From: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Date: Fri, 9 Sep 2005 23:23:42 +0000 (-0700)
Subject: [PATCH] dm: fix rh_dec()/rh_inc() race in dm-raid1.c
X-Git-Tag: v2.6.14-rc1~253
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=844e8d904a7c1446e3f040683b4a0645c3eb168f;p=pandora-kernel.git

[PATCH] dm: fix rh_dec()/rh_inc() race in dm-raid1.c

Fix another bug in dm-raid1.c that the dirty region may stay in or be moved
to clean list and freed while in use.

It happens as follows:

   CPU0                                   CPU1
   ------------------------------------------------------------------------------
   rh_dec()
     if (atomic_dec_and_test(pending))
        <the region is still marked dirty>
                                          rh_inc()
                                            if the region is clean
                                               mark the region dirty
                                               and remove from clean list
        mark the region clean
        and move to clean list
                                                  atomic_inc(pending)

At this stage, the region is in clean list and will be mistakenly reclaimed
by rh_update_states() later.

Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---

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