From: Jan Kara <jack@suse.cz>
Date: Sun, 8 May 2011 23:09:53 +0000 (-0400)
Subject: jbd2: Fix forever sleeping process in do_get_write_access()
X-Git-Tag: v3.0-rc1~140^2~47
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=229309caebe4508d650bb6d8f7d51f2b116f5bbd;p=pandora-kernel.git

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>
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