[mirror_ubuntu-bionic-kernel.git] / fs / fscache / cache.c

/* FS-Cache cache handling
 *
 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#define FSCACHE_DEBUG_LEVEL CACHE
#include <linux/module.h>
#include <linux/slab.h>
#include "internal.h"

LIST_HEAD(fscache_cache_list);
DECLARE_RWSEM(fscache_addremove_sem);
DECLARE_WAIT_QUEUE_HEAD(fscache_cache_cleared_wq);
EXPORT_SYMBOL(fscache_cache_cleared_wq);

static LIST_HEAD(fscache_cache_tag_list);

/*
 * look up a cache tag
 */
struct fscache_cache_tag *__fscache_lookup_cache_tag(const char *name)
{
	struct fscache_cache_tag *tag, *xtag;

	/* firstly check for the existence of the tag under read lock */
	down_read(&fscache_addremove_sem);

	list_for_each_entry(tag, &fscache_cache_tag_list, link) {
		if (strcmp(tag->name, name) == 0) {
			atomic_inc(&tag->usage);
			up_read(&fscache_addremove_sem);
			return tag;
		}
	}

	up_read(&fscache_addremove_sem);

	/* the tag does not exist - create a candidate */
	xtag = kzalloc(sizeof(*xtag) + strlen(name) + 1, GFP_KERNEL);
	if (!xtag)
		/* return a dummy tag if out of memory */
		return ERR_PTR(-ENOMEM);

	atomic_set(&xtag->usage, 1);
	strcpy(xtag->name, name);

	/* write lock, search again and add if still not present */
	down_write(&fscache_addremove_sem);

	list_for_each_entry(tag, &fscache_cache_tag_list, link) {
		if (strcmp(tag->name, name) == 0) {
			atomic_inc(&tag->usage);
			up_write(&fscache_addremove_sem);
			kfree(xtag);
			return tag;
		}
	}

	list_add_tail(&xtag->link, &fscache_cache_tag_list);
	up_write(&fscache_addremove_sem);
	return xtag;
}

/*
 * release a reference to a cache tag
 */
void __fscache_release_cache_tag(struct fscache_cache_tag *tag)
{
	if (tag != ERR_PTR(-ENOMEM)) {
		down_write(&fscache_addremove_sem);

		if (atomic_dec_and_test(&tag->usage))
			list_del_init(&tag->link);
		else
			tag = NULL;

		up_write(&fscache_addremove_sem);

		kfree(tag);
	}
}

/*
 * select a cache in which to store an object
 * - the cache addremove semaphore must be at least read-locked by the caller
 * - the object will never be an index
 */
struct fscache_cache *fscache_select_cache_for_object(
	struct fscache_cookie *cookie)
{
	struct fscache_cache_tag *tag;
	struct fscache_object *object;
	struct fscache_cache *cache;

	_enter("");

	if (list_empty(&fscache_cache_list)) {
		_leave(" = NULL [no cache]");
		return NULL;
	}

	/* we check the parent to determine the cache to use */
	spin_lock(&cookie->lock);

	/* the first in the parent's backing list should be the preferred
	 * cache */
	if (!hlist_empty(&cookie->backing_objects)) {
		object = hlist_entry(cookie->backing_objects.first,
				     struct fscache_object, cookie_link);

		cache = object->cache;
		if (fscache_object_is_dying(object) ||
		    test_bit(FSCACHE_IOERROR, &cache->flags))
			cache = NULL;

		spin_unlock(&cookie->lock);
		_leave(" = %p [parent]", cache);
		return cache;
	}

	/* the parent is unbacked */
	if (cookie->def->type != FSCACHE_COOKIE_TYPE_INDEX) {
		/* cookie not an index and is unbacked */
		spin_unlock(&cookie->lock);
		_leave(" = NULL [cookie ub,ni]");
		return NULL;
	}

	spin_unlock(&cookie->lock);

	if (!cookie->def->select_cache)
		goto no_preference;

	/* ask the netfs for its preference */
	tag = cookie->def->select_cache(cookie->parent->netfs_data,
					cookie->netfs_data);
	if (!tag)
		goto no_preference;

	if (tag == ERR_PTR(-ENOMEM)) {
		_leave(" = NULL [nomem tag]");
		return NULL;
	}

	if (!tag->cache) {
		_leave(" = NULL [unbacked tag]");
		return NULL;
	}

	if (test_bit(FSCACHE_IOERROR, &tag->cache->flags))
		return NULL;

