Merge tag 'fscache-20130702' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs

Pull FS-Cache updates from David Howells:
 "This contains a number of fixes for various FS-Cache issues plus some
  cleanups.  The commits are, in order:

   1) Provide a system wait_on_atomic_t() and wake_up_atomic_t() sharing
      the bit-wait table (enhancement for #8).

   2) Don't put spin_lock() in a while-condition as spin_lock() may have
      a do {} while(0) wrapper (cleanup).

   3) Symbolically name i_mutex lock classes rather than using numbers
      in CacheFiles (cleanup).

   4) Don't sleep in page release if __GFP_FS is not set (deadlock vs
      ext4).

   5) Uninline fscache_object_init() (cleanup for #7).

   6) Wrap checks on object state (cleanup for #7).

   7) Simplify the object state machine by separating work states from
      wait states.

   8) Simplify cookie retention by objects (NULL pointer deref fix).

   9) Remove unused list_to_page() macro (cleanup).

  10) Make the remaining-pages counter in the retrieval op atomic
      (assertion failure fix).

  11) Don't use spin_is_locked() in assertions (assertion failure fix)"

* tag 'fscache-20130702' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs:
  FS-Cache: Don't use spin_is_locked() in assertions
  FS-Cache: The retrieval remaining-pages counter needs to be atomic_t
  cachefiles: remove unused macro list_to_page()
  FS-Cache: Simplify cookie retention for fscache_objects, fixing oops
  FS-Cache: Fix object state machine to have separate work and wait states
  FS-Cache: Wrap checks on object state
  FS-Cache: Uninline fscache_object_init()
  FS-Cache: Don't sleep in page release if __GFP_FS is not set
  CacheFiles: name i_mutex lock class explicitly
  fs/fscache: remove spin_lock() from the condition in while()
  Add wait_on_atomic_t() and wake_up_atomic_t()

Author: torvalds

fs/cachefiles/interface.c

@@ -13,8 +13,6 @@
 #include <linux/mount.h>
 #include "internal.h"
 
-#define list_to_page(head) (list_entry((head)->prev, struct page, lru))
-
 struct cachefiles_lookup_data {
 	struct cachefiles_xattr	*auxdata;	/* auxiliary data */
 	char			*key;		/* key path */
@@ -212,20 +210,29 @@ static void cachefiles_update_object(struct fscache_object *_object)
 	object = container_of(_object, struct cachefiles_object, fscache);
 	cache = container_of(object->fscache.cache, struct cachefiles_cache,
 			     cache);
+
+	if (!fscache_use_cookie(_object)) {
+		_leave(" [relinq]");
+		return;
+	}
+
 	cookie = object->fscache.cookie;
 
 	if (!cookie->def->get_aux) {
+		fscache_unuse_cookie(_object);
 		_leave(" [no aux]");
 		return;
 	}
 
 	auxdata = kmalloc(2 + 512 + 3, cachefiles_gfp);
 	if (!auxdata) {
+		fscache_unuse_cookie(_object);
 		_leave(" [nomem]");
 		return;
 	}
 
 	auxlen = cookie->def->get_aux(cookie->netfs_data, auxdata->data, 511);
+	fscache_unuse_cookie(_object);
 	ASSERTCMP(auxlen, <, 511);
 
 	auxdata->len = auxlen + 1;
@@ -263,7 +270,7 @@ static void cachefiles_drop_object(struct fscache_object *_object)
 #endif
 
