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/object.c

@@ -15,52 +15,131 @@
 #define FSCACHE_DEBUG_LEVEL COOKIE
 #include <linux/module.h>
 #include <linux/slab.h>
+#include <linux/prefetch.h>
 #include "internal.h"
 
-const char *fscache_object_states[FSCACHE_OBJECT__NSTATES] = {
-	[FSCACHE_OBJECT_INIT]		= "OBJECT_INIT",
-	[FSCACHE_OBJECT_LOOKING_UP]	= "OBJECT_LOOKING_UP",
-	[FSCACHE_OBJECT_CREATING]	= "OBJECT_CREATING",
-	[FSCACHE_OBJECT_AVAILABLE]	= "OBJECT_AVAILABLE",
-	[FSCACHE_OBJECT_ACTIVE]		= "OBJECT_ACTIVE",
-	[FSCACHE_OBJECT_INVALIDATING]	= "OBJECT_INVALIDATING",
-	[FSCACHE_OBJECT_UPDATING]	= "OBJECT_UPDATING",
-	[FSCACHE_OBJECT_DYING]		= "OBJECT_DYING",
-	[FSCACHE_OBJECT_LC_DYING]	= "OBJECT_LC_DYING",
-	[FSCACHE_OBJECT_ABORT_INIT]	= "OBJECT_ABORT_INIT",
-	[FSCACHE_OBJECT_RELEASING]	= "OBJECT_RELEASING",
-	[FSCACHE_OBJECT_RECYCLING]	= "OBJECT_RECYCLING",
-	[FSCACHE_OBJECT_WITHDRAWING]	= "OBJECT_WITHDRAWING",
-	[FSCACHE_OBJECT_DEAD]		= "OBJECT_DEAD",
+static const struct fscache_state *fscache_abort_initialisation(struct fscache_object *, int);
+static const struct fscache_state *fscache_kill_dependents(struct fscache_object *, int);
+static const struct fscache_state *fscache_drop_object(struct fscache_object *, int);
+static const struct fscache_state *fscache_initialise_object(struct fscache_object *, int);
+static const struct fscache_state *fscache_invalidate_object(struct fscache_object *, int);
+static const struct fscache_state *fscache_jumpstart_dependents(struct fscache_object *, int);
+static const struct fscache_state *fscache_kill_object(struct fscache_object *, int);
+static const struct fscache_state *fscache_lookup_failure(struct fscache_object *, int);
+static const struct fscache_state *fscache_look_up_object(struct fscache_object *, int);
+static const struct fscache_state *fscache_object_available(struct fscache_object *, int);
+static const struct fscache_state *fscache_parent_ready(struct fscache_object *, int);
+static const struct fscache_state *fscache_update_object(struct fscache_object *, int);
+
+#define __STATE_NAME(n) fscache_osm_##n
+#define STATE(n) (&__STATE_NAME(n))
+
+/*
+ * Define a work state.  Work states are execution states.  No event processing
+ * is performed by them.  The function attached to a work state returns a
+ * pointer indicating the next state to which the state machine should
+ * transition.  Returning NO_TRANSIT repeats the current state, but goes back
+ * to the scheduler first.
+ */
+#define WORK_STATE(n, sn, f) \
+	const struct fscache_state __STATE_NAME(n) = {			\
+		.name = #n,						\
+		.short_name = sn,					\
+		.work = f						\
+	}
+
+/*
+ * Returns from work states.
+ */
+#define transit_to(state) ({ prefetch(&STATE(state)->work); STATE(state); })
+
+#define NO_TRANSIT ((struct fscache_state *)NULL)
+
+/*
+ * Define a wait state.  Wait states are event processing states.  No execution
+ * is performed by them.  Wait states are just tables of "if event X occurs,
+ * clear it and transition to state Y".  The dispatcher returns to the
+ * scheduler if none of the events in which the wait state has an interest are
+ * currently pending.
+ */
+#define WAIT_STATE(n, sn, ...) \
+	const struct fscache_state __STATE_NAME(n) = {			\
+		.name = #n,						\
+		.short_name = sn,					\
+		.work = NULL,						\
+		.transitions = { __VA_ARGS__, { 0, NULL } }		\
+	}
+
+#define TRANSIT_TO(state, emask) \
+	{ .events = (emask), .transit_to = STATE(state) }
+
+/*
+ * The object state machine.
+ */
+static WORK_STATE(INIT_OBJECT,		"INIT", fscache_initialise_object);
+static WORK_STATE(PARENT_READY,		"PRDY", fscache_parent_ready);
+static WORK_STATE(ABORT_INIT,		"ABRT", fscache_abort_initialisation);
+static WORK_STATE(LOOK_UP_OBJECT,	"LOOK", fscache_look_up_object);
+static WORK_STATE(CREATE_OBJECT,	"CRTO", fscache_look_up_object);
+static WORK_STATE(OBJECT_AVAILABLE,	"AVBL", fscache_object_available);
+static WORK_STATE(JUMPSTART_DEPS,	"JUMP", fscache_jumpstart_dependents);
+
+static WORK_STATE(INVALIDATE_OBJECT,	"INVL", fscache_invalidate_object);
+static WORK_STATE(UPDATE_OBJECT,	"UPDT", fscache_update_object);
+
+static WORK_STATE(LOOKUP_FAILURE,	"LCFL", fscache_lookup_failure);
+static WORK_STATE(KILL_OBJECT,		"KILL", fscache_kill_object);
+static WORK_STATE(KILL_DEPENDENTS,	"KDEP", fscache_kill_dependents);
+static WORK_STATE(DROP_OBJECT,		"DROP", fscache_drop_object);
+static WORK_STATE(OBJECT_DEAD,		"DEAD", (void*)2UL);
+
+static WAIT_STATE(WAIT_FOR_INIT,	"?INI",
+		  TRANSIT_TO(INIT_OBJECT,	1 << FSCACHE_OBJECT_EV_NEW_CHILD));
+
+static WAIT_STATE(WAIT_FOR_PARENT,	"?PRN",
+		  TRANSIT_TO(PARENT_READY,	1 << FSCACHE_OBJECT_EV_PARENT_READY));
+
+static WAIT_STATE(WAIT_FOR_CMD,		"?CMD",
+		  TRANSIT_TO(INVALIDATE_OBJECT,	1 << FSCACHE_OBJECT_EV_INVALIDATE),
+		  TRANSIT_TO(UPDATE_OBJECT,	1 << FSCACHE_OBJECT_EV_UPDATE),
+		  TRANSIT_TO(JUMPSTART_DEPS,	1 << FSCACHE_OBJECT_EV_NEW_CHILD));
+
+static WAIT_STATE(WAIT_FOR_CLEARANCE,	"?CLR",
+		  TRANSIT_TO(KILL_OBJECT,	1 << FSCACHE_OBJECT_EV_CLEARED));
+
+/*
+ * Out-of-band event transition tables.  These are for handling unexpected
+ * events, such as an I/O error.  If an OOB event occurs, the state machine
+ * clears and disables the event and forces a transition to the nominated work
+ * state (acurrently executing work states will complete first).
+ *
+ * In such a situation, object->state remembers the state the machine should
+ * have been in/gone to and returning NO_TRANSIT returns to that.
+ */
+static const struct fscache_transition fscache_osm_init_oob[] = {
+	   TRANSIT_TO(ABORT_INIT,
+		      (1 << FSCACHE_OBJECT_EV_ERROR) |
+		      (1 << FSCACHE_OBJECT_EV_KILL)),
+	   { 0, NULL }
+};
+
+static const struct fscache_transition fscache_osm_lookup_oob[] = {
+	   TRANSIT_TO(LOOKUP_FAILURE,
+		      (1 << FSCACHE_OBJECT_EV_ERROR) |
+		      (1 << FSCACHE_OBJECT_EV_KILL)),
+	   { 0, NULL }
 };
-EXPORT_SYMBOL(fscache_object_states);
-
-const char fscache_object_states_short[FSCACHE_OBJECT__NSTATES][5] = {
-	[FSCACHE_OBJECT_INIT]		= "INIT",
-	[FSCACHE_OBJECT_LOOKING_UP]	= "LOOK",
-	[FSCACHE_OBJECT_CREATING]	= "CRTN",
-	[FSCACHE_OBJECT_AVAILABLE]	= "AVBL",
-	[FSCACHE_OBJECT_ACTIVE]		= "ACTV",
-	[FSCACHE_OBJECT_INVALIDATING]	= "INVL",
-	[FSCACHE_OBJECT_UPDATING]	= "UPDT",
-	[FSCACHE_OBJECT_DYING]		= "DYNG",
-	[FSCACHE_OBJECT_LC_DYING]	= "LCDY",
-	[FSCACHE_OBJECT_ABORT_INIT]	= "ABTI",
-	[FSCACHE_OBJECT_RELEASING]	= "RELS",
-	[FSCACHE_OBJECT_RECYCLING]	= "RCYC",
-	[FSCACHE_OBJECT_WITHDRAWING]	= "WTHD",
-	[FSCACHE_OBJECT_DEAD]		= "DEAD",
+
+static const struct fscache_transition fscache_osm_run_oob[] = {
+	   TRANSIT_TO(KILL_OBJECT,
+		      (1 << FSCACHE_OBJECT_EV_ERROR) |
+		      (1 << FSCACHE_OBJECT_EV_KILL)),
+	   { 0, NULL }
 };
 