	_leave(" = %p [specific]", tag->cache);
	return tag->cache;

no_preference:
	/* netfs has no preference - just select first cache */
	cache = list_entry(fscache_cache_list.next,
			   struct fscache_cache, link);
	_leave(" = %p [first]", cache);
	return cache;
}

/**
 * fscache_init_cache - Initialise a cache record
 * @cache: The cache record to be initialised
 * @ops: The cache operations to be installed in that record
 * @idfmt: Format string to define identifier
 * @...: sprintf-style arguments
 *
 * Initialise a record of a cache and fill in the name.
 *
 * See Documentation/filesystems/caching/backend-api.txt for a complete
 * description.
 */
void fscache_init_cache(struct fscache_cache *cache,
			const struct fscache_cache_ops *ops,
			const char *idfmt,
			...)
{
	va_list va;

	memset(cache, 0, sizeof(*cache));

	cache->ops = ops;

	va_start(va, idfmt);
	vsnprintf(cache->identifier, sizeof(cache->identifier), idfmt, va);
	va_end(va);

	INIT_WORK(&cache->op_gc, fscache_operation_gc);
	INIT_LIST_HEAD(&cache->link);
	INIT_LIST_HEAD(&cache->object_list);
	INIT_LIST_HEAD(&cache->op_gc_list);
	spin_lock_init(&cache->object_list_lock);
	spin_lock_init(&cache->op_gc_list_lock);
}
EXPORT_SYMBOL(fscache_init_cache);

/**
 * fscache_add_cache - Declare a cache as being open for business
 * @cache: The record describing the cache
 * @ifsdef: The record of the cache object describing the top-level index
 * @tagname: The tag describing this cache
 *
 * Add a cache to the system, making it available for netfs's to use.
 *
 * See Documentation/filesystems/caching/backend-api.txt for a complete
 * description.
 */
int fscache_add_cache(struct fscache_cache *cache,
		      struct fscache_object *ifsdef,
		      const char *tagname)
{
	struct fscache_cache_tag *tag;

	BUG_ON(!cache->ops);
	BUG_ON(!ifsdef);

	cache->flags = 0;
	ifsdef->event_mask =
		((1 << NR_FSCACHE_OBJECT_EVENTS) - 1) &
		~(1 << FSCACHE_OBJECT_EV_CLEARED);
	__set_bit(FSCACHE_OBJECT_IS_AVAILABLE, &ifsdef->flags);

	if (!tagname)
		tagname = cache->identifier;

	BUG_ON(!tagname[0]);

	_enter("{%s.%s},,%s", cache->ops->name, cache->identifier, tagname);

	/* we use the cache tag to uniquely identify caches */
	tag = __fscache_lookup_cache_tag(tagname);
	if (IS_ERR(tag))
		goto nomem;

	if (test_and_set_bit(FSCACHE_TAG_RESERVED, &tag->flags))
		goto tag_in_use;

	cache->kobj = kobject_create_and_add(tagname, fscache_root);
	if (!cache->kobj)
		goto error;

	ifsdef->cookie = &fscache_fsdef_index;
	ifsdef->cache = cache;
	cache->fsdef = ifsdef;

	down_write(&fscache_addremove_sem);

	tag->cache = cache;
	cache->tag = tag;

	/* add the cache to the list */
	list_add(&cache->link, &fscache_cache_list);

	/* add the cache's netfs definition index object to the cache's
	 * list */
	spin_lock(&cache->object_list_lock);
	list_add_tail(&ifsdef->cache_link, &cache->object_list);
	spin_unlock(&cache->object_list_lock);
	fscache_objlist_add(ifsdef);

	/* add the cache's netfs definition index object to the top level index
	 * cookie as a known backing object */
	spin_lock(&fscache_fsdef_index.lock);

	hlist_add_head(&ifsdef->cookie_link,
		       &fscache_fsdef_index.backing_objects);

	atomic_inc(&fscache_fsdef_index.usage);

