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authorJan Kara <jack@suse.cz>2011-05-05 07:59:35 -0400
committerJan Kara <jack@suse.cz>2011-05-17 07:47:42 -0400
commit2842bb20eed2e25cde5114298edc62c8883a1d9a (patch)
treeaf4d60d1e5e922f836ec5de3bc6f433fbb947ef2 /fs
parent4e299c1d9113b5c1c3845c0d4e78d09dd60a4fe8 (diff)
jbd: Fix forever sleeping process in do_get_write_access()
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. CC: stable@kernel.org Reported-by: Tao Ma <boyu.mt@taobao.com> Signed-off-by: Jan Kara <jack@suse.cz>
Diffstat (limited to 'fs')
-rw-r--r--fs/jbd/commit.c9
1 files changed, 7 insertions, 2 deletions
diff --git a/fs/jbd/commit.c b/fs/jbd/commit.c
index 69b180459463..f486ff697781 100644
--- a/fs/jbd/commit.c
+++ b/fs/jbd/commit.c
@@ -722,8 +722,13 @@ wait_for_iobuf:
722 required. */ 722 required. */
723 JBUFFER_TRACE(jh, "file as BJ_Forget"); 723 JBUFFER_TRACE(jh, "file as BJ_Forget");
724 journal_file_buffer(jh, commit_transaction, BJ_Forget); 724 journal_file_buffer(jh, commit_transaction, BJ_Forget);
725 /* Wake up any transactions which were waiting for this 725 /*
726 IO to complete */ 726 * Wake up any transactions which were waiting for this
727 * IO to complete. The barrier must be here so that changes
728 * by journal_file_buffer() take effect before wake_up_bit()
729 * does the waitqueue check.
730 */
731 smp_mb();
727 wake_up_bit(&bh->b_state, BH_Unshadow); 732 wake_up_bit(&bh->b_state, BH_Unshadow);
728 JBUFFER_TRACE(jh, "brelse shadowed buffer"); 733 JBUFFER_TRACE(jh, "brelse shadowed buffer");
729 __brelse(bh); 734 __brelse(bh);