[PATCH v3] xfs: add a test for number of open zones on conventional devices

Test that mounts of zoned file systems on conventional devices don't
create more open zones than allowed when the last blocks in one or more
zones have been invalidated.

Signed-off-by: Christoph Hellwig <[email protected]>
---

Changes since v2:
 - use raw mkfs to avoid injecting a real RT device
 - _notrun with a useful message when the mkfs or mount fails due to lack
   of RT device or zoned block device support

 tests/xfs/4201     | 69 ++++++++++++++++++++++++++++++++++++++++++++++
 tests/xfs/4201.out |  1 +
 2 files changed, 70 insertions(+)
 create mode 100755 tests/xfs/4201
 create mode 100644 tests/xfs/4201.out

diff --git a/tests/xfs/4201 b/tests/xfs/4201
new file mode 100755
index 000000000000..56084bca41c0
--- /dev/null
+++ b/tests/xfs/4201
@@ -0,0 +1,69 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2026 Christoph Hellwig.
+#
+# FS QA Test No. 4201
+#
+# Test that mounts of zoned file systems on conventional devices don't create
+# more open zones than allowed when the last blocks in one or more zones have
+# been invalidated.
+#
+
+. ./common/preamble
+_begin_fstest auto quick zone
+
+_require_scratch_nocheck
+_require_odirect
+_require_non_zoned_device $SCRATCH_DEV
+_require_non_zoned_device $SCRATCH_RTDEV
+
+open_zones=5
+blocks=16384
+bsize=4096
+
+zone_size_mib=$((blocks * bsize / 1024 / 1024))
+file_size_mib=$((zone_size_mib / 2))
+nr_files=$((open_zones * 3 - 1))
+
+echo "zone size: $zone_size_mib" >>$seqres.full
+echo "file size: $file_size_mib" >>$seqres.full
+echo "nr files: $nr_files" >>$seqres.full
+
+# don't use _scratch_mkfs/_scratch_mount to avoid injection a real RT device
+$MKFS_XFS_PROG -b size=${bsize} -r zoned=1,rgsize=${blocks}b \
+	$SCRATCH_DEV > "$seqres.full" 2>&1 || \
+		_notrun "Zoned mkfs not supported"
+_mount $SCRATCH_DEV $SCRATCH_MNT -o max_open_zones=${open_zones} || \
+	_notrun "Zoned allocator not supported"
+
+_has_fs_sysfs_attr $SCRATCH_DEV zoned/nr_open_zones || \
+	_notrun "This test requires /sys/fs/${FSTYP}/$SCRATCH_DEV/zoned/nr_open_zones"
+
+for i in $(seq 1 $nr_files); do
+	dd if=/dev/zero of=$SCRATCH_MNT/$i bs=1M count=$file_size_mib \
+		 oflag=direct > /dev/null 2>&1
+done
+
+# delete odd numbered files as they should be at the end of the zones
+for ((i = 0; i < $nr_files; i = $((i + 2)))); do
+	rm $SCRATCH_MNT/$((i + 1))
+done
+
+_scratch_unmount
+_mount $SCRATCH_DEV $SCRATCH_MNT -o max_open_zones=${open_zones}
+
+max_open=$(_get_fs_sysfs_attr $SCRATCH_DEV zoned/max_open_zones)
+nr_open=$(_get_fs_sysfs_attr $SCRATCH_DEV zoned/nr_open_zones)
+
+if [ ${max_open} -ne $((open_zones - 1)) ]; then
+	_fail "Test needs adjustments for multiple open GC zones"
+fi
+
+if [ ${nr_open} -gt ${max_open} ]; then
+	_fail "Too many open zones: $nr_open/$max_open"
+fi
+
+_scratch_unmount
+
+status=0
+exit
diff --git a/tests/xfs/4201.out b/tests/xfs/4201.out
new file mode 100644
index 000000000000..32e395dd4d6d
--- /dev/null
+++ b/tests/xfs/4201.out
@@ -0,0 +1 @@
+QA output created by 4201
-- 
2.53.0