) {
                        fail_t = &request->rq_req_deadline;
                } else if (CFS_FAIL_CHECK(OBD_FAIL_PTLRPC_LONG_BOTH_UNLINK)) {
                        fail_t = &request->rq_reply_deadline;
                        fail2_t = &request->rq_bulk_deadline;
                } else if (CFS_FAIL_CHECK(OBD_FAIL_PTLRPC_ROUND_XID)) {
                        time64_t now = ktime_get_real_seconds();
                        u64 xid = ((u64)now >> 4) << 24;

                        atomic64_set(&ptlrpc_last_xid, xid);
                }

                if (fail_t) {
                        *fail_t = ktime_get_real_seconds() +
                                  PTLRPC_REQ_LONG_UNLINK;

                        if (fail2_t)
                                *fail2_t = ktime_get_real_seconds() +
                                           PTLRPC_REQ_LONG_UNLINK;

                        /*
                         * The RPC is infected, let the test to change the
                         * fail_loc
                         */
                        msleep(4 * MSEC_PER_SEC);
                }
        }
        ptlrpc_assign_next_xid(request);

        RETURN(0);

out_ctx:
        LASSERT(!request->rq_pool);
        sptlrpc_cli_ctx_put(request->rq_cli_ctx, 1);
out_free:
        atomic_dec(&imp->imp_reqs);
        class_import_put(imp);

        return rc;
}
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);
}
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;

        request = ptlrpc_request_cache_alloc(GFP_NOFS);

        if (!request && pool)
                request = ptlrpc_prep_req_from_pool(pool);

        if (request) {
                ptlrpc_cli_req_init(request);

                LASSERTF((unsigned long)imp > 0x1000, "%px\n", imp);
                LASSERT(imp != LP_POISON);
                LASSERTF((unsigned long)imp->imp_client > 0x1000, "%px\n",
                         imp->imp_client);
                LASSERT(imp->imp_client != LP_POISON);

                request->rq_import = class_import_get(imp);
                atomic_inc(&imp->imp_reqs);
        } else {
                CERROR("request allocation out of memory\n");
        }

        return request;
}

static int ptlrpc_reconnect_if_idle(struct obd_import *imp)
{
        int rc;

        /*
         * initiate connection if needed when the import has been
         * referenced by the new request to avoid races with disconnect.
         * serialize this check against conditional state=IDLE
         * in ptlrpc_disconnect_idle_interpret()
         */
        spin_lock(&imp->imp_lock);
        if (imp->imp_state == LUSTRE_IMP_IDLE) {
                imp->imp_generation++;
                imp->imp_initiated_at = imp->imp_generation;
                imp->imp_state = LUSTRE_IMP_NEW;

                /* connect_import_locked releases imp_lock */
                rc = ptlrpc_connect_import_locked(imp);
                if (rc)
                        return rc;
                ptlrpc_pinger_add_import(imp);
        } else {
                spin_unlock(&imp->imp_lock);
        }
        return 0;
}

/**
 * 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,
                              const struct req_format *format)
{
        struct ptlrpc_request *request;

        request = __ptlrpc_request_alloc(imp, pool);
        if (!request)
                return NULL;

        /* don't make expensive check for idling connection
         * if it's already connected */
        if (unlikely(imp->imp_state != LUSTRE_IMP_FULL)) {
                if (ptlrpc_reconnect_if_idle(imp) < 0) {
                        atomic_dec(&imp->imp_reqs);
                        ptlrpc_request_free(request);
                        return NULL;
                }
        }

        req_capsule_init(&request->rq_pill, request, RCL_CLIENT);
        req_capsule_set(&request->rq_pill, format);
        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
                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)
{
        struct ptlrpc_request *req = ptlrpc_request_alloc(imp, format);
        int rc;

        if (req) {
                rc = ptlrpc_request_pack(req, version, opcode);
                if (rc) {
                        ptlrpc_request_free(req);
                        req = NULL;
                }
        }
        return req;
}
EXPORT_SYMBOL(ptlrpc_request_alloc_pack);

/**
 * Allocate and initialize new request set structure on the current CPT.
 * 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;
        int cpt;

        ENTRY;
        cpt = cfs_cpt_current(cfs_cpt_tab, 0);
        OBD_CPT_ALLOC(set, cfs_cpt_tab, cpt, sizeof(*set));
        if (!set)
                RETURN(NULL);
        atomic_set(&set->set_refcount, 1);
        INIT_LIST_HEAD(&set->set_requests);
        init_waitqueue_head(&set->set_waitq);
        atomic_set(&set->set_new_count, 0);
        atomic_set(&set->set_remaining, 0);
        spin_lock_init(&set->set_new_req_lock);
        INIT_LIST_HEAD(&set->set_new_requests);
        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);

/**
 * 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);

        set->set_max_inflight  = max;
        set->set_producer      = func;
        set->set_producer_arg  = arg;

        RETURN(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 ptlrpc_request *req;
        int expected_phase;
        int n = 0;

        ENTRY;

        /* Requests on the set should either all be completed, or all be new */
        expected_phase = (atomic_read(&set->set_remaining) == 0) ?
                         RQ_PHASE_COMPLETE : RQ_PHASE_NEW;
        list_for_each_entry(req, &set->set_requests, rq_set_chain) {
                LASSERT(req->rq_phase == expected_phase);
                n++;
        }

        LASSERTF(atomic_read(&set->set_remaining) == 0 ||
                 atomic_read(&set->set_remaining) == n, "%d / %d\n",
                 atomic_read(&set->set_remaining), n);

        while ((req = list_first_entry_or_null(&set->set_requests,
                                               struct ptlrpc_request,
                                               rq_set_chain))) {
                list_del_init(&req->rq_set_chain);

                LASSERT(req->rq_phase == expected_phase);

                if (req->rq_phase == RQ_PHASE_NEW) {
                        ptlrpc_req_interpret(NULL, req, -EBADR);
                        atomic_dec(&set->set_remaining);
                }

                spin_lock(&req->rq_lock);
                req->rq_set = NULL;
                req->rq_invalid_rqset = 0;
                spin_unlock(&req->rq_lock);

                ptlrpc_req_finished(req);
        }

        LASSERT(atomic_read(&set->set_remaining) == 0);

        ptlrpc_reqset_put(set);
        EXIT;
}
EXPORT_SYMBOL(ptlrpc_set_destroy);

/**
 * 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)
{
        if (set == PTLRPCD_SET) {
                ptlrpcd_add_req(req);
                return;
        }

        LASSERT(req->rq_import->imp_state != LUSTRE_IMP_IDLE);
        LASSERT(list_empty(&req->rq_set_chain));

        if (req->rq_allow_intr)
                set->set_allow_intr = 1;

        /* The set takes over the caller's request reference */
        list_add_tail(&req->rq_set_chain, &set->set_requests);
        req->rq_set = set;
        atomic_inc(&set->set_remaining);
        req->rq_queued_time = ktime_get_seconds();

        if (req->rq_reqmsg) {
                lustre_msg_set_jobid(req->rq_reqmsg, NULL);
                lustre_msg_set_uid_gid(req->rq_reqmsg, NULL, NULL);
        }

        if (set->set_producer)
                /*
                 * 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);

/**
 * Add a request to a request with dedicated server thread
 * and wake the thread to make any necessary processing.
 * Currently only used for ptlrpcd.
 */
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;

        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 = ktime_get_seconds();
        list_add_tail(&req->rq_set_chain, &set->set_new_requests);
        count = 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);
        }
}

/**
 * Based on the current state of the import, determine if the request
 * can be sent, is an error, or should be delayed.
 *
 * Returns true if this request should be delayed. If false, and
 * *status is set, then the request can not be sent and *status is the
 * error code.  If false and status is 0, then request can be sent.
 *
 * The imp->imp_lock must be held.
 */
static int ptlrpc_import_delay_req(struct obd_import *imp,
                                   struct ptlrpc_request *req, int *status)
{
        int delay = 0;

        ENTRY;
        LASSERT(status);
        *status = 0;

        if (req->rq_ctx_init || req->rq_ctx_fini) {
                /* always allow ctx init/fini rpc go through */
        } else if (imp->imp_state == LUSTRE_IMP_NEW) {
                DEBUG_REQ(D_ERROR, req, "Uninitialized import");
                *status = -EIO;
        } else if (imp->imp_state == LUSTRE_IMP_CLOSED) {
                unsigned int opc = lustre_msg_get_opc(req->rq_reqmsg);

