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

[Lukas Herbolt <lukas@herbolt.com>]

On 21.05.2021 18:06, Darrick J. Wong wrote:
> 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
> 

Ah, right. Well using -o nouuid might have it's own info/notice in the 
logs
to make it clear.

>> 
>> 
>> 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
>> > >