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()

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)
@@ -481,8 +483,11 @@ 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",
@@ -490,62 +495,28 @@ void __fscache_relinquish_cookie(struct fscache_cookie *cookie, int retire)
 		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);
@@ -553,7 +524,7 @@ void __fscache_relinquish_cookie(struct fscache_cookie *cookie, int retire)
 		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,

fs/fscache/internal.h

@@ -93,14 +93,11 @@ static inline bool fscache_object_congested(void)
 
 extern int fscache_wait_bit(void *);
 extern int fscache_wait_bit_interruptible(void *);
+extern int fscache_wait_atomic_t(atomic_t *);
 
 /*
  * object.c
  */
-extern const char fscache_object_states_short[FSCACHE_OBJECT__NSTATES][5];
-
-extern void fscache_withdrawing_object(struct fscache_cache *,
-				       struct fscache_object *);
 extern void fscache_enqueue_object(struct fscache_object *);
 
 /*
@@ -110,8 +107,10 @@ extern void fscache_enqueue_object(struct fscache_object *);
 extern const struct file_operations fscache_objlist_fops;
 
 extern void fscache_objlist_add(struct fscache_object *);
+extern void fscache_objlist_remove(struct fscache_object *);
 #else
 #define fscache_objlist_add(object) do {} while(0)
+#define fscache_objlist_remove(object) do {} while(0)
 #endif
 
 /*
@@ -291,6 +290,10 @@ static inline void fscache_raise_event(struct fscache_object *object,
 				       unsigned event)
 {
 	BUG_ON(event >= NR_FSCACHE_OBJECT_EVENTS);
+#if 0
+	printk("*** fscache_raise_event(OBJ%d{%lx},%x)\n",
+	       object->debug_id, object->event_mask, (1 << event));
+#endif
 	if (!test_and_set_bit(event, &object->events) &&
 	    test_bit(event, &object->event_mask))
 		fscache_enqueue_object(object);

fs/fscache/main.c

@@ -205,7 +205,6 @@ int fscache_wait_bit(void *flags)
 	schedule();
 	return 0;
 }
-EXPORT_SYMBOL(fscache_wait_bit);
 
 /*
  * wait_on_bit() sleep function for interruptible waiting
@@ -215,4 +214,12 @@ int fscache_wait_bit_interruptible(void *flags)
 	schedule();
 	return signal_pending(current);
 }
-EXPORT_SYMBOL(fscache_wait_bit_interruptible);
+
+/*
+ * wait_on_atomic_t() sleep function for uninterruptible waiting
+ */
+int fscache_wait_atomic_t(atomic_t *p)
+{
+	schedule();
+	return 0;
+}

fs/fscache/netfs.c

@@ -40,6 +40,7 @@ int __fscache_register_netfs(struct fscache_netfs *netfs)
 	/* initialise the primary index cookie */
 	atomic_set(&netfs->primary_index->usage, 1);
 	atomic_set(&netfs->primary_index->n_children, 0);
+	atomic_set(&netfs->primary_index->n_active, 1);
 
 	netfs->primary_index->def		= &fscache_fsdef_netfs_def;
 	netfs->primary_index->parent		= &fscache_fsdef_index;

fs/fscache/object-list.c

@@ -70,13 +70,10 @@ void fscache_objlist_add(struct fscache_object *obj)
 	write_unlock(&fscache_object_list_lock);
 }
 
-/**
- * fscache_object_destroy - Note that a cache object is about to be destroyed
- * @object: The object to be destroyed
- *
- * Note the imminent destruction and deallocation of a cache object record.
+/*
+ * Remove an object from the object list.
  */
-void fscache_object_destroy(struct fscache_object *obj)
+void fscache_objlist_remove(struct fscache_object *obj)
 {
 	write_lock(&fscache_object_list_lock);
 
@@ -85,7 +82,6 @@ void fscache_object_destroy(struct fscache_object *obj)
 
 	write_unlock(&fscache_object_list_lock);
 }
-EXPORT_SYMBOL(fscache_object_destroy);
 
 /*
  * find the object in the tree on or after the specified index
@@ -166,15 +162,14 @@ static int fscache_objlist_show(struct seq_file *m, void *v)
 {
 	struct fscache_objlist_data *data = m->private;
 	struct fscache_object *obj = v;
+	struct fscache_cookie *cookie;
 	unsigned long config = data->config;
-	uint16_t keylen, auxlen;
 	char _type[3], *type;
-	bool no_cookie;
 	u8 *buf = data->buf, *p;
 
 	if ((unsigned long) v == 1) {
 		seq_puts(m, "OBJECT   PARENT   STAT CHLDN OPS OOP IPR EX READS"
-			 " EM EV F S"
+			 " EM EV FL S"
 			 " | NETFS_COOKIE_DEF TY FL NETFS_DATA");
 		if (config & (FSCACHE_OBJLIST_CONFIG_KEY |
 			      FSCACHE_OBJLIST_CONFIG_AUX))
@@ -193,7 +188,7 @@ static int fscache_objlist_show(struct seq_file *m, void *v)
 
 	if ((unsigned long) v == 2) {
 		seq_puts(m, "======== ======== ==== ===== === === === == ====="
-			 " == == = ="
+			 " == == == ="
 			 " | ================ == == ================");
 		if (config & (FSCACHE_OBJLIST_CONFIG_KEY |
 			      FSCACHE_OBJLIST_CONFIG_AUX))
@@ -216,10 +211,11 @@ static int fscache_objlist_show(struct seq_file *m, void *v)
 		}							\
 	} while(0)
 
