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Date: Sat, 1 Sep 2018 14:49:26 +1000
From: Dave Chinner <david@fromorbit.com>
To: Ernesto =?iso-8859-1?Q?A=2E_Fern=E1ndez?=
        <ernesto.mnd.fernandez@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>,
        linux-fsdevel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 1/6] hfsplus: prevent btree data loss on root split
Message-ID: <20180901044926.GI1572@dastard>
References: <26d882184fc43043a810114258f45277752186c7.1535682461.git.ernesto.mnd.fernandez@gmail.com>
 <20180831053642.GA29605@infradead.org>
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On Fri, Aug 31, 2018 at 11:55:54AM -0300, Ernesto A. Fern�ndez wrote:
> On Thu, Aug 30, 2018 at 10:36:42PM -0700, Christoph Hellwig wrote:
> > On Fri, Aug 31, 2018 at 12:58:19AM -0300, Ernesto A. Fern�ndez wrote:
> > > Creating, renaming or deleting a file may cause catalog corruption and
> > > data loss.  This bug is randomly triggered by xfstests generic/027, but
> > > here is a faster reproducer:
> > > 
> > >   truncate -s 50M fs.iso
> > >   mkfs.hfsplus fs.iso
> > >   mount fs.iso /mnt
> > >   i=100
> > >   while [ $i -le 150 ]; do
> > >     touch /mnt/$i &>/dev/null
> > >     ((++i))
> > >   done
> > >   i=100
> > >   while [ $i -le 150 ]; do
> > >     mv /mnt/$i /mnt/$(perl -e "print $i x82") &>/dev/null
> > >     ((++i))
> > >   done
> > >   umount /mnt
> > >   fsck.hfsplus -n fs.iso
> > 
> > It would be good to wire up this short reproducer as well for xfstests.
> 
> Yes, that's my intention. The problem is that mkfs.hfsplus does not allow
> setting the size of the filesystem for scratch_mkfs_sized(); you need a
> workaround with the device mapper. I think I should submit that patch first
> and see if there is a problem with it.

You don't need to do that. We use loop devices like this w/ mkfs_dev
quite a lot in fstests. For example, generic/361 has pretty much the
exact code pattern you need....

Cheers,

Dave.


-- 
Dave Chinner
david@fromorbit.com