Whamcloud - gitweb
LU-3157 llite: A not locked mutex can be unlocked.
[fs/lustre-release.git] / lustre / obdclass / cl_lock.c
index b8096b7..fc8f9c9 100644 (file)
@@ -1,6 +1,4 @@
-/* -*- mode: c; c-basic-offset: 8; indent-tabs-mode: nil; -*-
- * vim:expandtab:shiftwidth=8:tabstop=8:
- *
+/*
  * GPL HEADER START
  *
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
@@ -29,8 +27,7 @@
  * Copyright (c) 2008, 2010, Oracle and/or its affiliates. All rights reserved.
  * Use is subject to license terms.
  *
- * Copyright (c) 2011 Whamcloud, Inc.
- *
+ * Copyright (c) 2011, 2013, Intel Corporation.
  */
 /*
  * This file is part of Lustre, http://www.lustre.org/
  */
 
 #define DEBUG_SUBSYSTEM S_CLASS
-#ifndef EXPORT_SYMTAB
-# define EXPORT_SYMTAB
-#endif
 
 #include <obd_class.h>
 #include <obd_support.h>
 #include <lustre_fid.h>
 #include <libcfs/list.h>
-/* lu_time_global_{init,fini}() */
-#include <lu_time.h>
-
 #include <cl_object.h>
 #include "cl_internal.h"
 
 /** Lock class of cl_lock::cll_guard */
-static cfs_lock_class_key_t cl_lock_guard_class;
+static struct lock_class_key cl_lock_guard_class;
 static cfs_mem_cache_t *cl_lock_kmem;
 
 static struct lu_kmem_descr cl_lock_caches[] = {
@@ -71,6 +62,22 @@ static struct lu_kmem_descr cl_lock_caches[] = {
         }
 };
 
+#ifdef CONFIG_DEBUG_PAGESTATE_TRACKING
+#define CS_LOCK_INC(o, item) \
+       cfs_atomic_inc(&cl_object_site(o)->cs_locks.cs_stats[CS_##item])
+#define CS_LOCK_DEC(o, item) \
+       cfs_atomic_dec(&cl_object_site(o)->cs_locks.cs_stats[CS_##item])
+#define CS_LOCKSTATE_INC(o, state) \
+        cfs_atomic_inc(&cl_object_site(o)->cs_locks_state[state])
+#define CS_LOCKSTATE_DEC(o, state) \
+        cfs_atomic_dec(&cl_object_site(o)->cs_locks_state[state])
+#else
+#define CS_LOCK_INC(o, item)
+#define CS_LOCK_DEC(o, item)
+#define CS_LOCKSTATE_INC(o, state)
+#define CS_LOCKSTATE_DEC(o, state)
+#endif
+
 /**
  * Basic lock invariant that is maintained at all times. Caller either has a
  * reference to \a lock, or somehow assures that \a lock cannot be freed.
@@ -148,7 +155,7 @@ static void cl_lock_trace0(int level, const struct lu_env *env,
 #define RETIP ((unsigned long)__builtin_return_address(0))
 
 #ifdef CONFIG_LOCKDEP
-static cfs_lock_class_key_t cl_lock_key;
+static struct lock_class_key cl_lock_key;
 
 static void cl_lock_lockdep_init(struct cl_lock *lock)
 {
@@ -275,13 +282,13 @@ static void cl_lock_free(const struct lu_env *env, struct cl_lock *lock)
                 cfs_list_del_init(lock->cll_layers.next);
                 slice->cls_ops->clo_fini(env, slice);
         }
-        cfs_atomic_dec(&cl_object_site(obj)->cs_locks.cs_total);
-        cfs_atomic_dec(&cl_object_site(obj)->cs_locks_state[lock->cll_state]);
+       CS_LOCK_DEC(obj, total);
+       CS_LOCKSTATE_DEC(obj, lock->cll_state);
         lu_object_ref_del_at(&obj->co_lu, lock->cll_obj_ref, "cl_lock", lock);
         cl_object_put(env, obj);
         lu_ref_fini(&lock->cll_reference);
         lu_ref_fini(&lock->cll_holders);
-        cfs_mutex_destroy(&lock->cll_guard);
+       mutex_destroy(&lock->cll_guard);
         OBD_SLAB_FREE_PTR(lock, cl_lock_kmem);
         EXIT;
 }
@@ -298,13 +305,11 @@ static void cl_lock_free(const struct lu_env *env, struct cl_lock *lock)
 void cl_lock_put(const struct lu_env *env, struct cl_lock *lock)
 {
         struct cl_object        *obj;
-        struct cl_site          *site;
 
         LINVRNT(cl_lock_invariant(env, lock));
         ENTRY;
         obj = lock->cll_descr.cld_obj;
         LINVRNT(obj != NULL);
-        site = cl_object_site(obj);
 
         CDEBUG(D_TRACE, "releasing reference: %d %p %lu\n",
                cfs_atomic_read(&lock->cll_ref), lock, RETIP);
@@ -314,7 +319,7 @@ void cl_lock_put(const struct lu_env *env, struct cl_lock *lock)
                         LASSERT(cfs_list_empty(&lock->cll_linkage));
                         cl_lock_free(env, lock);
                 }
-                cfs_atomic_dec(&site->cs_locks.cs_busy);
+               CS_LOCK_DEC(obj, busy);
         }
         EXIT;
 }
@@ -348,12 +353,10 @@ EXPORT_SYMBOL(cl_lock_get);
  */
 void cl_lock_get_trust(struct cl_lock *lock)
 {
-        struct cl_site *site = cl_object_site(lock->cll_descr.cld_obj);
-
         CDEBUG(D_TRACE, "acquiring trusted reference: %d %p %lu\n",
                cfs_atomic_read(&lock->cll_ref), lock, RETIP);
         if (cfs_atomic_inc_return(&lock->cll_ref) == 1)
-                cfs_atomic_inc(&site->cs_locks.cs_busy);
+               CS_LOCK_INC(lock->cll_descr.cld_obj, busy);
 }
 EXPORT_SYMBOL(cl_lock_get_trust);
 
