text: /*
   * 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) 2010, 2015, Intel Corporation.
   */
  /*
   * This file is part of Lustre, http://www.lustre.org/
   * Lustre is a trademark of Sun Microsystems, Inc.
   */
  /**
   * This file contains Asynchronous System Trap (AST) handlers and related
   * LDLM request-processing routines.
   *
   * An AST is a callback issued on a lock when its state is changed. There are
   * several different types of ASTs (callbacks) registered for each lock:
   *
   * - completion AST: when a lock is enqueued by some process, but cannot be
   *   granted immediately due to other conflicting locks on the same resource,
   *   the completion AST is sent to notify the caller when the lock is
   *   eventually granted
   *
   * - blocking AST: when a lock is granted to some process, if another process
   *   enqueues a conflicting (blocking) lock on a resource, a blocking AST is
   *   sent to notify the holder(s) of the lock(s) of the conflicting lock
   *   request. The lock holder(s) must release their lock(s) on that resource in
   *   a timely manner or be evicted by the server.
   *
   * - glimpse AST: this is used when a process wants information about a lock
   *   (i.e. the lock value block (LVB)) but does not necessarily require holding
   *   the lock. If the resource is locked, the lock holder(s) are sent glimpse
   *   ASTs and the LVB is returned to the caller, and lock holder(s) may CANCEL
   *   their lock(s) if they are idle. If the resource is not locked, the server
   *   may grant the lock.
   */
  
  #define DEBUG_SUBSYSTEM S_LDLM
  
  #include "../include/lustre_dlm.h"
  #include "../include/obd_class.h"
  #include "../include/obd.h"
  
  #include "ldlm_internal.h"
  
  unsigned int ldlm_enqueue_min = OBD_TIMEOUT_DEFAULT;
  module_param(ldlm_enqueue_min, uint, 0644);
  MODULE_PARM_DESC(ldlm_enqueue_min, "lock enqueue timeout minimum");
  
  /* in client side, whether the cached locks will be canceled before replay */
  unsigned int ldlm_cancel_unused_locks_before_replay = 1;
  
  static void interrupted_completion_wait(void *data)
  {
  }
  
  struct lock_wait_data {
  	struct ldlm_lock *lwd_lock;
  	__u32	     lwd_conn_cnt;
  };
  
  struct ldlm_async_args {
  	struct lustre_handle lock_handle;
  };
  
  static int ldlm_expired_completion_wait(void *data)
  {
  	struct lock_wait_data *lwd = data;
  	struct ldlm_lock *lock = lwd->lwd_lock;
  	struct obd_import *imp;
  	struct obd_device *obd;
  
  	if (!lock->l_conn_export) {
  		static unsigned long next_dump, last_dump;
  
  		LCONSOLE_WARN("lock timed out (enqueued at %lld, %llds ago)\n",
  			      (s64)lock->l_last_activity,
  			      (s64)(ktime_get_real_seconds() -
  				    lock->l_last_activity));
  		LDLM_DEBUG(lock, "lock timed out (enqueued at %lld, %llds ago); not entering recovery in server code, just going back to sleep",
  			   (s64)lock->l_last_activity,
  			   (s64)(ktime_get_real_seconds() -
  				 lock->l_last_activity));
  		if (cfs_time_after(cfs_time_current(), next_dump)) {
  			last_dump = next_dump;
  			next_dump = cfs_time_shift(300);
  			ldlm_namespace_dump(D_DLMTRACE,
  					    ldlm_lock_to_ns(lock));
  			if (last_dump == 0)
  				libcfs_debug_dumplog();
  		}
  		return 0;
  	}
  
  	obd = lock->l_conn_export->exp_obd;
  	imp = obd->u.cli.cl_import;
  	ptlrpc_fail_import(imp, lwd->lwd_conn_cnt);
  	LDLM_ERROR(lock, "lock timed out (enqueued at %lld, %llds ago), entering recovery for %s@%s",
  		   (s64)lock->l_last_activity,
  		   (s64)(ktime_get_real_seconds() - lock->l_last_activity),
  		   obd2cli_tgt(obd), imp->imp_connection->c_remote_uuid.uuid);
  
  	return 0;
  }
  
  /**
   * Calculate the Completion timeout (covering enqueue, BL AST, data flush,
   * lock cancel, and their replies). Used for lock completion timeout on the
   * client side.
   *
   * \param[in] lock	lock which is waiting the completion callback
   *
   * \retval		timeout in seconds to wait for the server reply
   */
  /* We use the same basis for both server side and client side functions
   * from a single node.
   */
  static unsigned int ldlm_cp_timeout(struct ldlm_lock *lock)
  {
  	unsigned int timeout;
  
  	if (AT_OFF)
  		return obd_timeout;
  
  	/*
  	 * Wait a long time for enqueue - server may have to callback a
  	 * lock from another client.  Server will evict the other client if it
  	 * doesn't respond reasonably, and then give us the lock.
  	 */
  	timeout = at_get(ldlm_lock_to_ns_at(lock));
  	return max(3 * timeout, ldlm_enqueue_min);
  }
  
  /**
   * Helper function for ldlm_completion_ast(), updating timings when lock is
   * actually granted.
   */
  static int ldlm_completion_tail(struct ldlm_lock *lock, void *data)
  {
  	long delay;
  	int result = 0;
  
  	if (ldlm_is_destroyed(lock) || ldlm_is_failed(lock)) {
  		LDLM_DEBUG(lock, "client-side enqueue: destroyed");
  		result = -EIO;
  	} else if (!data) {
  		LDLM_DEBUG(lock, "client-side enqueue: granted");
  	} else {
  		/* Take into AT only CP RPC, not immediately granted locks */
  		delay = ktime_get_real_seconds() - lock->l_last_activity;
  		LDLM_DEBUG(lock, "client-side enqueue: granted after %lds",
  			   delay);
  
  		/* Update our time estimate */
  		at_measured(ldlm_lock_to_ns_at(lock), delay);
  	}
  	return result;
  }
  
  /**
   * Implementation of ->l_completion_ast() for a client, that doesn't wait
   * until lock is granted. Suitable for locks enqueued through ptlrpcd, of
   * other threads that cannot block for long.
   */
  int ldlm_completion_ast_async(struct ldlm_lock *lock, __u64 flags, void *data)
  {
  	if (flags == LDLM_FL_WAIT_NOREPROC) {
  		LDLM_DEBUG(lock, "client-side enqueue waiting on pending lock");
  		return 0;
  	}
  
  	if (!(flags & LDLM_FL_BLOCKED_MASK)) {
  		wake_up(&lock->l_waitq);
  		return ldlm_completion_tail(lock, data);
  	}
  
  	LDLM_DEBUG(lock, "client-side enqueue returned a blocked lock, going forward");
  	return 0;
  }
  EXPORT_SYMBOL(ldlm_completion_ast_async);
  
  /**
   * Generic LDLM "completion" AST. This is called in several cases:
   *
   *     - when a reply to an ENQUEUE RPC is received from the server
   *       (ldlm_cli_enqueue_fini()). Lock might be granted or not granted at
   *       this point (determined by flags);
   *
   *     - when LDLM_CP_CALLBACK RPC comes to client to notify it that lock has
   *       been granted;
   *
   *     - when ldlm_lock_match(LDLM_FL_LVB_READY) is about to wait until lock
   *       gets correct lvb;
   *
   *     - to force all locks when resource is destroyed (cleanup_resource());
   *
   *     - during lock conversion (not used currently).
   *
   * If lock is not granted in the first case, this function waits until second
   * or penultimate cases happen in some other thread.
   *
   */
  int ldlm_completion_ast(struct ldlm_lock *lock, __u64 flags, void *data)
  {
  	/* XXX ALLOCATE - 160 bytes */
  	struct lock_wait_data lwd;
  	struct obd_device *obd;
  	struct obd_import *imp = NULL;
  	struct l_wait_info lwi;
  	__u32 timeout;
  	int rc = 0;
  
  	if (flags == LDLM_FL_WAIT_NOREPROC) {
  		LDLM_DEBUG(lock, "client-side enqueue waiting on pending lock");
  		goto noreproc;
  	}
  
  	if (!(flags & LDLM_FL_BLOCKED_MASK)) {
  		wake_up(&lock->l_waitq);
  		return 0;
  	}
  
  	LDLM_DEBUG(lock, "client-side enqueue returned a blocked lock, sleeping");
  
  noreproc:
  
  	obd = class_exp2obd(lock->l_conn_export);
  
  	/* if this is a local lock, then there is no import */
  	if (obd)
  		imp = obd->u.cli.cl_import;
  
  	timeout = ldlm_cp_timeout(lock);
  
  	lwd.lwd_lock = lock;
  	lock->l_last_activity = ktime_get_real_seconds();
  
  	if (ldlm_is_no_timeout(lock)) {
  		LDLM_DEBUG(lock, "waiting indefinitely because of NO_TIMEOUT");
  		lwi = LWI_INTR(interrupted_completion_wait, &lwd);
  	} else {
  		lwi = LWI_TIMEOUT_INTR(cfs_time_seconds(timeout),
  				       ldlm_expired_completion_wait,
  				       interrupted_completion_wait, &lwd);
  	}
  
  	if (imp) {
  		spin_lock(&imp->imp_lock);
  		lwd.lwd_conn_cnt = imp->imp_conn_cnt;
  		spin_unlock(&imp->imp_lock);
  	}
  
  	if (OBD_FAIL_CHECK_RESET(OBD_FAIL_LDLM_INTR_CP_AST,
  				 OBD_FAIL_LDLM_CP_BL_RACE | OBD_FAIL_ONCE)) {
  		ldlm_set_fail_loc(lock);
  		rc = -EINTR;
  	} else {
  		/* Go to sleep until the lock is granted or cancelled. */
  		rc = l_wait_event(lock->l_waitq,
  				  is_granted_or_cancelled(lock), &lwi);
  	}
  
  	if (rc) {
  		LDLM_DEBUG(lock, "client-side enqueue waking up: failed (%d)",
  			   rc);
  		return rc;
  	}
  
  	return ldlm_completion_tail(lock, data);
  }
  EXPORT_SYMBOL(ldlm_completion_ast);
  
  static void failed_lock_cleanup(struct ldlm_namespace *ns,
  				struct ldlm_lock *lock, int mode)
  {
  	int need_cancel = 0;
  
