Re: [PATCH 2/2] generic: test small swapfile without page-aligned contiguous blocks

Zorro Lang
2021-05-26T03:55:46Z

On Tue, May 25, 2021 at 09:09:07AM -0700, Darrick J. Wong wrote:
> On Tue, May 25, 2021 at 12:46:42PM +0800, Zorro Lang wrote:
> > If a swapfile doesn't contain even a single page-aligned contiguous
> > range of blocks, it's an invalid swapfile, and might cause kernel
> > issue. This case covered commit 5808fecc5723 ("iomap: Fix negative
> > assignment to unsigned sis->pages in iomap_swapfile_activate").
> >
> > Signed-off-by: Zorro Lang <zlang@redhat.com>
> > ---
> > tests/generic/638 | 79 +++++++++++++++++++++++++++++++++++++++++++
> > tests/generic/638.out | 2 ++
> > tests/generic/group | 1 +
> > 3 files changed, 82 insertions(+)
> > create mode 100755 tests/generic/638
> > create mode 100644 tests/generic/638.out
> >
> > diff --git a/tests/generic/638 b/tests/generic/638
> > new file mode 100755
> > index 00000000..74bc39cb
> > --- /dev/null
> > +++ b/tests/generic/638
> > @@ -0,0 +1,79 @@
> > +#! /bin/bash
> > +# SPDX-License-Identifier: GPL-2.0
> > +# Copyright (c) 2021 Red Hat Inc. All Rights Reserved.
> > +#
> > +# FS QA Test 638
> > +#
> > +# Test small swapfile which doesn't contain even a single page-aligned contiguous
> > +# range of blocks. This case covered commit 5808fecc5723 ("iomap: Fix negative
> > +# assignment to unsigned sis->pages in iomap_swapfile_activate").
> > +#
> > +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.*
> > +}
> > +
> > +# get standard environment, filters and checks
> > +. ./common/rc
> > +. ./common/filter
> > +
> > +# remove previous $seqres.full before test
> > +rm -f $seqres.full
> > +
> > +# real QA test starts here
> > +_supported_fs generic
> > +_require_scratch
> > +_require_scratch_swapfile
> > +_require_test_program mkswap
> > +_require_test_program swapon
> > +
> > +make_unaligned_swapfile()
> > +{
> > + local fname=$1
> > + local n=$((psize / bsize - 1))
> > +
> > + # Make sure the swapfile doesn't contain even a single page-aligned
> > + # contiguous range of blocks. This's necessary to cover the bug
> > + $XFS_IO_PROG -f -t -c "pwrite 0 $(((psize + bsize) * n))" $fname >> $seqres.full 2>&1
> > + for((i=1; i<=n; i++));do
> > + $XFS_IO_PROG -c "fcollapse $(((psize - bsize) * i)) $bsize" $fname
> > + done
> > + chmod 0600 $fname
> > + $CHATTR_PROG +C $fname > /dev/null 2>&1
> > + $here/src/mkswap $fname
> > +}
> > +
> > +_scratch_mkfs >> $seqres.full 2>&1
> > +_scratch_mount
> > +psize=`get_page_size`
> > +bsize=`_get_block_size $SCRATCH_MNT`
>
> _get_file_block_size, since fcollapse requires arguments aligned to the
> file's allocation unit, which isn't necessarily the same as the fs block
> size (bigalloc, rt, etc.)...

You're right.

>
> > +# Due to we need page-unaligned blocks, so blocksize < pagesize is necessary.
> > +# If not, try to make a smaller enough block size
> > +if [ $bsize -ge $psize ];then
> > + _scratch_unmount
> > + _scratch_mkfs_blocksized 1024 >> $seqres.full 2>&1
>
> ...which leads me to the next question, which is: Should the above
> helper override mkfs options as necessary to enforce that the allocation
> unit is 1024 bytes? Or is it time for a new helper?

Hmm... the _scratch_mkfs_blocksized() does:

xfs)
_scratch_mkfs_xfs $MKFS_OPTIONS -b size=$blocksize

_scratch_mkfs_xfs() already use $MKFS_OPTIONS internally, don't need to give
$MKFS_OPTIONS to it again. Although _scratch_mkfs_xfs deals with $MKFS_OPTIONS,
it just drops whole $MKFS_OPTIONS if there're conflicts.

The _scratch_mkfs_geom() does overwrite, but _scratch_mkfs_sized doesn't (sized
filesystem is rarely seen in local.config). We might let _scratch_mkfs_blocksized
learn _scratch_mkfs_geom.

>
> > + if [ $? -ne 0 ];then
> > + _notrun "Can't make filesystem block size < page size"
> > + fi
> > + _scratch_mount
> > + bsize=1024
>
> You probably want to re-check _get_file_block_size to make sure that you
> actually got blocksize < pagesize in the format attempt.

Yes, you're right. _scratch_mkfs_blocksized can't make sure to get that blocksize.

Thanks,
Zorro

>
> --D
>
> > +fi
> > +swapfile=$SCRATCH_MNT/$seq.swapfile
> > +make_unaligned_swapfile $swapfile
> > +$here/src/swapon $swapfile
> > +swapoff $swapfile
> > +
> > +echo "Silence is golden"
> > +# success, all done
> > +status=0
> > +exit
> > diff --git a/tests/generic/638.out b/tests/generic/638.out
> > new file mode 100644
> > index 00000000..3113b1e3
> > --- /dev/null
> > +++ b/tests/generic/638.out
> > @@ -0,0 +1,2 @@
> > +QA output created by 638
> > +Silence is golden
> > diff --git a/tests/generic/group b/tests/generic/group
> > index b9614c69..5b9b3d1b 100644
> > --- a/tests/generic/group
> > +++ b/tests/generic/group
> > @@ -640,3 +640,4 @@
> > 635 auto quick atime bigtime shutdown
> > 636 auto quick swap
> > 637 auto quick rw
> > +638 auto quick swap
> > --
> > 2.31.1
> >
>