[PATCH] jbd wakeup fix

Processes can sleep in do_get_write_access(), waiting for buffers to be
removed from the BJ_Shadow state.  We did this by doing a wake_up_buffer() in
the commit path and sleeping on the buffer in do_get_write_access().

With the filtered bit-level wakeup code this doesn't work properly any more -
the wake_up_buffer() accidentally wakes up tasks which are sleeping in
lock_buffer() as well.  Those tasks now implicitly assume that the buffer came
unlocked.  Net effect: Bogus I/O errors when reading journal blocks, because
the buffer isn't up to date yet.  Hence the recently spate of journal_bmap()
failure reports.

The patch creates a new jbd-private BH flag purely for this wakeup function.
So a wake_up_bit(..., BH_Unshadow) doesn't wake up someone who is waiting for
a wake_up_bit(BH_Lock).

JBD was the only user of wake_up_buffer(), so remove it altogether.

Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/fs/jbd/commit.c b/fs/jbd/commit.c
index f8a1dea56611..b4d6654ef7f2 100644
--- a/fs/jbd/commit.c
+++ b/fs/jbd/commit.c
@@ -579,7 +579,7 @@ wait_for_iobuf:
 		journal_file_buffer(jh, commit_transaction, BJ_Forget);
 		/* Wake up any transactions which were waiting for this
 		   IO to complete */
-		wake_up_buffer(bh);
+		wake_up_bit(&bh->b_state, BH_Unshadow);
 		JBUFFER_TRACE(jh, "brelse shadowed buffer");
 		__brelse(bh);
 	}