  	/* Set a flag to prevent us from sending a CANCEL (bug 407) */
  	lock_res_and_lock(lock);
  	/* Check that lock is not granted or failed, we might race. */
  	if ((lock->l_req_mode != lock->l_granted_mode) &&
  	    !ldlm_is_failed(lock)) {
  		/* Make sure that this lock will not be found by raced
  		 * bl_ast and -EINVAL reply is sent to server anyways.
  		 * bug 17645
  		 */
  		lock->l_flags |= LDLM_FL_LOCAL_ONLY | LDLM_FL_FAILED |
  				 LDLM_FL_ATOMIC_CB | LDLM_FL_CBPENDING;
  		need_cancel = 1;
  	}
  	unlock_res_and_lock(lock);
  
  	if (need_cancel)
  		LDLM_DEBUG(lock,
  			   "setting FL_LOCAL_ONLY | LDLM_FL_FAILED | LDLM_FL_ATOMIC_CB | LDLM_FL_CBPENDING");
  	else
  		LDLM_DEBUG(lock, "lock was granted or failed in race");
  
  	/* XXX - HACK because we shouldn't call ldlm_lock_destroy()
  	 *       from llite/file.c/ll_file_flock().
  	 */
  	/* This code makes for the fact that we do not have blocking handler on
  	 * a client for flock locks. As such this is the place where we must
  	 * completely kill failed locks. (interrupted and those that
  	 * were waiting to be granted when server evicted us.
  	 */
  	if (lock->l_resource->lr_type == LDLM_FLOCK) {
  		lock_res_and_lock(lock);
  		if (!ldlm_is_destroyed(lock)) {
  			ldlm_resource_unlink_lock(lock);
  			ldlm_lock_decref_internal_nolock(lock, mode);
  			ldlm_lock_destroy_nolock(lock);
  		}
  		unlock_res_and_lock(lock);
  	} else {
  		ldlm_lock_decref_internal(lock, mode);
  	}
  }
  
  /**
   * Finishing portion of client lock enqueue code.
   *
   * Called after receiving reply from server.
   */
  int ldlm_cli_enqueue_fini(struct obd_export *exp, struct ptlrpc_request *req,
  			  enum ldlm_type type, __u8 with_policy,
  			  enum ldlm_mode mode,
  			  __u64 *flags, void *lvb, __u32 lvb_len,
  			  const struct lustre_handle *lockh, int rc)
  {
  	struct ldlm_namespace *ns = exp->exp_obd->obd_namespace;
  	int is_replay = *flags & LDLM_FL_REPLAY;
  	struct ldlm_lock *lock;
  	struct ldlm_reply *reply;
  	int cleanup_phase = 1;
  
  	lock = ldlm_handle2lock(lockh);
  	/* ldlm_cli_enqueue is holding a reference on this lock. */
  	if (!lock) {
  		LASSERT(type == LDLM_FLOCK);
  		return -ENOLCK;
  	}
  
  	LASSERTF(ergo(lvb_len != 0, lvb_len == lock->l_lvb_len),
  		 "lvb_len = %d, l_lvb_len = %d\n", lvb_len, lock->l_lvb_len);
  
  	if (rc != ELDLM_OK) {
  		LASSERT(!is_replay);
  		LDLM_DEBUG(lock, "client-side enqueue END (%s)",
  			   rc == ELDLM_LOCK_ABORTED ? "ABORTED" : "FAILED");
  
  		if (rc != ELDLM_LOCK_ABORTED)
  			goto cleanup;
  	}
  
  	/* Before we return, swab the reply */
  	reply = req_capsule_server_get(&req->rq_pill, &RMF_DLM_REP);
  	if (!reply) {
  		rc = -EPROTO;
  		goto cleanup;
  	}
  
  	if (lvb_len > 0) {
  		int size = 0;
  
  		size = req_capsule_get_size(&req->rq_pill, &RMF_DLM_LVB,
  					    RCL_SERVER);
  		if (size < 0) {
  			LDLM_ERROR(lock, "Fail to get lvb_len, rc = %d", size);
  			rc = size;
  			goto cleanup;
  		} else if (unlikely(size > lvb_len)) {
  			LDLM_ERROR(lock, "Replied LVB is larger than expectation, expected = %d, replied = %d",
  				   lvb_len, size);
  			rc = -EINVAL;
  			goto cleanup;
  		}
  		lvb_len = size;
  	}
  
  	if (rc == ELDLM_LOCK_ABORTED) {
  		if (lvb_len > 0 && lvb)
  			rc = ldlm_fill_lvb(lock, &req->rq_pill, RCL_SERVER,
  					   lvb, lvb_len);
  		if (rc == 0)
  			rc = ELDLM_LOCK_ABORTED;
  		goto cleanup;
  	}
  
  	/* lock enqueued on the server */
  	cleanup_phase = 0;
  
  	lock_res_and_lock(lock);
  	/* Key change rehash lock in per-export hash with new key */
  	if (exp->exp_lock_hash) {
  		/* In the function below, .hs_keycmp resolves to
  		 * ldlm_export_lock_keycmp()
  		 */
  		/* coverity[overrun-buffer-val] */
  		cfs_hash_rehash_key(exp->exp_lock_hash,
  				    &lock->l_remote_handle,
  				    &reply->lock_handle,
  				    &lock->l_exp_hash);
  	} else {
  		lock->l_remote_handle = reply->lock_handle;
  	}
  
  	*flags = ldlm_flags_from_wire(reply->lock_flags);
  	lock->l_flags |= ldlm_flags_from_wire(reply->lock_flags &
  					      LDLM_FL_INHERIT_MASK);
  	unlock_res_and_lock(lock);
  
  	CDEBUG(D_INFO, "local: %p, remote cookie: %#llx, flags: 0x%llx\n",
  	       lock, reply->lock_handle.cookie, *flags);
  
  	/* If enqueue returned a blocked lock but the completion handler has
  	 * already run, then it fixed up the resource and we don't need to do it
  	 * again.
  	 */
  	if ((*flags) & LDLM_FL_LOCK_CHANGED) {
  		int newmode = reply->lock_desc.l_req_mode;
  
  		LASSERT(!is_replay);
  		if (newmode && newmode != lock->l_req_mode) {
  			LDLM_DEBUG(lock, "server returned different mode %s",
  				   ldlm_lockname[newmode]);
  			lock->l_req_mode = newmode;
  		}
  
  		if (!ldlm_res_eq(&reply->lock_desc.l_resource.lr_name,
  				 &lock->l_resource->lr_name)) {
  			CDEBUG(D_INFO, "remote intent success, locking "DLDLMRES
  				       " instead of "DLDLMRES"\n",
  			       PLDLMRES(&reply->lock_desc.l_resource),
  			       PLDLMRES(lock->l_resource));
  
  			rc = ldlm_lock_change_resource(ns, lock,
  					&reply->lock_desc.l_resource.lr_name);
  			if (rc || !lock->l_resource) {
  				rc = -ENOMEM;
  				goto cleanup;
  			}
  			LDLM_DEBUG(lock, "client-side enqueue, new resource");
  		}
  		if (with_policy)
  			if (!(type == LDLM_IBITS &&
  			      !(exp_connect_flags(exp) & OBD_CONNECT_IBITS)))
  				/* We assume lock type cannot change on server*/
  				ldlm_convert_policy_to_local(exp,
  						lock->l_resource->lr_type,
  						&reply->lock_desc.l_policy_data,
  						&lock->l_policy_data);
  		if (type != LDLM_PLAIN)
  			LDLM_DEBUG(lock,
  				   "client-side enqueue, new policy data");
  	}
  
  	if ((*flags) & LDLM_FL_AST_SENT ||
  	    /* Cancel extent locks as soon as possible on a liblustre client,
  	     * because it cannot handle asynchronous ASTs robustly (see
  	     * bug 7311).
  	     */
  	    (LIBLUSTRE_CLIENT && type == LDLM_EXTENT)) {
  		lock_res_and_lock(lock);
  		lock->l_flags |= LDLM_FL_CBPENDING |  LDLM_FL_BL_AST;
  		unlock_res_and_lock(lock);
  		LDLM_DEBUG(lock, "enqueue reply includes blocking AST");
  	}
  
  	/* If the lock has already been granted by a completion AST, don't
  	 * clobber the LVB with an older one.
  	 */
  	if (lvb_len > 0) {
  		/* We must lock or a racing completion might update lvb without
  		 * letting us know and we'll clobber the correct value.
  		 * Cannot unlock after the check either, as that still leaves
  		 * a tiny window for completion to get in
  		 */
  		lock_res_and_lock(lock);
  		if (lock->l_req_mode != lock->l_granted_mode)
  			rc = ldlm_fill_lvb(lock, &req->rq_pill, RCL_SERVER,
  					   lock->l_lvb_data, lvb_len);
  		unlock_res_and_lock(lock);
  		if (rc < 0) {
  			cleanup_phase = 1;
  			goto cleanup;
  		}
  	}
  
  	if (!is_replay) {
  		rc = ldlm_lock_enqueue(ns, &lock, NULL, flags);
  		if (lock->l_completion_ast) {
  			int err = lock->l_completion_ast(lock, *flags, NULL);
  
  			if (!rc)
  				rc = err;
  			if (rc)
  				cleanup_phase = 1;
  		}
  	}
  
  	if (lvb_len > 0 && lvb) {
  		/* Copy the LVB here, and not earlier, because the completion
  		 * AST (if any) can override what we got in the reply
  		 */
  		memcpy(lvb, lock->l_lvb_data, lvb_len);
  	}
  
