Re: [PATCH] btrfs: test ENOSPC caused by many orphan items

[Omar Sandoval <osandov@osandov.com>]

On Wed, May 16, 2018 at 09:48:58AM +0800, Eryu Guan wrote:
> On Wed, May 09, 2018 at 11:21:55PM -0700, Omar Sandoval wrote:
> > From: Omar Sandoval <osandov@fb.com>
> > 
> > Btrfs has a bug where we can prematurely ENOSPC if we have lots of
> > orphaned files, i.e., deleted files which are still open. Add a test
> > which repeatedly creates and deletes a file while keeping all of the
> > file descriptors open. This should succeed but doesn't on Btrfs without
> > the fix.
> > 
> > Signed-off-by: Omar Sandoval <osandov@fb.com>
> > ---
> >  tests/generic/479     |  0
> >  tests/generic/487     | 65 +++++++++++++++++++++++++++++++++++++++++++
> >  tests/generic/487.out |  2 ++
> >  tests/generic/group   |  1 +
> >  4 files changed, 68 insertions(+)
> >  mode change 100644 => 100755 tests/generic/479
> >  create mode 100755 tests/generic/487
> >  create mode 100644 tests/generic/487.out
> > 
> > diff --git a/tests/generic/479 b/tests/generic/479
> > old mode 100644
> > new mode 100755
> > diff --git a/tests/generic/487 b/tests/generic/487
> > new file mode 100755
> > index 00000000..66379cf0
> > --- /dev/null
> > +++ b/tests/generic/487
> > @@ -0,0 +1,65 @@
> > +#! /bin/bash
> > +# FS QA Test 487
> > +#
> > +# Test having many file descriptors referring to deleted files open. Regression
> > +# test for patch "Btrfs: fix ENOSPC caused by orphan items reservations".
> > +#
> > +#-----------------------------------------------------------------------
> > +# Copyright (c) 2018 Omar Sandoval.  All Rights Reserved.
> > +#
> > +# This program is free software; you can redistribute it and/or
> > +# modify it under the terms of the GNU General Public License as
> > +# published by the Free Software Foundation.
> > +#
> > +# This program is distributed in the hope that it would be useful,
> > +# but WITHOUT ANY WARRANTY; without even the implied warranty of
> > +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > +# GNU General Public License for more details.
> > +#
> > +# You should have received a copy of the GNU General Public License
> > +# along with this program; if not, write the Free Software Foundation,
> > +# Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
> > +#-----------------------------------------------------------------------
> > +#
> > +
> > +seq=`basename $0`
> > +seqres=$RESULT_DIR/$seq
> > +echo "QA output created by $seq"
> > +
> > +here=`pwd`
> > +tmp=/tmp/$$
> > +status=1	# failure is the default!
> > +trap "_cleanup; exit \$status" 0 1 2 3 15
> > +
> > +_cleanup()
> > +{
> > +	cd /
> > +	rm -f $tmp.*
> > +}
> > +
> > +. ./common/rc
> > +. ./common/filter
> > +
> > +rm -f $seqres.full
> > +
> > +_supported_fs generic
> > +_supported_os Linux
> > +_require_scratch
> > +
> > +_scratch_mkfs_sized $((1024 * 1024 * 1024)) >> $seqres.full 2>&1
> > +_scratch_mount
> > +
> > +test_file="$SCRATCH_MNT/$seq"
> > +
> > +(
> > +ulimit -n $((16 * 1024))
> > +# ~10000 files on a 1 GB filesystem should be no problem.
> > +for ((i = 1000; i < 10000; i++)); do
> > +	eval "exec $i<> \"$test_file\"" && rm "$test_file" || break
> > +done
> 
> There's a helper command in src that does exactly this job, e.g.
> 
> $here/src/multi_open_unlink -f $SCRATCH_MNT/$seq -n 10000 -s 0
> 
> which creates & unlinks 10000 files and keeps them open for 0 second in
> $SCRATCH_MNT using "$seq" as name prefix. This reduces the test run time
> from 13s to 1s for me.
> 
> It's a straightforward change, I'll just update on commit, please let me
> know if you have different thoughts.
> 
> Thanks,
> Eryu

Great, as long as it still reproduces the bug without the fix applied,
that's perfect. Thanks!