// 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 (dhowells@redhat.com)
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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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