Re: [PATCH v2 07/21] crypto: shash, caam: Make use of the new sg_map helper function

On 26/04/17 09:56 PM, Herbert Xu wrote: > On Tue, Apr 25, 2017 at 12:20:54PM -0600, Logan Gunthorpe wrote: >> Very straightforward conversion to the new function in the caam driver >> and shash library. >> >> Signed-off-by: Logan Gunthorpe <logang(a)deltatee.com&gt; >> Cc: Herbert Xu <herbert(a)gondor.apana.org.au&gt; >> Cc: "David S. Miller" <davem(a)davemloft.net&gt; >> --- >> crypto/shash.c | 9 ++++++--- >> drivers/crypto/caam/caamalg.c | 8 +++----- >> 2 files changed, 9 insertions(+), 8 deletions(-) >> >> diff --git a/crypto/shash.c b/crypto/shash.c >> index 5e31c8d..5914881 100644 >> --- a/crypto/shash.c >> +++ b/crypto/shash.c >> @@ -283,10 +283,13 @@ int shash_ahash_digest(struct ahash_request *req, struct shash_desc *desc) >> if (nbytes < min(sg->length, ((unsigned int)(PAGE_SIZE)) - offset)) { >> void *data; >> >> - data = kmap_atomic(sg_page(sg)); >> - err = crypto_shash_digest(desc, data + offset, nbytes, >> + data = sg_map(sg, 0, SG_KMAP_ATOMIC); >> + if (IS_ERR(data)) >> + return PTR_ERR(data); >> + >> + err = crypto_shash_digest(desc, data, nbytes, >> req->result); >> - kunmap_atomic(data); >> + sg_unmap(sg, data, 0, SG_KMAP_ATOMIC); >> crypto_yield(desc->flags); >> } else >> err = crypto_shash_init(desc) ?: > > Nack. This is an optimisation for the special case of a single > SG list entry. In fact in the common case the kmap_atomic should > disappear altogether in the no-highmem case. So replacing it > with sg_map is not acceptable. What you seem to have missed is that sg_map is just a thin wrapper around kmap_atomic. Perhaps with a future check for a mappable page. This change should have zero impact on performance.