@@ -379,7 +382,6 @@ static struct cl_lock *cl_lock_alloc(const struct lu_env *env,
 {
         struct cl_lock          *lock;
         struct lu_object_header *head;
-        struct cl_site          *site = cl_object_site(obj);
 
         ENTRY;
         OBD_SLAB_ALLOC_PTR_GFP(lock, cl_lock_kmem, CFS_ALLOC_IO);
@@ -395,13 +397,13 @@ static struct cl_lock *cl_lock_alloc(const struct lu_env *env,
                 CFS_INIT_LIST_HEAD(&lock->cll_inclosure);
                 lu_ref_init(&lock->cll_reference);
                 lu_ref_init(&lock->cll_holders);
-                cfs_mutex_init(&lock->cll_guard);
-                cfs_lockdep_set_class(&lock->cll_guard, &cl_lock_guard_class);
+               mutex_init(&lock->cll_guard);
+               lockdep_set_class(&lock->cll_guard, &cl_lock_guard_class);
                 cfs_waitq_init(&lock->cll_wq);
                 head = obj->co_lu.lo_header;
-                cfs_atomic_inc(&site->cs_locks_state[CLS_NEW]);
-                cfs_atomic_inc(&site->cs_locks.cs_total);
-                cfs_atomic_inc(&site->cs_locks.cs_created);
+               CS_LOCKSTATE_INC(obj, CLS_NEW);
+               CS_LOCK_INC(obj, total);
+               CS_LOCK_INC(obj, create);
                 cl_lock_lockdep_init(lock);
                 cfs_list_for_each_entry(obj, &head->loh_layers,
                                         co_lu.lo_linkage) {
@@ -499,14 +501,12 @@ static struct cl_lock *cl_lock_lookup(const struct lu_env *env,
 {
         struct cl_lock          *lock;
         struct cl_object_header *head;
-        struct cl_site          *site;
 
         ENTRY;
 
         head = cl_object_header(obj);
-        site = cl_object_site(obj);
         LINVRNT_SPIN_LOCKED(&head->coh_lock_guard);
-        cfs_atomic_inc(&site->cs_locks.cs_lookup);
+       CS_LOCK_INC(obj, lookup);
         cfs_list_for_each_entry(lock, &head->coh_locks, cll_linkage) {
                 int matched;
 
@@ -520,7 +520,7 @@ static struct cl_lock *cl_lock_lookup(const struct lu_env *env,
                        matched);
                 if (matched) {
                         cl_lock_get_trust(lock);
-                        cfs_atomic_inc(&cl_object_site(obj)->cs_locks.cs_hit);
+                       CS_LOCK_INC(obj, hit);
                         RETURN(lock);
                 }
         }
@@ -544,32 +544,30 @@ static struct cl_lock *cl_lock_find(const struct lu_env *env,
         struct cl_object_header *head;
         struct cl_object        *obj;
         struct cl_lock          *lock;
-        struct cl_site          *site;
 
         ENTRY;
 
         obj  = need->cld_obj;
         head = cl_object_header(obj);
-        site = cl_object_site(obj);
-
-        cfs_spin_lock(&head->coh_lock_guard);
-        lock = cl_lock_lookup(env, obj, io, need);
-        cfs_spin_unlock(&head->coh_lock_guard);
-
-        if (lock == NULL) {
-                lock = cl_lock_alloc(env, obj, io, need);
-                if (!IS_ERR(lock)) {
-                        struct cl_lock *ghost;
-
-                        cfs_spin_lock(&head->coh_lock_guard);
-                        ghost = cl_lock_lookup(env, obj, io, need);
-                        if (ghost == NULL) {
-                                cfs_list_add_tail(&lock->cll_linkage,
-                                                  &head->coh_locks);
-                                cfs_spin_unlock(&head->coh_lock_guard);
-                                cfs_atomic_inc(&site->cs_locks.cs_busy);
-                        } else {
-                                cfs_spin_unlock(&head->coh_lock_guard);
+
+       spin_lock(&head->coh_lock_guard);
+       lock = cl_lock_lookup(env, obj, io, need);
+       spin_unlock(&head->coh_lock_guard);
+
+       if (lock == NULL) {
+               lock = cl_lock_alloc(env, obj, io, need);
+               if (!IS_ERR(lock)) {
+                       struct cl_lock *ghost;
+
+                       spin_lock(&head->coh_lock_guard);
+                       ghost = cl_lock_lookup(env, obj, io, need);
+                       if (ghost == NULL) {
+                               cfs_list_add_tail(&lock->cll_linkage,
+                                                 &head->coh_locks);
+                               spin_unlock(&head->coh_lock_guard);
+                               CS_LOCK_INC(obj, busy);
+                       } else {
+                               spin_unlock(&head->coh_lock_guard);
                                 /*
                                  * Other threads can acquire references to the
                                  * top-lock through its sub-locks. Hence, it
@@ -595,35 +593,40 @@ struct cl_lock *cl_lock_peek(const struct lu_env *env, const struct cl_io *io,
         struct cl_object_header *head;
         struct cl_object        *obj;
         struct cl_lock          *lock;
-        int ok;
 
         obj  = need->cld_obj;
         head = cl_object_header(obj);
 
