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LU-6158 mdt: always shrink_capsule in getxattr_all
[fs/lustre-release.git] / lustre / osp / osp_trans.c
index 39a42bc..e700acf 100644 (file)
@@ -41,7 +41,7 @@
  * OUT RPC.
  *
  * For the asynchronous idempotent operations, such as get_(x)attr, related
- * RPCs will be inserted into a osp_device based shared asynchronous request
+ * RPCs will be inserted into an osp_device based shared asynchronous request
  * queue - osp_device::opd_async_requests. When the queue is full, all the
  * requests in the queue will be packaged into a single OUT RPC and given to
  * the ptlrpcd daemon (for sending), then the queue is purged and other new
  * will be called one by one to handle each own result.
  *
  *
+ * There are three kinds of transactions
+ *
+ * 1. Local transaction, all of updates of the transaction are in the local MDT.
+ * 2. Remote transaction, all of updates of the transaction are in one remote
+ * MDT, which only happens in LFSCK now.
+ * 3. Distribute transaction, updates for the transaction are in mulitple MDTs.
+ *
  * Author: Di Wang <di.wang@intel.com>
  * Author: Fan, Yong <fan.yong@intel.com>
  */
 
 #define DEBUG_SUBSYSTEM S_MDS
 
+#include <lustre_net.h>
 #include "osp_internal.h"
 
-struct osp_async_update_args {
-       struct dt_update_request *oaua_update;
+/**
+ * The argument for the interpreter callback of osp request.
+ */
+struct osp_update_args {
+       struct osp_update_request *oaua_update;
+       atomic_t                 *oaua_count;
+       wait_queue_head_t        *oaua_waitq;
        bool                      oaua_flow_control;
 };
 
-struct osp_async_request {
-       /* list in the dt_update_request::dur_cb_items */
-       struct list_head                 oar_list;
+/**
+ * Call back for each update request.
+ */
+struct osp_update_callback {
+       /* list in the osp_update_request::our_cb_items */
+       struct list_head                 ouc_list;
 
        /* The target of the async update request. */
-       struct osp_object               *oar_obj;
+       struct osp_object               *ouc_obj;
 
-       /* The data used by oar_interpreter. */
-       void                            *oar_data;
+       /* The data used by or_interpreter. */
+       void                            *ouc_data;
 
        /* The interpreter function called after the async request handled. */
-       osp_async_request_interpreter_t  oar_interpreter;
+       osp_update_interpreter_t        ouc_interpreter;
 };
 
