On Fri, Nov 11, 2011 at 09:34:44AM -0800, Mandeep Singh Baines wrote:
>
> +/**
> + * dm_bht_compute_hash: hashes a page of data
> + */
> +static int dm_bht_compute_hash(struct dm_bht *bht, struct page *pg,
> + unsigned int offset, u8 *digest)
> +{
> + struct shash_desc *hash_desc = bht->hash_desc[smp_processor_id()];
> + void *data;
> + int err;
You don't need to have one shash_desc per cpu. As the shash interface is
synchronous, you could either allocate a new shash_desc with every call
to dm_bht_compute_hash, or just place the shash_desc with the context to
the stack of this function. The easiest thing would be to add the
shash transformation direct to dm_bht and then something like
struct {
struct shash_desc desc;
char ctx[crypto_shash_descsize(bht->tfm)];
} hash_desc;
hash_desc.desc.tfm = bmt->tfm;
The intermediate and final digest values are stored to hash_desc.ctx.
This is local, hence it's reentrant.
> +
> + /* Note, this is synchronous. */
> + if (crypto_shash_init(hash_desc)) {
> + DMCRIT("failed to reinitialize crypto hash (proc:%d)",
> + smp_processor_id());
> + return -EINVAL;
> + }
> + data = kmap_atomic(pg);
> + err = crypto_shash_update(hash_desc, data + offset, PAGE_SIZE);
> + kunmap_atomic(data);
> + if (err) {
> + DMCRIT("crypto_hash_update failed");
> + return -EINVAL;
> + }
> + if (crypto_shash_update(hash_desc, bht->salt, sizeof(bht->salt))) {
> + DMCRIT("crypto_hash_update failed");
> + return -EINVAL;
> + }
> + if (crypto_shash_final(hash_desc, digest)) {
> + DMCRIT("crypto_hash_final failed");
> + return -EINVAL;
> + }
> +
> + return 0;
> +}
> +
[snip]
> + * TODO(wad): All hash storage memory is pre-allocated and freed once an
> + * entire branch has been verified.
> + */
> +struct dm_bht {
> + /* Configured values */
> + int depth; /* Depth of the tree including the root */
> + unsigned int block_count; /* Number of blocks hashed */
> + unsigned int block_size; /* Size of a hash block */
> + char hash_alg[CRYPTO_MAX_ALG_NAME];
> + unsigned char salt[DM_BHT_SALT_SIZE];
> +
> + /* Computed values */
> + unsigned int node_count; /* Data size (in hashes) for each entry */
> + unsigned int node_count_shift; /* first bit set - 1 */
> + /* There is one per CPU so that verified can be simultaneous. */
> + struct shash_desc *hash_desc[NR_CPUS]; /* Container for the hash alg */
As mentioned above, you don't need to have one shash_desc per cpu.
Replace this with a 'struct crypto_shash *tfm;' and add this transformation
to the local hash_desc.
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