  	LDLM_DEBUG(lock, "client-side enqueue END");
  cleanup:
  	if (cleanup_phase == 1 && rc)
  		failed_lock_cleanup(ns, lock, mode);
  	/* Put lock 2 times, the second reference is held by ldlm_cli_enqueue */
  	LDLM_LOCK_PUT(lock);
  	LDLM_LOCK_RELEASE(lock);
  	return rc;
  }
  EXPORT_SYMBOL(ldlm_cli_enqueue_fini);
  
  /**
   * Estimate number of lock handles that would fit into request of given
   * size.  PAGE_SIZE-512 is to allow TCP/IP and LNET headers to fit into
   * a single page on the send/receive side. XXX: 512 should be changed to
   * more adequate value.
   */
  static inline int ldlm_req_handles_avail(int req_size, int off)
  {
  	int avail;
  
  	avail = min_t(int, LDLM_MAXREQSIZE, PAGE_SIZE - 512) - req_size;
  	if (likely(avail >= 0))
  		avail /= (int)sizeof(struct lustre_handle);
  	else
  		avail = 0;
  	avail += LDLM_LOCKREQ_HANDLES - off;
  
  	return avail;
  }
  
  static inline int ldlm_capsule_handles_avail(struct req_capsule *pill,
  					     enum req_location loc,
  					     int off)
  {
  	u32 size = req_capsule_msg_size(pill, loc);
  
  	return ldlm_req_handles_avail(size, off);
  }
  
  static inline int ldlm_format_handles_avail(struct obd_import *imp,
  					    const struct req_format *fmt,
  					    enum req_location loc, int off)
  {
  	u32 size = req_capsule_fmt_size(imp->imp_msg_magic, fmt, loc);
  
  	return ldlm_req_handles_avail(size, off);
  }
  
  /**
   * Cancel LRU locks and pack them into the enqueue request. Pack there the given
   * \a count locks in \a cancels.
   *
   * This is to be called by functions preparing their own requests that
   * might contain lists of locks to cancel in addition to actual operation
   * that needs to be performed.
   */
  int ldlm_prep_elc_req(struct obd_export *exp, struct ptlrpc_request *req,
  		      int version, int opc, int canceloff,
  		      struct list_head *cancels, int count)
  {
  	struct ldlm_namespace   *ns = exp->exp_obd->obd_namespace;
  	struct req_capsule      *pill = &req->rq_pill;
  	struct ldlm_request     *dlm = NULL;
  	int flags, avail, to_free, pack = 0;
  	LIST_HEAD(head);
  	int rc;
  
  	if (!cancels)
  		cancels = &head;
  	if (ns_connect_cancelset(ns)) {
  		/* Estimate the amount of available space in the request. */
  		req_capsule_filled_sizes(pill, RCL_CLIENT);
  		avail = ldlm_capsule_handles_avail(pill, RCL_CLIENT, canceloff);
  
  		flags = ns_connect_lru_resize(ns) ?
  			LDLM_CANCEL_LRUR_NO_WAIT : LDLM_CANCEL_AGED;
  		to_free = !ns_connect_lru_resize(ns) &&
  			  opc == LDLM_ENQUEUE ? 1 : 0;
  
  		/* Cancel LRU locks here _only_ if the server supports
  		 * EARLY_CANCEL. Otherwise we have to send extra CANCEL
  		 * RPC, which will make us slower.
  		 */
  		if (avail > count)
  			count += ldlm_cancel_lru_local(ns, cancels, to_free,
  						       avail - count, 0, flags);
  		if (avail > count)
  			pack = count;
  		else
  			pack = avail;
  		req_capsule_set_size(pill, &RMF_DLM_REQ, RCL_CLIENT,
  				     ldlm_request_bufsize(pack, opc));
  	}
  
  	rc = ptlrpc_request_pack(req, version, opc);
  	if (rc) {
  		ldlm_lock_list_put(cancels, l_bl_ast, count);
  		return rc;
  	}
  
  	if (ns_connect_cancelset(ns)) {
  		if (canceloff) {
  			dlm = req_capsule_client_get(pill, &RMF_DLM_REQ);
  			LASSERT(dlm);
  			/* Skip first lock handler in ldlm_request_pack(),
  			 * this method will increment @lock_count according
  			 * to the lock handle amount actually written to
  			 * the buffer.
  			 */
  			dlm->lock_count = canceloff;
  		}
  		/* Pack into the request @pack lock handles. */
  		ldlm_cli_cancel_list(cancels, pack, req, 0);
  		/* Prepare and send separate cancel RPC for others. */
  		ldlm_cli_cancel_list(cancels, count - pack, NULL, 0);
  	} else {
  		ldlm_lock_list_put(cancels, l_bl_ast, count);
  	}
  	return 0;
  }
  EXPORT_SYMBOL(ldlm_prep_elc_req);
  
  int ldlm_prep_enqueue_req(struct obd_export *exp, struct ptlrpc_request *req,
  			  struct list_head *cancels, int count)
  {
  	return ldlm_prep_elc_req(exp, req, LUSTRE_DLM_VERSION, LDLM_ENQUEUE,
  				 LDLM_ENQUEUE_CANCEL_OFF, cancels, count);
  }
  EXPORT_SYMBOL(ldlm_prep_enqueue_req);
  
  /**
   * Client-side lock enqueue.
   *
   * If a request has some specific initialisation it is passed in \a reqp,
   * otherwise it is created in ldlm_cli_enqueue.
   *
   * Supports sync and async requests, pass \a async flag accordingly. If a
   * request was created in ldlm_cli_enqueue and it is the async request,
   * pass it to the caller in \a reqp.
   */
  int ldlm_cli_enqueue(struct obd_export *exp, struct ptlrpc_request **reqp,
  		     struct ldlm_enqueue_info *einfo,
  		     const struct ldlm_res_id *res_id,
  		     ldlm_policy_data_t const *policy, __u64 *flags,
  		     void *lvb, __u32 lvb_len, enum lvb_type lvb_type,
  		     struct lustre_handle *lockh, int async)
  {
  	struct ldlm_namespace *ns;
  	struct ldlm_lock      *lock;
  	struct ldlm_request   *body;
  	int		    is_replay = *flags & LDLM_FL_REPLAY;
  	int		    req_passed_in = 1;
  	int		    rc, err;
  	struct ptlrpc_request *req;
  
  	ns = exp->exp_obd->obd_namespace;
  
  	/* If we're replaying this lock, just check some invariants.
  	 * If we're creating a new lock, get everything all setup nicely.
  	 */
  	if (is_replay) {
  		lock = ldlm_handle2lock_long(lockh, 0);
  		LASSERT(lock);
  		LDLM_DEBUG(lock, "client-side enqueue START");
  		LASSERT(exp == lock->l_conn_export);
  	} else {
  		const struct ldlm_callback_suite cbs = {
  			.lcs_completion = einfo->ei_cb_cp,
  			.lcs_blocking	= einfo->ei_cb_bl,
  			.lcs_glimpse	= einfo->ei_cb_gl
  		};
  		lock = ldlm_lock_create(ns, res_id, einfo->ei_type,
  					einfo->ei_mode, &cbs, einfo->ei_cbdata,
  					lvb_len, lvb_type);
  		if (IS_ERR(lock))
  			return PTR_ERR(lock);
  		/* for the local lock, add the reference */
  		ldlm_lock_addref_internal(lock, einfo->ei_mode);
  		ldlm_lock2handle(lock, lockh);
  		if (policy)
  			lock->l_policy_data = *policy;
  
  		if (einfo->ei_type == LDLM_EXTENT) {
  			/* extent lock without policy is a bug */
  			if (!policy)
  				LBUG();
  
  			lock->l_req_extent = policy->l_extent;
  		}
  		LDLM_DEBUG(lock, "client-side enqueue START, flags %llx",
  			   *flags);
  	}
  
  	lock->l_conn_export = exp;
  	lock->l_export = NULL;
  	lock->l_blocking_ast = einfo->ei_cb_bl;
  	lock->l_flags |= (*flags & (LDLM_FL_NO_LRU | LDLM_FL_EXCL));
  	lock->l_last_activity = ktime_get_real_seconds();
  
  	/* lock not sent to server yet */
  
  	if (!reqp || !*reqp) {
  		req = ptlrpc_request_alloc_pack(class_exp2cliimp(exp),
  						&RQF_LDLM_ENQUEUE,
  						LUSTRE_DLM_VERSION,
  						LDLM_ENQUEUE);
  		if (!req) {
  			failed_lock_cleanup(ns, lock, einfo->ei_mode);
  			LDLM_LOCK_RELEASE(lock);
  			return -ENOMEM;
  		}
  		req_passed_in = 0;
  		if (reqp)
  			*reqp = req;
  	} else {
  		int len;
  
  		req = *reqp;
  		len = req_capsule_get_size(&req->rq_pill, &RMF_DLM_REQ,
  					   RCL_CLIENT);
  		LASSERTF(len >= sizeof(*body), "buflen[%d] = %d, not %d\n",
  			 DLM_LOCKREQ_OFF, len, (int)sizeof(*body));
  	}
  
  	/* Dump lock data into the request buffer */
  	body = req_capsule_client_get(&req->rq_pill, &RMF_DLM_REQ);
  	ldlm_lock2desc(lock, &body->lock_desc);
  	body->lock_flags = ldlm_flags_to_wire(*flags);
  	body->lock_handle[0] = *lockh;
  
  	/* Continue as normal. */
  	if (!req_passed_in) {
  		if (lvb_len > 0)
  			req_capsule_extend(&req->rq_pill,
  					   &RQF_LDLM_ENQUEUE_LVB);
  		req_capsule_set_size(&req->rq_pill, &RMF_DLM_LVB, RCL_SERVER,
  				     lvb_len);
  		ptlrpc_request_set_replen(req);
  	}
  