-        cfs_spin_lock(&head->coh_lock_guard);
-        lock = cl_lock_lookup(env, obj, io, need);
-        cfs_spin_unlock(&head->coh_lock_guard);
-
-        if (lock == NULL)
-                return NULL;
-
-        cl_lock_mutex_get(env, lock);
-        if (lock->cll_state == CLS_INTRANSIT)
-                cl_lock_state_wait(env, lock); /* Don't care return value. */
-        if (lock->cll_state == CLS_CACHED) {
-                int result;
-                result = cl_use_try(env, lock, 1);
-                if (result < 0)
-                        cl_lock_error(env, lock, result);
-        }
-        ok = lock->cll_state == CLS_HELD;
-        if (ok) {
-                cl_lock_hold_add(env, lock, scope, source);
-                cl_lock_user_add(env, lock);
-                cl_lock_put(env, lock);
-        }
-        cl_lock_mutex_put(env, lock);
-        if (!ok) {
+       do {
+               spin_lock(&head->coh_lock_guard);
+               lock = cl_lock_lookup(env, obj, io, need);
+               spin_unlock(&head->coh_lock_guard);
+               if (lock == NULL)
+                       return NULL;
+
+               cl_lock_mutex_get(env, lock);
+               if (lock->cll_state == CLS_INTRANSIT)
+                       /* Don't care return value. */
+                       cl_lock_state_wait(env, lock);
+               if (lock->cll_state == CLS_FREEING) {
+                       cl_lock_mutex_put(env, lock);
+                       cl_lock_put(env, lock);
+                       lock = NULL;
+               }
+       } while (lock == NULL);
+
+       cl_lock_hold_add(env, lock, scope, source);
+       cl_lock_user_add(env, lock);
+       if (lock->cll_state == CLS_CACHED)
+               cl_use_try(env, lock, 1);
+       if (lock->cll_state == CLS_HELD) {
+               cl_lock_mutex_put(env, lock);
+               cl_lock_lockdep_acquire(env, lock, 0);
+               cl_lock_put(env, lock);
+       } else {
+               cl_unuse_try(env, lock);
+               cl_lock_unhold(env, lock, scope, source);
+                cl_lock_mutex_put(env, lock);
                 cl_lock_put(env, lock);
                 lock = NULL;
         }
@@ -695,7 +698,7 @@ void cl_lock_mutex_get(const struct lu_env *env, struct cl_lock *lock)
                 info = cl_env_info(env);
                 for (i = 0; i < hdr->coh_nesting; ++i)
                         LASSERT(info->clt_counters[i].ctc_nr_locks_locked == 0);
-                cfs_mutex_lock_nested(&lock->cll_guard, hdr->coh_nesting);
+               mutex_lock_nested(&lock->cll_guard, hdr->coh_nesting);
                 lock->cll_guarder = cfs_current();
                 LINVRNT(lock->cll_depth == 0);
         }
@@ -725,7 +728,7 @@ int cl_lock_mutex_try(const struct lu_env *env, struct cl_lock *lock)
         if (lock->cll_guarder == cfs_current()) {
                 LINVRNT(lock->cll_depth > 0);
                 cl_lock_mutex_tail(env, lock);
-        } else if (cfs_mutex_trylock(&lock->cll_guard)) {
+       } else if (mutex_trylock(&lock->cll_guard)) {
                 LINVRNT(lock->cll_depth == 0);
                 lock->cll_guarder = cfs_current();
                 cl_lock_mutex_tail(env, lock);
@@ -759,7 +762,7 @@ void cl_lock_mutex_put(const struct lu_env *env, struct cl_lock *lock)
         counters->ctc_nr_locks_locked--;
         if (--lock->cll_depth == 0) {
                 lock->cll_guarder = NULL;
-                cfs_mutex_unlock(&lock->cll_guard);
+               mutex_unlock(&lock->cll_guard);
         }
 }
 EXPORT_SYMBOL(cl_lock_mutex_put);
@@ -827,10 +830,10 @@ static void cl_lock_delete0(const struct lu_env *env, struct cl_lock *lock)
 
                 head = cl_object_header(lock->cll_descr.cld_obj);
 
-                cfs_spin_lock(&head->coh_lock_guard);
-                cfs_list_del_init(&lock->cll_linkage);
+               spin_lock(&head->coh_lock_guard);
+               cfs_list_del_init(&lock->cll_linkage);
+               spin_unlock(&head->coh_lock_guard);
 
-                cfs_spin_unlock(&head->coh_lock_guard);
                 /*
                  * From now on, no new references to this lock can be acquired
                  * by cl_lock_lookup().
@@ -893,8 +896,8 @@ static void cl_lock_used_mod(const struct lu_env *env, struct cl_lock *lock,
         }
 }
 
-static void cl_lock_hold_release(const struct lu_env *env, struct cl_lock *lock,
-                                 const char *scope, const void *source)
+void cl_lock_hold_release(const struct lu_env *env, struct cl_lock *lock,
+                         const char *scope, const void *source)
 {
         LINVRNT(cl_lock_is_mutexed(lock));
         LINVRNT(cl_lock_invariant(env, lock));
@@ -905,8 +908,10 @@ static void cl_lock_hold_release(const struct lu_env *env, struct cl_lock *lock,
         lu_ref_del(&lock->cll_holders, scope, source);
         cl_lock_hold_mod(env, lock, -1);
         if (lock->cll_holds == 0) {
-                if (lock->cll_descr.cld_mode == CLM_PHANTOM ||
-                    lock->cll_descr.cld_mode == CLM_GROUP)
+               CL_LOCK_ASSERT(lock->cll_state != CLS_HELD, env, lock);
+               if (lock->cll_descr.cld_mode == CLM_PHANTOM ||
+                   lock->cll_descr.cld_mode == CLM_GROUP ||
+                   lock->cll_state != CLS_CACHED)
                         /*
                          * If lock is still phantom or grouplock when user is
                          * done with it---destroy the lock.
@@ -924,7 +929,7 @@ static void cl_lock_hold_release(const struct lu_env *env, struct cl_lock *lock,
         }
         EXIT;
 }
-
+EXPORT_SYMBOL(cl_lock_hold_release);
 
