Re: [patch 3/3] [PATCH 3/3] xfstests: add tests for new feature ioctl and sysfs interfaces

Josef Bacik
2013-10-28T16:02:13Z

On Fri, Oct 25, 2013 at 04:52:49PM -0400, Jeff Mahoney wrote:
> This tests the exporting of feature information from the kernel via
> sysfs and ioctl. The first test works whether the sysfs permissions
> are correct, if the information exported via sysfs matches
> what the ioctls are reporting, and if they both match the on-disk
> superblock's version of the feature sets. The second and third tests
> test online setting and clearing of feature bits via the sysfs and
> ioctl interfaces, checking whether they match the on-disk super on
> each cycle.
>
> In every case, if the features are not present, it is not considered
> a failure and a message indicating that will be dumped to the $num.full
> file.
>
> Signed-off-by: Jeff Mahoney <jeffm@suse.com>
> ---
> src/btrfs_ioctl_helper.c | 93 +++++++++++++++++
> tests/btrfs/102 | 263 +++++++++++++++++++++++++++++++++++++++++++++++
> tests/btrfs/102.out | 2 +
> tests/btrfs/103 | 188 +++++++++++++++++++++++++++++++++
> tests/btrfs/103.out | 2 +
> tests/btrfs/104 | 186 +++++++++++++++++++++++++++++++++
> tests/btrfs/104.out | 2 +
> 7 files changed, 736 insertions(+)
> create mode 100755 tests/btrfs/102
> create mode 100644 tests/btrfs/102.out
> create mode 100755 tests/btrfs/103
> create mode 100644 tests/btrfs/103.out
> create mode 100755 tests/btrfs/104
> create mode 100644 tests/btrfs/104.out
>
> diff --git a/src/btrfs_ioctl_helper.c b/src/btrfs_ioctl_helper.c
> index a88b7b5..73cfa60 100644
> --- a/src/btrfs_ioctl_helper.c
> +++ b/src/btrfs_ioctl_helper.c
> @@ -5,6 +5,7 @@
> #include <string.h>
> #include <stdint.h>
> #include <unistd.h>
> +#include <stdlib.h>
>
> #ifndef BTRFS_IOCTL_MAGIC
> #define BTRFS_IOCTL_MAGIC 0x94
> @@ -14,6 +15,21 @@
> #define BTRFS_IOC_GLOBAL_RSV _IOR(BTRFS_IOCTL_MAGIC, 20, uint64_t)
> #endif
>
> +#ifndef BTRFS_IOC_GET_FEATURES
> +struct btrfs_ioctl_feature_flags {
> + uint64_t compat_flags;
> + uint64_t compat_ro_flags;
> + uint64_t incompat_flags;
> +};
> +
> +#define BTRFS_IOC_GET_FEATURES _IOR(BTRFS_IOCTL_MAGIC, 57, \
> + struct btrfs_ioctl_feature_flags)
> +#define BTRFS_IOC_SET_FEATURES _IOW(BTRFS_IOCTL_MAGIC, 57, \
> + struct btrfs_ioctl_feature_flags[2])
> +#define BTRFS_IOC_GET_SUPPORTED_FEATURES _IOR(BTRFS_IOCTL_MAGIC, 57, \
> + struct btrfs_ioctl_feature_flags[3])
> +#endif
> +
> static int global_rsv_ioctl(int fd, int argc, char *argv[])
> {
> uint64_t reserved;
> @@ -25,6 +41,80 @@ static int global_rsv_ioctl(int fd, int argc, char *argv[])
> return 0;
> }
>
> +static int get_features_ioctl(int fd, int argc, char *argv[])
> +{
> + struct btrfs_ioctl_feature_flags flags;
> + int ret = ioctl(fd, BTRFS_IOC_GET_FEATURES, &flags);
> + if (ret)
> + return -errno;
> +
> + printf("0x%llx 0x%llx 0x%llx\n",
> + (unsigned long long)flags.compat_flags,
> + (unsigned long long)flags.compat_ro_flags,
> + (unsigned long long)flags.incompat_flags);
> + return 0;