	/* done */
	spin_unlock(&fscache_fsdef_index.lock);
	up_write(&fscache_addremove_sem);

	pr_notice("Cache \"%s\" added (type %s)\n",
		  cache->tag->name, cache->ops->name);
	kobject_uevent(cache->kobj, KOBJ_ADD);

	_leave(" = 0 [%s]", cache->identifier);
	return 0;

tag_in_use:
	pr_err("Cache tag '%s' already in use\n", tagname);
	__fscache_release_cache_tag(tag);
	_leave(" = -EXIST");
	return -EEXIST;

error:
	__fscache_release_cache_tag(tag);
	_leave(" = -EINVAL");
	return -EINVAL;

nomem:
	_leave(" = -ENOMEM");
	return -ENOMEM;
}
EXPORT_SYMBOL(fscache_add_cache);

/**
 * fscache_io_error - Note a cache I/O error
 * @cache: The record describing the cache
 *
 * Note that an I/O error occurred in a cache and that it should no longer be
 * used for anything.  This also reports the error into the kernel log.
 *
 * See Documentation/filesystems/caching/backend-api.txt for a complete
 * description.
 */
void fscache_io_error(struct fscache_cache *cache)
{
	if (!test_and_set_bit(FSCACHE_IOERROR, &cache->flags))
		pr_err("Cache '%s' stopped due to I/O error\n",
		       cache->ops->name);
}
EXPORT_SYMBOL(fscache_io_error);

/*
 * request withdrawal of all the objects in a cache
 * - all the objects being withdrawn are moved onto the supplied list
 */
static void fscache_withdraw_all_objects(struct fscache_cache *cache,
					 struct list_head *dying_objects)
{
	struct fscache_object *object;

	while (!list_empty(&cache->object_list)) {
		spin_lock(&cache->object_list_lock);

		if (!list_empty(&cache->object_list)) {
			object = list_entry(cache->object_list.next,
					    struct fscache_object, cache_link);
			list_move_tail(&object->cache_link, dying_objects);

			_debug("withdraw %p", object->cookie);

			/* This must be done under object_list_lock to prevent
			 * a race with fscache_drop_object().
			 */
			fscache_raise_event(object, FSCACHE_OBJECT_EV_KILL);
		}

		spin_unlock(&cache->object_list_lock);
		cond_resched();
	}
}

/**
 * fscache_withdraw_cache - Withdraw a cache from the active service
 * @cache: The record describing the cache
 *
 * Withdraw a cache from service, unbinding all its cache objects from the
 * netfs cookies they're currently representing.
 *
 * See Documentation/filesystems/caching/backend-api.txt for a complete
 * description.
 */
void fscache_withdraw_cache(struct fscache_cache *cache)
{
	LIST_HEAD(dying_objects);

	_enter("");

	pr_notice("Withdrawing cache \"%s\"\n",
		  cache->tag->name);

	/* make the cache unavailable for cookie acquisition */
	if (test_and_set_bit(FSCACHE_CACHE_WITHDRAWN, &cache->flags))
		BUG();

	down_write(&fscache_addremove_sem);
	list_del_init(&cache->link);
	cache->tag->cache = NULL;
	up_write(&fscache_addremove_sem);

	/* make sure all pages pinned by operations on behalf of the netfs are
	 * written to disk */
	fscache_stat(&fscache_n_cop_sync_cache);
	cache->ops->sync_cache(cache);
	fscache_stat_d(&fscache_n_cop_sync_cache);

	/* dissociate all the netfs pages backed by this cache from the block
	 * mappings in the cache */
	fscache_stat(&fscache_n_cop_dissociate_pages);
	cache->ops->dissociate_pages(cache);
	fscache_stat_d(&fscache_n_cop_dissociate_pages);

	/* we now have to destroy all the active objects pertaining to this
	 * cache - which we do by passing them off to thread pool to be
	 * disposed of */
	_debug("destroy");

	fscache_withdraw_all_objects(cache, &dying_objects);

