Re: [PATCH 1/1] xfs: test xfs_scrub phase 6 media error reporting

["Darrick J. Wong" <djwong@kernel.org>]

On Wed, Nov 02, 2022 at 11:45:58AM +0800, Zorro Lang wrote:
> On Tue, Nov 01, 2022 at 05:59:50PM -0700, Darrick J. Wong wrote:
> > On Wed, Nov 02, 2022 at 12:43:45AM +0800, Zorro Lang wrote:
> > > On Tue, Oct 18, 2022 at 03:45:18PM -0700, Darrick J. Wong wrote:
> > > > From: Darrick J. Wong <djwong@kernel.org>
> > > > 
> > > > Add new helpers to dmerror to provide for marking selected ranges
> > > > totally bad -- both reads and writes will fail.  Create a new test for
> > > > xfs_scrub to check that it reports media errors in data files correctly.
> > > > 
> > > > Signed-off-by: Darrick J. Wong <djwong@kernel.org>
> > > > ---
> > > >  common/dmerror    |  136 +++++++++++++++++++++++++++++++++++++++++++++--
> > > >  common/xfs        |    9 +++
> > > >  tests/xfs/747     |  155 +++++++++++++++++++++++++++++++++++++++++++++++++++++
> > > >  tests/xfs/747.out |   12 ++++
> > > >  4 files changed, 309 insertions(+), 3 deletions(-)
> > > >  create mode 100755 tests/xfs/747
> > > >  create mode 100644 tests/xfs/747.out
> > > > 
> > > > 
> > > > diff --git a/common/dmerror b/common/dmerror
> > > > index 54122b12ea..58ab461e0e 100644
> > > > --- a/common/dmerror
> > > > +++ b/common/dmerror
> > > > @@ -159,16 +159,16 @@ _dmerror_load_error_table()
> > > >  	fi
> > > >  
> > > >  	# Load new table
> > > > -	$DMSETUP_PROG load error-test --table "$DMERROR_TABLE"
> > > > +	echo "$DMERROR_TABLE" | $DMSETUP_PROG load error-test
> > > >  	load_res=$?
> > > >  
> > > >  	if [ -n "$NON_ERROR_RTDEV" ]; then
> > > > -		$DMSETUP_PROG load error-rttest --table "$DMERROR_RTTABLE"
> > > > +		echo "$DMERROR_RTTABLE" | $DMSETUP_PROG load error-rttest
> > > >  		[ $? -ne 0 ] && _fail "failed to load error table into error-rttest"
> > > >  	fi
> > > >  
> > > >  	if [ -n "$NON_ERROR_LOGDEV" ]; then
> > > > -		$DMSETUP_PROG load error-logtest --table "$DMERROR_LOGTABLE"
> > > > +		echo "$DMERROR_LOGTABLE" | $DMSETUP_PROG load error-logtest
> > > 
> > > Hi,
> > > 
> > > Is there any reason about why we need to replace "dmsetup --table $table" with
> > > "echo $table | dmsetup"?
> > 
> > Once we poke enough dmerror holes into the mapping, $table becomes a
> > multiline string, and I feel that pipes are better suited to that usage
> > than stuffing a huge string into argv[].
> 
> Oh, make sense.
> 
> > 
> > That said, I don't have any plans to create multigigabyte table
> > definitions, so it's no big deal to switch them back.
> 
> If we haven't hit any real problems, how about do this change in a seperated
> patch when we need it, and at that time you might like to change other
> common/dmxxxx (e.g. dmflakey, dmthin ...) with this dmerror together?

Ok.  I'll try leaving the --table=$table and see how it goes.

