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b=En82ZQYAA3LUKTp7MwQkYWxetxRa/R/ktEzh0fKi1H9RfNcAjlr9unbq2gY8r7rZh 632LF7U8TfdolAn5JCO/VyAP0f6IHK2+3FLjC0WXIjpdbBCHuo0N6LaImCCEaBRqRw q+GOKMChF2SgifEBYZ1ryhXY+6pP3Acse7QJn6pTk18aGO1CyoZsLFnK5qKb2dv1p1 XLEJbGBxMe/AOUpBaWDmpQYW7RYyTKL9bEWmMgdg7QBxr5URyZafCC3IUclmm9Lcf6 e2a4G5g9/7vhx/6ed8vXLtpCN7CY9GYxqB/nCqW/ZSVlLlQeleUAxzwP1gWIc7k/B9 jYKVvRWOkPAsw== Message-ID: <24ca671b-074b-4d1c-ab50-1143279480ce@kernel.org> Date: Wed, 24 Jun 2026 17:07:55 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/4] mm: drop stale folio_ref_count()==1 check in do_swap_page reuse logic To: "Barry Song (Xiaomi)" , akpm@linux-foundation.org, linux-mm@kvack.org Cc: baoquan.he@linux.dev, chrisl@kernel.org, jp.kobryn@linux.dev, kasong@tencent.com, liam@infradead.org, linux-kernel@vger.kernel.org, ljs@kernel.org, mhocko@suse.com, nphamcs@gmail.com, rppt@kernel.org, shakeel.butt@linux.dev, shikemeng@huaweicloud.com, surenb@google.com, usama.arif@linux.dev, vbabka@kernel.org, youngjun.park@lge.com References: <20260623231635.43086-1-baohua@kernel.org> <20260623231635.43086-3-baohua@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: B291440016 X-Rspam-User: X-Stat-Signature: cymnde4z4ac5s3tjib8np9mhomobtmd3 X-HE-Tag: 1782313683-173445 X-HE-Meta: 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 6GiiJr/F qCibeQpw/hnls/giZ5LU3MLXMwE0TD4bCY9hVuVLyLsd/ocrgLk7Iu9dwCGejFX92y/9ZRgPeDth8kvxGr5H7TNP5FQmkM3sria3a4ek2DDiQB7GJvG0Bfyw9TvybYTeXbpCY8uhZi01CC/BFaSSM5Pohin6lxzJqH92AdJc1ZcZHo/JnKMmYaI4fu8NWD1bhtTHYbjqwSutbon7vPNAYct5JkKJZzqDq+yoCDagFUPLKNNYCAGmfsoo/p5QHdgrHJEbZX0UlV25MQzf+JPYuVc6wbT6xq2uGlxaXBasNnMB83WwoPsuVZ/bCEWN1eSiPhefr3ycMN6Kg2hVQMTKQIM7vFOc/ZlhVsn8r Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 6/24/26 01:16, Barry Song (Xiaomi) wrote: > The "we just allocated them without exposing them to the swapcache" > case no longer exists, as Kairui has routed synchronous I/O through > the swapcache as well in his series "unify swapin use swap cache and > cleanup flags"[1]. As a result, folio_ref_count() should never be 1 > in this path, since at least two references are held (base ref plus > swapcache). Remove the folio_ref_count()==1 check and update the > comment accordingly. > > [1] https://lore.kernel.org/all/20251220-swap-table-p2-v5-0-8862a265a033@tencent.com/ > > Acked-by: Usama Arif > Reviewed-by: Kairui Song > Reviewed-by: Baoquan He > Acked-by: Shakeel Butt > Signed-off-by: Barry Song (Xiaomi) > --- > mm/memory.c | 7 ++----- > 1 file changed, 2 insertions(+), 5 deletions(-) > > diff --git a/mm/memory.c b/mm/memory.c > index f6848f4234a6..abd0adcf65f0 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -5049,12 +5049,9 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) > > /* > * Same logic as in do_wp_page(); however, optimize for pages that are s/Same/Similar/ ? > - * certainly not shared either because we just allocated them without > - * exposing them to the swapcache or because the swap entry indicates > - * exclusivity. > + * certainly not because the swap entry indicates exclusivity. > */ > - if (!folio_test_ksm(folio) && > - (exclusive || folio_ref_count(folio) == 1)) { > + if (!folio_test_ksm(folio) && exclusive) { Hmm, but KSM folios should never have "exclusive" set. So I think you can drop that as well (was only relevant with folio_ref_count==1 check IIRC). -- Cheers, David