  	/*
  	 * Liblustre client doesn't get extent locks, except for O_APPEND case
  	 * where [0, OBD_OBJECT_EOF] lock is taken, or truncate, where
  	 * [i_size, OBD_OBJECT_EOF] lock is taken.
  	 */
  	LASSERT(ergo(LIBLUSTRE_CLIENT, einfo->ei_type != LDLM_EXTENT ||
  		     policy->l_extent.end == OBD_OBJECT_EOF));
  
  	if (async) {
  		LASSERT(reqp);
  		return 0;
  	}
  
  	LDLM_DEBUG(lock, "sending request");
  
  	rc = ptlrpc_queue_wait(req);
  
  	err = ldlm_cli_enqueue_fini(exp, req, einfo->ei_type, policy ? 1 : 0,
  				    einfo->ei_mode, flags, lvb, lvb_len,
  				    lockh, rc);
  
  	/* If ldlm_cli_enqueue_fini did not find the lock, we need to free
  	 * one reference that we took
  	 */
  	if (err == -ENOLCK)
  		LDLM_LOCK_RELEASE(lock);
  	else
  		rc = err;
  
  	if (!req_passed_in && req) {
  		ptlrpc_req_finished(req);
  		if (reqp)
  			*reqp = NULL;
  	}
  
  	return rc;
  }
  EXPORT_SYMBOL(ldlm_cli_enqueue);
  
  /**
   * Cancel locks locally.
   * Returns:
   * \retval LDLM_FL_LOCAL_ONLY if there is no need for a CANCEL RPC to the server
   * \retval LDLM_FL_CANCELING otherwise;
   * \retval LDLM_FL_BL_AST if there is a need for a separate CANCEL RPC.
   */
  static __u64 ldlm_cli_cancel_local(struct ldlm_lock *lock)
  {
  	__u64 rc = LDLM_FL_LOCAL_ONLY;
  
  	if (lock->l_conn_export) {
  		bool local_only;
  
  		LDLM_DEBUG(lock, "client-side cancel");
  		/* Set this flag to prevent others from getting new references*/
  		lock_res_and_lock(lock);
  		ldlm_set_cbpending(lock);
  		local_only = !!(lock->l_flags &
  				(LDLM_FL_LOCAL_ONLY | LDLM_FL_CANCEL_ON_BLOCK));
  		ldlm_cancel_callback(lock);
  		rc = ldlm_is_bl_ast(lock) ? LDLM_FL_BL_AST : LDLM_FL_CANCELING;
  		unlock_res_and_lock(lock);
  
  		if (local_only) {
  			CDEBUG(D_DLMTRACE, "not sending request (at caller's instruction)\n");
  			rc = LDLM_FL_LOCAL_ONLY;
  		}
  		ldlm_lock_cancel(lock);
  	} else {
  		LDLM_ERROR(lock, "Trying to cancel local lock");
  		LBUG();
  	}
  
  	return rc;
  }
  
  /**
   * Pack \a count locks in \a head into ldlm_request buffer of request \a req.
   */
  static void ldlm_cancel_pack(struct ptlrpc_request *req,
  			     struct list_head *head, int count)
  {
  	struct ldlm_request *dlm;
  	struct ldlm_lock *lock;
  	int max, packed = 0;
  
  	dlm = req_capsule_client_get(&req->rq_pill, &RMF_DLM_REQ);
  	LASSERT(dlm);
  
  	/* Check the room in the request buffer. */
  	max = req_capsule_get_size(&req->rq_pill, &RMF_DLM_REQ, RCL_CLIENT) -
  		sizeof(struct ldlm_request);
  	max /= sizeof(struct lustre_handle);
  	max += LDLM_LOCKREQ_HANDLES;
  	LASSERT(max >= dlm->lock_count + count);
  
  	/* XXX: it would be better to pack lock handles grouped by resource.
  	 * so that the server cancel would call filter_lvbo_update() less
  	 * frequently.
  	 */
  	list_for_each_entry(lock, head, l_bl_ast) {
  		if (!count--)
  			break;
  		LASSERT(lock->l_conn_export);
  		/* Pack the lock handle to the given request buffer. */
  		LDLM_DEBUG(lock, "packing");
  		dlm->lock_handle[dlm->lock_count++] = lock->l_remote_handle;
  		packed++;
  	}
  	CDEBUG(D_DLMTRACE, "%d locks packed\n", packed);
  }
  
  /**
   * Prepare and send a batched cancel RPC. It will include \a count lock
   * handles of locks given in \a cancels list.
   */
  static int ldlm_cli_cancel_req(struct obd_export *exp,
  			       struct list_head *cancels,
  			       int count, enum ldlm_cancel_flags flags)
  {
  	struct ptlrpc_request *req = NULL;
  	struct obd_import *imp;
  	int free, sent = 0;
  	int rc = 0;
  
  	LASSERT(exp);
  	LASSERT(count > 0);
  
  	CFS_FAIL_TIMEOUT(OBD_FAIL_LDLM_PAUSE_CANCEL, cfs_fail_val);
  
  	if (CFS_FAIL_CHECK(OBD_FAIL_LDLM_CANCEL_RACE))
  		return count;
  
  	free = ldlm_format_handles_avail(class_exp2cliimp(exp),
  					 &RQF_LDLM_CANCEL, RCL_CLIENT, 0);
  	if (count > free)
  		count = free;
  
  	while (1) {
  		imp = class_exp2cliimp(exp);
  		if (!imp || imp->imp_invalid) {
  			CDEBUG(D_DLMTRACE,
  			       "skipping cancel on invalid import %p\n", imp);
  			return count;
  		}
  
  		req = ptlrpc_request_alloc(imp, &RQF_LDLM_CANCEL);
  		if (!req) {
  			rc = -ENOMEM;
  			goto out;
  		}
  
  		req_capsule_filled_sizes(&req->rq_pill, RCL_CLIENT);
  		req_capsule_set_size(&req->rq_pill, &RMF_DLM_REQ, RCL_CLIENT,
  				     ldlm_request_bufsize(count, LDLM_CANCEL));
  
  		rc = ptlrpc_request_pack(req, LUSTRE_DLM_VERSION, LDLM_CANCEL);
  		if (rc) {
  			ptlrpc_request_free(req);
  			goto out;
  		}
  
  		req->rq_request_portal = LDLM_CANCEL_REQUEST_PORTAL;
  		req->rq_reply_portal = LDLM_CANCEL_REPLY_PORTAL;
  		ptlrpc_at_set_req_timeout(req);
  
  		ldlm_cancel_pack(req, cancels, count);
  
  		ptlrpc_request_set_replen(req);
  		if (flags & LCF_ASYNC) {
  			ptlrpcd_add_req(req);
  			sent = count;
  			goto out;
  		}
  
  		rc = ptlrpc_queue_wait(req);
  		if (rc == LUSTRE_ESTALE) {
  			CDEBUG(D_DLMTRACE, "client/server (nid %s) out of sync -- not fatal\n",
  			       libcfs_nid2str(req->rq_import->
  					      imp_connection->c_peer.nid));
  			rc = 0;
  		} else if (rc == -ETIMEDOUT && /* check there was no reconnect*/
  			   req->rq_import_generation == imp->imp_generation) {
  			ptlrpc_req_finished(req);
  			continue;
  		} else if (rc != ELDLM_OK) {
  			/* -ESHUTDOWN is common on umount */
  			CDEBUG_LIMIT(rc == -ESHUTDOWN ? D_DLMTRACE : D_ERROR,
  				     "Got rc %d from cancel RPC: canceling anyway\n",
  				     rc);
  			break;
  		}
  		sent = count;
  		break;
  	}
  
  	ptlrpc_req_finished(req);
  out:
  	return sent ? sent : rc;
  }
  
  static inline struct ldlm_pool *ldlm_imp2pl(struct obd_import *imp)
  {
  	return &imp->imp_obd->obd_namespace->ns_pool;
  }
  
  /**
   * Update client's OBD pool related fields with new SLV and Limit from \a req.
   */
  int ldlm_cli_update_pool(struct ptlrpc_request *req)
  {
  	struct obd_device *obd;
  	__u64 new_slv;
  	__u32 new_limit;
  
  	if (unlikely(!req->rq_import || !req->rq_import->imp_obd ||
  		     !imp_connect_lru_resize(req->rq_import))) {
  		/*
  		 * Do nothing for corner cases.
  		 */
  		return 0;
  	}
  
  	/* In some cases RPC may contain SLV and limit zeroed out. This
  	 * is the case when server does not support LRU resize feature.
  	 * This is also possible in some recovery cases when server-side
  	 * reqs have no reference to the OBD export and thus access to
  	 * server-side namespace is not possible.
  	 */
  	if (lustre_msg_get_slv(req->rq_repmsg) == 0 ||
  	    lustre_msg_get_limit(req->rq_repmsg) == 0) {
  		DEBUG_REQ(D_HA, req,
  			  "Zero SLV or Limit found (SLV: %llu, Limit: %u)",
  			  lustre_msg_get_slv(req->rq_repmsg),
  			  lustre_msg_get_limit(req->rq_repmsg));
  		return 0;
  	}
  
  	new_limit = lustre_msg_get_limit(req->rq_repmsg);
  	new_slv = lustre_msg_get_slv(req->rq_repmsg);
  	obd = req->rq_import->imp_obd;
  
  	/* Set new SLV and limit in OBD fields to make them accessible
  	 * to the pool thread. We do not access obd_namespace and pool
  	 * directly here as there is no reliable way to make sure that
  	 * they are still alive at cleanup time. Evil races are possible
  	 * which may cause Oops at that time.
  	 */
  	write_lock(&obd->obd_pool_lock);
  	obd->obd_pool_slv = new_slv;
  	obd->obd_pool_limit = new_limit;
  	write_unlock(&obd->obd_pool_lock);
  
  	return 0;
  }
  EXPORT_SYMBOL(ldlm_cli_update_pool);
  