                /*
                 * pings or MDS-equivalent STATFS may safely
                 * race with umount
                 */
                DEBUG_REQ((opc == OBD_PING || opc == OST_STATFS) ?
                          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 afterinitial testing */
                DEBUG_REQ(D_HA, req, "send limit expired");
                *status = -ETIMEDOUT;
        } 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) {
                        DEBUG_REQ(D_ERROR, req, "invalidate in flight");
                        *status = -EIO;
                }
        } else if (imp->imp_invalid || imp->imp_obd->obd_no_recov) {
                if (!imp->imp_deactive)
                        DEBUG_REQ(D_NET, req, "IMP_INVALID");
                *status = -ESHUTDOWN; /* b=12940 */
        } else if (req->rq_import_generation != imp->imp_generation) {
                DEBUG_REQ(req->rq_no_resend ? D_INFO : 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) {
                        DEBUG_REQ(D_ERROR, req, "invalidate in flight");
                        *status = -EIO;
                } else if (req->rq_no_delay &&
                           imp->imp_generation != imp->imp_initiated_at) {
                        /* ignore nodelay for requests initiating connections */
                        *status = -EAGAIN;
                } 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");
                } else {
                        delay = 1;
                }
        }

        RETURN(delay);
}

/**
 * Decide if the error message should be printed to the console or not.
 * Makes its decision based on request type, status, and failure frequency.
 *
 * \param[in] req  request that failed and may need a console message
 *
 * \retval false if no message should be printed
 * \retval true  if console message should be printed
 */
static bool ptlrpc_console_allow(struct ptlrpc_request *req, __u32 opc, int err)
{
        LASSERT(req->rq_reqmsg != NULL);

        /* Suppress particular reconnect errors which are to be expected. */
        if (opc == OST_CONNECT || opc == OST_DISCONNECT ||
            opc == MDS_CONNECT || opc == MDS_DISCONNECT ||
            opc == MGS_CONNECT || opc == MGS_DISCONNECT) {
                /* Suppress timed out reconnect/disconnect requests */
                if (lustre_handle_is_used(&req->rq_import->imp_remote_handle) ||
                    req->rq_timedout)
                        return false;

                /*
                 * Suppress most unavailable/again reconnect requests, but
                 * print occasionally so it is clear client is trying to
                 * connect to a server where no target is running.
                 */
                if ((err == -ENODEV || err == -EAGAIN) &&
                    req->rq_import->imp_conn_cnt % 30 != 20)
                        return false;
        }

        if (opc == LDLM_ENQUEUE && err == -EAGAIN)
                /* -EAGAIN is normal when using POSIX flocks */
                return false;

        if (opc == OBD_PING && (err == -ENODEV || err == -ENOTCONN) &&
            (req->rq_xid & 0xf) != 10)
                /* Suppress most ping requests, they may fail occasionally */
                return false;

        return true;
}

/**
 * Check request processing status.
 * Returns the status.
 */
static int ptlrpc_check_status(struct ptlrpc_request *req)
{
        int rc;

        ENTRY;
        rc = 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;
                struct lnet_nid *nid = &imp->imp_connection->c_peer.nid;
                __u32 opc = lustre_msg_get_opc(req->rq_reqmsg);

                if (ptlrpc_console_allow(req, opc, rc))
                        LCONSOLE_ERROR_MSG(0x11,
                                           "%s: operation %s to node %s failed: rc = %d\n",
                                           imp->imp_obd->obd_name,
                                           ll_opcode2str(opc),
                                           libcfs_nidstr(nid), rc);
                RETURN(rc < 0 ? rc : -EINVAL);
        }

        if (rc)
                DEBUG_REQ(D_INFO, req, "check status: rc = %d", rc);

        RETURN(rc);
}

/**
 * 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 [%#llx/%#llx]\n",
               versions[0], versions[1]);

        EXIT;
}

__u64 ptlrpc_known_replied_xid(struct obd_import *imp)
{
        struct ptlrpc_request *req;

        assert_spin_locked(&imp->imp_lock);
        if (list_empty(&imp->imp_unreplied_list))
                return 0;

        req = list_first_entry(&imp->imp_unreplied_list, struct ptlrpc_request,
                               rq_unreplied_list);
        LASSERTF(req->rq_xid >= 1, "XID:%llu\n", req->rq_xid);

        if (imp->imp_known_replied_xid < req->rq_xid - 1)
                imp->imp_known_replied_xid = req->rq_xid - 1;

        return req->rq_xid - 1;
}

/**
 * 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)
{
        struct obd_import *imp = req->rq_import;
        struct obd_device *obd = req->rq_import->imp_obd;
        ktime_t work_start;
        u64 committed;
        s64 timediff;
        int rc;

        ENTRY;
        LASSERT(obd != NULL);
        /* repbuf must be unlinked */
        LASSERT(!req->rq_receiving_reply && req->rq_reply_unlinked);

        if (req->rq_reply_truncated) {
                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);
        }

        work_start = ktime_get_real();
        timediff = ktime_us_delta(work_start, req->rq_sent_ns);

        /*
         * 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: rc = %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);

        /* retry indefinitely on EINPROGRESS */
        if (lustre_msg_get_status(req->rq_repmsg) == -EINPROGRESS &&
            ptlrpc_no_resend(req) == 0 && !req->rq_no_retry_einprogress) {
                time64_t now = ktime_get_real_seconds();

                DEBUG_REQ((req->rq_nr_resend % 8 == 1 ? D_WARNING : 0) |
                          D_RPCTRACE, req, "resending request on EINPROGRESS");
                spin_lock(&req->rq_lock);
                req->rq_resend = 1;
                spin_unlock(&req->rq_lock);
                req->rq_nr_resend++;

                /* 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;

                /* Resend for EINPROGRESS will use a new XID */
                spin_lock(&imp->imp_lock);
                list_del_init(&req->rq_unreplied_list);
                spin_unlock(&imp->imp_lock);

                RETURN(0);
        }

        if (obd->obd_svc_stats) {
                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) {
                DEBUG_REQ(D_ERROR, req, "invalid packet received (type=%u)",
                          lustre_msg_get_type(req->rq_repmsg));
                RETURN(-EPROTO);
        }

        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_timeout(req->rq_repmsg));

        rc = ptlrpc_check_status(req);

        if (rc) {
                /*
                 * Either we've been evicted, or the server has failed for
                 * some reason. Try to reconnect, and if that fails, punt to
                 * the upcall.
                 */
                if (ptlrpc_recoverable_error(rc)) {
                        if (req->rq_send_state != LUSTRE_IMP_FULL ||
                            imp->imp_obd->obd_no_recov || imp->imp_dlm_fake) {
                                RETURN(rc);
                        }
                        ptlrpc_request_handle_notconn(req);
                        RETURN(rc);
                }
        } else {
                /*
                 * Let's look if server sent slv. Do it only for RPC with
                 * rc == 0.
                 */
                ldlm_cli_update_pool(req);
        }

        /*
         * Store transno in reqmsg for replay.
         */
        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 (lustre_msg_get_transno(req->rq_repmsg) ||
            lustre_msg_get_opc(req->rq_reqmsg) == LDLM_ENQUEUE)
                imp->imp_no_cached_data = 0;

        if (imp->imp_replayable) {
                /* if other threads are waiting for ptlrpc_free_committed()
                 * they could continue the work of freeing RPCs. That reduces
                 * lock hold times, and distributes work more fairly across
                 * waiting threads.  We can't use spin_is_contended() since
                 * there are many other places where imp_lock is held.
                 */
                atomic_inc(&imp->imp_waiting);
                spin_lock(&imp->imp_lock);
                atomic_dec(&imp->imp_waiting);
                /*
                 * No point in adding already-committed requests to the replay
                 * list, we will just remove them immediately. b=9829
                 */
                if (req->rq_transno != 0 &&
                    (req->rq_transno >
                     lustre_msg_get_last_committed(req->rq_repmsg) ||
                     req->rq_replay)) {
                        /** version recovery */
                        ptlrpc_save_versions(req);
                        ptlrpc_retain_replayable_request(req, imp);
                } else if (req->rq_commit_cb &&
                           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);
                        atomic_inc(&imp->imp_waiting);
                        spin_lock(&imp->imp_lock);
                        atomic_dec(&imp->imp_waiting);
                }

                /*
                 * Replay-enabled imports return commit-status information.
                 */
                committed = lustre_msg_get_last_committed(req->rq_repmsg);
                if (likely(committed > imp->imp_peer_committed_transno))
                        imp->imp_peer_committed_transno = committed;

                ptlrpc_free_committed(imp);

                if (!list_empty(&imp->imp_replay_list)) {
                        struct ptlrpc_request *last;

