From: Eric Sandeen <sandeen@sandeen.net>
To: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: "J. Bruce Fields" <bfields@fieldses.org>,
Christoph Hellwig <hch@infradead.org>,
Masayoshi Mizuma <msys.mizuma@gmail.com>,
Theodore Ts'o <tytso@mit.edu>,
Andreas Dilger <adilger.kernel@dilger.ca>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>,
linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-xfs <linux-xfs@vger.kernel.org>
Subject: Re: [PATCH] fs: i_version mntopt gets visible through /proc/mounts
Date: Wed, 17 Jun 2020 12:55:24 -0500 [thread overview]
Message-ID: <8f0df756-4f71-9d96-7a52-45bf51482556@sandeen.net> (raw)
In-Reply-To: <20200617172456.GP11245@magnolia>
On 6/17/20 12:24 PM, Darrick J. Wong wrote:
> On Wed, Jun 17, 2020 at 12:14:28PM -0500, Eric Sandeen wrote:
>>
>>
>> On 6/17/20 10:58 AM, J. Bruce Fields wrote:
>>> On Wed, Jun 17, 2020 at 01:03:14AM -0700, Christoph Hellwig wrote:
>>>> On Tue, Jun 16, 2020 at 04:21:23PM -0400, Masayoshi Mizuma wrote:
>>>>> From: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
>>>>>
>>>>> /proc/mounts doesn't show 'i_version' even if iversion
>>>>> mount option is set to XFS.
>>>>>
>>>>> iversion mount option is a VFS option, not ext4 specific option.
>>>>> Move the handler to show_sb_opts() so that /proc/mounts can show
>>>>> 'i_version' on not only ext4 but also the other filesystem.
>>>>
>>>> SB_I_VERSION is a kernel internal flag. XFS doesn't have an i_version
>>>> mount option.
>>>
>>> It probably *should* be a kernel internal flag, but it seems to work as
>>> a mount option too.
>>
>> Not on XFS AFAICT:
>>
>> [600280.685810] xfs: Unknown parameter 'i_version'
>
> Yeah, because the mount option is 'iversion', not 'i_version'. Even if
unless you're ext4:
{Opt_i_version, "i_version"},
ok "iversion" is what mount(8) takes and translates into MS_I_VERSION (thanks Darrick)
# strace -vv -emount mount -oloop,iversion fsfile mnt
mount("/dev/loop0", "/tmp/mnt", "xfs", MS_I_VERSION, NULL) = 0
FWIW, mount actually seems to pass what it finds in /proc/mounts back in on remount for ext4:
# strace -vv -emount mount -o remount mnt
mount("/dev/loop0", "/tmp/mnt", 0x55bfcbdca150, MS_REMOUNT|MS_RELATIME, "seclabel,i_version,data=ordered") = 0
but it still looks unhandled on remount. Perhaps if /proc/mounts exposed
"iversion" (not "i_version") then mount -o remount would DTRT.
-Eric
> you were going to expose the flag state in /proc/mounts, the text string
> should match the mount option.
>
>> so we can't be exporting "mount options" for xfs that aren't actually
>> going to be accepted by the filesystem.
>>
>>> By coincidence I've just been looking at a bug report showing that
>>> i_version support is getting accidentally turned off on XFS whenever
>>> userspace does a read-write remount.
>>>
>>> Is there someplace in the xfs mount code where it should be throwing out
>>> SB_I_VERSION?
>>
>> <cc xfs list>
>>
>> XFS doesn't manipulate that flag on remount. We just turn it on by default
>> for modern filesystem formats:
>>
>> /* version 5 superblocks support inode version counters. */
>> if (XFS_SB_VERSION_NUM(&mp->m_sb) == XFS_SB_VERSION_5)
>> sb->s_flags |= SB_I_VERSION;
>>
>> Also, this behavior doesn't seem unique to xfs:
>>
>> # mount -o loop,i_version fsfile test_iversion
>> # grep test_iversion /proc/mounts
>> /dev/loop4 /tmp/test_iversion ext4 rw,seclabel,relatime,i_version 0 0
>> # mount -o remount test_iversion
>> # grep test_iversion /proc/mounts
>> /dev/loop4 /tmp/test_iversion ext4 rw,seclabel,relatime 0 0
>> # uname -a
>> Linux <hostname> 5.7.0-rc4+ #7 SMP Wed Jun 10 14:01:34 EDT 2020 x86_64 x86_64 x86_64 GNU/Linux
>
> Probably because do_mount clears it and I guess xfs don't re-enable
> it in any of their remount functions...
next prev parent reply other threads:[~2020-06-17 17:55 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-16 20:21 [PATCH] fs: i_version mntopt gets visible through /proc/mounts Masayoshi Mizuma
2020-06-17 8:03 ` Christoph Hellwig
2020-06-17 13:33 ` Masayoshi Mizuma
2020-06-17 15:58 ` J. Bruce Fields
2020-06-17 17:14 ` Eric Sandeen
2020-06-17 17:24 ` Darrick J. Wong
2020-06-17 17:55 ` Eric Sandeen [this message]
2020-06-17 18:18 ` J. Bruce Fields
2020-06-17 18:28 ` Eric Sandeen
2020-06-17 18:45 ` J. Bruce Fields
2020-06-18 1:30 ` Masayoshi Mizuma
2020-06-18 1:44 ` Darrick J. Wong
2020-06-18 3:33 ` Masayoshi Mizuma
2020-06-18 3:05 ` Dave Chinner
2020-06-18 3:45 ` Masayoshi Mizuma
2020-06-18 22:39 ` Dave Chinner
2020-06-19 2:20 ` J. Bruce Fields
2020-06-19 2:44 ` Dave Chinner
2020-06-19 12:04 ` Jeff Layton
2020-06-19 20:40 ` J. Bruce Fields
2020-06-19 22:10 ` Dave Chinner
2020-06-19 22:28 ` J. Bruce Fields
2020-06-20 1:49 ` Dave Chinner
2020-06-20 1:56 ` J. Bruce Fields
2020-06-20 17:00 ` Eric Sandeen
2020-06-20 17:09 ` J. Bruce Fields
2020-06-20 23:54 ` Dave Chinner
2020-06-22 21:26 ` J. Bruce Fields
2020-06-22 22:03 ` Dave Chinner
2020-06-19 13:17 ` Christoph Hellwig
2020-07-13 23:45 ` Eric Sandeen
2020-07-14 8:30 ` Christoph Hellwig
2020-07-14 20:26 ` Eric Sandeen
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