 	/* delete retired objects */
-	if (object->fscache.state == FSCACHE_OBJECT_RECYCLING &&
+	if (test_bit(FSCACHE_COOKIE_RETIRED, &object->fscache.cookie->flags) &&
 	    _object != cache->cache.fsdef
 	    ) {
 		_debug("- retire object OBJ%x", object->fscache.debug_id);

fs/cachefiles/namei.c

@@ -38,7 +38,7 @@ void __cachefiles_printk_object(struct cachefiles_object *object,
 	printk(KERN_ERR "%sobject: OBJ%x\n",
 	       prefix, object->fscache.debug_id);
 	printk(KERN_ERR "%sobjstate=%s fl=%lx wbusy=%x ev=%lx[%lx]\n",
-	       prefix, fscache_object_states[object->fscache.state],
+	       prefix, object->fscache.state->name,
 	       object->fscache.flags, work_busy(&object->fscache.work),
 	       object->fscache.events, object->fscache.event_mask);
 	printk(KERN_ERR "%sops=%u inp=%u exc=%u\n",
@@ -127,10 +127,10 @@ static void cachefiles_mark_object_buried(struct cachefiles_cache *cache,
 found_dentry:
 	kdebug("preemptive burial: OBJ%x [%s] %p",
 	       object->fscache.debug_id,
-	       fscache_object_states[object->fscache.state],
+	       object->fscache.state->name,
 	       dentry);
 
-	if (object->fscache.state < FSCACHE_OBJECT_DYING) {
+	if (fscache_object_is_live(&object->fscache)) {
 		printk(KERN_ERR "\n");
 		printk(KERN_ERR "CacheFiles: Error:"
 		       " Can't preemptively bury live object\n");
@@ -192,7 +192,7 @@ static int cachefiles_mark_object_active(struct cachefiles_cache *cache,
 	/* an old object from a previous incarnation is hogging the slot - we
 	 * need to wait for it to be destroyed */
 wait_for_old_object:
-	if (xobject->fscache.state < FSCACHE_OBJECT_DYING) {
+	if (fscache_object_is_live(&object->fscache)) {
 		printk(KERN_ERR "\n");
 		printk(KERN_ERR "CacheFiles: Error:"
 		       " Unexpected object collision\n");
@@ -836,7 +836,7 @@ static struct dentry *cachefiles_check_active(struct cachefiles_cache *cache,
 	//       dir->d_name.len, dir->d_name.len, dir->d_name.name, filename);
 
 	/* look up the victim */
-	mutex_lock_nested(&dir->d_inode->i_mutex, 1);
+	mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_PARENT);
 
 	start = jiffies;
 	victim = lookup_one_len(filename, dir, strlen(filename));

fs/cachefiles/xattr.c

@@ -109,13 +109,12 @@ int cachefiles_set_object_xattr(struct cachefiles_object *object,
 	struct dentry *dentry = object->dentry;
 	int ret;
 
-	ASSERT(object->fscache.cookie);
 	ASSERT(dentry);
 
 	_enter("%p,#%d", object, auxdata->len);
 
 	/* attempt to install the cache metadata directly */
-	_debug("SET %s #%u", object->fscache.cookie->def->name, auxdata->len);
+	_debug("SET #%u", auxdata->len);
 
 	ret = vfs_setxattr(dentry, cachefiles_xattr_cache,
 			   &auxdata->type, auxdata->len,
@@ -138,13 +137,12 @@ int cachefiles_update_object_xattr(struct cachefiles_object *object,
 	struct dentry *dentry = object->dentry;
 	int ret;
 
-	ASSERT(object->fscache.cookie);
 	ASSERT(dentry);
 
 	_enter("%p,#%d", object, auxdata->len);
 
 	/* attempt to install the cache metadata directly */
-	_debug("SET %s #%u", object->fscache.cookie->def->name, auxdata->len);
+	_debug("SET #%u", auxdata->len);
 
 	ret = vfs_setxattr(dentry, cachefiles_xattr_cache,
 			   &auxdata->type, auxdata->len,

fs/fscache/cache.c

@@ -115,7 +115,7 @@ struct fscache_cache *fscache_select_cache_for_object(
 				     struct fscache_object, cookie_link);
 
 		cache = object->cache;
-		if (object->state >= FSCACHE_OBJECT_DYING ||
+		if (fscache_object_is_dying(object) ||
 		    test_bit(FSCACHE_IOERROR, &cache->flags))
 			cache = NULL;
 
