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Received: from 30.74.144.137(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0XDgFIpV_1793178096 cluster:ay36) by smtp.aliyun-inc.com; Wed, 28 Oct 2026 17:01:38 +0800 Message-ID: <7f4155ef-9f5c-4567-a84d-dddf640cb844@linux.alibaba.com> Date: Wed, 28 Oct 2026 17:01:36 +0800 X-Archived-By: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 12/14] mm/shmem: fix truncate loop after boundary swapin failure To: "David Hildenbrand (Arm)" , Andrew Morton , Gregory Price , Zi Yan , Joshua Hahn , Rakie Kim , Ying Huang , Johannes Weiner , Vladimir Davydov , Michal Hocko , Hugh Dickins , Lukas Czerner , Carlos Maiolino , Christian Brauner , Jan Kara , Daniel Verkamp , Jeff Xu , Muchun Song , Oscar Salvador , David Stevens , "Matthew Wilcox (Oracle)" , William Kucharski , Chris Li , Kairui Song , Nhat Pham , Miaohe Lin , Naoya Horiguchi Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, "Kiryl Shutsemau (Meta)" References: <20261027-fixes_shmem-v2-0-86a00952acb9@kernel.org> <20261027-fixes_shmem-v2-12-86a00952acb9@kernel.org> <2d111275-e7a8-4ac5-8618-f068e87145f2@linux.alibaba.com> <10ae2533-cc4b-4c30-95d7-705815ba7830@kernel.org> From: Baolin Wang In-Reply-To: <10ae2533-cc4b-4c30-95d7-705815ba7830@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 172F4A0002 X-Stat-Signature: 6it3dneud1dja7caoobybmbihn83h11p X-Spam-Status: No, score=-19.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS, UNPARSEABLE_RELAY,USER_AGENT_SANE_1,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=4.0.1 X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1793178102-967050 X-HE-Meta: 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 T+sykRH3 GEwMEaH1XgtYkk9flMVUv6tAsIW0cpdCnDU24Tagu8BnUNJ2Q/5xwh5McDWETdPxKUO3kAbasR7/wQ2Hjk28lp1heZByfcXADDHEInKCBnyLi0j7LFZ1sahUO7mj2gSQicDfKSTy4BfvaAQ2IVDtcMA2PYijVWwVeEVtoKHm/F7pCE/oZ84Hnp2H7FG7DfUbeqMf5MCd1xmE2X1lKrEmk4Cyns9cIg6fYVcEBur4TVOri7r7d8H5FNOmIJoWGzqmC2wqLjSoZjZipRbaRoOsDzzNB1Rpzp9j65ITdmlRZ6Q8POHub2fVzWHqerOHH5/QYdIuSF8GE7LvF9k27FdYPWHNUUvSxMaiU4/VY7TE2415KnfaVM6u6sgLf/A== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On 10/28/26 4:21 PM, David Hildenbrand (Arm) wrote: > On 10/28/26 02:30, Baolin Wang wrote: >> >> >> On 10/27/26 9:03 PM, David Hildenbrand (Arm) wrote: >>> If swapping in a large entry at the new EOF fails, shmem_undo_range() >>> leaves the entry in place. Its final scan skips the entry, then restarts >>> from the same start index and finds it again. Truncation can loop forever >>> while holding i_rwsem. >> >> Right. But ... >> >>> Advance start past the skipped entry so that a restarted scan can finish, >>> as we already do for folios that cannot be split. >> >> IIRC, we originally avoided advancing start because a concurrent swapin fault >> could split the boundary large swap entry via shmem_split_large_entry(), leaving >> small swap entries below the new start. >> >> Sigh. >> >> There doesn't seem to be a simple fix. We may need to swap in the large entry as >> shmem_get_partial_folio() does, and then split the large folio. I'll work on >> this as a follow-up. > > Thanks! > > So you are fine with the patch as is to fix the endless loop? Yes, let's get this fixed first. Reviewed-by: Baolin Wang