  /**
   * Client side lock cancel.
   *
   * Lock must not have any readers or writers by this time.
   */
  int ldlm_cli_cancel(const struct lustre_handle *lockh,
  		    enum ldlm_cancel_flags cancel_flags)
  {
  	struct obd_export *exp;
  	int avail, flags, count = 1;
  	__u64 rc = 0;
  	struct ldlm_namespace *ns;
  	struct ldlm_lock *lock;
  	LIST_HEAD(cancels);
  
  	/* concurrent cancels on the same handle can happen */
  	lock = ldlm_handle2lock_long(lockh, LDLM_FL_CANCELING);
  	if (!lock) {
  		LDLM_DEBUG_NOLOCK("lock is already being destroyed");
  		return 0;
  	}
  
  	rc = ldlm_cli_cancel_local(lock);
  	if (rc == LDLM_FL_LOCAL_ONLY || cancel_flags & LCF_LOCAL) {
  		LDLM_LOCK_RELEASE(lock);
  		return 0;
  	}
  	/* Even if the lock is marked as LDLM_FL_BL_AST, this is a LDLM_CANCEL
  	 * RPC which goes to canceld portal, so we can cancel other LRU locks
  	 * here and send them all as one LDLM_CANCEL RPC.
  	 */
  	LASSERT(list_empty(&lock->l_bl_ast));
  	list_add(&lock->l_bl_ast, &cancels);
  
  	exp = lock->l_conn_export;
  	if (exp_connect_cancelset(exp)) {
  		avail = ldlm_format_handles_avail(class_exp2cliimp(exp),
  						  &RQF_LDLM_CANCEL,
  						  RCL_CLIENT, 0);
  		LASSERT(avail > 0);
  
  		ns = ldlm_lock_to_ns(lock);
  		flags = ns_connect_lru_resize(ns) ?
  			LDLM_CANCEL_LRUR : LDLM_CANCEL_AGED;
  		count += ldlm_cancel_lru_local(ns, &cancels, 0, avail - 1,
  					       LCF_BL_AST, flags);
  	}
  	ldlm_cli_cancel_list(&cancels, count, NULL, cancel_flags);
  	return 0;
  }
  EXPORT_SYMBOL(ldlm_cli_cancel);
  
  /**
   * Locally cancel up to \a count locks in list \a cancels.
   * Return the number of cancelled locks.
   */
  int ldlm_cli_cancel_list_local(struct list_head *cancels, int count,
  			       enum ldlm_cancel_flags flags)
  {
  	LIST_HEAD(head);
  	struct ldlm_lock *lock, *next;
  	int left = 0, bl_ast = 0;
  	__u64 rc;
  
  	left = count;
  	list_for_each_entry_safe(lock, next, cancels, l_bl_ast) {
  		if (left-- == 0)
  			break;
  
  		if (flags & LCF_LOCAL) {
  			rc = LDLM_FL_LOCAL_ONLY;
  			ldlm_lock_cancel(lock);
  		} else {
  			rc = ldlm_cli_cancel_local(lock);
  		}
  		/* Until we have compound requests and can send LDLM_CANCEL
  		 * requests batched with generic RPCs, we need to send cancels
  		 * with the LDLM_FL_BL_AST flag in a separate RPC from
  		 * the one being generated now.
  		 */
  		if (!(flags & LCF_BL_AST) && (rc == LDLM_FL_BL_AST)) {
  			LDLM_DEBUG(lock, "Cancel lock separately");
  			list_del_init(&lock->l_bl_ast);
  			list_add(&lock->l_bl_ast, &head);
  			bl_ast++;
  			continue;
  		}
  		if (rc == LDLM_FL_LOCAL_ONLY) {
  			/* CANCEL RPC should not be sent to server. */
  			list_del_init(&lock->l_bl_ast);
  			LDLM_LOCK_RELEASE(lock);
  			count--;
  		}
  	}
  	if (bl_ast > 0) {
  		count -= bl_ast;
  		ldlm_cli_cancel_list(&head, bl_ast, NULL, 0);
  	}
  
  	return count;
  }
  EXPORT_SYMBOL(ldlm_cli_cancel_list_local);
  
  /**
   * Cancel as many locks as possible w/o sending any RPCs (e.g. to write back
   * dirty data, to close a file, ...) or waiting for any RPCs in-flight (e.g.
   * readahead requests, ...)
   */
  static enum ldlm_policy_res
  ldlm_cancel_no_wait_policy(struct ldlm_namespace *ns, struct ldlm_lock *lock,
  			   int unused, int added, int count)
  {
  	enum ldlm_policy_res result = LDLM_POLICY_CANCEL_LOCK;
  
  	/* don't check added & count since we want to process all locks
  	 * from unused list.
  	 * It's fine to not take lock to access lock->l_resource since
  	 * the lock has already been granted so it won't change.
  	 */
  	switch (lock->l_resource->lr_type) {
  	case LDLM_EXTENT:
  	case LDLM_IBITS:
  		if (ns->ns_cancel && ns->ns_cancel(lock) != 0)
  			break;
  	default:
  		result = LDLM_POLICY_SKIP_LOCK;
  		lock_res_and_lock(lock);
  		ldlm_set_skipped(lock);
  		unlock_res_and_lock(lock);
  		break;
  	}
  
  	return result;
  }
  
  /**
   * Callback function for LRU-resize policy. Decides whether to keep
   * \a lock in LRU for current \a LRU size \a unused, added in current
   * scan \a added and number of locks to be preferably canceled \a count.
   *
   * \retval LDLM_POLICY_KEEP_LOCK keep lock in LRU in stop scanning
   *
   * \retval LDLM_POLICY_CANCEL_LOCK cancel lock from LRU
   */
  static enum ldlm_policy_res ldlm_cancel_lrur_policy(struct ldlm_namespace *ns,
  						    struct ldlm_lock *lock,
  						    int unused, int added,
  						    int count)
  {
  	unsigned long cur = cfs_time_current();
  	struct ldlm_pool *pl = &ns->ns_pool;
  	__u64 slv, lvf, lv;
  	unsigned long la;
  
  	/* Stop LRU processing when we reach past @count or have checked all
  	 * locks in LRU.
  	 */
  	if (count && added >= count)
  		return LDLM_POLICY_KEEP_LOCK;
  
  	slv = ldlm_pool_get_slv(pl);
  	lvf = ldlm_pool_get_lvf(pl);
  	la = cfs_duration_sec(cfs_time_sub(cur, lock->l_last_used));
  	lv = lvf * la * unused;
  
  	/* Inform pool about current CLV to see it via debugfs. */
  	ldlm_pool_set_clv(pl, lv);
  
  	/* Stop when SLV is not yet come from server or lv is smaller than
  	 * it is.
  	 */
  	if (slv == 0 || lv < slv)
  		return LDLM_POLICY_KEEP_LOCK;
  
  	return LDLM_POLICY_CANCEL_LOCK;
  }
  
  /**
   * Callback function for debugfs used policy. Makes decision whether to keep
   * \a lock in LRU for current \a LRU size \a unused, added in current scan \a
   * added and number of locks to be preferably canceled \a count.
   *
   * \retval LDLM_POLICY_KEEP_LOCK keep lock in LRU in stop scanning
   *
   * \retval LDLM_POLICY_CANCEL_LOCK cancel lock from LRU
   */
  static enum ldlm_policy_res ldlm_cancel_passed_policy(struct ldlm_namespace *ns,
  						      struct ldlm_lock *lock,
  						      int unused, int added,
  						      int count)
  {
  	/* Stop LRU processing when we reach past @count or have checked all
  	 * locks in LRU.
  	 */
  	return (added >= count) ?
  		LDLM_POLICY_KEEP_LOCK : LDLM_POLICY_CANCEL_LOCK;
  }
  
  /**
   * Callback function for aged policy. Makes decision whether to keep \a lock in
   * LRU for current LRU size \a unused, added in current scan \a added and
   * number of locks to be preferably canceled \a count.
   *
   * \retval LDLM_POLICY_KEEP_LOCK keep lock in LRU in stop scanning
   *
   * \retval LDLM_POLICY_CANCEL_LOCK cancel lock from LRU
   */
  static enum ldlm_policy_res ldlm_cancel_aged_policy(struct ldlm_namespace *ns,
  						    struct ldlm_lock *lock,
  						    int unused, int added,
  						    int count)
  {
  	if ((added >= count) &&
  	    time_before(cfs_time_current(),
  			cfs_time_add(lock->l_last_used, ns->ns_max_age)))
  		return LDLM_POLICY_KEEP_LOCK;
  
  	return LDLM_POLICY_CANCEL_LOCK;
  }
  
  static enum ldlm_policy_res
  ldlm_cancel_lrur_no_wait_policy(struct ldlm_namespace *ns,
  				struct ldlm_lock *lock,
  				int unused, int added,
  				int count)
  {
  	enum ldlm_policy_res result;
  
  	result = ldlm_cancel_lrur_policy(ns, lock, unused, added, count);
  	if (result == LDLM_POLICY_KEEP_LOCK)
  		return result;
  
  	return ldlm_cancel_no_wait_policy(ns, lock, unused, added, count);
  }
  
  /**
   * Callback function for default policy. Makes decision whether to keep \a lock
   * in LRU for current LRU size \a unused, added in current scan \a added and
   * number of locks to be preferably canceled \a count.
   *
   * \retval LDLM_POLICY_KEEP_LOCK keep lock in LRU in stop scanning
   *
   * \retval LDLM_POLICY_CANCEL_LOCK cancel lock from LRU
   */
  static enum ldlm_policy_res
  ldlm_cancel_default_policy(struct ldlm_namespace *ns, struct ldlm_lock *lock,
  			   int unused, int added, int count)
  {
  	/* Stop LRU processing when we reach past count or have checked all
  	 * locks in LRU.
  	 */
  	return (added >= count) ?
  		LDLM_POLICY_KEEP_LOCK : LDLM_POLICY_CANCEL_LOCK;
  }
  
