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[90.171.92.67]) by smtp.gmail.com with ESMTPSA id j15-20020a5d464f000000b003012030a0c6sm4756925wrs.18.2023.05.21.06.57.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 21 May 2023 06:57:35 -0700 (PDT) From: =?UTF-8?q?Joan=20Bruguera=20Mic=C3=B3?= To: zhengqi.arch@bytedance.com Cc: Andrew Morton , Roman Gushchin , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: shrinkers: fix race condition on debugfs cleanup Date: Sun, 21 May 2023 13:57:33 +0000 Message-Id: <20230521135733.1076395-1-joanbrugueram@gmail.com> X-Mailer: git-send-email 2.40.1 In-Reply-To: <2d44a1bd-eb80-7724-ff4e-a0fc3bfd8b72@bytedance.com> References: <2d44a1bd-eb80-7724-ff4e-a0fc3bfd8b72@bytedance.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 507291C000F X-Stat-Signature: 5mfw5fgxydm1ktksj4ogs4nt7b7h9ua9 X-Rspam-User: X-HE-Tag: 1684677457-267592 X-HE-Meta: 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 oNg5vS4r wKwBxw7f3uaqcafkfmwDFeX+7uBSkDZAdMwXElQVVDuBHSV1s7Ua/LRs0sfbpB9wY3WjOAiewldWnu2RUF+n1bb4e0AIW0MPbpHklbrae452MbWsCxoOrmDq1feR3FVJsof2EXX+gdx3LmcLcuXhzYaM+wiwTFiWTLHAq6o58dRpAN9SNt2K5v8J4FyQrDkD6p+l2+d8wI4DWb9b3QiOErKa4OzKr0csCAHb8toKBeoIEtlQ6zJKKLpYdwtdPRiAqwd0tBS7BqAtTcBLckRXVrdi+hHEYbw286Sh9wPMlD35hxgYacUl4QhZLuyvcDG8sDnHSu9mEvL95TSlLULKCPhx+lYcLBf4odZSYguaJCRK2hFNQvRNxjJrOhaZvJAI1ach3XeLw5vzIG8qFyk26eP0grh78Rb4y0+sjrzUbgDZ1z3gao4iSW5vLQgBF3d9k+ij22rLIlgCODXxZKYnEnaYnZQ== 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: On 2023/5/3 13:37, Qi Zheng wrote: > > +void shrinker_debugfs_remove(struct dentry *debugfs_entry, int debugfs_id) > > +{ > > It would be better to add a check: > > if (!debugfs_entry) > return; > > > + debugfs_remove_recursive(debugfs_entry); > > + ida_free(&shrinker_debugfs_ida, debugfs_id); > > +} As a practical matter, both `debugfs_remove_recursive(NULL)` and `ida_free(_, -1);` are documented as no-ops, see: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/fs/debugfs/inode.c?id=0dd2a6fb1e34d6dcb96806bc6b111388ad324722#n748 https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=fc82bbf4dede758007763867d0282353c06d1121 Sorry for the late reply (the patch already reached the mainline tree).