 /**
  * Waits until lock state is changed.
@@ -971,12 +976,19 @@ int cl_lock_state_wait(const struct lu_env *env, struct cl_lock *lock)
                 cl_lock_mutex_put(env, lock);
 
                 LASSERT(cl_lock_nr_mutexed(env) == 0);
-                cfs_waitq_wait(&waiter, CFS_TASK_INTERRUPTIBLE);
+
+               /* Returning ERESTARTSYS instead of EINTR so syscalls
+                * can be restarted if signals are pending here */
+               result = -ERESTARTSYS;
+               if (likely(!OBD_FAIL_CHECK(OBD_FAIL_LOCK_STATE_WAIT_INTR))) {
+                       cfs_waitq_wait(&waiter, CFS_TASK_INTERRUPTIBLE);
+                       if (!cfs_signal_pending())
+                               result = 0;
+               }
 
                 cl_lock_mutex_get(env, lock);
                 cfs_set_current_state(CFS_TASK_RUNNING);
                 cfs_waitq_del(&lock->cll_wq, &waiter);
-                result = cfs_signal_pending() ? -EINTR : 0;
 
                 /* Restore old blocked signals */
                 cfs_restore_sigs(blocked);
@@ -1030,8 +1042,6 @@ EXPORT_SYMBOL(cl_lock_signal);
 void cl_lock_state_set(const struct lu_env *env, struct cl_lock *lock,
                        enum cl_lock_state state)
 {
-        struct cl_site *site = cl_object_site(lock->cll_descr.cld_obj);
-
         ENTRY;
         LASSERT(lock->cll_state <= state ||
                 (lock->cll_state == CLS_CACHED &&
@@ -1042,8 +1052,8 @@ void cl_lock_state_set(const struct lu_env *env, struct cl_lock *lock,
                 lock->cll_state == CLS_INTRANSIT);
 
         if (lock->cll_state != state) {
-                cfs_atomic_dec(&site->cs_locks_state[lock->cll_state]);
-                cfs_atomic_inc(&site->cs_locks_state[state]);
+               CS_LOCKSTATE_DEC(lock->cll_descr.cld_obj, lock->cll_state);
+               CS_LOCKSTATE_INC(lock->cll_descr.cld_obj, state);
 
                 cl_lock_state_signal(env, lock, state);
                 lock->cll_state = state;
@@ -1186,12 +1196,12 @@ int cl_enqueue_try(const struct lu_env *env, struct cl_lock *lock,
         ENTRY;
         cl_lock_trace(D_DLMTRACE, env, "enqueue lock", lock);
         do {
-                result = 0;
-
                 LINVRNT(cl_lock_is_mutexed(lock));
 
-                if (lock->cll_error != 0)
+               result = lock->cll_error;
+               if (result != 0)
                         break;
+
                 switch (lock->cll_state) {
                 case CLS_NEW:
                         cl_lock_state_set(env, lock, CLS_QUEUING);
@@ -1199,7 +1209,9 @@ int cl_enqueue_try(const struct lu_env *env, struct cl_lock *lock,
                 case CLS_QUEUING:
                         /* kick layers. */
                         result = cl_enqueue_kick(env, lock, io, flags);
-                        if (result == 0)
+                       /* For AGL case, the cl_lock::cll_state may
+                        * become CLS_HELD already. */
+                       if (result == 0 && lock->cll_state == CLS_QUEUING)
                                 cl_lock_state_set(env, lock, CLS_ENQUEUED);
                         break;
                 case CLS_INTRANSIT:
@@ -1224,9 +1236,7 @@ int cl_enqueue_try(const struct lu_env *env, struct cl_lock *lock,
                         LBUG();
                 }
         } while (result == CLO_REPEAT);
-        if (result < 0)
-                cl_lock_error(env, lock, result);
-        RETURN(result ?: lock->cll_error);
+       RETURN(result);
 }
 EXPORT_SYMBOL(cl_enqueue_try);
 
@@ -1255,6 +1265,7 @@ int cl_lock_enqueue_wait(const struct lu_env *env,
         LASSERT(cl_lock_nr_mutexed(env) == 0);
 
         cl_lock_mutex_get(env, conflict);
+       cl_lock_trace(D_DLMTRACE, env, "enqueue wait", conflict);
         cl_lock_cancel(env, conflict);
         cl_lock_delete(env, conflict);
 