> +}
> +
> +static int set_features_ioctl(int fd, int argc, char *argv[])
> +{
> + struct btrfs_ioctl_feature_flags flags[2];
> + uint64_t bit, *bits, *mask;
> + if (argc != 3)
> + goto usage;
> +
> + memset(flags, 0, sizeof(flags));
> +
> + errno = 0;
> + bit = strtoull(argv[2], NULL, 10);
> + if (errno)
> + goto usage;
> +
> + if (strcmp(argv[1], "compat") == 0) {
> + mask = &flags[0].compat_flags;
> + bits = &flags[1].compat_flags;
> + } else if (strcmp(argv[1], "compat_ro") == 0) {
> + mask = &flags[0].compat_ro_flags;
> + bits = &flags[1].compat_ro_flags;
> + } else if (strcmp(argv[1], "incompat") == 0) {
> + mask = &flags[0].incompat_flags;
> + bits = &flags[1].incompat_flags;
> + } else
> + goto usage;
> +
> + *mask |= bit;
> +
> + if (strcmp(argv[0], "set") == 0)
> + *bits |= bit;
> +
> + return ioctl(fd, BTRFS_IOC_SET_FEATURES, &flags);
> +usage:
> + fprintf(stderr, "usage: SET_FEATURES <set|clear> <compat|compat_ro|incompat> <base-10 bitmask>\n");
> + return -EINVAL;
> +}
> +
> +static int get_supported_features_ioctl(int fd, int argc, char *argv[])
> +{
> + struct btrfs_ioctl_feature_flags flags[3];
> + int ret;
> + int i;
> +
> + ret = ioctl(fd, BTRFS_IOC_GET_SUPPORTED_FEATURES, &flags);
> + if (ret)
> + return -errno;
> +
> + for (i = 0; i < 3; i++)
> + printf("0x%llx 0x%llx 0x%llx ",
> + (unsigned long long)flags[i].compat_flags,
> + (unsigned long long)flags[i].compat_ro_flags,
> + (unsigned long long)flags[i].incompat_flags);
> +
> + printf("\n");
> + return 0;
> +usage:
> + fprintf(stderr,
> + "usage: GET_SUPPORTED_FEATURES <supported|settable|clearable>\n");
> + return -EINVAL;
> +}
> #define IOCTL_TABLE_ENTRY(_ioctl_name, _handler) \
> { .name = #_ioctl_name, .ioctl_cmd = BTRFS_IOC_##_ioctl_name, \
> .handler = _handler, }
> @@ -37,6 +127,9 @@ struct ioctl_table_entry {
>
> static struct ioctl_table_entry ioctls[] = {
> IOCTL_TABLE_ENTRY(GLOBAL_RSV, global_rsv_ioctl),
> + IOCTL_TABLE_ENTRY(GET_FEATURES, get_features_ioctl),
> + IOCTL_TABLE_ENTRY(SET_FEATURES, set_features_ioctl),
> + IOCTL_TABLE_ENTRY(GET_SUPPORTED_FEATURES, get_supported_features_ioctl),
> };
>
> int
> diff --git a/tests/btrfs/102 b/tests/btrfs/102
> new file mode 100755
> index 0000000..77f2162
> --- /dev/null
> +++ b/tests/btrfs/102
> @@ -0,0 +1,263 @@
> +#!/bin/bash
> +# FA QA Test No. 102
> +#
> +# Test online feature publishing
> +# This test doesn't test the changing of features. It does test that
> +# the proper publishing bits and permissions match up with
> +# the expected values.
> +#
> +#-----------------------------------------------------------------------
> +# Copyright (c) 2013 SUSE, 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
> +
> +# get standard environment, filters and checks
> +. ./common/rc
> +. ./common/filter.btrfs
> +
> +_supported_fs btrfs
> +_supported_os Linux
> +_require_scratch
> +_require_command $BTRFS_SHOW_SUPER_PROG btrfs-show-super

You don't need the extra btrfs-show-super here, the var should be good enough.

