staging: lustre: ldlm: ldlm_lock: remove unneeded null test before free

[deliverable/linux.git] / drivers / staging / lustre / lustre / ldlm / ldlm_lock.c

/*
 * GPL HEADER START
 *
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 only,
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License version 2 for more details (a copy is included
 * in the LICENSE file that accompanied this code).
 *
 * You should have received a copy of the GNU General Public License
 * version 2 along with this program; If not, see
 * http://www.sun.com/software/products/lustre/docs/GPLv2.pdf
 *
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 *
 * GPL HEADER END
 */
/*
 * Copyright (c) 2002, 2010, Oracle and/or its affiliates. All rights reserved.
 * Use is subject to license terms.
 *
 * Copyright (c) 2010, 2012, Intel Corporation.
 */
/*
 * This file is part of Lustre, http://www.lustre.org/
 * Lustre is a trademark of Sun Microsystems, Inc.
 *
 * lustre/ldlm/ldlm_lock.c
 *
 * Author: Peter Braam <braam@clusterfs.com>
 * Author: Phil Schwan <phil@clusterfs.com>
 */

#define DEBUG_SUBSYSTEM S_LDLM

#include "../../include/linux/libcfs/libcfs.h"
#include "../include/lustre_intent.h"
#include "../include/obd_class.h"
#include "ldlm_internal.h"

/* lock types */
char *ldlm_lockname[] = {
        [0]             = "--",
        [LCK_EX]        = "EX",
        [LCK_PW]        = "PW",
        [LCK_PR]        = "PR",
        [LCK_CW]        = "CW",
        [LCK_CR]        = "CR",
        [LCK_NL]        = "NL",
        [LCK_GROUP]     = "GROUP",
        [LCK_COS]       = "COS",
};
EXPORT_SYMBOL(ldlm_lockname);

char *ldlm_typename[] = {
        [LDLM_PLAIN]    = "PLN",
        [LDLM_EXTENT]   = "EXT",
        [LDLM_FLOCK]    = "FLK",
        [LDLM_IBITS]    = "IBT",
};
EXPORT_SYMBOL(ldlm_typename);

static ldlm_policy_wire_to_local_t ldlm_policy_wire18_to_local[] = {
        [LDLM_PLAIN - LDLM_MIN_TYPE]    = ldlm_plain_policy_wire_to_local,
        [LDLM_EXTENT - LDLM_MIN_TYPE]   = ldlm_extent_policy_wire_to_local,
        [LDLM_FLOCK - LDLM_MIN_TYPE]    = ldlm_flock_policy_wire18_to_local,
        [LDLM_IBITS - LDLM_MIN_TYPE]    = ldlm_ibits_policy_wire_to_local,
};

static ldlm_policy_wire_to_local_t ldlm_policy_wire21_to_local[] = {
        [LDLM_PLAIN - LDLM_MIN_TYPE]    = ldlm_plain_policy_wire_to_local,
        [LDLM_EXTENT - LDLM_MIN_TYPE]   = ldlm_extent_policy_wire_to_local,
        [LDLM_FLOCK - LDLM_MIN_TYPE]    = ldlm_flock_policy_wire21_to_local,
        [LDLM_IBITS - LDLM_MIN_TYPE]    = ldlm_ibits_policy_wire_to_local,
};

static ldlm_policy_local_to_wire_t ldlm_policy_local_to_wire[] = {
        [LDLM_PLAIN - LDLM_MIN_TYPE]    = ldlm_plain_policy_local_to_wire,
        [LDLM_EXTENT - LDLM_MIN_TYPE]   = ldlm_extent_policy_local_to_wire,
        [LDLM_FLOCK - LDLM_MIN_TYPE]    = ldlm_flock_policy_local_to_wire,
        [LDLM_IBITS - LDLM_MIN_TYPE]    = ldlm_ibits_policy_local_to_wire,
};

/**
 * Converts lock policy from local format to on the wire lock_desc format
 */
void ldlm_convert_policy_to_wire(ldlm_type_t type,
                                 const ldlm_policy_data_t *lpolicy,
                                 ldlm_wire_policy_data_t *wpolicy)
{
        ldlm_policy_local_to_wire_t convert;

        convert = ldlm_policy_local_to_wire[type - LDLM_MIN_TYPE];

        convert(lpolicy, wpolicy);
}

/**
 * Converts lock policy from on the wire lock_desc format to local format
 */
void ldlm_convert_policy_to_local(struct obd_export *exp, ldlm_type_t type,
                                  const ldlm_wire_policy_data_t *wpolicy,
                                  ldlm_policy_data_t *lpolicy)
{
        ldlm_policy_wire_to_local_t convert;
        int new_client;

        /** some badness for 2.0.0 clients, but 2.0.0 isn't supported */
        new_client = (exp_connect_flags(exp) & OBD_CONNECT_FULL20) != 0;
        if (new_client)
                convert = ldlm_policy_wire21_to_local[type - LDLM_MIN_TYPE];
        else
                convert = ldlm_policy_wire18_to_local[type - LDLM_MIN_TYPE];

        convert(wpolicy, lpolicy);
}

char *ldlm_it2str(int it)
{
        switch (it) {
        case IT_OPEN:
                return "open";
        case IT_CREAT:
                return "creat";
        case (IT_OPEN | IT_CREAT):
                return "open|creat";
        case IT_READDIR:
                return "readdir";
        case IT_GETATTR:
                return "getattr";
        case IT_LOOKUP:
                return "lookup";
        case IT_UNLINK:
                return "unlink";
        case IT_GETXATTR:
                return "getxattr";
        case IT_LAYOUT:
                return "layout";
        default:
                CERROR("Unknown intent %d\n", it);
                return "UNKNOWN";
        }
}
EXPORT_SYMBOL(ldlm_it2str);


void ldlm_register_intent(struct ldlm_namespace *ns, ldlm_res_policy arg)
{
        ns->ns_policy = arg;
}
EXPORT_SYMBOL(ldlm_register_intent);

/*
 * REFCOUNTED LOCK OBJECTS
 */


/**
 * Get a reference on a lock.
 *
 * Lock refcounts, during creation:
 *   - one special one for allocation, dec'd only once in destroy
 *   - one for being a lock that's in-use
 *   - one for the addref associated with a new lock
 */
struct ldlm_lock *ldlm_lock_get(struct ldlm_lock *lock)
{
        atomic_inc(&lock->l_refc);
        return lock;
}
EXPORT_SYMBOL(ldlm_lock_get);

/**
 * Release lock reference.
 *
 * Also frees the lock if it was last reference.
 */
void ldlm_lock_put(struct ldlm_lock *lock)
{
        LASSERT(lock->l_resource != LP_POISON);
        LASSERT(atomic_read(&lock->l_refc) > 0);
        if (atomic_dec_and_test(&lock->l_refc)) {
                struct ldlm_resource *res;

                LDLM_DEBUG(lock,
                           "final lock_put on destroyed lock, freeing it.");

                res = lock->l_resource;
                LASSERT(lock->l_flags & LDLM_FL_DESTROYED);
                LASSERT(list_empty(&lock->l_res_link));
                LASSERT(list_empty(&lock->l_pending_chain));

                lprocfs_counter_decr(ldlm_res_to_ns(res)->ns_stats,
                                     LDLM_NSS_LOCKS);
                lu_ref_del(&res->lr_reference, "lock", lock);
                ldlm_resource_putref(res);
                lock->l_resource = NULL;
                if (lock->l_export) {
                        class_export_lock_put(lock->l_export, lock);
                        lock->l_export = NULL;
                }

                kfree(lock->l_lvb_data);

                ldlm_interval_free(ldlm_interval_detach(lock));
                lu_ref_fini(&lock->l_reference);
                OBD_FREE_RCU(lock, sizeof(*lock), &lock->l_handle);
        }
}
EXPORT_SYMBOL(ldlm_lock_put);

/**
 * Removes LDLM lock \a lock from LRU. Assumes LRU is already locked.
 */
int ldlm_lock_remove_from_lru_nolock(struct ldlm_lock *lock)
{
        int rc = 0;

        if (!list_empty(&lock->l_lru)) {
                struct ldlm_namespace *ns = ldlm_lock_to_ns(lock);

                LASSERT(lock->l_resource->lr_type != LDLM_FLOCK);
                list_del_init(&lock->l_lru);
                LASSERT(ns->ns_nr_unused > 0);
                ns->ns_nr_unused--;
                rc = 1;
        }
        return rc;
}

/**
 * Removes LDLM lock \a lock from LRU. Obtains the LRU lock first.
 */
int ldlm_lock_remove_from_lru(struct ldlm_lock *lock)
{
        struct ldlm_namespace *ns = ldlm_lock_to_ns(lock);
        int rc;

        if (lock->l_flags & LDLM_FL_NS_SRV) {
                LASSERT(list_empty(&lock->l_lru));
                return 0;
        }

        spin_lock(&ns->ns_lock);
        rc = ldlm_lock_remove_from_lru_nolock(lock);
        spin_unlock(&ns->ns_lock);
        return rc;
}

/**
 * Adds LDLM lock \a lock to namespace LRU. Assumes LRU is already locked.
 */
void ldlm_lock_add_to_lru_nolock(struct ldlm_lock *lock)
{
        struct ldlm_namespace *ns = ldlm_lock_to_ns(lock);

        lock->l_last_used = cfs_time_current();
        LASSERT(list_empty(&lock->l_lru));
        LASSERT(lock->l_resource->lr_type != LDLM_FLOCK);
        list_add_tail(&lock->l_lru, &ns->ns_unused_list);
        if (lock->l_flags & LDLM_FL_SKIPPED)
                lock->l_flags &= ~LDLM_FL_SKIPPED;
        LASSERT(ns->ns_nr_unused >= 0);
        ns->ns_nr_unused++;
}

/**
 * Adds LDLM lock \a lock to namespace LRU. Obtains necessary LRU locks
 * first.
 */
void ldlm_lock_add_to_lru(struct ldlm_lock *lock)
{
        struct ldlm_namespace *ns = ldlm_lock_to_ns(lock);

        spin_lock(&ns->ns_lock);
        ldlm_lock_add_to_lru_nolock(lock);
        spin_unlock(&ns->ns_lock);
}

/**
 * Moves LDLM lock \a lock that is already in namespace LRU to the tail of
 * the LRU. Performs necessary LRU locking
 */
void ldlm_lock_touch_in_lru(struct ldlm_lock *lock)
{
        struct ldlm_namespace *ns = ldlm_lock_to_ns(lock);

        if (lock->l_flags & LDLM_FL_NS_SRV) {
                LASSERT(list_empty(&lock->l_lru));
                return;
        }

        spin_lock(&ns->ns_lock);
        if (!list_empty(&lock->l_lru)) {
                ldlm_lock_remove_from_lru_nolock(lock);
                ldlm_lock_add_to_lru_nolock(lock);
        }
        spin_unlock(&ns->ns_lock);
}

