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authorJan Kara <jack@suse.cz>2011-05-05 13:59:35 +0200
committerGreg Kroah-Hartman <gregkh@suse.de>2011-06-03 09:31:50 +0900
commit0a5cb949920f8796c684fcde2da098e00c4c28da (patch)
tree089b106eb09eefe07dd1973c1db99229d44b8577 /fs
parent61485c2e416f12932cfd9423ad0641b975b4de65 (diff)
jbd: Fix forever sleeping process in do_get_write_access()
commit 2842bb20eed2e25cde5114298edc62c8883a1d9a upstream. 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: Greg Kroah-Hartman <gregkh@suse.de>
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 69b18045946..f486ff69778 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);