  typedef enum ldlm_policy_res (*ldlm_cancel_lru_policy_t)(
  						      struct ldlm_namespace *,
  						      struct ldlm_lock *, int,
  						      int, int);
  
  static ldlm_cancel_lru_policy_t
  ldlm_cancel_lru_policy(struct ldlm_namespace *ns, int flags)
  {
  	if (flags & LDLM_CANCEL_NO_WAIT)
  		return ldlm_cancel_no_wait_policy;
  
  	if (ns_connect_lru_resize(ns)) {
  		if (flags & LDLM_CANCEL_SHRINK)
  			/* We kill passed number of old locks. */
  			return ldlm_cancel_passed_policy;
  		else if (flags & LDLM_CANCEL_LRUR)
  			return ldlm_cancel_lrur_policy;
  		else if (flags & LDLM_CANCEL_PASSED)
  			return ldlm_cancel_passed_policy;
  		else if (flags & LDLM_CANCEL_LRUR_NO_WAIT)
  			return ldlm_cancel_lrur_no_wait_policy;
  	} else {
  		if (flags & LDLM_CANCEL_AGED)
  			return ldlm_cancel_aged_policy;
  	}
  
  	return ldlm_cancel_default_policy;
  }
  
  /**
   * - Free space in LRU for \a count new locks,
   *   redundant unused locks are canceled locally;
   * - also cancel locally unused aged locks;
   * - do not cancel more than \a max locks;
   * - GET the found locks and add them into the \a cancels list.
   *
   * A client lock can be added to the l_bl_ast list only when it is
   * marked LDLM_FL_CANCELING. Otherwise, somebody is already doing
   * CANCEL.  There are the following use cases:
   * ldlm_cancel_resource_local(), ldlm_cancel_lru_local() and
   * ldlm_cli_cancel(), which check and set this flag properly. As any
   * attempt to cancel a lock rely on this flag, l_bl_ast list is accessed
   * later without any special locking.
   *
   * Calling policies for enabled LRU resize:
   * ----------------------------------------
   * flags & LDLM_CANCEL_LRUR - use LRU resize policy (SLV from server) to
   *			    cancel not more than \a count locks;
   *
   * flags & LDLM_CANCEL_PASSED - cancel \a count number of old locks (located at
   *			      the beginning of LRU list);
   *
   * flags & LDLM_CANCEL_SHRINK - cancel not more than \a count locks according to
   *			      memory pressure policy function;
   *
   * flags & LDLM_CANCEL_AGED - cancel \a count locks according to "aged policy".
   *
   * flags & LDLM_CANCEL_NO_WAIT - cancel as many unused locks as possible
   *			       (typically before replaying locks) w/o
   *			       sending any RPCs or waiting for any
   *			       outstanding RPC to complete.
   */
  static int ldlm_prepare_lru_list(struct ldlm_namespace *ns,
  				 struct list_head *cancels, int count, int max,
  				 int flags)
  {
  	ldlm_cancel_lru_policy_t pf;
  	struct ldlm_lock *lock, *next;
  	int added = 0, unused, remained;
  	int no_wait = flags & (LDLM_CANCEL_NO_WAIT | LDLM_CANCEL_LRUR_NO_WAIT);
  
  	spin_lock(&ns->ns_lock);
  	unused = ns->ns_nr_unused;
  	remained = unused;
  
  	if (!ns_connect_lru_resize(ns))
  		count += unused - ns->ns_max_unused;
  
  	pf = ldlm_cancel_lru_policy(ns, flags);
  	LASSERT(pf);
  
  	while (!list_empty(&ns->ns_unused_list)) {
  		enum ldlm_policy_res result;
  		time_t last_use = 0;
  
  		/* all unused locks */
  		if (remained-- <= 0)
  			break;
  
  		/* For any flags, stop scanning if @max is reached. */
  		if (max && added >= max)
  			break;
  
  		list_for_each_entry_safe(lock, next, &ns->ns_unused_list,
  					 l_lru) {
  			/* No locks which got blocking requests. */
  			LASSERT(!ldlm_is_bl_ast(lock));
  
  			if (no_wait && ldlm_is_skipped(lock))
  				/* already processed */
  				continue;
  
  			last_use = lock->l_last_used;
  			if (last_use == cfs_time_current())
  				continue;
  
  			/* Somebody is already doing CANCEL. No need for this
  			 * lock in LRU, do not traverse it again.
  			 */
  			if (!ldlm_is_canceling(lock))
  				break;
  
  			ldlm_lock_remove_from_lru_nolock(lock);
  		}
  		if (&lock->l_lru == &ns->ns_unused_list)
  			break;
  
  		LDLM_LOCK_GET(lock);
  		spin_unlock(&ns->ns_lock);
  		lu_ref_add(&lock->l_reference, __func__, current);
  
  		/* Pass the lock through the policy filter and see if it
  		 * should stay in LRU.
  		 *
  		 * Even for shrinker policy we stop scanning if
  		 * we find a lock that should stay in the cache.
  		 * We should take into account lock age anyway
  		 * as a new lock is a valuable resource even if
  		 * it has a low weight.
  		 *
  		 * That is, for shrinker policy we drop only
  		 * old locks, but additionally choose them by
  		 * their weight. Big extent locks will stay in
  		 * the cache.
  		 */
  		result = pf(ns, lock, unused, added, count);
  		if (result == LDLM_POLICY_KEEP_LOCK) {
  			lu_ref_del(&lock->l_reference,
  				   __func__, current);
  			LDLM_LOCK_RELEASE(lock);
  			spin_lock(&ns->ns_lock);
  			break;
  		}
  		if (result == LDLM_POLICY_SKIP_LOCK) {
  			lu_ref_del(&lock->l_reference,
  				   __func__, current);
  			LDLM_LOCK_RELEASE(lock);
  			spin_lock(&ns->ns_lock);
  			continue;
  		}
  
  		lock_res_and_lock(lock);
  		/* Check flags again under the lock. */
  		if (ldlm_is_canceling(lock) ||
  		    (ldlm_lock_remove_from_lru_check(lock, last_use) == 0)) {
  			/* Another thread is removing lock from LRU, or
  			 * somebody is already doing CANCEL, or there
  			 * is a blocking request which will send cancel
  			 * by itself, or the lock is no longer unused or
  			 * the lock has been used since the pf() call and
  			 * pages could be put under it.
  			 */
  			unlock_res_and_lock(lock);
  			lu_ref_del(&lock->l_reference,
  				   __func__, current);
  			LDLM_LOCK_RELEASE(lock);
  			spin_lock(&ns->ns_lock);
  			continue;
  		}
  		LASSERT(!lock->l_readers && !lock->l_writers);
  
  		/* If we have chosen to cancel this lock voluntarily, we
  		 * better send cancel notification to server, so that it
  		 * frees appropriate state. This might lead to a race
  		 * where while we are doing cancel here, server is also
  		 * silently cancelling this lock.
  		 */
  		ldlm_clear_cancel_on_block(lock);
  
  		/* Setting the CBPENDING flag is a little misleading,
  		 * but prevents an important race; namely, once
  		 * CBPENDING is set, the lock can accumulate no more
  		 * readers/writers. Since readers and writers are
  		 * already zero here, ldlm_lock_decref() won't see
  		 * this flag and call l_blocking_ast
  		 */
  		lock->l_flags |= LDLM_FL_CBPENDING | LDLM_FL_CANCELING;
  
  		/* We can't re-add to l_lru as it confuses the
  		 * refcounting in ldlm_lock_remove_from_lru() if an AST
  		 * arrives after we drop lr_lock below. We use l_bl_ast
  		 * and can't use l_pending_chain as it is used both on
  		 * server and client nevertheless bug 5666 says it is
  		 * used only on server
  		 */
  		LASSERT(list_empty(&lock->l_bl_ast));
  		list_add(&lock->l_bl_ast, cancels);
  		unlock_res_and_lock(lock);
  		lu_ref_del(&lock->l_reference, __func__, current);
  		spin_lock(&ns->ns_lock);
  		added++;
  		unused--;
  	}
  	spin_unlock(&ns->ns_lock);
  	return added;
  }
  
  int ldlm_cancel_lru_local(struct ldlm_namespace *ns,
  			  struct list_head *cancels, int count, int max,
  			  enum ldlm_cancel_flags cancel_flags, int flags)
  {
  	int added;
  
  	added = ldlm_prepare_lru_list(ns, cancels, count, max, flags);
  	if (added <= 0)
  		return added;
  	return ldlm_cli_cancel_list_local(cancels, added, cancel_flags);
  }
  
  /**
   * Cancel at least \a nr locks from given namespace LRU.
   *
   * When called with LCF_ASYNC the blocking callback will be handled
   * in a thread and this function will return after the thread has been
   * asked to call the callback.  When called with LCF_ASYNC the blocking
   * callback will be performed in this function.
   */
  int ldlm_cancel_lru(struct ldlm_namespace *ns, int nr,
  		    enum ldlm_cancel_flags cancel_flags,
  		    int flags)
  {
  	LIST_HEAD(cancels);
  	int count, rc;
  