> > 
> > > >  		[ $? -ne 0 ] && _fail "failed to load error table into error-logtest"
> > > >  	fi
> > > >  
> > > > @@ -250,3 +250,133 @@ _dmerror_load_working_table()
> > > >  	[ $load_res -ne 0 ] && _fail "dmsetup failed to load error table"
> > > >  	[ $resume_res -ne 0 ] && _fail  "dmsetup resume failed"
> > > >  }
> > > > +
> > > > +# Given a list of (start, length) tuples on stdin, combine adjacent tuples into
> > > > +# larger ones and write the new list to stdout.
> > > > +__dmerror_combine_extents()
> > > > +{
> > > > +	awk 'BEGIN{start = 0; len = 0;}{
> > > > +if (start + len == $1) {
> > > > +	len += $2;
> > > > +} else {
> > > > +	if (len > 0)
> > > > +		printf("%d %d\n", start, len);
> > > > +	start = $1;
> > > > +	len = $2;
> > > > +}
> > > > +} END {
> > > > +	if (len > 0)
> > > > +		printf("%d %d\n", start, len);
> > > > +}'
> > > > +}
> > > > +
> > > > +# Given a block device, the name of a preferred dm target, the name of an
> > > > +# implied dm target, and a list of (start, len) tuples on stdin, create a new
> > > > +# dm table which maps each of the tuples to the preferred target and all other
> > > > +# areas to the implied dm target.
> > > > +__dmerror_recreate_map()
> > > > +{
> > > > +	local device="$1"
> > > > +	local preferred_tgt="$2"
> > > > +	local implied_tgt="$3"
> > > > +	local size=$(blockdev --getsz "$device")
> > > > +
> > > > +	awk -v device="$device" -v size=$size -v implied_tgt="$implied_tgt" \
> > > > +		-v preferred_tgt="$preferred_tgt" 'BEGIN{implied_start = 0;}{
> > > > +	extent_start = $1;
> > > > +	extent_len = $2;
> > > > +
> > > > +	if (extent_start > size) {
> > > > +		extent_start = size;
> > > > +		extent_len = 0;
> > > > +	} else if (extent_start + extent_len > size) {
> > > > +		extent_len = size - extent_start;
> > > > +	}
> > > > +
> > > > +	if (implied_start < extent_start)
> > > > +		printf("%d %d %s %s %d\n", implied_start,
> > > > +				extent_start - implied_start, implied_tgt,
> > > > +				device, implied_start);
> > > > +	printf("%d %d %s %s %d\n", extent_start, extent_len, preferred_tgt,
> > > > +			device, extent_start);
> > > > +	implied_start = extent_start + extent_len;
> > > > +}END{
> > > > +	if (implied_start < size)
> > > > +		printf("%d %d %s %s %d\n", implied_start, size - implied_start,
> > > > +				implied_tgt, device, implied_start);
> > > > +}'
> > > 
> > > Above indentation (of awk code mix with bash function) is a little confused ...
> > 
> > I'm not sure how to make it any prettier -- embedding code from one
> > language into a function written in a different but similar language is
> > always going to be fugly.
> > 
> > Predefining the awk program text as a global string would avoid that but
> > pollute the global namespace.
> > 
> > I could indent the entire awk program so the indent might be less weird:
> > 
> > __dmerror_recreate_map()
> > {
> > 	local device="$1"
> > 	local preferred_tgt="$2"
> > 	local implied_tgt="$3"
> > 	local size=$(blockdev --getsz "$device")
> > 
> > 	awk -v device="$device" -v size=$size -v implied_tgt="$implied_tgt" \
> > 		-v preferred_tgt="$preferred_tgt" '
> > 	BEGIN {
> > 		implied_start = 0;
> > 	}
> > 	{
> > 		extent_start = $1;
> > 		extent_len = $2;
> > 
> > 		if (extent_start > size) {
> > 			extent_start = size;
> > 			extent_len = 0;
> > 		} else if (extent_start + extent_len > size) {
> > 			extent_len = size - extent_start;
> > 		}
> > 
> > 		if (implied_start < extent_start)
> > 			printf("%d %d %s %s %d\n", implied_start,
> > 					extent_start - implied_start,
> > 					implied_tgt, device, implied_start);
> > 		printf("%d %d %s %s %d\n", extent_start, extent_len,
> > 				preferred_tgt, device, extent_start);
> > 		implied_start = extent_start + extent_len;
> > 	}
> > 	END {
> > 		if (implied_start < size)
> > 			printf("%d %d %s %s %d\n", implied_start,
> > 					size - implied_start, implied_tgt,
> > 					device, implied_start);
> > 	}'
> > }
> > 
> > but now the awk code has the same level of indenting as the bash code.
> 
> Yeah, it's hard to say how to deal with the format of long embedded code, but
> this one looks better to me, and I think we can add two comment lines to mark
> the 'start and end' of the embedded awk program. I think we can change this
> function and __dmerror_combine_extents() like that.

<shrug> I've actually taken a liking to defining the awk program as a
local variable in the function and moving the actual call to awk at the
end.  That way it's obvious that we've gone back to shell mode...