+static struct object_update_request *object_update_request_alloc(size_t size)
+{
+       struct object_update_request *ourq;
+
+       OBD_ALLOC_LARGE(ourq, size);
+       if (ourq == NULL)
+               return ERR_PTR(-ENOMEM);
+
+       ourq->ourq_magic = UPDATE_REQUEST_MAGIC;
+       ourq->ourq_count = 0;
+
+       return ourq;
+}
+
+/**
+ * Allocate new update request
+ *
+ * Allocate new update request and insert it to the req_update_list.
+ *
+ * \param [in] our     osp_udate_request where to create a new
+ *                      update request
+ *
+ * \retval     0 if creation succeeds.
+ * \retval     negative errno if creation fails.
+ */
+int osp_object_update_request_create(struct osp_update_request *our,
+                                    size_t size)
+{
+       struct osp_update_request_sub *ours;
+
+       OBD_ALLOC_PTR(ours);
+       if (ours == NULL)
+               return -ENOMEM;
+
+       if (size < OUT_UPDATE_INIT_BUFFER_SIZE)
+               size = OUT_UPDATE_INIT_BUFFER_SIZE;
+
+       ours->ours_req = object_update_request_alloc(size);
+
+       if (IS_ERR(ours->ours_req)) {
+               OBD_FREE_PTR(ours);
+               return -ENOMEM;
+       }
+
+       ours->ours_req_size = size;
+       INIT_LIST_HEAD(&ours->ours_list);
+       list_add_tail(&ours->ours_list, &our->our_req_list);
+
+       return 0;
+}
+
+/**
+ * Get current update request
+ *
+ * Get current object update request from our_req_list in
+ * osp_update_request, because we always insert the new update
+ * request in the last position, so the last update request
+ * in the list will be the current update req.
+ *
+ * \param[in] our      osp update request where to get the
+ *                      current object update.
+ *
+ * \retval             the current object update.
+ **/
+struct osp_update_request_sub *
+osp_current_object_update_request(struct osp_update_request *our)
+{
+       if (list_empty(&our->our_req_list))
+               return NULL;
+
+       return list_entry(our->our_req_list.prev, struct osp_update_request_sub,
+                         ours_list);
+}
+
+/**
+ * Allocate and initialize osp_update_request
+ *
+ * osp_update_request is being used to track updates being executed on
+ * this dt_device(OSD or OSP). The update buffer will be 4k initially,
+ * and increased if needed.
+ *
+ * \param [in] dt      dt device
+ *
+ * \retval             osp_update_request being allocated if succeed
+ * \retval             ERR_PTR(errno) if failed
+ */
+struct osp_update_request *osp_update_request_create(struct dt_device *dt)
+{
+       struct osp_update_request *our;
+
+       OBD_ALLOC_PTR(our);
+       if (our == NULL)
+               return ERR_PTR(-ENOMEM);
+
+       INIT_LIST_HEAD(&our->our_req_list);
+       INIT_LIST_HEAD(&our->our_cb_items);
+       INIT_LIST_HEAD(&our->our_list);
+
+       osp_object_update_request_create(our, OUT_UPDATE_INIT_BUFFER_SIZE);
+       return our;
+}
+
+void osp_update_request_destroy(struct osp_update_request *our)
+{
+       struct osp_update_request_sub *ours;
+       struct osp_update_request_sub *tmp;
+
+       if (our == NULL)
+               return;
+
+       list_for_each_entry_safe(ours, tmp, &our->our_req_list, ours_list) {
+               list_del(&ours->ours_list);
+               if (ours->ours_req != NULL)
+                       OBD_FREE(ours->ours_req, ours->ours_req_size);
+               OBD_FREE_PTR(ours);
+       }
+       OBD_FREE_PTR(our);
+}
+
+static void
+object_update_request_dump(const struct object_update_request *ourq,
+                          unsigned int mask)
+{
+       unsigned int i;
+       size_t total_size = 0;
+
+       for (i = 0; i < ourq->ourq_count; i++) {
+               struct object_update    *update;
+               size_t                  size = 0;
+
+               update = object_update_request_get(ourq, i, &size);
+               LASSERT(update != NULL);
+               CDEBUG(mask, "i = %u fid = "DFID" op = %s master = %u"
+                      "params = %d batchid = "LPU64" size = %zu\n",
+                      i, PFID(&update->ou_fid),
+                      update_op_str(update->ou_type),
+                      update->ou_master_index, update->ou_params_count,
+                      update->ou_batchid, size);
+
+               total_size += size;
+       }
+
+       CDEBUG(mask, "updates = %p magic = %x count = %d size = %zu\n", ourq,
+              ourq->ourq_magic, ourq->ourq_count, total_size);
+}
+
 /**
- * Allocate an asynchronous request and initialize it with the given parameters.
+ * Prepare update request.
+ *
+ * Prepare OUT update ptlrpc request, and the request usually includes
+ * all of updates (stored in \param ureq) from one operation.
+ *
+ * \param[in] env      execution environment
+ * \param[in] imp      import on which ptlrpc request will be sent
+ * \param[in] ureq     hold all of updates which will be packed into the req
+ * \param[in] reqp     request to be created
+ *
+ * \retval             0 if preparation succeeds.
+ * \retval             negative errno if preparation fails.
+ */
+int osp_prep_update_req(const struct lu_env *env, struct obd_import *imp,
+                       struct osp_update_request *our,
+                       struct ptlrpc_request **reqp)
+{
+       struct ptlrpc_request           *req;
+       struct ptlrpc_bulk_desc         *desc;
+       struct osp_update_request_sub   *ours;
+       struct out_update_header        *ouh;
+       struct out_update_buffer        *oub;
+       __u32                           buf_count = 0;
+       int                             rc;
+       ENTRY;
+
+       list_for_each_entry(ours, &our->our_req_list, ours_list) {
+               object_update_request_dump(ours->ours_req, D_INFO);
+               buf_count++;
+       }
+
+       req = ptlrpc_request_alloc(imp, &RQF_OUT_UPDATE);
+       if (req == NULL)
+               RETURN(-ENOMEM);
+
+       req_capsule_set_size(&req->rq_pill, &RMF_OUT_UPDATE_BUF, RCL_CLIENT,
+                            buf_count * sizeof(*oub));
+
+       rc = ptlrpc_request_pack(req, LUSTRE_MDS_VERSION, OUT_UPDATE);
+       if (rc != 0)
+               GOTO(out_req, rc);
+
+       ouh = req_capsule_client_get(&req->rq_pill, &RMF_OUT_UPDATE_HEADER);
+       ouh->ouh_magic = OUT_UPDATE_HEADER_MAGIC;
+       ouh->ouh_count = buf_count;
+
+       oub = req_capsule_client_get(&req->rq_pill, &RMF_OUT_UPDATE_BUF);
+       list_for_each_entry(ours, &our->our_req_list, ours_list) {
+               oub->oub_size = ours->ours_req_size;
+               oub++;
+       }
+
+       req->rq_bulk_write = 1;
+       desc = ptlrpc_prep_bulk_imp(req, buf_count,
+               MD_MAX_BRW_SIZE >> LNET_MTU_BITS,
+               PTLRPC_BULK_GET_SOURCE | PTLRPC_BULK_BUF_KVEC,
+               MDS_BULK_PORTAL, &ptlrpc_bulk_kvec_ops);
+       if (desc == NULL)
+               GOTO(out_req, rc = -ENOMEM);
+
+       /* NB req now owns desc and will free it when it gets freed */
+       list_for_each_entry(ours, &our->our_req_list, ours_list)
+               desc->bd_frag_ops->add_iov_frag(desc, ours->ours_req,
+                                               ours->ours_req_size);
+
+       req_capsule_set_size(&req->rq_pill, &RMF_OUT_UPDATE_REPLY,
+                            RCL_SERVER, OUT_UPDATE_REPLY_SIZE);
+
+       ptlrpc_request_set_replen(req);
+       req->rq_request_portal = OUT_PORTAL;
+       req->rq_reply_portal = OSC_REPLY_PORTAL;
+       *reqp = req;
+
+out_req:
+       if (rc < 0)
+               ptlrpc_req_finished(req);
+
+       RETURN(rc);
+}
+
+/**
+ * Send update RPC.
+ *
+ * Send update request to the remote MDT synchronously.
+ *
+ * \param[in] env      execution environment
+ * \param[in] imp      import on which ptlrpc request will be sent
+ * \param[in] our      hold all of updates which will be packed into the req
+ * \param[in] reqp     request to be created
+ *
+ * \retval             0 if RPC succeeds.
+ * \retval             negative errno if RPC fails.
+ */
+
+int osp_remote_sync(const struct lu_env *env, struct osp_device *osp,
+                   struct osp_update_request *our,
+                   struct ptlrpc_request **reqp)
+{
+       struct obd_import       *imp = osp->opd_obd->u.cli.cl_import;
+       struct ptlrpc_request   *req = NULL;
+       int                     rc;
+       ENTRY;
+
+       rc = osp_prep_update_req(env, imp, our, &req);
+       if (rc != 0)
+               RETURN(rc);
+
+       /* This will only be called with read-only update, and these updates
+        * might be used to retrieve update log during recovery process, so
+        * it will be allowed to send during recovery process */
+       req->rq_allow_replay = 1;
+
+       /* Note: some dt index api might return non-zero result here, like
+        * osd_index_ea_lookup, so we should only check rc < 0 here */
+       rc = ptlrpc_queue_wait(req);
+       our->our_rc = rc;
+       if (rc < 0 || reqp == NULL)
+               ptlrpc_req_finished(req);
+       else
+               *reqp = req;
+
+       RETURN(rc);
+}
+
+static void osp_trans_stop_cb(struct osp_thandle *oth, int result)
+{
+       struct dt_txn_commit_cb *dcb;
+       struct dt_txn_commit_cb *tmp;
+
+       /* call per-transaction stop callbacks if any */
+       list_for_each_entry_safe(dcb, tmp, &oth->ot_stop_dcb_list,
+                                dcb_linkage) {
+               LASSERTF(dcb->dcb_magic == TRANS_COMMIT_CB_MAGIC,
+                        "commit callback entry: magic=%x name='%s'\n",
+                        dcb->dcb_magic, dcb->dcb_name);
+               list_del_init(&dcb->dcb_linkage);
+               dcb->dcb_func(NULL, &oth->ot_super, dcb, result);
+       }
+}
+
+/**
+ * Allocate an osp request and initialize it with the given parameters.
  *
  * \param[in] obj              pointer to the operation target
  * \param[in] data             pointer to the data used by the interpreter
@@ -90,38 +393,38 @@ struct osp_async_request {
  * \retval                     pointer to the asychronous request
  * \retval                     NULL if the allocation failed
  */
-static struct osp_async_request *
-osp_async_request_init(struct osp_object *obj, void *data,
-                      osp_async_request_interpreter_t interpreter)
+static struct osp_update_callback *
+osp_update_callback_init(struct osp_object *obj, void *data,
+                        osp_update_interpreter_t interpreter)
 {
-       struct osp_async_request *oar;
+       struct osp_update_callback *ouc;
 
