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417 lines
11 KiB
417 lines
11 KiB
// SPDX-License-Identifier: GPL-2.0-or-later |
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/* FS-Cache cache handling |
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* |
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* Copyright (C) 2007 Red Hat, Inc. All Rights Reserved. |
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* Written by David Howells ([email protected]) |
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*/ |
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#define FSCACHE_DEBUG_LEVEL CACHE |
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#include <linux/module.h> |
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#include <linux/slab.h> |
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#include "internal.h" |
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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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/* |
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* look up a cache tag |
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*/ |
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struct fscache_cache_tag *__fscache_lookup_cache_tag(const char *name) |
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{ |
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struct fscache_cache_tag *tag, *xtag; |
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/* firstly check for the existence of the tag under read lock */ |
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down_read(&fscache_addremove_sem); |
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list_for_each_entry(tag, &fscache_cache_tag_list, link) { |
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if (strcmp(tag->name, name) == 0) { |
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atomic_inc(&tag->usage); |
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up_read(&fscache_addremove_sem); |
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return tag; |
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} |
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} |
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up_read(&fscache_addremove_sem); |
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/* the tag does not exist - create a candidate */ |
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xtag = kzalloc(sizeof(*xtag) + strlen(name) + 1, GFP_KERNEL); |
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if (!xtag) |
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/* return a dummy tag if out of memory */ |
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return ERR_PTR(-ENOMEM); |
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atomic_set(&xtag->usage, 1); |
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strcpy(xtag->name, name); |
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/* write lock, search again and add if still not present */ |
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down_write(&fscache_addremove_sem); |
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list_for_each_entry(tag, &fscache_cache_tag_list, link) { |
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if (strcmp(tag->name, name) == 0) { |
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atomic_inc(&tag->usage); |
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up_write(&fscache_addremove_sem); |
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kfree(xtag); |
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return tag; |
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} |
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} |
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list_add_tail(&xtag->link, &fscache_cache_tag_list); |
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up_write(&fscache_addremove_sem); |
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return xtag; |
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} |
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/* |
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* release a reference to a cache tag |
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*/ |
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void __fscache_release_cache_tag(struct fscache_cache_tag *tag) |
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{ |
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if (tag != ERR_PTR(-ENOMEM)) { |
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down_write(&fscache_addremove_sem); |
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if (atomic_dec_and_test(&tag->usage)) |
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list_del_init(&tag->link); |
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else |
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tag = NULL; |
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up_write(&fscache_addremove_sem); |
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kfree(tag); |
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} |
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} |
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/* |
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* select a cache in which to store an object |
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* - the cache addremove semaphore must be at least read-locked by the caller |
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* - the object will never be an index |
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*/ |
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struct fscache_cache *fscache_select_cache_for_object( |
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struct fscache_cookie *cookie) |
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{ |
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struct fscache_cache_tag *tag; |
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struct fscache_object *object; |
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struct fscache_cache *cache; |
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_enter(""); |
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if (list_empty(&fscache_cache_list)) { |
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_leave(" = NULL [no cache]"); |
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return NULL; |
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} |
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/* we check the parent to determine the cache to use */ |
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spin_lock(&cookie->lock); |
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/* the first in the parent's backing list should be the preferred |
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* cache */ |
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if (!hlist_empty(&cookie->backing_objects)) { |
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object = hlist_entry(cookie->backing_objects.first, |
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struct fscache_object, cookie_link); |
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cache = object->cache; |
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if (fscache_object_is_dying(object) || |
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test_bit(FSCACHE_IOERROR, &cache->flags)) |
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cache = NULL; |
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spin_unlock(&cookie->lock); |
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_leave(" = %p [parent]", cache); |
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return cache; |
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} |
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/* the parent is unbacked */ |
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if (cookie->type != FSCACHE_COOKIE_TYPE_INDEX) { |
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/* cookie not an index and is unbacked */ |
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spin_unlock(&cookie->lock); |
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_leave(" = NULL [cookie ub,ni]"); |
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return NULL; |
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} |
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spin_unlock(&cookie->lock); |
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if (!cookie->def->select_cache) |
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goto no_preference; |
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/* ask the netfs for its preference */ |
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tag = cookie->def->select_cache(cookie->parent->netfs_data, |
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cookie->netfs_data); |
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if (!tag) |
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goto no_preference; |
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if (tag == ERR_PTR(-ENOMEM)) { |
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_leave(" = NULL [nomem tag]"); |
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return NULL; |
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} |
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if (!tag->cache) { |
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_leave(" = NULL [unbacked tag]"); |
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return NULL; |
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} |
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if (test_bit(FSCACHE_IOERROR, &tag->cache->flags)) |
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return NULL; |
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_leave(" = %p [specific]", tag->cache); |
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return tag->cache; |
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no_preference: |
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/* netfs has no preference - just select first cache */ |
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cache = list_entry(fscache_cache_list.next, |
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struct fscache_cache, link); |
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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.rst 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, fscache_operation_gc); |
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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.rst 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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ASSERTCMP(ifsdef->cookie, ==, &fscache_fsdef_index); |
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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 = |
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((1 << NR_FSCACHE_OBJECT_EVENTS) - 1) & |
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~(1 << FSCACHE_OBJECT_EV_CLEARED); |
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__set_bit(FSCACHE_OBJECT_IS_AVAILABLE, &ifsdef->flags); |
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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->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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fscache_objlist_add(ifsdef); |
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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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pr_notice("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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pr_err("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.rst 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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if (!test_and_set_bit(FSCACHE_IOERROR, &cache->flags)) |
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pr_err("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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while (!list_empty(&cache->object_list)) { |
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spin_lock(&cache->object_list_lock); |
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if (!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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/* This must be done under object_list_lock to prevent |
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* a race with fscache_drop_object(). |
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*/ |
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fscache_raise_event(object, FSCACHE_OBJECT_EV_KILL); |
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} |
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spin_unlock(&cache->object_list_lock); |
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cond_resched(); |
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} |
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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.rst 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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pr_notice("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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fscache_stat(&fscache_n_cop_sync_cache); |
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cache->ops->sync_cache(cache); |
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fscache_stat_d(&fscache_n_cop_sync_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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fscache_stat(&fscache_n_cop_dissociate_pages); |
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cache->ops->dissociate_pages(cache); |
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fscache_stat_d(&fscache_n_cop_dissociate_pages); |
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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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