From 8e87b9b81b3c370f7e53c1ab6e1c3519ef37a644 Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Thu, 10 Dec 2009 23:51:54 +0000 Subject: [PATCH] dm snapshot: cope with chunk size larger than origin Under some special conditions the snapshot hash_size is calculated as zero. This patch instead sets a minimum value of 64, the same as for the pending exception table. rounddown_pow_of_two(0) is an undefined operation (it expands to shift by -1). init_exception_table with an argument of 0 would fail with -ENOMEM. The way to trigger the problem is to create a snapshot with a chunk size that is larger than the origin device. Cc: stable@kernel.org Signed-off-by: Mikulas Patocka Signed-off-by: Alasdair G Kergon --- drivers/md/dm-snap.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c index d135212958f1..8a4a9c838afd 100644 --- a/drivers/md/dm-snap.c +++ b/drivers/md/dm-snap.c @@ -553,6 +553,8 @@ static int init_hash_tables(struct dm_snapshot *s) hash_size = min(origin_dev_size, cow_dev_size) >> s->store->chunk_shift; hash_size = min(hash_size, max_buckets); + if (hash_size < 64) + hash_size = 64; hash_size = rounddown_pow_of_two(hash_size); if (init_exception_table(&s->complete, hash_size, DM_CHUNK_CONSECUTIVE_BITS)) -- 2.34.1