 static int  fscache_get_object(struct fscache_object *);
 static void fscache_put_object(struct fscache_object *);
-static void fscache_initialise_object(struct fscache_object *);
-static void fscache_lookup_object(struct fscache_object *);
-static void fscache_object_available(struct fscache_object *);
-static void fscache_invalidate_object(struct fscache_object *);
-static void fscache_release_object(struct fscache_object *);
-static void fscache_withdraw_object(struct fscache_object *);
-static void fscache_enqueue_dependents(struct fscache_object *);
+static bool fscache_enqueue_dependents(struct fscache_object *, int);
 static void fscache_dequeue_object(struct fscache_object *);
 
 /*
@@ -75,295 +154,116 @@ static inline void fscache_done_parent_op(struct fscache_object *object)
 	       object->debug_id, parent->debug_id, parent->n_ops);
 
 	spin_lock_nested(&parent->lock, 1);
-	parent->n_ops--;
 	parent->n_obj_ops--;
+	parent->n_ops--;
 	if (parent->n_ops == 0)
 		fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
 	spin_unlock(&parent->lock);
 }
 
 /*
- * Notify netfs of invalidation completion.
+ * Object state machine dispatcher.
  */
-static inline void fscache_invalidation_complete(struct fscache_cookie *cookie)
+static void fscache_object_sm_dispatcher(struct fscache_object *object)
 {
-	if (test_and_clear_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags))
-		wake_up_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING);
-}
-
-/*
- * process events that have been sent to an object's state machine
- * - initiates parent lookup
- * - does object lookup
- * - does object creation
- * - does object recycling and retirement
- * - does object withdrawal
- */
-static void fscache_object_state_machine(struct fscache_object *object)
-{
-	enum fscache_object_state new_state;
-	struct fscache_cookie *cookie;
-	int event;
+	const struct fscache_transition *t;
+	const struct fscache_state *state, *new_state;
+	unsigned long events, event_mask;
+	int event = -1;
 
 	ASSERT(object != NULL);
 
 	_enter("{OBJ%x,%s,%lx}",
-	       object->debug_id, fscache_object_states[object->state],
-	       object->events);
-
-	switch (object->state) {
-		/* wait for the parent object to become ready */
-	case FSCACHE_OBJECT_INIT:
-		object->event_mask =
-			FSCACHE_OBJECT_EVENTS_MASK &
-			~(1 << FSCACHE_OBJECT_EV_CLEARED);
-		fscache_initialise_object(object);
-		goto done;
-
-		/* look up the object metadata on disk */
-	case FSCACHE_OBJECT_LOOKING_UP:
-		fscache_lookup_object(object);
-		goto lookup_transit;
-
-		/* create the object metadata on disk */
-	case FSCACHE_OBJECT_CREATING:
-		fscache_lookup_object(object);
-		goto lookup_transit;
-
-		/* handle an object becoming available; start pending
-		 * operations and queue dependent operations for processing */
-	case FSCACHE_OBJECT_AVAILABLE:
-		fscache_object_available(object);
-		goto active_transit;
-
-		/* normal running state */
-	case FSCACHE_OBJECT_ACTIVE:
-		goto active_transit;
-
-		/* Invalidate an object on disk */
-	case FSCACHE_OBJECT_INVALIDATING:
-		clear_bit(FSCACHE_OBJECT_EV_INVALIDATE, &object->events);
-		fscache_stat(&fscache_n_invalidates_run);
-		fscache_stat(&fscache_n_cop_invalidate_object);
-		fscache_invalidate_object(object);
-		fscache_stat_d(&fscache_n_cop_invalidate_object);
-		fscache_raise_event(object, FSCACHE_OBJECT_EV_UPDATE);
-		goto active_transit;
-
-		/* update the object metadata on disk */
-	case FSCACHE_OBJECT_UPDATING:
-		clear_bit(FSCACHE_OBJECT_EV_UPDATE, &object->events);
-		fscache_stat(&fscache_n_updates_run);
-		fscache_stat(&fscache_n_cop_update_object);
-		object->cache->ops->update_object(object);
-		fscache_stat_d(&fscache_n_cop_update_object);
-		goto active_transit;
-
-		/* handle an object dying during lookup or creation */
-	case FSCACHE_OBJECT_LC_DYING:
-		object->event_mask &= ~(1 << FSCACHE_OBJECT_EV_UPDATE);
-		fscache_stat(&fscache_n_cop_lookup_complete);
-		object->cache->ops->lookup_complete(object);
-		fscache_stat_d(&fscache_n_cop_lookup_complete);
-
-		spin_lock(&object->lock);
-		object->state = FSCACHE_OBJECT_DYING;
-		cookie = object->cookie;
-		if (cookie) {
-			if (test_and_clear_bit(FSCACHE_COOKIE_LOOKING_UP,
-					       &cookie->flags))
-				wake_up_bit(&cookie->flags,
-					    FSCACHE_COOKIE_LOOKING_UP);
-			if (test_and_clear_bit(FSCACHE_COOKIE_CREATING,
-					       &cookie->flags))
-				wake_up_bit(&cookie->flags,
-					    FSCACHE_COOKIE_CREATING);
+	       object->debug_id, object->state->name, object->events);
+
+	event_mask = object->event_mask;
+restart:
+	object->event_mask = 0; /* Mask normal event handling */
+	state = object->state;
+restart_masked:
+	events = object->events;
+
+	/* Handle any out-of-band events (typically an error) */
+	if (events & object->oob_event_mask) {
+		_debug("{OBJ%x} oob %lx",
+		       object->debug_id, events & object->oob_event_mask);
+		for (t = object->oob_table; t->events; t++) {
+			if (events & t->events) {
+				state = t->transit_to;
+				ASSERT(state->work != NULL);
+				event = fls(events & t->events) - 1;
+				__clear_bit(event, &object->oob_event_mask);
+				clear_bit(event, &object->events);
+				goto execute_work_state;
+			}
 		}
-		spin_unlock(&object->lock);
+	}
 
