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.gnu.org/licenses/gpl-2.0.html
 *
 * GPL HEADER END
 */
/*
 * Copyright (c) 2002, 2010, Oracle and/or its affiliates. All rights reserved.
 * Use is subject to license terms.
 *
 * Copyright (c) 2010, 2017, 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 <libcfs/libcfs.h>

#include <lustre_swab.h>
#include <obd_class.h>

#include "ldlm_internal.h"

struct kmem_cache *ldlm_glimpse_work_kmem;
EXPORT_SYMBOL(ldlm_glimpse_work_kmem);

/* 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",
};

static ldlm_policy_wire_to_local_t ldlm_policy_wire_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_wire_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(enum ldlm_type type,
				 const union ldlm_policy_data *lpolicy,
				 union ldlm_wire_policy_data *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, enum ldlm_type type,
				  const union ldlm_wire_policy_data *wpolicy,
				  union ldlm_policy_data *lpolicy)
{
	ldlm_policy_wire_to_local_t convert;

	convert = ldlm_policy_wire_to_local[type - LDLM_MIN_TYPE];

	convert(wpolicy, lpolicy);
}

const char *ldlm_it2str(enum ldlm_intent_flags 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_GETXATTR:
		return "getxattr";
	case IT_LAYOUT:
		return "layout";
	default:
		CERROR("Unknown intent 0x%08x\n", it);
		return "UNKNOWN";
	}
}
EXPORT_SYMBOL(ldlm_it2str);

#ifdef HAVE_SERVER_SUPPORT
static ldlm_processing_policy ldlm_processing_policy_table[] = {
	[LDLM_PLAIN]	= ldlm_process_plain_lock,
	[LDLM_EXTENT]	= ldlm_process_extent_lock,
	[LDLM_FLOCK]	= ldlm_process_flock_lock,
	[LDLM_IBITS]	= ldlm_process_inodebits_lock,
};

ldlm_processing_policy ldlm_get_processing_policy(struct ldlm_resource *res)
{
        return ldlm_processing_policy_table[res->lr_type];
}
EXPORT_SYMBOL(ldlm_get_processing_policy);

static ldlm_reprocessing_policy ldlm_reprocessing_policy_table[] = {
	[LDLM_PLAIN]	= ldlm_reprocess_queue,
	[LDLM_EXTENT]	= ldlm_reprocess_queue,
	[LDLM_FLOCK]	= ldlm_reprocess_queue,
	[LDLM_IBITS]	= ldlm_reprocess_inodebits_queue,
};

ldlm_reprocessing_policy ldlm_get_reprocessing_policy(struct ldlm_resource *res)
{
	return ldlm_reprocessing_policy_table[res->lr_type];
}

#endif /* HAVE_SERVER_SUPPORT */

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)
{
	refcount_inc(&lock->l_handle.h_ref);
        return lock;
}
EXPORT_SYMBOL(ldlm_lock_get);

static void lock_handle_free(struct rcu_head *rcu)
{
	struct ldlm_lock *lock = container_of(rcu, struct ldlm_lock,
					      l_handle.h_rcu);

	OBD_FREE_PRE(lock, sizeof(*lock), "slab-freed");
	kmem_cache_free(ldlm_lock_slab, lock);
}

/**
 * Release lock reference.
 *
 * Also frees the lock if it was last reference.
 */
void ldlm_lock_put(struct ldlm_lock *lock)
{
        ENTRY;

        LASSERT(lock->l_resource != LP_POISON);
	LASSERT(refcount_read(&lock->l_handle.h_ref) > 0);
	if (refcount_dec_and_test(&lock->l_handle.h_ref)) {
                struct ldlm_resource *res;