@@ -1299,11 +1310,10 @@ static int cl_enqueue_locked(const struct lu_env *env, struct cl_lock *lock,
                 }
                 break;
         } while (1);
-        if (result != 0) {
-                cl_lock_user_del(env, lock);
-                cl_lock_error(env, lock, result);
-        }
-        LASSERT(ergo(result == 0, lock->cll_state == CLS_ENQUEUED ||
+       if (result != 0)
+               cl_unuse_try(env, lock);
+        LASSERT(ergo(result == 0 && !(enqflags & CEF_AGL),
+                     lock->cll_state == CLS_ENQUEUED ||
                      lock->cll_state == CLS_HELD));
         RETURN(result);
 }
@@ -1339,13 +1349,11 @@ EXPORT_SYMBOL(cl_enqueue);
 /**
  * Tries to unlock a lock.
  *
- * This function is called repeatedly by cl_unuse() until either lock is
- * unlocked, or error occurs.
- * cl_unuse_try is a one-shot operation, so it must NOT return CLO_WAIT.
- *
- * \pre  lock->cll_state == CLS_HELD
+ * This function is called to release underlying resource:
+ * 1. for top lock, the resource is sublocks it held;
+ * 2. for sublock, the resource is the reference to dlmlock.
  *
- * \post ergo(result == 0, lock->cll_state == CLS_CACHED)
+ * cl_unuse_try is a one-shot operation, so it must NOT return CLO_WAIT.
  *
  * \see cl_unuse() cl_lock_operations::clo_unuse()
  * \see cl_lock_state::CLS_CACHED
@@ -1358,12 +1366,18 @@ int cl_unuse_try(const struct lu_env *env, struct cl_lock *lock)
         ENTRY;
         cl_lock_trace(D_DLMTRACE, env, "unuse lock", lock);
 
-        LASSERT(lock->cll_state == CLS_HELD || lock->cll_state == CLS_ENQUEUED);
         if (lock->cll_users > 1) {
                 cl_lock_user_del(env, lock);
                 RETURN(0);
         }
 
+       /* Only if the lock is in CLS_HELD or CLS_ENQUEUED state, it can hold
+        * underlying resources. */
+       if (!(lock->cll_state == CLS_HELD || lock->cll_state == CLS_ENQUEUED)) {
+               cl_lock_user_del(env, lock);
+               RETURN(0);
+       }
+
         /*
          * New lock users (->cll_users) are not protecting unlocking
          * from proceeding. From this point, lock eventually reaches
@@ -1404,13 +1418,10 @@ int cl_unuse_try(const struct lu_env *env, struct cl_lock *lock)
                 result = 0;
         } else {
                 CERROR("result = %d, this is unlikely!\n", result);
+               state = CLS_NEW;
                 cl_lock_extransit(env, lock, state);
         }
-
-        result = result ?: lock->cll_error;
-        if (result < 0)
-                cl_lock_error(env, lock, result);
-        RETURN(result);
+       RETURN(result ?: lock->cll_error);
 }
 EXPORT_SYMBOL(cl_unuse_try);
 
@@ -1460,14 +1471,16 @@ int cl_wait_try(const struct lu_env *env, struct cl_lock *lock)
         do {
                 LINVRNT(cl_lock_is_mutexed(lock));
                 LINVRNT(cl_lock_invariant(env, lock));
-                LASSERT(lock->cll_state == CLS_ENQUEUED ||
-                        lock->cll_state == CLS_HELD ||
-                        lock->cll_state == CLS_INTRANSIT);
+               LASSERTF(lock->cll_state == CLS_QUEUING ||
+                        lock->cll_state == CLS_ENQUEUED ||
+                        lock->cll_state == CLS_HELD ||
+                        lock->cll_state == CLS_INTRANSIT,
+                        "lock state: %d\n", lock->cll_state);
                 LASSERT(lock->cll_users > 0);
                 LASSERT(lock->cll_holds > 0);
 
-                result = 0;
-                if (lock->cll_error != 0)
+               result = lock->cll_error;
+               if (result != 0)
                         break;
 
                 if (cl_lock_is_intransit(lock)) {
@@ -1493,7 +1506,7 @@ int cl_wait_try(const struct lu_env *env, struct cl_lock *lock)
                         cl_lock_state_set(env, lock, CLS_HELD);
                 }
         } while (result == CLO_REPEAT);
-        RETURN(result ?: lock->cll_error);
+       RETURN(result);
 }
 EXPORT_SYMBOL(cl_wait_try);
 
@@ -1528,8 +1541,7 @@ int cl_wait(const struct lu_env *env, struct cl_lock *lock)
                 break;
         } while (1);
         if (result < 0) {
-                cl_lock_user_del(env, lock);
-                cl_lock_error(env, lock, result);
+               cl_unuse_try(env, lock);
                 cl_lock_lockdep_release(env, lock);
         }
         cl_lock_trace(D_DLMTRACE, env, "wait lock", lock);
@@ -1605,10 +1617,10 @@ int cl_lock_modify(const struct lu_env *env, struct cl_lock *lock,
          * now. If locks were indexed according to their extent and/or mode,
          * that index would have to be updated here.
          */
-        cfs_spin_lock(&hdr->coh_lock_guard);
-        lock->cll_descr = *desc;
-        cfs_spin_unlock(&hdr->coh_lock_guard);
-        RETURN(0);
+       spin_lock(&hdr->coh_lock_guard);
+       lock->cll_descr = *desc;
+       spin_unlock(&hdr->coh_lock_guard);
+       RETURN(0);
 }
 EXPORT_SYMBOL(cl_lock_modify);
 
@@ -1797,8 +1809,8 @@ void cl_lock_error(const struct lu_env *env, struct cl_lock *lock, int error)
         LINVRNT(cl_lock_invariant(env, lock));
 
         ENTRY;
-        cl_lock_trace(D_DLMTRACE, env, "set lock error", lock);
         if (lock->cll_error == 0 && error != 0) {
+               cl_lock_trace(D_DLMTRACE, env, "set lock error", lock);
                 lock->cll_error = error;
                 cl_lock_signal(env, lock);
                 cl_lock_cancel(env, lock);
@@ -1835,12 +1847,13 @@ void cl_lock_cancel(const struct lu_env *env, struct cl_lock *lock)
 EXPORT_SYMBOL(cl_lock_cancel);
 
