crypto: introduce: acomp_is_async to expose if comp drivers might sleep

acomp's users might want to know if acomp is really async to optimize
themselves.  One typical user which can benefit from exposed async stat is
zswap.

In zswap, zsmalloc is the most commonly used allocator for (and perhaps
the only one).  For zsmalloc, we cannot sleep while we map the compressed
memory, so we copy it to a temporary buffer.  By knowing the alg won't
sleep can help zswap to avoid the need for a buffer.  This shows
noticeable improvement in load/store latency of zswap.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Barry Song <[email protected]>
Acked-by: Herbert Xu <[email protected]>
Acked-by: Chris Li <[email protected]>
Cc: Chengming Zhou <[email protected]>
Cc: Dan Streetman <[email protected]>
Cc: David S. Miller <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Nhat Pham <[email protected]>
Cc: Seth Jennings <[email protected]>
Cc: Vitaly Wool <[email protected]>
Cc: Yosry Ahmed <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: Barry Song

include/crypto/acompress.h

@@ -160,6 +160,12 @@ static inline void acomp_request_set_tfm(struct acomp_req *req,
 	req->base.tfm = crypto_acomp_tfm(tfm);
 }
 
+static inline bool acomp_is_async(struct crypto_acomp *tfm)
+{
+	return crypto_comp_alg_common(tfm)->base.cra_flags &
+	       CRYPTO_ALG_ASYNC;
+}
+
 static inline struct crypto_acomp *crypto_acomp_reqtfm(struct acomp_req *req)
 {
 	return __crypto_acomp_tfm(req->base.tfm);