> +
> +_scratch_mkfs > /dev/null 2>&1
> +_scratch_mount
> +
> +fsid() {
> + $BTRFS_UTIL_PROG filesystem show $1|awk '/uuid:/ {print $NF}'
> +}
> +
> +check_features() {
> + reserved="$2"
> + method="$3"
> + if [ "$1" != 0 ]; then
> + echo "$method: failed: $reserved"
> + exit 1
> + fi
> +}
> +
> +error=false
> +
> +# test -w will always return true if root is making the call.
> +# This would be true in most cases, but for sysfs files, the permissions
> +# are enforced even for root.
> +is_writeable() {
> + local file=$1
> + mode=$(stat -c "0%a" "$file")
> + mode=$(( $mode & 0200 ))
> +
> + [ "$mode" -eq 0 ] && return 1
> + return 0
> +}
> +
> +# ioctl
> +read -a features < <(src/btrfs_ioctl_helper $SCRATCH_MNT GET_FEATURES 2>&1)
> +check_features $? "$features" "GET_FEATURES"
> +
> +read -a supp_features < <(src/btrfs_ioctl_helper $SCRATCH_MNT GET_SUPPORTED_FEATURES 2>&1)
> +check_features $? "$features" "GET_SUPPORTED_FEATURES"
> +
> +# Sysfs checks
> +fsid=$(fsid $SCRATCH_DEV)
> +sysfs_base="/sys/fs/btrfs"
> +
> +# TODO Add tool to enable and test unknown feature bits
> +get_feature_mask() {
> + class=""
> + case "$attr" in
> + mixed_backref) class=incompat; bit=0x1 ;;
> + default_subvol) class=incompat; bit=0x2 ;;
> + mixed_groups) class=incompat; bit=0x4 ;;
> + compress_lzo) class=incompat; bit=0x8 ;;
> + compress_lsov2) class=incompat; bit=0x10 ;;
> + big_metadata) class=incompat; bit=0x20 ;;
> + extended_iref) class=incompat; bit=0x40 ;;
> + raid56) class=incompat; bit=0x80 ;;
> + skinny_metadata)class=incompat; bit=0x100 ;;
> + compat:*) class=compat; bit=${attr##compat:} ;;
> + compat_ro:*) class=compat_ro; bit=${attr##compat_ro:} ;;
> + incompat:*) class=incompat; bit=${attr##incompat:} ;;
> + esac
> + if [ -z "$class" ]; then
> + echo "Unknown feature name $attr. xfstests needs updating." \
> + " Skipping the test of sysfs values to superblock values" \
> + >> $seqres.full
> + return
> + fi
> +
> + echo "$class $bit"
> +}
> +
> +get_changeable_mask() {
> + local class=$1
> + local index=0
> + if [ "$class" = "compat" ]; then
> + index=0
> + elif [ "$class" = "compat_ro" ]; then
> + index=1
> + elif [ "$class" = "incompat" ]; then
> + index=2
> + fi
> + local set_index=$(( $index + 3 ))
> + local clear_index=$(( $index + 6 ))
> +
> + local mask=$(( ${supp_features[$set_index]} | \
> + ${supp_features[$clear_index]} ))
> +
> + echo $mask
> +}
> +
> +# Check enabled features in sysfs vs what the superblock claims
> +sysfs_features=(0 0 0)
> +for file in $sysfs_base/$fsid/features/*; do
> + attr=$(basename $file)
> + val=$(cat $file)
> + read class bit < <(get_feature_mask $attr)
> +
> + # A file that exists but has a 0 value means that it's changeable
> + if [ "$val" -eq 0 ]; then
> + if [ ! -e "$sysfs_base/features/$attr" ]; then
> + echo "$fsid/$attr exists with a 0 value but" \
> + "features/$attr doesn't exist."
> + error=true
> + continue
> + elif ! is_writeable "$file"; then
> + echo "$attr is not writable but exists and has a" \
> + "0 value."
