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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 56683C04FE0 for ; Wed, 9 Aug 2023 17:59:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230419AbjHIR7g (ORCPT ); Wed, 9 Aug 2023 13:59:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35720 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229484AbjHIR7f (ORCPT ); Wed, 9 Aug 2023 13:59:35 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EAD88171D; Wed, 9 Aug 2023 10:59:34 -0700 (PDT) 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 6E68B64364; 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 Cc: Jan Kara , Alexander Viro , Christian Brauner , Eric Van Hensbergen , Latchesar Ionkov , Dominique Martinet , Christian Schoenebeck , David Howells , Marc Dionne , Chris Mason , Josef Bacik , David Sterba , Xiubo Li , Ilya Dryomov , Jan Harkes , coda@cs.cmu.edu, Tyler Hicks , Gao Xiang , Chao Yu , Yue Hu , Jeffle Xu , Namjae Jeon , Sungjong Seo , Jan Kara , Theodore Ts'o , Andreas Dilger , Jaegeuk Kim , Miklos Szeredi , Bob Peterson , Andreas Gruenbacher , Greg Kroah-Hartman , Tejun Heo , Trond Myklebust , Anna Schumaker , Konstantin Komarov , Mark Fasheh , Joel Becker , Joseph Qi , Mike Marshall , Martin Brandenburg , Luis Chamberlain , Kees Cook , Iurii Zaikin , Steve French , Paulo Alcantara , Ronnie Sahlberg , Shyam Prasad N , Tom Talpey , Sergey Senozhatsky , Richard Weinberger , Hans de Goede , Hugh Dickins , Andrew Morton , Amir Goldstein , "Darrick J. Wong" , Benjamin Coddington , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, v9fs@lists.linux.dev, linux-afs@lists.infradead.org, linux-btrfs@vger.kernel.org, ceph-devel@vger.kernel.org, codalist@telemann.coda.cs.cmu.edu, ecryptfs@vger.kernel.org, linux-erofs@lists.ozlabs.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, cluster-devel@redhat.com, linux-nfs@vger.kernel.org, ntfs3@lists.linux.dev, ocfs2-devel@lists.linux.dev, devel@lists.orangefs.org, linux-cifs@vger.kernel.org, samba-technical@lists.samba.org, linux-mtd@lists.infradead.org, linux-mm@kvack.org, linux-unionfs@vger.kernel.org, linux-xfs@vger.kernel.org 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 Precedence: bulk List-ID: X-Mailing-List: ceph-devel@vger.kernel.org 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 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 us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 95927C04A94 for ; Wed, 9 Aug 2023 17:59:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1691603985; h=from:from:sender:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:list-id:list-help: list-unsubscribe:list-subscribe:list-post; bh=pzqYMc+IEe2Qk50ppvLbU6FnbUB8bOTvzSCY1iZtNg8=; b=amMQH6cTyJbnpWqQk4RPU+c+PscVAAEplBZW8Sj2my/aAnzh8cRQBW5gwwfQeuQWQEpgBI EJhMqYfVp2kJBZYO6LcOtc6IDx29zPJoYfyCXXbd1urfeXpWJYeL5EgXQU3m5nDHqHogR3 gUzVB4nsR+q7tXEiBv5HS7aTyYWbCTY= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-261-oq9l9ke1PdCRGbyMOBRpgg-1; Wed, 09 Aug 2023 13:59:41 -0400 X-MC-Unique: oq9l9ke1PdCRGbyMOBRpgg-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 8D277800159; Wed, 9 Aug 2023 17:59:40 +0000 (UTC) Received: from mm-prod-listman-01.mail-001.prod.us-east-1.aws.redhat.com (unknown [10.30.29.100]) by smtp.corp.redhat.com (Postfix) with ESMTP id 83095492C13; Wed, 9 Aug 2023 17:59:39 +0000 (UTC) Received: from mm-prod-listman-01.mail-001.prod.us-east-1.aws.redhat.com (localhost [IPv6:::1]) by mm-prod-listman-01.mail-001.prod.us-east-1.aws.redhat.com (Postfix) with ESMTP id 416371946589; Wed, 9 Aug 2023 17:59:39 +0000 (UTC) Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) by mm-prod-listman-01.mail-001.prod.us-east-1.aws.redhat.com (Postfix) with ESMTP id 7C4051946588 for ; Wed, 9 Aug 2023 17:59:38 +0000 (UTC) Received: by smtp.corp.redhat.com (Postfix) id 2BE9040C2077; Wed, 9 Aug 2023 17:59:38 +0000 (UTC) Received: from mimecast-mx02.redhat.com (mimecast10.extmail.prod.ext.rdu2.redhat.com [10.11.55.26]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 249A840C2076 for ; Wed, 9 Aug 2023 17:59:38 +0000 (UTC) Received: from us-smtp-1.mimecast.com (us-smtp-delivery-1.mimecast.com [205.139.110.