linux-kernel - [PATCH 20/28] FS-Cache: Make sure FSCACHE_COOKIE_LOOKING

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Date:	Thu, 19 Nov 2009 17:22:16 +0000
From:	David Howells <dhowells@...hat.com>
To:	linux-cachefs@...hat.com, nfsv4@...ux-nfs.org,
	linux-kernel@...r.kernel.org
Cc:	dhowells@...hat.com, steved@...hat.com
Subject: [PATCH 20/28] FS-Cache: Make sure FSCACHE_COOKIE_LOOKING_UP cleared
	on lookup failure

We must make sure that FSCACHE_COOKIE_LOOKING_UP is cleared on lookup failure
(if an object reaches the LC_DYING state), and we should clear it before
clearing FSCACHE_COOKIE_CREATING.

If this doesn't happen then fscache_wait_for_deferred_lookup() may hold
allocation and retrieval operations indefinitely until they're interrupted by
signals - which in turn pins the dying object until they go away.

Signed-off-by: David Howells <dhowells@...hat.com>
---

 fs/fscache/object.c |   17 ++++++++++++-----
 1 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/fs/fscache/object.c b/fs/fscache/object.c
index 1a1afa8..74bc562 100644
--- a/fs/fscache/object.c
+++ b/fs/fscache/object.c
@@ -105,6 +105,7 @@ static inline void fscache_done_parent_op(struct fscache_object *object)
 static void fscache_object_state_machine(struct fscache_object *object)
 {
 	enum fscache_object_state new_state;
+	struct fscache_cookie *cookie;
 
 	ASSERT(object != NULL);
 
@@ -158,11 +159,17 @@ static void fscache_object_state_machine(struct fscache_object *object)
 
 		spin_lock(&object->lock);
 		object->state = FSCACHE_OBJECT_DYING;
-		if (object->cookie &&
-		    test_and_clear_bit(FSCACHE_COOKIE_CREATING,
-				       &object->cookie->flags))
-			wake_up_bit(&object->cookie->flags,
-				    FSCACHE_COOKIE_CREATING);
+		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);
+		}
 		spin_unlock(&object->lock);
 
 		fscache_done_parent_op(object);

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