                        last = 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 = req->rq_import;
        __u64 min_xid = 0;
        int rc;

        ENTRY;
        LASSERT(req->rq_phase == RQ_PHASE_NEW);

        /* do not try to go further if there is not enough memory in pool */
        if (req->rq_sent && req->rq_bulk)
                if (req->rq_bulk->bd_iov_count >
                    sptlrpc_pool_get_free_pages(0) &&
                    pool_is_at_full_capacity(0))
                        RETURN(-ENOMEM);

        if (req->rq_sent && (req->rq_sent > ktime_get_real_seconds()) &&
            (!req->rq_generation_set ||
             req->rq_import_generation == imp->imp_generation))
                RETURN(0);

        ptlrpc_rqphase_move(req, RQ_PHASE_RPC);

        spin_lock(&imp->imp_lock);

        LASSERT(req->rq_xid != 0);
        LASSERT(!list_empty(&req->rq_unreplied_list));

        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 waiting for recovery: (%s != %s)",
                          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);

        /*
         * find the known replied XID from the unreplied list, CONNECT
         * and DISCONNECT requests are skipped to make the sanity check
         * on server side happy. see process_req_last_xid().
         *
         * For CONNECT: Because replay requests have lower XID, it'll
         * break the sanity check if CONNECT bump the exp_last_xid on
         * server.
         *
         * For DISCONNECT: Since client will abort inflight RPC before
         * sending DISCONNECT, DISCONNECT may carry an XID which higher
         * than the inflight RPC.
         */
        if (!ptlrpc_req_is_connect(req) && !ptlrpc_req_is_disconnect(req))
                min_xid = ptlrpc_known_replied_xid(imp);
        spin_unlock(&imp->imp_lock);

        lustre_msg_set_last_xid(req->rq_reqmsg, min_xid);

        lustre_msg_set_status(req->rq_reqmsg, current->pid);

        /* If the request to be sent is an LDLM callback, do not try to
         * refresh context.
         * An LDLM callback is sent by a server to a client in order to make
         * it release a lock, on a communication channel that uses a reverse
         * context. It cannot be refreshed on its own, as it is the 'reverse'
         * (server-side) representation of a client context.
         * We do not care if the reverse context is expired, and want to send
         * the LDLM callback anyway. Once the client receives the AST, it is
         * its job to refresh its own context if it has expired, hence
         * refreshing the associated reverse context on server side, before
         * being able to send the LDLM_CANCEL requested by the server.
         */
        if (lustre_msg_get_opc(req->rq_reqmsg) != LDLM_BL_CALLBACK &&
            lustre_msg_get_opc(req->rq_reqmsg) != LDLM_CP_CALLBACK &&
            lustre_msg_get_opc(req->rq_reqmsg) != LDLM_GL_CALLBACK)
                rc = sptlrpc_req_refresh_ctx(req, 0);
        if (rc) {
                if (req->rq_err) {
                        req->rq_status = rc;
                        RETURN(1);
                } else {
                        spin_lock(&req->rq_lock);
                        req->rq_wait_ctx = 1;
                        spin_unlock(&req->rq_lock);
                        RETURN(0);
                }
        }

        CDEBUG(D_RPCTRACE,
               "Sending RPC req@%p pname:cluuid:pid:xid:nid:opc:job %s:%s:%d:%llu:%s:%d:%s\n",
               req, current->comm,
               imp->imp_obd->obd_uuid.uuid,
               lustre_msg_get_status(req->rq_reqmsg), req->rq_xid,
               obd_import_nid2str(imp), lustre_msg_get_opc(req->rq_reqmsg),
               lustre_msg_get_jobid(req->rq_reqmsg) ?: "");

        rc = ptl_send_rpc(req, 0);
        if (rc == -ENOMEM) {
                spin_lock(&imp->imp_lock);
                if (!list_empty(&req->rq_list)) {
                        list_del_init(&req->rq_list);
                        if (atomic_dec_and_test(&req->rq_import->imp_inflight))
                                wake_up(&req->rq_import->imp_recovery_waitq);
                }
                spin_unlock(&imp->imp_lock);
                ptlrpc_rqphase_move(req, RQ_PHASE_NEW);
                RETURN(rc);
        }
        if (rc) {
                DEBUG_REQ(D_HA, req, "send failed, expect timeout: rc = %d",
                          rc);
                spin_lock(&req->rq_lock);
                req->rq_net_err = 1;
                spin_unlock(&req->rq_lock);
                RETURN(rc);
        }
        RETURN(0);
}

static inline int ptlrpc_set_producer(struct ptlrpc_request_set *set)
{
        int remaining, rc;

        ENTRY;
        LASSERT(set->set_producer != NULL);

        remaining = 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 (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((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)
 *
 * NOTE: This function contains a potential schedule point (cond_resched()).
 */
int ptlrpc_check_set(const struct lu_env *env, struct ptlrpc_request_set *set)
{
        struct ptlrpc_request *req, *next;
        LIST_HEAD(comp_reqs);
        int force_timer_recalc = 0;

        ENTRY;
        if (atomic_read(&set->set_remaining) == 0)
                RETURN(1);

        list_for_each_entry_safe(req, next, &set->set_requests,
                                 rq_set_chain) {
                struct obd_import *imp = req->rq_import;
                int unregistered = 0;
                int async = 1;
                int rc = 0;

                if (req->rq_phase == RQ_PHASE_COMPLETE) {
                        list_move_tail(&req->rq_set_chain, &comp_reqs);
                        continue;
                }

                /*
                 * This schedule point is mainly for the ptlrpcd caller of this
                 * function.  Most ptlrpc sets are not long-lived and unbounded
                 * in length, but at the least the set used by the ptlrpcd is.
                 * Since the processing time is unbounded, we need to insert an
                 * explicit schedule point to make the thread well-behaved.
                 */
                cond_resched();

                /*
                 * If the caller requires to allow to be interpreted by force
                 * and it has really been interpreted, then move the request
                 * to RQ_PHASE_INTERPRET phase in spite of what the current
                 * phase is.
                 */
                if (unlikely(req->rq_allow_intr && req->rq_intr)) {
                        req->rq_status = -EINTR;
                        ptlrpc_rqphase_move(req, RQ_PHASE_INTERPRET);

                        /*
                         * Since it is interpreted and we have to wait for
                         * the reply to be unlinked, then use sync mode.
                         */
                        async = 0;

                        GOTO(interpret, req->rq_status);
                }

                if (req->rq_phase == RQ_PHASE_NEW && ptlrpc_send_new_req(req))
                        force_timer_recalc = 1;

                /* delayed send - skip */
                if (req->rq_phase == RQ_PHASE_NEW && req->rq_sent)
                        continue;

                /* delayed resend - skip */
                if (req->rq_phase == RQ_PHASE_RPC && req->rq_resend &&
                    req->rq_sent > ktime_get_real_seconds())
                        continue;

                if (!(req->rq_phase == RQ_PHASE_RPC ||
                      req->rq_phase == RQ_PHASE_BULK ||
                      req->rq_phase == RQ_PHASE_INTERPRET ||
                      req->rq_phase == RQ_PHASE_UNREG_RPC ||
                      req->rq_phase == RQ_PHASE_UNREG_BULK)) {
                        DEBUG_REQ(D_ERROR, req, "bad phase %x", req->rq_phase);
                        LBUG();
                }

                if (req->rq_phase == RQ_PHASE_UNREG_RPC ||
                    req->rq_phase == RQ_PHASE_UNREG_BULK) {
                        LASSERT(req->rq_next_phase != req->rq_phase);
                        LASSERT(req->rq_next_phase != RQ_PHASE_UNDEFINED);

                        if (req->rq_req_deadline &&
                            !CFS_FAIL_CHECK(OBD_FAIL_PTLRPC_LONG_REQ_UNLINK))
                                req->rq_req_deadline = 0;
                        if (req->rq_reply_deadline &&
                            !CFS_FAIL_CHECK(OBD_FAIL_PTLRPC_LONG_REPL_UNLINK))
                                req->rq_reply_deadline = 0;
                        if (req->rq_bulk_deadline &&
                            !CFS_FAIL_CHECK(OBD_FAIL_PTLRPC_LONG_BULK_UNLINK))
                                req->rq_bulk_deadline = 0;