 /**
- * Finds an existing lock covering given page and optionally different from a
+ * Finds an existing lock covering given index and optionally different from a
  * given \a except lock.
  */
-struct cl_lock *cl_lock_at_page(const struct lu_env *env, struct cl_object *obj,
-                                struct cl_page *page, struct cl_lock *except,
-                                int pending, int canceld)
+struct cl_lock *cl_lock_at_pgoff(const struct lu_env *env,
+                                struct cl_object *obj, pgoff_t index,
+                                struct cl_lock *except,
+                                int pending, int canceld)
 {
         struct cl_object_header *head;
         struct cl_lock          *scan;
@@ -1855,10 +1868,10 @@ struct cl_lock *cl_lock_at_page(const struct lu_env *env, struct cl_object *obj,
 
         need->cld_mode = CLM_READ; /* CLM_READ matches both READ & WRITE, but
                                     * not PHANTOM */
-        need->cld_start = need->cld_end = page->cp_index;
+       need->cld_start = need->cld_end = index;
         need->cld_enq_flags = 0;
 
-        cfs_spin_lock(&head->coh_lock_guard);
+       spin_lock(&head->coh_lock_guard);
         /* It is fine to match any group lock since there could be only one
          * with a uniq gid and it conflicts with all other lock modes too */
         cfs_list_for_each_entry(scan, &head->coh_locks, cll_linkage) {
@@ -1881,104 +1894,104 @@ struct cl_lock *cl_lock_at_page(const struct lu_env *env, struct cl_object *obj,
                         break;
                 }
         }
-        cfs_spin_unlock(&head->coh_lock_guard);
-        RETURN(lock);
+       spin_unlock(&head->coh_lock_guard);
+       RETURN(lock);
 }
-EXPORT_SYMBOL(cl_lock_at_page);
+EXPORT_SYMBOL(cl_lock_at_pgoff);
 
 /**
- * Returns a list of pages protected (only) by a given lock.
- *
- * Scans an extent of page radix tree, corresponding to the \a lock and queues
- * all pages that are not protected by locks other than \a lock into \a queue.
+ * Calculate the page offset at the layer of @lock.
+ * At the time of this writing, @page is top page and @lock is sub lock.
  */
-void cl_lock_page_list_fixup(const struct lu_env *env,
-                             struct cl_io *io, struct cl_lock *lock,
-                             struct cl_page_list *queue)
+static pgoff_t pgoff_at_lock(struct cl_page *page, struct cl_lock *lock)
 {
-        struct cl_page        *page;
-        struct cl_page        *temp;
-        struct cl_page_list   *plist = &cl_env_info(env)->clt_list;
-
-        LINVRNT(cl_lock_invariant(env, lock));
-        ENTRY;
+        struct lu_device_type *dtype;
+        const struct cl_page_slice *slice;
 
-        /* No need to fix for WRITE lock because it is exclusive. */
-        if (lock->cll_descr.cld_mode >= CLM_WRITE)
-                RETURN_EXIT;
+        dtype = lock->cll_descr.cld_obj->co_lu.lo_dev->ld_type;
+        slice = cl_page_at(page, dtype);
+        LASSERT(slice != NULL);
+        return slice->cpl_page->cp_index;
+}
 
-        /* For those pages who are still covered by other PR locks, we should
-         * not discard them otherwise a [0, EOF) PR lock will discard all
-         * pages.
-         */
-        cl_page_list_init(plist);
-        cl_page_list_for_each_safe(page, temp, queue) {
-                pgoff_t                idx = page->cp_index;
-                struct cl_lock        *found;
-                struct cl_lock_descr  *descr;
-
-                /* The algorithm counts on the index-ascending page index. */
-                LASSERT(ergo(&temp->cp_batch != &queue->pl_pages,
-                        page->cp_index < temp->cp_index));
-
-                found = cl_lock_at_page(env, lock->cll_descr.cld_obj,
-                                        page, lock, 1, 0);
-                if (found == NULL)
-                        continue;
-
-                descr = &found->cll_descr;
-                cfs_list_for_each_entry_safe_from(page, temp, &queue->pl_pages,
-                                                  cp_batch) {
-                        idx = page->cp_index;
-                        if (descr->cld_start > idx || descr->cld_end < idx)
-                                break;
-                        cl_page_list_move(plist, queue, page);
+/**
+ * Check if page @page is covered by an extra lock or discard it.
+ */
+static int check_and_discard_cb(const struct lu_env *env, struct cl_io *io,
+                                struct cl_page *page, void *cbdata)
+{
+        struct cl_thread_info *info = cl_env_info(env);
+        struct cl_lock *lock = cbdata;
+        pgoff_t index = pgoff_at_lock(page, lock);
+
+        if (index >= info->clt_fn_index) {
+                struct cl_lock *tmp;
+
+               /* refresh non-overlapped index */
+               tmp = cl_lock_at_pgoff(env, lock->cll_descr.cld_obj, index,
+                                       lock, 1, 0);
+                if (tmp != NULL) {
+                        /* Cache the first-non-overlapped index so as to skip
+                         * all pages within [index, clt_fn_index). This
+                         * is safe because if tmp lock is canceled, it will
+                         * discard these pages. */
+                        info->clt_fn_index = tmp->cll_descr.cld_end + 1;
+                        if (tmp->cll_descr.cld_end == CL_PAGE_EOF)
+                                info->clt_fn_index = CL_PAGE_EOF;
+                        cl_lock_put(env, tmp);
+                } else if (cl_page_own(env, io, page) == 0) {
+                        /* discard the page */
+                        cl_page_unmap(env, io, page);
+                        cl_page_discard(env, io, page);
+                        cl_page_disown(env, io, page);
+                } else {
+                        LASSERT(page->cp_state == CPS_FREEING);
                 }
-                cl_lock_put(env, found);
         }
 
