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| author | Jan Kara <jack@suse.cz> | 2011-05-05 13:59:35 +0200 |
|---|---|---|
| committer | Jan Kara <jack@suse.cz> | 2011-05-17 13:47:42 +0200 |
| commit | 2842bb20eed2e25cde5114298edc62c8883a1d9a (patch) | |
| tree | af4d60d1e5e922f836ec5de3bc6f433fbb947ef2 | |
| parent | 4e299c1d9113b5c1c3845c0d4e78d09dd60a4fe8 (diff) | |
| download | linux-2842bb20eed2e25cde5114298edc62c8883a1d9a.tar.gz linux-2842bb20eed2e25cde5114298edc62c8883a1d9a.tar.bz2 linux-2842bb20eed2e25cde5114298edc62c8883a1d9a.zip | |
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>
| -rw-r--r-- | fs/jbd/commit.c | 9 |
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: 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); |