                        /*
                         * 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.
                         */
                        if (req->rq_phase == RQ_PHASE_UNREG_RPC &&
                            ptlrpc_cli_wait_unlink(req))
                                continue;
                        if (req->rq_phase == RQ_PHASE_UNREG_BULK &&
                            ptlrpc_client_bulk_active(req))
                                continue;

                        /*
                         * Turn fail_loc off to prevent it from looping
                         * forever.
                         */
                        if (CFS_FAIL_CHECK(OBD_FAIL_PTLRPC_LONG_REPL_UNLINK)) {
                                CFS_FAIL_CHECK_ORSET(OBD_FAIL_PTLRPC_LONG_REPL_UNLINK,
                                                     CFS_FAIL_ONCE);
                        }
                        if (CFS_FAIL_CHECK(OBD_FAIL_PTLRPC_LONG_BULK_UNLINK)) {
                                CFS_FAIL_CHECK_ORSET(OBD_FAIL_PTLRPC_LONG_BULK_UNLINK,
                                                     CFS_FAIL_ONCE);
                        }

                        /*
                         * Move to next phase if reply was successfully
                         * unlinked.
                         */
                        ptlrpc_rqphase_move(req, req->rq_next_phase);
                }

                if (req->rq_phase == RQ_PHASE_INTERPRET)
                        GOTO(interpret, req->rq_status);

                /*
                 * 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.
                         */
                        if (ptlrpc_cli_wait_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) {
                        if (!ptlrpc_unregister_reply(req, 1)) {
                                ptlrpc_unregister_bulk(req, 1);
                                continue;
                        }

                        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_set_wait uses l_wait_event_abortable_timeout()
                 * 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;
                        ptlrpc_rqphase_move(req, RQ_PHASE_INTERPRET);
                        GOTO(interpret, req->rq_status);
                }

                if (req->rq_phase == RQ_PHASE_RPC) {
                        if (req->rq_timedout || req->rq_resend ||
                            req->rq_waiting || req->rq_wait_ctx) {
                                int status;

                                if (!ptlrpc_unregister_reply(req, 1)) {
                                        ptlrpc_unregister_bulk(req, 1);
                                        continue;
                                }

                                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
                                         */
                                        list_move_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,
                                                            RQ_PHASE_INTERPRET);
                                        spin_unlock(&imp->imp_lock);
                                        GOTO(interpret, req->rq_status);
                                }
                                /* ignore on just initiated connections */
                                if (ptlrpc_no_resend(req) &&
                                    !req->rq_wait_ctx &&
                                    imp->imp_generation !=
                                    imp->imp_initiated_at) {
                                        req->rq_status = -ENOTCONN;
                                        ptlrpc_rqphase_move(req,
                                                            RQ_PHASE_INTERPRET);
                                        spin_unlock(&imp->imp_lock);
                                        GOTO(interpret, req->rq_status);
                                }

                                /* don't resend too fast in case of network
                                 * errors.
                                 */
                                if (ktime_get_real_seconds() < (req->rq_sent + 1)
                                    && req->rq_net_err && req->rq_timedout) {

                                        DEBUG_REQ(D_INFO, req,
                                                  "throttle request");
                                        /* Don't try to resend RPC right away
                                         * as it is likely it will fail again
                                         * and ptlrpc_check_set() will be
                                         * called again, keeping this thread
                                         * busy. Instead, wait for the next
                                         * timeout. Flag it as resend to
                                         * ensure we don't wait to long.
                                         */
                                        req->rq_resend = 1;
                                        spin_unlock(&imp->imp_lock);
                                        continue;
                                }

                                list_move_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);
                                }
                                /*
                                 * rq_wait_ctx is only touched by ptlrpcd,
                                 * so no lock is needed here.
                                 */
                                status = sptlrpc_req_refresh_ctx(req, 0);
                                if (status) {
                                        if (req->rq_err) {
                                                req->rq_status = status;
                                                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);
                                }

                                /*
                                 * In any case, the previous bulk should be
                                 * cleaned up to prepare for the new sending
                                 */
                                if (req->rq_bulk &&
                                    !ptlrpc_unregister_bulk(req, 1))
                                        continue;

                                rc = ptl_send_rpc(req, 0);
                                if (rc == -ENOMEM) {
                                        spin_lock(&imp->imp_lock);
                                        if (!list_empty(&req->rq_list)) {
                                                list_del_init(&req->rq_list);
                                                if (atomic_dec_and_test(&imp->imp_inflight))
                                                        wake_up(&imp->imp_recovery_waitq);
                                        }
                                        spin_unlock(&imp->imp_lock);
                                        ptlrpc_rqphase_move(req, RQ_PHASE_NEW);
                                        continue;
                                }
                                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;

                        req->rq_status = after_reply(req);
                        if (req->rq_resend) {
                                force_timer_recalc = 1;
                                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 || req->rq_status < 0) {
                                ptlrpc_rqphase_move(req, RQ_PHASE_INTERPRET);
                                GOTO(interpret, req->rq_status);
                        }

                        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_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 %d/%d/%d",
                                  req->rq_status,
                                  req->rq_bulk->bd_nob,
                                  req->rq_bulk->bd_nob_transferred);
                        req->rq_status = -EIO;
                }

                ptlrpc_rqphase_move(req, RQ_PHASE_INTERPRET);

interpret:
                LASSERT(req->rq_phase == RQ_PHASE_INTERPRET);

                /*
                 * This moves to "unregistering" phase we need to wait for
                 * reply unlink.
                 */
                if (!unregistered && !ptlrpc_unregister_reply(req, async)) {
                        /* start async bulk unlink too */
                        ptlrpc_unregister_bulk(req, 1);
                        continue;
                }

                if (!ptlrpc_unregister_bulk(req, async))
                        continue;

                /*
                 * When calling interpret receiving already should be
                 * finished.
                 */
                LASSERT(!req->rq_receiving_reply);

                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);

                if (req->rq_reqmsg)
                        CDEBUG(D_RPCTRACE,
                               "Completed RPC req@%p pname:cluuid:pid:xid:nid:opc:job %s:%s:%d:%llu:%s:%d:%s\n",
                               req, current->comm,
                               imp->imp_obd->obd_uuid.uuid,
                               lustre_msg_get_status(req->rq_reqmsg),
                               req->rq_xid,
                               obd_import_nid2str(imp),
                               lustre_msg_get_opc(req->rq_reqmsg),
                               lustre_msg_get_jobid(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 (!list_empty(&req->rq_list)) {
                        list_del_init(&req->rq_list);
                        if (atomic_dec_and_test(&imp->imp_inflight))
                                wake_up(&imp->imp_recovery_waitq);
                }
                list_del_init(&req->rq_unreplied_list);
                spin_unlock(&imp->imp_lock);

                atomic_dec(&set->set_remaining);
                wake_up(&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
                         */
                        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);
                } else {
                        list_move_tail(&req->rq_set_chain, &comp_reqs);
                }
        }

        /*
         * move completed request at the head of list so it's easier for
         * caller to find them
         */
        list_splice(&comp_reqs, &set->set_requests);

        /* If we hit an error, we want to recover promptly. */
        RETURN(atomic_read(&set->set_remaining) == 0 || force_timer_recalc);
}
EXPORT_SYMBOL(ptlrpc_check_set);

/**
 * 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;
        unsigned int debug_mask = D_RPCTRACE;
        int rc = 0;
        __u32 opc;

        ENTRY;
        spin_lock(&req->rq_lock);
        req->rq_timedout = 1;
        spin_unlock(&req->rq_lock);

        opc = lustre_msg_get_opc(req->rq_reqmsg);
        if (ptlrpc_console_allow(req, opc,
                                 lustre_msg_get_status(req->rq_reqmsg)))
                debug_mask = D_WARNING;
        DEBUG_REQ(debug_mask, req, "Request sent has %s: [sent %lld/real %lld]",
                  req->rq_net_err ? "failed due to network error" :
                     ((req->rq_real_sent == 0 ||
                       req->rq_real_sent < req->rq_sent ||
                       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 && obd_debug_peer_on_timeout)
                LNetDebugPeer(&imp->imp_connection->c_peer);

        ptlrpc_unregister_reply(req, async_unlink);
        ptlrpc_unregister_bulk(req, async_unlink);

        if (obd_dump_on_timeout)
                libcfs_debug_dumplog();

        if (!imp) {
                DEBUG_REQ(D_HA, req, "NULL import: already cleaned up?");
                RETURN(1);
        }

        atomic_inc(&imp->imp_timeouts);