	/* wait for all extant objects to finish their outstanding operations
	 * and go away */
	_debug("wait for finish");
	wait_event(fscache_cache_cleared_wq,
		   atomic_read(&cache->object_count) == 0);
	_debug("wait for clearance");
	wait_event(fscache_cache_cleared_wq,
		   list_empty(&cache->object_list));
	_debug("cleared");
	ASSERT(list_empty(&dying_objects));

	kobject_put(cache->kobj);

	clear_bit(FSCACHE_TAG_RESERVED, &cache->tag->flags);
	fscache_release_cache_tag(cache->tag);
	cache->tag = NULL;

	_leave("");
}
EXPORT_SYMBOL(fscache_withdraw_cache);
Commit	Line	Data
0e04d4ce DH	1	/* FS-Cache cache handling
	2	*
	3	* Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
	4	* Written by David Howells (dhowells@redhat.com)
	5	*
	6	* This program is free software; you can redistribute it and/or
	7	* modify it under the terms of the GNU General Public License
	8	* as published by the Free Software Foundation; either version
	9	* 2 of the License, or (at your option) any later version.
	10	*/
	11
	12	#define FSCACHE_DEBUG_LEVEL CACHE
	13	#include <linux/module.h>
	14	#include <linux/slab.h>
	15	#include "internal.h"
	16
	17	LIST_HEAD(fscache_cache_list);
	18	DECLARE_RWSEM(fscache_addremove_sem);
4c515dd4 DH	19	DECLARE_WAIT_QUEUE_HEAD(fscache_cache_cleared_wq);
4c515dd4 DH	20	EXPORT_SYMBOL(fscache_cache_cleared_wq);
0e04d4ce DH	21
	22	static LIST_HEAD(fscache_cache_tag_list);
	23
	24	/*
	25	* look up a cache tag
	26	*/
	27	struct fscache_cache_tag __fscache_lookup_cache_tag(const char name)
	28	{
	29	struct fscache_cache_tag tag, xtag;
	30
	31	/* firstly check for the existence of the tag under read lock */
	32	down_read(&fscache_addremove_sem);
	33
	34	list_for_each_entry(tag, &fscache_cache_tag_list, link) {
	35	if (strcmp(tag->name, name) == 0) {
	36	atomic_inc(&tag->usage);
	37	up_read(&fscache_addremove_sem);
	38	return tag;
	39	}
	40	}
	41
	42	up_read(&fscache_addremove_sem);
	43
	44	/* the tag does not exist - create a candidate */
	45	xtag = kzalloc(sizeof(*xtag) + strlen(name) + 1, GFP_KERNEL);
	46	if (!xtag)
	47	/* return a dummy tag if out of memory */
	48	return ERR_PTR(-ENOMEM);
	49
	50	atomic_set(&xtag->usage, 1);
	51	strcpy(xtag->name, name);
	52
	53	/* write lock, search again and add if still not present */
	54	down_write(&fscache_addremove_sem);
	55
	56	list_for_each_entry(tag, &fscache_cache_tag_list, link) {
	57	if (strcmp(tag->name, name) == 0) {
	58	atomic_inc(&tag->usage);
	59	up_write(&fscache_addremove_sem);
	60	kfree(xtag);
	61	return tag;
	62	}
	63	}
	64
	65	list_add_tail(&xtag->link, &fscache_cache_tag_list);
	66	up_write(&fscache_addremove_sem);
	67	return xtag;
	68	}
	69
	70	/*
	71	* release a reference to a cache tag
	72	*/
	73	void __fscache_release_cache_tag(struct fscache_cache_tag *tag)
	74	{
	75	if (tag != ERR_PTR(-ENOMEM)) {
	76	down_write(&fscache_addremove_sem);
	77
	78	if (atomic_dec_and_test(&tag->usage))
	79	list_del_init(&tag->link);
	80	else
	81	tag = NULL;
	82
	83	up_write(&fscache_addremove_sem);
	84
85	kfree(tag);
86	}
87	}
88
89	/*
90	* select a cache in which to store an object
91	* - the cache addremove semaphore must be at least read-locked by the caller
92	* - the object will never be an index
93	*/
94	struct fscache_cache *fscache_select_cache_for_object(
95	struct fscache_cookie *cookie)
96	{
97	struct fscache_cache_tag *tag;
98	struct fscache_object *object;
