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fs-verity: use mempool for hash requests

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When initializing an fs-verity hash algorithm, also initialize a mempool
that contains a single preallocated hash request object.  Then replace
the direct calls to ahash_request_alloc() and ahash_request_free() with
allocating and freeing from this mempool.

This eliminates the possibility of the allocation failing, which is
desirable for the I/O path.

This doesn't cause deadlocks because there's no case where multiple hash
requests are needed at a time to make forward progress.

Link: https://lore.kernel.org/r/20191231175545.20709-1-ebiggers@kernel.org
Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Eric Biggers <ebiggers@google.com>
This commit is contained in:
Eric Biggers
2019-12-31 11:55:45 -06:00
parent fd39073dba
commit 439bea104c
5 changed files with 97 additions and 46 deletions
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4
fs/verity/open.c
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@@ -31,7 +31,7 @@ int fsverity_init_merkle_tree_params(struct merkle_tree_params *params,
unsigned int log_blocksize,
const u8 *salt, size_t salt_size)
{
const struct fsverity_hash_alg *hash_alg;
struct fsverity_hash_alg *hash_alg;
int err;
u64 blocks;
u64 offset;
@@ -127,7 +127,7 @@ out_err:
* Compute the file measurement by hashing the fsverity_descriptor excluding the
* signature and with the sig_size field set to 0.
*/
static int compute_file_measurement(const struct fsverity_hash_alg *hash_alg,
static int compute_file_measurement(struct fsverity_hash_alg *hash_alg,
struct fsverity_descriptor *desc,
u8 *measurement)
{