-		fscache_done_parent_op(object);
+	/* Wait states are just transition tables */
+	if (!state->work) {
+		if (events & event_mask) {
+			for (t = state->transitions; t->events; t++) {
+				if (events & t->events) {
+					new_state = t->transit_to;
+					event = fls(events & t->events) - 1;
+					clear_bit(event, &object->events);
+					_debug("{OBJ%x} ev %d: %s -> %s",
+					       object->debug_id, event,
+					       state->name, new_state->name);
+					object->state = state = new_state;
+					goto execute_work_state;
+				}
+			}
 
-		/* wait for completion of all active operations on this object
-		 * and the death of all child objects of this object */
-	case FSCACHE_OBJECT_DYING:
-	dying:
-		clear_bit(FSCACHE_OBJECT_EV_CLEARED, &object->events);
-		spin_lock(&object->lock);
-		_debug("dying OBJ%x {%d,%d}",
-		       object->debug_id, object->n_ops, object->n_children);
-		if (object->n_ops == 0 && object->n_children == 0) {
-			object->event_mask &=
-				~(1 << FSCACHE_OBJECT_EV_CLEARED);
-			object->event_mask |=
-				(1 << FSCACHE_OBJECT_EV_WITHDRAW) |
-				(1 << FSCACHE_OBJECT_EV_RETIRE) |
-				(1 << FSCACHE_OBJECT_EV_RELEASE) |
-				(1 << FSCACHE_OBJECT_EV_ERROR);
-		} else {
-			object->event_mask &=
-				~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
-				  (1 << FSCACHE_OBJECT_EV_RETIRE) |
-				  (1 << FSCACHE_OBJECT_EV_RELEASE) |
-				  (1 << FSCACHE_OBJECT_EV_ERROR));
-			object->event_mask |=
-				1 << FSCACHE_OBJECT_EV_CLEARED;
+			/* The event mask didn't include all the tabled bits */
+			BUG();
 		}
-		spin_unlock(&object->lock);
-		fscache_enqueue_dependents(object);
-		fscache_start_operations(object);
-		goto terminal_transit;
-
-		/* handle an abort during initialisation */
-	case FSCACHE_OBJECT_ABORT_INIT:
-		_debug("handle abort init %lx", object->events);
-		object->event_mask &= ~(1 << FSCACHE_OBJECT_EV_UPDATE);
-
-		spin_lock(&object->lock);
-		fscache_dequeue_object(object);
-
-		object->state = FSCACHE_OBJECT_DYING;
-		if (test_and_clear_bit(FSCACHE_COOKIE_CREATING,
-				       &object->cookie->flags))
-			wake_up_bit(&object->cookie->flags,
-				    FSCACHE_COOKIE_CREATING);
-		spin_unlock(&object->lock);
-		goto dying;
-
-		/* handle the netfs releasing an object and possibly marking it
-		 * obsolete too */
-	case FSCACHE_OBJECT_RELEASING:
-	case FSCACHE_OBJECT_RECYCLING:
-		object->event_mask &=
-			~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
-			  (1 << FSCACHE_OBJECT_EV_RETIRE) |
-			  (1 << FSCACHE_OBJECT_EV_RELEASE) |
-			  (1 << FSCACHE_OBJECT_EV_ERROR));
-		fscache_release_object(object);
-		spin_lock(&object->lock);
-		object->state = FSCACHE_OBJECT_DEAD;
-		spin_unlock(&object->lock);
-		fscache_stat(&fscache_n_object_dead);
-		goto terminal_transit;
-
-		/* handle the parent cache of this object being withdrawn from
-		 * active service */
-	case FSCACHE_OBJECT_WITHDRAWING:
-		object->event_mask &=
-			~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
-			  (1 << FSCACHE_OBJECT_EV_RETIRE) |
-			  (1 << FSCACHE_OBJECT_EV_RELEASE) |
-			  (1 << FSCACHE_OBJECT_EV_ERROR));
-		fscache_withdraw_object(object);
-		spin_lock(&object->lock);
-		object->state = FSCACHE_OBJECT_DEAD;
-		spin_unlock(&object->lock);
-		fscache_stat(&fscache_n_object_dead);
-		goto terminal_transit;
-
-		/* complain about the object being woken up once it is
-		 * deceased */
-	case FSCACHE_OBJECT_DEAD:
-		printk(KERN_ERR "FS-Cache:"
-		       " Unexpected event in dead state %lx\n",
-		       object->events & object->event_mask);
-		BUG();
-
-	default:
-		printk(KERN_ERR "FS-Cache: Unknown object state %u\n",
-		       object->state);
-		BUG();
-	}
-
-	/* determine the transition from a lookup state */
-lookup_transit:
-	event = fls(object->events & object->event_mask) - 1;
-	switch (event) {
-	case FSCACHE_OBJECT_EV_WITHDRAW:
-	case FSCACHE_OBJECT_EV_RETIRE:
-	case FSCACHE_OBJECT_EV_RELEASE:
-	case FSCACHE_OBJECT_EV_ERROR:
-		new_state = FSCACHE_OBJECT_LC_DYING;
-		goto change_state;
-	case FSCACHE_OBJECT_EV_INVALIDATE:
-		new_state = FSCACHE_OBJECT_INVALIDATING;
-		goto change_state;
-	case FSCACHE_OBJECT_EV_REQUEUE:
-		goto done;
-	case -1:
-		goto done; /* sleep until event */
-	default:
-		goto unsupported_event;
+		/* Randomly woke up */
+		goto unmask_events;
 	}
 
