crypto: ahash - Handle partial blocks in API

Provide an option to handle the partial blocks in the ahash API.
Almost every hash algorithm has a block size and are only able
to hash partial blocks on finalisation.

As a first step disable virtual address support for algorithms
with state sizes larger than HASH_MAX_STATESIZE.  This is OK as
virtual addresses are currently only used on synchronous fallbacks.

This means ahash_do_req_chain only needs to handle synchronous
fallbacks, removing the complexities of saving the request state.

Also move the saved request state into the ahash_request object
as nesting is no longer possible.

Add a scatterlist to ahash_request to store the partial block.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

include/crypto/hash.h

@@ -8,8 +8,8 @@
 #ifndef _CRYPTO_HASH_H
 #define _CRYPTO_HASH_H
 
-#include <linux/atomic.h>
 #include <linux/crypto.h>
+#include <linux/scatterlist.h>
 #include <linux/slab.h>
 #include <linux/string.h>
 
@@ -65,6 +65,10 @@ struct ahash_request {
 	};
 	u8 *result;
 
+	struct scatterlist sg_head[2];
+	crypto_completion_t saved_complete;
+	void *saved_data;
+
 	void *__ctx[] CRYPTO_MINALIGN_ATTR;
 };
 
@@ -488,7 +492,11 @@ int crypto_ahash_finup(struct ahash_request *req);
  * -EBUSY	if queue is full and request should be resubmitted later;
  * other < 0	if an error occurred
  */
-int crypto_ahash_final(struct ahash_request *req);
+static inline int crypto_ahash_final(struct ahash_request *req)
+{
+	req->nbytes = 0;
+	return crypto_ahash_finup(req);
+}
 
 /**
  * crypto_ahash_digest() - calculate message digest for a buffer