@@ -224,8 +224,10 @@ int fscache_add_cache(struct fscache_cache *cache,
 	BUG_ON(!ifsdef);
 
 	cache->flags = 0;
-	ifsdef->event_mask = ULONG_MAX & ~(1 << FSCACHE_OBJECT_EV_CLEARED);
-	ifsdef->state = FSCACHE_OBJECT_ACTIVE;
+	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;
@@ -330,25 +332,25 @@ static void fscache_withdraw_all_objects(struct fscache_cache *cache,
 {
 	struct fscache_object *object;
 
-	spin_lock(&cache->object_list_lock);
-
 	while (!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);
+		spin_lock(&cache->object_list_lock);
 
-		_debug("withdraw %p", object->cookie);
+		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);
 
-		spin_lock(&object->lock);
-		spin_unlock(&cache->object_list_lock);
-		fscache_raise_event(object, FSCACHE_OBJECT_EV_WITHDRAW);
-		spin_unlock(&object->lock);
+			_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();
-		spin_lock(&cache->object_list_lock);
 	}
-
-	spin_unlock(&cache->object_list_lock);
 }
 
 /**

fs/fscache/cookie.c

@@ -95,6 +95,11 @@ struct fscache_cookie *__fscache_acquire_cookie(
 	atomic_set(&cookie->usage, 1);
 	atomic_set(&cookie->n_children, 0);
 
+	/* We keep the active count elevated until relinquishment to prevent an
+	 * attempt to wake up every time the object operations queue quiesces.
+	 */
+	atomic_set(&cookie->n_active, 1);
+
 	atomic_inc(&parent->usage);
 	atomic_inc(&parent->n_children);
 
@@ -177,7 +182,6 @@ static int fscache_acquire_non_index_cookie(struct fscache_cookie *cookie)
 
 	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
@@ -205,7 +209,7 @@ static int fscache_acquire_non_index_cookie(struct fscache_cookie *cookie)
 
 	/* initiate the process of looking up all the objects in the chain
 	 * (done by fscache_initialise_object()) */
-	fscache_enqueue_object(object);
+	fscache_raise_event(object, FSCACHE_OBJECT_EV_NEW_CHILD);
 
 	spin_unlock(&cookie->lock);
 
@@ -285,7 +289,7 @@ static int fscache_alloc_object(struct fscache_cache *cache,
 
 object_already_extant:
 	ret = -ENOBUFS;
-	if (object->state >= FSCACHE_OBJECT_DYING) {
+	if (fscache_object_is_dead(object)) {
 		spin_unlock(&cookie->lock);
 		goto error;
 	}
@@ -321,7 +325,7 @@ static int fscache_attach_object(struct fscache_cookie *cookie,
 	ret = -EEXIST;
 	hlist_for_each_entry(p, &cookie->backing_objects, cookie_link) {
 		if (p->cache == object->cache) {
-			if (p->state >= FSCACHE_OBJECT_DYING)
+			if (fscache_object_is_dying(p))
 				ret = -ENOBUFS;
 			goto cant_attach_object;
 		}
@@ -332,7 +336,7 @@ static int fscache_attach_object(struct fscache_cookie *cookie,
 	hlist_for_each_entry(p, &cookie->parent->backing_objects,
 			     cookie_link) {
 		if (p->cache == object->cache) {
-			if (p->state >= FSCACHE_OBJECT_DYING) {
+			if (fscache_object_is_dying(p)) {
 				ret = -ENOBUFS;
 				spin_unlock(&cookie->parent->lock);
 				goto cant_attach_object;
@@ -400,7 +404,7 @@ void __fscache_invalidate(struct fscache_cookie *cookie)
 			object = hlist_entry(cookie->backing_objects.first,
 					     struct fscache_object,
 					     cookie_link);
-			if (object->state < FSCACHE_OBJECT_DYING)
+			if (fscache_object_is_live(object))
 				fscache_raise_event(
 					object, FSCACHE_OBJECT_EV_INVALIDATE);
 		}
@@ -467,9 +471,7 @@ EXPORT_SYMBOL(__fscache_update_cookie);
  */
 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 (retire)
@@ -481,79 +483,48 @@ void __fscache_relinquish_cookie(struct fscache_cookie *cookie, int retire)
 		return;
 	}
 