-       OBD_ALLOC_PTR(oar);
-       if (oar == NULL)
+       OBD_ALLOC_PTR(ouc);
+       if (ouc == NULL)
                return NULL;
 
        lu_object_get(osp2lu_obj(obj));
-       INIT_LIST_HEAD(&oar->oar_list);
-       oar->oar_obj = obj;
-       oar->oar_data = data;
-       oar->oar_interpreter = interpreter;
+       INIT_LIST_HEAD(&ouc->ouc_list);
+       ouc->ouc_obj = obj;
+       ouc->ouc_data = data;
+       ouc->ouc_interpreter = interpreter;
 
-       return oar;
+       return ouc;
 }
 
 /**
- * Destroy the asychronous request.
+ * Destroy the osp_update_callback.
  *
  * \param[in] env      pointer to the thread context
- * \param[in] oar      pointer to asychronous request
+ * \param[in] ouc      pointer to osp_update_callback
  */
-static void osp_async_request_fini(const struct lu_env *env,
-                                  struct osp_async_request *oar)
+static void osp_update_callback_fini(const struct lu_env *env,
+                                    struct osp_update_callback *ouc)
 {
-       LASSERT(list_empty(&oar->oar_list));
+       LASSERT(list_empty(&ouc->ouc_list));
 
-       lu_object_put(env, osp2lu_obj(oar->oar_obj));
-       OBD_FREE_PTR(oar);
+       lu_object_put(env, osp2lu_obj(ouc->ouc_obj));
+       OBD_FREE_PTR(ouc);
 }
 
 /**
@@ -138,22 +441,33 @@ static void osp_async_request_fini(const struct lu_env *env,
  * \retval             0 for success
  * \retval             negative error number on failure
  */
-static int osp_async_update_interpret(const struct lu_env *env,
-                                     struct ptlrpc_request *req,
-                                     void *arg, int rc)
+static int osp_update_interpret(const struct lu_env *env,
+                               struct ptlrpc_request *req, void *arg, int rc)
 {
        struct object_update_reply      *reply  = NULL;
-       struct osp_async_update_args    *oaua   = arg;
-       struct dt_update_request        *dt_update = oaua->oaua_update;
-       struct osp_async_request        *oar;
-       struct osp_async_request        *next;
+       struct osp_update_args          *oaua   = arg;
+       struct osp_update_request       *our = oaua->oaua_update;
+       struct osp_thandle              *oth;
+       struct osp_update_callback      *ouc;
+       struct osp_update_callback      *next;
        int                              count  = 0;
        int                              index  = 0;
        int                              rc1    = 0;
 
-       if (oaua->oaua_flow_control)
-               obd_put_request_slot(
-                               &dt2osp_dev(dt_update->dur_dt)->opd_obd->u.cli);
+       ENTRY;
+
+       if (our == NULL)
+               RETURN(0);
+
+       oaua->oaua_update = NULL;
+       oth = our->our_th;
+       if (oaua->oaua_flow_control) {
+               struct osp_device *osp;
+
+               LASSERT(oth != NULL);
+               osp = dt2osp_dev(oth->ot_super.th_dev);
+               obd_put_request_slot(&osp->opd_obd->u.cli);
+       }
 
        /* Unpack the results from the reply message. */
        if (req->rq_repmsg != NULL) {
@@ -168,9 +482,8 @@ static int osp_async_update_interpret(const struct lu_env *env,
                rc1 = rc;
        }
 
-       list_for_each_entry_safe(oar, next, &dt_update->dur_cb_items,
-                                oar_list) {
-               list_del_init(&oar->oar_list);
+       list_for_each_entry_safe(ouc, next, &our->our_cb_items, ouc_list) {
+               list_del_init(&ouc->ouc_list);
 
                /* The peer may only have handled some requests (indicated
                 * by the 'count') in the packaged OUT RPC, we can only get
@@ -189,15 +502,27 @@ static int osp_async_update_interpret(const struct lu_env *env,
                                rc1 = -EINVAL;
                }
 
-               oar->oar_interpreter(env, reply, req, oar->oar_obj,
-                                      oar->oar_data, index, rc1);
-               osp_async_request_fini(env, oar);
+               if (ouc->ouc_interpreter != NULL)
+                       ouc->ouc_interpreter(env, reply, req, ouc->ouc_obj,
+                                            ouc->ouc_data, index, rc1);
+
+               osp_update_callback_fini(env, ouc);
                index++;
        }
 
-       out_destroy_update_req(dt_update);
+       if (oaua->oaua_count != NULL && atomic_dec_and_test(oaua->oaua_count))
+               wake_up_all(oaua->oaua_waitq);
 
-       return 0;
+       if (oth != NULL) {
+               /* oth and osp_update_requests will be destoryed in
+                * osp_thandle_put */
+               osp_trans_stop_cb(oth, rc);
+               osp_thandle_put(oth);
+       } else {
+               osp_update_request_destroy(our);
+       }
+
+       RETURN(0);
 }
 
 /**
@@ -206,40 +531,43 @@ static int osp_async_update_interpret(const struct lu_env *env,
  *
  * \param[in] env      pointer to the thread context
  * \param[in] osp      pointer to the OSP device
- * \param[in] update   pointer to the shared queue
+ * \param[in] our      pointer to the shared queue
  *
  * \retval             0 for success
  * \retval             negative error number on failure
  */
 int osp_unplug_async_request(const struct lu_env *env,
                             struct osp_device *osp,
-                            struct dt_update_request *update)
+                            struct osp_update_request *our)
 {
-       struct osp_async_update_args    *args;
-       struct ptlrpc_request           *req = NULL;
-       int                              rc;
+       struct osp_update_args  *args;
+       struct ptlrpc_request   *req = NULL;
+       int                      rc;
 
-       rc = out_prep_update_req(env, osp->opd_obd->u.cli.cl_import,
-                                update->dur_req, &req);
+       rc = osp_prep_update_req(env, osp->opd_obd->u.cli.cl_import,
+                                our, &req);
        if (rc != 0) {
-               struct osp_async_request *oar;
-               struct osp_async_request *next;
-
-               list_for_each_entry_safe(oar, next,
-                                        &update->dur_cb_items, oar_list) {
-                       list_del_init(&oar->oar_list);
-                       oar->oar_interpreter(env, NULL, NULL, oar->oar_obj,
-                                              oar->oar_data, 0, rc);
-                       osp_async_request_fini(env, oar);
+               struct osp_update_callback *ouc;
+               struct osp_update_callback *next;
+
+               list_for_each_entry_safe(ouc, next,
+                                        &our->our_cb_items, ouc_list) {
+                       list_del_init(&ouc->ouc_list);
+                       if (ouc->ouc_interpreter != NULL)
+                               ouc->ouc_interpreter(env, NULL, NULL,
+                                                    ouc->ouc_obj,
+                                                    ouc->ouc_data, 0, rc);
+                       osp_update_callback_fini(env, ouc);
                }
-               out_destroy_update_req(update);
+               osp_update_request_destroy(our);
        } else {
-               LASSERT(list_empty(&update->dur_list));
-
                args = ptlrpc_req_async_args(req);
-               args->oaua_update = update;
-               req->rq_interpret_reply = osp_async_update_interpret;
-               ptlrpcd_add_req(req, PDL_POLICY_LOCAL, -1);
+               args->oaua_update = our;
+               args->oaua_count = NULL;
+               args->oaua_waitq = NULL;
+               args->oaua_flow_control = false;
+               req->rq_interpret_reply = osp_update_interpret;
+               ptlrpcd_add_req(req);
        }
 
