[dm-devel] [PATCH] 2.6.12-rc6: fix rh_dec()/rh_inc() race in dm-raid1.c

[Jun'ichi Nomura]

Hello,

Attached patch fixes the 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 at ce.jp.nec.com>

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