From: Jan Kara <jack@suse.cz>
Date: Tue, 4 Jun 2013 16:22:15 +0000 (-0400)
Subject: jbd2: fix race in t_outstanding_credits update in jbd2_journal_extend()
X-Git-Tag: omap-for-v3.11/fixes-for-merge-window~83^2~53
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=fe1e8db598b259eafdffbe3dd5fe849cd2ad97d5;p=pandora-kernel.git

jbd2: fix race in t_outstanding_credits update in jbd2_journal_extend()

jbd2_journal_extend() first checked whether transaction can accept
extending handle with more credits and then added credits to
t_outstanding_credits.  This can race with start_this_handle() adding
another handle to a transaction and thus overbooking a transaction.
Make jbd2_journal_extend() use atomic_add_return() to close the race.

Reviewed-by: Zheng Liu <wenqing.lz@taobao.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
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