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b=rTzwgXpuF6wQ6jCQ7lvKPIPDg2fLAGyHaXZFUNv6JipJz5CzRhPf6kq4goHKupdG6G396MxwFY1fccJMq/gc8djTZubrVpBUka+/G31Ii+LH1DkuMiTb2aWcvS7TKh76uN5y+27oxtSQezDob1jQCW64PVhJ4Z1DFw6mroqTdwc= Received: from 30.74.144.132(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0WnQW09W_1757300926 cluster:ay36) by smtp.aliyun-inc.com; Mon, 08 Sep 2025 11:08:47 +0800 Message-ID: Date: Mon, 8 Sep 2025 11:08:46 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 03/15] mm, swap: fix swap cahe index error when retrying reclaim To: Kairui Song , linux-mm@kvack.org Cc: Andrew Morton , Matthew Wilcox , Hugh Dickins , Chris Li , Barry Song , Baoquan He , Nhat Pham , Kemeng Shi , Ying Huang , Johannes Weiner , David Hildenbrand , Yosry Ahmed , Lorenzo Stoakes , Zi Yan , linux-kernel@vger.kernel.org References: <20250905191357.78298-1-ryncsn@gmail.com> <20250905191357.78298-4-ryncsn@gmail.com> From: Baolin Wang In-Reply-To: <20250905191357.78298-4-ryncsn@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: C7E4240008 X-Stat-Signature: gbx73qs4istebqjkhyjsa4nifupb7pbh X-Rspam-User: X-HE-Tag: 1757300932-29647 X-HE-Meta: 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 ElMA0toL NaUJm2wgkRA4qmfmlbpAtv0QjHYvZFEyscNMGL/yQTvcmC2xehTc5B9O2Nib4r+ytXTK1YPBcrt54wOchYL+PsYcsd+aFAR/r1rKIcQjnjnPyxWNdMUIsha0Cyt40s9ZuTZl33U7CKYJ1qg+sTYKy2+ml4R7sB4jR4lt2B7RORVtGG9+oUTYInF4d8XBZ48ZdySAJd1lD8KHFvoQu2+gPZJJfttX0mIzmjCqjCzUb9xRgPJ5ELBZOMmTAFRi42IdP1qAiJiUR3RFUeLaSB7Xq3lVyHuh/1aG0Icdn5iG2FY83XGt2hVZ/L25uHa9nVTwhKMBKEBLxcNuGSek= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2025/9/6 03:13, Kairui Song wrote: > From: Kairui Song > > The allocator will reclaim cached slots while scanning. Currently, it > will try again if the reclaim found a folio that is already removed from > the swap cache due to a race. But the following lookup will be using the > wrong index. It won't cause any OOB issue since the swap cache index is > truncated upon lookup, but it may lead to reclaiming of an irrelevant > folio. > > This should not cause a measurable issue, but we should fix it. > > Fixes: fae8595505313 ("mm, swap: avoid reclaiming irrelevant swap cache") > Signed-off-by: Kairui Song > --- Good catch. LGTM. Reviewed-by: Baolin Wang > mm/swapfile.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/mm/swapfile.c b/mm/swapfile.c > index 4b8ab2cb49ca..4c63fc62f4cb 100644 > --- a/mm/swapfile.c > +++ b/mm/swapfile.c > @@ -240,13 +240,13 @@ static int __try_to_reclaim_swap(struct swap_info_struct *si, > * Offset could point to the middle of a large folio, or folio > * may no longer point to the expected offset before it's locked. > */ > - entry = folio->swap; > - if (offset < swp_offset(entry) || offset >= swp_offset(entry) + nr_pages) { > + if (offset < swp_offset(folio->swap) || > + offset >= swp_offset(folio->swap) + nr_pages) { > folio_unlock(folio); > folio_put(folio); > goto again; > } > - offset = swp_offset(entry); > + offset = swp_offset(folio->swap); > > need_reclaim = ((flags & TTRS_ANYWAY) || > ((flags & TTRS_UNMAPPED) && !folio_mapped(folio)) ||