/**
 * Helper to destroy a locked lock.
 *
 * Used by ldlm_lock_destroy and ldlm_lock_destroy_nolock
 * Must be called with l_lock and lr_lock held.
 *
 * Does not actually free the lock data, but rather marks the lock as
 * destroyed by setting l_destroyed field in the lock to 1.  Destroys a
 * handle->lock association too, so that the lock can no longer be found
 * and removes the lock from LRU list.  Actual lock freeing occurs when
 * last lock reference goes away.
 *
 * Original comment (of some historical value):
 * This used to have a 'strict' flag, which recovery would use to mark an
 * in-use lock as needing-to-die.  Lest I am ever tempted to put it back, I
 * shall explain why it's gone: with the new hash table scheme, once you call
 * ldlm_lock_destroy, you can never drop your final references on this lock.
 * Because it's not in the hash table anymore.  -phil
 */
int ldlm_lock_destroy_internal(struct ldlm_lock *lock)
{
        if (lock->l_readers || lock->l_writers) {
                LDLM_ERROR(lock, "lock still has references");
                LBUG();
        }

        if (!list_empty(&lock->l_res_link)) {
                LDLM_ERROR(lock, "lock still on resource");
                LBUG();
        }

        if (lock->l_flags & LDLM_FL_DESTROYED) {
                LASSERT(list_empty(&lock->l_lru));
                return 0;
        }
        lock->l_flags |= LDLM_FL_DESTROYED;

        if (lock->l_export && lock->l_export->exp_lock_hash) {
                /* NB: it's safe to call cfs_hash_del() even lock isn't
                 * in exp_lock_hash. */
                /* In the function below, .hs_keycmp resolves to
                 * ldlm_export_lock_keycmp() */
                /* coverity[overrun-buffer-val] */
                cfs_hash_del(lock->l_export->exp_lock_hash,
                             &lock->l_remote_handle, &lock->l_exp_hash);
        }

        ldlm_lock_remove_from_lru(lock);
        class_handle_unhash(&lock->l_handle);

#if 0
        /* Wake anyone waiting for this lock */
        /* FIXME: I should probably add yet another flag, instead of using
         * l_export to only call this on clients */
        if (lock->l_export)
                class_export_put(lock->l_export);
        lock->l_export = NULL;
        if (lock->l_export && lock->l_completion_ast)
                lock->l_completion_ast(lock, 0);
#endif
        return 1;
}

/**
 * Destroys a LDLM lock \a lock. Performs necessary locking first.
 */
void ldlm_lock_destroy(struct ldlm_lock *lock)
{
        int first;

        lock_res_and_lock(lock);
        first = ldlm_lock_destroy_internal(lock);
        unlock_res_and_lock(lock);

        /* drop reference from hashtable only for first destroy */
        if (first) {
                lu_ref_del(&lock->l_reference, "hash", lock);
                LDLM_LOCK_RELEASE(lock);
        }
}

/**
 * Destroys a LDLM lock \a lock that is already locked.
 */
void ldlm_lock_destroy_nolock(struct ldlm_lock *lock)
{
        int first;

        first = ldlm_lock_destroy_internal(lock);
        /* drop reference from hashtable only for first destroy */
        if (first) {
                lu_ref_del(&lock->l_reference, "hash", lock);
                LDLM_LOCK_RELEASE(lock);
        }
}

/* this is called by portals_handle2object with the handle lock taken */
static void lock_handle_addref(void *lock)
{
        LDLM_LOCK_GET((struct ldlm_lock *)lock);
}

static void lock_handle_free(void *lock, int size)
{
        LASSERT(size == sizeof(struct ldlm_lock));
        OBD_SLAB_FREE(lock, ldlm_lock_slab, size);
}

struct portals_handle_ops lock_handle_ops = {
        .hop_addref = lock_handle_addref,
        .hop_free   = lock_handle_free,
};

/**
 *
 * Allocate and initialize new lock structure.
 *
 * usage: pass in a resource on which you have done ldlm_resource_get
 *      new lock will take over the refcount.
 * returns: lock with refcount 2 - one for current caller and one for remote
 */
static struct ldlm_lock *ldlm_lock_new(struct ldlm_resource *resource)
{
        struct ldlm_lock *lock;

        if (resource == NULL)
                LBUG();

        OBD_SLAB_ALLOC_PTR_GFP(lock, ldlm_lock_slab, GFP_NOFS);
        if (lock == NULL)
                return NULL;

        spin_lock_init(&lock->l_lock);
        lock->l_resource = resource;
        lu_ref_add(&resource->lr_reference, "lock", lock);

        atomic_set(&lock->l_refc, 2);
        INIT_LIST_HEAD(&lock->l_res_link);
        INIT_LIST_HEAD(&lock->l_lru);
        INIT_LIST_HEAD(&lock->l_pending_chain);
        INIT_LIST_HEAD(&lock->l_bl_ast);
        INIT_LIST_HEAD(&lock->l_cp_ast);
        INIT_LIST_HEAD(&lock->l_rk_ast);
        init_waitqueue_head(&lock->l_waitq);
        lock->l_blocking_lock = NULL;
        INIT_LIST_HEAD(&lock->l_sl_mode);
        INIT_LIST_HEAD(&lock->l_sl_policy);
        INIT_HLIST_NODE(&lock->l_exp_hash);
        INIT_HLIST_NODE(&lock->l_exp_flock_hash);

        lprocfs_counter_incr(ldlm_res_to_ns(resource)->ns_stats,
                             LDLM_NSS_LOCKS);
        INIT_LIST_HEAD(&lock->l_handle.h_link);
        class_handle_hash(&lock->l_handle, &lock_handle_ops);

        lu_ref_init(&lock->l_reference);
        lu_ref_add(&lock->l_reference, "hash", lock);
        lock->l_callback_timeout = 0;

#if LUSTRE_TRACKS_LOCK_EXP_REFS
        INIT_LIST_HEAD(&lock->l_exp_refs_link);
        lock->l_exp_refs_nr = 0;
        lock->l_exp_refs_target = NULL;
#endif
        INIT_LIST_HEAD(&lock->l_exp_list);

        return lock;
}

/**
 * Moves LDLM lock \a lock to another resource.
 * This is used on client when server returns some other lock than requested
 * (typically as a result of intent operation)
 */
int ldlm_lock_change_resource(struct ldlm_namespace *ns, struct ldlm_lock *lock,
                              const struct ldlm_res_id *new_resid)
{
        struct ldlm_resource *oldres = lock->l_resource;
        struct ldlm_resource *newres;
        int type;

        LASSERT(ns_is_client(ns));

        lock_res_and_lock(lock);
        if (memcmp(new_resid, &lock->l_resource->lr_name,
                   sizeof(lock->l_resource->lr_name)) == 0) {
                /* Nothing to do */
                unlock_res_and_lock(lock);
                return 0;
        }

        LASSERT(new_resid->name[0] != 0);

        /* This function assumes that the lock isn't on any lists */
        LASSERT(list_empty(&lock->l_res_link));

        type = oldres->lr_type;
        unlock_res_and_lock(lock);

        newres = ldlm_resource_get(ns, NULL, new_resid, type, 1);
        if (newres == NULL)
                return -ENOMEM;

        lu_ref_add(&newres->lr_reference, "lock", lock);
        /*
         * To flip the lock from the old to the new resource, lock, oldres and
         * newres have to be locked. Resource spin-locks are nested within
         * lock->l_lock, and are taken in the memory address order to avoid
         * dead-locks.
         */
        spin_lock(&lock->l_lock);
        oldres = lock->l_resource;
        if (oldres < newres) {
                lock_res(oldres);
                lock_res_nested(newres, LRT_NEW);
        } else {
                lock_res(newres);
                lock_res_nested(oldres, LRT_NEW);
        }
        LASSERT(memcmp(new_resid, &oldres->lr_name,
                       sizeof(oldres->lr_name)) != 0);
        lock->l_resource = newres;
        unlock_res(oldres);
        unlock_res_and_lock(lock);

        /* ...and the flowers are still standing! */
        lu_ref_del(&oldres->lr_reference, "lock", lock);
        ldlm_resource_putref(oldres);

        return 0;
}
EXPORT_SYMBOL(ldlm_lock_change_resource);

/** \defgroup ldlm_handles LDLM HANDLES
 * Ways to get hold of locks without any addresses.
 * @{
 */

/**
 * Fills in handle for LDLM lock \a lock into supplied \a lockh
 * Does not take any references.
 */
void ldlm_lock2handle(const struct ldlm_lock *lock, struct lustre_handle *lockh)
{
        lockh->cookie = lock->l_handle.h_cookie;
}
EXPORT_SYMBOL(ldlm_lock2handle);

/**
 * Obtain a lock reference by handle.
 *
 * if \a flags: atomically get the lock and set the flags.
 *            Return NULL if flag already set
 */
struct ldlm_lock *__ldlm_handle2lock(const struct lustre_handle *handle,
                                     __u64 flags)
{
        struct ldlm_lock *lock;

        LASSERT(handle);

        lock = class_handle2object(handle->cookie);
        if (lock == NULL)
                return NULL;

        /* It's unlikely but possible that someone marked the lock as
         * destroyed after we did handle2object on it */
        if (flags == 0 && ((lock->l_flags & LDLM_FL_DESTROYED) == 0)) {
                lu_ref_add(&lock->l_reference, "handle", current);
                return lock;
        }

        lock_res_and_lock(lock);

        LASSERT(lock->l_resource != NULL);

        lu_ref_add_atomic(&lock->l_reference, "handle", current);
        if (unlikely(lock->l_flags & LDLM_FL_DESTROYED)) {
                unlock_res_and_lock(lock);
                CDEBUG(D_INFO, "lock already destroyed: lock %p\n", lock);
                LDLM_LOCK_PUT(lock);
                return NULL;
        }

        if (flags && (lock->l_flags & flags)) {
                unlock_res_and_lock(lock);
                LDLM_LOCK_PUT(lock);
                return NULL;
        }

        if (flags)
                lock->l_flags |= flags;

        unlock_res_and_lock(lock);
        return lock;
}
EXPORT_SYMBOL(__ldlm_handle2lock);
/** @} ldlm_handles */