-	/* determine the transition from an active state */
-active_transit:
-	event = fls(object->events & object->event_mask) - 1;
-	switch (event) {
-	case FSCACHE_OBJECT_EV_WITHDRAW:
-	case FSCACHE_OBJECT_EV_RETIRE:
-	case FSCACHE_OBJECT_EV_RELEASE:
-	case FSCACHE_OBJECT_EV_ERROR:
-		new_state = FSCACHE_OBJECT_DYING;
-		goto change_state;
-	case FSCACHE_OBJECT_EV_INVALIDATE:
-		new_state = FSCACHE_OBJECT_INVALIDATING;
-		goto change_state;
-	case FSCACHE_OBJECT_EV_UPDATE:
-		new_state = FSCACHE_OBJECT_UPDATING;
-		goto change_state;
-	case -1:
-		new_state = FSCACHE_OBJECT_ACTIVE;
-		goto change_state; /* sleep until event */
-	default:
-		goto unsupported_event;
-	}
+execute_work_state:
+	_debug("{OBJ%x} exec %s", object->debug_id, state->name);
 
-	/* determine the transition from a terminal state */
-terminal_transit:
-	event = fls(object->events & object->event_mask) - 1;
-	switch (event) {
-	case FSCACHE_OBJECT_EV_WITHDRAW:
-		new_state = FSCACHE_OBJECT_WITHDRAWING;
-		goto change_state;
-	case FSCACHE_OBJECT_EV_RETIRE:
-		new_state = FSCACHE_OBJECT_RECYCLING;
-		goto change_state;
-	case FSCACHE_OBJECT_EV_RELEASE:
-		new_state = FSCACHE_OBJECT_RELEASING;
-		goto change_state;
-	case FSCACHE_OBJECT_EV_ERROR:
-		new_state = FSCACHE_OBJECT_WITHDRAWING;
-		goto change_state;
-	case FSCACHE_OBJECT_EV_CLEARED:
-		new_state = FSCACHE_OBJECT_DYING;
-		goto change_state;
-	case -1:
-		goto done; /* sleep until event */
-	default:
-		goto unsupported_event;
+	new_state = state->work(object, event);
+	event = -1;
+	if (new_state == NO_TRANSIT) {
+		_debug("{OBJ%x} %s notrans", object->debug_id, state->name);
+		fscache_enqueue_object(object);
+		event_mask = object->oob_event_mask;
+		goto unmask_events;
 	}
 
-change_state:
-	spin_lock(&object->lock);
-	object->state = new_state;
-	spin_unlock(&object->lock);
+	_debug("{OBJ%x} %s -> %s",
+	       object->debug_id, state->name, new_state->name);
+	object->state = state = new_state;
 
-done:
-	_leave(" [->%s]", fscache_object_states[object->state]);
-	return;
+	if (state->work) {
+		if (unlikely(state->work == ((void *)2UL))) {
+			_leave(" [dead]");
+			return;
+		}
+		goto restart_masked;
+	}
 
-unsupported_event:
-	printk(KERN_ERR "FS-Cache:"
-	       " Unsupported event %d [%lx/%lx] in state %s\n",
-	       event, object->events, object->event_mask,
-	       fscache_object_states[object->state]);
-	BUG();
+	/* Transited to wait state */
+	event_mask = object->oob_event_mask;
+	for (t = state->transitions; t->events; t++)
+		event_mask |= t->events;
+
+unmask_events:
+	object->event_mask = event_mask;
+	smp_mb();
+	events = object->events;
+	if (events & event_mask)
+		goto restart;
+	_leave(" [msk %lx]", event_mask);
 }
 
 /*
  * execute an object
  */
-void fscache_object_work_func(struct work_struct *work)
+static void fscache_object_work_func(struct work_struct *work)
 {
 	struct fscache_object *object =
 		container_of(work, struct fscache_object, work);
@@ -372,14 +272,70 @@ void fscache_object_work_func(struct work_struct *work)
 	_enter("{OBJ%x}", object->debug_id);
 
 	start = jiffies;
-	fscache_object_state_machine(object);
+	fscache_object_sm_dispatcher(object);
 	fscache_hist(fscache_objs_histogram, start);
-	if (object->events & object->event_mask)
-		fscache_enqueue_object(object);
-	clear_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 	fscache_put_object(object);
 }
-EXPORT_SYMBOL(fscache_object_work_func);
+
+/**
+ * fscache_object_init - Initialise a cache object description
+ * @object: Object description
+ * @cookie: Cookie object will be attached to
+ * @cache: Cache in which backing object will be found
+ *
+ * Initialise a cache object description to its basic values.
+ *
+ * See Documentation/filesystems/caching/backend-api.txt for a complete
+ * description.
+ */
+void fscache_object_init(struct fscache_object *object,
+			 struct fscache_cookie *cookie,
+			 struct fscache_cache *cache)
+{
+	const struct fscache_transition *t;
+
+	atomic_inc(&cache->object_count);
+
+	object->state = STATE(WAIT_FOR_INIT);
+	object->oob_table = fscache_osm_init_oob;
+	object->flags = 1 << FSCACHE_OBJECT_IS_LIVE;
+	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 = 0;
+	object->store_limit = 0;
+	object->store_limit_l = 0;
+	object->cache = cache;
+	object->cookie = cookie;
+	object->parent = NULL;
+
+	object->oob_event_mask = 0;
+	for (t = object->oob_table; t->events; t++)
+		object->oob_event_mask |= t->events;
+	object->event_mask = object->oob_event_mask;
+	for (t = object->state->transitions; t->events; t++)
+		object->event_mask |= t->events;
+}
+EXPORT_SYMBOL(fscache_object_init);
+
+/*
+ * Abort object initialisation before we start it.
+ */
+static const struct fscache_state *fscache_abort_initialisation(struct fscache_object *object,
+								int event)
+{
+	_enter("{OBJ%x},%d", object->debug_id, event);
+
+	object->oob_event_mask = 0;
+	fscache_dequeue_object(object);
+	return transit_to(KILL_OBJECT);
+}
 
 /*
  * initialise an object
@@ -387,130 +343,136 @@ EXPORT_SYMBOL(fscache_object_work_func);
  *   immediately to do a creation
  * - we may need to start the process of creating a parent and we need to wait
  *   for the parent's lookup and creation to complete if it's not there yet
- * - an object's cookie is pinned until we clear FSCACHE_COOKIE_CREATING on the
- *   leaf-most cookies of the object and all its children
  */
-static void fscache_initialise_object(struct fscache_object *object)
+static const struct fscache_state *fscache_initialise_object(struct fscache_object *object,
+							     int event)
 {
 	struct fscache_object *parent;
+	bool success;
 
