From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from zeniv.linux.org.uk (zeniv.linux.org.uk [62.89.141.173]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 796204A06; Wed, 23 Apr 2025 02:15:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=62.89.141.173 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745374555; cv=none; b=QUeKCIKLLl99gKzr76H6tKMEusIkz2myW4DG5k9umMtSoaGufFSxTbS4QMn3NMqkv6CYyKEwZIvp3/keC3iTNgf/75mdIbucfHiPUIjao0i2/Z1jQWN9EQ5jcOJTFtnlfQlw/S5INNqErZm6wQJSOWBq9NaAYRSl90Bu6lcCsOM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745374555; c=relaxed/simple; bh=uMWRC0mX21CCnzoFN25e4PYINhMXPjtIdAYTkYHgev4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=hHBF/chvm03utA5i86UJs6FKdspmZWnO5Zs90avdrI5rBXqEIUxkXBmM0EuTQ0J6KLmog6MnyXBJBKzfkr0Wop+TV9WGLwtdpVQoNYM92lBxozUbpS0JaOOLWEQLRXPkK9Ow42wiJ1LrbnuKQ2l6U/XbhHEAIukO/4nuqH5qwC8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zeniv.linux.org.uk; spf=none smtp.mailfrom=ftp.linux.org.uk; dkim=pass (2048-bit key) header.d=linux.org.uk header.i=@linux.org.uk header.b=S0S5x0ux; arc=none smtp.client-ip=62.89.141.173 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zeniv.linux.org.uk Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=ftp.linux.org.uk Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linux.org.uk header.i=@linux.org.uk header.b="S0S5x0ux" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=linux.org.uk; s=zeniv-20220401; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=3E/Nw19u36SXEMrl+EhZ1FRQFD9W6ajpHgqUEXxizb8=; b=S0S5x0ux1kKNgFqxHa37bpq5DH t2kAWHYs0Wr4cRxjnXBQjojyDP0uxgDGjGguxb7qVmZvq9upz2sbRsm9iwmJkJA3mykWZ3UWdsU3W 3AtvLxKB7kLYMjC7IrYhFh9HyVxqaHdzS4+KDIAtqBsBSXJffYAcQSQtAZM84RWwTMXsrnaRzdzae R1qhPAtCGgP4UL12L5oNubyBORGX5T5zsImb+tjTbKlO4kwByUWrmEhztdz8t6v4EzYvozF8hallV WnfmEpd8ZP749kgRP1nnM1x8Gv3Nu/XEXm3YnoPE+ZNSPd18RPEGV67evLTBfwI24Gy95JMEg+A+Y Ys61pPxA==; Received: from viro by zeniv.linux.org.uk with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1u7PeN-00000008IT2-44KK; Wed, 23 Apr 2025 02:15:48 +0000 Date: Wed, 23 Apr 2025 03:15:47 +0100 From: Al Viro To: Eric Chanudet Cc: Christian Brauner , Jan Kara , Sebastian Andrzej Siewior , Clark Williams , Steven Rostedt , Ian Kent , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, Alexander Larsson , Lucas Karpinski Subject: Re: [PATCH v4] fs/namespace: defer RCU sync for MNT_DETACH umount Message-ID: <20250423021547.GD2023217@ZenIV> References: <20250408210350.749901-12-echanude@redhat.com> <20250420055406.GS2023217@ZenIV> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: Al Viro On Tue, Apr 22, 2025 at 03:53:43PM -0400, Eric Chanudet wrote: > I'm not quite following. With umount -l, I thought there is no guaranty > that the file-system is shutdown. Doesn't "shutdown -r now" already > risks loses without any of these changes today? Busy filesystems might stay around after umount -l, for as long as they are busy. I.e. if there's a process with cwd on one of the affected filesystems, it will remain active until that process chdirs away or gets killed, etc. Assuming that your userland kills all processes before rebooting the kernel, everything ought to be shut down, TYVM... If not for that, the damn thing would be impossible to use safely...