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 091BB1C05AF7 for ; Wed, 9 Aug 2023 17:59:38 +0000 (UTC) Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-292-ZoF8INdHMpeO8Dr-_vfsSg-1; Wed, 09 Aug 2023 13:59:36 -0400 X-MC-Unique: ZoF8INdHMpeO8Dr-_vfsSg-1 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) Message-ID: 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> User-Agent: Evolution 3.48.4 (3.48.4-1.fc38) MIME-Version: 1.0 X-Mimecast-Impersonation-Protect: Policy=CLT - Impersonation Protection Definition; Similar Internal Domain=false; Similar Monitored External Domain=false; Custom External Domain=false; Mimecast External Domain=false; Newly Observed Domain=false; Internal User Name=false; Custom Display Name List=false; Reply-to Address Mismatch=false; Targeted Threat Dictionary=false; Mimecast Threat Dictionary=false; Custom Threat Dictionary=false X-Scanned-By: MIMEDefang 3.1 on 10.11.54.1 Subject: Re: [Cluster-devel] [PATCH v7 05/13] fat: make fat_update_time get its own timestamp X-BeenThere: cluster-devel@redhat.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: "\[Cluster devel\]" 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 , Miklos Szeredi , Richard Weinberger , Mark Fasheh , linux-unionfs@vger.kernel.org, Hugh Dickins , 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, Chao Yu , Josef Bacik , Tom Talpey , Tejun Heo , Alexander Viro , Ronnie Sahlberg , David Sterba , Jaegeuk Kim , ceph-devel@vger.kernel.org, Xiubo Li , Gao Xiang , 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 , Jeffle Xu , devel@lists.orangefs.org, Anna Schumaker , Jan Kara , 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: cluster-devel-bounces@redhat.com Sender: "Cluster-devel" X-Scanned-By: MIMEDefang 3.1 on 10.11.54.10 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: kernel.org Content-Type: text/plain; charset="ISO-8859-15" Content-Transfer-Encoding: quoted-printable 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 > -=09if ((flags & S_VERSION) && inode_maybe_inc_iversion(inode, false)) > +=09if ((flags & (S_VERSION|S_CTIME|S_MTIME)) && inode_maybe_inc_iversion= (inode, false)) > =09=09dirty_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 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 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.sourceforge.net (lists.sourceforge.net [216.105.38.7]) (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 6C6CAC0015E for ; Wed, 9 Aug 2023 17:59:45 +0000 (UTC) Received: from [127.0.0.1] (helo=sfs-ml-2.v29.lw.sourceforge.com) by sfs-ml-2.v29.lw.sourceforge.com with esmtp (Exim 4.95) (envelope-from ) id 1qTnTD-0002FJ-Um; Wed, 09 Aug 2023 17:59:42 +0000 Received: from [172.30.20.202] (helo=mx.sourceforge.net) by sfs-ml-2.v29.lw.sourceforge.com with esmtps (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.95) (envelope-from ) id 1qTnTC-0002F7-8v for linux-f2fs-devel@lists.sourceforge.net; Wed, 09 Aug 2023 17:59:41 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sourceforge.net; s=x; h=MIME-Version:Content-Transfer-Encoding:Content-Type :References:In-Reply-To:Date:Cc:To:From:Subject:Message-ID:Sender:Reply-To: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=ZJYkWobh6KEl/9KBdVbAet9rd5oJbzUXYYantWtSSuI=; b=TnvDKsf+fc1lNr6EG8va5Qk9Dj 9p24eqfL4nKVMHTwpQzcVUay47kT/eMoMRtbC+hoG1UqDOHBDgVmwbdkBT71TtEZUmVgtyCR4LYa/ LsZHPHecSjb9ru7M5LpH7jZM0ToemMGiUQB2xL0FEQKTluauu4QVRWUeAsGkry0a+19c=; DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sf.net; s=x ; h=MIME-Version:Content-Transfer-Encoding:Content-Type:References: In-Reply-To:Date:Cc:To:From:Subject:Message-ID:Sender:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=ZJYkWobh6KEl/9KBdVbAet9rd5oJbzUXYYantWtSSuI=; b=Lrq9HTFe6OkJ+UL1VeBzm+kNkZ BAjmnSxsIQuRnexl9NBwlVjtMi/FVMZWCMkAU2HQOGM31K+1O0IwTHkYy9c5Ma5v+FIsDdMKewe1Q rpi4kog5J6Zrw8sw3C5aNZFgSaj2TZLWGz3tF5BIARM8lGwOBHE7g9L8D8Naiq+Nii4Y=; Received: from dfw.source.kernel.org ([139.178.84.217]) by sfi-mx-2.v28.lw.sourceforge.com with esmtps (TLS1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.95) id 1qTnTA-0003T7-Ce for linux-f2fs-devel@lists.sourceforge.net; Wed, 09 Aug 2023 17:59:41 +0000 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: 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> User-Agent: Evolution 3.48.4 (3.48.4-1.fc38) MIME-Version: 1.0 X-Headers-End: 1qTnTA-0003T7-Ce Subject: Re: [f2fs-dev] [PATCH v7 05/13] fat: make fat_update_time get its own timestamp X-BeenThere: linux-f2fs-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: 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 , Gao Xiang , 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 , Jeffle Xu , 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 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net On Thu, 2023-08-10 at 02:44 +0900, OGAWA Hirofumi wrote: > Jeff Layton writes: > > > On Thu, 2023-08-10 at 00:17 +0900, OGAWA Hirofumi wrote: > > > Jan Kara writes: > > [...] > > > My mistake re: lazytime vs. relatime, but Jan is correct that this > > shouldn't break anything there. > > 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. > > > The logic in the revised generic_update_time is different because FAT is > > is a bit strange. fat_update_time does extra truncation on the timestamp > > 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. > > > > 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. > > > > generic_update_time is used across many filesystems so we need to ensure > > 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. > > > > Is there a particular case or flag combination you're concerned about > > here? > > Yes. Because FAT has strange timestamps that different granularity on > disk . This is why generic time truncation doesn't work for FAT. > > 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. > > - if ((flags & S_VERSION) && inode_maybe_inc_iversion(inode, false)) > + if ((flags & (S_VERSION|S_CTIME|S_MTIME)) && inode_maybe_inc_iversion(inode, false)) > dirty_flags |= I_DIRTY_SYNC; > 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. -- Jeff Layton _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel 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 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.lore.kernel.org (Postfix) with ESMTPS id 7BB7CC41513 for ; Wed, 9 Aug 2023 17:59:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Date:Cc:To:From:Subject:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=0LjKLj4VLQ35M6qQlCsuXGsiz5XqGjnObFgn4vWNoyg=; b=kuGkyawSVqFt+U BqZJlDGdHDN2NWkoThPpT9YRY9O77We7FEWrP6eB/Asf4UuRCdCBrThg4m9cgvNcAZXYkFcqhX9ky kkKKevs59agdZlW371U33gKLTFPB1m6uqYHKL4Yb6s+L8EJ6d1S2sEHvYNS+FZJzK6HX8B9jeLXnt olpRlEvzYaMR/vG+jtr6ausJHX1zGx9OfNxwWePOEQhKRGrcVm2s3cx7oSXpsljGQEPW+RllqEFGC /e7LaMkd1TlTeY/p/r1Ii7SgE7ixfXNJdVzP7lDX9/a9Ji53dEzM5Siqq2PGj/oYHYuuRMxJgpSgc