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

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

On Fri, Jun 03, 2022 at 11:14:13AM -0500, Eric Sandeen wrote:
> On 5/19/21 10:22 AM, 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.
> > 
> > Signed-off-by: Lukas Herbolt <lukas@herbolt.com>
> > ---
> > V2: Drop void casts and fix long lines
> 
> Can we revisit this? I think it's a nice enhancement.
> 
> The "nouuid" concern raised in the thread doesn't seem like a problem;
> if someone mounts with "-o nouuid" then you'll see 2 different devices
> mounted with the same uuid printed. I don't think that's an argument
> against the patch. Printing the uuid still provides more info than not.

Ok fair.

> I, uh, also don't think the submitter should be required to do a tree-wide
> change for an xfs printk enhancement. Sure, it'd be nice to have ext4
> and btrfs and and and but we have no other requirements that mount-time
> messages must be consistent across all filesystems....

As you pointed out on irc, btrfs already prints its own uuids.  So that
leaves ext4 -- are you all planning to send a patch for that?

(Otherwise, I don't mind this patch, if it helps support perform
forensics on systems with a lot of filesystem activity.)

> Thanks,
> -Eric
> 
> > 
> >  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);

sb_uuid is the uuid that the user can set, not the one that's encoded
identically in all the cloud vm images, right?

--D

> >  		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);
> >