[PATCH 2/2] btrfs: test active zone tracking

[Naohiro Aota <naohiro.aota@wdc.com>]

A ZNS device limits the number of active zones, which is the number of
zones can be written at the same time. To deal with the limit, btrfs's
zoned mode tracks which zone (corresponds to a block group on the SINGLE
profile) is active, and finish a zone if necessary.

This test checks if the active zone tracking and the finishing of zones
works properly. First, it fills <number of max active zones> zones
mostly. And, run some data/metadata stress workload to force btrfs to use a
new zone.

This test fails on an older kernel (e.g, 5.18.2) like below.

btrfs/292
[failed, exit status 1]- output mismatch (see /host/btrfs/292.out.bad)
    --- tests/btrfs/292.out     2022-09-15 07:52:18.000000000 +0000
    +++ /host/btrfs/292.out.bad 2022-09-15 07:59:14.290967793 +0000
    @@ -1,2 +1,5 @@
     QA output created by 292
    -Silence is golden
    +stress_data_bgs failed
    +stress_data_bgs_2 failed
    +failed: '/bin/btrfs subvolume snapshot /mnt/scratch /mnt/scratch/snap825'
    +(see /host/btrfs/292.full for details)
    ...
    (Run 'diff -u /var/lib/xfstests/tests/btrfs/292.out /host/btrfs/292.out.bad'  to see the entire diff)

The failure is fixed with a series "btrfs: zoned: fix active zone tracking
issues" [1] (upstream commits from 65ea1b66482f ("block: add bdev_max_segments()
helper") to 2ce543f47843 ("btrfs: zoned: wait until zone is finished when
allocation didn't progress")).

[1] https://lore.kernel.org/linux-btrfs/cover.1657321126.git.naohiro.aota@wdc.com/

Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
---
 common/zbd          |  12 ++++
 tests/btrfs/292     | 137 ++++++++++++++++++++++++++++++++++++++++++++
 tests/btrfs/292.out |   2 +
 3 files changed, 151 insertions(+)
 create mode 100755 tests/btrfs/292
 create mode 100644 tests/btrfs/292.out

diff --git a/common/zbd b/common/zbd
index 329bb7be6b7b..19a59fd27e69 100644
--- a/common/zbd
+++ b/common/zbd
@@ -2,8 +2,20 @@
 # Common zoned block device specific functions
 #
 
