FS-Cache: Add cache management
Implement the entry points by which a cache backend may initialise, add, declare an error upon and withdraw a cache. Further, an object is created in sysfs under which each cache added will get an object created: /sys/fs/fscache/<cachetag>/ All of this is described in Documentation/filesystems/caching/backend-api.txt added by a previous patch. Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Steve Dickson <steved@redhat.com> Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Tested-by: Daire Byrne <Daire.Byrne@framestore.com>
This commit is contained in:
David Howells
parent
0e04d4cefc
commit
4c515dd47a
2 changed files with 256 additions and 0 deletions
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@ -16,6 +16,8 @@
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LIST_HEAD(fscache_cache_list);
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DECLARE_RWSEM(fscache_addremove_sem);
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DECLARE_WAIT_QUEUE_HEAD(fscache_cache_cleared_wq);
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EXPORT_SYMBOL(fscache_cache_cleared_wq);
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static LIST_HEAD(fscache_cache_tag_list);
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@ -164,3 +166,250 @@ struct fscache_cache *fscache_select_cache_for_object(
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_leave(" = %p [first]", cache);
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return cache;
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}
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/**
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* fscache_init_cache - Initialise a cache record
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* @cache: The cache record to be initialised
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* @ops: The cache operations to be installed in that record
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* @idfmt: Format string to define identifier
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* @...: sprintf-style arguments
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*
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* Initialise a record of a cache and fill in the name.
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*
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* See Documentation/filesystems/caching/backend-api.txt for a complete
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* description.
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*/
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void fscache_init_cache(struct fscache_cache *cache,
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const struct fscache_cache_ops *ops,
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const char *idfmt,
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...)
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{
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va_list va;
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memset(cache, 0, sizeof(*cache));
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cache->ops = ops;
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va_start(va, idfmt);
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vsnprintf(cache->identifier, sizeof(cache->identifier), idfmt, va);
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va_end(va);
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INIT_WORK(&cache->op_gc, NULL);
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INIT_LIST_HEAD(&cache->link);
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INIT_LIST_HEAD(&cache->object_list);
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INIT_LIST_HEAD(&cache->op_gc_list);
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spin_lock_init(&cache->object_list_lock);
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spin_lock_init(&cache->op_gc_list_lock);
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}
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EXPORT_SYMBOL(fscache_init_cache);
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/**
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* fscache_add_cache - Declare a cache as being open for business
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* @cache: The record describing the cache
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* @ifsdef: The record of the cache object describing the top-level index
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* @tagname: The tag describing this cache
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*
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* Add a cache to the system, making it available for netfs's to use.
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*
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* See Documentation/filesystems/caching/backend-api.txt for a complete
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* description.
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*/
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int fscache_add_cache(struct fscache_cache *cache,
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struct fscache_object *ifsdef,
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const char *tagname)
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{
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struct fscache_cache_tag *tag;
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BUG_ON(!cache->ops);
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BUG_ON(!ifsdef);
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cache->flags = 0;
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ifsdef->event_mask = ULONG_MAX & ~(1 << FSCACHE_OBJECT_EV_CLEARED);
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ifsdef->state = FSCACHE_OBJECT_ACTIVE;
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if (!tagname)
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tagname = cache->identifier;
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BUG_ON(!tagname[0]);
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_enter("{%s.%s},,%s", cache->ops->name, cache->identifier, tagname);
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/* we use the cache tag to uniquely identify caches */
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tag = __fscache_lookup_cache_tag(tagname);
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if (IS_ERR(tag))
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goto nomem;
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if (test_and_set_bit(FSCACHE_TAG_RESERVED, &tag->flags))
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goto tag_in_use;
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cache->kobj = kobject_create_and_add(tagname, fscache_root);
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if (!cache->kobj)
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goto error;
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ifsdef->cookie = &fscache_fsdef_index;
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ifsdef->cache = cache;
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cache->fsdef = ifsdef;
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down_write(&fscache_addremove_sem);
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tag->cache = cache;
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cache->tag = tag;
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/* add the cache to the list */
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list_add(&cache->link, &fscache_cache_list);
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/* add the cache's netfs definition index object to the cache's
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* list */
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spin_lock(&cache->object_list_lock);
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list_add_tail(&ifsdef->cache_link, &cache->object_list);
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spin_unlock(&cache->object_list_lock);
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/* add the cache's netfs definition index object to the top level index
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* cookie as a known backing object */
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spin_lock(&fscache_fsdef_index.lock);
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hlist_add_head(&ifsdef->cookie_link,
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&fscache_fsdef_index.backing_objects);
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atomic_inc(&fscache_fsdef_index.usage);
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/* done */
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spin_unlock(&fscache_fsdef_index.lock);
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up_write(&fscache_addremove_sem);
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printk(KERN_NOTICE "FS-Cache: Cache \"%s\" added (type %s)\n",
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cache->tag->name, cache->ops->name);
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kobject_uevent(cache->kobj, KOBJ_ADD);
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_leave(" = 0 [%s]", cache->identifier);
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return 0;
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tag_in_use:
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printk(KERN_ERR "FS-Cache: Cache tag '%s' already in use\n", tagname);
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__fscache_release_cache_tag(tag);
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_leave(" = -EXIST");
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return -EEXIST;
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error:
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__fscache_release_cache_tag(tag);
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_leave(" = -EINVAL");
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return -EINVAL;
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nomem:
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_leave(" = -ENOMEM");
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return -ENOMEM;
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}
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EXPORT_SYMBOL(fscache_add_cache);
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/**
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* fscache_io_error - Note a cache I/O error
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* @cache: The record describing the cache
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*
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* Note that an I/O error occurred in a cache and that it should no longer be
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* used for anything. This also reports the error into the kernel log.