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

                res = lock->l_resource;
		LASSERT(ldlm_is_destroyed(lock));
		LASSERT(list_empty(&lock->l_exp_list));
		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);
                if (lock->l_export) {
                        class_export_lock_put(lock->l_export, lock);
                        lock->l_export = NULL;
                }

                if (lock->l_lvb_data != NULL)
                        OBD_FREE_LARGE(lock->l_lvb_data, lock->l_lvb_len);

		if (res->lr_type == LDLM_EXTENT) {
			ldlm_interval_free(ldlm_interval_detach(lock));
		} else if (res->lr_type == LDLM_IBITS) {
			if (lock->l_ibits_node != NULL)
				OBD_SLAB_FREE_PTR(lock->l_ibits_node,
						  ldlm_inodebits_slab);
		}
		ldlm_resource_putref(res);
		lock->l_resource = NULL;
                lu_ref_fini(&lock->l_reference);
		call_rcu(&lock->l_handle.h_rcu, lock_handle_free);
        }

        EXIT;
}
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);
		if (ns->ns_last_pos == &lock->l_lru)
			ns->ns_last_pos = lock->l_lru.prev;
		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.
 *
 * If \a last_use is non-zero, it will remove the lock from LRU only if
 * it matches lock's l_last_used.
 *
 * \retval 0 if \a last_use is set, the lock is not in LRU list or \a last_use
 *           doesn't match lock's l_last_used;
 *           otherwise, the lock hasn't been in the LRU list.
 * \retval 1 the lock was in LRU list and removed.
 */
int ldlm_lock_remove_from_lru_check(struct ldlm_lock *lock, ktime_t last_use)
{
	struct ldlm_namespace *ns = ldlm_lock_to_ns(lock);
	int rc = 0;

	ENTRY;
	if (ldlm_is_ns_srv(lock)) {
		LASSERT(list_empty(&lock->l_lru));
		RETURN(0);
	}

	spin_lock(&ns->ns_lock);
	if (!ktime_compare(last_use, ktime_set(0, 0)) ||
	    !ktime_compare(last_use, lock->l_last_used))
		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 = ktime_get();
	LASSERT(list_empty(&lock->l_lru));
	LASSERT(lock->l_resource->lr_type != LDLM_FLOCK);
	list_add_tail(&lock->l_lru, &ns->ns_unused_list);
	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);

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

/**
 * 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);

	ENTRY;
	if (ldlm_is_ns_srv(lock)) {
		LASSERT(list_empty(&lock->l_lru));
		EXIT;
		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);
	EXIT;
}

/**
 * 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
 */
static int ldlm_lock_destroy_internal(struct ldlm_lock *lock)
{
        ENTRY;

        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 (ldlm_is_destroyed(lock)) {
		LASSERT(list_empty(&lock->l_lru));
		EXIT;
		return 0;
	}
	ldlm_set_destroyed(lock);

	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);

        EXIT;
        return 1;
}

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

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

static const char lock_handle_owner[] = "ldlm";

/**
 *
 * 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;
	ENTRY;

	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);

	refcount_set(&lock->l_handle.h_ref, 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_HLIST_NODE(&lock->l_handle.h_link);
	class_handle_hash(&lock->l_handle, lock_handle_owner);

        lu_ref_init(&lock->l_reference);
        lu_ref_add(&lock->l_reference, "hash", lock);
	lock->l_callback_timestamp = 0;
	lock->l_activity = 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;
        struct ldlm_resource *newres;
        int type;
        ENTRY;

        LASSERT(ns_is_client(ns));

	oldres = lock_res_and_lock(lock);
	if (memcmp(new_resid, &oldres->lr_name,
		   sizeof(oldres->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 (IS_ERR(newres))
		RETURN(PTR_ERR(newres));

        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);
}

/** \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;
	ENTRY;

	LASSERT(handle);

	if (!lustre_handle_is_used(handle))
		RETURN(NULL);

	lock = class_handle2object(handle->cookie, lock_handle_owner);
	if (lock == NULL)
		RETURN(NULL);

	if (lock->l_export != NULL && lock->l_export->exp_failed) {
		CDEBUG(D_INFO, "lock export failed: lock %p, exp %p\n",
		       lock, lock->l_export);
		LDLM_LOCK_PUT(lock);
		RETURN(NULL);
	}