> > 
> > I could put a comment at the end noting that we're switching from awk
> > back to bash, or I could define the awk program as a local string, but I
> > don't think that's going to clear things up that much...
> > 
> > __dmerror_recreate_map()
> > {
> > 	local device="$1"
> > 	local preferred_tgt="$2"
> > 	local implied_tgt="$3"
> > 	local size=$(blockdev --getsz "$device")
> > 
> > 	local awk_program='
> > 	BEGIN {
> > 		implied_start = 0;
> > 	}
> > 	{
> > 		extent_start = $1;
> > 		extent_len = $2;
> > 
> > 		if (extent_start > size) {
> > 			extent_start = size;
> > 			extent_len = 0;
> > 		} else if (extent_start + extent_len > size) {
> > 			extent_len = size - extent_start;
> > 		}
> > 
> > 		if (implied_start < extent_start)
> > 			printf("%d %d %s %s %d\n", implied_start,
> > 					extent_start - implied_start,
> > 					implied_tgt, device, implied_start);
> > 		printf("%d %d %s %s %d\n", extent_start, extent_len,
> > 				preferred_tgt, device, extent_start);
> > 		implied_start = extent_start + extent_len;
> > 	}
> > 	END {
> > 		if (implied_start < size)
> > 			printf("%d %d %s %s %d\n", implied_start,
> > 					size - implied_start, implied_tgt,
> > 					device, implied_start);
> > 	}'
> > 
> > 	awk -v device="$device" -v size=$size -v implied_tgt="$implied_tgt" \
> > 		-v preferred_tgt="$preferred_tgt" "$awk_program"
> > }

...aka this chunk.  Do you mind if I leave it this way?

