From 844e8d904a7c1446e3f040683b4a0645c3eb168f Mon Sep 17 00:00:00 2001 From: Jun'ichi Nomura Date: Fri, 9 Sep 2005 16:23:42 -0700 Subject: [PATCH] [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)) 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 Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/md/dm-raid1.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/drivers/md/dm-raid1.c b/drivers/md/dm-raid1.c index b08df8b..8632825 100644 --- a/drivers/md/dm-raid1.c +++ b/drivers/md/dm-raid1.c @@ -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(®->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(®->list); /* take off the clean list */ - spin_unlock_irq(&rh->region_lock); } + spin_unlock_irq(&rh->region_lock); - atomic_inc(®->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(®->pending)) { spin_lock_irqsave(&rh->region_lock, flags); + if (atomic_read(®->pending)) { /* check race */ + spin_unlock_irqrestore(&rh->region_lock, flags); + return; + } if (reg->state == RH_RECOVERING) { list_add_tail(®->list, &rh->quiesced_regions); } else { -- 2.7.4