FS-Cache: The object-available state can't rely on the cookie to be available (6897e3df) · Commits · 戴 / test

The object-available state in the object processing state machine (as processed by fscache_object_available()) can't rely on the cookie to be available because the FSCACHE_COOKIE_CREATING bit may have been cleared by fscache_obtained_object() prior to the object being put into the FSCACHE_OBJECT_AVAILABLE state. Clearing the FSCACHE_COOKIE_CREATING bit on a cookie permits __fscache_relinquish_cookie() to proceed and detach the cookie from the object. To deal with this, we don't dereference object->cookie in fscache_object_available() if the object has already been detached. In addition, a couple of assertions are added into fscache_drop_object() to make sure the object is unbound from the cookie before it gets there. Signed-off-by:

David Howells <dhowells@redhat.com>

fs/fscache/object.c

+7 −2

Original line number	Diff line number	Diff line
		@@ -158,7 +158,8 @@ static void fscache_object_state_machine(struct fscache_object *object)

		spin_lock(&object->lock);
		object->state = FSCACHE_OBJECT_DYING;
		if (test_and_clear_bit(FSCACHE_COOKIE_CREATING,
		if (object->cookie &&
		test_and_clear_bit(FSCACHE_COOKIE_CREATING,
		&object->cookie->flags))
		wake_up_bit(&object->cookie->flags,
		FSCACHE_COOKIE_CREATING);
		@@ -594,7 +595,8 @@ static void fscache_object_available(struct fscache_object *object)

		spin_lock(&object->lock);

		if (test_and_clear_bit(FSCACHE_COOKIE_CREATING, &object->cookie->flags))
		if (object->cookie &&
		test_and_clear_bit(FSCACHE_COOKIE_CREATING, &object->cookie->flags))
		wake_up_bit(&object->cookie->flags, FSCACHE_COOKIE_CREATING);

		fscache_done_parent_op(object);
		@@ -631,6 +633,9 @@ static void fscache_drop_object(struct fscache_object *object)

		_enter("{OBJ%x,%d}", object->debug_id, object->n_children);

		ASSERTCMP(object->cookie, ==, NULL);
		ASSERT(hlist_unhashed(&object->cookie_link));

		spin_lock(&cache->object_list_lock);
		list_del_init(&object->cache_link);
		spin_unlock(&cache->object_list_lock);

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