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authorMikulas Patocka <mpatocka@redhat.com>2009-12-10 23:51:54 +0000
committerAlasdair G Kergon <agk@redhat.com>2009-12-10 23:51:54 +0000
commit8e87b9b81b3c370f7e53c1ab6e1c3519ef37a644 (patch)
tree272a8532e12749c6c8419dcab0c341604646c571 /drivers/md/dm-snap.c
parent94e76572b5dd37b1f0f4b3742ee8a565daead932 (diff)
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 <mpatocka@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Diffstat (limited to 'drivers/md/dm-snap.c')
-rw-r--r--drivers/md/dm-snap.c2
1 files changed, 2 insertions, 0 deletions
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))