/**
 * Fill in "on the wire" representation for given LDLM lock into supplied
 * lock descriptor \a desc structure.
 */
void ldlm_lock2desc(struct ldlm_lock *lock, struct ldlm_lock_desc *desc)
{
        ldlm_res2desc(lock->l_resource, &desc->l_resource);
        desc->l_req_mode = lock->l_req_mode;
        desc->l_granted_mode = lock->l_granted_mode;
        ldlm_convert_policy_to_wire(lock->l_resource->lr_type,
                                    &lock->l_policy_data,
                                    &desc->l_policy_data);
}
EXPORT_SYMBOL(ldlm_lock2desc);

/**
 * Add a lock to list of conflicting locks to send AST to.
 *
 * Only add if we have not sent a blocking AST to the lock yet.
 */
void ldlm_add_bl_work_item(struct ldlm_lock *lock, struct ldlm_lock *new,
                           struct list_head *work_list)
{
        if ((lock->l_flags & LDLM_FL_AST_SENT) == 0) {
                LDLM_DEBUG(lock, "lock incompatible; sending blocking AST.");
                lock->l_flags |= LDLM_FL_AST_SENT;
                /* If the enqueuing client said so, tell the AST recipient to
                 * discard dirty data, rather than writing back. */
                if (new->l_flags & LDLM_FL_AST_DISCARD_DATA)
                        lock->l_flags |= LDLM_FL_DISCARD_DATA;
                LASSERT(list_empty(&lock->l_bl_ast));
                list_add(&lock->l_bl_ast, work_list);
                LDLM_LOCK_GET(lock);
                LASSERT(lock->l_blocking_lock == NULL);
                lock->l_blocking_lock = LDLM_LOCK_GET(new);
        }
}

/**
 * Add a lock to list of just granted locks to send completion AST to.
 */
void ldlm_add_cp_work_item(struct ldlm_lock *lock, struct list_head *work_list)
{
        if ((lock->l_flags & LDLM_FL_CP_REQD) == 0) {
                lock->l_flags |= LDLM_FL_CP_REQD;
                LDLM_DEBUG(lock, "lock granted; sending completion AST.");
                LASSERT(list_empty(&lock->l_cp_ast));
                list_add(&lock->l_cp_ast, work_list);
                LDLM_LOCK_GET(lock);
        }
}

/**
 * Aggregator function to add AST work items into a list. Determines
 * what sort of an AST work needs to be done and calls the proper
 * adding function.
 * Must be called with lr_lock held.
 */
void ldlm_add_ast_work_item(struct ldlm_lock *lock, struct ldlm_lock *new,
                            struct list_head *work_list)
{
        check_res_locked(lock->l_resource);
        if (new)
                ldlm_add_bl_work_item(lock, new, work_list);
        else
                ldlm_add_cp_work_item(lock, work_list);
}

/**
 * Add specified reader/writer reference to LDLM lock with handle \a lockh.
 * r/w reference type is determined by \a mode
 * Calls ldlm_lock_addref_internal.
 */
void ldlm_lock_addref(struct lustre_handle *lockh, __u32 mode)
{
        struct ldlm_lock *lock;

        lock = ldlm_handle2lock(lockh);
        LASSERT(lock != NULL);
        ldlm_lock_addref_internal(lock, mode);
        LDLM_LOCK_PUT(lock);
}
EXPORT_SYMBOL(ldlm_lock_addref);

/**
 * Helper function.
 * Add specified reader/writer reference to LDLM lock \a lock.
 * r/w reference type is determined by \a mode
 * Removes lock from LRU if it is there.
 * Assumes the LDLM lock is already locked.
 */
void ldlm_lock_addref_internal_nolock(struct ldlm_lock *lock, __u32 mode)
{
        ldlm_lock_remove_from_lru(lock);
        if (mode & (LCK_NL | LCK_CR | LCK_PR)) {
                lock->l_readers++;
                lu_ref_add_atomic(&lock->l_reference, "reader", lock);
        }
        if (mode & (LCK_EX | LCK_CW | LCK_PW | LCK_GROUP | LCK_COS)) {
                lock->l_writers++;
                lu_ref_add_atomic(&lock->l_reference, "writer", lock);
        }
        LDLM_LOCK_GET(lock);
        lu_ref_add_atomic(&lock->l_reference, "user", lock);
        LDLM_DEBUG(lock, "ldlm_lock_addref(%s)", ldlm_lockname[mode]);
}

/**
 * Attempts to add reader/writer reference to a lock with handle \a lockh, and
 * fails if lock is already LDLM_FL_CBPENDING or destroyed.
 *
 * \retval 0 success, lock was addref-ed
 *
 * \retval -EAGAIN lock is being canceled.
 */
int ldlm_lock_addref_try(struct lustre_handle *lockh, __u32 mode)
{
        struct ldlm_lock *lock;
        int            result;

        result = -EAGAIN;
        lock = ldlm_handle2lock(lockh);
        if (lock != NULL) {
                lock_res_and_lock(lock);
                if (lock->l_readers != 0 || lock->l_writers != 0 ||
                    !(lock->l_flags & LDLM_FL_CBPENDING)) {
                        ldlm_lock_addref_internal_nolock(lock, mode);
                        result = 0;
                }
                unlock_res_and_lock(lock);
                LDLM_LOCK_PUT(lock);
        }
        return result;
}
EXPORT_SYMBOL(ldlm_lock_addref_try);

/**
 * Add specified reader/writer reference to LDLM lock \a lock.
 * Locks LDLM lock and calls ldlm_lock_addref_internal_nolock to do the work.
 * Only called for local locks.
 */
void ldlm_lock_addref_internal(struct ldlm_lock *lock, __u32 mode)
{
        lock_res_and_lock(lock);
        ldlm_lock_addref_internal_nolock(lock, mode);
        unlock_res_and_lock(lock);
}

/**
 * Removes reader/writer reference for LDLM lock \a lock.
 * Assumes LDLM lock is already locked.
 * only called in ldlm_flock_destroy and for local locks.
 * Does NOT add lock to LRU if no r/w references left to accommodate flock locks
 * that cannot be placed in LRU.
 */
void ldlm_lock_decref_internal_nolock(struct ldlm_lock *lock, __u32 mode)
{
        LDLM_DEBUG(lock, "ldlm_lock_decref(%s)", ldlm_lockname[mode]);
        if (mode & (LCK_NL | LCK_CR | LCK_PR)) {
                LASSERT(lock->l_readers > 0);
                lu_ref_del(&lock->l_reference, "reader", lock);
                lock->l_readers--;
        }
        if (mode & (LCK_EX | LCK_CW | LCK_PW | LCK_GROUP | LCK_COS)) {
                LASSERT(lock->l_writers > 0);
                lu_ref_del(&lock->l_reference, "writer", lock);
                lock->l_writers--;
        }

        lu_ref_del(&lock->l_reference, "user", lock);
        LDLM_LOCK_RELEASE(lock);    /* matches the LDLM_LOCK_GET() in addref */
}

/**
 * Removes reader/writer reference for LDLM lock \a lock.
 * Locks LDLM lock first.
 * If the lock is determined to be client lock on a client and r/w refcount
 * drops to zero and the lock is not blocked, the lock is added to LRU lock
 * on the namespace.
 * For blocked LDLM locks if r/w count drops to zero, blocking_ast is called.
 */
void ldlm_lock_decref_internal(struct ldlm_lock *lock, __u32 mode)
{
        struct ldlm_namespace *ns;

        lock_res_and_lock(lock);

        ns = ldlm_lock_to_ns(lock);

        ldlm_lock_decref_internal_nolock(lock, mode);

        if (lock->l_flags & LDLM_FL_LOCAL &&
            !lock->l_readers && !lock->l_writers) {
                /* If this is a local lock on a server namespace and this was
                 * the last reference, cancel the lock. */
                CDEBUG(D_INFO, "forcing cancel of local lock\n");
                lock->l_flags |= LDLM_FL_CBPENDING;
        }

        if (!lock->l_readers && !lock->l_writers &&
            (lock->l_flags & LDLM_FL_CBPENDING)) {
                /* If we received a blocked AST and this was the last reference,
                 * run the callback. */
                if ((lock->l_flags & LDLM_FL_NS_SRV) && lock->l_export)
                        CERROR("FL_CBPENDING set on non-local lock--just a warning\n");

                LDLM_DEBUG(lock, "final decref done on cbpending lock");

                LDLM_LOCK_GET(lock); /* dropped by bl thread */
                ldlm_lock_remove_from_lru(lock);
                unlock_res_and_lock(lock);

                if (lock->l_flags & LDLM_FL_FAIL_LOC)
                        OBD_RACE(OBD_FAIL_LDLM_CP_BL_RACE);

                if ((lock->l_flags & LDLM_FL_ATOMIC_CB) ||
                    ldlm_bl_to_thread_lock(ns, NULL, lock) != 0)
                        ldlm_handle_bl_callback(ns, NULL, lock);
        } else if (ns_is_client(ns) &&
                   !lock->l_readers && !lock->l_writers &&
                   !(lock->l_flags & LDLM_FL_NO_LRU) &&
                   !(lock->l_flags & LDLM_FL_BL_AST)) {

                LDLM_DEBUG(lock, "add lock into lru list");

                /* If this is a client-side namespace and this was the last
                 * reference, put it on the LRU. */
                ldlm_lock_add_to_lru(lock);
                unlock_res_and_lock(lock);

                if (lock->l_flags & LDLM_FL_FAIL_LOC)
                        OBD_RACE(OBD_FAIL_LDLM_CP_BL_RACE);

                /* Call ldlm_cancel_lru() only if EARLY_CANCEL and LRU RESIZE
                 * are not supported by the server, otherwise, it is done on
                 * enqueue. */
                if (!exp_connect_cancelset(lock->l_conn_export) &&
                    !ns_connect_lru_resize(ns))
                        ldlm_cancel_lru(ns, 0, LCF_ASYNC, 0);
        } else {
                LDLM_DEBUG(lock, "do not add lock into lru list");
                unlock_res_and_lock(lock);
        }
}

/**
 * Decrease reader/writer refcount for LDLM lock with handle \a lockh
 */
void ldlm_lock_decref(struct lustre_handle *lockh, __u32 mode)
{
        struct ldlm_lock *lock = __ldlm_handle2lock(lockh, 0);

        LASSERTF(lock != NULL, "Non-existing lock: %#llx\n", lockh->cookie);
        ldlm_lock_decref_internal(lock, mode);
        LDLM_LOCK_PUT(lock);
}
EXPORT_SYMBOL(ldlm_lock_decref);

