path: root/fs/jbd/commit.c
diff options
authorJan Kara <jack@suse.cz>2011-05-05 13:59:35 +0200
committerJan Kara <jack@suse.cz>2011-05-17 13:47:42 +0200
commit2842bb20eed2e25cde5114298edc62c8883a1d9a (patch)
treeaf4d60d1e5e922f836ec5de3bc6f433fbb947ef2 /fs/jbd/commit.c
parentext2: fix error msg when mounting fs with too-large blocksize (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/jbd/commit.c')
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");