linux-kernel - Re: [PATCH v7] crypto: scompress: remove memcpy if sg

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Message-ID: <bf2a5631-79cc-414e-82f0-6b45e487c8d9@roeck-us.net>
Date: Sun, 17 Mar 2024 17:13:57 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Barry Song <21cnbao@...il.com>
Cc: herbert@...dor.apana.org.au, davem@...emloft.net,
 linux-crypto@...r.kernel.org, akpm@...ux-foundation.org, chrisl@...nel.org,
 sjenning@...hat.com, vitaly.wool@...sulko.com, linux-kernel@...r.kernel.org,
 Barry Song <v-songbaohua@...o.com>, Johannes Weiner <hannes@...xchg.org>,
 Nhat Pham <nphamcs@...il.com>, Yosry Ahmed <yosryahmed@...gle.com>,
 Chengming Zhou <zhouchengming@...edance.com>
Subject: Re: [PATCH v7] crypto: scompress: remove memcpy if sg_nents is 1 and
 pages are lowmem

On 3/17/24 16:48, Barry Song wrote:
> On Mon, Mar 18, 2024 at 7:13 AM Guenter Roeck <linux@...ck-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:

Thanks for the update.

> https://lore.kernel.org/all/20240313045036.51065-1-21cnbao@gmail.com/
> 

That doesn't build for me.

   CC      arch/xtensa/kernel/asm-offsets.s
In file included from ./include/linux/highmem.h:8,
                  from ./include/linux/bvec.h:10,
                  from ./include/linux/blk_types.h:10,
                  from ./include/linux/writeback.h:13,
                  from ./include/linux/memcontrol.h:23,
                  from ./include/linux/swap.h:9,
                  from ./include/linux/suspend.h:5,
                  from arch/xtensa/kernel/asm-offsets.c:24:
/include/linux/cacheflush.h:9:5: error: "ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE" is not defined, evaluates to 0 [-Werror=undef]
     9 | #if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE

A similar works for loongarch, so I don't know what is wrong.
Maybe some context patch is missing.

Guenter