  	/* Just prepare the list of locks, do not actually cancel them yet.
  	 * Locks are cancelled later in a separate thread.
  	 */
  	count = ldlm_prepare_lru_list(ns, &cancels, nr, 0, flags);
  	rc = ldlm_bl_to_thread_list(ns, NULL, &cancels, count, cancel_flags);
  	if (rc == 0)
  		return count;
  
  	return 0;
  }
  
  /**
   * Find and cancel locally unused locks found on resource, matched to the
   * given policy, mode. GET the found locks and add them into the \a cancels
   * list.
   */
  int ldlm_cancel_resource_local(struct ldlm_resource *res,
  			       struct list_head *cancels,
  			       ldlm_policy_data_t *policy,
  			       enum ldlm_mode mode, __u64 lock_flags,
  			       enum ldlm_cancel_flags cancel_flags,
  			       void *opaque)
  {
  	struct ldlm_lock *lock;
  	int count = 0;
  
  	lock_res(res);
  	list_for_each_entry(lock, &res->lr_granted, l_res_link) {
  		if (opaque && lock->l_ast_data != opaque) {
  			LDLM_ERROR(lock, "data %p doesn't match opaque %p",
  				   lock->l_ast_data, opaque);
  			continue;
  		}
  
  		if (lock->l_readers || lock->l_writers)
  			continue;
  
  		/* If somebody is already doing CANCEL, or blocking AST came,
  		 * skip this lock.
  		 */
  		if (ldlm_is_bl_ast(lock) || ldlm_is_canceling(lock))
  			continue;
  
  		if (lockmode_compat(lock->l_granted_mode, mode))
  			continue;
  
  		/* If policy is given and this is IBITS lock, add to list only
  		 * those locks that match by policy.
  		 */
  		if (policy && (lock->l_resource->lr_type == LDLM_IBITS) &&
  		    !(lock->l_policy_data.l_inodebits.bits &
  		      policy->l_inodebits.bits))
  			continue;
  
  		/* See CBPENDING comment in ldlm_cancel_lru */
  		lock->l_flags |= LDLM_FL_CBPENDING | LDLM_FL_CANCELING |
  				 lock_flags;
  
  		LASSERT(list_empty(&lock->l_bl_ast));
  		list_add(&lock->l_bl_ast, cancels);
  		LDLM_LOCK_GET(lock);
  		count++;
  	}
  	unlock_res(res);
  
  	return ldlm_cli_cancel_list_local(cancels, count, cancel_flags);
  }
  EXPORT_SYMBOL(ldlm_cancel_resource_local);
  
  /**
   * Cancel client-side locks from a list and send/prepare cancel RPCs to the
   * server.
   * If \a req is NULL, send CANCEL request to server with handles of locks
   * in the \a cancels. If EARLY_CANCEL is not supported, send CANCEL requests
   * separately per lock.
   * If \a req is not NULL, put handles of locks in \a cancels into the request
   * buffer at the offset \a off.
   * Destroy \a cancels at the end.
   */
  int ldlm_cli_cancel_list(struct list_head *cancels, int count,
  			 struct ptlrpc_request *req,
  			 enum ldlm_cancel_flags flags)
  {
  	struct ldlm_lock *lock;
  	int res = 0;
  
  	if (list_empty(cancels) || count == 0)
  		return 0;
  
  	/* XXX: requests (both batched and not) could be sent in parallel.
  	 * Usually it is enough to have just 1 RPC, but it is possible that
  	 * there are too many locks to be cancelled in LRU or on a resource.
  	 * It would also speed up the case when the server does not support
  	 * the feature.
  	 */
  	while (count > 0) {
  		LASSERT(!list_empty(cancels));
  		lock = list_entry(cancels->next, struct ldlm_lock, l_bl_ast);
  		LASSERT(lock->l_conn_export);
  
  		if (exp_connect_cancelset(lock->l_conn_export)) {
  			res = count;
  			if (req)
  				ldlm_cancel_pack(req, cancels, count);
  			else
  				res = ldlm_cli_cancel_req(lock->l_conn_export,
  							  cancels, count,
  							  flags);
  		} else {
  			res = ldlm_cli_cancel_req(lock->l_conn_export,
  						  cancels, 1, flags);
  		}
  
  		if (res < 0) {
  			CDEBUG_LIMIT(res == -ESHUTDOWN ? D_DLMTRACE : D_ERROR,
  				     "ldlm_cli_cancel_list: %d\n", res);
  			res = count;
  		}
  
  		count -= res;
  		ldlm_lock_list_put(cancels, l_bl_ast, res);
  	}
  	LASSERT(count == 0);
  	return 0;
  }
  EXPORT_SYMBOL(ldlm_cli_cancel_list);
  
  /**
   * Cancel all locks on a resource that have 0 readers/writers.
   *
   * If flags & LDLM_FL_LOCAL_ONLY, throw the locks away without trying
   * to notify the server.
   */
  int ldlm_cli_cancel_unused_resource(struct ldlm_namespace *ns,
  				    const struct ldlm_res_id *res_id,
  				    ldlm_policy_data_t *policy,
  				    enum ldlm_mode mode,
  				    enum ldlm_cancel_flags flags,
  				    void *opaque)
  {
  	struct ldlm_resource *res;
  	LIST_HEAD(cancels);
  	int count;
  	int rc;
  
  	res = ldlm_resource_get(ns, NULL, res_id, 0, 0);
  	if (IS_ERR(res)) {
  		/* This is not a problem. */
  		CDEBUG(D_INFO, "No resource %llu\n", res_id->name[0]);
  		return 0;
  	}
  
  	LDLM_RESOURCE_ADDREF(res);
  	count = ldlm_cancel_resource_local(res, &cancels, policy, mode,
  					   0, flags | LCF_BL_AST, opaque);
  	rc = ldlm_cli_cancel_list(&cancels, count, NULL, flags);
  	if (rc != ELDLM_OK)
  		CERROR("canceling unused lock "DLDLMRES": rc = %d\n",
  		       PLDLMRES(res), rc);
  
  	LDLM_RESOURCE_DELREF(res);
  	ldlm_resource_putref(res);
  	return 0;
  }
  EXPORT_SYMBOL(ldlm_cli_cancel_unused_resource);
  
  struct ldlm_cli_cancel_arg {
  	int     lc_flags;
  	void   *lc_opaque;
  };
  
  static int ldlm_cli_hash_cancel_unused(struct cfs_hash *hs,
  				       struct cfs_hash_bd *bd,
  				       struct hlist_node *hnode, void *arg)
  {
  	struct ldlm_resource	   *res = cfs_hash_object(hs, hnode);
  	struct ldlm_cli_cancel_arg     *lc = arg;
  
  	ldlm_cli_cancel_unused_resource(ldlm_res_to_ns(res), &res->lr_name,
  					NULL, LCK_MINMODE,
  					lc->lc_flags, lc->lc_opaque);
  	/* must return 0 for hash iteration */
  	return 0;
  }
  
  /**
   * Cancel all locks on a namespace (or a specific resource, if given)
   * that have 0 readers/writers.
   *
   * If flags & LCF_LOCAL, throw the locks away without trying
   * to notify the server.
   */
  int ldlm_cli_cancel_unused(struct ldlm_namespace *ns,
  			   const struct ldlm_res_id *res_id,
  			   enum ldlm_cancel_flags flags, void *opaque)
  {
  	struct ldlm_cli_cancel_arg arg = {
  		.lc_flags       = flags,
  		.lc_opaque      = opaque,
  	};
  
  	if (!ns)
  		return ELDLM_OK;
  
  	if (res_id) {
  		return ldlm_cli_cancel_unused_resource(ns, res_id, NULL,
  						       LCK_MINMODE, flags,
  						       opaque);
  	} else {
  		cfs_hash_for_each_nolock(ns->ns_rs_hash,
  					 ldlm_cli_hash_cancel_unused, &arg);
  		return ELDLM_OK;
  	}
  }
  EXPORT_SYMBOL(ldlm_cli_cancel_unused);
  
  /* Lock iterators. */
  
  static int ldlm_resource_foreach(struct ldlm_resource *res,
  				 ldlm_iterator_t iter, void *closure)
  {
  	struct list_head *tmp, *next;
  	struct ldlm_lock *lock;
  	int rc = LDLM_ITER_CONTINUE;
  
  	if (!res)
  		return LDLM_ITER_CONTINUE;
  
  	lock_res(res);
  	list_for_each_safe(tmp, next, &res->lr_granted) {
  		lock = list_entry(tmp, struct ldlm_lock, l_res_link);
  
  		if (iter(lock, closure) == LDLM_ITER_STOP) {
  			rc = LDLM_ITER_STOP;
  			goto out;
  		}
  	}
  
  	list_for_each_safe(tmp, next, &res->lr_waiting) {
  		lock = list_entry(tmp, struct ldlm_lock, l_res_link);
  
  		if (iter(lock, closure) == LDLM_ITER_STOP) {
  			rc = LDLM_ITER_STOP;
  			goto out;
  		}
  	}
   out:
  	unlock_res(res);
  	return rc;
  }
  
  struct iter_helper_data {
  	ldlm_iterator_t iter;
  	void *closure;
  };
  
  static int ldlm_iter_helper(struct ldlm_lock *lock, void *closure)
  {
  	struct iter_helper_data *helper = closure;
  
  	return helper->iter(lock, helper->closure);
  }
  
  static int ldlm_res_iter_helper(struct cfs_hash *hs, struct cfs_hash_bd *bd,
  				struct hlist_node *hnode, void *arg)
  
  {
  	struct ldlm_resource *res = cfs_hash_object(hs, hnode);
  
  	return ldlm_resource_foreach(res, ldlm_iter_helper, arg) ==
  	       LDLM_ITER_STOP;
  }
  
  static void ldlm_namespace_foreach(struct ldlm_namespace *ns,
  				   ldlm_iterator_t iter, void *closure)
  
  {
  	struct iter_helper_data helper = {
  		.iter		= iter,
  		.closure	= closure,
  	};
  
  	cfs_hash_for_each_nolock(ns->ns_rs_hash,
  				 ldlm_res_iter_helper, &helper);
  }
  
  /* non-blocking function to manipulate a lock whose cb_data is being put away.
   * return  0:  find no resource
   *       > 0:  must be LDLM_ITER_STOP/LDLM_ITER_CONTINUE.
   *       < 0:  errors
   */
  int ldlm_resource_iterate(struct ldlm_namespace *ns,
  			  const struct ldlm_res_id *res_id,
  			  ldlm_iterator_t iter, void *data)
  {
  	struct ldlm_resource *res;
  	int rc;
  