+	cookie = obj->cookie;
 	if (~config) {
-		FILTER(obj->cookie,
+		FILTER(cookie->def,
 		       COOKIE, NOCOOKIE);
-		FILTER(obj->state != FSCACHE_OBJECT_ACTIVE ||
+		FILTER(fscache_object_is_active(obj) ||
 		       obj->n_ops != 0 ||
 		       obj->n_obj_ops != 0 ||
 		       obj->flags ||
@@ -235,10 +231,10 @@ static int fscache_objlist_show(struct seq_file *m, void *v)
 	}
 
 	seq_printf(m,
-		   "%8x %8x %s %5u %3u %3u %3u %2u %5u %2lx %2lx %1lx %1x | ",
+		   "%8x %8x %s %5u %3u %3u %3u %2u %5u %2lx %2lx %2lx %1x | ",
 		   obj->debug_id,
 		   obj->parent ? obj->parent->debug_id : -1,
-		   fscache_object_states_short[obj->state],
+		   obj->state->short_name,
 		   obj->n_children,
 		   obj->n_ops,
 		   obj->n_obj_ops,
@@ -250,48 +246,40 @@ static int fscache_objlist_show(struct seq_file *m, void *v)
 		   obj->flags,
 		   work_busy(&obj->work));
 
-	no_cookie = true;
-	keylen = auxlen = 0;
-	if (obj->cookie) {
-		spin_lock(&obj->lock);
-		if (obj->cookie) {
-			switch (obj->cookie->def->type) {
-			case 0:
-				type = "IX";
-				break;
-			case 1:
-				type = "DT";
-				break;
-			default:
-				sprintf(_type, "%02u",
-					obj->cookie->def->type);
-				type = _type;
-				break;
-			}
+	if (fscache_use_cookie(obj)) {
+		uint16_t keylen = 0, auxlen = 0;
 
-			seq_printf(m, "%-16s %s %2lx %16p",
-				   obj->cookie->def->name,
-				   type,
-				   obj->cookie->flags,
-				   obj->cookie->netfs_data);
-
-			if (obj->cookie->def->get_key &&
-			    config & FSCACHE_OBJLIST_CONFIG_KEY)
-				keylen = obj->cookie->def->get_key(
-					obj->cookie->netfs_data,
-					buf, 400);
-
-			if (obj->cookie->def->get_aux &&
-			    config & FSCACHE_OBJLIST_CONFIG_AUX)
-				auxlen = obj->cookie->def->get_aux(
-					obj->cookie->netfs_data,
-					buf + keylen, 512 - keylen);
-
-			no_cookie = false;
+		switch (cookie->def->type) {
+		case 0:
+			type = "IX";
+			break;
+		case 1:
+			type = "DT";
+			break;
+		default:
+			sprintf(_type, "%02u", cookie->def->type);
+			type = _type;
+			break;
 		}
-		spin_unlock(&obj->lock);
 
-		if (!no_cookie && (keylen > 0 || auxlen > 0)) {
+		seq_printf(m, "%-16s %s %2lx %16p",
+			   cookie->def->name,
+			   type,
+			   cookie->flags,
+			   cookie->netfs_data);
+
+		if (cookie->def->get_key &&
+		    config & FSCACHE_OBJLIST_CONFIG_KEY)
+			keylen = cookie->def->get_key(cookie->netfs_data,
+						      buf, 400);
+
+		if (cookie->def->get_aux &&
+		    config & FSCACHE_OBJLIST_CONFIG_AUX)
+			auxlen = cookie->def->get_aux(cookie->netfs_data,
+						      buf + keylen, 512 - keylen);
+		fscache_unuse_cookie(obj);
+
+		if (keylen > 0 || auxlen > 0) {
 			seq_printf(m, " ");
 			for (p = buf; keylen > 0; keylen--)
 				seq_printf(m, "%02x", *p++);
@@ -302,12 +290,11 @@ static int fscache_objlist_show(struct seq_file *m, void *v)
 					seq_printf(m, "%02x", *p++);
 			}
 		}
-	}
 
-	if (no_cookie)
-		seq_printf(m, "<no_cookie>\n");
-	else
 		seq_printf(m, "\n");
+	} else {
+		seq_printf(m, "<no_netfs>\n");
+	}
 	return 0;
 }
 

fs/fscache/operation.c

@@ -35,7 +35,7 @@ void fscache_enqueue_operation(struct fscache_operation *op)
 
 	ASSERT(list_empty(&op->pend_link));
 	ASSERT(op->processor != NULL);
-	ASSERTCMP(op->object->state, >=, FSCACHE_OBJECT_AVAILABLE);
+	ASSERT(fscache_object_is_available(op->object));
 	ASSERTCMP(atomic_read(&op->usage), >, 0);
 	ASSERTCMP(op->state, ==, FSCACHE_OP_ST_IN_PROGRESS);
 
