This is a note to let you know that I've just added the patch titled
jbd: Fix forever sleeping process in do_get_write_access()
to the 2.6.33-longterm tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/longterm/longterm-queue-2.6.33.git;a=summary
The filename of the patch is:
jbd-fix-forever-sleeping-process-in-do_get_write_access.patch
and it can be found in the queue-2.6.33 subdirectory.
If you, or anyone else, feels it should not be added to the 2.6.33 longterm
tree,
please let <[email protected]> know about it.
>From 2842bb20eed2e25cde5114298edc62c8883a1d9a Mon Sep 17 00:00:00 2001
From: Jan Kara <[email protected]>
Date: Thu, 5 May 2011 13:59:35 +0200
Subject: jbd: Fix forever sleeping process in do_get_write_access()
From: Jan Kara <[email protected]>
commit 2842bb20eed2e25cde5114298edc62c8883a1d9a upstream.
In do_get_write_access() we wait on BH_Unshadow bit for buffer to get
from shadow state. The waking code in journal_commit_transaction() has
a bug because it does not issue a memory barrier after the buffer is moved
from the shadow state and before wake_up_bit() is called. Thus a waitqueue
check can happen before the buffer is actually moved from the shadow state
and waiting process may never be woken. Fix the problem by issuing proper
barrier.
Reported-by: Tao Ma <[email protected]>
Signed-off-by: Jan Kara <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
fs/jbd/commit.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
--- a/fs/jbd/commit.c
+++ b/fs/jbd/commit.c
@@ -746,8 +746,13 @@ wait_for_iobuf:
required. */
JBUFFER_TRACE(jh, "file as BJ_Forget");
journal_file_buffer(jh, commit_transaction, BJ_Forget);
- /* Wake up any transactions which were waiting for this
- IO to complete */
+ /*
+ * Wake up any transactions which were waiting for this
+ * IO to complete. The barrier must be here so that changes
+ * by journal_file_buffer() take effect before wake_up_bit()
+ * does the waitqueue check.
+ */
+ smp_mb();
wake_up_bit(&bh->b_state, BH_Unshadow);
JBUFFER_TRACE(jh, "brelse shadowed buffer");
__brelse(bh);
Patches currently in longterm-queue-2.6.33 which might be from [email protected] are
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