/**
 * Decrease reader/writer refcount for LDLM lock with handle
 * \a lockh and mark it for subsequent cancellation once r/w refcount
 * drops to zero instead of putting into LRU.
 *
 * Typical usage is for GROUP locks which we cannot allow to be cached.
 */
void ldlm_lock_decref_and_cancel(struct lustre_handle *lockh, __u32 mode)
{
        struct ldlm_lock *lock = __ldlm_handle2lock(lockh, 0);

        LASSERT(lock != NULL);

        LDLM_DEBUG(lock, "ldlm_lock_decref(%s)", ldlm_lockname[mode]);
        lock_res_and_lock(lock);
        lock->l_flags |= LDLM_FL_CBPENDING;
        unlock_res_and_lock(lock);
        ldlm_lock_decref_internal(lock, mode);
        LDLM_LOCK_PUT(lock);
}
EXPORT_SYMBOL(ldlm_lock_decref_and_cancel);

struct sl_insert_point {
        struct list_head *res_link;
        struct list_head *mode_link;
        struct list_head *policy_link;
};

/**
 * Finds a position to insert the new lock into granted lock list.
 *
 * Used for locks eligible for skiplist optimization.
 *
 * Parameters:
 *      queue [input]:  the granted list where search acts on;
 *      req [input]:    the lock whose position to be located;
 *      prev [output]:  positions within 3 lists to insert @req to
 * Return Value:
 *      filled @prev
 * NOTE: called by
 *  - ldlm_grant_lock_with_skiplist
 */
static void search_granted_lock(struct list_head *queue,
                                struct ldlm_lock *req,
                                struct sl_insert_point *prev)
{
        struct list_head *tmp;
        struct ldlm_lock *lock, *mode_end, *policy_end;

        list_for_each(tmp, queue) {
                lock = list_entry(tmp, struct ldlm_lock, l_res_link);

                mode_end = list_entry(lock->l_sl_mode.prev,
                                          struct ldlm_lock, l_sl_mode);

                if (lock->l_req_mode != req->l_req_mode) {
                        /* jump to last lock of mode group */
                        tmp = &mode_end->l_res_link;
                        continue;
                }

                /* suitable mode group is found */
                if (lock->l_resource->lr_type == LDLM_PLAIN) {
                        /* insert point is last lock of the mode group */
                        prev->res_link = &mode_end->l_res_link;
                        prev->mode_link = &mode_end->l_sl_mode;
                        prev->policy_link = &req->l_sl_policy;
                        return;
                } else if (lock->l_resource->lr_type == LDLM_IBITS) {
                        for (;;) {
                                policy_end =
                                        list_entry(lock->l_sl_policy.prev,
                                                       struct ldlm_lock,
                                                       l_sl_policy);

                                if (lock->l_policy_data.l_inodebits.bits ==
                                    req->l_policy_data.l_inodebits.bits) {
                                        /* insert point is last lock of
                                         * the policy group */
                                        prev->res_link =
                                                &policy_end->l_res_link;
                                        prev->mode_link =
                                                &policy_end->l_sl_mode;
                                        prev->policy_link =
                                                &policy_end->l_sl_policy;
                                        return;
                                }

                                if (policy_end == mode_end)
                                        /* done with mode group */
                                        break;

                                /* go to next policy group within mode group */
                                tmp = policy_end->l_res_link.next;
                                lock = list_entry(tmp, struct ldlm_lock,
                                                      l_res_link);
                        }  /* loop over policy groups within the mode group */

                        /* insert point is last lock of the mode group,
                         * new policy group is started */
                        prev->res_link = &mode_end->l_res_link;
                        prev->mode_link = &mode_end->l_sl_mode;
                        prev->policy_link = &req->l_sl_policy;
                        return;
                } else {
                        LDLM_ERROR(lock,
                                   "is not LDLM_PLAIN or LDLM_IBITS lock");
                        LBUG();
                }
        }

        /* insert point is last lock on the queue,
         * new mode group and new policy group are started */
        prev->res_link = queue->prev;
        prev->mode_link = &req->l_sl_mode;
        prev->policy_link = &req->l_sl_policy;
}

/**
 * Add a lock into resource granted list after a position described by
 * \a prev.
 */
static void ldlm_granted_list_add_lock(struct ldlm_lock *lock,
                                       struct sl_insert_point *prev)
{
        struct ldlm_resource *res = lock->l_resource;

        check_res_locked(res);

        ldlm_resource_dump(D_INFO, res);
        LDLM_DEBUG(lock, "About to add lock:");

        if (lock->l_flags & LDLM_FL_DESTROYED) {
                CDEBUG(D_OTHER, "Lock destroyed, not adding to resource\n");
                return;
        }

        LASSERT(list_empty(&lock->l_res_link));
        LASSERT(list_empty(&lock->l_sl_mode));
        LASSERT(list_empty(&lock->l_sl_policy));

        /*
         * lock->link == prev->link means lock is first starting the group.
         * Don't re-add to itself to suppress kernel warnings.
         */
        if (&lock->l_res_link != prev->res_link)
                list_add(&lock->l_res_link, prev->res_link);
        if (&lock->l_sl_mode != prev->mode_link)
                list_add(&lock->l_sl_mode, prev->mode_link);
        if (&lock->l_sl_policy != prev->policy_link)
                list_add(&lock->l_sl_policy, prev->policy_link);
}

/**
 * Add a lock to granted list on a resource maintaining skiplist
 * correctness.
 */
static void ldlm_grant_lock_with_skiplist(struct ldlm_lock *lock)
{
        struct sl_insert_point prev;

        LASSERT(lock->l_req_mode == lock->l_granted_mode);

        search_granted_lock(&lock->l_resource->lr_granted, lock, &prev);
        ldlm_granted_list_add_lock(lock, &prev);
}

/**
 * Perform lock granting bookkeeping.
 *
 * Includes putting the lock into granted list and updating lock mode.
 * NOTE: called by
 *  - ldlm_lock_enqueue
 *  - ldlm_reprocess_queue
 *  - ldlm_lock_convert
 *
 * must be called with lr_lock held
 */
void ldlm_grant_lock(struct ldlm_lock *lock, struct list_head *work_list)
{
        struct ldlm_resource *res = lock->l_resource;

        check_res_locked(res);

        lock->l_granted_mode = lock->l_req_mode;
        if (res->lr_type == LDLM_PLAIN || res->lr_type == LDLM_IBITS)
                ldlm_grant_lock_with_skiplist(lock);
        else if (res->lr_type == LDLM_EXTENT)
                ldlm_extent_add_lock(res, lock);
        else
                ldlm_resource_add_lock(res, &res->lr_granted, lock);

        if (lock->l_granted_mode < res->lr_most_restr)
                res->lr_most_restr = lock->l_granted_mode;

        if (work_list && lock->l_completion_ast != NULL)
                ldlm_add_ast_work_item(lock, NULL, work_list);

        ldlm_pool_add(&ldlm_res_to_ns(res)->ns_pool, lock);
}

/**
 * Search for a lock with given properties in a queue.
 *
 * \retval a referenced lock or NULL.  See the flag descriptions below, in the
 * comment above ldlm_lock_match
 */
static struct ldlm_lock *search_queue(struct list_head *queue,
                                      ldlm_mode_t *mode,
                                      ldlm_policy_data_t *policy,
                                      struct ldlm_lock *old_lock,
                                      __u64 flags, int unref)
{
        struct ldlm_lock *lock;
        struct list_head       *tmp;

        list_for_each(tmp, queue) {
                ldlm_mode_t match;

                lock = list_entry(tmp, struct ldlm_lock, l_res_link);

                if (lock == old_lock)
                        break;

                /* Check if this lock can be matched.
                 * Used by LU-2919(exclusive open) for open lease lock */
                if (ldlm_is_excl(lock))
                        continue;

                /* llite sometimes wants to match locks that will be
                 * canceled when their users drop, but we allow it to match
                 * if it passes in CBPENDING and the lock still has users.
                 * this is generally only going to be used by children
                 * whose parents already hold a lock so forward progress
                 * can still happen. */
                if (lock->l_flags & LDLM_FL_CBPENDING &&
                    !(flags & LDLM_FL_CBPENDING))
                        continue;
                if (!unref && lock->l_flags & LDLM_FL_CBPENDING &&
                    lock->l_readers == 0 && lock->l_writers == 0)
                        continue;

                if (!(lock->l_req_mode & *mode))
                        continue;
                match = lock->l_req_mode;

                if (lock->l_resource->lr_type == LDLM_EXTENT &&
                    (lock->l_policy_data.l_extent.start >
                     policy->l_extent.start ||
                     lock->l_policy_data.l_extent.end < policy->l_extent.end))
                        continue;

                if (unlikely(match == LCK_GROUP) &&
                    lock->l_resource->lr_type == LDLM_EXTENT &&
                    lock->l_policy_data.l_extent.gid != policy->l_extent.gid)
                        continue;

                /* We match if we have existing lock with same or wider set
                   of bits. */
                if (lock->l_resource->lr_type == LDLM_IBITS &&
                     ((lock->l_policy_data.l_inodebits.bits &
                      policy->l_inodebits.bits) !=
                      policy->l_inodebits.bits))
                        continue;

                if (!unref && (lock->l_flags & LDLM_FL_GONE_MASK))
                        continue;

                if ((flags & LDLM_FL_LOCAL_ONLY) &&
                    !(lock->l_flags & LDLM_FL_LOCAL))
                        continue;

                if (flags & LDLM_FL_TEST_LOCK) {
                        LDLM_LOCK_GET(lock);
                        ldlm_lock_touch_in_lru(lock);
                } else {
                        ldlm_lock_addref_internal_nolock(lock, match);
                }
                *mode = match;
                return lock;
        }

        return NULL;
}

void ldlm_lock_fail_match_locked(struct ldlm_lock *lock)
{
        if ((lock->l_flags & LDLM_FL_FAIL_NOTIFIED) == 0) {
                lock->l_flags |= LDLM_FL_FAIL_NOTIFIED;
                wake_up_all(&lock->l_waitq);
        }
}
EXPORT_SYMBOL(ldlm_lock_fail_match_locked);

void ldlm_lock_fail_match(struct ldlm_lock *lock)
{
        lock_res_and_lock(lock);
        ldlm_lock_fail_match_locked(lock);
        unlock_res_and_lock(lock);
}
EXPORT_SYMBOL(ldlm_lock_fail_match);

/**
 * Mark lock as "matchable" by OST.
 *
 * Used to prevent certain races in LOV/OSC where the lock is granted, but LVB
 * is not yet valid.
 * Assumes LDLM lock is already locked.
 */
void ldlm_lock_allow_match_locked(struct ldlm_lock *lock)
{
        lock->l_flags |= LDLM_FL_LVB_READY;
        wake_up_all(&lock->l_waitq);
}
EXPORT_SYMBOL(ldlm_lock_allow_match_locked);