@@ -119,7 +119,7 @@ int fscache_submit_exclusive_op(struct fscache_object *object,
 		/* need to issue a new write op after this */
 		clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
 		ret = 0;
-	} else if (object->state == FSCACHE_OBJECT_CREATING) {
+	} else if (test_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
 		op->object = object;
 		object->n_ops++;
 		object->n_exclusive++;	/* reads and writes must wait */
@@ -144,7 +144,7 @@ int fscache_submit_exclusive_op(struct fscache_object *object,
  */
 static void fscache_report_unexpected_submission(struct fscache_object *object,
 						 struct fscache_operation *op,
-						 unsigned long ostate)
+						 const struct fscache_state *ostate)
 {
 	static bool once_only;
 	struct fscache_operation *p;
@@ -155,11 +155,8 @@ static void fscache_report_unexpected_submission(struct fscache_object *object,
 	once_only = true;
 
 	kdebug("unexpected submission OP%x [OBJ%x %s]",
-	       op->debug_id, object->debug_id,
-	       fscache_object_states[object->state]);
-	kdebug("objstate=%s [%s]",
-	       fscache_object_states[object->state],
-	       fscache_object_states[ostate]);
+	       op->debug_id, object->debug_id, object->state->name);
+	kdebug("objstate=%s [%s]", object->state->name, ostate->name);
 	kdebug("objflags=%lx", object->flags);
 	kdebug("objevent=%lx [%lx]", object->events, object->event_mask);
 	kdebug("ops=%u inp=%u exc=%u",
@@ -190,7 +187,7 @@ static void fscache_report_unexpected_submission(struct fscache_object *object,
 int fscache_submit_op(struct fscache_object *object,
 		      struct fscache_operation *op)
 {
-	unsigned long ostate;
+	const struct fscache_state *ostate;
 	int ret;
 
 	_enter("{OBJ%x OP%x},{%u}",
@@ -226,16 +223,14 @@ int fscache_submit_op(struct fscache_object *object,
 			fscache_run_op(object, op);
 		}
 		ret = 0;
-	} else if (object->state == FSCACHE_OBJECT_CREATING) {
+	} else if (test_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
 		op->object = object;
 		object->n_ops++;
 		atomic_inc(&op->usage);
 		list_add_tail(&op->pend_link, &object->pending_ops);
 		fscache_stat(&fscache_n_op_pend);
 		ret = 0;
-	} else if (object->state == FSCACHE_OBJECT_DYING ||
-		   object->state == FSCACHE_OBJECT_LC_DYING ||
-		   object->state == FSCACHE_OBJECT_WITHDRAWING) {
+	} else if (fscache_object_is_dying(object)) {
 		fscache_stat(&fscache_n_op_rejected);
 		op->state = FSCACHE_OP_ST_CANCELLED;
 		ret = -ENOBUFS;
@@ -265,8 +260,8 @@ void fscache_abort_object(struct fscache_object *object)
 }
 
 /*
- * jump start the operation processing on an object
- * - caller must hold object->lock
+ * Jump start the operation processing on an object.  The caller must hold
+ * object->lock.
  */
 void fscache_start_operations(struct fscache_object *object)
 {
@@ -428,14 +423,10 @@ void fscache_put_operation(struct fscache_operation *op)
 
 	object = op->object;
 
-	if (test_bit(FSCACHE_OP_DEC_READ_CNT, &op->flags)) {
-		if (atomic_dec_and_test(&object->n_reads)) {
-			clear_bit(FSCACHE_COOKIE_WAITING_ON_READS,
-				  &object->cookie->flags);
-			wake_up_bit(&object->cookie->flags,
-				    FSCACHE_COOKIE_WAITING_ON_READS);
-		}
-	}
+	if (test_bit(FSCACHE_OP_DEC_READ_CNT, &op->flags))
+		atomic_dec(&object->n_reads);
+	if (test_bit(FSCACHE_OP_UNUSE_COOKIE, &op->flags))
+		fscache_unuse_cookie(object);
 
 	/* now... we may get called with the object spinlock held, so we
 	 * complete the cleanup here only if we can immediately acquire the

fs/fscache/page.c

@@ -109,7 +109,7 @@ bool __fscache_maybe_release_page(struct fscache_cookie *cookie,
 	 * allocator as the work threads writing to the cache may all end up
 	 * sleeping on memory allocation, so we may need to impose a timeout
 	 * too. */
-	if (!(gfp & __GFP_WAIT)) {
+	if (!(gfp & __GFP_WAIT) || !(gfp & __GFP_FS)) {
 		fscache_stat(&fscache_n_store_vmscan_busy);
 		return false;
 	}
@@ -163,10 +163,12 @@ static void fscache_attr_changed_op(struct fscache_operation *op)
 
 	fscache_stat(&fscache_n_attr_changed_calls);
 
-	if (fscache_object_is_active(object)) {
+	if (fscache_object_is_active(object) &&
+	    fscache_use_cookie(object)) {
 		fscache_stat(&fscache_n_cop_attr_changed);
 		ret = object->cache->ops->attr_changed(object);
 		fscache_stat_d(&fscache_n_cop_attr_changed);
+		fscache_unuse_cookie(object);
 		if (ret < 0)
 			fscache_abort_object(object);
 	}
@@ -233,7 +235,7 @@ static void fscache_release_retrieval_op(struct fscache_operation *_op)
 
 	_enter("{OP%x}", op->op.debug_id);
 
-	ASSERTCMP(op->n_pages, ==, 0);
+	ASSERTCMP(atomic_read(&op->n_pages), ==, 0);
 
 	fscache_hist(fscache_retrieval_histogram, op->start_time);
 	if (op->context)
@@ -246,6 +248,7 @@ static void fscache_release_retrieval_op(struct fscache_operation *_op)
  * allocate a retrieval op
  */
 static struct fscache_retrieval *fscache_alloc_retrieval(
+	struct fscache_cookie *cookie,
 	struct address_space *mapping,
 	fscache_rw_complete_t end_io_func,
 	void *context)
@@ -260,7 +263,10 @@ static struct fscache_retrieval *fscache_alloc_retrieval(
 	}
 
 	fscache_operation_init(&op->op, NULL, fscache_release_retrieval_op);
-	op->op.flags	= FSCACHE_OP_MYTHREAD | (1 << FSCACHE_OP_WAITING);
+	atomic_inc(&cookie->n_active);
+	op->op.flags	= FSCACHE_OP_MYTHREAD |
+		(1UL << FSCACHE_OP_WAITING) |
+		(1UL << FSCACHE_OP_UNUSE_COOKIE);
 	op->mapping	= mapping;
 	op->end_io_func	= end_io_func;
 	op->context	= context;
@@ -310,7 +316,7 @@ static void fscache_do_cancel_retrieval(struct fscache_operation *_op)
 	struct fscache_retrieval *op =
 		container_of(_op, struct fscache_retrieval, op);
 
