[PATCH] xfs: preserve inode versioning across remounts

Eric Sandeen
2020-07-14T22:11:40Z

The MS_I_VERSION mount flag is exposed via the VFS, as documented
in the mount manpages etc; see the iversion and noiversion mount
options in mount(8).

As a result, mount -o remount looks for this option in /proc/mounts
and will only send the I_VERSION flag back in during remount it it
is present. Since it's not there, a remount will /remove/ the
I_VERSION flag at the vfs level, and iversion functionality is lost.

xfs v5 superblocks intend to always have i_version enabled; it is
set as a default at mount time, but is lost during remount for the
reasons above.

The generic fix would be to expose this documented option in
/proc/mounts, but since that was rejected, fix it up again in the
xfs remount path instead, so that at least xfs won't suffer from
this misbehavior.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
--

diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index 379cbff438bc..9239985571af 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1714,6 +1714,10 @@ xfs_fc_reconfigure(
int flags = fc->sb_flags;
int error;

+ /* version 5 superblocks always support version counters. */
+ if (XFS_SB_VERSION_NUM(&mp->m_sb) == XFS_SB_VERSION_5)
+ fc->sb_flags |= SB_I_VERSION;
+
error = xfs_fc_validate_params(new_mp);
if (error)
return error;