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t=1793127788; bh=z2aICW6ha5mvAYcJTiKr0lmuhUF+UbL5lXiLkXBjUAA=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=n+WA9GNgsZok/1bfEEz2jnBVNjFM9RCPATbiZ3nZjEc4IWyk8DMWmdqf4y0yDp3Nk E7ZL/Uk8T+VM6ijsONiQbZMONfbqfABEznvjkqS6NgUU60Mz8R7vr7EWE6wSrS0cYu OwDmo+nIMCV2nM9WmqsKwoTKI9VkjrpzGRkq2CmRQVTwXunYfm/9QaVTXJx7P7tClw aQ3ETzz49IbbnD6kOa2Jki/Rp03R48LCJ8UDgkEJjnTqNzrU3WhDO3U8bTkL/ndP/V 3+OcMyuIwKPCmhg+/6GvyQ5ajb6AO5jG7HJepgBLRsF0SeSY/e0L7O0SIQavT4WGIk 5FZTSbuWwIhog== Message-ID: <331082ad-d8ad-40ec-a281-b9aee72a3f75@kernel.org> Date: Tue, 27 Oct 2026 20:03:00 +0100 X-Archived-By: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4] khugepaged: fix readahead lock inversion in collapse_file() To: Lance Yang , akpm@linux-foundation.org Cc: ziy@nvidia.com, baolin.wang@linux.alibaba.com, liam@infradead.org, nico.pache@linux.dev, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, usama.arif@linux.dev, kas@kernel.org, jack@suse.cz, djwong@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, hch@lst.de, pfalcato@suse.de, ngocthang2710.1999@gmail.com, syzbot+16bf7cd0ebeb1de93aa5@syzkaller.appspotmail.com, stable@vger.kernel.org References: <20261026152013.10511-1-lance.yang@linux.dev> 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-Stat-Signature: bqi8nixzqux1oxbq68ttyaciumwa3nha X-Spam-Status: No, score=-12.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=4.0.1 X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 8FE7D140007 X-Rspam-User: X-HE-Tag: 1793127789-429773 X-HE-Meta: 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 qAq+SQmb i7fYjcb7+3NmcxbX90aQUVEOb8A0K8VtJMDxOrJfd6GzmxL3Lu0Yee0jerro8CfOh0DXbyCxx3p9UOoeBbEYcSduXQ/A0RgVLgrpq9Rq4kprn6QbXsL+/BfaDRYlzkO8FhH4/Jxo1WlesPVFZLq12+mFTyx9c/+x/c7bjiahZJIwsq+DAQ4117bioNPtzJ7rZ+1/Lz3JHCSDvuorWNSwCKaacjCMOYaNjBMfiyVHkPGUonVhdBUtlK0s6qEGA8h6ccFrPHM5Q3X7kn71a7G8Sqd0Z6W1jbePBLwn8wihqmU9P1bH1FY95rvkCmRtTMlJ+1VGhupQcSmRfSM+WltoWIFPPPm/CY3r8892NjxeHmIu6Bl7vhhjW5mmj4sT9J0BYVxQC1dtiBMomjYj1oEfsW2HEgMOi7T2BogqhLzGSmBEsjYIDayTFxAz4MBw3CD1Lp0KYY3nGpz00JbP1Oe5AFi3z3419RHwfKaGHP5dnFax4IS7Uo94OVvbdTNYg3Uesm/FugBOKTauH54KMU+DR9UlgYNi4p3J/447BRatzJcd3CsFCjqkJFj+RVQEmTh6fNqces5S4ZxFROlA= 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 10/26/26 16:20, Lance Yang wrote: > collapse_file() can call page_cache_sync_readahead() while still holding > source folios locked. If truncate holds mapping->invalidate_lock > exclusively and waits for one of those folios, readahead waits for > invalidate_lock and neither side can make progress. > > We need to release those folio locks before starting readahead. On a page > cache miss, roll back first, populate the collapse range, and retry once. > Doing readahead after rollback avoids an extra pass when all folios are > already present. If another miss occurs on retry, give up rather than keep > retrying while truncate or reclaim removes folios. > > Keep page_cache_sync_readahead() and wait for read I/O with > filemap_lock_folio(), releasing each folio before moving to the next. The > existing uptodate check during collapse still handles read errors. > > Shmem uses shmem_get_folio() for swapin and fallocated folios without > taking mapping->invalidate_lock, so it is unaffected. > > Reported-by: syzbot+16bf7cd0ebeb1de93aa5@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=16bf7cd0ebeb1de93aa5 > Fixes: 730633f0b7f9 ("mm: Protect operations adding pages to page cache with invalidate_lock") > Cc: stable@vger.kernel.org > Signed-off-by: Lance Yang > --- As discussed, this needs some rework afterwards. For now this should fix the problem Acked-by: David Hildenbrand (Arm) -- Cheers, David