From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 639DEC001E0 for ; Wed, 9 Aug 2023 17:59:44 +0000 (UTC) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20201202 header.b=meGLBjWx; dkim-atps=neutral Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4RLd9p5xXkz3bX1 for ; Thu, 10 Aug 2023 03:59:42 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20201202 header.b=meGLBjWx; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=kernel.org (client-ip=139.178.84.217; helo=dfw.source.kernel.org; envelope-from=jlayton@kernel.org; receiver=lists.ozlabs.org) Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4RLd9j0KrHz2xW7 for ; Thu, 10 Aug 2023 03:59:37 +1000 (AEST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 6A7C864360; Wed, 9 Aug 2023 17:59:34 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5192AC433C8; Wed, 9 Aug 2023 17:59:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1691603973; bh=xOe+Vz95v0qUUg0QOdDgphymvgENzflkYZLnMMULJfc=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=meGLBjWxluzaOBNuo8p0RmOQwgxUuFNZjvOIrqHLsT0YVm/rgDHwnHDJAx99/2L/o bhtobjoD8C6zGB5rdBPrQ785IrHaS3N4jJtTCfHc34NT0geG1/U9IaQFq3S4WuZ+t8 gzoPyUaQOM1ROi1uUYhm2o1c3laLFRiCZK/Lx2Wm4O80TbvA4CQm+kAJim7vyqiQ1H 44XIoEDh201mHVX5XJvZmC/E4Ogx1IKt/t/nyvPCcopm66rc52em9DBbgLmnfaxUsA shBRwdOI1wQgTtwpw38zZcoHm5c5hE7yNnsry2zyL7HvpHmwfSKALId/x1hyiXL2cb CwGZoXi1fmKhQ== Message-ID: Subject: Re: [PATCH v7 05/13] fat: make fat_update_time get its own timestamp From: Jeff Layton To: OGAWA Hirofumi Date: Wed, 09 Aug 2023 13:59:26 -0400 In-Reply-To: <87leek6rh1.fsf@mail.parknet.co.jp> References: <20230807-mgctime-v7-0-d1dec143a704@kernel.org> <20230807-mgctime-v7-5-d1dec143a704@kernel.org> <87msz08vc7.fsf@mail.parknet.co.jp> <52bead1d6a33fec89944b96e2ec20d1ea8747a9a.camel@kernel.org> <878rak8hia.fsf@mail.parknet.co.jp> <20230809150041.452w7gucjmvjnvbg@quack3> <87v8do6y8q.fsf@mail.parknet.co.jp> <2cb998ff14ace352a9dd553e82cfa0aa92ec09ce.camel@kernel.org> <87leek6rh1.fsf@mail.parknet.co.jp> Content-Type: text/plain; charset="ISO-8859-15" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.48.4 (3.48.4-1.fc38) MIME-Version: 1.0 X-BeenThere: linux-erofs@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Development of Linux EROFS file system List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Latchesar Ionkov , Martin Brandenburg , Konstantin Komarov , Jan Kara , "Darrick J. Wong" , Dominique Martinet , Christian Schoenebeck , ecryptfs@vger.kernel.org, Yue Hu , David Howells , Chris Mason , Andreas Dilger , Hans de Goede , Marc Dionne , linux-xfs@vger.kernel.org, linux-afs@lists.infradead.org, linux-mtd@lists.infradead.org, Mike Marshall , Paulo Alcantara , linux-cifs@vger.kernel.org, Eric Van Hensbergen , Andreas Gruenbacher , Miklos Szeredi , Richard Weinberger , Mark Fasheh , linux-unionfs@vger.kernel.org, Hugh Dickins , Benjamin Coddington , Tyler Hicks , cluster-devel@redhat.com, coda@cs.cmu.edu, linux-mm@kvack.org, Ilya Dryomov , Iurii Zaikin , Namjae Jeon , Trond Myklebust , codalist@telemann.coda.cs.cmu.edu, Shyam Prasad N , Amir Goldstein , Kees Cook , ocfs2-devel@lists.linux.dev, Josef Bacik , Tom Talpey , Tejun Heo , Alexander Viro , Ronnie Sahlberg , David Sterba , Jaegeuk Kim , ceph-devel@vger.kernel.org, Xiubo Li , Jan Harkes , Christian Brauner , linux-ext4@vger.kernel.org, Theodore Ts'o , Joseph Qi , Greg Kroah-Hartman , v9fs@lists.linux.dev, ntfs3@lists.linux.dev, samba-technical@lists.samba.org, linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, Steve