-	op->n_pages = 0;
+	atomic_set(&op->n_pages, 0);
 }
 
 /*
@@ -394,12 +400,13 @@ int __fscache_read_or_alloc_page(struct fscache_cookie *cookie,
 	if (fscache_wait_for_deferred_lookup(cookie) < 0)
 		return -ERESTARTSYS;
 
-	op = fscache_alloc_retrieval(page->mapping, end_io_func, context);
+	op = fscache_alloc_retrieval(cookie, page->mapping,
+				     end_io_func,context);
 	if (!op) {
 		_leave(" = -ENOMEM");
 		return -ENOMEM;
 	}
-	op->n_pages = 1;
+	atomic_set(&op->n_pages, 1);
 
 	spin_lock(&cookie->lock);
 
@@ -408,7 +415,7 @@ int __fscache_read_or_alloc_page(struct fscache_cookie *cookie,
 	object = hlist_entry(cookie->backing_objects.first,
 			     struct fscache_object, cookie_link);
 
-	ASSERTCMP(object->state, >, FSCACHE_OBJECT_LOOKING_UP);
+	ASSERT(test_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags));
 
 	atomic_inc(&object->n_reads);
 	__set_bit(FSCACHE_OP_DEC_READ_CNT, &op->op.flags);
@@ -465,6 +472,7 @@ int __fscache_read_or_alloc_page(struct fscache_cookie *cookie,
 	atomic_dec(&object->n_reads);
 nobufs_unlock:
 	spin_unlock(&cookie->lock);
+	atomic_dec(&cookie->n_active);
 	kfree(op);
 nobufs:
 	fscache_stat(&fscache_n_retrievals_nobufs);
@@ -522,10 +530,10 @@ int __fscache_read_or_alloc_pages(struct fscache_cookie *cookie,
 	if (fscache_wait_for_deferred_lookup(cookie) < 0)
 		return -ERESTARTSYS;
 
-	op = fscache_alloc_retrieval(mapping, end_io_func, context);
+	op = fscache_alloc_retrieval(cookie, mapping, end_io_func, context);
 	if (!op)
 		return -ENOMEM;
-	op->n_pages = *nr_pages;
+	atomic_set(&op->n_pages, *nr_pages);
 
 	spin_lock(&cookie->lock);
 
@@ -589,6 +597,7 @@ int __fscache_read_or_alloc_pages(struct fscache_cookie *cookie,
 	atomic_dec(&object->n_reads);
 nobufs_unlock:
 	spin_unlock(&cookie->lock);
+	atomic_dec(&cookie->n_active);
 	kfree(op);
 nobufs:
 	fscache_stat(&fscache_n_retrievals_nobufs);
@@ -631,10 +640,10 @@ int __fscache_alloc_page(struct fscache_cookie *cookie,
 	if (fscache_wait_for_deferred_lookup(cookie) < 0)
 		return -ERESTARTSYS;
 
-	op = fscache_alloc_retrieval(page->mapping, NULL, NULL);
+	op = fscache_alloc_retrieval(cookie, page->mapping, NULL, NULL);
 	if (!op)
 		return -ENOMEM;
-	op->n_pages = 1;
+	atomic_set(&op->n_pages, 1);
 
 	spin_lock(&cookie->lock);
 
@@ -675,6 +684,7 @@ int __fscache_alloc_page(struct fscache_cookie *cookie,
 
 nobufs_unlock:
 	spin_unlock(&cookie->lock);
+	atomic_dec(&cookie->n_active);
 	kfree(op);
 nobufs:
 	fscache_stat(&fscache_n_allocs_nobufs);
@@ -729,8 +739,9 @@ static void fscache_write_op(struct fscache_operation *_op)
 		 */
 		spin_unlock(&object->lock);
 		fscache_op_complete(&op->op, false);
-		_leave(" [cancel] op{f=%lx s=%u} obj{s=%u f=%lx}",
-		       _op->flags, _op->state, object->state, object->flags);
+		_leave(" [cancel] op{f=%lx s=%u} obj{s=%s f=%lx}",
+		       _op->flags, _op->state, object->state->short_name,
+		       object->flags);
 		return;
 	}
 
@@ -796,11 +807,16 @@ void fscache_invalidate_writes(struct fscache_cookie *cookie)
 
 	_enter("");
 
-	while (spin_lock(&cookie->stores_lock),
-	       n = radix_tree_gang_lookup_tag(&cookie->stores, results, 0,
-					      ARRAY_SIZE(results),
-					      FSCACHE_COOKIE_PENDING_TAG),
-	       n > 0) {
+	for (;;) {
+		spin_lock(&cookie->stores_lock);
+		n = radix_tree_gang_lookup_tag(&cookie->stores, results, 0,
+					       ARRAY_SIZE(results),
+					       FSCACHE_COOKIE_PENDING_TAG);
+		if (n == 0) {
+			spin_unlock(&cookie->stores_lock);
+			break;
+		}
+
 		for (i = n - 1; i >= 0; i--) {
 			page = results[i];
 			radix_tree_delete(&cookie->stores, page->index);
@@ -812,7 +828,6 @@ void fscache_invalidate_writes(struct fscache_cookie *cookie)
 			page_cache_release(results[i]);
 	}
 
