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authorJun'ichi Nomura <j-nomura@ce.jp.nec.com>2005-09-10 01:23:42 +0200
committerLinus Torvalds <torvalds@g5.osdl.org>2005-09-10 01:39:09 +0200
commit844e8d904a7c1446e3f040683b4a0645c3eb168f (patch)
tree5e277539dab95d6325cec564a91e0e70acdce021
parent[PATCH] md: fail IO request to md that require a barrier. (diff)
downloadlinux-844e8d904a7c1446e3f040683b4a0645c3eb168f.tar.xz
linux-844e8d904a7c1446e3f040683b4a0645c3eb168f.zip
[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>
-rw-r--r--drivers/md/dm-raid1.c12
1 files changed, 9 insertions, 3 deletions
diff --git a/drivers/md/dm-raid1.c b/drivers/md/dm-raid1.c
index b08df8b9b2ca..863282513753 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(&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 {