[PATCH v4] ext4: resize fs after set reserved GDT blocks equals 100

[Sun Ke <sunke32@huawei.com>]

Set reserved GDT blocks equals 100, then resize fs, will trigger null
pointer.

Regression test for commit b55c3cd102a6 ext4: add reserved GDT blocks
check.

Signed-off-by: Sun Ke <sunke32@huawei.com>
---
 tests/ext4/057     | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 tests/ext4/057.out |  2 ++
 2 files changed, 48 insertions(+)
 create mode 100755 tests/ext4/057
 create mode 100644 tests/ext4/057.out

diff --git a/tests/ext4/057 b/tests/ext4/057
new file mode 100755
index 00000000..f4bbcd32
--- /dev/null
+++ b/tests/ext4/057
@@ -0,0 +1,46 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2022 HUAWEI.  All Rights Reserved.
+#
+# FS QA Test 057
+#
+# Set reserved GDT blocks equals 100, then resize fs, will trigger null pointer.
+#
+# Regression test for commit
+# b55c3cd102a6 ext4: add reserved GDT blocks check
+#
+. ./common/preamble
+_begin_fstest auto resize quick
+
+# real QA test starts here
+
+# Modify as appropriate.
+_supported_fs ext4
+_fixed_by_kernel_commit b55c3cd102a6 \
+	"ext4: add reserved GDT blocks check"
+
+_require_command "$TUNE2FS_PROG" tune2fs
+_require_command "$RESIZE2FS_PROG" resize2fs
+_require_command "$DEBUGFS_PROG" debugfs
+_require_scratch_size $((1024 * 1024)) #kB
+_require_scratch_nocheck
+
+# set fs size 512M
+dev_size=$((512 * 1024 * 1024))
+MKFS_OPTIONS="-O ^resize_inode $MKFS_OPTIONS" _scratch_mkfs_sized $dev_size \
+	>>$seqres.full 2>&1 || _fail "mkfs failed"
+
+$DEBUGFS_PROG -w -R "set_super_value s_reserved_gdt_blocks 100" $SCRATCH_DEV \
+	>>$seqres.full 2>&1
+
+$DEBUGFS_PROG -R "show_super_stats -h" $SCRATCH_DEV 2>/dev/null | \
+	grep "Reserved GDT blocks"
+
+_scratch_mount
+
+# resize fs will trigger NULL pointer in ext4_flex_group_add
+$RESIZE2FS_PROG $SCRATCH_DEV 1G >> $seqres.full 2>&1
+
+# success, all done
+status=0
+exit
diff --git a/tests/ext4/057.out b/tests/ext4/057.out
new file mode 100644
index 00000000..99423e16
--- /dev/null
+++ b/tests/ext4/057.out
@@ -0,0 +1,2 @@
+QA output created by 057
+Reserved GDT blocks:      100
-- 
2.13.6