-	spin_unlock(&cookie->stores_lock);
 	_leave("");
 }
 
@@ -829,14 +844,12 @@ void fscache_invalidate_writes(struct fscache_cookie *cookie)
  *  (1) negative lookup, object not yet created (FSCACHE_COOKIE_CREATING is
  *      set)
  *
- *	(a) no writes yet (set FSCACHE_COOKIE_PENDING_FILL and queue deferred
- *	    fill op)
+ *	(a) no writes yet
  *
  *	(b) writes deferred till post-creation (mark page for writing and
  *	    return immediately)
  *
  *  (2) negative lookup, object created, initial fill being made from netfs
- *      (FSCACHE_COOKIE_INITIAL_FILL is set)
  *
  *	(a) fill point not yet reached this page (mark page for writing and
  *          return)
@@ -873,7 +886,9 @@ int __fscache_write_page(struct fscache_cookie *cookie,
 
 	fscache_operation_init(&op->op, fscache_write_op,
 			       fscache_release_write_op);
-	op->op.flags = FSCACHE_OP_ASYNC | (1 << FSCACHE_OP_WAITING);
+	op->op.flags = FSCACHE_OP_ASYNC |
+		(1 << FSCACHE_OP_WAITING) |
+		(1 << FSCACHE_OP_UNUSE_COOKIE);
 
 	ret = radix_tree_preload(gfp & ~__GFP_HIGHMEM);
 	if (ret < 0)
@@ -919,6 +934,7 @@ int __fscache_write_page(struct fscache_cookie *cookie,
 	op->op.debug_id	= atomic_inc_return(&fscache_op_debug_id);
 	op->store_limit = object->store_limit;
 
+	atomic_inc(&cookie->n_active);
 	if (fscache_submit_op(object, &op->op) < 0)
 		goto submit_failed;
 
@@ -945,6 +961,7 @@ int __fscache_write_page(struct fscache_cookie *cookie,
 	return 0;
 
 submit_failed:
+	atomic_dec(&cookie->n_active);
 	spin_lock(&cookie->stores_lock);
 	radix_tree_delete(&cookie->stores, page->index);
 	spin_unlock(&cookie->stores_lock);

include/linux/fscache-cache.h

@@ -97,7 +97,8 @@ struct fscache_operation {
 #define FSCACHE_OP_WAITING	4	/* cleared when op is woken */
 #define FSCACHE_OP_EXCLUSIVE	5	/* exclusive op, other ops must wait */
 #define FSCACHE_OP_DEC_READ_CNT	6	/* decrement object->n_reads on destruction */
-#define FSCACHE_OP_KEEP_FLAGS	0x0070	/* flags to keep when repurposing an op */
+#define FSCACHE_OP_UNUSE_COOKIE	7	/* call fscache_unuse_cookie() on completion */
+#define FSCACHE_OP_KEEP_FLAGS	0x00f0	/* flags to keep when repurposing an op */
 
 	enum fscache_operation_state state;
 	atomic_t		usage;
@@ -150,7 +151,7 @@ struct fscache_retrieval {
 	void			*context;	/* netfs read context (pinned) */
 	struct list_head	to_do;		/* list of things to be done by the backend */
 	unsigned long		start_time;	/* time at which retrieval started */
-	unsigned		n_pages;	/* number of pages to be retrieved */
+	atomic_t		n_pages;	/* number of pages to be retrieved */
 };
 
 typedef int (*fscache_page_retrieval_func_t)(struct fscache_retrieval *op,
@@ -194,15 +195,14 @@ static inline void fscache_enqueue_retrieval(struct fscache_retrieval *op)
 static inline void fscache_retrieval_complete(struct fscache_retrieval *op,
 					      int n_pages)
 {
-	op->n_pages -= n_pages;
-	if (op->n_pages <= 0)
+	atomic_sub(n_pages, &op->n_pages);
+	if (atomic_read(&op->n_pages) <= 0)
 		fscache_op_complete(&op->op, true);
 }
 
 /**
  * fscache_put_retrieval - Drop a reference to a retrieval operation
  * @op: The retrieval operation affected
- * @n_pages: The number of pages to account for
  *
  * Drop a reference to a retrieval operation.
  */
@@ -314,6 +314,7 @@ struct fscache_cache_ops {
 struct fscache_cookie {
 	atomic_t			usage;		/* number of users of this cookie */
 	atomic_t			n_children;	/* number of children of this cookie */
+	atomic_t			n_active;	/* number of active users of netfs ptrs */
 	spinlock_t			lock;
 	spinlock_t			stores_lock;	/* lock on page store tree */
 	struct hlist_head		backing_objects; /* object(s) backing this file/index */
@@ -326,13 +327,11 @@ struct fscache_cookie {
 