vYzP8bQMDGCgWom25NJQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1qTnT7-005Z3t-37; Wed, 09 Aug 2023 17:59:37 +0000 Received: from dfw.source.kernel.org ([139.178.84.217]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1qTnT5-005Z2y-1A; Wed, 09 Aug 2023 17:59:36 +0000 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 Cc: Jan Kara , Alexander Viro , Christian Brauner , Eric Van Hensbergen , Latchesar Ionkov , Dominique Martinet , Christian Schoenebeck , David Howells , Marc Dionne , Chris Mason , Josef Bacik , David Sterba , Xiubo Li , Ilya Dryomov , Jan Harkes , coda@cs.cmu.edu, Tyler Hicks , Gao Xiang , Chao Yu , Yue Hu , Jeffle Xu , Namjae Jeon , Sungjong Seo , Jan Kara , Theodore Ts'o , Andreas Dilger , Jaegeuk Kim , Miklos Szeredi , Bob Peterson , Andreas Gruenbacher , Greg Kroah-Hartman , Tejun Heo , Trond Myklebust , Anna Schumaker , Konstantin Komarov , Mark Fasheh , Joel Becker , Joseph Qi , Mike Marshall , Martin Brandenburg , Luis Chamberlain , Kees Cook , Iurii Zaikin , Steve French , Paulo Alcantara , Ronnie Sahlberg , Shyam Prasad N , Tom Talpey , Sergey Senozhatsky , Richard Weinberger , Hans de Goede , Hugh Dickins , Andrew Morton , Amir Goldstein , "Darrick J. Wong" , Benjamin Coddington , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, v9fs@lists.linux.dev, linux-afs@lists.infradead.org, linux-btrfs@vger.kernel.org, ceph-devel@vger.kernel.org, codalist@telemann.coda.cs.cmu.edu, ecryptfs@vger.kernel.org, linux-erofs@lists.ozlabs.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, cluster-devel@redhat.com, linux-nfs@vger.kernel.org, ntfs3@lists.linux.dev, ocfs2-devel@lists.linux.dev, devel@lists.orangefs.org, linux-cifs@vger.kernel.org, samba-technical@lists.samba.org, linux-mtd@lists.infradead.org, linux-mm@kvack.org, linux-unionfs@vger.kernel.org, linux-xfs@vger.kernel.org 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> User-Agent: Evolution 3.48.4 (3.48.4-1.fc38) MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230809_105935_488374_A7CC1FBA X-CRM114-Status: GOOD ( 31.62 ) X-BeenThere: linux-mtd@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-mtd" Errors-To: linux-mtd-bounces+linux-mtd=archiver.kernel.org@lists.infradead.org On Thu, 2023-08-10 at 02:44 +0900, OGAWA Hirofumi wrote: > Jeff Layton writes: > > > On Thu, 2023-08-10 at 00:17 +0900, OGAWA Hirofumi wrote: > > > Jan Kara writes: > > [...] > > > My mistake re: lazytime vs. relatime, but Jan is correct that this > > shouldn't break anything there. > > 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. > > > The logic in the revised generic_update_time is different because FAT is > > is a bit strange. fat_update_time does extra truncation on the timestamp > > 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. > > > > 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. > > > > generic_update_time is used across many filesystems so we need to ensure > > 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. > > > > Is there a particular case or flag combination you're concerned about > > here? > > Yes. Because FAT has strange timestamps that different granularity on > disk . This is why generic time truncation doesn't work for FAT. > > 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. > > - if ((flags & S_VERSION) && inode_maybe_inc_iversion(inode, false)) > + if ((flags & (S_VERSION|S_CTIME|S_MTIME)) && inode_maybe_inc_iversion(inode, false)) > dirty_flags |= I_DIRTY_SYNC; > 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. -- Jeff Layton ______________________________________________________ Linux MTD discussion mailing list http://lists.infradead.org/mailman/listinfo/linux-mtd/