> + error=true
> + fi
> +
> + mask=$(get_changeable_mask $class)
> + if [ "$(( $bit & ~$mask ))" -ne 0 ]; then
> + echo "$attr is writable but GET_SUPPORTED_FEATURES" \
> + "ioctl claims it shouldn't be."
> + error=true
> + fi
> +
> + continue
> + fi
> + if [ "$class" = "compat" ]; then
> + sysfs_features[0]=$(( ${sysfs_features[0]} | $bit ))
> + elif [ "$class" = "compat_ro" ]; then
> + sysfs_features[1]=$(( ${sysfs_features[1]} | $bit ))
> + elif [ "$class" = "incompat" ]; then
> + sysfs_features[2]=$(( ${sysfs_features[2]} | $bit ))
> + else
> + # We will end up with a bit set in the superblock that
> + # doesn't have a matching bit here. The feature-bit to name
> + # mapping must be kept up-to-date for this test to succeed.
> + echo "Unknown feature name $attr. xfstests needs updating." \
> + "Skipping the test of sysfs values to superblock values" \
> + >> $seqres.full
> + skip_sysfs_super_check=true
> + fi
> +done
> +
> +for file in $sysfs_base/features/*; do
> + attr=$(basename $file)
> + val=$(cat $file)
> + if [ "$val" -gt 0 ]; then
> + if [ ! -e "$sysfs_base/$fsid/features/$attr" ]; then
> + echo "features/$attr has a nonzero value ($val)" \
> + "but $fsid/features/$attr doesn't exist"
> + error=true
> + continue
> + fi
> + if ! is_writeable "$sysfs_base/$fsid/features/$attr"; then
> + echo "features/$attr has a nonzero value ($val)" \
> + "but $fsid/features/$attr is not writable"
> + error=true
> + continue
> + fi
> + continue
> + fi
> +
> + [ ! -e "$sysfs_base/$fsid/features/$attr" ] && continue
> +
> + if is_writeable "$sysfs_base/$fsid/features/$attr"; then
> + echo "features/$attr has a zero value but" \
> + "$fsid/features/$attr is writable."
> + error=true
> + continue
> + fi
> +
> + read class bit < <(get_feature_mask $attr)
> + mask=$(get_changeable_mask $class)
> + if [ "$(( $bit & $mask ))" -ne 0 ]; then
> + echo "$attr isn't writable but GET_SUPPORTED_FEATURES" \
> + "ioctl claims it should be."
> + error=true
> + continue
> + fi
> +done
> +
> +umount $SCRATCH_MNT > /dev/null 2>&1
> +
> +fields=("compat" "compat_ro" "incompat")
> +declare -a disk_flags
> +get_disk_flags() {
> + local index=$1
> +
> + # Grab the flags from the superblock directly to compare
> + disk_flags[$index]=$($BTRFS_SHOW_SUPER_PROG $SCRATCH_DEV | \
> + grep "^${fields[$index]}_flags"|awk '{print $NF}')
> +}
> +
> +check_ioctl_flags() {
> + local index=$1
> + local flags=${features[$index]}
> +
> + if [ "$flags" != "${disk_flags[$index]}" ]; then
> + echo "ioctl returned different ${fields[$index]} flags" \
> + "($flags) than those contained in superblock" \
> + "(${disk_flags[$index]})"
> + error=true
> + fi
> +}
> +
> +check_sysfs_flags() {
> + local index=$1
> + $skip_sysfs_super_check || return
> +
> + flags=$(printf "0x%llx" ${sysfs_features[$index]})
> + if [ "$flags" != "${disk_flags[$index]}" ]; then
> + echo "sysfs returned different ${fields[$index]}" \
> + "flags ($flags) than those contained in" \
> + "superblock (${disk_flags[$index]})"
> + error=true
> + fi
> +}
> +
> +
> +for index in $(seq 0 2); do
> + get_disk_flags "$index"
> + check_ioctl_flags "$index"
> + check_sysfs_flags "$index"
> +done
> +
> +$error && exit 1
> +
> +#
> +echo "Silence is golden"
> +status=0
> +exit
> diff --git a/tests/btrfs/102.out b/tests/btrfs/102.out
> new file mode 100644
> index 0000000..28b7182
> --- /dev/null
> +++ b/tests/btrfs/102.out
> @@ -0,0 +1,2 @@
> +== QA output created by 102
> +Silence is golden
> diff --git a/tests/btrfs/103 b/tests/btrfs/103
> new file mode 100755
> index 0000000..ff083c7
> --- /dev/null
> +++ b/tests/btrfs/103
> @@ -0,0 +1,188 @@
> +#!/bin/bash
> +# FA QA Test No. 103
> +#
> +# Test online feature changing via ioctl
> +#
> +#-----------------------------------------------------------------------
> +# Copyright (c) 2013 SUSE, All Rights Reserved.