        return rc;
@@ -250,26 +578,59 @@ int osp_unplug_async_request(const struct lu_env *env,
  * request queue - osp_device::opd_async_requests.
  *
  * If the osp_device::opd_async_requests is not NULL, then return it directly;
- * otherwise create new dt_update_request and attach it to opd_async_requests.
+ * otherwise create new osp_update_request and attach it to opd_async_requests.
  *
  * \param[in] osp      pointer to the OSP device
  *
  * \retval             pointer to the shared queue
  * \retval             negative error number on failure
  */
-static struct dt_update_request *
+static struct osp_update_request *
 osp_find_or_create_async_update_request(struct osp_device *osp)
 {
-       struct dt_update_request *update = osp->opd_async_requests;
+       struct osp_update_request *our = osp->opd_async_requests;
 
-       if (update != NULL)
-               return update;
+       if (our != NULL)
+               return our;
 
-       update = out_create_update_req(&osp->opd_dt_dev);
-       if (!IS_ERR(update))
-               osp->opd_async_requests = update;
+       our = osp_update_request_create(&osp->opd_dt_dev);
+       if (IS_ERR(our))
+               return our;
 
-       return update;
+       osp->opd_async_requests = our;
+
+       return our;
+}
+
+/**
+ * Insert an osp_update_callback into the osp_update_request.
+ *
+ * Insert an osp_update_callback to the osp_update_request. Usually each update
+ * in the osp_update_request will have one correspondent callback, and these
+ * callbacks will be called in rq_interpret_reply.
+ *
+ * \param[in] env              pointer to the thread context
+ * \param[in] obj              pointer to the operation target object
+ * \param[in] data             pointer to the data used by the interpreter
+ * \param[in] interpreter      pointer to the interpreter function
+ *
+ * \retval                     0 for success
+ * \retval                     negative error number on failure
+ */
+int osp_insert_update_callback(const struct lu_env *env,
+                              struct osp_update_request *our,
+                              struct osp_object *obj, void *data,
+                              osp_update_interpreter_t interpreter)
+{
+       struct osp_update_callback  *ouc;
+
+       ouc = osp_update_callback_init(obj, data, interpreter);
+       if (ouc == NULL)
+               RETURN(-ENOMEM);
+
+       list_add_tail(&ouc->ouc_list, &our->our_cb_items);
+
+       return 0;
 }
 
 /**
@@ -287,8 +648,8 @@ osp_find_or_create_async_update_request(struct osp_device *osp)
  * \param[in] env              pointer to the thread context
  * \param[in] op               operation type, see 'enum update_type'
  * \param[in] obj              pointer to the operation target
- * \param[in] count            array size of the subsequent @lens and @bufs
- * \param[in] lens             buffer length array for the subsequent @bufs
+ * \param[in] count            array size of the subsequent \a lens and \a bufs
+ * \param[in] lens             buffer length array for the subsequent \a bufs
  * \param[in] bufs             the buffers to compose the request
  * \param[in] data             pointer to the data used by the interpreter
  * \param[in] interpreter      pointer to the interpreter function
@@ -296,55 +657,90 @@ osp_find_or_create_async_update_request(struct osp_device *osp)
  * \retval                     0 for success
  * \retval                     negative error number on failure
  */
-int osp_insert_async_request(const struct lu_env *env,
-                            int op, struct osp_object *obj, int count,
-                            int *lens, const char **bufs, void *data,
-                            osp_async_request_interpreter_t interpreter)
-{
-       struct osp_async_request     *oar;
-       struct osp_device            *osp = lu2osp_dev(osp2lu_obj(obj)->lo_dev);
-       struct dt_update_request     *update;
-       int                           rc  = 0;
+int osp_insert_async_request(const struct lu_env *env, enum update_type op,
+                            struct osp_object *obj, int count,
+                            __u16 *lens, const void **bufs, void *data,
+                            osp_update_interpreter_t interpreter)
+{
+       struct osp_device               *osp;
+       struct osp_update_request       *our;
+       struct object_update            *object_update;
+       size_t                          max_update_size;
+       struct object_update_request    *ureq;
+       struct osp_update_request_sub   *ours;
+       int                             rc = 0;
        ENTRY;
 
-       oar = osp_async_request_init(obj, data, interpreter);
-       if (oar == NULL)
-               RETURN(-ENOMEM);
-
-       update = osp_find_or_create_async_update_request(osp);
-       if (IS_ERR(update))
-               GOTO(out, rc = PTR_ERR(update));
+       osp = lu2osp_dev(osp2lu_obj(obj)->lo_dev);
+       our = osp_find_or_create_async_update_request(osp);
+       if (IS_ERR(our))
+               RETURN(PTR_ERR(our));
 
 again:
-       rc = out_insert_update(env, update, op, lu_object_fid(osp2lu_obj(obj)),
-                              count, lens, bufs);
+       ours = osp_current_object_update_request(our);
+
+       ureq = ours->ours_req;
+       max_update_size = ours->ours_req_size -
+                         object_update_request_size(ureq);
+
+       object_update = update_buffer_get_update(ureq, ureq->ourq_count);
+       rc = out_update_pack(env, object_update, &max_update_size, op,
+                            lu_object_fid(osp2lu_obj(obj)), count, lens, bufs);
        /* The queue is full. */
        if (rc == -E2BIG) {
                osp->opd_async_requests = NULL;
                mutex_unlock(&osp->opd_async_requests_mutex);
 
-               rc = osp_unplug_async_request(env, osp, update);
+               rc = osp_unplug_async_request(env, osp, our);
                mutex_lock(&osp->opd_async_requests_mutex);
                if (rc != 0)
-                       GOTO(out, rc);
+                       RETURN(rc);
 
-               update = osp_find_or_create_async_update_request(osp);
-               if (IS_ERR(update))
-                       GOTO(out, rc = PTR_ERR(update));
+               our = osp_find_or_create_async_update_request(osp);
+               if (IS_ERR(our))
+                       RETURN(PTR_ERR(our));
 
                goto again;
+       } else {
+               if (rc < 0)
+                       RETURN(rc);
+
+               ureq->ourq_count++;
        }
 
-       if (rc == 0)
-               list_add_tail(&oar->oar_list, &update->dur_cb_items);
+       rc = osp_insert_update_callback(env, our, obj, data, interpreter);
 
-       GOTO(out, rc);
+       RETURN(rc);
+}
 
-out:
-       if (rc != 0)
-               osp_async_request_fini(env, oar);
+int osp_trans_update_request_create(struct thandle *th)
+{
+       struct osp_thandle              *oth = thandle_to_osp_thandle(th);
+       struct osp_update_request       *our;
 