-	_enter("");
-	ASSERT(object->cookie != NULL);
-	ASSERT(object->cookie->parent != NULL);
-
-	if (object->events & ((1 << FSCACHE_OBJECT_EV_ERROR) |
-			      (1 << FSCACHE_OBJECT_EV_RELEASE) |
-			      (1 << FSCACHE_OBJECT_EV_RETIRE) |
-			      (1 << FSCACHE_OBJECT_EV_WITHDRAW))) {
-		_debug("abort init %lx", object->events);
-		spin_lock(&object->lock);
-		object->state = FSCACHE_OBJECT_ABORT_INIT;
-		spin_unlock(&object->lock);
-		return;
-	}
+	_enter("{OBJ%x},%d", object->debug_id, event);
 
-	spin_lock(&object->cookie->lock);
-	spin_lock_nested(&object->cookie->parent->lock, 1);
+	ASSERT(list_empty(&object->dep_link));
 
 	parent = object->parent;
 	if (!parent) {
-		_debug("no parent");
-		set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
-	} else {
-		spin_lock(&object->lock);
-		spin_lock_nested(&parent->lock, 1);
-		_debug("parent %s", fscache_object_states[parent->state]);
-
-		if (parent->state >= FSCACHE_OBJECT_DYING) {
-			_debug("bad parent");
-			set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
-		} else if (parent->state < FSCACHE_OBJECT_AVAILABLE) {
-			_debug("wait");
-
-			/* we may get woken up in this state by child objects
-			 * binding on to us, so we need to make sure we don't
-			 * add ourself to the list multiple times */
-			if (list_empty(&object->dep_link)) {
-				fscache_stat(&fscache_n_cop_grab_object);
-				object->cache->ops->grab_object(object);
-				fscache_stat_d(&fscache_n_cop_grab_object);
-				list_add(&object->dep_link,
-					 &parent->dependents);
-
-				/* fscache_acquire_non_index_cookie() uses this
-				 * to wake the chain up */
-				if (parent->state == FSCACHE_OBJECT_INIT)
-					fscache_enqueue_object(parent);
-			}
-		} else {
-			_debug("go");
-			parent->n_ops++;
-			parent->n_obj_ops++;
-			object->lookup_jif = jiffies;
-			object->state = FSCACHE_OBJECT_LOOKING_UP;
-			set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
-		}
+		_leave(" [no parent]");
+		return transit_to(DROP_OBJECT);
+	}
 
-		spin_unlock(&parent->lock);
-		spin_unlock(&object->lock);
+	_debug("parent: %s of:%lx", parent->state->name, parent->flags);
+
+	if (fscache_object_is_dying(parent)) {
+		_leave(" [bad parent]");
+		return transit_to(DROP_OBJECT);
 	}
 
-	spin_unlock(&object->cookie->parent->lock);
-	spin_unlock(&object->cookie->lock);
+	if (fscache_object_is_available(parent)) {
+		_leave(" [ready]");
+		return transit_to(PARENT_READY);
+	}
+
+	_debug("wait");
+
+	spin_lock(&parent->lock);
+	fscache_stat(&fscache_n_cop_grab_object);
+	success = false;
+	if (fscache_object_is_live(parent) &&
+	    object->cache->ops->grab_object(object)) {
+		list_add(&object->dep_link, &parent->dependents);
+		success = true;
+	}
+	fscache_stat_d(&fscache_n_cop_grab_object);
+	spin_unlock(&parent->lock);
+	if (!success) {
+		_leave(" [grab failed]");
+		return transit_to(DROP_OBJECT);
+	}
+
+	/* fscache_acquire_non_index_cookie() uses this
+	 * to wake the chain up */
+	fscache_raise_event(parent, FSCACHE_OBJECT_EV_NEW_CHILD);
+	_leave(" [wait]");
+	return transit_to(WAIT_FOR_PARENT);
+}
+
+/*
+ * Once the parent object is ready, we should kick off our lookup op.
+ */
+static const struct fscache_state *fscache_parent_ready(struct fscache_object *object,
+							int event)
+{
+	struct fscache_object *parent = object->parent;
+
+	_enter("{OBJ%x},%d", object->debug_id, event);
+
+	ASSERT(parent != NULL);
+
+	spin_lock(&parent->lock);
+	parent->n_ops++;
+	parent->n_obj_ops++;
+	object->lookup_jif = jiffies;
+	spin_unlock(&parent->lock);
+
 	_leave("");
+	return transit_to(LOOK_UP_OBJECT);
 }
 
 /*
  * look an object up in the cache from which it was allocated
  * - we hold an "access lock" on the parent object, so the parent object cannot
  *   be withdrawn by either party till we've finished
- * - an object's cookie is pinned until we clear FSCACHE_COOKIE_CREATING on the
- *   leaf-most cookies of the object and all its children
  */
-static void fscache_lookup_object(struct fscache_object *object)
+static const struct fscache_state *fscache_look_up_object(struct fscache_object *object,
+							  int event)
 {
 	struct fscache_cookie *cookie = object->cookie;
-	struct fscache_object *parent;
+	struct fscache_object *parent = object->parent;
 	int ret;
 
-	_enter("");
+	_enter("{OBJ%x},%d", object->debug_id, event);
+
+	object->oob_table = fscache_osm_lookup_oob;
 
-	parent = object->parent;
 	ASSERT(parent != NULL);
 	ASSERTCMP(parent->n_ops, >, 0);
 	ASSERTCMP(parent->n_obj_ops, >, 0);
 
 	/* make sure the parent is still available */
-	ASSERTCMP(parent->state, >=, FSCACHE_OBJECT_AVAILABLE);
-
-	if (parent->state >= FSCACHE_OBJECT_DYING ||
-	    test_bit(FSCACHE_IOERROR, &object->cache->flags)) {
-		_debug("unavailable");
-		set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
-		_leave("");
-		return;
+	ASSERT(fscache_object_is_available(parent));
+
+	if (fscache_object_is_dying(parent) ||
+	    test_bit(FSCACHE_IOERROR, &object->cache->flags) ||
+	    !fscache_use_cookie(object)) {
+		_leave(" [unavailable]");
+		return transit_to(LOOKUP_FAILURE);
 	}
 
-	_debug("LOOKUP \"%s/%s\" in \"%s\"",
-	       parent->cookie->def->name, cookie->def->name,
-	       object->cache->tag->name);
+	_debug("LOOKUP \"%s\" in \"%s\"",
+	       cookie->def->name, object->cache->tag->name);
 
 	fscache_stat(&fscache_n_object_lookups);
 	fscache_stat(&fscache_n_cop_lookup_object);
 	ret = object->cache->ops->lookup_object(object);
 	fscache_stat_d(&fscache_n_cop_lookup_object);
 
-	if (test_bit(FSCACHE_OBJECT_EV_ERROR, &object->events))
-		set_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
+	fscache_unuse_cookie(object);
 
 	if (ret == -ETIMEDOUT) {
 		/* probably stuck behind another object, so move this one to
 		 * the back of the queue */
 		fscache_stat(&fscache_n_object_lookups_timed_out);
-		set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
+		_leave(" [timeout]");
+		return NO_TRANSIT;
 	}
 
