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Commit 844e8d90 authored by Jun'ichi Nomura's avatar Jun'ichi Nomura Committed by Linus Torvalds
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[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: default avatarJun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent e5dcdd80

drivers/md/dm-raid1.c

+9 −3
Original line number Diff line number Diff line
@@ -375,16 +375,18 @@ static void rh_inc(struct region_hash *rh, region_t region) 


	read_lock(&rh->hash_lock);

	reg = __rh_find(rh, region);



	atomic_inc(&reg->pending);



	spin_lock_irq(&rh->region_lock);

	if (reg->state == RH_CLEAN) {

		rh->log->type->mark_region(rh->log, reg->key);



		spin_lock_irq(&rh->region_lock);

		reg->state = RH_DIRTY;

		list_del_init(&reg->list);	/* take off the clean list */

		spin_unlock_irq(&rh->region_lock);

	}

	spin_unlock_irq(&rh->region_lock);



	atomic_inc(&reg->pending);

	read_unlock(&rh->hash_lock);

}
@@ -408,6 +410,10 @@ static void rh_dec(struct region_hash *rh, region_t region) 


	if (atomic_dec_and_test(&reg->pending)) {

		spin_lock_irqsave(&rh->region_lock, flags);

		if (atomic_read(&reg->pending)) { /* check race */

			spin_unlock_irqrestore(&rh->region_lock, flags);

			return;

		}

		if (reg->state == RH_RECOVERING) {

			list_add_tail(&reg->list, &rh->quiesced_regions);

		} else {