From: Frederic Weisbecker <fweisbec@gmail.com>
Date: Mon, 13 Apr 2009 22:10:35 +0000 (+0200)
Subject: reiserfs, kill-the-BKL: fix unsafe j_flush_mutex lock
X-Git-Tag: v2.6.33-rc1~360^2~29
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a412f9efdd6424bf4bf28c8e8c92060b5e975482;p=pandora-kernel.git

reiserfs, kill-the-BKL: fix unsafe j_flush_mutex lock

Impact: fix a deadlock

The j_flush_mutex is acquired safely in journal.c:
if we can't take it, we free the reiserfs per superblock lock
and wait a bit.

But we have a remaining place in kupdate_transactions() where
j_flush_mutex is still acquired traditionnaly. Thus the following
scenario (warned by lockdep) can happen:

A						B

mutex_lock(&write_lock)			mutex_lock(&write_lock)
	mutex_lock(&j_flush_mutex)	mutex_lock(&j_flush_mutex) //block
	mutex_unlock(&write_lock)
	sleep...
	mutex_lock(&write_lock) //deadlock

Fix this by using reiserfs_mutex_lock_safe() in kupdate_transactions().

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Alessio Igor Bogani <abogani@texware.it>
Cc: Jeff Mahoney <jeffm@suse.com>
LKML-Reference: <1239660635-12940-1-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---

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