> +#
> +# This program is free software; you can redistribute it and/or
> +# modify it under the terms of the GNU General Public License as
> +# published by the Free Software Foundation.
> +#
> +# This program is distributed in the hope that it would be useful,
> +# but WITHOUT ANY WARRANTY; without even the implied warranty of
> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> +# GNU General Public License for more details.
> +#
> +# You should have received a copy of the GNU General Public License
> +# along with this program; if not, write the Free Software Foundation,
> +# Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
> +#-----------------------------------------------------------------------
> +
> +seq=$(basename $0)
> +seqres=$RESULT_DIR/$seq
> +echo "== QA output created by $seq"
> +
> +here=$(pwd)
> +tmp=/tmp/$$
> +status=1
> +
> +# get standard environment, filters and checks
> +. ./common/rc
> +. ./common/filter.btrfs
> +
> +_supported_fs btrfs
> +_supported_os Linux
> +_require_scratch
> +_require_command $BTRFS_SHOW_SUPER_PROG btrfs-show-super
> +

Same here.

> +IOCTL=src/btrfs_ioctl_helper
> +
> +check_features() {
> + reserved="$2"
> + method="$3"
> + if [ "$1" != 0 ]; then
> + echo "$method: failed: $reserved"
> + exit 1
> + fi
> + if [ "$reserved" = "Not implemented." ]; then
> + echo "Skipping ioctl $method test. Not implemented." \
> + >> $seqres.full
> + echo "Silence is golden."
> + exit 0
> + fi
> +}
> +
> +# 3 values, one for each each of the fields
> +update_features() {
> + read -a features < <($IOCTL $SCRATCH_MNT GET_FEATURES 2>&1)
> + check_features $? "${features[@]}" "GET_FEATURES"
> +}
> +
> +set_feature() {
> + local field=$1
> + local bits=$2
> + local class=${fields[$field]}
> + local old=${features[$field]}
> + msg=$($IOCTL $SCRATCH_MNT SET_FEATURES set $class $bits)
> + check_features $? "$msg" "SET_FEATURES"
> + update_features
> + local new=${features[$field]}
> +
> + if [ "$old" = "$new" ]; then
> + echo "Feature setting failed"
> + exit 1
> + fi
> + expected=$(( $old | $bits ))
> + new=$(( $new ))
> + if [ "$expected" -ne "$new" ]; then
> + echo "Feature setting failed; Got $new, expected $expected"
> + exit 1
> + fi
> + echo $new
> +}
> +
> +clear_feature() {
> + local field=$1
> + local bits=$2
> + local class=${fields[$field]}
> + local old=${features[$field]}
> + msg=$($IOCTL $SCRATCH_MNT SET_FEATURES clear $class $bits)
> + check_features $? "$msg" "SET_FEATURES"
> + update_features
> + local new="${features[$field]}"
> +
> + if [ "$old" = "$new" ]; then
> + echo "Feature clearing failed"
> + exit 1
> + fi
> + expected=$(( $old & ~$bits ))
> + new=$(( $new ))
> + if [ "$expected" -ne "$new" ]; then
> + echo "Feature clearing failed; Got $new, expected $expected"
> + exit 1
> + fi
> +}
> +
> +get_disk_flags () {
> + local index=$1
> + $BTRFS_SHOW_SUPER_PROG $SCRATCH_DEV | grep ^${fields[$index]}_flags | \
> + awk '{print $NF}'
> +}
> +
> +check_flags() {
> + local index=$1
> + local expected=$(( $2 ))
> + disk_flags="$(( $(get_disk_flags $index) ))"
> + if [ "$disk_flags" -ne "$expected" ]; then
> + echo "mismatch: $disk_flags-$expected"
> + error=true
> + fi
> +}
> +
> +error=false
> +fields=("compat" "compat_ro" "incompat")
> +
> +_scratch_mkfs > /dev/null 2>&1
> +_scratch_mount
> +
> +update_features
> +
> +# 9 values; 3 each for supported, settable, and clearable
> +read -a supp_features < <($IOCTL $SCRATCH_MNT GET_SUPPORTED_FEATURES 2>&1)
> +check_features $? "$supp_features" "GET_SUPPORTED_FEATURES"
> +
> +# Cycle through settable features.
