1 files changed, 444 insertions, 0 deletions

diff --git a/fs/fscache/cookie.c b/fs/fscache/cookie.c
index 47fd75b832e1..72fd18f6c71f 100644
--- a/fs/fscache/cookie.c
+++ b/fs/fscache/cookie.c
@@ -7,6 +7,9 @@
  * 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.
+ *
+ * See Documentation/filesystems/caching/netfs-api.txt for more information on
+ * the netfs API.
  */
 
 #define FSCACHE_DEBUG_LEVEL COOKIE
@@ -16,6 +19,14 @@
 
 struct kmem_cache *fscache_cookie_jar;
 
+static atomic_t fscache_object_debug_id = ATOMIC_INIT(0);
+
+static int fscache_acquire_non_index_cookie(struct fscache_cookie *cookie);
+static int fscache_alloc_object(struct fscache_cache *cache,
+                                struct fscache_cookie *cookie);
+static int fscache_attach_object(struct fscache_cookie *cookie,
+                                 struct fscache_object *object);
+
 /*
  * initialise an cookie jar slab element prior to any use
  */
@@ -29,6 +40,439 @@ void fscache_cookie_init_once(void *_cookie)
 }
 
 /*
+ * request a cookie to represent an object (index, datafile, xattr, etc)
+ * - parent specifies the parent object
+ *   - the top level index cookie for each netfs is stored in the fscache_netfs
+ *     struct upon registration
+ * - def points to the definition
+ * - the netfs_data will be passed to the functions pointed to in *def
+ * - all attached caches will be searched to see if they contain this object
+ * - index objects aren't stored on disk until there's a dependent file that
+ *   needs storing
+ * - other objects are stored in a selected cache immediately, and all the
+ *   indices forming the path to it are instantiated if necessary
+ * - we never let on to the netfs about errors
+ *   - we may set a negative cookie pointer, but that's okay
+ */
+struct fscache_cookie *__fscache_acquire_cookie(
+        struct fscache_cookie *parent,
+        const struct fscache_cookie_def *def,
+        void *netfs_data)
+{
+        struct fscache_cookie *cookie;
+
+        BUG_ON(!def);
+
+        _enter("{%s},{%s},%p",
+               parent ? (char *) parent->def->name : "<no-parent>",
+               def->name, netfs_data);
+
+        fscache_stat(&fscache_n_acquires);
+
+        /* if there's no parent cookie, then we don't create one here either */
+        if (!parent) {
+                fscache_stat(&fscache_n_acquires_null);
+                _leave(" [no parent]");
+                return NULL;
+        }
+
+        /* validate the definition */
+        BUG_ON(!def->get_key);
+        BUG_ON(!def->name[0]);
+
+        BUG_ON(def->type == FSCACHE_COOKIE_TYPE_INDEX &&
+               parent->def->type != FSCACHE_COOKIE_TYPE_INDEX);
+
+        /* allocate and initialise a cookie */
+        cookie = kmem_cache_alloc(fscache_cookie_jar, GFP_KERNEL);
+        if (!cookie) {
+                fscache_stat(&fscache_n_acquires_oom);
+                _leave(" [ENOMEM]");
+                return NULL;
+        }
+
+        atomic_set(&cookie->usage, 1);
+        atomic_set(&cookie->n_children, 0);
+
+        atomic_inc(&parent->usage);
+        atomic_inc(&parent->n_children);
+
+        cookie->def             = def;
+        cookie->parent          = parent;
+        cookie->netfs_data      = netfs_data;
+        cookie->flags           = 0;
+
+        INIT_RADIX_TREE(&cookie->stores, GFP_NOFS);
+
+        switch (cookie->def->type) {
+        case FSCACHE_COOKIE_TYPE_INDEX:
+                fscache_stat(&fscache_n_cookie_index);
+                break;
+        case FSCACHE_COOKIE_TYPE_DATAFILE:
+                fscache_stat(&fscache_n_cookie_data);
+                break;
+        default:
+                fscache_stat(&fscache_n_cookie_special);
+                break;
+        }
+
+        /* if the object is an index then we need do nothing more here - we
+         * create indices on disk when we need them as an index may exist in
+         * multiple caches */
+        if (cookie->def->type != FSCACHE_COOKIE_TYPE_INDEX) {
