Re: [PATCH] common/xfs: wipe the XFS superblock of each AGs

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

On Fri, Sep 20, 2019 at 09:52:11AM +0800, Yang Xu wrote:
> 
> 
> on 2019/09/19 23:00, Zorro Lang wrote:
> > xfs/030 always fails after d0e484ac699f ("check: wipe scratch devices
> > between tests") get merged.
> > 
> > Due to xfs/030 does a sized(100m) mkfs. Before we merge above commit,
> > mkfs.xfs detects an old primary superblock, it will write zeroes to
> > all superblocks before formatting the new filesystem. But this won't
> > be done if we wipe the first superblock(by merging above commit).
> > 
> > That means if we make a (smaller) sized xfs after wipefs, those *old*
> > superblocks which created by last time mkfs.xfs will be left on disk.
> > Then when we do xfs_repair, if xfs_repair can't find the first SB, it
> > will go to find those *old* SB at first. When it finds them,
> > everyting goes wrong.
> > 
> > So I try to get XFS AG geometry(by default) and then try to erase all
> > superblocks. Thanks Darrick J. Wong helped to analyze this issue.
> Feel free to add Reported-by.
> > 
> > Signed-off-by: Zorro Lang <zlang@redhat.com>
> > ---
> >   common/rc  |  4 ++++
> >   common/xfs | 23 +++++++++++++++++++++++
> >   2 files changed, 27 insertions(+)
> > 
> > diff --git a/common/rc b/common/rc
> > index 66c7fd4d..fe13f659 100644
> > --- a/common/rc
> > +++ b/common/rc
> > @@ -4048,6 +4048,10 @@ _try_wipe_scratch_devs()
> >   	for dev in $SCRATCH_DEV_POOL $SCRATCH_DEV $SCRATCH_LOGDEV $SCRATCH_RTDEV; do
> >   		test -b $dev && $WIPEFS_PROG -a $dev
> >   	done
> > +
> > +	if [ "$FSTYP" = "xfs" ];then
> > +		try_wipe_scratch_xfs
> I think we should add a simple comment for why we add it.
> 
> ps:_scratch_mkfs_xfs also can make case pass. We can use it and add comment.
> the  try_wipe_scratch_xfs method and the _scratch_mkfs_xfs method are all
> acceptable for me.

Yes, I suppose formatting and then wiping per below would also achieve
our means, but it would come at the extra cost of zeroing the log.  I'm
not too eager to increase xfstest runtime even more.

Hmmm, I wonder if xfs_db could just grow a 'wipe all superblocks'
command....

--D

> > +	fi
> >   }
> >   # Only run this on xfs if xfs_scrub is available and has the unicode checker
> > diff --git a/common/xfs b/common/xfs
> > index 1bce3c18..34516f82 100644
> > --- a/common/xfs
> > +++ b/common/xfs
> > @@ -884,3 +884,26 @@ _xfs_mount_agcount()
> >   {
> >   	$XFS_INFO_PROG "$1" | grep agcount= | sed -e 's/^.*agcount=\([0-9]*\),.*$/\1/g'
> >   }
> > +
> > +# wipe the superblock of each XFS AGs
> > +try_wipe_scratch_xfs()
> > +{
> > +	local tmp=`mktemp -u`
> > +
> > +	_scratch_mkfs_xfs -N 2>/dev/null | perl -ne '
> > +		if (/^meta-data=.*\s+agcount=(\d+), agsize=(\d+) blks/) {
> > +			print STDOUT "agcount=$1\nagsize=$2\n";
> > +		}
> > +		if (/^data\s+=\s+bsize=(\d+)\s/) {
> > +			print STDOUT "dbsize=$1\n";
> > +		}' > $tmp.mkfs
> > +
> > +	. $tmp.mkfs
> > +	if [ -n "$agcount" -a -n "$agsize" -a -n "$dbsize" ];then
> > +		for ((i = 0; i < agcount; i++)); do
> > +			$XFS_IO_PROG -c "pwrite $((i * dbsize * agsize)) $dbsize" \
> > +				$SCRATCH_DEV >/dev/null;
> > +		done
> > +       fi
> > +       rm -f $tmp.mkfs
> > +}
> > 
> 
>