        /* The DLM server doesn't want recovery run on its imports. */
        if (imp->imp_dlm_fake)
                RETURN(1);

        /*
         * If this request is for recovery or other primordial tasks,
         * then error it out here.
         */
        if (req->rq_ctx_init || req->rq_ctx_fini ||
            req->rq_send_state != LUSTRE_IMP_FULL ||
            imp->imp_obd->obd_no_recov) {
                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);
        }

        /*
         * if a request can't be resent we can't wait for an answer after
         * the timeout
         */
        if (ptlrpc_no_resend(req)) {
                DEBUG_REQ(D_RPCTRACE, req, "TIMEOUT-NORESEND:");
                rc = 1;
        }

        if (opc != OBD_PING || req->rq_xid > imp->imp_highest_replied_xid)
                ptlrpc_fail_import(imp,
                                   lustre_msg_get_conn_cnt(req->rq_reqmsg));

        RETURN(rc);
}

/**
 * Time out all uncompleted requests in request set pointed by \a data
 * This is called when a wait times out.
 */
void ptlrpc_expired_set(struct ptlrpc_request_set *set)
{
        struct ptlrpc_request *req;
        time64_t now = ktime_get_real_seconds();

        ENTRY;
        LASSERT(set != NULL);

        /*
         * A timeout expired. See which reqs it applies to...
         */
        list_for_each_entry(req, &set->set_requests, rq_set_chain) {
                /* don't expire request waiting for context */
                if (req->rq_wait_ctx)
                        continue;

                /* Request in-flight? */
                if (!((req->rq_phase == RQ_PHASE_RPC &&
                       !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;

                /*
                 * Deal with this guy. Do it asynchronously to not block
                 * ptlrpcd thread.
                 */
                ptlrpc_expire_one_request(req, 1);
                /*
                 * Loops require that we resched once in a while to avoid
                 * RCU stalls and a few other problems.
                 */
                cond_resched();

        }
}

/**
 * Interrupts (sets interrupted flag) all uncompleted requests in
 * a set \a data. This is called when a wait_event is interrupted
 * by a signal.
 */
static void ptlrpc_interrupted_set(struct ptlrpc_request_set *set)
{
        struct ptlrpc_request *req;

        LASSERT(set != NULL);
        CDEBUG(D_RPCTRACE, "INTERRUPTED SET %p\n", set);

        list_for_each_entry(req, &set->set_requests, rq_set_chain) {
                if (req->rq_intr)
                        continue;

                if (req->rq_phase != RQ_PHASE_RPC &&
                    req->rq_phase != RQ_PHASE_UNREG_RPC &&
                    !req->rq_allow_intr)
                        continue;

                spin_lock(&req->rq_lock);
                req->rq_intr = 1;
                spin_unlock(&req->rq_lock);
        }
}

/**
 * Get the smallest timeout in the set; this does NOT set a timeout.
 */
time64_t ptlrpc_set_next_timeout(struct ptlrpc_request_set *set)
{
        time64_t now = ktime_get_real_seconds();
        int timeout = 0;
        struct ptlrpc_request *req;
        time64_t deadline;

        ENTRY;
        list_for_each_entry(req, &set->set_requests, rq_set_chain) {
                /* 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. */
                if (req->rq_timedout)
                        continue;

                /* 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;

                if (deadline <= now)    /* actually expired already */
                        timeout = 1;    /* ASAP */
                else if (timeout == 0 || timeout > deadline - now)
                        timeout = deadline - now;
        }
        RETURN(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(const struct lu_env *env, struct ptlrpc_request_set *set)
{
        struct ptlrpc_request *req;
        time64_t timeout;
        int rc;

        ENTRY;
        if (set->set_producer)
                (void)ptlrpc_set_producer(set);
        else
                list_for_each_entry(req, &set->set_requests, rq_set_chain) {
                        if (req->rq_phase == RQ_PHASE_NEW)
                                (void)ptlrpc_send_new_req(req);
                }

        if (list_empty(&set->set_requests))
                RETURN(0);

        do {
                timeout = ptlrpc_set_next_timeout(set);

                /*
                 * wait until all complete, interrupted, or an in-flight
                 * req times out
                 */
                CDEBUG(D_RPCTRACE, "set %p going to sleep for %lld seconds\n",
                       set, timeout);

                if ((timeout == 0 && !signal_pending(current)) ||
                    set->set_allow_intr) {
                        /*
                         * 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.
                         */
                        rc = l_wait_event_abortable_timeout(
                                set->set_waitq,
                                ptlrpc_check_set(NULL, set),
                                cfs_time_seconds(timeout ? timeout : 1));
                        if (rc == 0) {
                                rc = -ETIMEDOUT;
                                ptlrpc_expired_set(set);
                        } else if (rc < 0) {
                                rc = -EINTR;
                                ptlrpc_interrupted_set(set);
                        } else {
                                rc = 0;
                        }
                } else {
                        /*
                         * At least one request is in flight, so no
                         * interrupts are allowed. Wait until all
                         * complete, or an in-flight req times out.
                         */
                        rc = wait_event_idle_timeout(
                                set->set_waitq,
                                ptlrpc_check_set(NULL, set),
                                cfs_time_seconds(timeout ? timeout : 1));
                        if (rc == 0) {
                                ptlrpc_expired_set(set);
                                rc = -ETIMEDOUT;
                        } else {
                                rc = 0;
                        }

                        /*
                         * 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 &&
                            signal_pending(current)) {
                                sigset_t old, new;

                                siginitset(&new, LUSTRE_FATAL_SIGS);
                                sigprocmask(SIG_BLOCK, &new, &old);
                                /*
                                 * 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 (signal_pending(current))
                                        ptlrpc_interrupted_set(set);
                                sigprocmask(SIG_SETMASK, &old, NULL);
                        }
                }

                LASSERT(rc == 0 || rc == -EINTR || rc == -ETIMEDOUT);

                /*
                 * -EINTR => all requests have been flagged rq_intr so next
                 * check completes.
                 * -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.
                 */
                if (rc == 0 && atomic_read(&set->set_remaining) == 0) {
                        list_for_each_entry(req, &set->set_requests,
                                            rq_set_chain) {
                                spin_lock(&req->rq_lock);
                                req->rq_invalid_rqset = 1;
                                spin_unlock(&req->rq_lock);
                        }
                }
        } while (rc != 0 || atomic_read(&set->set_remaining) != 0);

        LASSERT(atomic_read(&set->set_remaining) == 0);

        rc = set->set_rc; /* rq_status of already freed requests if any */
        list_for_each_entry(req, &set->set_requests, rq_set_chain) {
                LASSERT(req->rq_phase == RQ_PHASE_COMPLETE);
                if (req->rq_status != 0)
                        rc = req->rq_status;
        }

        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;

        if (!request)
                RETURN_EXIT;

        LASSERT(!request->rq_srv_req);
        LASSERT(request->rq_export == NULL);
        LASSERTF(!request->rq_receiving_reply, "req %px\n", request);
        LASSERTF(list_empty(&request->rq_list), "req %px\n", request);
        LASSERTF(list_empty(&request->rq_set_chain), "req %px\n", request);
        LASSERTF(!request->rq_replay, "req %px\n", request);

        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) {
                if (!locked)
                        spin_lock(&request->rq_import->imp_lock);
                list_del_init(&request->rq_replay_list);
                list_del_init(&request->rq_unreplied_list);
                if (!locked)
                        spin_unlock(&request->rq_import->imp_lock);
        }
        LASSERTF(list_empty(&request->rq_replay_list), "req %px\n", request);

        if (atomic_read(&request->rq_refcount) != 0) {
                DEBUG_REQ(D_ERROR, request,
                          "freeing request with nonzero refcount");
                LBUG();
        }

        if (request->rq_repbuf)
                sptlrpc_cli_free_repbuf(request);

        if (request->rq_import) {
                if (!ptlrpcd_check_work(request)) {
                        LASSERT(atomic_read(&request->rq_import->imp_reqs) > 0);
                        atomic_dec(&request->rq_import->imp_reqs);
                }
                class_import_put(request->rq_import);
                request->rq_import = NULL;
        }
        if (request->rq_bulk)
                ptlrpc_free_bulk(request->rq_bulk);

        if (request->rq_reqbuf || request->rq_clrbuf)
                sptlrpc_cli_free_reqbuf(request);

        if (request->rq_cli_ctx)
                sptlrpc_req_put_ctx(request, !locked);

        if (request->rq_pool)
                __ptlrpc_free_req_to_pool(request);
        else
                ptlrpc_request_cache_free(request);
        EXIT;
}