+                if (fscache_acquire_non_index_cookie(cookie) < 0) {
+                        atomic_dec(&parent->n_children);
+                        __fscache_cookie_put(cookie);
+                        fscache_stat(&fscache_n_acquires_nobufs);
+                        _leave(" = NULL");
+                        return NULL;
+                }
+        }
+
+        fscache_stat(&fscache_n_acquires_ok);
+        _leave(" = %p", cookie);
+        return cookie;
+}
+EXPORT_SYMBOL(__fscache_acquire_cookie);
+
+/*
+ * acquire a non-index cookie
+ * - this must make sure the index chain is instantiated and instantiate the
+ *   object representation too
+ */
+static int fscache_acquire_non_index_cookie(struct fscache_cookie *cookie)
+{
+        struct fscache_object *object;
+        struct fscache_cache *cache;
+        uint64_t i_size;
+        int ret;
+
+        _enter("");
+
+        cookie->flags = 1 << FSCACHE_COOKIE_UNAVAILABLE;
+
+        /* now we need to see whether the backing objects for this cookie yet
+         * exist, if not there'll be nothing to search */
+        down_read(&fscache_addremove_sem);
+
+        if (list_empty(&fscache_cache_list)) {
+                up_read(&fscache_addremove_sem);
+                _leave(" = 0 [no caches]");
+                return 0;
+        }
+
+        /* select a cache in which to store the object */
+        cache = fscache_select_cache_for_object(cookie->parent);
+        if (!cache) {
+                up_read(&fscache_addremove_sem);
+                fscache_stat(&fscache_n_acquires_no_cache);
+                _leave(" = -ENOMEDIUM [no cache]");
+                return -ENOMEDIUM;
+        }
+
+        _debug("cache %s", cache->tag->name);
+
+        cookie->flags =
+                (1 << FSCACHE_COOKIE_LOOKING_UP) |
+                (1 << FSCACHE_COOKIE_CREATING) |
+                (1 << FSCACHE_COOKIE_NO_DATA_YET);
+
+        /* ask the cache to allocate objects for this cookie and its parent
+         * chain */
+        ret = fscache_alloc_object(cache, cookie);
+        if (ret < 0) {
+                up_read(&fscache_addremove_sem);
+                _leave(" = %d", ret);
+                return ret;
+        }
+
+        /* pass on how big the object we're caching is supposed to be */
+        cookie->def->get_attr(cookie->netfs_data, &i_size);
+
+        spin_lock(&cookie->lock);
+        if (hlist_empty(&cookie->backing_objects)) {
+                spin_unlock(&cookie->lock);
+                goto unavailable;
+        }
+
+        object = hlist_entry(cookie->backing_objects.first,
+                             struct fscache_object, cookie_link);
+
+        fscache_set_store_limit(object, i_size);
+
+        /* initiate the process of looking up all the objects in the chain
+         * (done by fscache_initialise_object()) */
+        fscache_enqueue_object(object);
+
+        spin_unlock(&cookie->lock);
+
+        /* we may be required to wait for lookup to complete at this point */
+        if (!fscache_defer_lookup) {
+                _debug("non-deferred lookup %p", &cookie->flags);
+                wait_on_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP,
+                            fscache_wait_bit, TASK_UNINTERRUPTIBLE);
+                _debug("complete");
+                if (test_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags))
+                        goto unavailable;
+        }
+
+        up_read(&fscache_addremove_sem);
+        _leave(" = 0 [deferred]");
+        return 0;
+
+unavailable:
+        up_read(&fscache_addremove_sem);
+        _leave(" = -ENOBUFS");
+        return -ENOBUFS;
+}
+
+/*
+ * recursively allocate cache object records for a cookie/cache combination
+ * - caller must be holding the addremove sem
+ */
+static int fscache_alloc_object(struct fscache_cache *cache,
+                                struct fscache_cookie *cookie)
+{
+        struct fscache_object *object;
+        struct hlist_node *_n;
+        int ret;
+
