From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 D7D914C6C; Tue, 7 Oct 2025 05:10:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.133 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759813834; cv=none; b=JZu+c2Nn5DZj4qioVvkGUt9xGytE4A8HZ1qXa65ogfZViUX3wBtWX5G2cJHO4V1V4IauNamg1EpE/ogrknsV/uBZoNymVvThxPOuwRy+OK/VuwySBpGotWH+8VPiUR7Ks9Th78ubTSzvkaHYiamcjF6yl7yGLDmuiDR5QYcC4Bs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759813834; c=relaxed/simple; bh=RTEiExciP8/R4hGtwF66A3na/tFaTqWtPRoTMHyhGVQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=VwUkE+fCJ5ApOxnd6ra527kVparPmuQ3r5xKC7mJp/dokwMLHZ19Y+58P0KVuF/110qLQCwKryT+gbweIts7a6bP5C3vy4SdJHdEnAZsn+v37oaH7wNLXS3Xi511AuK0IqMNqTkWZgvHXlG6Yy6mWXV022mWBhgUoXUsnE8kXwY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=z6Lu+2ZJ; arc=none smtp.client-ip=198.137.202.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="z6Lu+2ZJ" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=H7+kqJdrOtlrnhWTU+oo8aVXwAXn0Jj3b2J0DwZYPa4=; b=z6Lu+2ZJWEM4PGwIYsZF4X6mp/ zeB3ivMcxgMAynWW1oqk4lWBLhDDWqZUwpdnwJBKFDZx5abS6bg78IZhNjWgAStDOI4cEthI/P1ty gyW1Ml8U20NvfCCO3bJY10DMRTSpW6IO+DPVwQkEIl/p1tlDCSWKaENhAoXTn/8iHARjy5m7EIoTB Anlv/Z/j/KWyohmaYSFtgbO40W8kHO7HPj8fBl5dNgJa53Ox2ULHwvgEME6XlH+JZmVfiSvjX/9Pv xUMD4UYoNl8D1ijFrZ5B1AwnB61+tE/iBxAjala8PvY9k5Bn9GMn5vvGjlFhUjIk2z0osv7OCbTP5 sx/DQ7dg==; Received: from hch by bombadil.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1v5zy4-00000001GzI-1bbO; Tue, 07 Oct 2025 05:10:32 +0000 Date: Mon, 6 Oct 2025 22:10:32 -0700 From: Christoph Hellwig To: Dave Chinner Cc: Christoph Hellwig , Pavel Emelyanov , linux-fsdevel@vger.kernel.org, "Raphael S . Carvalho" , linux-api@vger.kernel.org, linux-xfs@vger.kernel.org Subject: Re: [PATCH] fs: Propagate FMODE_NOCMTIME flag to user-facing O_NOCMTIME Message-ID: References: <20251003093213.52624-1-xemul@scylladb.com> 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: X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html On Mon, Oct 06, 2025 at 09:06:40AM +1100, Dave Chinner wrote: > If you don't care about accurate c/mtime, then mount the filesystem > with '-o lazytime' to degrade c/mtime updates to "eventual > consistency" behaviour for IO operations. Exactly. > Lazytime updates can generally be done in a non-blocking manner > right now (someone raised that in the context of io-uring on #xfs > about a month ago), but the NOWAIT behaviour for timestamp updates > is done at a higher level in the VFS and does not take into account > filesystem specific non-blocking lazytime updates at all. If we > push the NOWAIT checking behaviour down to the filesystem, we can do > this. We might not even have to push it out, but just make the VFS/rw helper check aware of lazytime. Either way currently even a lazytime timestampt update will cause a write to block, which renders the nowait writes pretty useless on anything but block devices.