> +# Set the feature
> +# Reload ioctl version and test against expected new value
> +# Unmount and test against expected new value
> +# Reount
> +settable() {
> + echo "${supp_features[$(( $1 + 3 ))]}"
> +}
> +did_set=false
> +for field in $(seq 0 2); do
> + fset="$(settable $field)"
> + for n in $(seq 0 63); do
> + old="${features[$field]}"
> + v="$(( $fset & (1 << $n) ))"
> + [ "$v" -eq 0 ] && continue
> + new="$(set_feature $field $v)"
> + umount $SCRATCH_MNT > /dev/null 2>&1
> + expected="$(( $old | $v ))"
> + check_flags "$field" "$expected"
> + _scratch_mount
> + did_set=true
> + done
> +done
> +$did_set || echo "No online-settable features to test." >> $seqres.full
> +
> +# Repeat with clearing features
> +clearable() {
> + echo "${supp_features[$(( $1 + 6 ))]}"
> +}
> +did_clear=false
> +for field in $(seq 0 2); do
> + fclear="$(clearable $field)"
> + for n in $(seq 0 63); do
> + v="$(( $fclear & (1 << $n) ))"
> + [ "$v" -eq 0 ] && continue
> +
> + new="$(clear_feature $field $v)"
> + umount $SCRATCH_MNT > /dev/null 2>&1
> + expected=$(( $old &~ $v ))
> + check_flags $field $expected
> + _scratch_mount
> + did_clear=true
> + done
> +done
> +$did_clear || echo "No online-clearable features to test." >> $seqres.full
> +
> +umount $SCRATCH_MNT > /dev/null 2>&1
> +
> +$error && exit 1
> +
> +echo "Silence is golden"
> +status=0
> +exit
> diff --git a/tests/btrfs/103.out b/tests/btrfs/103.out
> new file mode 100644
> index 0000000..aa66c3b
> --- /dev/null
> +++ b/tests/btrfs/103.out
> @@ -0,0 +1,2 @@
> +== QA output created by 103
> +Silence is golden
> diff --git a/tests/btrfs/104 b/tests/btrfs/104
> new file mode 100755
> index 0000000..3ac4040
> --- /dev/null
> +++ b/tests/btrfs/104
> @@ -0,0 +1,186 @@
> +#!/bin/bash
> +# FA QA Test No. 104
> +#
> +# Test online feature changing via sysfs
> +#
> +#-----------------------------------------------------------------------
> +# Copyright (c) 2013 SUSE, 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
> +
> +# get standard environment, filters and checks
> +. ./common/rc
> +. ./common/filter.btrfs
> +
> +_supported_fs btrfs
> +_supported_os Linux
> +_require_scratch
> +_require_command $BTRFS_SHOW_SUPER_PROG btrfs-show-super
> +

And here. Thanks,

Josef