crypto: shash - remove shash_desc::flags

The flags field in 'struct shash_desc' never actually does anything.
The only ostensibly supported flag is CRYPTO_TFM_REQ_MAY_SLEEP.
However, no shash algorithm ever sleeps, making this flag a no-op.

With this being the case, inevitably some users who can't sleep wrongly
pass MAY_SLEEP.  These would all need to be fixed if any shash algorithm
actually started sleeping.  For example, the shash_ahash_*() functions,
which wrap a shash algorithm with the ahash API, pass through MAY_SLEEP
from the ahash API to the shash API.  However, the shash functions are
called under kmap_atomic(), so actually they're assumed to never sleep.

Even if it turns out that some users do need preemption points while
hashing large buffers, we could easily provide a helper function
crypto_shash_update_large() which divides the data into smaller chunks
and calls crypto_shash_update() and cond_resched() for each chunk.  It's
not necessary to have a flag in 'struct shash_desc', nor is it necessary
to make individual shash algorithms aware of this at all.

Therefore, remove shash_desc::flags, and document that the
crypto_shash_*() functions can be called from any context.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 0 insertions, 11 deletions

diff --git a/crypto/hmac.c b/crypto/hmac.c
index 4ceb3f1f0eb8..a68c1266121f 100644
--- a/crypto/hmac.c
+++ b/crypto/hmac.c
@@ -57,8 +57,6 @@ static int hmac_setkey(struct crypto_shash *parent,
 	unsigned int i;
 
 	shash->tfm = hash;
-	shash->flags = crypto_shash_get_flags(parent)
-		& CRYPTO_TFM_REQ_MAY_SLEEP;
 
 	if (keylen > bs) {
 		int err;
@@ -91,8 +89,6 @@ static int hmac_export(struct shash_desc *pdesc, void *out)
 {
 	struct shash_desc *desc = shash_desc_ctx(pdesc);
 
-	desc->flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
-
 	return crypto_shash_export(desc, out);
 }
 
@@ -102,7 +98,6 @@ static int hmac_import(struct shash_desc *pdesc, const void *in)
 	struct hmac_ctx *ctx = hmac_ctx(pdesc->tfm);
 
 	desc->tfm = ctx->hash;
-	desc->flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
 
 	return crypto_shash_import(desc, in);
 }
@@ -117,8 +112,6 @@ static int hmac_update(struct shash_desc *pdesc,
 {
 	struct shash_desc *desc = shash_desc_ctx(pdesc);
 
-	desc->flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
-
 	return crypto_shash_update(desc, data, nbytes);
 }
 
@@ -130,8 +123,6 @@ static int hmac_final(struct shash_desc *pdesc, u8 *out)
 	char *opad = crypto_shash_ctx_aligned(parent) + ss;
 	struct shash_desc *desc = shash_desc_ctx(pdesc);
 
-	desc->flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
-
 	return crypto_shash_final(desc, out) ?:
 	       crypto_shash_import(desc, opad) ?:
 	       crypto_shash_finup(desc, out, ds, out);
@@ -147,8 +138,6 @@ static int hmac_finup(struct shash_desc *pdesc, const u8 *data,
 	char *opad = crypto_shash_ctx_aligned(parent) + ss;
 	struct shash_desc *desc = shash_desc_ctx(pdesc);
 
-	desc->flags = pdesc->flags & CRYPTO_TFM_REQ_MAY_SLEEP;
-
 	return crypto_shash_finup(desc, data, nbytes, out) ?:
 	       crypto_shash_import(desc, opad) ?:
 	       crypto_shash_finup(desc, out, ds, out);