Re: [PATCH v5 3/3] crypto: scompress: remove memcpy if sg_nents is 1

[Herbert Xu]

On Tue, Feb 20, 2024 at 07:44:14PM +1300, Barry Song wrote:
> From: Barry Song <v-songbaohua@xxxxxxxx>
> 
> while sg_nents is 1 which is always true for the current kernel
> as the only user - zswap is the case, we should remove two big
> memcpy.
> 
> Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx>
> Tested-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
> ---
>  crypto/scompress.c | 36 +++++++++++++++++++++++++++++-------
>  1 file changed, 29 insertions(+), 7 deletions(-)

This patch is independent of the other two.  Please split it
out so I can apply it directly.

> @@ -134,13 +135,25 @@ static int scomp_acomp_comp_decomp(struct acomp_req *req, int dir)
>  	scratch = raw_cpu_ptr(&scomp_scratch);
>  	spin_lock(&scratch->lock);
>  
> -	scatterwalk_map_and_copy(scratch->src, req->src, 0, req->slen, 0);
> +	if (sg_nents(req->src) == 1) {
> +		src = kmap_local_page(sg_page(req->src)) + req->src->offset;

What if the SG entry is longer than PAGE_SIZE (or indeed crosses a
page boundary)? I think the test needs to be strengthened.

Thanks,
-- 
Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Home Page: http://gondor.apana.org.au/~herbert/
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