From: Jan Kara <jack@suse.cz>
Date: Thu, 5 May 2011 11:59:35 +0000 (+0200)
Subject: jbd: Fix forever sleeping process in do_get_write_access()
X-Git-Tag: v2.6.39.1~118
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0a5cb949920f8796c684fcde2da098e00c4c28da;p=pandora-kernel.git

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>
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