/**
 * Mark lock as "matchable" by OST.
 * Locks the lock and then \see ldlm_lock_allow_match_locked
 */
void ldlm_lock_allow_match(struct ldlm_lock *lock)
{
        lock_res_and_lock(lock);
        ldlm_lock_allow_match_locked(lock);
        unlock_res_and_lock(lock);
}
EXPORT_SYMBOL(ldlm_lock_allow_match);

/**
 * Attempt to find a lock with specified properties.
 *
 * Typically returns a reference to matched lock unless LDLM_FL_TEST_LOCK is
 * set in \a flags
 *
 * Can be called in two ways:
 *
 * If 'ns' is NULL, then lockh describes an existing lock that we want to look
 * for a duplicate of.
 *
 * Otherwise, all of the fields must be filled in, to match against.
 *
 * If 'flags' contains LDLM_FL_LOCAL_ONLY, then only match local locks on the
 *     server (ie, connh is NULL)
 * If 'flags' contains LDLM_FL_BLOCK_GRANTED, then only locks on the granted
 *     list will be considered
 * If 'flags' contains LDLM_FL_CBPENDING, then locks that have been marked
 *     to be canceled can still be matched as long as they still have reader
 *     or writer referneces
 * If 'flags' contains LDLM_FL_TEST_LOCK, then don't actually reference a lock,
 *     just tell us if we would have matched.
 *
 * \retval 1 if it finds an already-existing lock that is compatible; in this
 * case, lockh is filled in with a addref()ed lock
 *
 * We also check security context, and if that fails we simply return 0 (to
 * keep caller code unchanged), the context failure will be discovered by
 * caller sometime later.
 */
ldlm_mode_t ldlm_lock_match(struct ldlm_namespace *ns, __u64 flags,
                            const struct ldlm_res_id *res_id, ldlm_type_t type,
                            ldlm_policy_data_t *policy, ldlm_mode_t mode,
                            struct lustre_handle *lockh, int unref)
{
        struct ldlm_resource *res;
        struct ldlm_lock *lock, *old_lock = NULL;
        int rc = 0;

        if (ns == NULL) {
                old_lock = ldlm_handle2lock(lockh);
                LASSERT(old_lock);

                ns = ldlm_lock_to_ns(old_lock);
                res_id = &old_lock->l_resource->lr_name;
                type = old_lock->l_resource->lr_type;
                mode = old_lock->l_req_mode;
        }

        res = ldlm_resource_get(ns, NULL, res_id, type, 0);
        if (res == NULL) {
                LASSERT(old_lock == NULL);
                return 0;
        }

        LDLM_RESOURCE_ADDREF(res);
        lock_res(res);

        lock = search_queue(&res->lr_granted, &mode, policy, old_lock,
                            flags, unref);
        if (lock != NULL) {
                rc = 1;
                goto out;
        }
        if (flags & LDLM_FL_BLOCK_GRANTED) {
                rc = 0;
                goto out;
        }
        lock = search_queue(&res->lr_converting, &mode, policy, old_lock,
                            flags, unref);
        if (lock != NULL) {
                rc = 1;
                goto out;
        }
        lock = search_queue(&res->lr_waiting, &mode, policy, old_lock,
                            flags, unref);
        if (lock != NULL) {
                rc = 1;
                goto out;
        }

 out:
        unlock_res(res);
        LDLM_RESOURCE_DELREF(res);
        ldlm_resource_putref(res);

        if (lock) {
                ldlm_lock2handle(lock, lockh);
                if ((flags & LDLM_FL_LVB_READY) &&
                    (!(lock->l_flags & LDLM_FL_LVB_READY))) {
                        __u64 wait_flags = LDLM_FL_LVB_READY |
                                LDLM_FL_DESTROYED | LDLM_FL_FAIL_NOTIFIED;
                        struct l_wait_info lwi;

                        if (lock->l_completion_ast) {
                                int err = lock->l_completion_ast(lock,
                                                          LDLM_FL_WAIT_NOREPROC,
                                                                 NULL);
                                if (err) {
                                        if (flags & LDLM_FL_TEST_LOCK)
                                                LDLM_LOCK_RELEASE(lock);
                                        else
                                                ldlm_lock_decref_internal(lock,
                                                                          mode);
                                        rc = 0;
                                        goto out2;
                                }
                        }

                        lwi = LWI_TIMEOUT_INTR(cfs_time_seconds(obd_timeout),
                                               NULL, LWI_ON_SIGNAL_NOOP, NULL);

                        /* XXX FIXME see comment on CAN_MATCH in lustre_dlm.h */
                        l_wait_event(lock->l_waitq,
                                     lock->l_flags & wait_flags,
                                     &lwi);
                        if (!(lock->l_flags & LDLM_FL_LVB_READY)) {
                                if (flags & LDLM_FL_TEST_LOCK)
                                        LDLM_LOCK_RELEASE(lock);
                                else
                                        ldlm_lock_decref_internal(lock, mode);
                                rc = 0;
                        }
                }
        }
 out2:
        if (rc) {
                LDLM_DEBUG(lock, "matched (%llu %llu)",
                           (type == LDLM_PLAIN || type == LDLM_IBITS) ?
                                res_id->name[2] : policy->l_extent.start,
                           (type == LDLM_PLAIN || type == LDLM_IBITS) ?
                                res_id->name[3] : policy->l_extent.end);

                /* check user's security context */
                if (lock->l_conn_export &&
                    sptlrpc_import_check_ctx(
                                class_exp2cliimp(lock->l_conn_export))) {
                        if (!(flags & LDLM_FL_TEST_LOCK))
                                ldlm_lock_decref_internal(lock, mode);
                        rc = 0;
                }

                if (flags & LDLM_FL_TEST_LOCK)
                        LDLM_LOCK_RELEASE(lock);

        } else if (!(flags & LDLM_FL_TEST_LOCK)) {/*less verbose for test-only*/
                LDLM_DEBUG_NOLOCK("not matched ns %p type %u mode %u res %llu/%llu (%llu %llu)",
                                  ns, type, mode, res_id->name[0],
                                  res_id->name[1],
                                  (type == LDLM_PLAIN || type == LDLM_IBITS) ?
                                        res_id->name[2] : policy->l_extent.start,
                                  (type == LDLM_PLAIN || type == LDLM_IBITS) ?
                                        res_id->name[3] : policy->l_extent.end);
        }
        if (old_lock)
                LDLM_LOCK_PUT(old_lock);

        return rc ? mode : 0;
}
EXPORT_SYMBOL(ldlm_lock_match);

ldlm_mode_t ldlm_revalidate_lock_handle(struct lustre_handle *lockh,
                                        __u64 *bits)
{
        struct ldlm_lock *lock;
        ldlm_mode_t mode = 0;

        lock = ldlm_handle2lock(lockh);
        if (lock != NULL) {
                lock_res_and_lock(lock);
                if (lock->l_flags & LDLM_FL_GONE_MASK)
                        goto out;

                if (lock->l_flags & LDLM_FL_CBPENDING &&
                    lock->l_readers == 0 && lock->l_writers == 0)
                        goto out;

                if (bits)
                        *bits = lock->l_policy_data.l_inodebits.bits;
                mode = lock->l_granted_mode;
                ldlm_lock_addref_internal_nolock(lock, mode);
        }

out:
        if (lock != NULL) {
                unlock_res_and_lock(lock);
                LDLM_LOCK_PUT(lock);
        }
        return mode;
}
EXPORT_SYMBOL(ldlm_revalidate_lock_handle);

/** The caller must guarantee that the buffer is large enough. */
int ldlm_fill_lvb(struct ldlm_lock *lock, struct req_capsule *pill,
                  enum req_location loc, void *data, int size)
{
        void *lvb;

        LASSERT(data != NULL);
        LASSERT(size >= 0);

        switch (lock->l_lvb_type) {
        case LVB_T_OST:
                if (size == sizeof(struct ost_lvb)) {
                        if (loc == RCL_CLIENT)
                                lvb = req_capsule_client_swab_get(pill,
                                                &RMF_DLM_LVB,
                                                lustre_swab_ost_lvb);
                        else
                                lvb = req_capsule_server_swab_get(pill,
                                                &RMF_DLM_LVB,
                                                lustre_swab_ost_lvb);
                        if (unlikely(lvb == NULL)) {
                                LDLM_ERROR(lock, "no LVB");
                                return -EPROTO;
                        }

                        memcpy(data, lvb, size);
                } else if (size == sizeof(struct ost_lvb_v1)) {
                        struct ost_lvb *olvb = data;

                        if (loc == RCL_CLIENT)
                                lvb = req_capsule_client_swab_get(pill,
                                                &RMF_DLM_LVB,
                                                lustre_swab_ost_lvb_v1);
                        else
                                lvb = req_capsule_server_sized_swab_get(pill,
                                                &RMF_DLM_LVB, size,
                                                lustre_swab_ost_lvb_v1);
                        if (unlikely(lvb == NULL)) {
                                LDLM_ERROR(lock, "no LVB");
                                return -EPROTO;
                        }

                        memcpy(data, lvb, size);
                        olvb->lvb_mtime_ns = 0;
                        olvb->lvb_atime_ns = 0;
                        olvb->lvb_ctime_ns = 0;
                } else {
                        LDLM_ERROR(lock, "Replied unexpected ost LVB size %d",
                                   size);
                        return -EINVAL;
                }
                break;
        case LVB_T_LQUOTA:
                if (size == sizeof(struct lquota_lvb)) {
                        if (loc == RCL_CLIENT)
                                lvb = req_capsule_client_swab_get(pill,
                                                &RMF_DLM_LVB,
                                                lustre_swab_lquota_lvb);
                        else
                                lvb = req_capsule_server_swab_get(pill,
                                                &RMF_DLM_LVB,
                                                lustre_swab_lquota_lvb);
                        if (unlikely(lvb == NULL)) {
                                LDLM_ERROR(lock, "no LVB");
                                return -EPROTO;
                        }