-        /* The pages in plist are covered by other locks, don't handle them
-         * this time.
-         */
-        if (io != NULL)
-                cl_page_list_disown(env, io, plist);
-        cl_page_list_fini(env, plist);
-        EXIT;
+        info->clt_next_index = index + 1;
+        return CLP_GANG_OKAY;
+}
+
+static int discard_cb(const struct lu_env *env, struct cl_io *io,
+                      struct cl_page *page, void *cbdata)
+{
+       struct cl_thread_info *info = cl_env_info(env);
+       struct cl_lock *lock   = cbdata;
+
+       LASSERT(lock->cll_descr.cld_mode >= CLM_WRITE);
+       KLASSERT(ergo(page->cp_type == CPT_CACHEABLE,
+                     !PageWriteback(cl_page_vmpage(env, page))));
+       KLASSERT(ergo(page->cp_type == CPT_CACHEABLE,
+                     !PageDirty(cl_page_vmpage(env, page))));
+
+       info->clt_next_index = pgoff_at_lock(page, lock) + 1;
+       if (cl_page_own(env, io, page) == 0) {
+               /* discard the page */
+               cl_page_unmap(env, io, page);
+               cl_page_discard(env, io, page);
+               cl_page_disown(env, io, page);
+       } else {
+               LASSERT(page->cp_state == CPS_FREEING);
+       }
+
+       return CLP_GANG_OKAY;
 }
-EXPORT_SYMBOL(cl_lock_page_list_fixup);
 
 /**
- * Invalidate pages protected by the given lock, sending them out to the
- * server first, if necessary.
- *
- * This function does the following:
- *
- *     - collects a list of pages to be invalidated,
- *
- *     - unmaps them from the user virtual memory,
- *
- *     - sends dirty pages to the server,
- *
- *     - waits for transfer completion,
- *
- *     - discards pages, and throws them out of memory.
- *
- * If \a discard is set, pages are discarded without sending them to the
- * server.
+ * Discard pages protected by the given lock. This function traverses radix
+ * tree to find all covering pages and discard them. If a page is being covered
+ * by other locks, it should remain in cache.
  *
  * If error happens on any step, the process continues anyway (the reasoning
  * behind this being that lock cancellation cannot be delayed indefinitely).
  */
-int cl_lock_page_out(const struct lu_env *env, struct cl_lock *lock,
-                     int discard)
+int cl_lock_discard_pages(const struct lu_env *env, struct cl_lock *lock)
 {
         struct cl_thread_info *info  = cl_env_info(env);
         struct cl_io          *io    = &info->clt_io;
-        struct cl_2queue      *queue = &info->clt_queue;
         struct cl_lock_descr  *descr = &lock->cll_descr;
-        struct lu_device_type *dtype;
-        long page_count;
-        pgoff_t next_index;
+        cl_page_gang_cb_t      cb;
         int res;
         int result;
 
@@ -1986,48 +1999,18 @@ int cl_lock_page_out(const struct lu_env *env, struct cl_lock *lock,
         ENTRY;
 
         io->ci_obj = cl_object_top(descr->cld_obj);
+       io->ci_ignore_layout = 1;
         result = cl_io_init(env, io, CIT_MISC, io->ci_obj);
         if (result != 0)
                 GOTO(out, result);
 
-        dtype = descr->cld_obj->co_lu.lo_dev->ld_type;
-        next_index = descr->cld_start;
+       cb = descr->cld_mode == CLM_READ ? check_and_discard_cb : discard_cb;
+        info->clt_fn_index = info->clt_next_index = descr->cld_start;
         do {
-                const struct cl_page_slice *slice;
-
-                cl_2queue_init(queue);
                 res = cl_page_gang_lookup(env, descr->cld_obj, io,
-                                          next_index, descr->cld_end,
-                                          &queue->c2_qin);
-                page_count = queue->c2_qin.pl_nr;
-                if (page_count == 0)
-                        break;
-
-                /* cl_page_gang_lookup() uses subobj and sublock to look for
-                 * covered pages, but @queue->c2_qin contains the list of top
-                 * pages. We have to turn the page back to subpage so as to
-                 * get `correct' next index. -jay */
-                slice = cl_page_at(cl_page_list_last(&queue->c2_qin), dtype);
-                next_index = slice->cpl_page->cp_index + 1;
-
-                result = cl_page_list_unmap(env, io, &queue->c2_qin);
-                if (!discard) {
-                        long timeout = 600; /* 10 minutes. */
-                        /* for debug purpose, if this request can't be
-                         * finished in 10 minutes, we hope it can notify us.
-                         */
-                        result = cl_io_submit_sync(env, io, CRT_WRITE, queue,
-                                                   CRP_CANCEL, timeout);
-                        if (result)
-                                CWARN("Writing %lu pages error: %d\n",
-                                      page_count, result);
-                }
-                cl_lock_page_list_fixup(env, io, lock, &queue->c2_qout);
-                cl_2queue_discard(env, io, queue);
-                cl_2queue_disown(env, io, queue);
-                cl_2queue_fini(env, queue);
-
-                if (next_index > descr->cld_end)
+                                          info->clt_next_index, descr->cld_end,
+                                          cb, (void *)lock);
+                if (info->clt_next_index > descr->cld_end)
                         break;
 
                 if (res == CLP_GANG_RESCHED)
@@ -2037,7 +2020,7 @@ out:
         cl_io_fini(env, io);
         RETURN(result);
 }
-EXPORT_SYMBOL(cl_lock_page_out);
+EXPORT_SYMBOL(cl_lock_discard_pages);
 
