Re: [PATCH 22/36] xfs_info: use findmnt to handle mounted block devices

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Tue, Mar 26, 2019 at 12:28:43PM -0500, Eric Sandeen wrote:
> On 3/14/19 4:06 PM, Darrick J. Wong wrote:
> > From: Darrick J. Wong <darrick.wong@oracle.com>
> > 
> > Use findmnt to determine if the passed-in argument is associated with a
> > mount point, and if so, use spaceman to query the mounted filesystem.
> > 
> > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> > ---
> >  debian/control       |    2 +-
> >  spaceman/xfs_info.sh |   14 +++++++++++---
> >  2 files changed, 12 insertions(+), 4 deletions(-)
> > 
> > 
> > diff --git a/debian/control b/debian/control
> > index f4f807b0..0b3205f5 100644
> > --- a/debian/control
> > +++ b/debian/control
> > @@ -8,7 +8,7 @@ Standards-Version: 4.0.0
> >  Homepage: https://xfs.wiki.kernel.org/
> >  
> >  Package: xfsprogs
> > -Depends: ${shlibs:Depends}, ${misc:Depends}, python3:any
> > +Depends: ${shlibs:Depends}, ${misc:Depends}, python3:any, util-linux
> >  Provides: fsck-backend
> >  Suggests: xfsdump, acl, attr, quota
> >  Breaks: xfsdump (<< 3.0.0)
> > diff --git a/spaceman/xfs_info.sh b/spaceman/xfs_info.sh
> > index ecf17f61..70978164 100755
> > --- a/spaceman/xfs_info.sh
> > +++ b/spaceman/xfs_info.sh
> > @@ -24,11 +24,19 @@ set -- extra "$@"
> >  shift $OPTIND
> >  case $# in
> >  	1)
> > -		if [ -b "$1" ] || [ -f "$1" ]; then
> > -			xfs_db -p xfs_info -c "info" $OPTS "$1"
> > +		arg="$1"
> > +
> > +		# See if we can map the arg to a loop device
> > +		loopdev="$(losetup -n -O NAME -j "${arg}" 2> /dev/null)"
> 
> hm, -n has existed since 2013...
> 
> commit 9f56106df6b49864ba604f6824f9fad5aeabd17a
> Author: Karel Zak <kzak@redhat.com>
> Date:   Mon May 13 12:00:24 2013 +0200
> 
>     losetup: add --raw and --noheadings
>     
>     Signed-off-by: Karel Zak <kzak@redhat.com>
> 
> and -O since 2012:
> 
> commit 896352d3906c19e8519670f1a511afb01083ed5e
> Author: Ondrej Oprala <ooprala@redhat.com>
> Date:   Mon Nov 12 13:08:00 2012 +0100
> 
>     losetup: add --list and --output option
> 
> So, granted, that is a /long time/.  And yet, somehow, my RHEL7 box does not
> have -n....
> 
> # losetup -j fsfile | awk -F: '{print $1}'
> /dev/loop0
> 
> perhaps, for older compatibility?
> 
> (and do we need to handle association w/ more than 1 loop dev? urk...)

Ok, I'll fix it to avoid losetup -n and only return the last one it
finds.

--D

> 
> 
> > +		test -n "${loopdev}" && arg="${loopdev}"
> > +
> > +		# If we find a mountpoint for the device, do a live query;
> > +		# otherwise try reading the fs with xfs_db.
> > +		if mountpt="$(findmnt -f -n -o TARGET "${arg}" 2> /dev/null)"; then
> > +			xfs_spaceman -p xfs_info -c "info" $OPTS "${mountpt}"
> >  			status=$?
> >  		else
> > -			xfs_spaceman -p xfs_info -c "info" $OPTS "$1"
> > +			xfs_db -p xfs_info -c "info" $OPTS "${arg}"
> >  			status=$?
> >  		fi
> >  		;;
> >