Re: [PATCH RFC v2] xfs: Print XFS UUID on mount and umount events.

["Darrick J. Wong" <djwong@kernel.org>]

On Fri, May 21, 2021 at 11:03:11AM +0200, lukas@herbolt.com wrote:
> > Are you going to wire up fs uuid logging for the other filesystems that
> > support them?
> Well, I wasn't planning to but I can take a look on other FS as well
> Ext4 and Btrfs for start.
> 
> > What happens w.r.t. uuid disambiguation if someone uses a nouuid mount
> > to mount a filesystem with the same uuid as an already-mounted xfs?
> 
> I a not sure I understand the "nouuid mount". I don't think there can
> be XFS with empty uuid value in SB. And printing the message is independent
> on the mount method (mount UUID="" ...; mount /dev/sdX ...;).

I meant specifically:

mount /dev/mapper/fubar /mnt
<snapshot fubar to fubar.bak>

Oh no, I deleted something in fubar, let's retrieve it from fubar.bak!

mount /dev/mapper/fubar.bak /opt	# fails because same uuid as fubar
mount /dev/mapper/fubar.bak /opt -o nouuid

--D

> 
> 
> On 20.05.2021 17:23, Darrick J. Wong wrote:
> > On Wed, May 19, 2021 at 05:22:48PM +0200, Lukas Herbolt wrote:
> > > As of now only device names are printed out over __xfs_printk().
> > > The device names are not persistent across reboots which in case
> > > of searching for origin of corruption brings another task to properly
> > > identify the devices. This patch add XFS UUID upon every mount/umount
> > > event which will make the identification much easier.
> > 
> > A few questions....
> > 
> > Are you going to wire up fs uuid logging for the other filesystems that
> > support them?
> > 
> > What happens w.r.t. uuid disambiguation if someone uses a nouuid mount
> > to mount a filesystem with the same uuid as an already-mounted xfs?
> > 
> > The changes themselves look ok, but I'm wondering what the use case is
> > here.
> > 
> > --D
> > 
> > > 
> > > Signed-off-by: Lukas Herbolt <lukas@herbolt.com>
> > > ---
> > > V2: Drop void casts and fix long lines
> > > 
> > >  fs/xfs/xfs_log.c   | 10 ++++++----
> > >  fs/xfs/xfs_super.c |  2 +-
> > >  2 files changed, 7 insertions(+), 5 deletions(-)
> > > 
> > > diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
> > > index 06041834daa31..8f4f671fd80d5 100644
> > > --- a/fs/xfs/xfs_log.c
> > > +++ b/fs/xfs/xfs_log.c
> > > @@ -570,12 +570,14 @@ xfs_log_mount(
> > >  	int		min_logfsbs;
> > > 
> > >  	if (!(mp->m_flags & XFS_MOUNT_NORECOVERY)) {
> > > -		xfs_notice(mp, "Mounting V%d Filesystem",
> > > -			   XFS_SB_VERSION_NUM(&mp->m_sb));
> > > +		xfs_notice(mp, "Mounting V%d Filesystem %pU",
> > > +			   XFS_SB_VERSION_NUM(&mp->m_sb),
> > > +			   &mp->m_sb.sb_uuid);
> > >  	} else {
> > >  		xfs_notice(mp,
> > > -"Mounting V%d filesystem in no-recovery mode. Filesystem will be
> > > inconsistent.",
> > > -			   XFS_SB_VERSION_NUM(&mp->m_sb));
> > > +"Mounting V%d filesystem %pU in no-recovery mode. Filesystem will
> > > be inconsistent.",
> > > +			   XFS_SB_VERSION_NUM(&mp->m_sb),
> > > +			   &mp->m_sb.sb_uuid);
> > >  		ASSERT(mp->m_flags & XFS_MOUNT_RDONLY);
> > >  	}
> > > 
> > > diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
> > > index e5e0713bebcd8..a4b8a5ad8039f 100644
> > > --- a/fs/xfs/xfs_super.c
> > > +++ b/fs/xfs/xfs_super.c
> > > @@ -1043,7 +1043,7 @@ xfs_fs_put_super(
> > >  	if (!sb->s_fs_info)
> > >  		return;
> > > 
> > > -	xfs_notice(mp, "Unmounting Filesystem");
> > > +	xfs_notice(mp, "Unmounting Filesystem %pU", &mp->m_sb.sb_uuid);
> > >  	xfs_filestream_unmount(mp);
> > >  	xfs_unmountfs(mp);
> > > 
> > > --
> > > 2.31.1
> > >