Re: [PATCH] fstests: btrfs: Test fiemap ioctl on completely deduped file

[Filipe Manana <fdmanana@gmail.com>]

On Tue, May 10, 2016 at 9:39 AM, Qu Wenruo <quwenruo@cn.fujitsu.com> wrote:
> For a completely deduped file, which means all its file extent are
> pointing to one bytenr, if calling fiemap on it, btrfs will cause soft
> hang up or just takes years long.
>
> This bug can be reproduced even without any in-band or out-of-band
> dedupe, normal clone_file_range() call can create such situation.
>
> This test case will detect it.

Why isn't this a generic test?
There's nothing btrfs specific anymore...

Thanks.

>
> Reported-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com>
> Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
> ---
>  tests/btrfs/028     | 78 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  tests/btrfs/028.out |  3 +++
>  tests/btrfs/group   |  1 +
>  3 files changed, 82 insertions(+)
>  create mode 100755 tests/btrfs/028
>  create mode 100644 tests/btrfs/028.out
>
> diff --git a/tests/btrfs/028 b/tests/btrfs/028
> new file mode 100755
> index 0000000..62bcc9d
> --- /dev/null
> +++ b/tests/btrfs/028
> @@ -0,0 +1,78 @@
> +#! /bin/bash
> +# FS QA Test 028
> +#
> +# Test fiemap ioctl on heavily deduped file.
> +#
> +# This test will cause btrfs to soft hang up or takes years long to finish

Haven't tried it, but I doubt it will take years...
Are you sure that the soft lookup, which is what makes the test fail
due to the dmesg warning, is triggered on very fast machines as well?
I.e. this may not be reliable on better hardware.


> +#
> +#-----------------------------------------------------------------------
> +# Copyright (c) 2016 Fujitsu. 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.*
> +}
> +
> +# get standard environment, filters and checks
> +. ./common/rc
> +. ./common/filter
> +. ./common/reflink
> +
> +# remove previous $seqres.full before test
> +rm -f $seqres.full
> +
> +# real QA test starts here
> +
> +# Modify as appropriate.
> +_supported_fs btrfs
> +_supported_os Linux
> +_require_scratch_reflink
> +
> +blocksize=$(( 128 * 1024 ))
> +nr=4096
> +file="$SCRATCH_MNT/tmp"
> +
> +_scratch_mkfs
> +_scratch_mount
> +
> +# write the initial block for later reflink
> +$XFS_IO_PROG -f -c "pwrite 0 $blocksize" -c "fsync" $file | _filter_xfs_io
> +
> +# use reflink to create the rest of the file, whose all extents are all
> +# pointing to the first extent
> +for i in $(seq 1 $nr); do
> +       $XFS_IO_PROG -c "reflink $file 0 $(( $i * $blocksize )) $blocksize" \
> +               $SCRATCH_MNT/tmp > /dev/null || _fail "reflink failed"
> +done
> +
> +# then call fiemap on that file, which shouldn't hang the fs by all means
> +$XFS_IO_PROG -c "fiemap" $file >> $seqres.full
> +
> +# success, all done
> +status=0
> +exit
> diff --git a/tests/btrfs/028.out b/tests/btrfs/028.out
> new file mode 100644
> index 0000000..2b5a9a5
> --- /dev/null
> +++ b/tests/btrfs/028.out
> @@ -0,0 +1,3 @@
> +QA output created by 028
> +wrote 131072/131072 bytes at offset 0
> +XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
> diff --git a/tests/btrfs/group b/tests/btrfs/group
> index da0e27f..8f6f877 100644
> --- a/tests/btrfs/group
> +++ b/tests/btrfs/group
> @@ -30,6 +30,7 @@
>  025 auto quick send clone
>  026 auto quick compress prealloc
>  027 auto replace
> +028 auto clone
>  029 auto quick clone
>  030 auto quick send
>  031 auto quick subvol clone
> --
> 2.5.5
>
>
>
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-- 
Filipe David Manana,

"Reasonable men adapt themselves to the world.
 Unreasonable men adapt the world to themselves.
 That's why all progress depends on unreasonable men."