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

	lock_res_and_lock(lock);

	LASSERT(lock->l_resource != NULL);

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

	/* If we're setting flags, make sure none of them are already set. */
	if (flags != 0) {
		if ((lock->l_flags & flags) != 0) {
			unlock_res_and_lock(lock);
			LDLM_LOCK_PUT(lock);
			RETURN(NULL);
		}

		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);
}

/**
 * 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.
 */
static void ldlm_add_bl_work_item(struct ldlm_lock *lock, struct ldlm_lock *new,
				  struct list_head *work_list)
{
	if (!ldlm_is_ast_sent(lock)) {
		LDLM_DEBUG(lock, "lock incompatible; sending blocking AST.");
		ldlm_set_ast_sent(lock);
		/* If the enqueuing client said so, tell the AST recipient to
		 * discard dirty data, rather than writing back. */
		if (ldlm_is_ast_discard_data(new))
			ldlm_set_discard_data(lock);

		/* Lock can be converted from a blocking state back to granted
		 * after lock convert or COS downgrade but still be in an
		 * older bl_list because it is controlled only by
		 * ldlm_work_bl_ast_lock(), let it be processed there.
		 */
		if (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.
 */
static void ldlm_add_cp_work_item(struct ldlm_lock *lock,
				  struct list_head *work_list)
{
	if (!ldlm_is_cp_reqd(lock)) {
		ldlm_set_cp_reqd(lock);
                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)
{
        ENTRY;
        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);
        EXIT;
}

/**
 * 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(const struct lustre_handle *lockh, enum ldlm_mode mode)
{
	struct ldlm_lock *lock;

	lock = ldlm_handle2lock(lockh);
	LASSERTF(lock != NULL, "Non-existing lock: %#llx\n", lockh->cookie);
	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,
				      enum ldlm_mode 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(const struct lustre_handle *lockh, enum ldlm_mode 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 ||
		    !ldlm_is_cbpending(lock)) {
                        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, enum ldlm_mode 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 accomodate flock locks
 * that cannot be placed in LRU.
 */
void ldlm_lock_decref_internal_nolock(struct ldlm_lock *lock,
				      enum ldlm_mode 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, enum ldlm_mode mode)
{
	struct ldlm_namespace *ns;

	ENTRY;

	lock_res_and_lock(lock);

	ns = ldlm_lock_to_ns(lock);

	ldlm_lock_decref_internal_nolock(lock, mode);

	if ((ldlm_is_local(lock) || lock->l_req_mode == LCK_GROUP) &&
	    !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.
		 *
		 * Group locks are special:
		 * They must not go in LRU, but they are not called back
		 * like non-group locks, instead they are manually released.
		 * They have an l_writers reference which they keep until
		 * they are manually released, so we remove them when they have
		 * no more reader or writer references. - LU-6368 */
		ldlm_set_cbpending(lock);
	}

	if (!lock->l_readers && !lock->l_writers && ldlm_is_cbpending(lock)) {
		unsigned int mask = D_DLMTRACE;

		/* If we received a blocked AST and this was the last reference,
		 * run the callback. */
		if (ldlm_is_ns_srv(lock) && lock->l_export)
			mask |= D_WARNING;
		LDLM_DEBUG_LIMIT(mask, lock,
				 "final decref done on %sCBPENDING lock",
				 mask & D_WARNING ? "non-local " : "");

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

		if (ldlm_is_fail_loc(lock))
			OBD_RACE(OBD_FAIL_LDLM_CP_BL_RACE);

		if (ldlm_is_atomic_cb(lock) ||
                    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 &&
		   !ldlm_is_no_lru(lock) &&
		   !ldlm_is_bl_ast(lock) &&
		   !ldlm_is_converting(lock)) {