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Received: from viro by zeniv.linux.org.uk with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1uyzPl-00000008YoM-1TR8; Wed, 17 Sep 2025 21:10:09 +0000 Date: Wed, 17 Sep 2025 22:10:09 +0100 From: Al Viro To: Max Kellermann Cc: Mateusz Guzik , linux-fsdevel , Linux Memory Management List , ceph-devel@vger.kernel.org Subject: Re: Need advice with iput() deadlock during writeback Message-ID: <20250917211009.GE39973@ZenIV> References: <4z3imll6zbzwqcyfl225xn3rc4mev6ppjnx5itmvznj2yormug@utk6twdablj3> <20250917201408.GX39973@ZenIV> <20250917203435.GA39973@ZenIV> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Queue-Id: 3AE28180008 X-Rspamd-Server: rspam05 X-Stat-Signature: 93fd4obsxdej1mzxuxdzg6kertijgcdx X-Rspam-User: X-HE-Tag: 1758143411-939912 X-HE-Meta: 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 vPHLs0Mu 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 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 Wed, Sep 17, 2025 at 10:36:48PM +0200, Max Kellermann wrote: > On Wed, Sep 17, 2025 at 10:34 PM Al Viro wrote: > > Suppose two threads do umount() on two different filesystems. The first > > one to flush picks *everything* you've delayed and starts handling that. > > The second sees nothing to do and proceeds to taking the filesystem > > it's unmounting apart, right under the nose of the first thread doing > > work on both filesystems... > > Each filesystem (struct ceph_fs_client) has its own inode_wq. Yes, but if (llist_add(&ci->async_llist, &delayed_ceph_iput_list)) schedule_delayed_work(&delayed_ceph_iput_work, 1); won't have anything to do with that.