-	_leave("");
+	if (ret < 0) {
+		_leave(" [error]");
+		return transit_to(LOOKUP_FAILURE);
+	}
+
+	_leave(" [ok]");
+	return transit_to(OBJECT_AVAILABLE);
 }
 
 /**
@@ -524,32 +486,20 @@ void fscache_object_lookup_negative(struct fscache_object *object)
 {
 	struct fscache_cookie *cookie = object->cookie;
 
-	_enter("{OBJ%x,%s}",
-	       object->debug_id, fscache_object_states[object->state]);
+	_enter("{OBJ%x,%s}", object->debug_id, object->state->name);
 
-	spin_lock(&object->lock);
-	if (object->state == FSCACHE_OBJECT_LOOKING_UP) {
+	if (!test_and_set_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
 		fscache_stat(&fscache_n_object_lookups_negative);
 
-		/* transit here to allow write requests to begin stacking up
-		 * and read requests to begin returning ENODATA */
-		object->state = FSCACHE_OBJECT_CREATING;
-		spin_unlock(&object->lock);
-
-		set_bit(FSCACHE_COOKIE_PENDING_FILL, &cookie->flags);
+		/* Allow write requests to begin stacking up and read requests to begin
+		 * returning ENODATA.
+		 */
 		set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 
 		_debug("wake up lookup %p", &cookie->flags);
-		smp_mb__before_clear_bit();
-		clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
-		smp_mb__after_clear_bit();
+		clear_bit_unlock(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
 		wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
-		set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
-	} else {
-		ASSERTCMP(object->state, ==, FSCACHE_OBJECT_CREATING);
-		spin_unlock(&object->lock);
 	}
-
 	_leave("");
 }
 EXPORT_SYMBOL(fscache_object_lookup_negative);
@@ -568,38 +518,26 @@ void fscache_obtained_object(struct fscache_object *object)
 {
 	struct fscache_cookie *cookie = object->cookie;
 
-	_enter("{OBJ%x,%s}",
-	       object->debug_id, fscache_object_states[object->state]);
+	_enter("{OBJ%x,%s}", object->debug_id, object->state->name);
 
 	/* if we were still looking up, then we must have a positive lookup
 	 * result, in which case there may be data available */
-	spin_lock(&object->lock);
-	if (object->state == FSCACHE_OBJECT_LOOKING_UP) {
+	if (!test_and_set_bit(FSCACHE_OBJECT_IS_LOOKED_UP, &object->flags)) {
 		fscache_stat(&fscache_n_object_lookups_positive);
 
-		clear_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
+		/* We do (presumably) have data */
+		clear_bit_unlock(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
 
-		object->state = FSCACHE_OBJECT_AVAILABLE;
-		spin_unlock(&object->lock);
-
-		smp_mb__before_clear_bit();
-		clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
-		smp_mb__after_clear_bit();
+		/* Allow write requests to begin stacking up and read requests
+		 * to begin shovelling data.
+		 */
+		clear_bit_unlock(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
 		wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
-		set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
 	} else {
-		ASSERTCMP(object->state, ==, FSCACHE_OBJECT_CREATING);
 		fscache_stat(&fscache_n_object_created);
-
-		object->state = FSCACHE_OBJECT_AVAILABLE;
-		spin_unlock(&object->lock);
-		set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
-		smp_wmb();
 	}
 
-	if (test_and_clear_bit(FSCACHE_COOKIE_CREATING, &cookie->flags))
-		wake_up_bit(&cookie->flags, FSCACHE_COOKIE_CREATING);
-
+	set_bit(FSCACHE_OBJECT_IS_AVAILABLE, &object->flags);
 	_leave("");
 }
 EXPORT_SYMBOL(fscache_obtained_object);
@@ -607,15 +545,14 @@ EXPORT_SYMBOL(fscache_obtained_object);
 /*
  * handle an object that has just become available
  */
-static void fscache_object_available(struct fscache_object *object)
+static const struct fscache_state *fscache_object_available(struct fscache_object *object,
+							    int event)
 {
-	_enter("{OBJ%x}", object->debug_id);
+	_enter("{OBJ%x},%d", object->debug_id, event);
 
-	spin_lock(&object->lock);
+	object->oob_table = fscache_osm_run_oob;
 
-	if (object->cookie &&
-	    test_and_clear_bit(FSCACHE_COOKIE_CREATING, &object->cookie->flags))
-		wake_up_bit(&object->cookie->flags, FSCACHE_COOKIE_CREATING);
+	spin_lock(&object->lock);
 
 	fscache_done_parent_op(object);
 	if (object->n_in_progress == 0) {
@@ -631,130 +568,158 @@ static void fscache_object_available(struct fscache_object *object)
 	fscache_stat(&fscache_n_cop_lookup_complete);
 	object->cache->ops->lookup_complete(object);
 	fscache_stat_d(&fscache_n_cop_lookup_complete);
-	fscache_enqueue_dependents(object);
 
 	fscache_hist(fscache_obj_instantiate_histogram, object->lookup_jif);
 	fscache_stat(&fscache_n_object_avail);
 
 	_leave("");
+	return transit_to(JUMPSTART_DEPS);
 }
 
 /*
- * drop an object's attachments
+ * Wake up this object's dependent objects now that we've become available.
  */
-static void fscache_drop_object(struct fscache_object *object)
+static const struct fscache_state *fscache_jumpstart_dependents(struct fscache_object *object,
+								int event)
 {
-	struct fscache_object *parent = object->parent;
-	struct fscache_cache *cache = object->cache;
+	_enter("{OBJ%x},%d", object->debug_id, event);
 
-	_enter("{OBJ%x,%d}", object->debug_id, object->n_children);
+	if (!fscache_enqueue_dependents(object, FSCACHE_OBJECT_EV_PARENT_READY))
+		return NO_TRANSIT; /* Not finished; requeue */
+	return transit_to(WAIT_FOR_CMD);
+}
 
-	ASSERTCMP(object->cookie, ==, NULL);
-	ASSERT(hlist_unhashed(&object->cookie_link));
+/*
+ * Handle lookup or creation failute.
+ */
+static const struct fscache_state *fscache_lookup_failure(struct fscache_object *object,
+							  int event)
+{
+	struct fscache_cookie *cookie;
 
-	spin_lock(&cache->object_list_lock);
-	list_del_init(&object->cache_link);
-	spin_unlock(&cache->object_list_lock);
+	_enter("{OBJ%x},%d", object->debug_id, event);
 
-	fscache_stat(&fscache_n_cop_drop_object);
-	cache->ops->drop_object(object);
-	fscache_stat_d(&fscache_n_cop_drop_object);
+	object->oob_event_mask = 0;
 
-	if (parent) {
-		_debug("release parent OBJ%x {%d}",
-		       parent->debug_id, parent->n_children);
+	fscache_stat(&fscache_n_cop_lookup_complete);
+	object->cache->ops->lookup_complete(object);
+	fscache_stat_d(&fscache_n_cop_lookup_complete);
 
