Re: [PATCH 4/4] btrfs: test read repair on a corrupted compressed extent

[Zorro Lang <zlang@redhat.com>]

On Wed, Jun 22, 2022 at 11:21:40AM +0200, Christoph Hellwig wrote:
> So while this test properly documents the current behavior, it failed
> to grasp how broken that behavior ist: the current read repair code
> writes back the uncompressed data to disk even for a compressed extent,
> and this test verified the behavior.
> 
> Below is a correct test that fails on current mainline.  I'll send fixes
> but right now they depend on a lot of prep work.
> 
> ---
> From 6b6c505f75c6c7cc15359f14053b1db43e3d3091 Mon Sep 17 00:00:00 2001
> From: Christoph Hellwig <hch@lst.de>
> Date: Wed, 22 Jun 2022 06:55:36 +0200
> Subject: btrfs: test read repair on a corrupted compressed extent
> 
> Exercise read repair on a corrupted compressed sector.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  tests/btrfs/270     | 82 +++++++++++++++++++++++++++++++++++++++++++++
>  tests/btrfs/270.out |  7 ++++
>  2 files changed, 89 insertions(+)
>  create mode 100755 tests/btrfs/270
>  create mode 100644 tests/btrfs/270.out
> 
> diff --git a/tests/btrfs/270 b/tests/btrfs/270
> new file mode 100755
> index 00000000..5b73fb15
> --- /dev/null
> +++ b/tests/btrfs/270
> @@ -0,0 +1,82 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (c) 2017 Liu Bo.  All Rights Reserved.
                   ^^^^^^^^^^^
Is it a wrong copy&paste ?

> +#
> +# FS QA Test 270
> +#
> +# Regression test for btrfs buffered read repair of compressed data.

If this's a regression test, I'd like to see the fix be reviewed/acked
at first :)

Thanks,
Zorro

> +#
> +. ./common/preamble
> +_begin_fstest auto quick read_repair compress
> +
> +. ./common/filter
> +
> +_supported_fs btrfs
> +_require_btrfs_command inspect-internal dump-tree
> +_require_non_zoned_device "${SCRATCH_DEV}" # no overwrites on zoned devices
> +_require_scratch_dev_pool 2
> +_scratch_dev_pool_get 2
> +
> +get_physical()
> +{
> +	local logical=$1
> +	local stripe=$2
> +	$BTRFS_UTIL_PROG inspect-internal dump-tree -t 3 $SCRATCH_DEV | \
> +		grep $logical -A 6 | \
> +		$AWK_PROG "(\$1 ~ /stripe/ && \$3 ~ /devid/ && \$2 ~ /$stripe/) { print \$6 }"
> +}
> +
> +get_devid()
> +{
> +	local logical=$1
> +	local stripe=$2
> +	$BTRFS_UTIL_PROG inspect-internal dump-tree -t 3 $SCRATCH_DEV | \
> +		grep $logical -A 6 | \
> +		$AWK_PROG "(\$1 ~ /stripe/ && \$3 ~ /devid/ && \$2 ~ /$stripe/) { print \$4 }"
> +}
> +
> +get_device_path()
> +{
> +	local devid=$1
> +	echo "$SCRATCH_DEV_POOL" | $AWK_PROG "{print \$$devid}"
> +}
> +
> +
> +echo "step 1......mkfs.btrfs"
> +_check_minimal_fs_size $(( 1024 * 1024 * 1024 ))
> +_scratch_pool_mkfs "-d raid1 -b 1G" >>$seqres.full 2>&1
> +_scratch_mount -ocompress
> +
> +# Create a file with all data being compressed
> +$XFS_IO_PROG -f -c "pwrite -S 0xaa -W -b 128K 0 128K" \
> +	"$SCRATCH_MNT/foobar" | _filter_xfs_io_offset
> +
> +logical_in_btrfs=$(_btrfs_get_first_logical $SCRATCH_MNT/foobar)
> +physical=$(get_physical ${logical_in_btrfs} 1)
> +devid=$(get_devid ${logical_in_btrfs} 1)
> +devpath=$(get_device_path ${devid})
> +
> +_scratch_unmount
> +echo "step 2......corrupt file extent"
> +echo " corrupt stripe #1, devid $devid devpath $devpath physical $physical" \
> +	>> $seqres.full
> +dd if=$devpath of=$TEST_DIR/$seq.dump.good skip=$physical bs=1 count=4096 \
> +	2>/dev/null
> +$XFS_IO_PROG -c "pwrite -S 0xbb -b 4K $physical 4K" $devpath > /dev/null
> +
> +_scratch_mount
> +
> +echo "step 3......repair the bad copy"
> +_btrfs_buffered_read_on_mirror 1 2 "$SCRATCH_MNT/foobar" 0 128K
> +
> +_scratch_unmount
> +
> +echo "step 4......check if the repair worked"
> +dd if=$devpath of=$TEST_DIR/$seq.dump skip=$physical bs=1 count=4096 \
> +	2>/dev/null
> +cmp -bl $TEST_DIR/$seq.dump.good $TEST_DIR/$seq.dump
> +
> +_scratch_dev_pool_put
> +# success, all done
> +status=0
> +exit
> diff --git a/tests/btrfs/270.out b/tests/btrfs/270.out
> new file mode 100644
> index 00000000..6d744c02
> --- /dev/null
> +++ b/tests/btrfs/270.out
> @@ -0,0 +1,7 @@
> +QA output created by 270
> +step 1......mkfs.btrfs
> +wrote 131072/131072 bytes
> +XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
> +step 2......corrupt file extent
> +step 3......repair the bad copy
> +step 4......check if the repair worked
> -- 
> 2.30.2
>