                        memcpy(data, lvb, size);
                } else {
                        LDLM_ERROR(lock,
                                   "Replied unexpected lquota LVB size %d",
                                   size);
                        return -EINVAL;
                }
                break;
        case LVB_T_LAYOUT:
                if (size == 0)
                        break;

                if (loc == RCL_CLIENT)
                        lvb = req_capsule_client_get(pill, &RMF_DLM_LVB);
                else
                        lvb = req_capsule_server_get(pill, &RMF_DLM_LVB);
                if (unlikely(lvb == NULL)) {
                        LDLM_ERROR(lock, "no LVB");
                        return -EPROTO;
                }

                memcpy(data, lvb, size);
                break;
        default:
                LDLM_ERROR(lock, "Unknown LVB type: %d\n", lock->l_lvb_type);
                dump_stack();
                return -EINVAL;
        }

        return 0;
}

/**
 * Create and fill in new LDLM lock with specified properties.
 * Returns a referenced lock
 */
struct ldlm_lock *ldlm_lock_create(struct ldlm_namespace *ns,
                                   const struct ldlm_res_id *res_id,
                                   ldlm_type_t type,
                                   ldlm_mode_t mode,
                                   const struct ldlm_callback_suite *cbs,
                                   void *data, __u32 lvb_len,
                                   enum lvb_type lvb_type)
{
        struct ldlm_lock *lock;
        struct ldlm_resource *res;

        res = ldlm_resource_get(ns, NULL, res_id, type, 1);
        if (res == NULL)
                return NULL;

        lock = ldlm_lock_new(res);

        if (lock == NULL)
                return NULL;

        lock->l_req_mode = mode;
        lock->l_ast_data = data;
        lock->l_pid = current_pid();
        if (ns_is_server(ns))
                lock->l_flags |= LDLM_FL_NS_SRV;
        if (cbs) {
                lock->l_blocking_ast = cbs->lcs_blocking;
                lock->l_completion_ast = cbs->lcs_completion;
                lock->l_glimpse_ast = cbs->lcs_glimpse;
        }

        lock->l_tree_node = NULL;
        /* if this is the extent lock, allocate the interval tree node */
        if (type == LDLM_EXTENT) {
                if (ldlm_interval_alloc(lock) == NULL)
                        goto out;
        }

        if (lvb_len) {
                lock->l_lvb_len = lvb_len;
                lock->l_lvb_data = kzalloc(lvb_len, GFP_NOFS);
                if (lock->l_lvb_data == NULL)
                        goto out;
        }

        lock->l_lvb_type = lvb_type;
        if (OBD_FAIL_CHECK(OBD_FAIL_LDLM_NEW_LOCK))
                goto out;

        return lock;

out:
        ldlm_lock_destroy(lock);
        LDLM_LOCK_RELEASE(lock);
        return NULL;
}

/**
 * Enqueue (request) a lock.
 *
 * Does not block. As a result of enqueue the lock would be put
 * into granted or waiting list.
 *
 * If namespace has intent policy sent and the lock has LDLM_FL_HAS_INTENT flag
 * set, skip all the enqueueing and delegate lock processing to intent policy
 * function.
 */
ldlm_error_t ldlm_lock_enqueue(struct ldlm_namespace *ns,
                               struct ldlm_lock **lockp,
                               void *cookie, __u64 *flags)
{
        struct ldlm_lock *lock = *lockp;
        struct ldlm_resource *res = lock->l_resource;
        int local = ns_is_client(ldlm_res_to_ns(res));
        ldlm_error_t rc = ELDLM_OK;
        struct ldlm_interval *node = NULL;

        lock->l_last_activity = get_seconds();
        /* policies are not executed on the client or during replay */
        if ((*flags & (LDLM_FL_HAS_INTENT|LDLM_FL_REPLAY)) == LDLM_FL_HAS_INTENT
            && !local && ns->ns_policy) {
                rc = ns->ns_policy(ns, lockp, cookie, lock->l_req_mode, *flags,
                                   NULL);
                if (rc == ELDLM_LOCK_REPLACED) {
                        /* The lock that was returned has already been granted,
                         * and placed into lockp.  If it's not the same as the
                         * one we passed in, then destroy the old one and our
                         * work here is done. */
                        if (lock != *lockp) {
                                ldlm_lock_destroy(lock);
                                LDLM_LOCK_RELEASE(lock);
                        }
                        *flags |= LDLM_FL_LOCK_CHANGED;
                        return 0;
                } else if (rc != ELDLM_OK ||
                           (rc == ELDLM_OK && (*flags & LDLM_FL_INTENT_ONLY))) {
                        ldlm_lock_destroy(lock);
                        return rc;
                }
        }

        /* For a replaying lock, it might be already in granted list. So
         * unlinking the lock will cause the interval node to be freed, we
         * have to allocate the interval node early otherwise we can't regrant
         * this lock in the future. - jay */
        if (!local && (*flags & LDLM_FL_REPLAY) && res->lr_type == LDLM_EXTENT)
                OBD_SLAB_ALLOC_PTR_GFP(node, ldlm_interval_slab, GFP_NOFS);

        lock_res_and_lock(lock);
        if (local && lock->l_req_mode == lock->l_granted_mode) {
                /* The server returned a blocked lock, but it was granted
                 * before we got a chance to actually enqueue it.  We don't
                 * need to do anything else. */
                *flags &= ~(LDLM_FL_BLOCK_GRANTED |
                            LDLM_FL_BLOCK_CONV | LDLM_FL_BLOCK_WAIT);
                goto out;
        }

        ldlm_resource_unlink_lock(lock);
        if (res->lr_type == LDLM_EXTENT && lock->l_tree_node == NULL) {
                if (node == NULL) {
                        ldlm_lock_destroy_nolock(lock);
                        rc = -ENOMEM;
                        goto out;
                }

                INIT_LIST_HEAD(&node->li_group);
                ldlm_interval_attach(node, lock);
                node = NULL;
        }

        /* Some flags from the enqueue want to make it into the AST, via the
         * lock's l_flags. */
        lock->l_flags |= *flags & LDLM_FL_AST_DISCARD_DATA;

        /* This distinction between local lock trees is very important; a client
         * namespace only has information about locks taken by that client, and
         * thus doesn't have enough information to decide for itself if it can
         * be granted (below).  In this case, we do exactly what the server
         * tells us to do, as dictated by the 'flags'.
         *
         * We do exactly the same thing during recovery, when the server is
         * more or less trusting the clients not to lie.
         *
         * FIXME (bug 268): Detect obvious lies by checking compatibility in
         * granted/converting queues. */
        if (local) {
                if (*flags & LDLM_FL_BLOCK_CONV)
                        ldlm_resource_add_lock(res, &res->lr_converting, lock);
                else if (*flags & (LDLM_FL_BLOCK_WAIT | LDLM_FL_BLOCK_GRANTED))
                        ldlm_resource_add_lock(res, &res->lr_waiting, lock);
                else
                        ldlm_grant_lock(lock, NULL);
                goto out;
        } else {
                CERROR("This is client-side-only module, cannot handle LDLM_NAMESPACE_SERVER resource type lock.\n");
                LBUG();
        }

out:
        unlock_res_and_lock(lock);
        if (node)
                OBD_SLAB_FREE(node, ldlm_interval_slab, sizeof(*node));
        return rc;
}


/**
 * Process a call to blocking AST callback for a lock in ast_work list
 */
static int
ldlm_work_bl_ast_lock(struct ptlrpc_request_set *rqset, void *opaq)
{
        struct ldlm_cb_set_arg *arg = opaq;
        struct ldlm_lock_desc   d;
        int                  rc;
        struct ldlm_lock       *lock;

        if (list_empty(arg->list))
                return -ENOENT;

        lock = list_entry(arg->list->next, struct ldlm_lock, l_bl_ast);

        /* nobody should touch l_bl_ast */
        lock_res_and_lock(lock);
        list_del_init(&lock->l_bl_ast);

        LASSERT(lock->l_flags & LDLM_FL_AST_SENT);
        LASSERT(lock->l_bl_ast_run == 0);
        LASSERT(lock->l_blocking_lock);
        lock->l_bl_ast_run++;
        unlock_res_and_lock(lock);

        ldlm_lock2desc(lock->l_blocking_lock, &d);

        rc = lock->l_blocking_ast(lock, &d, (void *)arg, LDLM_CB_BLOCKING);
        LDLM_LOCK_RELEASE(lock->l_blocking_lock);
        lock->l_blocking_lock = NULL;
        LDLM_LOCK_RELEASE(lock);

        return rc;
}

/**
 * Process a call to completion AST callback for a lock in ast_work list
 */
static int
ldlm_work_cp_ast_lock(struct ptlrpc_request_set *rqset, void *opaq)
{
        struct ldlm_cb_set_arg  *arg = opaq;
        int                   rc = 0;
        struct ldlm_lock        *lock;
        ldlm_completion_callback completion_callback;

        if (list_empty(arg->list))
                return -ENOENT;

        lock = list_entry(arg->list->next, struct ldlm_lock, l_cp_ast);

        /* It's possible to receive a completion AST before we've set
         * the l_completion_ast pointer: either because the AST arrived
         * before the reply, or simply because there's a small race
         * window between receiving the reply and finishing the local
         * enqueue. (bug 842)
         *
         * This can't happen with the blocking_ast, however, because we
         * will never call the local blocking_ast until we drop our
         * reader/writer reference, which we won't do until we get the
         * reply and finish enqueueing. */

        /* nobody should touch l_cp_ast */
        lock_res_and_lock(lock);
        list_del_init(&lock->l_cp_ast);
        LASSERT(lock->l_flags & LDLM_FL_CP_REQD);
        /* save l_completion_ast since it can be changed by
         * mds_intent_policy(), see bug 14225 */
        completion_callback = lock->l_completion_ast;
        lock->l_flags &= ~LDLM_FL_CP_REQD;
        unlock_res_and_lock(lock);

        if (completion_callback != NULL)
                rc = completion_callback(lock, 0, (void *)arg);
        LDLM_LOCK_RELEASE(lock);

        return rc;
}

/**
 * Process a call to revocation AST callback for a lock in ast_work list
 */
static int
ldlm_work_revoke_ast_lock(struct ptlrpc_request_set *rqset, void *opaq)
{
        struct ldlm_cb_set_arg *arg = opaq;
        struct ldlm_lock_desc   desc;
        int                  rc;
        struct ldlm_lock       *lock;

        if (list_empty(arg->list))
                return -ENOENT;

        lock = list_entry(arg->list->next, struct ldlm_lock, l_rk_ast);
        list_del_init(&lock->l_rk_ast);

