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Date: Tue, 16 Jan 2024 21:03:46 +0000
From: Matthew Wilcox <willy@infradead.org>
To: Zhongkun He <hezhongkun.hzk@bytedance.com>
Cc: Nhat Pham <nphamcs@gmail.com>, Yosry Ahmed <yosryahmed@google.com>,
	akpm@linux-foundation.org, hannes@cmpxchg.org, sjenning@redhat.com,
	ddstreet@ieee.org, vitaly.wool@konsulko.com, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, Chris Li <chrisl@kernel.org>
Subject: Re: [External] Re: [PATCH] mm: zswap: fix the lack of page lru flag
 in zswap_writeback_entry
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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.