+        _enter("%p,%p{%s}", cache, cookie, cookie->def->name);
+
+        spin_lock(&cookie->lock);
+        hlist_for_each_entry(object, _n, &cookie->backing_objects,
+                             cookie_link) {
+                if (object->cache == cache)
+                        goto object_already_extant;
+        }
+        spin_unlock(&cookie->lock);
+
+        /* ask the cache to allocate an object (we may end up with duplicate
+         * objects at this stage, but we sort that out later) */
+        object = cache->ops->alloc_object(cache, cookie);
+        if (IS_ERR(object)) {
+                fscache_stat(&fscache_n_object_no_alloc);
+                ret = PTR_ERR(object);
+                goto error;
+        }
+
+        fscache_stat(&fscache_n_object_alloc);
+
+        object->debug_id = atomic_inc_return(&fscache_object_debug_id);
+
+        _debug("ALLOC OBJ%x: %s {%lx}",
+               object->debug_id, cookie->def->name, object->events);
+
+        ret = fscache_alloc_object(cache, cookie->parent);
+        if (ret < 0)
+                goto error_put;
+
+        /* only attach if we managed to allocate all we needed, otherwise
+         * discard the object we just allocated and instead use the one
+         * attached to the cookie */
+        if (fscache_attach_object(cookie, object) < 0)
+                cache->ops->put_object(object);
+
+        _leave(" = 0");
+        return 0;
+
+object_already_extant:
+        ret = -ENOBUFS;
+        if (object->state >= FSCACHE_OBJECT_DYING) {
+                spin_unlock(&cookie->lock);
+                goto error;
+        }
+        spin_unlock(&cookie->lock);
+        _leave(" = 0 [found]");
+        return 0;
+
+error_put:
+        cache->ops->put_object(object);
+error:
+        _leave(" = %d", ret);
+        return ret;
+}
+
+/*
+ * attach a cache object to a cookie
+ */
+static int fscache_attach_object(struct fscache_cookie *cookie,
+                                 struct fscache_object *object)
+{
+        struct fscache_object *p;
+        struct fscache_cache *cache = object->cache;
+        struct hlist_node *_n;
+        int ret;
+
+        _enter("{%s},{OBJ%x}", cookie->def->name, object->debug_id);
+
+        spin_lock(&cookie->lock);
+
+        /* there may be multiple initial creations of this object, but we only
+         * want one */
+        ret = -EEXIST;
+        hlist_for_each_entry(p, _n, &cookie->backing_objects, cookie_link) {
+                if (p->cache == object->cache) {
+                        if (p->state >= FSCACHE_OBJECT_DYING)
+                                ret = -ENOBUFS;
+                        goto cant_attach_object;
+                }
+        }
+
+        /* pin the parent object */
+        spin_lock_nested(&cookie->parent->lock, 1);
+        hlist_for_each_entry(p, _n, &cookie->parent->backing_objects,
+                             cookie_link) {
+                if (p->cache == object->cache) {
+                        if (p->state >= FSCACHE_OBJECT_DYING) {
+                                ret = -ENOBUFS;
+                                spin_unlock(&cookie->parent->lock);
+                                goto cant_attach_object;
+                        }
+                        object->parent = p;
+                        spin_lock(&p->lock);
+                        p->n_children++;
+                        spin_unlock(&p->lock);
+                        break;
+                }
+        }
+        spin_unlock(&cookie->parent->lock);
+
+        /* attach to the cache's object list */
+        if (list_empty(&object->cache_link)) {
+                spin_lock(&cache->object_list_lock);
+                list_add(&object->cache_link, &cache->object_list);
+                spin_unlock(&cache->object_list_lock);
+        }
+
+        /* attach to the cookie */
+        object->cookie = cookie;
+        atomic_inc(&cookie->usage);
+        hlist_add_head(&object->cookie_link, &cookie->backing_objects);
+        ret = 0;
+
+cant_attach_object:
