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| author | Jan Kara <jack@suse.cz> | 2011-05-08 19:09:53 -0400 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2011-05-08 19:09:53 -0400 |
| commit | 229309caebe4508d650bb6d8f7d51f2b116f5bbd (patch) | |
| tree | 6b9612369cac17205b21ca0b4d93ebbd25863f6d /fs/jbd2/commit.c | |
| parent | 667eff35a1f56fa74ce98a0c7c29a40adc1ba4e3 (diff) | |
| download | linux-229309caebe4508d650bb6d8f7d51f2b116f5bbd.tar.gz linux-229309caebe4508d650bb6d8f7d51f2b116f5bbd.tar.bz2 linux-229309caebe4508d650bb6d8f7d51f2b116f5bbd.zip | |
jbd2: 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.
Reported-by: Tao Ma <boyu.mt@taobao.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Diffstat (limited to 'fs/jbd2/commit.c')
| -rw-r--r-- | fs/jbd2/commit.c | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c index 6e28000a4b21..78c299218681 100644 --- a/fs/jbd2/commit.c +++ b/fs/jbd2/commit.c @@ -760,8 +760,13 @@ wait_for_iobuf: required. */ JBUFFER_TRACE(jh, "file as BJ_Forget"); jbd2_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 + * jbd2_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); |