/**
 * 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.
 *
 * \retval 1    the request is freed
 * \retval 0    some others still hold references on the request
 */
static int __ptlrpc_req_put(struct ptlrpc_request *request, int locked)
{
        int count;

        ENTRY;
        if (!request)
                RETURN(1);

        LASSERT(request != LP_POISON);
        LASSERT(request->rq_reqmsg != LP_POISON);

        DEBUG_REQ(D_INFO, request, "refcount now %u",
                  atomic_read(&request->rq_refcount) - 1);

        spin_lock(&request->rq_lock);
        count = atomic_dec_return(&request->rq_refcount);
        LASSERTF(count >= 0, "Invalid ref count %d\n", count);

        /*
         * For open RPC, the client does not know the EA size (LOV, ACL, and
         * so on) before replied, then the client has to reserve very large
         * reply buffer. Such buffer will not be released until the RPC freed.
         * Since The open RPC is replayable, we need to keep it in the replay
         * list until close. If there are a lot of files opened concurrently,
         * then the client may be OOM.
         *
         * If fact, it is unnecessary to keep reply buffer for open replay,
         * related EAs have already been saved via mdc_save_lovea() before
         * coming here. So it is safe to free the reply buffer some earlier
         * before releasing the RPC to avoid client OOM. LU-9514
         */
        if (count == 1 && request->rq_early_free_repbuf && request->rq_repbuf) {
                spin_lock(&request->rq_early_free_lock);
                sptlrpc_cli_free_repbuf(request);
                request->rq_repbuf = NULL;
                request->rq_repbuf_len = 0;
                request->rq_repdata = NULL;
                request->rq_reqdata_len = 0;
                spin_unlock(&request->rq_early_free_lock);
        }
        spin_unlock(&request->rq_lock);

        if (!count)
                __ptlrpc_free_req(request, locked);

        RETURN(!count);
}

/**
 * Drop one request reference. Must be called with import imp_lock held.
 * When reference count drops to zero, request is freed.
 */
void ptlrpc_req_put_with_imp_lock(struct ptlrpc_request *request)
{
        assert_spin_locked(&request->rq_import->imp_lock);
        (void)__ptlrpc_req_put(request, 1);
}

/**
 * Drops one reference count for a request.
 */
void ptlrpc_req_put(struct ptlrpc_request *request)
{
        __ptlrpc_req_put(request, 0);
}
EXPORT_SYMBOL(ptlrpc_req_put);


/**
 * 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
 * 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.
 */
static int ptlrpc_unregister_reply(struct ptlrpc_request *request, int async)
{
        bool discard;
        /*
         * Might sleep.
         */
        LASSERT(!in_interrupt());

        /* Let's setup deadline for reply unlink. */
        if (CFS_FAIL_CHECK(OBD_FAIL_PTLRPC_LONG_REPL_UNLINK) &&
            async && request->rq_reply_deadline == 0 && cfs_fail_val == 0)
                request->rq_reply_deadline = ktime_get_real_seconds() +
                                             PTLRPC_REQ_LONG_UNLINK;

        /*
         * Nothing left to do.
         */
        if (!ptlrpc_cli_wait_unlink(request))
                RETURN(1);

        LNetMDUnlink(request->rq_reply_md_h);

        spin_lock(&request->rq_lock);
        discard = request->rq_reply_unlinked && !request->rq_req_unlinked;
        spin_unlock(&request->rq_lock);

        if (discard) /* Discard the request-out callback */
                __LNetMDUnlink(request->rq_req_md_h, discard);

        /*
         * Let's check it once again.
         */
        if (!ptlrpc_cli_wait_unlink(request))
                RETURN(1);

        /* Move to "Unregistering" phase as reply was not unlinked yet. */
        ptlrpc_rqphase_move(request, RQ_PHASE_UNREG_RPC);

        /*
         * Do not wait for unlink to finish.
         */
        if (async)
                RETURN(0);

        /*
         * We have to wait_event_idle_timeout() whatever the result, to get
         * a chance to run reply_in_callback(), and to make sure we've
         * unlinked before returning a req to the pool.
         */
        for (;;) {
                wait_queue_head_t *wq = (request->rq_set) ?
                                        &request->rq_set->set_waitq :
                                        &request->rq_reply_waitq;
                int seconds = PTLRPC_REQ_LONG_UNLINK;
                /*
                 * Network access will complete in finite time but the HUGE
                 * timeout lets us CWARN for visibility of sluggish NALs
                 */
                while (seconds > 0 &&
                       wait_event_idle_timeout(
                               *wq,
                               !ptlrpc_cli_wait_unlink(request),
                               cfs_time_seconds(1)) == 0)
                        seconds -= 1;
                if (seconds > 0) {
                        ptlrpc_rqphase_move(request, request->rq_next_phase);
                        RETURN(1);
                }

                DEBUG_REQ(D_WARNING, request,
                          "Unexpectedly long timeout receiving_reply=%d req_ulinked=%d reply_unlinked=%d",
                          request->rq_receiving_reply,
                          request->rq_req_unlinked,
                          request->rq_reply_unlinked);
        }
        RETURN(0);
}

static void ptlrpc_free_request(struct ptlrpc_request *req)
{
        spin_lock(&req->rq_lock);
        req->rq_replay = 0;
        spin_unlock(&req->rq_lock);

        if (req->rq_commit_cb)
                req->rq_commit_cb(req);
        list_del_init(&req->rq_replay_list);

        __ptlrpc_req_put(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;

        spin_lock(&imp->imp_lock);
        if (list_empty(&req->rq_replay_list)) {
                spin_unlock(&imp->imp_lock);
                return;
        }

        if (force || req->rq_transno <= imp->imp_peer_committed_transno) {
                if (imp->imp_replay_cursor == &req->rq_replay_list)
                        imp->imp_replay_cursor = req->rq_replay_list.next;
                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 meeting 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;
        unsigned int replay_scanned = 0, replay_freed = 0;
        unsigned int commit_scanned = 0, commit_freed = 0;
        unsigned int debug_level = D_INFO;
        __u64 peer_committed_transno;
        int imp_generation;
        time64_t start, now;

        ENTRY;
        LASSERT(imp != NULL);
        assert_spin_locked(&imp->imp_lock);

        start = ktime_get_seconds();
        /* save these here, we can potentially drop imp_lock after checking */
        peer_committed_transno = imp->imp_peer_committed_transno;
        imp_generation = imp->imp_generation;

        if (peer_committed_transno == imp->imp_last_transno_checked &&
            imp_generation == imp->imp_last_generation_checked) {
                CDEBUG(D_INFO, "%s: skip recheck: last_committed %llu\n",
                       imp->imp_obd->obd_name, peer_committed_transno);
                RETURN_EXIT;
        }
        CDEBUG(D_RPCTRACE, "%s: committing for last_committed %llu gen %d\n",
               imp->imp_obd->obd_name, peer_committed_transno, imp_generation);

        if (imp_generation != imp->imp_last_generation_checked ||
            imp->imp_last_transno_checked == 0)
                skip_committed_list = false;
        /* maybe drop imp_lock here, if another lock protected the lists */

        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 other threads are waiting on imp_lock, stop processing
                 * in this thread. Another thread can finish remaining work.
                 * This may happen if there are huge numbers of open files
                 * that are closed suddenly or evicted, or if the server
                 * commit interval is very high vs. RPC rate.
                 */
                if (++replay_scanned % 2048 == 0) {
                        now = ktime_get_seconds();
                        if (now > start + 5)
                                debug_level = D_WARNING;

                        if ((replay_freed > 128 && now > start + 3) &&
                            atomic_read(&imp->imp_waiting)) {
                                if (debug_level == D_INFO)
                                        debug_level = D_RPCTRACE;
                                break;
                        }
                }

                if (req->rq_import_generation < imp_generation) {
                        DEBUG_REQ(D_RPCTRACE, req, "free request with old gen");
                        GOTO(free_req, 0);
                }

                /* not yet committed */
                if (req->rq_transno > peer_committed_transno) {
                        DEBUG_REQ(D_RPCTRACE, req, "stopping search");
                        break;
                }

                if (req->rq_replay) {
                        DEBUG_REQ(D_RPCTRACE, req, "keeping (FL_REPLAY)");
                        list_move_tail(&req->rq_replay_list,
                                       &imp->imp_committed_list);
                        continue;
                }

