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https://github.com/linux-apfs/apfstests.git
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Qu Wenruo
a4f0a9bfd6
For fully deduped file, whose file extents are all pointing to the same extent, btrfs backref walk can be very time consuming, long enough to trigger softlock. Unfortunately, btrfs send is one of the caller of such backref walk under an O(n) loop, making the total time complexity to O(n^3) or more. And even worse, btrfs send will allocate memory in such loop, to trigger OOM on system with small memory(<4G). This test case will check if btrfs send will cause these problems. Reporeted-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com> Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com> Reviewed-by: Eryu Guan <eguan@redhat.com> Signed-off-by: Eryu Guan <eguan@redhat.com>
90 lines
2.6 KiB
Bash
Executable File
90 lines
2.6 KiB
Bash
Executable File
#! /bin/bash
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# FS QA Test 130
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#
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# Check if btrfs send can handle large deduped file, whose file extents
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# are all pointing to one extent.
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# Such file structure will cause quite large pressure to any operation which
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# iterates all backref of one extent.
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# And unfortunately, btrfs send is one of these operations, and will cause
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# softlock or OOM on systems with small memory(<4G).
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#
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#-----------------------------------------------------------------------
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# Copyright (c) 2016 Fujitsu. All Rights Reserved.
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#
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# This program is free software; you can redistribute it and/or
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# modify it under the terms of the GNU General Public License as
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# published by the Free Software Foundation.
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#
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# This program is distributed in the hope that it would be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write the Free Software Foundation,
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# Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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#-----------------------------------------------------------------------
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#
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seq=`basename $0`
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seqres=$RESULT_DIR/$seq
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echo "QA output created by $seq"
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here=`pwd`
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tmp=/tmp/$$
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status=1 # failure is the default!
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trap "_cleanup; exit \$status" 0 1 2 3 15
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_cleanup()
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{
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cd /
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rm -f $tmp.*
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}
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# get standard environment, filters and checks
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. ./common/rc
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. ./common/filter
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. ./common/reflink
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# remove previous $seqres.full before test
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rm -f $seqres.full
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# real QA test starts here
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# Modify as appropriate.
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_supported_fs btrfs
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_supported_os Linux
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_require_scratch
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_require_scratch_reflink
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_scratch_mkfs > /dev/null 2>&1
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_scratch_mount
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nr_extents=$((4096 * $LOAD_FACTOR))
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# Use 128K blocksize, the default value of both deduperemove or
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# inband dedupe
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blocksize=$((128 * 1024))
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file=$SCRATCH_MNT/foobar
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# create the initial file, whose file extents are all point to one extent
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_pwrite_byte 0xcdcdcdcd 0 $blocksize $file | _filter_xfs_io
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for i in $(seq 1 $(($nr_extents - 1))); do
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_reflink_range $file 0 $file $(($i * $blocksize)) $blocksize \
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> /dev/null 2>&1
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done
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# create a RO snapshot, so we can send out the snapshot
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_run_btrfs_util_prog subvolume snapshot -r $SCRATCH_MNT $SCRATCH_MNT/ro_snap
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# send out the subvolume, and it will either:
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# 1) OOM since memory is allocated inside a O(n^3) loop
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# 2) Softlock since time consuming backref walk is called without scheduling.
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# the send destination is not important, just send will cause the problem
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_run_btrfs_util_prog send $SCRATCH_MNT/ro_snap > /dev/null 2>&1
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# success, all done
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status=0
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exit
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