-       return rc;
+       if (oth->ot_our != NULL)
+               return 0;
+
+       our = osp_update_request_create(th->th_dev);
+       if (IS_ERR(our)) {
+               th->th_result = PTR_ERR(our);
+               return PTR_ERR(our);
+       }
+
+       oth->ot_our = our;
+       our->our_th = oth;
+
+       return 0;
+}
+
+void osp_thandle_destroy(struct osp_thandle *oth)
+{
+       LASSERT(oth->ot_magic == OSP_THANDLE_MAGIC);
+       LASSERT(list_empty(&oth->ot_commit_dcb_list));
+       LASSERT(list_empty(&oth->ot_stop_dcb_list));
+       if (oth->ot_our != NULL)
+               osp_update_request_destroy(oth->ot_our);
+       OBD_FREE_PTR(oth);
 }
 
 /**
@@ -376,110 +772,492 @@ out:
  */
 struct thandle *osp_trans_create(const struct lu_env *env, struct dt_device *d)
 {
-       struct thandle          *th = NULL;
-       struct thandle_update   *tu = NULL;
-       int                      rc = 0;
+       struct osp_thandle              *oth;
+       struct thandle                  *th = NULL;
+       ENTRY;
 
-       OBD_ALLOC_PTR(th);
-       if (unlikely(th == NULL))
-               GOTO(out, rc = -ENOMEM);
+       OBD_ALLOC_PTR(oth);
+       if (unlikely(oth == NULL))
+               RETURN(ERR_PTR(-ENOMEM));
 
+       oth->ot_magic = OSP_THANDLE_MAGIC;
+       th = &oth->ot_super;
        th->th_dev = d;
        th->th_tags = LCT_TX_HANDLE;
-       atomic_set(&th->th_refc, 1);
-       th->th_alloc_size = sizeof(*th);
 
-       OBD_ALLOC_PTR(tu);
-       if (tu == NULL)
-               GOTO(out, rc = -ENOMEM);
+       atomic_set(&oth->ot_refcount, 1);
+       INIT_LIST_HEAD(&oth->ot_commit_dcb_list);
+       INIT_LIST_HEAD(&oth->ot_stop_dcb_list);
 
-       INIT_LIST_HEAD(&tu->tu_remote_update_list);
-       tu->tu_only_remote_trans = 1;
-       th->th_update = tu;
+       RETURN(th);
+}
 
-out:
-       if (rc != 0) {
-               if (tu != NULL)
-                       OBD_FREE_PTR(tu);
-               if (th != NULL)
-                       OBD_FREE_PTR(th);
-               th = ERR_PTR(rc);
+/**
+ * Add commit callback to transaction.
+ *
+ * Add commit callback to the osp thandle, which will be called
+ * when the thandle is committed remotely.
+ *
+ * \param[in] th       the thandle
+ * \param[in] dcb      commit callback structure
+ *
+ * \retval             only return 0 for now.
+ */
+int osp_trans_cb_add(struct thandle *th, struct dt_txn_commit_cb *dcb)
+{
+       struct osp_thandle *oth = thandle_to_osp_thandle(th);
+
+       LASSERT(dcb->dcb_magic == TRANS_COMMIT_CB_MAGIC);
+       LASSERT(&dcb->dcb_func != NULL);
+       if (dcb->dcb_flags & DCB_TRANS_STOP)
+               list_add(&dcb->dcb_linkage, &oth->ot_stop_dcb_list);
+       else
+               list_add(&dcb->dcb_linkage, &oth->ot_commit_dcb_list);
+       return 0;
+}
+
+static void osp_trans_commit_cb(struct osp_thandle *oth, int result)
+{
+       struct dt_txn_commit_cb *dcb;
+       struct dt_txn_commit_cb *tmp;
+
+       LASSERT(atomic_read(&oth->ot_refcount) > 0);
+       /* call per-transaction callbacks if any */
+       list_for_each_entry_safe(dcb, tmp, &oth->ot_commit_dcb_list,
+                                dcb_linkage) {
+               LASSERTF(dcb->dcb_magic == TRANS_COMMIT_CB_MAGIC,
+                        "commit callback entry: magic=%x name='%s'\n",
+                        dcb->dcb_magic, dcb->dcb_name);
+               list_del_init(&dcb->dcb_linkage);
+               dcb->dcb_func(NULL, &oth->ot_super, dcb, result);
        }
+}
+
+static void osp_request_commit_cb(struct ptlrpc_request *req)
+{
+       struct thandle          *th = req->rq_cb_data;
+       struct osp_thandle      *oth;
+       __u64                   last_committed_transno = 0;
+       int                     result = req->rq_status;
+       ENTRY;
+
+       if (th == NULL)
+               RETURN_EXIT;
+
+       oth = thandle_to_osp_thandle(th);
+       if (lustre_msg_get_last_committed(req->rq_repmsg))
+               last_committed_transno =
+                       lustre_msg_get_last_committed(req->rq_repmsg);
+
+       if (last_committed_transno <
+               req->rq_import->imp_peer_committed_transno)
+               last_committed_transno =
+                       req->rq_import->imp_peer_committed_transno;
+
+       CDEBUG(D_HA, "trans no "LPU64" committed transno "LPU64"\n",
+              req->rq_transno, last_committed_transno);
+
+       /* If the transaction is not really committed, mark result = 1 */
+       if (req->rq_transno != 0 &&
+           (req->rq_transno > last_committed_transno) && result == 0)
+               result = 1;
 
-       return th;
+       osp_trans_commit_cb(oth, result);
+       req->rq_committed = 1;
+       osp_thandle_put(oth);
+       EXIT;
 }
 