-	_enter("%p{%s,%p},%d",
-	       cookie, cookie->def->name, cookie->netfs_data, retire);
+	_enter("%p{%s,%p,%d},%d",
+	       cookie, cookie->def->name, cookie->netfs_data,
+	       atomic_read(&cookie->n_active), retire);
+
+	ASSERTCMP(atomic_read(&cookie->n_active), >, 0);
 
 	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;
+	/* No further netfs-accessing operations on this cookie permitted */
+	set_bit(FSCACHE_COOKIE_RELINQUISHED, &cookie->flags);
+	if (retire)
+		set_bit(FSCACHE_COOKIE_RETIRED, &cookie->flags);
 
-try_again:
 	spin_lock(&cookie->lock);
-
-	/* break links with all the active objects */
-	while (!hlist_empty(&cookie->backing_objects)) {
-		int n_reads;
-		object = hlist_entry(cookie->backing_objects.first,
-				     struct fscache_object,
-				     cookie_link);
-
-		_debug("RELEASE OBJ%x", object->debug_id);
-
-		set_bit(FSCACHE_COOKIE_WAITING_ON_READS, &cookie->flags);
-		n_reads = atomic_read(&object->n_reads);
-		if (n_reads) {
-			int n_ops = object->n_ops;
-			int n_in_progress = object->n_in_progress;
-			spin_unlock(&cookie->lock);
-			printk(KERN_ERR "FS-Cache:"
-			       " Cookie '%s' still has %d outstanding reads (%d,%d)\n",
-			       cookie->def->name,
-			       n_reads, n_ops, n_in_progress);
-			wait_on_bit(&cookie->flags, FSCACHE_COOKIE_WAITING_ON_READS,
-				    fscache_wait_bit, TASK_UNINTERRUPTIBLE);
-			printk("Wait finished\n");
-			goto try_again;
-		}
-
-		/* 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();
+	hlist_for_each_entry(object, &cookie->backing_objects, cookie_link) {
+		fscache_raise_event(object, FSCACHE_OBJECT_EV_KILL);
 	}
+	spin_unlock(&cookie->lock);
 
-	/* detach pointers back to the netfs */
+	/* Wait for cessation of activity requiring access to the netfs (when
+	 * n_active reaches 0).
+	 */
+	if (!atomic_dec_and_test(&cookie->n_active))
+		wait_on_atomic_t(&cookie->n_active, fscache_wait_atomic_t,
+				 TASK_UNINTERRUPTIBLE);
+
+	/* Clear pointers back to the netfs */
 	cookie->netfs_data	= NULL;
 	cookie->def		= NULL;
-
-	spin_unlock(&cookie->lock);
+	BUG_ON(cookie->stores.rnode);
 
 	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 */
+	/* Dispose of the netfs's link to the cookie */
 	ASSERTCMP(atomic_read(&cookie->usage), >, 0);
 	fscache_cookie_put(cookie);
 

fs/fscache/fsdef.c

@@ -55,6 +55,7 @@ static struct fscache_cookie_def fscache_fsdef_index_def = {
 
 struct fscache_cookie fscache_fsdef_index = {
 	.usage		= ATOMIC_INIT(1),
+	.n_active	= ATOMIC_INIT(1),
 	.lock		= __SPIN_LOCK_UNLOCKED(fscache_fsdef_index.lock),
 	.backing_objects = HLIST_HEAD_INIT,
 	.def		= &fscache_fsdef_index_def,