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@xxxxxxxxxxxxxx>
>>>
>>> /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'
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
-Eric
> Ideally there'd be entirely different fields for mount options and
> internal feature flags. But I don't know, maybe SB_I_VERSION is the
> only flag we have like this.
>
> --b.
>