99	struct fscache_cache *cache;
100
101	_enter("");
102
103	if (list_empty(&fscache_cache_list)) {
104	_leave(" = NULL [no cache]");
105	return NULL;
106	}
107
108	/* we check the parent to determine the cache to use */
109	spin_lock(&cookie->lock);
110
111	/* the first in the parent's backing list should be the preferred
112	* cache */
113	if (!hlist_empty(&cookie->backing_objects)) {
114	object = hlist_entry(cookie->backing_objects.first,
115	struct fscache_object, cookie_link);
116
117	cache = object->cache;
493f7bc1	118	if (fscache_object_is_dying(object) \|\|
0e04d4ce DH	119	test_bit(FSCACHE_IOERROR, &cache->flags))
	120	cache = NULL;
	121
	122	spin_unlock(&cookie->lock);
	123	_leave(" = %p [parent]", cache);
	124	return cache;
	125	}
	126
	127	/* the parent is unbacked */
	128	if (cookie->def->type != FSCACHE_COOKIE_TYPE_INDEX) {
	129	/* cookie not an index and is unbacked */
	130	spin_unlock(&cookie->lock);
	131	_leave(" = NULL [cookie ub,ni]");
	132	return NULL;
	133	}
	134
	135	spin_unlock(&cookie->lock);
	136
	137	if (!cookie->def->select_cache)
	138	goto no_preference;
	139
	140	/* ask the netfs for its preference */
	141	tag = cookie->def->select_cache(cookie->parent->netfs_data,
	142	cookie->netfs_data);
	143	if (!tag)
	144	goto no_preference;
	145
	146	if (tag == ERR_PTR(-ENOMEM)) {
	147	_leave(" = NULL [nomem tag]");
	148	return NULL;
	149	}
	150
	151	if (!tag->cache) {
	152	_leave(" = NULL [unbacked tag]");
	153	return NULL;
	154	}
	155
	156	if (test_bit(FSCACHE_IOERROR, &tag->cache->flags))
	157	return NULL;
	158
	159	_leave(" = %p [specific]", tag->cache);
	160	return tag->cache;
	161
	162	no_preference:
	163	/* netfs has no preference - just select first cache */
	164	cache = list_entry(fscache_cache_list.next,
	165	struct fscache_cache, link);
	166	_leave(" = %p [first]", cache);
	167	return cache;
	168	}
4c515dd4 DH	169
	170	/**
	171	* fscache_init_cache - Initialise a cache record
	172	* @cache: The cache record to be initialised
	173	* @ops: The cache operations to be installed in that record
	174	* @idfmt: Format string to define identifier
	175	* @...: sprintf-style arguments
	176	*
	177	* Initialise a record of a cache and fill in the name.
	178	*
	179	* See Documentation/filesystems/caching/backend-api.txt for a complete
	180	* description.
	181	*/
	182	void fscache_init_cache(struct fscache_cache *cache,
	183	const struct fscache_cache_ops *ops,
	184	const char *idfmt,
	185	...)
	186	{
	187	va_list va;
	188
	189	memset(cache, 0, sizeof(*cache));
	190
	191	cache->ops = ops;
	192
	193	va_start(va, idfmt);
	194	vsnprintf(cache->identifier, sizeof(cache->identifier), idfmt, va);
	195	va_end(va);
	196
952efe7b	197	INIT_WORK(&cache->op_gc, fscache_operation_gc);
4c515dd4 DH	198	INIT_LIST_HEAD(&cache->link);
	199	INIT_LIST_HEAD(&cache->object_list);
	200	INIT_LIST_HEAD(&cache->op_gc_list);
	201	spin_lock_init(&cache->object_list_lock);
	202	spin_lock_init(&cache->op_gc_list_lock);
	203	}
	204	EXPORT_SYMBOL(fscache_init_cache);
	205
	206	/**
	207	* fscache_add_cache - Declare a cache as being open for business
	208	* @cache: The record describing the cache
	209	* @ifsdef: The record of the cache object describing the top-level index
	210	* @tagname: The tag describing this cache
	211	*
	212	* Add a cache to the system, making it available for netfs's to use.
	213	*