        /* the desc just pretend to exclusive */
        ldlm_lock2desc(lock, &desc);
        desc.l_req_mode = LCK_EX;
        desc.l_granted_mode = 0;

        rc = lock->l_blocking_ast(lock, &desc, (void *)arg, LDLM_CB_BLOCKING);
        LDLM_LOCK_RELEASE(lock);

        return rc;
}

/**
 * Process a call to glimpse AST callback for a lock in ast_work list
 */
int ldlm_work_gl_ast_lock(struct ptlrpc_request_set *rqset, void *opaq)
{
        struct ldlm_cb_set_arg          *arg = opaq;
        struct ldlm_glimpse_work        *gl_work;
        struct ldlm_lock                *lock;
        int                              rc = 0;

        if (list_empty(arg->list))
                return -ENOENT;

        gl_work = list_entry(arg->list->next, struct ldlm_glimpse_work,
                                 gl_list);
        list_del_init(&gl_work->gl_list);

        lock = gl_work->gl_lock;

        /* transfer the glimpse descriptor to ldlm_cb_set_arg */
        arg->gl_desc = gl_work->gl_desc;

        /* invoke the actual glimpse callback */
        if (lock->l_glimpse_ast(lock, (void *)arg) == 0)
                rc = 1;

        LDLM_LOCK_RELEASE(lock);

        if ((gl_work->gl_flags & LDLM_GL_WORK_NOFREE) == 0)
                kfree(gl_work);

        return rc;
}

/**
 * Process list of locks in need of ASTs being sent.
 *
 * Used on server to send multiple ASTs together instead of sending one by
 * one.
 */
int ldlm_run_ast_work(struct ldlm_namespace *ns, struct list_head *rpc_list,
                      enum ldlm_desc_ast_t ast_type)
{
        struct ldlm_cb_set_arg *arg;
        set_producer_func       work_ast_lock;
        int                  rc;

        if (list_empty(rpc_list))
                return 0;

        arg = kzalloc(sizeof(*arg), GFP_NOFS);
        if (arg == NULL)
                return -ENOMEM;

        atomic_set(&arg->restart, 0);
        arg->list = rpc_list;

        switch (ast_type) {
        case LDLM_WORK_BL_AST:
                arg->type = LDLM_BL_CALLBACK;
                work_ast_lock = ldlm_work_bl_ast_lock;
                break;
        case LDLM_WORK_CP_AST:
                arg->type = LDLM_CP_CALLBACK;
                work_ast_lock = ldlm_work_cp_ast_lock;
                break;
        case LDLM_WORK_REVOKE_AST:
                arg->type = LDLM_BL_CALLBACK;
                work_ast_lock = ldlm_work_revoke_ast_lock;
                break;
        case LDLM_WORK_GL_AST:
                arg->type = LDLM_GL_CALLBACK;
                work_ast_lock = ldlm_work_gl_ast_lock;
                break;
        default:
                LBUG();
        }

        /* We create a ptlrpc request set with flow control extension.
         * This request set will use the work_ast_lock function to produce new
         * requests and will send a new request each time one completes in order
         * to keep the number of requests in flight to ns_max_parallel_ast */
        arg->set = ptlrpc_prep_fcset(ns->ns_max_parallel_ast ? : UINT_MAX,
                                     work_ast_lock, arg);
        if (arg->set == NULL) {
                rc = -ENOMEM;
                goto out;
        }

        ptlrpc_set_wait(arg->set);
        ptlrpc_set_destroy(arg->set);

        rc = atomic_read(&arg->restart) ? -ERESTART : 0;
        goto out;
out:
        kfree(arg);
        return rc;
}

static int reprocess_one_queue(struct ldlm_resource *res, void *closure)
{
        ldlm_reprocess_all(res);
        return LDLM_ITER_CONTINUE;
}

static int ldlm_reprocess_res(struct cfs_hash *hs, struct cfs_hash_bd *bd,
                              struct hlist_node *hnode, void *arg)
{
        struct ldlm_resource *res = cfs_hash_object(hs, hnode);
        int    rc;

        rc = reprocess_one_queue(res, arg);

        return rc == LDLM_ITER_STOP;
}

/**
 * Iterate through all resources on a namespace attempting to grant waiting
 * locks.
 */
void ldlm_reprocess_all_ns(struct ldlm_namespace *ns)
{
        if (ns != NULL) {
                cfs_hash_for_each_nolock(ns->ns_rs_hash,
                                         ldlm_reprocess_res, NULL);
        }
}
EXPORT_SYMBOL(ldlm_reprocess_all_ns);

/**
 * Try to grant all waiting locks on a resource.
 *
 * Calls ldlm_reprocess_queue on converting and waiting queues.
 *
 * Typically called after some resource locks are cancelled to see
 * if anything could be granted as a result of the cancellation.
 */
void ldlm_reprocess_all(struct ldlm_resource *res)
{
        LIST_HEAD(rpc_list);

        if (!ns_is_client(ldlm_res_to_ns(res))) {
                CERROR("This is client-side-only module, cannot handle LDLM_NAMESPACE_SERVER resource type lock.\n");
                LBUG();
        }
}

/**
 * Helper function to call blocking AST for LDLM lock \a lock in a
 * "cancelling" mode.
 */
void ldlm_cancel_callback(struct ldlm_lock *lock)
{
        check_res_locked(lock->l_resource);
        if (!(lock->l_flags & LDLM_FL_CANCEL)) {
                lock->l_flags |= LDLM_FL_CANCEL;
                if (lock->l_blocking_ast) {
                        unlock_res_and_lock(lock);
                        lock->l_blocking_ast(lock, NULL, lock->l_ast_data,
                                             LDLM_CB_CANCELING);
                        lock_res_and_lock(lock);
                } else {
                        LDLM_DEBUG(lock, "no blocking ast");
                }
        }
        lock->l_flags |= LDLM_FL_BL_DONE;
}

/**
 * Remove skiplist-enabled LDLM lock \a req from granted list
 */
void ldlm_unlink_lock_skiplist(struct ldlm_lock *req)
{
        if (req->l_resource->lr_type != LDLM_PLAIN &&
            req->l_resource->lr_type != LDLM_IBITS)
                return;

        list_del_init(&req->l_sl_policy);
        list_del_init(&req->l_sl_mode);
}

/**
 * Attempts to cancel LDLM lock \a lock that has no reader/writer references.
 */
void ldlm_lock_cancel(struct ldlm_lock *lock)
{
        struct ldlm_resource *res;
        struct ldlm_namespace *ns;

        lock_res_and_lock(lock);

        res = lock->l_resource;
        ns  = ldlm_res_to_ns(res);

        /* Please do not, no matter how tempting, remove this LBUG without
         * talking to me first. -phik */
        if (lock->l_readers || lock->l_writers) {
                LDLM_ERROR(lock, "lock still has references");
                LBUG();
        }

        if (lock->l_flags & LDLM_FL_WAITED)
                ldlm_del_waiting_lock(lock);

        /* Releases cancel callback. */
        ldlm_cancel_callback(lock);

        /* Yes, second time, just in case it was added again while we were
         * running with no res lock in ldlm_cancel_callback */
        if (lock->l_flags & LDLM_FL_WAITED)
                ldlm_del_waiting_lock(lock);

        ldlm_resource_unlink_lock(lock);
        ldlm_lock_destroy_nolock(lock);

        if (lock->l_granted_mode == lock->l_req_mode)
                ldlm_pool_del(&ns->ns_pool, lock);

        /* Make sure we will not be called again for same lock what is possible
         * if not to zero out lock->l_granted_mode */
        lock->l_granted_mode = LCK_MINMODE;
        unlock_res_and_lock(lock);
}
EXPORT_SYMBOL(ldlm_lock_cancel);

/**
 * Set opaque data into the lock that only makes sense to upper layer.
 */
int ldlm_lock_set_data(struct lustre_handle *lockh, void *data)
{
        struct ldlm_lock *lock = ldlm_handle2lock(lockh);
        int rc = -EINVAL;

        if (lock) {
                if (lock->l_ast_data == NULL)
                        lock->l_ast_data = data;
                if (lock->l_ast_data == data)
                        rc = 0;
                LDLM_LOCK_PUT(lock);
        }
        return rc;
}
EXPORT_SYMBOL(ldlm_lock_set_data);

struct export_cl_data {
        struct obd_export       *ecl_exp;
        int                     ecl_loop;
};

/**
 * Iterator function for ldlm_cancel_locks_for_export.
 * Cancels passed locks.
 */
int ldlm_cancel_locks_for_export_cb(struct cfs_hash *hs, struct cfs_hash_bd *bd,
                                    struct hlist_node *hnode, void *data)

{
        struct export_cl_data   *ecl = (struct export_cl_data *)data;
        struct obd_export       *exp  = ecl->ecl_exp;
        struct ldlm_lock     *lock = cfs_hash_object(hs, hnode);
        struct ldlm_resource *res;

        res = ldlm_resource_getref(lock->l_resource);
        LDLM_LOCK_GET(lock);

        LDLM_DEBUG(lock, "export %p", exp);
        ldlm_res_lvbo_update(res, NULL, 1);
        ldlm_lock_cancel(lock);
        ldlm_reprocess_all(res);
        ldlm_resource_putref(res);
        LDLM_LOCK_RELEASE(lock);

        ecl->ecl_loop++;
        if ((ecl->ecl_loop & -ecl->ecl_loop) == ecl->ecl_loop) {
                CDEBUG(D_INFO,
                       "Cancel lock %p for export %p (loop %d), still have %d locks left on hash table.\n",
                       lock, exp, ecl->ecl_loop,
                       atomic_read(&hs->hs_count));
        }

        return 0;
}

/**
 * Cancel all locks for given export.
 *
 * Typically called on client disconnection/eviction
 */
void ldlm_cancel_locks_for_export(struct obd_export *exp)
{
        struct export_cl_data   ecl = {
                .ecl_exp        = exp,
                .ecl_loop       = 0,
        };

        cfs_hash_for_each_empty(exp->exp_lock_hash,
                                ldlm_cancel_locks_for_export_cb, &ecl);
}

/**
 * Downgrade an exclusive lock.
 *
 * A fast variant of ldlm_lock_convert for conversion of exclusive
 * locks. The conversion is always successful.
 * Used by Commit on Sharing (COS) code.
 *
 * \param lock A lock to convert
 * \param new_mode new lock mode
 */
void ldlm_lock_downgrade(struct ldlm_lock *lock, int new_mode)
{
        LASSERT(lock->l_granted_mode & (LCK_PW | LCK_EX));
        LASSERT(new_mode == LCK_COS);

        lock_res_and_lock(lock);
        ldlm_resource_unlink_lock(lock);
        /*
         * Remove the lock from pool as it will be added again in
         * ldlm_grant_lock() called below.
         */
        ldlm_pool_del(&ldlm_lock_to_ns(lock)->ns_pool, lock);

        lock->l_req_mode = new_mode;
        ldlm_grant_lock(lock, NULL);
        unlock_res_and_lock(lock);
        ldlm_reprocess_all(lock->l_resource);
}
EXPORT_SYMBOL(ldlm_lock_downgrade);