                DEBUG_REQ(D_INFO, req, "commit (last_committed %llu)",
                          peer_committed_transno);
free_req:
                replay_freed++;
                ptlrpc_free_request(req);
        }

        if (skip_committed_list)
                GOTO(out, 0);

        list_for_each_entry_safe(req, saved, &imp->imp_committed_list,
                                 rq_replay_list) {
                LASSERT(req->rq_transno != 0);

                /* If other threads are waiting on imp_lock, stop processing
                 * in this thread. Another thread can finish remaining work. */
                if (++commit_scanned % 2048 == 0) {
                        now = ktime_get_seconds();
                        if (now > start + 6)
                                debug_level = D_WARNING;

                        if ((commit_freed > 128 && now > start + 4) &&
                            atomic_read(&imp->imp_waiting)) {
                                if (debug_level == D_INFO)
                                        debug_level = D_RPCTRACE;
                                break;
                        }
                }

                if (req->rq_import_generation < imp_generation ||
                    !req->rq_replay) {
                        DEBUG_REQ(D_RPCTRACE, req, "free %s open request",
                                  req->rq_import_generation <
                                  imp_generation ? "stale" : "closed");

                        if (imp->imp_replay_cursor == &req->rq_replay_list)
                                imp->imp_replay_cursor =
                                        req->rq_replay_list.next;

                        commit_freed++;
                        ptlrpc_free_request(req);
                }
        }
out:
        /* if full lists processed without interruption, avoid next scan */
        if (debug_level == D_INFO) {
                imp->imp_last_transno_checked = peer_committed_transno;
                imp->imp_last_generation_checked = imp_generation;
        }

        CDEBUG_LIMIT(debug_level,
                     "%s: %s: skip=%u replay=%u/%u committed=%u/%u\n",
                     imp->imp_obd->obd_name,
                     debug_level == D_INFO ? "normal" : "overloaded",
                     skip_committed_list, replay_freed, replay_scanned,
                     commit_freed, commit_scanned);
        EXIT;
}

void ptlrpc_cleanup_client(struct obd_import *imp)
{
        ENTRY;
        EXIT;
}

/**
 * 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");
        spin_lock(&req->rq_lock);

        /*
         * Request got reply but linked to the import list still.
         * Let ptlrpc_check_set() process it.
         */
        if (ptlrpc_client_replied(req)) {
                spin_unlock(&req->rq_lock);
                DEBUG_REQ(D_HA, req, "it has reply, so skip it");
                return;
        }

        req->rq_status = -EAGAIN;

        req->rq_resend = 1;
        req->rq_net_err = 0;
        req->rq_timedout = 0;

        ptlrpc_client_wake_req(req);
        spin_unlock(&req->rq_lock);
}

/* 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;

        spin_lock(&req->rq_lock);
        req->rq_restart = 1;
        req->rq_timedout = 0;
        ptlrpc_client_wake_req(req);
        spin_unlock(&req->rq_lock);
}

/**
 * Grab additional reference on a request \a req
 */
struct ptlrpc_request *ptlrpc_request_addref(struct ptlrpc_request *req)
{
        ENTRY;
        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 ptlrpc_request *iter;

        assert_spin_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))
                return;

        lustre_msg_add_flags(req->rq_reqmsg, MSG_REPLAY);

        spin_lock(&req->rq_lock);
        req->rq_resend = 0;
        spin_unlock(&req->rq_lock);

        LASSERT(imp->imp_replayable);
        /* Balanced in ptlrpc_free_committed, usually. */
        ptlrpc_request_addref(req);
        list_for_each_entry_reverse(iter, &imp->imp_replay_list,
                                    rq_replay_list) {
                /*
                 * We may have duplicate transnos if we create and then
                 * open a file, or for closes retained if to match creating
                 * opens, so use req->rq_xid as a secondary key.
                 * (See bugs 684, 685, and 428.)
                 * XXX no longer needed, but all opens need transnos!
                 */
                if (iter->rq_transno > req->rq_transno)
                        continue;

                if (iter->rq_transno == req->rq_transno) {
                        LASSERT(iter->rq_xid != req->rq_xid);
                        if (iter->rq_xid > req->rq_xid)
                                continue;
                }

                list_add(&req->rq_replay_list, &iter->rq_replay_list);
                return;
        }

        list_add(&req->rq_replay_list, &imp->imp_replay_list);
}

/**
 * Send request and wait until it completes.
 * Returns request processing status.
 */
int ptlrpc_queue_wait(struct ptlrpc_request *req)
{
        struct ptlrpc_request_set *set;
        int rc;

        ENTRY;
        LASSERT(req->rq_set == NULL);
        LASSERT(!req->rq_receiving_reply);

        set = ptlrpc_prep_set();
        if (!set) {
                CERROR("cannot allocate ptlrpc set: rc = %d\n", -ENOMEM);
                RETURN(-ENOMEM);
        }

        /* for distributed debugging */
        lustre_msg_set_status(req->rq_reqmsg, current->pid);

        /* 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(NULL, set);
        ptlrpc_set_destroy(set);

        RETURN(rc);
}
EXPORT_SYMBOL(ptlrpc_queue_wait);

/**
 * Callback used for replayed requests reply processing.
 * In case of successful reply calls registered 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 *args, int rc)
{
        struct ptlrpc_replay_async_args *aa = args;
        struct obd_import *imp = req->rq_import;

        ENTRY;
        atomic_dec(&imp->imp_replay_inflight);

        /*
         * Note: if it is bulk replay (MDS-MDS replay), then even if
         * server got the request, but bulk transfer timeout, let's
         * replay the bulk req again
         */
        if (!ptlrpc_client_replied(req) ||
            (req->rq_bulk &&
             lustre_msg_get_status(req->rq_repmsg) == -ETIMEDOUT)) {
                DEBUG_REQ(D_ERROR, req, "request replay timed out");
                GOTO(out, rc = -ETIMEDOUT);
        }

        if (lustre_msg_get_type(req->rq_repmsg) == PTL_RPC_MSG_ERR &&
            (lustre_msg_get_status(req->rq_repmsg) == -ENOTCONN ||
            lustre_msg_get_status(req->rq_repmsg) == -ENODEV))
                GOTO(out, rc = lustre_msg_get_status(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");
                spin_lock(&imp->imp_lock);
                imp->imp_vbr_failed = 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,
                         "%#llx/%#llx\n",
                         lustre_msg_get_transno(req->rq_reqmsg),
                         lustre_msg_get_transno(req->rq_repmsg));
        }

        spin_lock(&imp->imp_lock);
        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=%llu is bigger than replayed=%llu",
                          req->rq_transno,
                          lustre_msg_get_transno(req->rq_reqmsg));
                GOTO(out, rc = -EINVAL);
        }

        DEBUG_REQ(D_HA, req, "got reply");

        /* let the callback do fixups, possibly including in the request */
        if (req->rq_replay_cb)
                req->rq_replay_cb(req);

        if (ptlrpc_client_replied(req) &&
            lustre_msg_get_status(req->rq_repmsg) != aa->praa_old_status) {
                DEBUG_REQ(D_ERROR, req, "status %d, old was %d",
                          lustre_msg_get_status(req->rq_repmsg),
                          aa->praa_old_status);

                /*
                 * Note: If the replay fails for MDT-MDT recovery, let's
                 * abort all of the following requests in the replay
                 * and sending list, because MDT-MDT update requests
                 * are dependent on each other, see LU-7039
                 */
                if (imp->imp_connect_flags_orig & OBD_CONNECT_MDS_MDS) {
                        struct ptlrpc_request *free_req;
                        struct ptlrpc_request *tmp;

                        spin_lock(&imp->imp_lock);
                        list_for_each_entry_safe(free_req, tmp,
                                                 &imp->imp_replay_list,
                                                 rq_replay_list) {
                                ptlrpc_free_request(free_req);
                        }

                        list_for_each_entry_safe(free_req, tmp,
                                                 &imp->imp_committed_list,
                                                 rq_replay_list) {
                                ptlrpc_free_request(free_req);
                        }

                        list_for_each_entry_safe(free_req, tmp,
                                                 &imp->imp_delayed_list,
                                                 rq_list) {
                                spin_lock(&free_req->rq_lock);
                                free_req->rq_err = 1;
                                free_req->rq_status = -EIO;
                                ptlrpc_client_wake_req(free_req);
                                spin_unlock(&free_req->rq_lock);
                        }