> > 
> > Hm?
> > 
> > > > +}
> > > > +
> > > > +# Update the dm error table so that the range (start, len) maps to the
> > > > +# preferred dm target, overriding anything that maps to the implied dm target.
> > > > +# This assumes that the only desired targets for this dm device are the
> > > > +# preferred and and implied targets.  The fifth argument is the scratch device
> > > > +# that we want to change the table for.
> > > > +__dmerror_change()
> > > > +{
> > > > +	local start="$1"
> > > > +	local len="$2"
> > > > +	local preferred_tgt="$3"
> > > > +	local implied_tgt="$4"
> > > > +	local whichdev="$5"
> > > 
> > > local old_table ?
> > > local new_table ?
> > 
> > Oops.  Fixed.
> > 
> > > > +
> > > > +	case "$whichdev" in
> > > > +	"SCRATCH_DEV"|"")	whichdev="$SCRATCH_DEV";;
> > > > +	"SCRATCH_LOGDEV"|"LOG")	whichdev="$NON_ERROR_LOGDEV";;
> > > > +	"SCRATCH_RTDEV"|"RT")	whichdev="$NON_ERROR_RTDEV";;
> > > > +	esac
> > > > +
> > > > +	case "$whichdev" in
> > > > +	"$SCRATCH_DEV")		old_table="$DMERROR_TABLE";;
> > > > +	"$NON_ERROR_LOGDEV")	old_table="$DMERROR_LOGTABLE";;
> > > > +	"$NON_ERROR_RTDEV")	old_table="$DMERROR_RTTABLE";;
> > > > +	*)
> > > > +		echo "$whichdev: Unknown dmerror device."
> > > > +		return
> > > > +		;;
> > > > +	esac
> > > > +
> > > > +	new_table="$( (echo "$old_table"; echo "$start $len $preferred_tgt") | \
> > > > +		awk -v type="$preferred_tgt" '{if ($3 == type) print $0;}' | \
> > > > +		sort -g | \
> > > > +		__dmerror_combine_extents | \
> > > > +		__dmerror_recreate_map "$whichdev" "$preferred_tgt" \
> > > > +				"$implied_tgt" )"
> > > > +
> > > > +	case "$whichdev" in
> > > > +	"$SCRATCH_DEV")		DMERROR_TABLE="$new_table";;
> > > > +	"$NON_ERROR_LOGDEV")	DMERROR_LOGTABLE="$new_table";;
> > > > +	"$NON_ERROR_RTDEV")	DMERROR_RTTABLE="$new_table";;
> > > > +	esac
> > > > +}
> > > > +
> > > > +# Reset the dm error table to everything ok.  The dm device itself must be
> > > > +# remapped by calling _dmerror_load_error_table.
> > > > +_dmerror_reset_table()
> > > > +{
> > > > +	DMERROR_TABLE="$DMLINEAR_TABLE"
> > > > +	DMERROR_LOGTABLE="$DMLINEAR_LOGTABLE"
> > > > +	DMERROR_RTTABLE="$DMLINEAR_RTTABLE"
> > > > +}
> > > > +
> > > > +# Update the dm error table so that IOs to the given range will return EIO.
> > > > +# The dm device itself must be remapped by calling _dmerror_load_error_table.
> > > > +_dmerror_mark_range_bad()
> > > > +{
> > > > +	local start="$1"
> > > > +	local len="$2"
> > > > +	local dev="$3"
> > > > +
> > > > +	__dmerror_change "$start" "$len" error linear "$dev"
> > > > +}
> > > > +
> > > > +# Update the dm error table so that IOs to the given range will succeed.
> > > > +# The dm device itself must be remapped by calling _dmerror_load_error_table.
> > > > +_dmerror_mark_range_good()
> > > > +{
> > > > +	local start="$1"
> > > > +	local len="$2"
> > > > +	local dev="$3"
> > > > +
> > > > +	__dmerror_change "$start" "$len" linear error "$dev"
> > > > +}
> > > > diff --git a/common/xfs b/common/xfs
> > > > index e1c15d3d04..2cd8254937 100644
> > > > --- a/common/xfs
> > > > +++ b/common/xfs
> > > > @@ -194,6 +194,15 @@ _xfs_get_file_block_size()
> > > >  	$XFS_INFO_PROG "$path" | grep realtime | sed -e 's/^.*extsz=\([0-9]*\).*$/\1/g'
> > > >  }
> > > >  
> > > > +# Decide if this path is a file on the realtime device
> > > > +_xfs_is_realtime_file()
> > > > +{
> > > > +	if [ "$USE_EXTERNAL" != "yes" ] || [ -z "$SCRATCH_RTDEV" ]; then
> > > > +		return 1
> > > > +	fi
> > > > +	$XFS_IO_PROG -c 'stat -v' "$1" | grep -q -w realtime
> > > > +}
> > > > +
> > > >  # Set or clear the realtime status of every supplied path.  The first argument
> > > >  # is either 'data' or 'realtime'.  All other arguments should be paths to
> > > >  # existing directories or empty regular files.
> > > > diff --git a/tests/xfs/747 b/tests/xfs/747
> > > 
> > > I tried this case, and got below error, looks like the od error output need a filter?
> > > 
> > > # ./check -s simpledev -s logdev xfs/747
> > > SECTION       -- simpledev
> > > FSTYP         -- xfs (debug)
> > > PLATFORM      -- Linux/x86_64 hp-dl380pg8-01 6.1.0-rc3 #5 SMP PREEMPT_DYNAMIC Tue Nov  1 01:08:52 CST 2022
> > > MKFS_OPTIONS  -- -f /dev/sda3
> > > MOUNT_OPTIONS -- -o context=system_u:object_r:root_t:s0 /dev/sda3 /mnt/scratch
> > > 
> > > xfs/747       - output mismatch (see /root/git/xfstests/results//simpledev/xfs/747.out.bad)
> > >     --- tests/xfs/747.out       2022-11-01 14:48:56.990683131 +0800
> > >     +++ /root/git/xfstests/results//simpledev/xfs/747.out.bad   2022-11-01 19:38:34.825632961 +0800
> > >     @@ -5,7 +5,7 @@
> > >      Scrub for injected media error (multi threaded)
> > >      Unfixable Error: SCRATCH_MNT/a: media error at data offset 2FSB length 1FSB.
> > >      SCRATCH_MNT: unfixable errors found: 1
> > >     -od: SCRATCH_MNT/a: read error: Input/output error
> > >     +od: SCRATCH_MNT/a: Input/output error
> > 
> > Err, what operating system is this?
> 
> # lsb_release -a
> LSB Version:    :core-4.1-amd64:core-4.1-noarch
> Distributor ID: Fedora
> Description:    Fedora release 38 (Rawhide)
> Release:        38
> Codename:       Rawhide
> # uname -r
> 6.1.0-rc3
> # rpm -qf `type -P od`
> coreutils-9.1-8.fc38.x86_64
>  uname -r
> 6.1.0-rc3

Aha.  Ok.  I run ancient 6mo things like Ubuntu 22.04 so I hadn't seen
that.