+. common/rc
 . common/filter
 
+_require_limited_active_zones() {
+    local dev=$1
+    local sysfs=$(_sysfs_dev ${dev})
+    local attr="${sysfs}/queue/max_active_zones"
+
+    [ -e "${attr}" ] || _notrun "cannot find queue/max_active_zones. Maybe non-zoned device?"
+    if [ $(cat "${attr}") == 0 ]; then
+	_notrun "this test requires limited active zones"
+    fi
+}
+
 _zone_capacity() {
     local phy=$1
     local dev=$2
diff --git a/tests/btrfs/292 b/tests/btrfs/292
new file mode 100755
index 000000000000..30c027c4ba5f
--- /dev/null
+++ b/tests/btrfs/292
@@ -0,0 +1,137 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2022 Western Digital Corporation.  All Rights Reserved.
+#
+# FS QA Test 292
+#
+# Test that an active zone is properly reclaimed to allow the further
+# allocations, even if the active zones are mostly filled.
+#
+. ./common/preamble
+_begin_fstest auto quick snapshot zone
+
+# Import common functions.
+. ./common/btrfs
+. ./common/zbd
+
+# real QA test starts here
+
+_supported_fs btrfs
+_require_scratch
+_require_zoned_device "$SCRATCH_DEV"
+_require_limited_active_zones "$SCRATCH_DEV"
+
+_require_command "$BLKZONE_PROG" blkzone
+_require_fio
+_require_btrfs_command inspect-internal dump-tree
+
+# This test requires specific data space usage, skip if we have compression
+# enabled.
+_require_no_compress
+
+max_active=$(cat $(_sysfs_dev ${SCRATCH_DEV})/queue/max_active_zones)
+
+# Fill the zones leaving the last 1MB
+fill_active_zones() {
+    # Asuumes we have the same capacity between zones.
+    local capacity=$(_zone_capacity 0)
+    local fill_size=$((capacity - 1024 * 1024))
+
+    for x in $(seq ${max_active}); do
+	dd if=/dev/zero of=${SCRATCH_MNT}/fill$(printf "%02d" $x) bs=${fill_size} \
+	   count=1 oflag=direct 2>/dev/null
+	$BTRFS_UTIL_PROG filesystem sync ${SCRATCH_MNT}
+
+	local nactive=$($BLKZONE_PROG report ${SCRATCH_DEV} | grep oi | wc -l)
+	if [[ ${nactive} == ${max_active} ]]; then
+	    break
+	fi
+    done
+
+    echo "max active zones: ${max_active}" >> $seqres.full
+    $BLKZONE_PROG report ${SCRATCH_DEV} | grep oi | cat -n >> $seqres.full
+}
+
+workout() {
+    local func="$1"
+
+    _scratch_mkfs >/dev/null 2>&1
+    _scratch_mount
+
+    fill_active_zones
+    eval "$func"
+    local ret=$?
+
+    _scratch_unmount
+    _check_btrfs_filesystem ${SCRATCH_DEV}
+
+    return $ret
+}
+
+stress_data_bgs() {
+    # This dd fails with ENOSPC, which should not :(
+    dd if=/dev/zero of=${SCRATCH_MNT}/large bs=64M count=1 oflag=sync \
+       >>$seqres.full 2>&1
+}
+
+stress_data_bgs_2() {
+    # This dd fails with ENOSPC, which should not :(
+    dd if=/dev/zero of=${SCRATCH_MNT}/large bs=64M count=10 conv=fsync \
+       >>$seqres.full 2>&1 &
+    local pid1=$!
+
+    dd if=/dev/zero of=${SCRATCH_MNT}/large2 bs=64M count=10 conv=fsync \
+       >>$seqres.full 2>&1 &
+    local pid2=$!
+
+    wait $pid1; local ret1=$?
+    wait $pid2; local ret2=$?
+
+    if [ $ret1 -ne 0 -o $ret2 -ne 0 ]; then
+	return 1
+    fi
+    return 0
+}
+
+get_meta_bgs() {
+    $BTRFS_UTIL_PROG inspect-internal dump-tree -t EXTENT ${SCRATCH_DEV} |
+        grep BLOCK_GROUP -A 1 |grep -B1 'METADATA|' |
+        grep -oP '\(\d+ BLOCK_GROUP_ITEM \d+\)'
+}
+
+# This test case does not return the result because
+# _run_btrfs_util_prog will call _fail() in the error case anyway.
+stress_metadata_bgs() {
+    local metabgs=$(get_meta_bgs)
+    local count=0
+
+    while : ; do
+        _run_btrfs_util_prog subvolume snapshot ${SCRATCH_MNT} ${SCRATCH_MNT}/snap$i
+        _run_btrfs_util_prog filesystem sync ${SCRATCH_MNT}
+        cur_metabgs=$(get_meta_bgs)
+        if [[ "${cur_metabgs}" != "${metabgs}" ]]; then
+            break
+        fi
+        i=$((i + 1))
+    done
+}
+
+WORKS=(
+    stress_data_bgs
+    stress_data_bgs_2
+    stress_metadata_bgs
+)
+
+status=0
+for work in "${WORKS[@]}"; do
+    if ! workout "${work}"; then
+	echo "${work} failed"
+	status=1
+    fi
+done
+
+# success, all done
+if [ $status -eq 0 ]; then
+    echo "Silence is golden"
+fi
+exit
diff --git a/tests/btrfs/292.out b/tests/btrfs/292.out
new file mode 100644
index 000000000000..627309d3fbd2
--- /dev/null
+++ b/tests/btrfs/292.out
@@ -0,0 +1,2 @@
+QA output created by 292
+Silence is golden
-- 
2.37.3