/**
 * Attempt to convert already granted lock to a different mode.
 *
 * While lock conversion is not currently used, future client-side
 * optimizations could take advantage of it to avoid discarding cached
 * pages on a file.
 */
struct ldlm_resource *ldlm_lock_convert(struct ldlm_lock *lock, int new_mode,
                                        __u32 *flags)
{
        LIST_HEAD(rpc_list);
        struct ldlm_resource *res;
        struct ldlm_namespace *ns;
        int granted = 0;
        struct ldlm_interval *node;

        /* Just return if mode is unchanged. */
        if (new_mode == lock->l_granted_mode) {
                *flags |= LDLM_FL_BLOCK_GRANTED;
                return lock->l_resource;
        }

        /* I can't check the type of lock here because the bitlock of lock
         * is not held here, so do the allocation blindly. -jay */
        OBD_SLAB_ALLOC_PTR_GFP(node, ldlm_interval_slab, GFP_NOFS);
        if (node == NULL)
                /* Actually, this causes EDEADLOCK to be returned */
                return NULL;

        LASSERTF((new_mode == LCK_PW && lock->l_granted_mode == LCK_PR),
                 "new_mode %u, granted %u\n", new_mode, lock->l_granted_mode);

        lock_res_and_lock(lock);

        res = lock->l_resource;
        ns  = ldlm_res_to_ns(res);

        lock->l_req_mode = new_mode;
        if (res->lr_type == LDLM_PLAIN || res->lr_type == LDLM_IBITS) {
                ldlm_resource_unlink_lock(lock);
        } else {
                ldlm_resource_unlink_lock(lock);
                if (res->lr_type == LDLM_EXTENT) {
                        /* FIXME: ugly code, I have to attach the lock to a
                         * interval node again since perhaps it will be granted
                         * soon */
                        INIT_LIST_HEAD(&node->li_group);
                        ldlm_interval_attach(node, lock);
                        node = NULL;
                }
        }

        /*
         * Remove old lock from the pool before adding the lock with new
         * mode below in ->policy()
         */
        ldlm_pool_del(&ns->ns_pool, lock);

        /* If this is a local resource, put it on the appropriate list. */
        if (ns_is_client(ldlm_res_to_ns(res))) {
                if (*flags & (LDLM_FL_BLOCK_CONV | LDLM_FL_BLOCK_GRANTED)) {
                        ldlm_resource_add_lock(res, &res->lr_converting, lock);
                } else {
                        /* This should never happen, because of the way the
                         * server handles conversions. */
                        LDLM_ERROR(lock, "Erroneous flags %x on local lock\n",
                                   *flags);
                        LBUG();

                        ldlm_grant_lock(lock, &rpc_list);
                        granted = 1;
                        /* FIXME: completion handling not with lr_lock held ! */
                        if (lock->l_completion_ast)
                                lock->l_completion_ast(lock, 0, NULL);
                }
        } else {
                CERROR("This is client-side-only module, cannot handle LDLM_NAMESPACE_SERVER resource type lock.\n");
                LBUG();
        }
        unlock_res_and_lock(lock);

        if (granted)
                ldlm_run_ast_work(ns, &rpc_list, LDLM_WORK_CP_AST);
        if (node)
                OBD_SLAB_FREE(node, ldlm_interval_slab, sizeof(*node));
        return res;
}
EXPORT_SYMBOL(ldlm_lock_convert);

/**
 * Print lock with lock handle \a lockh description into debug log.
 *
 * Used when printing all locks on a resource for debug purposes.
 */
void ldlm_lock_dump_handle(int level, struct lustre_handle *lockh)
{
        struct ldlm_lock *lock;

        if (!((libcfs_debug | D_ERROR) & level))
                return;

        lock = ldlm_handle2lock(lockh);
        if (lock == NULL)
                return;

        LDLM_DEBUG_LIMIT(level, lock, "###");

        LDLM_LOCK_PUT(lock);
}
EXPORT_SYMBOL(ldlm_lock_dump_handle);

/**
 * Print lock information with custom message into debug log.
 * Helper function.
 */
void _ldlm_lock_debug(struct ldlm_lock *lock,
                      struct libcfs_debug_msg_data *msgdata,
                      const char *fmt, ...)
{
        va_list args;
        struct obd_export *exp = lock->l_export;
        struct ldlm_resource *resource = lock->l_resource;
        char *nid = "local";

        va_start(args, fmt);

        if (exp && exp->exp_connection) {
                nid = libcfs_nid2str(exp->exp_connection->c_peer.nid);
        } else if (exp && exp->exp_obd != NULL) {
                struct obd_import *imp = exp->exp_obd->u.cli.cl_import;

                nid = libcfs_nid2str(imp->imp_connection->c_peer.nid);
        }

        if (resource == NULL) {
                libcfs_debug_vmsg2(msgdata, fmt, args,
                                   " ns: \?\? lock: %p/%#llx lrc: %d/%d,%d mode: %s/%s res: \?\? rrc=\?\? type: \?\?\? flags: %#llx nid: %s remote: %#llx expref: %d pid: %u timeout: %lu lvb_type: %d\n",
                                   lock,
                                   lock->l_handle.h_cookie, atomic_read(&lock->l_refc),
                                   lock->l_readers, lock->l_writers,
                                   ldlm_lockname[lock->l_granted_mode],
                                   ldlm_lockname[lock->l_req_mode],
                                   lock->l_flags, nid, lock->l_remote_handle.cookie,
                                   exp ? atomic_read(&exp->exp_refcount) : -99,
                                   lock->l_pid, lock->l_callback_timeout, lock->l_lvb_type);
                va_end(args);
                return;
        }

        switch (resource->lr_type) {
        case LDLM_EXTENT:
                libcfs_debug_vmsg2(msgdata, fmt, args,
                                   " ns: %s lock: %p/%#llx lrc: %d/%d,%d mode: %s/%s res: " DLDLMRES " rrc: %d type: %s [%llu->%llu] (req %llu->%llu) flags: %#llx nid: %s remote: %#llx expref: %d pid: %u timeout: %lu lvb_type: %d\n",
                                   ldlm_lock_to_ns_name(lock), lock,
                                   lock->l_handle.h_cookie, atomic_read(&lock->l_refc),
                                   lock->l_readers, lock->l_writers,
                                   ldlm_lockname[lock->l_granted_mode],
                                   ldlm_lockname[lock->l_req_mode],
                                   PLDLMRES(resource),
                                   atomic_read(&resource->lr_refcount),
                                   ldlm_typename[resource->lr_type],
                                   lock->l_policy_data.l_extent.start,
                                   lock->l_policy_data.l_extent.end,
                                   lock->l_req_extent.start, lock->l_req_extent.end,
                                   lock->l_flags, nid, lock->l_remote_handle.cookie,
                                   exp ? atomic_read(&exp->exp_refcount) : -99,
                                   lock->l_pid, lock->l_callback_timeout,
                                   lock->l_lvb_type);
                break;

        case LDLM_FLOCK:
                libcfs_debug_vmsg2(msgdata, fmt, args,
                                   " ns: %s lock: %p/%#llx lrc: %d/%d,%d mode: %s/%s res: " DLDLMRES " rrc: %d type: %s pid: %d [%llu->%llu] flags: %#llx nid: %s remote: %#llx expref: %d pid: %u timeout: %lu\n",
                                   ldlm_lock_to_ns_name(lock), lock,
                                   lock->l_handle.h_cookie, atomic_read(&lock->l_refc),
                                   lock->l_readers, lock->l_writers,
                                   ldlm_lockname[lock->l_granted_mode],
                                   ldlm_lockname[lock->l_req_mode],
                                   PLDLMRES(resource),
                                   atomic_read(&resource->lr_refcount),
                                   ldlm_typename[resource->lr_type],
                                   lock->l_policy_data.l_flock.pid,
                                   lock->l_policy_data.l_flock.start,
                                   lock->l_policy_data.l_flock.end,
                                   lock->l_flags, nid, lock->l_remote_handle.cookie,
                                   exp ? atomic_read(&exp->exp_refcount) : -99,
                                   lock->l_pid, lock->l_callback_timeout);
                break;

        case LDLM_IBITS:
                libcfs_debug_vmsg2(msgdata, fmt, args,
                                   " ns: %s lock: %p/%#llx lrc: %d/%d,%d mode: %s/%s res: " DLDLMRES " bits %#llx rrc: %d type: %s flags: %#llx nid: %s remote: %#llx expref: %d pid: %u timeout: %lu lvb_type: %d\n",
                                   ldlm_lock_to_ns_name(lock),
                                   lock, lock->l_handle.h_cookie,
                                   atomic_read(&lock->l_refc),
                                   lock->l_readers, lock->l_writers,
                                   ldlm_lockname[lock->l_granted_mode],
                                   ldlm_lockname[lock->l_req_mode],
                                   PLDLMRES(resource),
                                   lock->l_policy_data.l_inodebits.bits,
                                   atomic_read(&resource->lr_refcount),
                                   ldlm_typename[resource->lr_type],
                                   lock->l_flags, nid, lock->l_remote_handle.cookie,
                                   exp ? atomic_read(&exp->exp_refcount) : -99,
                                   lock->l_pid, lock->l_callback_timeout,
                                   lock->l_lvb_type);
                break;

        default:
                libcfs_debug_vmsg2(msgdata, fmt, args,
                                   " ns: %s lock: %p/%#llx lrc: %d/%d,%d mode: %s/%s res: " DLDLMRES " rrc: %d type: %s flags: %#llx nid: %s remote: %#llx expref: %d pid: %u timeout: %lu lvb_type: %d\n",
                                   ldlm_lock_to_ns_name(lock),
                                   lock, lock->l_handle.h_cookie,
                                   atomic_read(&lock->l_refc),
                                   lock->l_readers, lock->l_writers,
                                   ldlm_lockname[lock->l_granted_mode],
                                   ldlm_lockname[lock->l_req_mode],
                                   PLDLMRES(resource),
                                   atomic_read(&resource->lr_refcount),
                                   ldlm_typename[resource->lr_type],
                                   lock->l_flags, nid, lock->l_remote_handle.cookie,
                                   exp ? atomic_read(&exp->exp_refcount) : -99,
                                   lock->l_pid, lock->l_callback_timeout,
                                   lock->l_lvb_type);
                break;
        }
        va_end(args);
}
EXPORT_SYMBOL(_ldlm_lock_debug);