Re: [PATCH v7] crypto: scompress: remove memcpy if sg_nents is 1 and pages are lowmem

From: Barry Song <21cnbao@gmail.com>
To: Guenter Roeck <linux@roeck-us.net>
Cc: herbert@gondor.apana.org.au, davem@davemloft.net,
	 linux-crypto@vger.kernel.org, akpm@linux-foundation.org,
	chrisl@kernel.org,  sjenning@redhat.com,
	vitaly.wool@konsulko.com, linux-kernel@vger.kernel.org,
	 Barry Song <v-songbaohua@oppo.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	 Nhat Pham <nphamcs@gmail.com>,
	Yosry Ahmed <yosryahmed@google.com>,
	 Chengming Zhou <zhouchengming@bytedance.com>
Subject: Re: [PATCH v7] crypto: scompress: remove memcpy if sg_nents is 1 and pages are lowmem
Date: Mon, 18 Mar 2024 07:48:19 +0800	[thread overview]
Message-ID: <CAGsJ_4wWEdxk0qNV89bL0zeGaXUBb7h92mdNeRCgcUCY5C84ww@mail.gmail.com> (raw)
In-Reply-To: <aaa8b7d7-5abe-47bf-93f6-407942436472@roeck-us.net>

On Mon, Mar 18, 2024 at 7:13 AM Guenter Roeck <linux@roeck-us.net> wrote:
>
> Hi,
>
> On Sat, Mar 02, 2024 at 08:27:45AM +1300, Barry Song wrote:
> [ ... ]
> > @@ -152,8 +165,17 @@ static int scomp_acomp_comp_decomp(struct acomp_req *req, int dir)
> >                       ret = -ENOSPC;
> >                       goto out;
> >               }
> > -             scatterwalk_map_and_copy(scratch->dst, req->dst, 0, req->dlen,
> > -                                      1);
> > +             if (dst == scratch->dst) {
> > +                     scatterwalk_map_and_copy(scratch->dst, req->dst, 0,
> > +                                              req->dlen, 1);
> > +             } else {
> > +                     int nr_pages = DIV_ROUND_UP(req->dst->offset + req->dlen, PAGE_SIZE);
> > +                     int i;
> > +                     struct page *dst_page = sg_page(req->dst);
> > +
> > +                     for (i = 0; i < nr_pages; i++)
> > +                             flush_dcache_page(dst_page + i);
>
> flush_dcache_page() is an empty macro on some architectures
> such as xtensa. This results in

Hi Guenter,

this is a bug of xtensa, could you test the patch:
https://lore.kernel.org/all/20240313045036.51065-1-21cnbao@gmail.com/

>
> Building xtensa:allmodconfig ... failed
> --------------
> Error log:
> crypto/scompress.c: In function 'scomp_acomp_comp_decomp':
> crypto/scompress.c:174:38: error: unused variable 'dst_page'
>
> on the affected architectures.
>
> Guenter

Thanks
Barry