crypto: ahash - optimize performance when wrapping shash

The "ahash" API provides access to both CPU-based and hardware offload-
based implementations of hash algorithms.  Typically the former are
implemented as "shash" algorithms under the hood, while the latter are
implemented as "ahash" algorithms.  The "ahash" API provides access to
both.  Various kernel subsystems use the ahash API because they want to
support hashing hardware offload without using a separate API for it.

Yet, the common case is that a crypto accelerator is not actually being
used, and ahash is just wrapping a CPU-based shash algorithm.

This patch optimizes the ahash API for that common case by eliminating
the extra indirect call for each ahash operation on top of shash.

It also fixes the double-counting of crypto stats in this scenario
(though CONFIG_CRYPTO_STATS should *not* be enabled by anyone interested
in performance anyway...), and it eliminates redundant checking of
CRYPTO_TFM_NEED_KEY.  As a bonus, it also shrinks struct crypto_ahash.

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

1 files changed, 10 insertions, 0 deletions

diff --git a/crypto/hash.h b/crypto/hash.h
index de2ee2f4ae30..93f6ba0df263 100644
--- a/crypto/hash.h
+++ b/crypto/hash.h
@@ -12,6 +12,16 @@
 
 #include "internal.h"
 
+static inline struct crypto_istat_hash *hash_get_stat(
+	struct hash_alg_common *alg)
+{
+#ifdef CONFIG_CRYPTO_STATS
+	return &alg->stat;
+#else
+	return NULL;
+#endif
+}
+
 static inline int crypto_hash_report_stat(struct sk_buff *skb,
 					  struct crypto_alg *alg,
 					  const char *type)