 /**
- * Trigger the request for remote updates.
+ * callback of osp transaction
+ *
+ * Call all of callbacks for this osp thandle. This will only be
+ * called in error handler path. In the normal processing path,
+ * these callback will be called in osp_request_commit_cb() and
+ * osp_update_interpret().
+ *
+ * \param [in] env     execution environment
+ * \param [in] oth     osp thandle
+ * \param [in] rc      result of the osp thandle
+ */
+void osp_trans_callback(const struct lu_env *env,
+                       struct osp_thandle *oth, int rc)
+{
+       struct osp_update_callback *ouc;
+       struct osp_update_callback *next;
+
+       if (oth->ot_our != NULL) {
+               list_for_each_entry_safe(ouc, next,
+                                        &oth->ot_our->our_cb_items, ouc_list) {
+                       list_del_init(&ouc->ouc_list);
+                       if (ouc->ouc_interpreter != NULL)
+                               ouc->ouc_interpreter(env, NULL, NULL,
+                                                    ouc->ouc_obj,
+                                                    ouc->ouc_data, 0, rc);
+                       osp_update_callback_fini(env, ouc);
+               }
+       }
+       osp_trans_stop_cb(oth, rc);
+       osp_trans_commit_cb(oth, rc);
+}
+
+/**
+ * Send the request for remote updates.
  *
- * If the transaction is a remote transaction, then related remote updates
- * will be sent asynchronously; otherwise, the cross MDTs transaction will
- * be synchronized.
+ * Send updates to the remote MDT. Prepare the request by osp_update_req
+ * and send them to remote MDT, for sync request, it will wait
+ * until the reply return, otherwise hand it to ptlrpcd.
  *
  * Please refer to osp_trans_create() for transaction type.
  *
  * \param[in] env              pointer to the thread context
  * \param[in] osp              pointer to the OSP device
- * \param[in] dt_update                pointer to the dt_update_request
- * \param[in] th               pointer to the transaction handler
- * \param[in] flow_control     whether need to control the flow
+ * \param[in] our              pointer to the osp_update_request
  *
  * \retval                     0 for success
  * \retval                     negative error number on failure
  */
-static int osp_trans_trigger(const struct lu_env *env, struct osp_device *osp,
-                            struct dt_update_request *dt_update,
-                            struct thandle *th, bool flow_control)
+static int osp_send_update_req(const struct lu_env *env,
+                              struct osp_device *osp,
+                              struct osp_update_request *our)
 {
-       struct thandle_update   *tu = th->th_update;
-       int                      rc = 0;
+       struct osp_update_args  *args;
+       struct ptlrpc_request   *req;
+       struct lu_device *top_device;
+       struct osp_thandle      *oth = our->our_th;
+       int     rc = 0;
+       ENTRY;
 
-       LASSERT(tu != NULL);
-
-       if (is_only_remote_trans(th)) {
-               struct osp_async_update_args    *args;
-               struct ptlrpc_request           *req;
-
-               list_del_init(&dt_update->dur_list);
-               rc = out_prep_update_req(env, osp->opd_obd->u.cli.cl_import,
-                                        dt_update->dur_req, &req);
-               if (rc == 0) {
-                       args = ptlrpc_req_async_args(req);
-                       args->oaua_update = dt_update;
-                       args->oaua_flow_control = flow_control;
-                       req->rq_interpret_reply =
-                               osp_async_update_interpret;
-                       ptlrpcd_add_req(req, PDL_POLICY_LOCAL, -1);
-               } else {
-                       out_destroy_update_req(dt_update);
+       LASSERT(oth != NULL);
+       LASSERT(our->our_req_sent == 0);
+       rc = osp_prep_update_req(env, osp->opd_obd->u.cli.cl_import,
+                                our, &req);
+       if (rc != 0) {
+               osp_trans_callback(env, oth, rc);
+               RETURN(rc);
+       }
+
+       args = ptlrpc_req_async_args(req);
+       args->oaua_update = our;
+       osp_thandle_get(oth); /* hold for update interpret */
+       req->rq_interpret_reply = osp_update_interpret;
+       if (!oth->ot_super.th_wait_submit && !oth->ot_super.th_sync) {
+               if (!osp->opd_imp_active || !osp->opd_imp_connected) {
+                       osp_trans_callback(env, oth, rc);
+                       osp_thandle_put(oth);
+                       GOTO(out, rc = -ENOTCONN);
+               }
+
+               rc = obd_get_request_slot(&osp->opd_obd->u.cli);
+               if (rc != 0) {
+                       osp_trans_callback(env, oth, rc);
+                       osp_thandle_put(oth);
+                       GOTO(out, rc = -ENOTCONN);
                }
+               args->oaua_flow_control = true;
+
+               if (!osp->opd_connect_mdt) {
+                       down_read(&osp->opd_async_updates_rwsem);
+                       args->oaua_count = &osp->opd_async_updates_count;
+                       args->oaua_waitq = &osp->opd_syn_barrier_waitq;
+                       up_read(&osp->opd_async_updates_rwsem);
+                       atomic_inc(args->oaua_count);
+               }
+
+               ptlrpcd_add_req(req);
+               req = NULL;
        } else {
-               th->th_sync = 1;
-               rc = out_remote_sync(env, osp->opd_obd->u.cli.cl_import,
-                                    dt_update, NULL);
+               osp_thandle_get(oth); /* hold for commit callback */
+               req->rq_commit_cb = osp_request_commit_cb;
+               req->rq_cb_data = &oth->ot_super;
+               args->oaua_flow_control = false;
+
+               /* If the transaction is created during MDT recoverying
+                * process, it means this is an recovery update, we need
+                * to let OSP send it anyway without checking recoverying
+                * status, in case the other target is being recoveried
+                * at the same time, and if we wait here for the import
+                * to be recoveryed, it might cause deadlock */
+               top_device = osp->opd_dt_dev.dd_lu_dev.ld_site->ls_top_dev;
+               if (top_device->ld_obd->obd_recovering)
+                       req->rq_allow_replay = 1;
+
+               if (osp->opd_connect_mdt)
+                       osp_get_rpc_lock(osp);
+               rc = ptlrpc_queue_wait(req);
+               if (osp->opd_connect_mdt)
+                       osp_put_rpc_lock(osp);
+               if ((rc == -ENOMEM && req->rq_set == NULL) ||
+                   (req->rq_transno == 0 && !req->rq_committed)) {
+                       if (args->oaua_update != NULL) {
+                               /* If osp_update_interpret is not being called,
+                                * release the osp_thandle */
+                               args->oaua_update = NULL;
+                               osp_thandle_put(oth);
+                       }
+
+                       req->rq_cb_data = NULL;
+                       rc = rc == 0 ? req->rq_status : rc;
+                       osp_trans_callback(env, oth, rc);
+                       osp_thandle_put(oth);
+                       GOTO(out, rc);
+               }
        }
+out:
+       if (req != NULL)
+               ptlrpc_req_finished(req);
 
