linux-kernel - Re: [PATCH 3/5] mm/zswap: refactor out __zswap

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Date: Mon, 18 Dec 2023 16:15:39 +0800
From: Chengming Zhou <zhouchengming@...edance.com>
To: Yosry Ahmed <yosryahmed@...gle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, Nhat Pham <nphamcs@...il.com>,
 Chris Li <chriscli@...gle.com>, Johannes Weiner <hannes@...xchg.org>,
 Seth Jennings <sjenning@...hat.com>, Dan Streetman <ddstreet@...e.org>,
 Vitaly Wool <vitaly.wool@...sulko.com>, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org
Subject: Re: [PATCH 3/5] mm/zswap: refactor out __zswap_load()

On 2023/12/14 08:52, Yosry Ahmed wrote:
> On Tue, Dec 12, 2023 at 8:18 PM Chengming Zhou
> <zhouchengming@...edance.com> wrote:
>>
>> The zswap_load() and zswap_writeback_entry() have the same part that
>> decompress the data from zswap_entry to page, so refactor out the
>> common part as __zswap_load(entry, page).
>>
>> Signed-off-by: Chengming Zhou <zhouchengming@...edance.com>
>> Reviewed-by: Nhat Pham <nphamcs@...il.com>
> 
> On a second look, there a few nits here.
> 
> First I think it makes more sense to move this refactoring ahead of
> reusing destmem. Right now, we add the destmem reuse to zswap_load()
> only, then we do the refactor and zswap_writeback_entry() gets it
> automatically, so there is a slight change coming to
> zswap_writeback_entry() hidden in the refactoring patch.
> 
> Let's refactor out __zswap_load() first, then reuse destmem in it.

I tried but found that putting the __zswap_load() first would introduce
another failure case in zswap_writeback_entry(), since the temporary
memory allocation may fail.

So instead, I also move the dstmem reusing in zswap_writeback_entry() to
the dstmem reusing patch. Then this patch becomes having only refactoring.

Thanks.