-		spin_lock(&parent->lock);
-		parent->n_children--;
-		if (parent->n_children == 0)
-			fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
-		spin_unlock(&parent->lock);
-		object->parent = NULL;
+	cookie = object->cookie;
+	set_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
+	if (test_and_clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags))
+		wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
+
+	fscache_done_parent_op(object);
+	return transit_to(KILL_OBJECT);
+}
+
+/*
+ * Wait for completion of all active operations on this object and the death of
+ * all child objects of this object.
+ */
+static const struct fscache_state *fscache_kill_object(struct fscache_object *object,
+						       int event)
+{
+	_enter("{OBJ%x,%d,%d},%d",
+	       object->debug_id, object->n_ops, object->n_children, event);
+
+	clear_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
+	object->oob_event_mask = 0;
+
+	if (list_empty(&object->dependents) &&
+	    object->n_ops == 0 &&
+	    object->n_children == 0)
+		return transit_to(DROP_OBJECT);
+
+	if (object->n_in_progress == 0) {
+		spin_lock(&object->lock);
+		if (object->n_ops > 0 && object->n_in_progress == 0)
+			fscache_start_operations(object);
+		spin_unlock(&object->lock);
 	}
 
-	/* this just shifts the object release to the work processor */
-	fscache_put_object(object);
+	if (!list_empty(&object->dependents))
+		return transit_to(KILL_DEPENDENTS);
 
-	_leave("");
+	return transit_to(WAIT_FOR_CLEARANCE);
 }
 
 /*
- * release or recycle an object that the netfs has discarded
+ * Kill dependent objects.
  */
-static void fscache_release_object(struct fscache_object *object)
+static const struct fscache_state *fscache_kill_dependents(struct fscache_object *object,
+							   int event)
 {
-	_enter("");
+	_enter("{OBJ%x},%d", object->debug_id, event);
 
-	fscache_drop_object(object);
+	if (!fscache_enqueue_dependents(object, FSCACHE_OBJECT_EV_KILL))
+		return NO_TRANSIT; /* Not finished */
+	return transit_to(WAIT_FOR_CLEARANCE);
 }
 
 /*
- * withdraw an object from active service
+ * Drop an object's attachments
  */
-static void fscache_withdraw_object(struct fscache_object *object)
+static const struct fscache_state *fscache_drop_object(struct fscache_object *object,
+						       int event)
 {
-	struct fscache_cookie *cookie;
-	bool detached;
+	struct fscache_object *parent = object->parent;
+	struct fscache_cookie *cookie = object->cookie;
+	struct fscache_cache *cache = object->cache;
+	bool awaken = false;
 
-	_enter("");
+	_enter("{OBJ%x,%d},%d", object->debug_id, object->n_children, event);
 
-	spin_lock(&object->lock);
-	cookie = object->cookie;
-	if (cookie) {
-		/* need to get the cookie lock before the object lock, starting
-		 * from the object pointer */
-		atomic_inc(&cookie->usage);
-		spin_unlock(&object->lock);
+	ASSERT(cookie != NULL);
+	ASSERT(!hlist_unhashed(&object->cookie_link));
 
-		detached = false;
-		spin_lock(&cookie->lock);
-		spin_lock(&object->lock);
+	/* Make sure the cookie no longer points here and that the netfs isn't
+	 * waiting for us.
+	 */
+	spin_lock(&cookie->lock);
+	hlist_del_init(&object->cookie_link);
+	if (test_and_clear_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags))
+		awaken = true;
+	spin_unlock(&cookie->lock);
 
-		if (object->cookie == cookie) {
-			hlist_del_init(&object->cookie_link);
-			object->cookie = NULL;
-			fscache_invalidation_complete(cookie);
-			detached = true;
-		}
-		spin_unlock(&cookie->lock);
-		fscache_cookie_put(cookie);
-		if (detached)
-			fscache_cookie_put(cookie);
-	}
+	if (awaken)
+		wake_up_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING);
 
+	/* Prevent a race with our last child, which has to signal EV_CLEARED
+	 * before dropping our spinlock.
+	 */
+	spin_lock(&object->lock);
 	spin_unlock(&object->lock);
 
-	fscache_drop_object(object);
-}
+	/* Discard from the cache's collection of objects */
+	spin_lock(&cache->object_list_lock);
+	list_del_init(&object->cache_link);
+	spin_unlock(&cache->object_list_lock);
 
-/*
- * withdraw an object from active service at the behest of the cache
- * - need break the links to a cached object cookie
- * - called under two situations:
- *   (1) recycler decides to reclaim an in-use object
- *   (2) a cache is unmounted
- * - have to take care as the cookie can be being relinquished by the netfs
- *   simultaneously
- * - the object is pinned by the caller holding a refcount on it
- */
-void fscache_withdrawing_object(struct fscache_cache *cache,
-				struct fscache_object *object)
-{
-	bool enqueue = false;
+	fscache_stat(&fscache_n_cop_drop_object);
+	cache->ops->drop_object(object);
+	fscache_stat_d(&fscache_n_cop_drop_object);
 
-	_enter(",OBJ%x", object->debug_id);
+	/* The parent object wants to know when all it dependents have gone */
+	if (parent) {
+		_debug("release parent OBJ%x {%d}",
+		       parent->debug_id, parent->n_children);
 
-	spin_lock(&object->lock);
-	if (object->state < FSCACHE_OBJECT_WITHDRAWING) {
-		object->state = FSCACHE_OBJECT_WITHDRAWING;
-		enqueue = true;
+		spin_lock(&parent->lock);
+		parent->n_children--;
+		if (parent->n_children == 0)
+			fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
+		spin_unlock(&parent->lock);
+		object->parent = NULL;
 	}
-	spin_unlock(&object->lock);
 
-	if (enqueue)
-		fscache_enqueue_object(object);
+	/* this just shifts the object release to the work processor */
+	fscache_put_object(object);
+	fscache_stat(&fscache_n_object_dead);
 
 	_leave("");
+	return transit_to(OBJECT_DEAD);
 }
 
 /*
@@ -771,7 +736,7 @@ static int fscache_get_object(struct fscache_object *object)
 }
 
 /*
- * discard a ref on a work item
+ * Discard a ref on an object
  */
 static void fscache_put_object(struct fscache_object *object)
 {
@@ -780,6 +745,22 @@ static void fscache_put_object(struct fscache_object *object)
 	fscache_stat_d(&fscache_n_cop_put_object);
 }
 
+/**
+ * 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.
+ */
+void fscache_object_destroy(struct fscache_object *object)
+{
+	fscache_objlist_remove(object);
+
+	/* We can get rid of the cookie now */
+	fscache_cookie_put(object->cookie);
+	object->cookie = NULL;
+}
+EXPORT_SYMBOL(fscache_object_destroy);
+
 /*
  * enqueue an object for metadata-type processing
  */
@@ -803,7 +784,7 @@ void fscache_enqueue_object(struct fscache_object *object)
 
