On Wed, Jun 17, 2020 at 12:55:24PM -0500, Eric Sandeen wrote:
> 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@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'
> >
> > 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.
I'd rather just eliminate the option, to the extent possible.
It was only ever a mount option since it caused a performance regression
in some filesystems, but I *think* that was addressed by Jeff Layton's
work (f02a9ad1f15d "fs: handle inode->i_version more efficiently").
XFS in particular is just using this flag to tell knfsd that it should
use i_version. I don't think it was really intended for userspace to be
able to turn this off.
--b.
