linux/fs/fscache/cache.c

422 lines
11 KiB
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->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);