 /**
  * fscache_object_sleep_till_congested - Sleep until object wq is congested
- * @timoutp: Scheduler sleep timeout
+ * @timeoutp: Scheduler sleep timeout
  *
  * Allow an object handler to sleep until the object workqueue is congested.
  *
@@ -831,18 +812,21 @@ bool fscache_object_sleep_till_congested(signed long *timeoutp)
 EXPORT_SYMBOL_GPL(fscache_object_sleep_till_congested);
 
 /*
- * enqueue the dependents of an object for metadata-type processing
- * - the caller must hold the object's lock
- * - this may cause an already locked object to wind up being processed again
+ * Enqueue the dependents of an object for metadata-type processing.
+ *
+ * If we don't manage to finish the list before the scheduler wants to run
+ * again then return false immediately.  We return true if the list was
+ * cleared.
  */
-static void fscache_enqueue_dependents(struct fscache_object *object)
+static bool fscache_enqueue_dependents(struct fscache_object *object, int event)
 {
 	struct fscache_object *dep;
+	bool ret = true;
 
 	_enter("{OBJ%x}", object->debug_id);
 
 	if (list_empty(&object->dependents))
-		return;
+		return true;
 
 	spin_lock(&object->lock);
 
@@ -851,23 +835,23 @@ static void fscache_enqueue_dependents(struct fscache_object *object)
 				 struct fscache_object, dep_link);
 		list_del_init(&dep->dep_link);
 
-
-		/* sort onto appropriate lists */
-		fscache_enqueue_object(dep);
+		fscache_raise_event(dep, event);
 		fscache_put_object(dep);
 
-		if (!list_empty(&object->dependents))
-			cond_resched_lock(&object->lock);
+		if (!list_empty(&object->dependents) && need_resched()) {
+			ret = false;
+			break;
+		}
 	}
 
 	spin_unlock(&object->lock);
+	return ret;
 }
 
 /*
  * remove an object from whatever queue it's waiting on
- * - the caller must hold object->lock
  */
-void fscache_dequeue_object(struct fscache_object *object)
+static void fscache_dequeue_object(struct fscache_object *object)
 {
 	_enter("{OBJ%x}", object->debug_id);
 
@@ -886,7 +870,10 @@ void fscache_dequeue_object(struct fscache_object *object)
  * @data: The auxiliary data for the object
  * @datalen: The size of the auxiliary data
  *
- * This function consults the netfs about the coherency state of an object
+ * This function consults the netfs about the coherency state of an object.
+ * The caller must be holding a ref on cookie->n_active (held by
+ * fscache_look_up_object() on behalf of the cache backend during object lookup
+ * and creation).
  */
 enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
 					const void *data, uint16_t datalen)
@@ -927,12 +914,23 @@ EXPORT_SYMBOL(fscache_check_aux);
 /*
  * Asynchronously invalidate an object.
  */
-static void fscache_invalidate_object(struct fscache_object *object)
+static const struct fscache_state *_fscache_invalidate_object(struct fscache_object *object,
+							      int event)
 {
 	struct fscache_operation *op;
 	struct fscache_cookie *cookie = object->cookie;
 
-	_enter("{OBJ%x}", object->debug_id);
+	_enter("{OBJ%x},%d", object->debug_id, event);
+
+	/* We're going to need the cookie.  If the cookie is not available then
+	 * retire the object instead.
+	 */
+	if (!fscache_use_cookie(object)) {
+		ASSERT(object->cookie->stores.rnode == NULL);
+		set_bit(FSCACHE_COOKIE_RETIRED, &cookie->flags);
+		_leave(" [no cookie]");
+		return transit_to(KILL_OBJECT);
+	}
 
 	/* Reject any new read/write ops and abort any that are pending. */
 	fscache_invalidate_writes(cookie);
@@ -941,14 +939,13 @@ static void fscache_invalidate_object(struct fscache_object *object)
 
 	/* Now we have to wait for in-progress reads and writes */
 	op = kzalloc(sizeof(*op), GFP_KERNEL);
-	if (!op) {
-		fscache_raise_event(object, FSCACHE_OBJECT_EV_ERROR);
-		_leave(" [ENOMEM]");
-		return;
-	}
+	if (!op)
+		goto nomem;
 
 	fscache_operation_init(op, object->cache->ops->invalidate_object, NULL);
-	op->flags = FSCACHE_OP_ASYNC | (1 << FSCACHE_OP_EXCLUSIVE);
+	op->flags = FSCACHE_OP_ASYNC |
+		(1 << FSCACHE_OP_EXCLUSIVE) |
+		(1 << FSCACHE_OP_UNUSE_COOKIE);
 
 	spin_lock(&cookie->lock);
 	if (fscache_submit_exclusive_op(object, op) < 0)
@@ -965,13 +962,50 @@ static void fscache_invalidate_object(struct fscache_object *object)
 	/* We can allow read and write requests to come in once again.  They'll
 	 * queue up behind our exclusive invalidation operation.
 	 */
-	fscache_invalidation_complete(cookie);
-	_leave("");
-	return;
+	if (test_and_clear_bit(FSCACHE_COOKIE_INVALIDATING, &cookie->flags))
+		wake_up_bit(&cookie->flags, FSCACHE_COOKIE_INVALIDATING);
+	_leave(" [ok]");
+	return transit_to(UPDATE_OBJECT);
+
+nomem:
+	clear_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
+	fscache_unuse_cookie(object);
+	_leave(" [ENOMEM]");
+	return transit_to(KILL_OBJECT);
 
 submit_op_failed:
+	clear_bit(FSCACHE_OBJECT_IS_LIVE, &object->flags);
 	spin_unlock(&cookie->lock);
 	kfree(op);
-	fscache_raise_event(object, FSCACHE_OBJECT_EV_ERROR);
 	_leave(" [EIO]");
+	return transit_to(KILL_OBJECT);
+}
+
+static const struct fscache_state *fscache_invalidate_object(struct fscache_object *object,
+							     int event)
+{
+	const struct fscache_state *s;
+
+	fscache_stat(&fscache_n_invalidates_run);
+	fscache_stat(&fscache_n_cop_invalidate_object);
+	s = _fscache_invalidate_object(object, event);
+	fscache_stat_d(&fscache_n_cop_invalidate_object);
+	return s;
+}
+
+/*
+ * Asynchronously update an object.
+ */
+static const struct fscache_state *fscache_update_object(struct fscache_object *object,
+							 int event)
+{
+	_enter("{OBJ%x},%d", object->debug_id, event);
+
+	fscache_stat(&fscache_n_updates_run);
+	fscache_stat(&fscache_n_cop_update_object);
+	object->cache->ops->update_object(object);
+	fscache_stat_d(&fscache_n_cop_update_object);
+
+	_leave("");
+	return transit_to(WAIT_FOR_CMD);
 }

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);