-       return rc;
+       RETURN(rc);
 }
 
 /**
- * The OSP layer dt_device_operations::dt_trans_start() interface
- * to start the transaction.
+ * Get local thandle for osp_thandle
  *
- * If the transaction is a remote transaction, then related remote
- * updates will be triggered in the osp_trans_stop(); otherwise the
- * transaction contains both local and remote update(s), then when
- * the OUT RPC will be triggered depends on the operation, and is
- * indicated by the dt_device::tu_sent_after_local_trans, for example:
+ * Get the local OSD thandle from the OSP thandle. Currently, there
+ * are a few OSP API (osp_object_create() and osp_sync_add()) needs
+ * to update the object on local OSD device.
+ *
+ * If the osp_thandle comes from normal stack (MDD->LOD->OSP), then
+ * we will get local thandle by thandle_get_sub_by_dt.
+ *
+ * If the osp_thandle is remote thandle (th_top == NULL, only used
+ * by LFSCK), then it will create a local thandle, and stop it in
+ * osp_trans_stop(). And this only happens on OSP for OST.
  *
- * 1) If it is remote create, it will send the remote req after local
- * transaction. i.e. create the object locally first, then insert the
- * remote name entry.
+ * These are temporary solution, once OSP accessing OSD object is
+ * being fixed properly, this function should be removed. XXX
+ *
+ * \param[in] env              pointer to the thread context
+ * \param[in] th               pointer to the transaction handler
+ * \param[in] dt               pointer to the OSP device
  *
- * 2) If it is remote unlink, it will send the remote req before the
- * local transaction, i.e. delete the name entry remotely first, then
- * destroy the local object.
+ * \retval                     pointer to the local thandle
+ * \retval                     ERR_PTR(errno) if it fails.
+ **/
+struct thandle *osp_get_storage_thandle(const struct lu_env *env,
+                                       struct thandle *th,
+                                       struct osp_device *osp)
+{
+       struct osp_thandle      *oth;
+       struct thandle          *local_th;
+
+       if (th->th_top != NULL)
+               return thandle_get_sub_by_dt(env, th->th_top,
+                                            osp->opd_storage);
+
+       LASSERT(!osp->opd_connect_mdt);
+       oth = thandle_to_osp_thandle(th);
+       if (oth->ot_storage_th != NULL)
+               return oth->ot_storage_th;
+
+       local_th = dt_trans_create(env, osp->opd_storage);
+       if (IS_ERR(local_th))
+               return local_th;
+
+       oth->ot_storage_th = local_th;
+
+       return local_th;
+}
+
+/**
+ * Set version for the transaction
+ *
+ * Set the version for the transaction, then the osp RPC will be
+ * sent in the order of version, i.e. the transaction with lower
+ * version will be sent first.
+ *
+ * \param [in] oth     osp thandle to be set version.
+ *
+ * \retval             0 if set version succeeds
+ *                      negative errno if set version fails.
+ */
+int osp_check_and_set_rpc_version(struct osp_thandle *oth)
+{
+       struct osp_device *osp = dt2osp_dev(oth->ot_super.th_dev);
+       struct osp_updates *ou = osp->opd_update;
+
+       if (ou == NULL)
+               return -EIO;
+
+       if (oth->ot_version != 0)
+               return 0;
+
+       spin_lock(&ou->ou_lock);
+       oth->ot_version = ou->ou_version++;
+       spin_unlock(&ou->ou_lock);
+
+       CDEBUG(D_INFO, "%s: version "LPU64" oth:version %p:"LPU64"\n",
+              osp->opd_obd->obd_name, ou->ou_version, oth, oth->ot_version);
+
+       return 0;
+}
+
+/**
+ * Get next OSP update request in the sending list
+ * Get next OSP update request in the sending list by version number, next
+ * request will be
+ * 1. transaction which does not have a version number.
+ * 2. transaction whose version == opd_rpc_version.
  *
+ * \param [in] ou      osp update structure.
+ * \param [out] ourp   the pointer holding the next update request.
+ *
+ * \retval             true if getting the next transaction.
+ * \retval             false if not getting the next transaction.
+ */
+static bool
+osp_get_next_request(struct osp_updates *ou, struct osp_update_request **ourp)
+{
+       struct osp_update_request *our;
+       struct osp_update_request *tmp;
+       bool                    got_req = false;
+
+       spin_lock(&ou->ou_lock);
+       list_for_each_entry_safe(our, tmp, &ou->ou_list, our_list) {
+               LASSERT(our->our_th != NULL);
+               CDEBUG(D_INFO, "our %p version "LPU64" rpc_version "LPU64"\n",
+                      our, our->our_th->ot_version, ou->ou_rpc_version);
+               if (our->our_th->ot_version == 0) {
+                       list_del_init(&our->our_list);
+                       *ourp = our;
+                       got_req = true;
+                       break;
+               }
+
+               /* Find next osp_update_request in the list */
+               if (our->our_th->ot_version == ou->ou_rpc_version) {
+                       list_del_init(&our->our_list);
+                       *ourp = our;
+                       got_req = true;
+                       break;
+               }
+       }
+       spin_unlock(&ou->ou_lock);
+
+       return got_req;
+}
+
+static void osp_update_rpc_version(struct osp_updates *ou,
+                                  struct osp_thandle *oth)
+{
+       if (oth->ot_version == 0)
+               return;
+
+       LASSERT(oth->ot_version == ou->ou_rpc_version);
+       spin_lock(&ou->ou_lock);
+       ou->ou_rpc_version++;
+       spin_unlock(&ou->ou_lock);
+}
+
+/**
+ * Sending update thread
+ *
+ * Create thread to send update request to other MDTs, this thread will pull
+ * out update request from the list in OSP by version number, i.e. it will
+ * make sure the update request with lower version number will be sent first.
+ *
+ * \param[in] arg      hold the OSP device.
+ *
+ * \retval             0 if the thread is created successfully.
+ * \retal              negative error if the thread is not created
+ *                      successfully.
+ */
+int osp_send_update_thread(void *arg)
+{
+       struct lu_env           env;
+       struct osp_device       *osp = arg;
+       struct l_wait_info       lwi = { 0 };
+       struct osp_updates      *ou = osp->opd_update;
+       struct ptlrpc_thread    *thread = &osp->opd_update_thread;
+       struct osp_update_request *our = NULL;
+       int                     rc;
+       ENTRY;
+
+       LASSERT(ou != NULL);
+       rc = lu_env_init(&env, osp->opd_dt_dev.dd_lu_dev.ld_type->ldt_ctx_tags);
+       if (rc < 0) {
+               CERROR("%s: init env error: rc = %d\n", osp->opd_obd->obd_name,
+                      rc);
+               RETURN(rc);
+       }
+
+       thread->t_flags = SVC_RUNNING;
+       wake_up(&thread->t_ctl_waitq);
+       while (1) {
+               our = NULL;
+               l_wait_event(ou->ou_waitq,
+                            !osp_send_update_thread_running(osp) ||
+                            osp_get_next_request(ou, &our),
+                            &lwi);
+
+               if (!osp_send_update_thread_running(osp)) {
+                       if (our != NULL && our->our_th != NULL) {
+                               osp_trans_callback(&env, our->our_th, -EINTR);
+                               osp_thandle_put(our->our_th);
+                       }
+                       break;
+               }
+
+               if (our->our_req_sent == 0) {
+                       if (our->our_th != NULL &&
+                           our->our_th->ot_super.th_result != 0)
+                               osp_trans_callback(&env, our->our_th,
+                                       our->our_th->ot_super.th_result);
+                       else
+                               rc = osp_send_update_req(&env, osp, our);
+               }
+
+               if (our->our_th != NULL) {
+                       /* Update the rpc version */
+                       osp_update_rpc_version(ou, our->our_th);
+                       /* Balanced for thandle_get in osp_trans_trigger() */
+                       osp_thandle_put(our->our_th);
+               }
+       }
+
+       thread->t_flags = SVC_STOPPED;
+       lu_env_fini(&env);
+       wake_up(&thread->t_ctl_waitq);
+
+       RETURN(0);
+}
+
+/**
+ * Trigger the request for remote updates.
+ *
+ * Add the request to the sending list, and wake up osp update
+ * sending thread.
+ *
+ * \param[in] env              pointer to the thread context
+ * \param[in] osp              pointer to the OSP device
+ * \param[in] oth              pointer to the transaction handler
+ *
+ */
+static void osp_trans_trigger(const struct lu_env *env,
+                            struct osp_device *osp,
+                            struct osp_thandle *oth)
+{
+
+       CDEBUG(D_INFO, "%s: add oth %p with version "LPU64"\n",
+              osp->opd_obd->obd_name, oth, oth->ot_version);
+
+       LASSERT(oth->ot_magic == OSP_THANDLE_MAGIC);
+       osp_thandle_get(oth);
+       LASSERT(oth->ot_our != NULL);
+       spin_lock(&osp->opd_update->ou_lock);
+       list_add_tail(&oth->ot_our->our_list,
+                     &osp->opd_update->ou_list);
+       spin_unlock(&osp->opd_update->ou_lock);
+
+       wake_up(&osp->opd_update->ou_waitq);
+}
+
+/**
+ * The OSP layer dt_device_operations::dt_trans_start() interface
+ * to start the transaction.
+ *
+ * If the transaction is a remote transaction, then related remote
+ * updates will be triggered in the osp_trans_stop().
  * Please refer to osp_trans_create() for transaction type.
  *
  * \param[in] env              pointer to the thread context
@@ -492,31 +1270,22 @@ static int osp_trans_trigger(const struct lu_env *env, struct osp_device *osp,
 int osp_trans_start(const struct lu_env *env, struct dt_device *dt,
                    struct thandle *th)
 {
-       struct thandle_update           *tu = th->th_update;
-       struct dt_update_request        *dt_update;
-       int                              rc = 0;
-
-       if (tu == NULL)
-               return rc;
-
-       /* Check whether there are updates related with this OSP */
-       dt_update = out_find_update(tu, dt);
-       if (dt_update == NULL)
-               return rc;
-
-       if (!is_only_remote_trans(th) && !tu->tu_sent_after_local_trans)
-               rc = osp_trans_trigger(env, dt2osp_dev(dt), dt_update, th,
-                                      false);
-
-       return rc;
+       struct osp_thandle      *oth = thandle_to_osp_thandle(th);
+
+       if (oth->ot_super.th_sync)
+               oth->ot_our->our_flags |= UPDATE_FL_SYNC;
+       /* For remote thandle, if there are local thandle, start it here*/
+       if (is_only_remote_trans(th) && oth->ot_storage_th != NULL)
+               return dt_trans_start(env, oth->ot_storage_th->th_dev,
+                                     oth->ot_storage_th);
+       return 0;
 }
 
