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b=WxxBrewlzT7ITVhnNCn8QnR0vavmA2xixsrBEvXdYbgkVDB6ep3o4zuQgehmNdiqvXQGLHhLcmjlcOzTKj0qoSxYCtfQWWU9bMc5hYzaE0QOacqD49yngxUyQkapbP1i3heLtMOLpluCogj3/pWAHVK8LdipiPw1XAtvVP41Q74= Received: from 30.74.144.121(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0WwWwVyP_1767748572 cluster:ay36) by smtp.aliyun-inc.com; Wed, 07 Jan 2026 09:16:12 +0800 Message-ID: <9c4b8d43-1c01-46f0-8e1e-435a19b8713b@linux.alibaba.com> Date: Wed, 7 Jan 2026 09:16:11 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/shmem: fix uninitialized folio in shmem_symlink To: Matthew Wilcox Cc: Brian Foster , Barry Song <21cnbao@gmail.com>, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Hugh Dickins , syzbot+178fff6149127421c2cc@syzkaller.appspotmail.com References: <20251224094027.65842-1-21cnbao@gmail.com> <2b12f63b-ceab-4d3e-a06f-f41e6b1b2d23@linux.alibaba.com> From: Baolin Wang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: A9ED1C0007 X-Rspamd-Server: rspam03 X-Stat-Signature: oq4bgo7bap6s5gzjqwqdpjknyy5xzknr X-Rspam-User: X-HE-Tag: 1767748576-937906 X-HE-Meta: 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 7HulIbJj iGxitZ/Vm/0GEYT0LIgbcGCgIPNa2W8ThnY/sXGQWXFpqtK0djFp5uUAtx0pXFqsY3+ZpzLxHEZCKGadEUAY9fMel0qAIObpXRv5dWA1y8AB9OGC1VJGJwkDk4M1MS/cmdi8faRE9Aw5pRik7z2hh/CX/fq4ffJomf7FHrgKRzJzA3h1h2eRJyWrDwwTZPf4hHjxfdY2R0odVdKKIF1z4LzVL9qFWonNXSddlTQOSHzD5iET1qwfEe+TaSKT+a1ac2JuEUrlH6fzHkiC18uBvqInE6h9+9ECyprm1XPtcE9K4u/mwrocKHdZ4dBX8H7Mvf3Xk7ZowzBiIppFZO0EzRxoUHzqu/SFJL0xE+YiGUFDH+xzcMMecFeKlsudd3SkAJujqoWlBXjTUBP1OqZny8FvmFtSfWODH73OGj8lRFOK43D8wGcBG3M4ODtbq7OOhWDUVCGcyI/LgMOz+WtiztWduE3K/ZhQ9DG05 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 1/7/26 2:46 AM, Matthew Wilcox wrote: > On Tue, Jan 06, 2026 at 11:47:44AM +0800, Baolin Wang wrote: >> Why I prefer Barry's fix: First, the symlink folio is marked Uptodate after >> copying the symlink name, but the whole folio hasn’t been initialized, which >> seems unreasonable to me. Second, as I said before, using the 'PG_owner_2' >> flag to mark this uncommon case doesn’t seem worthwhile. Currently, IIUC the >> 'PG_owner_2' is only used by btrfs; if we ever want to remove the >> 'PG_owner_2', this uncommon symlink case shouldn’t block its removal. > > PG_owner_2 is aliased with PG_mappedtodisk [1], so it's used by every > filesystem which uses buffer_heads (whether mentioned in that filesystem > or not). btrfs was switched from using private_2 to using owner_2 > a little over a year ago. PG_owner_2 is not on the list of flags to be > removed; that's PG_private, PG_private_2 and PG_reserved. OK. Thanks for the explanation. I understand the plan.