--- /dev/null
+/* 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);
Code Review / kvmfornfv.git / blobdiff