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>
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@ -553,6 +553,8 @@ static int init_hash_tables(struct dm_snapshot *s)
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hash_size = min(origin_dev_size, cow_dev_size) >> s->store->chunk_shift;
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hash_size = min(hash_size, max_buckets);
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if (hash_size < 64)
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hash_size = 64;
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hash_size = rounddown_pow_of_two(hash_size);
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if (init_exception_table(&s->complete, hash_size,
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DM_CHUNK_CONSECUTIVE_BITS))
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