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*
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* See Documentation/filesystems/caching/backend-api.txt for a complete
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* description.
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*/
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void fscache_io_error(struct fscache_cache *cache)
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{
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set_bit(FSCACHE_IOERROR, &cache->flags);
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printk(KERN_ERR "FS-Cache: Cache %s stopped due to I/O error\n",
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cache->ops->name);
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}
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EXPORT_SYMBOL(fscache_io_error);
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/*
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* request withdrawal of all the objects in a cache
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* - all the objects being withdrawn are moved onto the supplied list
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*/
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static void fscache_withdraw_all_objects(struct fscache_cache *cache,
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struct list_head *dying_objects)
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{
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struct fscache_object *object;
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spin_lock(&cache->object_list_lock);
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while (!list_empty(&cache->object_list)) {
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object = list_entry(cache->object_list.next,
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struct fscache_object, cache_link);
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list_move_tail(&object->cache_link, dying_objects);
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_debug("withdraw %p", object->cookie);
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spin_lock(&object->lock);
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spin_unlock(&cache->object_list_lock);
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fscache_raise_event(object, FSCACHE_OBJECT_EV_WITHDRAW);
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spin_unlock(&object->lock);
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cond_resched();
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spin_lock(&cache->object_list_lock);
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}
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spin_unlock(&cache->object_list_lock);
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}
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/**
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* fscache_withdraw_cache - Withdraw a cache from the active service
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* @cache: The record describing the cache
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*
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* Withdraw a cache from service, unbinding all its cache objects from the
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* netfs cookies they're currently representing.
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*
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* See Documentation/filesystems/caching/backend-api.txt for a complete
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* description.
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*/
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void fscache_withdraw_cache(struct fscache_cache *cache)
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{
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LIST_HEAD(dying_objects);
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_enter("");
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printk(KERN_NOTICE "FS-Cache: Withdrawing cache \"%s\"\n",
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cache->tag->name);
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/* make the cache unavailable for cookie acquisition */
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if (test_and_set_bit(FSCACHE_CACHE_WITHDRAWN, &cache->flags))
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BUG();
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down_write(&fscache_addremove_sem);
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list_del_init(&cache->link);
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cache->tag->cache = NULL;
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up_write(&fscache_addremove_sem);
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/* make sure all pages pinned by operations on behalf of the netfs are
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* written to disk */
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cache->ops->sync_cache(cache);
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/* dissociate all the netfs pages backed by this cache from the block
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* mappings in the cache */
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cache->ops->dissociate_pages(cache);
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/* we now have to destroy all the active objects pertaining to this
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* cache - which we do by passing them off to thread pool to be
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* disposed of */
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_debug("destroy");
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fscache_withdraw_all_objects(cache, &dying_objects);
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/* wait for all extant objects to finish their outstanding operations
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* and go away */
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_debug("wait for finish");
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wait_event(fscache_cache_cleared_wq,
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atomic_read(&cache->object_count) == 0);
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_debug("wait for clearance");
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wait_event(fscache_cache_cleared_wq,
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list_empty(&cache->object_list));
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_debug("cleared");
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ASSERT(list_empty(&dying_objects));
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kobject_put(cache->kobj);
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clear_bit(FSCACHE_TAG_RESERVED, &cache->tag->flags);
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fscache_release_cache_tag(cache->tag);
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cache->tag = NULL;
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_leave("");
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}
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EXPORT_SYMBOL(fscache_withdraw_cache);
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@ -56,9 +56,15 @@ static int __init fscache_init(void)
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if (ret < 0)
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goto error_proc;
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fscache_root = kobject_create_and_add("fscache", kernel_kobj);
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if (!fscache_root)
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goto error_kobj;
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printk(KERN_NOTICE "FS-Cache: Loaded\n");
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return 0;
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error_kobj:
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fscache_proc_cleanup();
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error_proc:
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slow_work_unregister_user();
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error_slow_work:
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@ -74,6 +80,7 @@ static void __exit fscache_exit(void)
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{
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_enter("");
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kobject_put(fscache_root);
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fscache_proc_cleanup();
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slow_work_unregister_user();
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printk(KERN_NOTICE "FS-Cache: Unloaded\n");
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