 /**
  * The OSP layer dt_device_operations::dt_trans_stop() interface
  * to stop the transaction.
  *
- * If the transaction is a remote transaction, or the update handler
- * is marked as 'tu_sent_after_local_trans', then related remote
+ * If the transaction is a remote transaction, related remote
  * updates will be triggered here via osp_trans_trigger().
  *
  * For synchronous mode update or any failed update, the request
@@ -534,61 +1303,50 @@ int osp_trans_start(const struct lu_env *env, struct dt_device *dt,
 int osp_trans_stop(const struct lu_env *env, struct dt_device *dt,
                   struct thandle *th)
 {
-       struct thandle_update           *tu = th->th_update;
-       struct dt_update_request        *dt_update;
-       int                              rc = 0;
-
-       LASSERT(tu != NULL);
-       LASSERT(tu != LP_POISON);
+       struct osp_thandle       *oth = thandle_to_osp_thandle(th);
+       struct osp_update_request *our = oth->ot_our;
+       struct osp_device        *osp = dt2osp_dev(dt);
+       int                      rc = 0;
+       ENTRY;
 
-       /* Check whether there are updates related with this OSP */
-       dt_update = out_find_update(tu, dt);
-       if (dt_update == NULL) {
-               if (!is_only_remote_trans(th))
-                       return rc;
-               goto put;
+       /* For remote transaction, if there is local storage thandle,
+        * stop it first */
+       if (oth->ot_storage_th != NULL && th->th_top == NULL) {
+               dt_trans_stop(env, oth->ot_storage_th->th_dev,
+                             oth->ot_storage_th);
+               oth->ot_storage_th = NULL;
        }
 
-       if (dt_update->dur_req->ourq_count == 0) {
-               out_destroy_update_req(dt_update);
-               goto put;
+       if (our == NULL || list_empty(&our->our_req_list)) {
+               osp_trans_callback(env, oth, th->th_result);
+               GOTO(out, rc = th->th_result);
        }
 
-       if (is_only_remote_trans(th)) {
-               if (th->th_result == 0) {
-                       struct osp_device *osp = dt2osp_dev(th->th_dev);
-                       struct client_obd *cli = &osp->opd_obd->u.cli;
-
-                       rc = obd_get_request_slot(cli);
-                       if (!osp->opd_imp_active || osp->opd_got_disconnected) {
-                               if (rc == 0)
-                                       obd_put_request_slot(cli);
-
-                               rc = -ENOTCONN;
-                       }
+       if (!osp->opd_connect_mdt) {
+               osp_trans_callback(env, oth, th->th_result);
+               rc = osp_send_update_req(env, osp, oth->ot_our);
+               GOTO(out, rc);
+       }
 
-                       if (rc != 0) {
-                               out_destroy_update_req(dt_update);
-                               goto put;
-                       }
+       if (osp->opd_update == NULL ||
+           !osp_send_update_thread_running(osp)) {
+               osp_trans_callback(env, oth, -EIO);
+               GOTO(out, rc = -EIO);
+       }
 
-                       rc = osp_trans_trigger(env, dt2osp_dev(dt),
-                                              dt_update, th, true);
-                       if (rc != 0)
-                               obd_put_request_slot(cli);
-               } else {
-                       rc = th->th_result;
-                       out_destroy_update_req(dt_update);
-               }
-       } else {
-               if (tu->tu_sent_after_local_trans)
-                       rc = osp_trans_trigger(env, dt2osp_dev(dt),
-                                              dt_update, th, false);
-               rc = dt_update->dur_rc;
-               out_destroy_update_req(dt_update);
+       if (th->th_sync) {
+               /* if th_sync is set, then it needs to be sent
+                * right away. Note: even thought the RPC has been
+                * sent, it still needs to be added to the sending
+                * list (see osp_trans_trigger()), so ou_rpc_version
+                * can be updated correctly. */
+               rc = osp_send_update_req(env, osp, our);
+               our->our_req_sent = 1;
        }
 
-put:
-       thandle_put(th);
-       return rc;
+       osp_trans_trigger(env, osp, oth);
+out:
+       osp_thandle_put(oth);
+
+       RETURN(rc);
 }