 	unsigned long			flags;
 #define FSCACHE_COOKIE_LOOKING_UP	0	/* T if non-index cookie being looked up still */
-#define FSCACHE_COOKIE_CREATING		1	/* T if non-index object being created still */
-#define FSCACHE_COOKIE_NO_DATA_YET	2	/* T if new object with no cached data yet */
-#define FSCACHE_COOKIE_PENDING_FILL	3	/* T if pending initial fill on object */
-#define FSCACHE_COOKIE_FILLING		4	/* T if filling object incrementally */
-#define FSCACHE_COOKIE_UNAVAILABLE	5	/* T if cookie is unavailable (error, etc) */
-#define FSCACHE_COOKIE_WAITING_ON_READS	6	/* T if cookie is waiting on reads */
-#define FSCACHE_COOKIE_INVALIDATING	7	/* T if cookie is being invalidated */
+#define FSCACHE_COOKIE_NO_DATA_YET	1	/* T if new object with no cached data yet */
+#define FSCACHE_COOKIE_UNAVAILABLE	2	/* T if cookie is unavailable (error, etc) */
+#define FSCACHE_COOKIE_INVALIDATING	3	/* T if cookie is being invalidated */
+#define FSCACHE_COOKIE_RELINQUISHED	4	/* T if cookie has been relinquished */
+#define FSCACHE_COOKIE_RETIRED		5	/* T if cookie was retired */
 };
 
 extern struct fscache_cookie fscache_fsdef_index;
@@ -341,45 +340,40 @@ extern struct fscache_cookie fscache_fsdef_index;
  * Event list for fscache_object::{event_mask,events}
  */
 enum {
-	FSCACHE_OBJECT_EV_REQUEUE,	/* T if object should be requeued */
+	FSCACHE_OBJECT_EV_NEW_CHILD,	/* T if object has a new child */
+	FSCACHE_OBJECT_EV_PARENT_READY,	/* T if object's parent is ready */
 	FSCACHE_OBJECT_EV_UPDATE,	/* T if object should be updated */
 	FSCACHE_OBJECT_EV_INVALIDATE,	/* T if cache requested object invalidation */
 	FSCACHE_OBJECT_EV_CLEARED,	/* T if accessors all gone */
 	FSCACHE_OBJECT_EV_ERROR,	/* T if fatal error occurred during processing */
-	FSCACHE_OBJECT_EV_RELEASE,	/* T if netfs requested object release */
-	FSCACHE_OBJECT_EV_RETIRE,	/* T if netfs requested object retirement */
-	FSCACHE_OBJECT_EV_WITHDRAW,	/* T if cache requested object withdrawal */
+	FSCACHE_OBJECT_EV_KILL,		/* T if netfs relinquished or cache withdrew object */
 	NR_FSCACHE_OBJECT_EVENTS
 };
 
 #define FSCACHE_OBJECT_EVENTS_MASK ((1UL << NR_FSCACHE_OBJECT_EVENTS) - 1)
 
+/*
+ * States for object state machine.
+ */
+struct fscache_transition {
+	unsigned long events;
+	const struct fscache_state *transit_to;
+};
+
+struct fscache_state {
+	char name[24];
+	char short_name[8];
+	const struct fscache_state *(*work)(struct fscache_object *object,
+					    int event);
+	const struct fscache_transition transitions[];
+};
+
 /*
  * on-disk cache file or index handle
  */
 struct fscache_object {
-	enum fscache_object_state {
-		FSCACHE_OBJECT_INIT,		/* object in initial unbound state */
-		FSCACHE_OBJECT_LOOKING_UP,	/* looking up object */
-		FSCACHE_OBJECT_CREATING,	/* creating object */
-
-		/* active states */
-		FSCACHE_OBJECT_AVAILABLE,	/* cleaning up object after creation */
-		FSCACHE_OBJECT_ACTIVE,		/* object is usable */
-		FSCACHE_OBJECT_INVALIDATING,	/* object is invalidating */
-		FSCACHE_OBJECT_UPDATING,	/* object is updating */
-
-		/* terminal states */
-		FSCACHE_OBJECT_DYING,		/* object waiting for accessors to finish */
-		FSCACHE_OBJECT_LC_DYING,	/* object cleaning up after lookup/create */
-		FSCACHE_OBJECT_ABORT_INIT,	/* abort the init state */
-		FSCACHE_OBJECT_RELEASING,	/* releasing object */
-		FSCACHE_OBJECT_RECYCLING,	/* retiring object */
-		FSCACHE_OBJECT_WITHDRAWING,	/* withdrawing object */
-		FSCACHE_OBJECT_DEAD,		/* object is now dead */
-		FSCACHE_OBJECT__NSTATES
-	} state;
-
+	const struct fscache_state *state;	/* Object state machine state */
+	const struct fscache_transition *oob_table; /* OOB state transition table */
 	int			debug_id;	/* debugging ID */
 	int			n_children;	/* number of child objects */
 	int			n_ops;		/* number of extant ops on object */
@@ -390,6 +384,7 @@ struct fscache_object {
 	spinlock_t		lock;		/* state and operations lock */
 
 	unsigned long		lookup_jif;	/* time at which lookup started */
+	unsigned long		oob_event_mask;	/* OOB events this object is interested in */
 	unsigned long		event_mask;	/* events this object is interested in */
 	unsigned long		events;		/* events to be processed by this object
 						 * (order is important - using fls) */
@@ -398,6 +393,9 @@ struct fscache_object {
 #define FSCACHE_OBJECT_LOCK		0	/* T if object is busy being processed */
 #define FSCACHE_OBJECT_PENDING_WRITE	1	/* T if object has pending write */
 #define FSCACHE_OBJECT_WAITING		2	/* T if object is waiting on its parent */
+#define FSCACHE_OBJECT_IS_LIVE		3	/* T if object is not withdrawn or relinquished */
+#define FSCACHE_OBJECT_IS_LOOKED_UP	4	/* T if object has been looked up */
+#define FSCACHE_OBJECT_IS_AVAILABLE	5	/* T if object has become active */
 
 	struct list_head	cache_link;	/* link in cache->object_list */
 	struct hlist_node	cookie_link;	/* link in cookie->backing_objects */
@@ -415,62 +413,40 @@ struct fscache_object {
 	loff_t			store_limit_l;	/* current storage limit */
 };
 