--D

> > 
> > --D
> > 
> > > 
> > > > new file mode 100755
> > > > index 0000000000..8952c24ee6
> > > > --- /dev/null
> > > > +++ b/tests/xfs/747
> > > > @@ -0,0 +1,155 @@
> > > > +#! /bin/bash
> > > > +# SPDX-License-Identifier: GPL-2.0-or-later
> > > > +# Copyright (c) 2022 Oracle.  All Rights Reserved.
> > > > +#
> > > > +# FS QA Test No. 747
> > > > +#
> > > > +# Check xfs_scrub's media scan can actually return diagnostic information for
> > > > +# media errors in file data extents.
> > > > +
> > > > +. ./common/preamble
> > > > +_begin_fstest auto quick scrub
> > > 
> > >   eio ?
> 
> Thanks,
> Zorro
> 
> > > 
> > > Thanks,
> > > Zorro
> > > 
> > > > +
> > > > +# Override the default cleanup function.
> > > > +_cleanup()
> > > > +{
> > > > +	cd /
> > > > +	rm -f $tmp.*
> > > > +	_dmerror_cleanup
> > > > +}
> > > > +
> > > > +# Import common functions.
> > > > +. ./common/fuzzy
> > > > +. ./common/filter
> > > > +. ./common/dmerror
> > > > +
> > > > +# real QA test starts here
> > > > +_supported_fs xfs
> > > > +_require_dm_target error
> > > > +_require_scratch
> > > > +_require_scratch_xfs_crc
> > > > +_require_scrub
> > > > +
> > > > +filter_scrub_errors() {
> > > > +	_filter_scratch | sed \
> > > > +		-e "s/offset $((fs_blksz * 2)) /offset 2FSB /g" \
> > > > +		-e "s/length $fs_blksz.*/length 1FSB./g"
> > > > +}
> > > > +
> > > > +_scratch_mkfs >> $seqres.full
> > > > +_dmerror_init
> > > > +_dmerror_mount >> $seqres.full 2>&1
> > > > +
> > > > +_supports_xfs_scrub $SCRATCH_MNT $SCRATCH_DEV || _notrun "Scrub not supported"
> > > > +
> > > > +# Write a file with 4 file blocks worth of data
> > > > +victim=$SCRATCH_MNT/a
> > > > +file_blksz=$(_get_file_block_size $SCRATCH_MNT)
> > > > +$XFS_IO_PROG -f -c "pwrite -S 0x58 0 $((4 * file_blksz))" -c "fsync" $victim >> $seqres.full
> > > > +unset errordev
> > > > +_xfs_is_realtime_file $victim && errordev="RT"
> > > > +bmap_str="$($XFS_IO_PROG -c "bmap -elpv" $victim | grep "^[[:space:]]*0:")"
> > > > +echo "$errordev:$bmap_str" >> $seqres.full
> > > > +
> > > > +phys="$(echo "$bmap_str" | $AWK_PROG '{print $3}')"
> > > > +if [ "$errordev" = "RT" ]; then
> > > > +	len="$(echo "$bmap_str" | $AWK_PROG '{print $4}')"
> > > > +else
> > > > +	len="$(echo "$bmap_str" | $AWK_PROG '{print $6}')"
> > > > +fi
> > > > +fs_blksz=$(_get_block_size $SCRATCH_MNT)
> > > > +echo "file_blksz:$file_blksz:fs_blksz:$fs_blksz" >> $seqres.full
> > > > +kernel_sectors_per_fs_block=$((fs_blksz / 512))
> > > > +
> > > > +# Did we get at least 4 fs blocks worth of extent?
> > > > +min_len_sectors=$(( 4 * kernel_sectors_per_fs_block ))
> > > > +test "$len" -lt $min_len_sectors && \
> > > > +	_fail "could not format a long enough extent on an empty fs??"
> > > > +
> > > > +phys_start=$(echo "$phys" | sed -e 's/\.\..*//g')
> > > > +
> > > > +echo "$errordev:$phys:$len:$fs_blksz:$phys_start" >> $seqres.full
> > > > +echo "victim file:" >> $seqres.full
> > > > +od -tx1 -Ad -c $victim >> $seqres.full
> > > > +
> > > > +# Set the dmerror table so that all IO will pass through.
> > > > +_dmerror_reset_table
> > > > +
> > > > +cat >> $seqres.full << ENDL
> > > > +dmerror before:
> > > > +$DMERROR_TABLE
> > > > +$DMERROR_RTTABLE
> > > > +<end table>
> > > > +ENDL
> > > > +
> > > > +# All sector numbers that we feed to the kernel must be in units of 512b, but
> > > > +# they also must be aligned to the device's logical block size.
> > > > +logical_block_size=$(_min_dio_alignment $SCRATCH_DEV)
> > > > +kernel_sectors_per_device_lba=$((logical_block_size / 512))
> > > > +