+        spin_unlock(&cookie->lock);
+        _leave(" = %d", ret);
+        return ret;
+}
+
+/*
+ * update the index entries backing a cookie
+ */
+void __fscache_update_cookie(struct fscache_cookie *cookie)
+{
+        struct fscache_object *object;
+        struct hlist_node *_p;
+
+        fscache_stat(&fscache_n_updates);
+
+        if (!cookie) {
+                fscache_stat(&fscache_n_updates_null);
+                _leave(" [no cookie]");
+                return;
+        }
+
+        _enter("{%s}", cookie->def->name);
+
+        BUG_ON(!cookie->def->get_aux);
+
+        spin_lock(&cookie->lock);
+
+        /* update the index entry on disk in each cache backing this cookie */
+        hlist_for_each_entry(object, _p,
+                             &cookie->backing_objects, cookie_link) {
+                fscache_raise_event(object, FSCACHE_OBJECT_EV_UPDATE);
+        }
+
+        spin_unlock(&cookie->lock);
+        _leave("");
+}
+EXPORT_SYMBOL(__fscache_update_cookie);
+
+/*
+ * release a cookie back to the cache
+ * - the object will be marked as recyclable on disk if retire is true
+ * - all dependents of this cookie must have already been unregistered
+ *   (indices/files/pages)
+ */
+void __fscache_relinquish_cookie(struct fscache_cookie *cookie, int retire)
+{
+        struct fscache_cache *cache;
+        struct fscache_object *object;
+        unsigned long event;
+
+        fscache_stat(&fscache_n_relinquishes);
+
+        if (!cookie) {
+                fscache_stat(&fscache_n_relinquishes_null);
+                _leave(" [no cookie]");
+                return;
+        }
+
+        _enter("%p{%s,%p},%d",
+               cookie, cookie->def->name, cookie->netfs_data, retire);
+
+        if (atomic_read(&cookie->n_children) != 0) {
+                printk(KERN_ERR "FS-Cache: Cookie '%s' still has children\n",
+                       cookie->def->name);
+                BUG();
+        }
+
+        /* wait for the cookie to finish being instantiated (or to fail) */
+        if (test_bit(FSCACHE_COOKIE_CREATING, &cookie->flags)) {
+                fscache_stat(&fscache_n_relinquishes_waitcrt);
+                wait_on_bit(&cookie->flags, FSCACHE_COOKIE_CREATING,
+                            fscache_wait_bit, TASK_UNINTERRUPTIBLE);
+        }
+
+        event = retire ? FSCACHE_OBJECT_EV_RETIRE : FSCACHE_OBJECT_EV_RELEASE;
+
+        /* detach pointers back to the netfs */
+        spin_lock(&cookie->lock);
+
+        cookie->netfs_data      = NULL;
+        cookie->def             = NULL;
+
+        /* break links with all the active objects */
+        while (!hlist_empty(&cookie->backing_objects)) {
+                object = hlist_entry(cookie->backing_objects.first,
+                                     struct fscache_object,
+                                     cookie_link);
+
+                _debug("RELEASE OBJ%x", object->debug_id);
+
+                /* detach each cache object from the object cookie */
+                spin_lock(&object->lock);
+                hlist_del_init(&object->cookie_link);
+
+                cache = object->cache;
+                object->cookie = NULL;
+                fscache_raise_event(object, event);
+                spin_unlock(&object->lock);
+
+                if (atomic_dec_and_test(&cookie->usage))
+                        /* the cookie refcount shouldn't be reduced to 0 yet */
+                        BUG();
+        }
+
+        spin_unlock(&cookie->lock);
+
+        if (cookie->parent) {
+                ASSERTCMP(atomic_read(&cookie->parent->usage), >, 0);
+                ASSERTCMP(atomic_read(&cookie->parent->n_children), >, 0);
+                atomic_dec(&cookie->parent->n_children);
+        }
+
+        /* finally dispose of the cookie */
+        ASSERTCMP(atomic_read(&cookie->usage), >, 0);
+        fscache_cookie_put(cookie);
+
+        _leave("");
+}
+EXPORT_SYMBOL(__fscache_relinquish_cookie);
+
+/*
  * destroy a cookie
  */
 void __fscache_cookie_put(struct fscache_cookie *cookie)