linux-kernel - Re: [External] Re: [PATCH] mm: zswap: fix the lack of page lru flag in zswap_writeback

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Message-ID: <CACSyD1PYm4wwQvOjkHZVcfuo-Voa4ABZ--n3K70i+s5ag9KnfA@mail.gmail.com>
Date: Wed, 17 Jan 2024 18:41:44 +0800
From: Zhongkun He <hezhongkun.hzk@...edance.com>
To: Matthew Wilcox <willy@...radead.org>
Cc: Nhat Pham <nphamcs@...il.com>, Yosry Ahmed <yosryahmed@...gle.com>, akpm@...ux-foundation.org, 
	hannes@...xchg.org, sjenning@...hat.com, ddstreet@...e.org, 
	vitaly.wool@...sulko.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org, 
	Chris Li <chrisl@...nel.org>
Subject: Re: [External] Re: [PATCH] mm: zswap: fix the lack of page lru flag
 in zswap_writeback_entry

On Wed, Jan 17, 2024 at 5:04 AM Matthew Wilcox <willy@...radead.org> wrote:
>
> On Tue, Jan 16, 2024 at 09:40:05PM +0800, Zhongkun He wrote:
> > 2)  __read_swap_cache_async has six parameters, so there is no space to
> > add a new one, add_to_lru_head.
>
> That's easy enough.  Define a new set of flags, make one of them the
> equivalent of skip_if_exists.  Something like:
>
> typedef unsigned int __bitwise read_swap_t;
>
> #define READ_SWAP_SKIP_EXISTING ((__force read_swap_t)0x00000001)
> #define READ_SWAP_ADD_TAIL      ((__force read_swap_t)0x00000002)
>
> There's only six callers of __read_swap_cache_async() to convert, so not
> really a big deal.
>

Yes, thanks for your suggestion.
The major problem is not the parameters, but the need to add three functions
to deal with a special case.  Thanks again.