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authorJan Kara <jack@suse.cz>2011-05-09 03:09:53 +0400
committerTheodore Ts'o <tytso@mit.edu>2011-05-09 03:09:53 +0400
commit229309caebe4508d650bb6d8f7d51f2b116f5bbd (patch)
tree6b9612369cac17205b21ca0b4d93ebbd25863f6d /fs/jbd2
parent667eff35a1f56fa74ce98a0c7c29a40adc1ba4e3 (diff)
downloadlinux-229309caebe4508d650bb6d8f7d51f2b116f5bbd.tar.xz
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')
-rw-r--r--fs/jbd2/commit.c9
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);