-extern const char *fscache_object_states[];
+extern void fscache_object_init(struct fscache_object *, struct fscache_cookie *,
+				struct fscache_cache *);
+extern void fscache_object_destroy(struct fscache_object *);
 
-#define fscache_object_is_active(obj)			      \
-	(!test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) &&  \
-	 (obj)->state >= FSCACHE_OBJECT_AVAILABLE &&	      \
-	 (obj)->state < FSCACHE_OBJECT_DYING)
+extern void fscache_object_lookup_negative(struct fscache_object *object);
+extern void fscache_obtained_object(struct fscache_object *object);
 
-#define fscache_object_is_dead(obj)				\
-	(test_bit(FSCACHE_IOERROR, &(obj)->cache->flags) &&	\
-	 (obj)->state >= FSCACHE_OBJECT_DYING)
+static inline bool fscache_object_is_live(struct fscache_object *object)
+{
+	return test_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
+}
 
-extern void fscache_object_work_func(struct work_struct *work);
+static inline bool fscache_object_is_dying(struct fscache_object *object)
+{
+	return !fscache_object_is_live(object);
+}
 
-/**
- * fscache_object_init - Initialise a cache object description
- * @object: Object description
- *
- * Initialise a cache object description to its basic values.
- *
- * See Documentation/filesystems/caching/backend-api.txt for a complete
- * description.
- */
-static inline
-void fscache_object_init(struct fscache_object *object,
-			 struct fscache_cookie *cookie,
-			 struct fscache_cache *cache)
+static inline bool fscache_object_is_available(struct fscache_object *object)
 {
-	atomic_inc(&cache->object_count);
-
-	object->state = FSCACHE_OBJECT_INIT;
-	spin_lock_init(&object->lock);
-	INIT_LIST_HEAD(&object->cache_link);
-	INIT_HLIST_NODE(&object->cookie_link);
-	INIT_WORK(&object->work, fscache_object_work_func);
-	INIT_LIST_HEAD(&object->dependents);
-	INIT_LIST_HEAD(&object->dep_link);
-	INIT_LIST_HEAD(&object->pending_ops);
-	object->n_children = 0;
-	object->n_ops = object->n_in_progress = object->n_exclusive = 0;
-	object->events = object->event_mask = 0;
-	object->flags = 0;
-	object->store_limit = 0;
-	object->store_limit_l = 0;
-	object->cache = cache;
-	object->cookie = cookie;
-	object->parent = NULL;
+	return test_bit(FSCACHE_OBJECT_IS_AVAILABLE, &object->flags);
 }
 
-extern void fscache_object_lookup_negative(struct fscache_object *object);
-extern void fscache_obtained_object(struct fscache_object *object);
+static inline bool fscache_object_is_active(struct fscache_object *object)
+{
+	return fscache_object_is_available(object) &&
+		fscache_object_is_live(object) &&
+		!test_bit(FSCACHE_IOERROR, &object->cache->flags);
+}
 
-#ifdef CONFIG_FSCACHE_OBJECT_LIST
-extern void fscache_object_destroy(struct fscache_object *object);
-#else
-#define fscache_object_destroy(object) do {} while(0)
-#endif
+static inline bool fscache_object_is_dead(struct fscache_object *object)
+{
+	return fscache_object_is_dying(object) &&
+		test_bit(FSCACHE_IOERROR, &object->cache->flags);
+}
 
 /**
  * fscache_object_destroyed - Note destruction of an object in a cache
@@ -531,6 +507,33 @@ static inline void fscache_end_io(struct fscache_retrieval *op,
 	op->end_io_func(page, op->context, error);
 }
 
+/**
+ * fscache_use_cookie - Request usage of cookie attached to an object
+ * @object: Object description
+ * 
+ * Request usage of the cookie attached to an object.  NULL is returned if the
+ * relinquishment had reduced the cookie usage count to 0.
+ */
+static inline bool fscache_use_cookie(struct fscache_object *object)
+{
+	struct fscache_cookie *cookie = object->cookie;
+	return atomic_inc_not_zero(&cookie->n_active) != 0;
+}
+
+/**
+ * fscache_unuse_cookie - Cease usage of cookie attached to an object
+ * @object: Object description
+ * 
+ * Cease usage of the cookie attached to an object.  When the users count
+ * reaches zero then the cookie relinquishment will be permitted to proceed.
+ */
+static inline void fscache_unuse_cookie(struct fscache_object *object)
+{
+	struct fscache_cookie *cookie = object->cookie;
+	if (atomic_dec_and_test(&cookie->n_active))
+		wake_up_atomic_t(&cookie->n_active);
+}
+
 /*
  * out-of-line cache backend functions
  */

include/linux/wait.h

@@ -23,6 +23,7 @@ struct __wait_queue {
 struct wait_bit_key {
 	void *flags;
 	int bit_nr;
+#define WAIT_ATOMIC_T_BIT_NR -1
 };
 
 struct wait_bit_queue {
@@ -60,6 +61,9 @@ struct task_struct;
 #define __WAIT_BIT_KEY_INITIALIZER(word, bit)				\
 	{ .flags = word, .bit_nr = bit, }
 
+#define __WAIT_ATOMIC_T_KEY_INITIALIZER(p)				\
+	{ .flags = p, .bit_nr = WAIT_ATOMIC_T_BIT_NR, }
+
 extern void __init_waitqueue_head(wait_queue_head_t *q, const char *name, struct lock_class_key *);
 
