[PATCH] xfs: test xfs_growfs with too-small size expansion

[Zorro Lang <zlang@kernel.org>]

This's a regression test of 84712492e6da ("xfs: short circuit
xfs_growfs_data_private() if delta is zero").

If try to do growfs with "too-small" size expansion, might lead to a
delta of "0" in xfs_growfs_data_private(), then end up in the shrink
case and emit the EXPERIMENTAL warning even if we're not changing
anything at all.

Signed-off-by: Zorro Lang <zlang@redhat.com>
---
 tests/xfs/999     | 53 +++++++++++++++++++++++++++++++++++++++++++++++
 tests/xfs/999.out |  2 ++
 2 files changed, 55 insertions(+)
 create mode 100755 tests/xfs/999
 create mode 100644 tests/xfs/999.out

diff --git a/tests/xfs/999 b/tests/xfs/999
new file mode 100755
index 00000000..09192ba3
--- /dev/null
+++ b/tests/xfs/999
@@ -0,0 +1,53 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2024 Red Hat, Inc.  All Rights Reserved.
+#
+# FS QA Test No. 999
+#
+# Test xfs_growfs with "too-small" size expansion, which lead to a delta of "0"
+# in xfs_growfs_data_private. This's a regression test of 84712492e6da ("xfs:
+# short circuit xfs_growfs_data_private() if delta is zero").
+#
+. ./common/preamble
+_begin_fstest auto quick growfs
+
+_cleanup()
+{
+	local dev
+        $UMOUNT_PROG $LOOP_MNT 2>/dev/null
+	dev=$(losetup -j testfile | cut -d: -f1)
+	losetup -d $dev 2>/dev/null
+        rm -rf $LOOP_IMG $LOOP_MNT
+        cd /
+        rm -f $tmp.*
+}
+
+# real QA test starts here
+_supported_fs xfs
+_fixed_by_kernel_commit 84712492e6da \
+	"xfs: short circuit xfs_growfs_data_private() if delta is zero"
+_require_test
+_require_loop
+_require_xfs_io_command "truncate"
+
+LOOP_IMG=$TEST_DIR/$seq.dev
+LOOP_MNT=$TEST_DIR/$seq.mnt
+rm -rf $LOOP_IMG $LOOP_MNT
+mkdir -p $LOOP_MNT
+# 1G image
+$XFS_IO_PROG -f -c "truncate 1073741824" $LOOP_IMG
+$MKFS_XFS_PROG -f $LOOP_IMG >$seqres.full
+# extend by just 8K
+$XFS_IO_PROG -f -c "truncate 1073750016" $LOOP_IMG
+_mount -oloop $LOOP_IMG $LOOP_MNT
+# A known bug shows "XFS_IOC_FSGROWFSDATA xfsctl failed: No space left on
+# device" at here, refer to _fixed_by_kernel_commit above
+$XFS_GROWFS_PROG $LOOP_MNT >$seqres.full
+if [ $? -ne 0 ];then
+	echo "xfs_growfs fails!"
+fi
+
+echo "Silence is golden"
+# success, all done
+status=0
+exit
diff --git a/tests/xfs/999.out b/tests/xfs/999.out
new file mode 100644
index 00000000..3b276ca8
--- /dev/null
+++ b/tests/xfs/999.out
@@ -0,0 +1,2 @@
+QA output created by 999
+Silence is golden
-- 
2.43.0