	214	* See Documentation/filesystems/caching/backend-api.txt for a complete
	215	* description.
	216	*/
	217	int fscache_add_cache(struct fscache_cache *cache,
	218	struct fscache_object *ifsdef,
	219	const char *tagname)
	220	{
	221	struct fscache_cache_tag *tag;
	222
	223	BUG_ON(!cache->ops);
	224	BUG_ON(!ifsdef);
	225
	226	cache->flags = 0;
caaef690 DH	227	ifsdef->event_mask =
	228	((1 << NR_FSCACHE_OBJECT_EVENTS) - 1) &
	229	~(1 << FSCACHE_OBJECT_EV_CLEARED);
	230	__set_bit(FSCACHE_OBJECT_IS_AVAILABLE, &ifsdef->flags);
4c515dd4 DH	231
	232	if (!tagname)
	233	tagname = cache->identifier;
	234
	235	BUG_ON(!tagname[0]);
	236
	237	_enter("{%s.%s},,%s", cache->ops->name, cache->identifier, tagname);
	238
	239	/* we use the cache tag to uniquely identify caches */
	240	tag = __fscache_lookup_cache_tag(tagname);
	241	if (IS_ERR(tag))
	242	goto nomem;
	243
	244	if (test_and_set_bit(FSCACHE_TAG_RESERVED, &tag->flags))
	245	goto tag_in_use;
	246
	247	cache->kobj = kobject_create_and_add(tagname, fscache_root);
	248	if (!cache->kobj)
	249	goto error;
	250
	251	ifsdef->cookie = &fscache_fsdef_index;
	252	ifsdef->cache = cache;
	253	cache->fsdef = ifsdef;
	254
	255	down_write(&fscache_addremove_sem);
	256
	257	tag->cache = cache;
	258	cache->tag = tag;
	259
	260	/* add the cache to the list */
	261	list_add(&cache->link, &fscache_cache_list);
	262
	263	/* add the cache's netfs definition index object to the cache's
	264	* list */
	265	spin_lock(&cache->object_list_lock);
	266	list_add_tail(&ifsdef->cache_link, &cache->object_list);
	267	spin_unlock(&cache->object_list_lock);
4fbf4291	268	fscache_objlist_add(ifsdef);
4c515dd4 DH	269
	270	/* add the cache's netfs definition index object to the top level index
	271	* cookie as a known backing object */
	272	spin_lock(&fscache_fsdef_index.lock);
	273
	274	hlist_add_head(&ifsdef->cookie_link,
	275	&fscache_fsdef_index.backing_objects);
	276
	277	atomic_inc(&fscache_fsdef_index.usage);
	278
	279	/* done */
	280	spin_unlock(&fscache_fsdef_index.lock);
	281	up_write(&fscache_addremove_sem);
	282
36dfd116 FF	283	pr_notice("Cache \"%s\" added (type %s)\n",
36dfd116 FF	284	cache->tag->name, cache->ops->name);
4c515dd4 DH	285	kobject_uevent(cache->kobj, KOBJ_ADD);
	286
	287	_leave(" = 0 [%s]", cache->identifier);
	288	return 0;
	289
	290	tag_in_use:
36dfd116	291	pr_err("Cache tag '%s' already in use\n", tagname);
4c515dd4 DH	292	__fscache_release_cache_tag(tag);
	293	_leave(" = -EXIST");
	294	return -EEXIST;
	295
	296	error:
	297	__fscache_release_cache_tag(tag);
	298	_leave(" = -EINVAL");
	299	return -EINVAL;
	300
	301	nomem:
	302	_leave(" = -ENOMEM");
	303	return -ENOMEM;
	304	}
	305	EXPORT_SYMBOL(fscache_add_cache);
	306
	307	/**
	308	* fscache_io_error - Note a cache I/O error
	309	* @cache: The record describing the cache
	310	*
	311	* Note that an I/O error occurred in a cache and that it should no longer be
	312	* used for anything. This also reports the error into the kernel log.
	313	*
	314	* See Documentation/filesystems/caching/backend-api.txt for a complete
	315	* description.
	316	*/
	317	void fscache_io_error(struct fscache_cache *cache)
	318	{
75bc4113	319	if (!test_and_set_bit(FSCACHE_IOERROR, &cache->flags))
36dfd116	320	pr_err("Cache '%s' stopped due to I/O error\n",
75bc4113	321	cache->ops->name);
4c515dd4 DH	322	}
	323	EXPORT_SYMBOL(fscache_io_error);
	324
	325	/*