 /**
  * Eliminate all locks for a given object.
@@ -2061,17 +2044,28 @@ void cl_locks_prune(const struct lu_env *env, struct cl_object *obj, int cancel)
         LASSERT(ergo(!cancel,
                      head->coh_tree.rnode == NULL && head->coh_pages == 0));
 
-        cfs_spin_lock(&head->coh_lock_guard);
-        while (!cfs_list_empty(&head->coh_locks)) {
-                lock = container_of(head->coh_locks.next,
-                                    struct cl_lock, cll_linkage);
-                cl_lock_get_trust(lock);
-                cfs_spin_unlock(&head->coh_lock_guard);
+       spin_lock(&head->coh_lock_guard);
+       while (!cfs_list_empty(&head->coh_locks)) {
+               lock = container_of(head->coh_locks.next,
+                                   struct cl_lock, cll_linkage);
+               cl_lock_get_trust(lock);
+               spin_unlock(&head->coh_lock_guard);
                 lu_ref_add(&lock->cll_reference, "prune", cfs_current());
+
+again:
                 cl_lock_mutex_get(env, lock);
                 if (lock->cll_state < CLS_FREEING) {
-                        LASSERT(lock->cll_holds == 0);
-                        LASSERT(lock->cll_users == 0);
+                        LASSERT(lock->cll_users <= 1);
+                        if (unlikely(lock->cll_users == 1)) {
+                                struct l_wait_info lwi = { 0 };
+
+                                cl_lock_mutex_put(env, lock);
+                                l_wait_event(lock->cll_wq,
+                                             lock->cll_users == 0,
+                                             &lwi);
+                                goto again;
+                        }
+
                         if (cancel)
                                 cl_lock_cancel(env, lock);
                         cl_lock_delete(env, lock);
@@ -2079,10 +2073,10 @@ void cl_locks_prune(const struct lu_env *env, struct cl_object *obj, int cancel)
                 cl_lock_mutex_put(env, lock);
                 lu_ref_del(&lock->cll_reference, "prune", cfs_current());
                 cl_lock_put(env, lock);
-                cfs_spin_lock(&head->coh_lock_guard);
-        }
-        cfs_spin_unlock(&head->coh_lock_guard);
-        EXIT;
+               spin_lock(&head->coh_lock_guard);
+       }
+       spin_unlock(&head->coh_lock_guard);
+       EXIT;
 }
 EXPORT_SYMBOL(cl_locks_prune);
 
@@ -2150,25 +2144,34 @@ struct cl_lock *cl_lock_request(const struct lu_env *env, struct cl_io *io,
         ENTRY;
         do {
                 lock = cl_lock_hold_mutex(env, io, need, scope, source);
-                if (!IS_ERR(lock)) {
-                        rc = cl_enqueue_locked(env, lock, io, enqflags);
-                        if (rc == 0) {
-                                if (cl_lock_fits_into(env, lock, need, io)) {
+                if (IS_ERR(lock))
+                        break;
+
+                rc = cl_enqueue_locked(env, lock, io, enqflags);
+                if (rc == 0) {
+                        if (cl_lock_fits_into(env, lock, need, io)) {
+                                if (!(enqflags & CEF_AGL)) {
                                         cl_lock_mutex_put(env, lock);
-                                        cl_lock_lockdep_acquire(env,
-                                                                lock, enqflags);
+                                        cl_lock_lockdep_acquire(env, lock,
+                                                                enqflags);
                                         break;
                                 }
-                                cl_unuse_locked(env, lock);
+                                rc = 1;
                         }
-                        cl_lock_trace(D_DLMTRACE, env, "enqueue failed", lock);
-                        cl_lock_hold_release(env, lock, scope, source);
-                        cl_lock_mutex_put(env, lock);
-                        lu_ref_del(&lock->cll_reference, scope, source);
-                        cl_lock_put(env, lock);
+                        cl_unuse_locked(env, lock);
+                }
+                cl_lock_trace(D_DLMTRACE, env,
+                              rc <= 0 ? "enqueue failed" : "agl succeed", lock);
+                cl_lock_hold_release(env, lock, scope, source);
+                cl_lock_mutex_put(env, lock);
+                lu_ref_del(&lock->cll_reference, scope, source);
+                cl_lock_put(env, lock);
+                if (rc > 0) {
+                        LASSERT(enqflags & CEF_AGL);
+                        lock = NULL;
+                } else if (rc != 0) {
                         lock = ERR_PTR(rc);
-                } else
-                        rc = PTR_ERR(lock);
+                }
         } while (rc == 0);
         RETURN(lock);
 }
@@ -2238,7 +2241,7 @@ void cl_lock_user_add(const struct lu_env *env, struct cl_lock *lock)
 }
 EXPORT_SYMBOL(cl_lock_user_add);
 
-int cl_lock_user_del(const struct lu_env *env, struct cl_lock *lock)
+void cl_lock_user_del(const struct lu_env *env, struct cl_lock *lock)
 {
         LINVRNT(cl_lock_is_mutexed(lock));
         LINVRNT(cl_lock_invariant(env, lock));
@@ -2246,7 +2249,9 @@ int cl_lock_user_del(const struct lu_env *env, struct cl_lock *lock)
 
         ENTRY;
         cl_lock_used_mod(env, lock, -1);
-        RETURN(lock->cll_users == 0);
+        if (lock->cll_users == 0)
+                cfs_waitq_broadcast(&lock->cll_wq);
+        EXIT;
 }
 EXPORT_SYMBOL(cl_lock_user_del);