> > > > +# Mark as bad one of the device LBAs in the middle of the extent.  Target the
> > > > +# second LBA of the third block of the four-block file extent that we allocated
> > > > +# earlier, but without overflowing into the fourth file block.
> > > > +bad_sector=$(( phys_start + (2 * kernel_sectors_per_fs_block) ))
> > > > +bad_len=$kernel_sectors_per_device_lba
> > > > +if (( kernel_sectors_per_device_lba < kernel_sectors_per_fs_block )); then
> > > > +	bad_sector=$((bad_sector + kernel_sectors_per_device_lba))
> > > > +fi
> > > > +if (( (bad_sector % kernel_sectors_per_device_lba) != 0)); then
> > > > +	echo "bad_sector $bad_sector not congruent with device logical block size $logical_block_size"
> > > > +fi
> > > > +_dmerror_mark_range_bad $bad_sector $bad_len $errordev
> > > > +
> > > > +cat >> $seqres.full << ENDL
> > > > +dmerror after marking bad:
> > > > +$DMERROR_TABLE
> > > > +$DMERROR_RTTABLE
> > > > +<end table>
> > > > +ENDL
> > > > +
> > > > +_dmerror_load_error_table
> > > > +
> > > > +# See if the media scan picks it up.
> > > > +echo "Scrub for injected media error (single threaded)"
> > > > +
> > > > +# Once in single-threaded mode
> > > > +_scratch_scrub -b -x >> $seqres.full 2> $tmp.error
> > > > +cat $tmp.error | filter_scrub_errors
> > > > +
> > > > +# Once in parallel mode
> > > > +echo "Scrub for injected media error (multi threaded)"
> > > > +_scratch_scrub -x >> $seqres.full 2> $tmp.error
> > > > +cat $tmp.error | filter_scrub_errors
> > > > +
> > > > +# Remount to flush the page cache and reread to see the IO error
> > > > +_dmerror_unmount
> > > > +_dmerror_mount
> > > > +echo "victim file:" >> $seqres.full
> > > > +od -tx1 -Ad -c $victim >> $seqres.full 2> $tmp.error
> > > > +cat $tmp.error | _filter_scratch
> > > > +
> > > > +# Scrub again to re-confirm the media error across a remount
> > > > +echo "Scrub for injected media error (after remount)"
> > > > +_scratch_scrub -x >> $seqres.full 2> $tmp.error
> > > > +cat $tmp.error | filter_scrub_errors
> > > > +
> > > > +# Now mark the bad range good so that a retest shows no media failure.
> > > > +_dmerror_mark_range_good $bad_sector $bad_len $errordev
> > > > +_dmerror_load_error_table
> > > > +
> > > > +cat >> $seqres.full << ENDL
> > > > +dmerror after marking good:
> > > > +$DMERROR_TABLE
> > > > +$DMERROR_RTTABLE
> > > > +<end table>
> > > > +ENDL
> > > > +
> > > > +echo "Scrub after removing injected media error"
> > > > +
> > > > +# Scrub one last time to make sure the error's gone.
> > > > +_scratch_scrub -x >> $seqres.full 2> $tmp.error
> > > > +cat $tmp.error | filter_scrub_errors
> > > > +
> > > > +# success, all done
> > > > +status=0
> > > > +exit
> > > > diff --git a/tests/xfs/747.out b/tests/xfs/747.out
> > > > new file mode 100644
> > > > index 0000000000..f85f1753a6
> > > > --- /dev/null
> > > > +++ b/tests/xfs/747.out
> > > > @@ -0,0 +1,12 @@
> > > > +QA output created by 747
> > > > +Scrub for injected media error (single threaded)
> > > > +Unfixable Error: SCRATCH_MNT/a: media error at data offset 2FSB length 1FSB.
> > > > +SCRATCH_MNT: unfixable errors found: 1
> > > > +Scrub for injected media error (multi threaded)
> > > > +Unfixable Error: SCRATCH_MNT/a: media error at data offset 2FSB length 1FSB.
> > > > +SCRATCH_MNT: unfixable errors found: 1
> > > > +od: SCRATCH_MNT/a: read error: Input/output error
> > > > +Scrub for injected media error (after remount)
> > > > +Unfixable Error: SCRATCH_MNT/a: media error at data offset 2FSB length 1FSB.
> > > > +SCRATCH_MNT: unfixable errors found: 1
> > > > +Scrub after removing injected media error
> > > > 
> > > 
> > 
>