                        list_for_each_entry_safe(free_req, tmp,
                                                 &imp->imp_sending_list,
                                                 rq_list) {
                                spin_lock(&free_req->rq_lock);
                                free_req->rq_err = 1;
                                free_req->rq_status = -EIO;
                                ptlrpc_client_wake_req(free_req);
                                spin_unlock(&free_req->rq_lock);
                        }
                        spin_unlock(&imp->imp_lock);
                }
        } else {
                /* Put it back for re-replay. */
                lustre_msg_set_status(req->rq_repmsg, aa->praa_old_status);
        }

        /*
         * 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)
                CERROR("Transno is 0 during replay!\n");

        /* continue with recovery */
        rc = ptlrpc_import_recovery_state_machine(imp);
 out:
        req->rq_send_state = aa->praa_old_state;

        if (rc != 0)
                /* this replay failed, so restart recovery */
                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);

        CFS_FAIL_TIMEOUT(OBD_FAIL_PTLRPC_REPLAY_PAUSE, cfs_fail_val);

        aa = ptlrpc_req_async_args(aa, req);
        memset(aa, 0, sizeof(*aa));

        /* Prepare request to be resent with ptlrpcd */
        aa->praa_old_state = req->rq_send_state;
        req->rq_send_state = LUSTRE_IMP_REPLAY;
        req->rq_phase = RQ_PHASE_NEW;
        req->rq_next_phase = RQ_PHASE_UNDEFINED;
        if (req->rq_repmsg)
                aa->praa_old_status = lustre_msg_get_status(req->rq_repmsg);
        req->rq_status = 0;
        req->rq_interpret_reply = ptlrpc_replay_interpret;
        /* Readjust the timeout for current conditions */
        ptlrpc_at_set_req_timeout(req);

        /* Tell server net_latency to calculate how long to wait for reply. */
        lustre_msg_set_service_timeout(req->rq_reqmsg,
                                       ptlrpc_at_get_net_latency(req));
        DEBUG_REQ(D_HA, req, "REPLAY");

        atomic_inc(&req->rq_import->imp_replay_inflight);
        spin_lock(&req->rq_lock);
        req->rq_early_free_repbuf = 0;
        spin_unlock(&req->rq_lock);
        ptlrpc_request_addref(req); /* ptlrpcd needs a ref */

        ptlrpcd_add_req(req);
        RETURN(0);
}

/**
 * Aborts all in-flight request on import \a imp sending and delayed lists
 */
void ptlrpc_abort_inflight(struct obd_import *imp)
{
        struct ptlrpc_request *req;
        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.
         */
        assert_spin_locked(&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_entry(req, &imp->imp_sending_list, 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 = -EIO;
                        ptlrpc_client_wake_req(req);
                }
                spin_unlock(&req->rq_lock);
        }

        list_for_each_entry(req, &imp->imp_delayed_list, rq_list) {
                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 = -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);

        EXIT;
}

/**
 * Abort all uncompleted requests in request set \a set
 */
void ptlrpc_abort_set(struct ptlrpc_request_set *set)
{
        struct ptlrpc_request *req;

        LASSERT(set != NULL);

        list_for_each_entry(req, &set->set_requests, rq_set_chain) {
                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);
        }
}

/**
 * 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
 * the same match bits for two different in-flight requests, hence we do
 * NOT want to have an XID per target or similar.
 *
 * To avoid an unlikely collision between match bits after a client reboot
 * (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
 * 9133 years, or permutations thereof.
 */
#define YEAR_2004 (1ULL << 30)
void ptlrpc_init_xid(void)
{
        time64_t now = ktime_get_real_seconds();
        u64 xid;

        if (now < YEAR_2004) {
                get_random_bytes(&xid, sizeof(xid));
                xid >>= 2;
                xid |= (1ULL << 61);
        } else {
                xid = (u64)now << 20;
        }

        /* Need to always be aligned to a power-of-two for mutli-bulk BRW */
        BUILD_BUG_ON((PTLRPC_BULK_OPS_COUNT & (PTLRPC_BULK_OPS_COUNT - 1)) !=
                     0);
        xid &= PTLRPC_BULK_OPS_MASK;
        atomic64_set(&ptlrpc_last_xid, xid);
}

/**
 * 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)
{
        return atomic64_add_return(PTLRPC_BULK_OPS_COUNT, &ptlrpc_last_xid);
}

/**
 * If request has a new allocated XID (new request or EINPROGRESS resend),
 * use this XID as matchbits of bulk, otherwise allocate a new matchbits for
 * request to ensure previous bulk fails and avoid problems with lost replies
 * and therefore several transfers landing into the same buffer from different
 * sending attempts.
 * Also, to avoid previous reply landing to a different sending attempt.
 */
void ptlrpc_set_mbits(struct ptlrpc_request *req)
{
        int md_count = req->rq_bulk ? req->rq_bulk->bd_md_count : 1;

        /*
         * Generate new matchbits for all resend requests, including
         * resend replay.
         */
        if (req->rq_resend) {
                __u64 old_mbits = req->rq_mbits;

                /*
                 * First time resend on -EINPROGRESS will generate new xid,
                 * so we can actually use the rq_xid as rq_mbits in such case,
                 * however, it's bit hard to distinguish such resend with a
                 * 'resend for the -EINPROGRESS resend'. To make it simple,
                 * we opt to generate mbits for all resend cases.
                 */
                if (OCD_HAS_FLAG(&req->rq_import->imp_connect_data,
                                 BULK_MBITS)) {
                        req->rq_mbits = ptlrpc_next_xid();
                } else {
                        /*
                         * Old version transfers rq_xid to peer as
                         * matchbits.
                         */
                        spin_lock(&req->rq_import->imp_lock);
                        list_del_init(&req->rq_unreplied_list);
                        ptlrpc_assign_next_xid_nolock(req);
                        spin_unlock(&req->rq_import->imp_lock);
                        req->rq_mbits = req->rq_xid;
                }
                CDEBUG(D_HA, "resend with new mbits old x%llu new x%llu\n",
                       old_mbits, req->rq_mbits);
        } else if (!(lustre_msg_get_flags(req->rq_reqmsg) & MSG_REPLAY)) {
                /* Request being sent first time, use xid as matchbits. */
                if (OCD_HAS_FLAG(&req->rq_import->imp_connect_data,
                                 BULK_MBITS) || req->rq_mbits == 0)
                {
                        req->rq_mbits = req->rq_xid;
                } else {
                        req->rq_mbits -= md_count - 1;
                }
        } else {
                /*
                 * Replay request, xid and matchbits have already been
                 * correctly assigned.
                 */
                return;
        }

        /*
         * For multi-bulk RPCs, rq_mbits is the last mbits needed for bulks so
         * that server can infer the number of bulks that were prepared,
         * see LU-1431
         */
        req->rq_mbits += md_count - 1;

        /*
         * Set rq_xid as rq_mbits to indicate the final bulk for the old
         * server which does not support OBD_CONNECT_BULK_MBITS. LU-6808.
         *
         * It's ok to directly set the rq_xid here, since this xid bump
         * won't affect the request position in unreplied list.
         */
        if (!OCD_HAS_FLAG(&req->rq_import->imp_connect_data, BULK_MBITS))
                req->rq_xid = req->rq_mbits;
}

/**
 * Get a glimpse at what next xid value might have been.
 * Returns possible next xid.
 */
__u64 ptlrpc_sample_next_xid(void)
{
        return atomic64_read(&ptlrpc_last_xid) + PTLRPC_BULK_OPS_COUNT;
}
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            = ktime_get_real_seconds();
        req->rq_deadline        = req->rq_sent + req->rq_timeout;
        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);
}

static int work_interpreter(const struct lu_env *env,
                            struct ptlrpc_request *req, void *args, int rc)
{
        struct ptlrpc_work_async_args *arg = args;

        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)
                RETURN(ERR_PTR(-EINVAL));

        /* copy some code from deprecated fakereq. */
        req = ptlrpc_request_cache_alloc(GFP_NOFS);
        if (!req) {
                CERROR("ptlrpc: run out of memory!\n");
                RETURN(ERR_PTR(-ENOMEM));
        }

        ptlrpc_cli_req_init(req);

        req->rq_send_state = LUSTRE_IMP_FULL;
        req->rq_type = PTL_RPC_MSG_REQUEST;
        req->rq_import = class_import_get(imp);
        req->rq_interpret_reply = work_interpreter;
        /* don't want reply */
        req->rq_no_delay = req->rq_no_resend = 1;
        req->rq_pill.rc_fmt = (void *)&worker_format;

        args = ptlrpc_req_async_args(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);