French , Sergey Senozhatsky , Luis Chamberlain , devel@lists.orangefs.org, Anna Schumaker , Jan Kara , Bob Peterson , linux-fsdevel@vger.kernel.org, Andrew Morton , Sungjong Seo , linux-erofs@lists.ozlabs.org, linux-nfs@vger.kernel.org, linux-btrfs@vger.kernel.org, Joel Becker Errors-To: linux-erofs-bounces+linux-erofs=archiver.kernel.org@lists.ozlabs.org Sender: "Linux-erofs" On Thu, 2023-08-10 at 02:44 +0900, OGAWA Hirofumi wrote: > Jeff Layton writes: >=20 > > On Thu, 2023-08-10 at 00:17 +0900, OGAWA Hirofumi wrote: > > > Jan Kara writes: >=20 > [...] >=20 > > My mistake re: lazytime vs. relatime, but Jan is correct that this > > shouldn't break anything there. >=20 > Actually breaks ("break" means not corrupt fs, means it breaks lazytime > optimization). It is just not always, but it should be always for some > userspaces. >=20 > > The logic in the revised generic_update_time is different because FAT i= s > > is a bit strange. fat_update_time does extra truncation on the timestam= p > > that it is handed beyond what timestamp_truncate() does. > > fat_truncate_time is called in many different places too, so I don't > > feel comfortable making big changes to how that works. > >=20 > > In the case of generic_update_time, it calls inode_update_timestamps > > which returns a mask that shows which timestamps got updated. It then > > marks the dirty_flags appropriately for what was actually changed. > >=20 > > generic_update_time is used across many filesystems so we need to ensur= e > > that it's OK to use even when multigrain timestamps are enabled. Those > > haven't been enabled in FAT though, so I didn't bother, and left it to > > dirtying the inode in the same way it was before, even though it now > > fetches its own timestamps from the clock. Given the way that the mtime > > and ctime are smooshed together in FAT, that seemed reasonable. > >=20 > > Is there a particular case or flag combination you're concerned about > > here? >=20 > Yes. Because FAT has strange timestamps that different granularity on > disk . This is why generic time truncation doesn't work for FAT. >=20 > Well anyway, my concern is the only following part. In > generic_update_time(), S_[CM]TIME are not the cause of I_DIRTY_SYNC if > lazytime mode. >=20 > - if ((flags & S_VERSION) && inode_maybe_inc_iversion(inode, false)) > + if ((flags & (S_VERSION|S_CTIME|S_MTIME)) && inode_maybe_inc_iversion(i= node, false)) > dirty_flags |=3D I_DIRTY_SYNC; >=20 That would be wrong. The problem is that we're changing how update_time works: Previously, update_time was given a timestamp and a set of S_* flags to indicate which fields should be updated. Now, update_time is not given a timestamp. It needs to fetch it itself, but that subtly changes the meaning of the flags field. It now means "these fields needed to be updated when I last checked". The timestamp and i_version may now be different from when the flags field was set. This means that if any of S_CTIME/S_MTIME/S_VERSION were set that we need to attempt to update all 3 of them. They may now be different from the timestamp or version that we ultimately end up with. The above may look to you like it would always cause I_DIRTY_SYNC to be set on any ctime or mtime update, but inode_maybe_inc_iversion only returns true if it actually updated i_version, and it only does that if someone issued a ->getattr against the file since the last time it was updated. So, this shouldn't generate any more DIRTY_SYNC updates than it did before. --=20 Jeff Layton