 #define init_waitqueue_head(q)				\
@@ -146,8 +150,10 @@ void __wake_up_bit(wait_queue_head_t *, void *, int);
 int __wait_on_bit(wait_queue_head_t *, struct wait_bit_queue *, int (*)(void *), unsigned);
 int __wait_on_bit_lock(wait_queue_head_t *, struct wait_bit_queue *, int (*)(void *), unsigned);
 void wake_up_bit(void *, int);
+void wake_up_atomic_t(atomic_t *);
 int out_of_line_wait_on_bit(void *, int, int (*)(void *), unsigned);
 int out_of_line_wait_on_bit_lock(void *, int, int (*)(void *), unsigned);
+int out_of_line_wait_on_atomic_t(atomic_t *, int (*)(atomic_t *), unsigned);
 wait_queue_head_t *bit_waitqueue(void *, int);
 
 #define wake_up(x)			__wake_up(x, TASK_NORMAL, 1, NULL)
@@ -902,5 +908,23 @@ static inline int wait_on_bit_lock(void *word, int bit,
 		return 0;
 	return out_of_line_wait_on_bit_lock(word, bit, action, mode);
 }
+
+/**
+ * wait_on_atomic_t - Wait for an atomic_t to become 0
+ * @val: The atomic value being waited on, a kernel virtual address
+ * @action: the function used to sleep, which may take special actions
+ * @mode: the task state to sleep in
+ *
+ * Wait for an atomic_t to become 0.  We abuse the bit-wait waitqueue table for
+ * the purpose of getting a waitqueue, but we set the key to a bit number
+ * outside of the target 'word'.
+ */
+static inline
+int wait_on_atomic_t(atomic_t *val, int (*action)(atomic_t *), unsigned mode)
+{
+	if (atomic_read(val) == 0)
+		return 0;
+	return out_of_line_wait_on_atomic_t(val, action, mode);
+}
 	
 #endif

kernel/wait.c

@@ -287,3 +287,91 @@ wait_queue_head_t *bit_waitqueue(void *word, int bit)
 	return &zone->wait_table[hash_long(val, zone->wait_table_bits)];
 }
 EXPORT_SYMBOL(bit_waitqueue);
+
+/*
+ * Manipulate the atomic_t address to produce a better bit waitqueue table hash
+ * index (we're keying off bit -1, but that would produce a horrible hash
+ * value).
+ */
+static inline wait_queue_head_t *atomic_t_waitqueue(atomic_t *p)
+{
+	if (BITS_PER_LONG == 64) {
+		unsigned long q = (unsigned long)p;
+		return bit_waitqueue((void *)(q & ~1), q & 1);
+	}
+	return bit_waitqueue(p, 0);
+}
+
+static int wake_atomic_t_function(wait_queue_t *wait, unsigned mode, int sync,
+				  void *arg)
+{
+	struct wait_bit_key *key = arg;
+	struct wait_bit_queue *wait_bit
+		= container_of(wait, struct wait_bit_queue, wait);
+	atomic_t *val = key->flags;
+
+	if (wait_bit->key.flags != key->flags ||
+	    wait_bit->key.bit_nr != key->bit_nr ||
+	    atomic_read(val) != 0)
+		return 0;
+	return autoremove_wake_function(wait, mode, sync, key);
+}
+
+/*
+ * To allow interruptible waiting and asynchronous (i.e. nonblocking) waiting,
+ * the actions of __wait_on_atomic_t() are permitted return codes.  Nonzero
+ * return codes halt waiting and return.
+ */
+static __sched
+int __wait_on_atomic_t(wait_queue_head_t *wq, struct wait_bit_queue *q,
+		       int (*action)(atomic_t *), unsigned mode)
+{
+	atomic_t *val;
+	int ret = 0;
+
+	do {
+		prepare_to_wait(wq, &q->wait, mode);
+		val = q->key.flags;
+		if (atomic_read(val) == 0)
+			ret = (*action)(val);
+	} while (!ret && atomic_read(val) != 0);
+	finish_wait(wq, &q->wait);
+	return ret;
+}
+
+#define DEFINE_WAIT_ATOMIC_T(name, p)					\
+	struct wait_bit_queue name = {					\
+		.key = __WAIT_ATOMIC_T_KEY_INITIALIZER(p),		\
+		.wait	= {						\
+			.private	= current,			\
+			.func		= wake_atomic_t_function,	\
+			.task_list	=				\
+				LIST_HEAD_INIT((name).wait.task_list),	\
+		},							\
+	}
+
+__sched int out_of_line_wait_on_atomic_t(atomic_t *p, int (*action)(atomic_t *),
+					 unsigned mode)
+{
+	wait_queue_head_t *wq = atomic_t_waitqueue(p);
+	DEFINE_WAIT_ATOMIC_T(wait, p);
+
+	return __wait_on_atomic_t(wq, &wait, action, mode);
+}
+EXPORT_SYMBOL(out_of_line_wait_on_atomic_t);
+
+/**
+ * wake_up_atomic_t - Wake up a waiter on a atomic_t
+ * @word: The word being waited on, a kernel virtual address
+ * @bit: The bit of the word being waited on
+ *
+ * Wake up anyone waiting for the atomic_t to go to zero.
+ *
+ * Abuse the bit-waker function and its waitqueue hash table set (the atomic_t
+ * check is done by the waiter's wake function, not the by the waker itself).
+ */
+void wake_up_atomic_t(atomic_t *p)
+{
+	__wake_up_bit(atomic_t_waitqueue(p), p, WAIT_ATOMIC_T_BIT_NR);
+}
+EXPORT_SYMBOL(wake_up_atomic_t);