  	LASSERTF(ns, "must pass in namespace\n");
  
  	res = ldlm_resource_get(ns, NULL, res_id, 0, 0);
  	if (IS_ERR(res))
  		return 0;
  
  	LDLM_RESOURCE_ADDREF(res);
  	rc = ldlm_resource_foreach(res, iter, data);
  	LDLM_RESOURCE_DELREF(res);
  	ldlm_resource_putref(res);
  	return rc;
  }
  EXPORT_SYMBOL(ldlm_resource_iterate);
  
  /* Lock replay */
  
  static int ldlm_chain_lock_for_replay(struct ldlm_lock *lock, void *closure)
  {
  	struct list_head *list = closure;
  
  	/* we use l_pending_chain here, because it's unused on clients. */
  	LASSERTF(list_empty(&lock->l_pending_chain),
  		 "lock %p next %p prev %p\n",
  		 lock, &lock->l_pending_chain.next,
  		 &lock->l_pending_chain.prev);
  	/* bug 9573: don't replay locks left after eviction, or
  	 * bug 17614: locks being actively cancelled. Get a reference
  	 * on a lock so that it does not disappear under us (e.g. due to cancel)
  	 */
  	if (!(lock->l_flags & (LDLM_FL_FAILED | LDLM_FL_CANCELING))) {
  		list_add(&lock->l_pending_chain, list);
  		LDLM_LOCK_GET(lock);
  	}
  
  	return LDLM_ITER_CONTINUE;
  }
  
  static int replay_lock_interpret(const struct lu_env *env,
  				 struct ptlrpc_request *req,
  				 struct ldlm_async_args *aa, int rc)
  {
  	struct ldlm_lock     *lock;
  	struct ldlm_reply    *reply;
  	struct obd_export    *exp;
  
  	atomic_dec(&req->rq_import->imp_replay_inflight);
  	if (rc != ELDLM_OK)
  		goto out;
  
  	reply = req_capsule_server_get(&req->rq_pill, &RMF_DLM_REP);
  	if (!reply) {
  		rc = -EPROTO;
  		goto out;
  	}
  
  	lock = ldlm_handle2lock(&aa->lock_handle);
  	if (!lock) {
  		CERROR("received replay ack for unknown local cookie %#llx remote cookie %#llx from server %s id %s\n",
  		       aa->lock_handle.cookie, reply->lock_handle.cookie,
  		       req->rq_export->exp_client_uuid.uuid,
  		       libcfs_id2str(req->rq_peer));
  		rc = -ESTALE;
  		goto out;
  	}
  
  	/* Key change rehash lock in per-export hash with new key */
  	exp = req->rq_export;
  	if (exp && exp->exp_lock_hash) {
  		/* In the function below, .hs_keycmp resolves to
  		 * ldlm_export_lock_keycmp()
  		 */
  		/* coverity[overrun-buffer-val] */
  		cfs_hash_rehash_key(exp->exp_lock_hash,
  				    &lock->l_remote_handle,
  				    &reply->lock_handle,
  				    &lock->l_exp_hash);
  	} else {
  		lock->l_remote_handle = reply->lock_handle;
  	}
  
  	LDLM_DEBUG(lock, "replayed lock:");
  	ptlrpc_import_recovery_state_machine(req->rq_import);
  	LDLM_LOCK_PUT(lock);
  out:
  	if (rc != ELDLM_OK)
  		ptlrpc_connect_import(req->rq_import);
  
  	return rc;
  }
  
  static int replay_one_lock(struct obd_import *imp, struct ldlm_lock *lock)
  {
  	struct ptlrpc_request *req;
  	struct ldlm_async_args *aa;
  	struct ldlm_request   *body;
  	int flags;
  
  	/* Bug 11974: Do not replay a lock which is actively being canceled */
  	if (ldlm_is_canceling(lock)) {
  		LDLM_DEBUG(lock, "Not replaying canceled lock:");
  		return 0;
  	}
  
  	/* If this is reply-less callback lock, we cannot replay it, since
  	 * server might have long dropped it, but notification of that event was
  	 * lost by network. (and server granted conflicting lock already)
  	 */
  	if (ldlm_is_cancel_on_block(lock)) {
  		LDLM_DEBUG(lock, "Not replaying reply-less lock:");
  		ldlm_lock_cancel(lock);
  		return 0;
  	}
  
  	/*
  	 * If granted mode matches the requested mode, this lock is granted.
  	 *
  	 * If they differ, but we have a granted mode, then we were granted
  	 * one mode and now want another: ergo, converting.
  	 *
  	 * If we haven't been granted anything and are on a resource list,
  	 * then we're blocked/waiting.
  	 *
  	 * If we haven't been granted anything and we're NOT on a resource list,
  	 * then we haven't got a reply yet and don't have a known disposition.
  	 * This happens whenever a lock enqueue is the request that triggers
  	 * recovery.
  	 */
  	if (lock->l_granted_mode == lock->l_req_mode)
  		flags = LDLM_FL_REPLAY | LDLM_FL_BLOCK_GRANTED;
  	else if (lock->l_granted_mode)
  		flags = LDLM_FL_REPLAY | LDLM_FL_BLOCK_CONV;
  	else if (!list_empty(&lock->l_res_link))
  		flags = LDLM_FL_REPLAY | LDLM_FL_BLOCK_WAIT;
  	else
  		flags = LDLM_FL_REPLAY;
  
  	req = ptlrpc_request_alloc_pack(imp, &RQF_LDLM_ENQUEUE,
  					LUSTRE_DLM_VERSION, LDLM_ENQUEUE);
  	if (!req)
  		return -ENOMEM;
  
  	/* We're part of recovery, so don't wait for it. */
  	req->rq_send_state = LUSTRE_IMP_REPLAY_LOCKS;
  
  	body = req_capsule_client_get(&req->rq_pill, &RMF_DLM_REQ);
  	ldlm_lock2desc(lock, &body->lock_desc);
  	body->lock_flags = ldlm_flags_to_wire(flags);
  
  	ldlm_lock2handle(lock, &body->lock_handle[0]);
  	if (lock->l_lvb_len > 0)
  		req_capsule_extend(&req->rq_pill, &RQF_LDLM_ENQUEUE_LVB);
  	req_capsule_set_size(&req->rq_pill, &RMF_DLM_LVB, RCL_SERVER,
  			     lock->l_lvb_len);
  	ptlrpc_request_set_replen(req);
  	/* notify the server we've replayed all requests.
  	 * also, we mark the request to be put on a dedicated
  	 * queue to be processed after all request replayes.
  	 * bug 6063
  	 */
  	lustre_msg_set_flags(req->rq_reqmsg, MSG_REQ_REPLAY_DONE);
  
  	LDLM_DEBUG(lock, "replaying lock:");
  
  	atomic_inc(&req->rq_import->imp_replay_inflight);
  	CLASSERT(sizeof(*aa) <= sizeof(req->rq_async_args));
  	aa = ptlrpc_req_async_args(req);
  	aa->lock_handle = body->lock_handle[0];
  	req->rq_interpret_reply = (ptlrpc_interpterer_t)replay_lock_interpret;
  	ptlrpcd_add_req(req);
  
  	return 0;
  }
  
  /**
   * Cancel as many unused locks as possible before replay. since we are
   * in recovery, we can't wait for any outstanding RPCs to send any RPC
   * to the server.
   *
   * Called only in recovery before replaying locks. there is no need to
   * replay locks that are unused. since the clients may hold thousands of
   * cached unused locks, dropping the unused locks can greatly reduce the
   * load on the servers at recovery time.
   */
  static void ldlm_cancel_unused_locks_for_replay(struct ldlm_namespace *ns)
  {
  	int canceled;
  	LIST_HEAD(cancels);
  
  	CDEBUG(D_DLMTRACE, "Dropping as many unused locks as possible before replay for namespace %s (%d)\n",
  	       ldlm_ns_name(ns), ns->ns_nr_unused);
  
  	/* We don't need to care whether or not LRU resize is enabled
  	 * because the LDLM_CANCEL_NO_WAIT policy doesn't use the
  	 * count parameter
  	 */
  	canceled = ldlm_cancel_lru_local(ns, &cancels, ns->ns_nr_unused, 0,
  					 LCF_LOCAL, LDLM_CANCEL_NO_WAIT);
  
  	CDEBUG(D_DLMTRACE, "Canceled %d unused locks from namespace %s\n",
  	       canceled, ldlm_ns_name(ns));
  }
  
  int ldlm_replay_locks(struct obd_import *imp)
  {
  	struct ldlm_namespace *ns = imp->imp_obd->obd_namespace;
  	LIST_HEAD(list);
  	struct ldlm_lock *lock, *next;
  	int rc = 0;
  
  	LASSERT(atomic_read(&imp->imp_replay_inflight) == 0);
  
  	/* don't replay locks if import failed recovery */
  	if (imp->imp_vbr_failed)
  		return 0;
  
  	/* ensure this doesn't fall to 0 before all have been queued */
  	atomic_inc(&imp->imp_replay_inflight);
  
  	if (ldlm_cancel_unused_locks_before_replay)
  		ldlm_cancel_unused_locks_for_replay(ns);
  
  	ldlm_namespace_foreach(ns, ldlm_chain_lock_for_replay, &list);
  
  	list_for_each_entry_safe(lock, next, &list, l_pending_chain) {
  		list_del_init(&lock->l_pending_chain);
  		if (rc) {
  			LDLM_LOCK_RELEASE(lock);
  			continue; /* or try to do the rest? */
  		}
  		rc = replay_one_lock(imp, lock);
  		LDLM_LOCK_RELEASE(lock);
  	}
  
  	atomic_dec(&imp->imp_replay_inflight);
  
  	return rc;
  }
  EXPORT_SYMBOL(ldlm_replay_locks);
  