From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 69B6927F01E; Tue, 14 Oct 2025 18:22:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760466150; cv=none; b=s1xmnAQe+ds9IUb73OTd0dWvWsSVScdcT/hLXB36xVOgAvOjkabTD/Fuyoq28Cwn2xcSOh94Ugp/d+cZUXGGEMHerre7J6cjBLrFXyQGGG3KqTnF8N8zarZWIOIhBRy34BN3FtD3DniaKi7a7jdq3xfcWD1uPm92VrX/nXCuJFk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760466150; c=relaxed/simple; bh=khlNisH8i2Ud4Fkv3yboxw0azYLQViia2aglBjxVop0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ZzjBQ+aI9Uypif4iflKdf7s8osTJUsh9NdL4IV/sBFwmRu3tXBPnncNvKs10dRQAKloIIZSiQ6aqey+kq3vN0L8rdUcJOgz6MR6SwgVfgwH8X19A9KZZNXWVGGkGpnwOln8dn1qIZb9bEyC2Nw+SgnAH0PiRBHaHlAwVw15WDwI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=YCeelzAi; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="YCeelzAi" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CEA6FC4CEE7; Tue, 14 Oct 2025 18:22:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1760466149; bh=khlNisH8i2Ud4Fkv3yboxw0azYLQViia2aglBjxVop0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=YCeelzAi4il5II6IqjasPsEDpq2aeQMC+tk37SVCi8T2Ppu84kRj/4n7+SEG9CfUi bNCNsR7EZ+s3ByhN73AuPNf4jsIZ04J/L8Yr8GM/XcNVyxRHEWr3K856/iBf8zdHsV DKwWEIva1/9IKVl7Uq6cVDJQ+NZUIpo5KHsKKL0L6hTvyi1dV8cmdVtGMCC5enBg22 zwP8kwVkdkpR6D3M+L009s2de0ztI2bG7LjD6lNKcQDdzhkAXd5HR1rei10/hDCmKT FaAnR8VK8Twh8fj9k8PZrw8bz44MdbsOUtBqlYvLDcAiFaziyDLU/qG+ous/znQpf4 4c8ANYnwvO0lw== Date: Tue, 14 Oct 2025 11:22:29 -0700 From: "Darrick J. Wong" To: Oleksandr Natalenko Cc: linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, Carlos Maiolino , Pavel Reichl , Vlastimil Babka , Thorsten Leemhuis Subject: Re: [PATCH 1/2] xfs: quietly ignore deprecated mount options Message-ID: <20251014182229.GY6188@frogsfrogsfrogs> References: <20251013233229.GR6188@frogsfrogsfrogs> <2800646.mvXUDI8C0e@natalenko.name> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <2800646.mvXUDI8C0e@natalenko.name> On Tue, Oct 14, 2025 at 01:27:40PM +0200, Oleksandr Natalenko wrote: > Hello. > > On úterý 14. října 2025 1:32:29, středoevropský letní čas Darrick J. Wong wrote: > > From: Darrick J. Wong > > > > Apparently we can never deprecate mount options in this project, because > > it will invariably turn out that some foolish userspace depends on some > > behavior and break. From Oleksandr Natalenko: > > > > > In v6.18, the attr2 XFS mount option is removed. This may silently > > > break system boot if the attr2 option is still present in /etc/fstab > > > for rootfs. > > > > > > Consider Arch Linux that is being set up from scratch with / being > > > formatted as XFS. The genfstab command that is used to generate > > > /etc/fstab produces something like this by default: > > > > > > /dev/sda2 on / type xfs (rw,relatime,attr2,discard,inode64,logbufs=8,logbsize=32k,noquota) > > > > > > Once the system is set up and rebooted, there's no deprecation warning > > > seen in the kernel log: > > > > > > # cat /proc/cmdline > > > root=UUID=77b42de2-397e-47ee-a1ef-4dfd430e47e9 rootflags=discard rd.luks.options=discard quiet > > > > > > # dmesg | grep -i xfs > > > [ 2.409818] SGI XFS with ACLs, security attributes, realtime, scrub, repair, quota, no debug enabled > > > [ 2.415341] XFS (sda2): Mounting V5 Filesystem 77b42de2-397e-47ee-a1ef-4dfd430e47e9 > > > [ 2.442546] XFS (sda2): Ending clean mount > > > > > > Although as per the deprecation intention, it should be there. > > > > > > Vlastimil (in Cc) suggests this is because xfs_fs_warn_deprecated() > > > doesn't produce any warning by design if the XFS FS is set to be > > > rootfs and gets remounted read-write during boot. This imposes two > > > problems: > > > > > > 1) a user doesn't see the deprecation warning; and > > > 2) with v6.18 kernel, the read-write remount fails because of unknown > > > attr2 option rendering system unusable: > > > > > > systemd[1]: Switching root. > > > systemd-remount-fs[225]: /usr/bin/mount for / exited with exit status 32. > > > > > > # mount -o rw / > > > mount: /: fsconfig() failed: xfs: Unknown parameter 'attr2'. > > > > > > Thorsten (in Cc) suggested reporting this as a user-visible regression. > > > > > > From my PoV, although the deprecation is in place for 5 years already, > > > it may not be visible enough as the warning is not emitted for rootfs. > > > Considering the amount of systems set up with XFS on /, this may > > > impose a mass problem for users. > > > > > > Vlastimil suggested making attr2 option a complete noop instead of > > > removing it. > > > > IOWs, the initrd mounts the root fs with (I assume) no mount options, > > and mount -a remounts with whatever options are in fstab. However, > > XFS doesn't complain about deprecated mount options during a remount, so > > technically speaking we were not warning all users in all combinations > > that they were heading for a cliff. > > > > Gotcha!! > > > > Now, how did 'attr2' get slurped up on so many systems? The old code > > would put that in /proc/mounts if the filesystem happened to be in attr2 > > mode, even if user hadn't mounted with any such option. IOWs, this is > > because someone thought it would be a good idea to advertise system > > state via /proc/mounts. > > > > The easy way to fix this is to reintroduce the four mount options but > > map them to a no-op option that ignores them, and hope that nobody's > > depending on attr2 to appear in /proc/mounts. (Hint: use the fsgeometry > > ioctl). > > > > Lessons learned: > > > > 1. Don't expose system state via /proc/mounts; the only strings that > > ought to be there are options *explicitly* provided by the user. > > 2. Never tidy, it's not worth the stress and irritation. > > > > Reported-by: oleksandr@natalenko.name > > Reported-by: vbabka@suse.cz > > Cc: # v6.18-rc1 > > Fixes: b9a176e54162f8 ("xfs: remove deprecated mount options") > > Signed-off-by: "Darrick J. Wong" > > --- > > fs/xfs/xfs_super.c | 13 +++++++++++-- > > 1 file changed, 11 insertions(+), 2 deletions(-) > > > > diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c > > index e85a156dc17d16..e1df41991fccc3 100644 > > --- a/fs/xfs/xfs_super.c > > +++ b/fs/xfs/xfs_super.c > > @@ -102,7 +102,7 @@ static const struct constant_table dax_param_enums[] = { > > * Table driven mount option parser. > > */ > > enum { > > - Opt_logbufs, Opt_logbsize, Opt_logdev, Opt_rtdev, > > + Opt_quietlyignore, Opt_logbufs, Opt_logbsize, Opt_logdev, Opt_rtdev, > > Opt_wsync, Opt_noalign, Opt_swalloc, Opt_sunit, Opt_swidth, Opt_nouuid, > > Opt_grpid, Opt_nogrpid, Opt_bsdgroups, Opt_sysvgroups, > > Opt_allocsize, Opt_norecovery, Opt_inode64, Opt_inode32, > > @@ -115,6 +115,14 @@ enum { > > }; > > > > static const struct fs_parameter_spec xfs_fs_parameters[] = { > > + /* > > + * These mount options were advertised in /proc/mounts even if the > > + * filesystem had not been mounted with that option. Quietly ignore > > + * them to avoid breaking scripts that captured /proc/mounts. > > + */ > > + fsparam_flag("attr", Opt_quietlyignore), > > Should have been "attr2" here I suppose. Yeah, sorry about that, will fix for v2. Maybe I should use fs_param_deprecated here too. --D > Thanks. > > > + fsparam_flag("noattr2", Opt_quietlyignore), > > + > > fsparam_u32("logbufs", Opt_logbufs), > > fsparam_string("logbsize", Opt_logbsize), > > fsparam_string("logdev", Opt_logdev), > > @@ -1408,6 +1416,8 @@ xfs_fs_parse_param( > > return opt; > > > > switch (opt) { > > + case Opt_quietlyignore: > > + return 0; > > case Opt_logbufs: > > parsing_mp->m_logbufs = result.uint_32; > > return 0; > > @@ -1528,7 +1538,6 @@ xfs_fs_parse_param( > > xfs_mount_set_dax_mode(parsing_mp, result.uint_32); > > return 0; > > #endif > > - /* Following mount options will be removed in September 2025 */ > > case Opt_max_open_zones: > > parsing_mp->m_max_open_zones = result.uint_32; > > return 0; > > > > -- > Oleksandr Natalenko, MSE