Re: [PATCH v3] generic: test small swapfile without page-aligned contiguous blocks

[riteshh <riteshh@linux.ibm.com>]

On 21/06/19 06:40AM, riteshh wrote:
> On 21/06/17 01:05PM, 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").
>
> Hi Zorro,
>
> Sorry for getting late on this. So can you reproduce the issue described in the
> patch on latest upstream kernel too w/o the above kernel fix with this fstest?
>
> So how I remember it, this fix on older kernel prevented a kernel panic.
> But on latest kernel it prevented from adding a fake hugesize swapfile.
> In your test, I don't see a test for checking whether the swapfile which was
> getting added is of the appropriate size or not. Note that this was only
> happening with a tiny swapfile of 1 blocksize(totalsize) only.

Update -
tiny swapfile of 2 pages. 1st page is reserved for swap headers I guess.
So I was using below logic, to fcollapse 1 block at the end of the every page.
And make sure that we allocated the swapfile with those extra blocks at creation
time, to get the swapfile size to match exact 2 pages.

Below logic may help make it more clear.

+$XFS_IO_PROG -f -c "pwrite 0 $(($PS + $PS + $BS + $BS))" -c fsync $SWAPFILE >> $seqres.full
+$XFS_IO_PROG -c "fcollapse $(($PS - $BS)) $BS" $SWAPFILE >> $seqres.full
+$XFS_IO_PROG -c "fcollapse $(($PS*2 - $BS*2)) $BS" $SWAPFILE >> $seqres.full
+$CHATTR_PROG +C $SWAPFILE >> $seqres.full 2>&1
+"$here/src/mkswap" $SWAPFILE


-ritesh

>
> If you take a look at [1], we are also checking for
> +	# error case
> +	if [ $swapsize -gt $filesize ]; then
> +		status=1
> +		echo "Allocated swap size($swapsize) cannot be greater than swapfile size($filesize)"
> +	fi
>
> [1]: https://patchwork.kernel.org/project/fstests/patch/e1f9798462ef60648db24b6291e1b149b114f2f2.1622105066.git.riteshh@linux.ibm.com/
>
> -ritesh
>
>
> >
> > Signed-off-by: Zorro Lang <zlang@redhat.com>
> > ---
> >
> > Thanks the review from Darrick, V3 did below changes:
> > 1) Add _require_xfs_io_command fcollapse
> > 2) Change the notrun output if block size isn't 1024.
> >
> > Thanks,
> > Zorro
> >
> >  tests/generic/639     | 83 +++++++++++++++++++++++++++++++++++++++++++
> >  tests/generic/639.out |  2 ++
> >  tests/generic/group   |  1 +
> >  3 files changed, 86 insertions(+)
> >  create mode 100755 tests/generic/639
> >  create mode 100644 tests/generic/639.out
> >
> > diff --git a/tests/generic/639 b/tests/generic/639
> > new file mode 100755
> > index 00000000..c8d0c6c5
> > --- /dev/null
> > +++ b/tests/generic/639
> > @@ -0,0 +1,83 @@
> > +#! /bin/bash
> > +# SPDX-License-Identifier: GPL-2.0
> > +# Copyright (c) 2021 Red Hat Inc.  All Rights Reserved.
> > +#
> > +# FS QA Test No. 639
> > +#
> > +# 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
> > +_require_xfs_io_command fcollapse
> > +
> > +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_file_block_size $SCRATCH_MNT`
> > +# 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
> > +	if [ $? -ne 0 ];then
> > +		_notrun "Can't make filesystem block size < page size."
> > +	fi
> > +	_scratch_mount
> > +	bsize=`_get_file_block_size $SCRATCH_MNT`
> > +	if [ $bsize -ne 1024 ];then
> > +		_notrun "Can't force 1024-byte file block size."
> > +	fi
> > +fi
> > +swapfile=$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/639.out b/tests/generic/639.out
> > new file mode 100644
> > index 00000000..62c66537
> > --- /dev/null
> > +++ b/tests/generic/639.out
> > @@ -0,0 +1,2 @@
> > +QA output created by 639
> > +Silence is golden
> > diff --git a/tests/generic/group b/tests/generic/group
> > index 9a636b23..48ffa3c7 100644
> > --- a/tests/generic/group
> > +++ b/tests/generic/group
> > @@ -641,3 +641,4 @@
> >  636 auto quick swap
> >  637 auto quick dir
> >  638 auto quick rw
> > +639 auto quick swap
> > --
> > 2.31.1
> >