	326	* request withdrawal of all the objects in a cache
	327	* - all the objects being withdrawn are moved onto the supplied list
	328	*/
	329	static void fscache_withdraw_all_objects(struct fscache_cache *cache,
	330	struct list_head *dying_objects)
	331	{
	332	struct fscache_object *object;
	333
4c515dd4	334	while (!list_empty(&cache->object_list)) {
caaef690	335	spin_lock(&cache->object_list_lock);
4c515dd4	336
caaef690 DH	337	if (!list_empty(&cache->object_list)) {
	338	object = list_entry(cache->object_list.next,
	339	struct fscache_object, cache_link);
	340	list_move_tail(&object->cache_link, dying_objects);
4c515dd4	341
caaef690 DH	342	_debug("withdraw %p", object->cookie);
	343
	344	/* This must be done under object_list_lock to prevent
	345	* a race with fscache_drop_object().
	346	*/
	347	fscache_raise_event(object, FSCACHE_OBJECT_EV_KILL);
	348	}
4c515dd4	349
caaef690	350	spin_unlock(&cache->object_list_lock);
4c515dd4	351	cond_resched();
4c515dd4	352	}
4c515dd4 DH	353	}
	354
	355	/**
	356	* fscache_withdraw_cache - Withdraw a cache from the active service
	357	* @cache: The record describing the cache
	358	*
	359	* Withdraw a cache from service, unbinding all its cache objects from the
	360	* netfs cookies they're currently representing.
	361	*
	362	* See Documentation/filesystems/caching/backend-api.txt for a complete
	363	* description.
	364	*/
	365	void fscache_withdraw_cache(struct fscache_cache *cache)
	366	{
	367	LIST_HEAD(dying_objects);
	368
	369	_enter("");
	370
36dfd116 FF	371	pr_notice("Withdrawing cache \"%s\"\n",
36dfd116 FF	372	cache->tag->name);
4c515dd4 DH	373
	374	/* make the cache unavailable for cookie acquisition */
	375	if (test_and_set_bit(FSCACHE_CACHE_WITHDRAWN, &cache->flags))
	376	BUG();
	377
	378	down_write(&fscache_addremove_sem);
	379	list_del_init(&cache->link);
	380	cache->tag->cache = NULL;
	381	up_write(&fscache_addremove_sem);
	382
	383	/* make sure all pages pinned by operations on behalf of the netfs are
	384	* written to disk */
52bd75fd	385	fscache_stat(&fscache_n_cop_sync_cache);
4c515dd4	386	cache->ops->sync_cache(cache);
52bd75fd	387	fscache_stat_d(&fscache_n_cop_sync_cache);
4c515dd4 DH	388
	389	/* dissociate all the netfs pages backed by this cache from the block
	390	* mappings in the cache */
52bd75fd	391	fscache_stat(&fscache_n_cop_dissociate_pages);
4c515dd4	392	cache->ops->dissociate_pages(cache);
52bd75fd	393	fscache_stat_d(&fscache_n_cop_dissociate_pages);
4c515dd4 DH	394
	395	/* we now have to destroy all the active objects pertaining to this
	396	* cache - which we do by passing them off to thread pool to be
	397	* disposed of */
	398	_debug("destroy");
	399
	400	fscache_withdraw_all_objects(cache, &dying_objects);
	401
	402	/* wait for all extant objects to finish their outstanding operations
	403	* and go away */
	404	_debug("wait for finish");
	405	wait_event(fscache_cache_cleared_wq,
	406	atomic_read(&cache->object_count) == 0);
	407	_debug("wait for clearance");
	408	wait_event(fscache_cache_cleared_wq,
	409	list_empty(&cache->object_list));
	410	_debug("cleared");
	411	ASSERT(list_empty(&dying_objects));
	412
	413	kobject_put(cache->kobj);
	414
	415	clear_bit(FSCACHE_TAG_RESERVED, &cache->tag->flags);
	416	fscache_release_cache_tag(cache->tag);
	417	cache->tag = NULL;
	418
	419	_leave("");
	420	}
	421	EXPORT_SYMBOL(fscache_withdraw_cache);