[PATCH] ext4: Regression test of ext4_lblk_t overflow

[Baokun Li <libaokun1@huawei.com>]

Append writes to a file approaching 16T and observe if a kernel crash is
caused by ext4_lblk_t overflow triggering BUG_ON at ext4_mb_new_inode_pa().
This is a regression test for commit bc056e7163ac ("ext4: fix BUG in
ext4_mb_new_inode_pa() due to overflow")

Signed-off-by: Baokun Li <libaokun1@huawei.com>
---
 tests/ext4/062     | 53 ++++++++++++++++++++++++++++++++++++++++++++++
 tests/ext4/062.out |  2 ++
 2 files changed, 55 insertions(+)
 create mode 100755 tests/ext4/062
 create mode 100644 tests/ext4/062.out

diff --git a/tests/ext4/062 b/tests/ext4/062
new file mode 100755
index 00000000..0ae4ed80
--- /dev/null
+++ b/tests/ext4/062
@@ -0,0 +1,53 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2023 HUAWEI.  All Rights Reserved.
+#
+# FS QA Test No. 062
+#
+# Append writes to a file approaching 16T and observe if a kernel crash is
+# caused by ext4_lblk_t overflow triggering BUG_ON at ext4_mb_new_inode_pa().
+# This is a regression test for commit
+# bc056e7163ac ("ext4: fix BUG in ext4_mb_new_inode_pa() due to overflow")
+#
+. ./common/preamble
+_begin_fstest auto quick insert
+
+# real QA test starts here
+_supported_fs ext4
+_fixed_by_kernel_commit bc056e7163ac \
+	"ext4: fix BUG in ext4_mb_new_inode_pa() due to overflow"
+
+_require_xfs_io_command "falloc"
+_require_xfs_io_command "open"
+_require_xfs_io_command "pwrite"
+_require_scratch_size_nocheck $((100 * 1024))   # 100MB in KB
+
+# Initalize a 4k 100M ext4 fs
+dev_size=$((100 * 1024 * 1024))
+MKFS_OPTIONS="-b 4096 $MKFS_OPTIONS" _scratch_mkfs_sized $dev_size \
+	>>$seqres.full 2>&1 || _fail "mkfs failed"
+
+_scratch_mount
+
+# Reserve 1M space
+$XFS_IO_PROG -f -c "falloc 0 1M" "${SCRATCH_MNT}/tmp" >> $seqres.full 2>&1
+
+# Create a file with logical block numbers close to overflow
+$XFS_IO_PROG -f -c "falloc 0 10M" "${SCRATCH_MNT}/file" >> $seqres.full 2>&1
+$XFS_IO_PROG -f -c "finsert 1M 16777203M" "${SCRATCH_MNT}/file" >> $seqres.full 2>&1
+
+# Filling up the free space ensures that the pre-allocated space is the reserved space.
+$XFS_IO_PROG -f -c "falloc 0 80388096" "${SCRATCH_MNT}/fill" >> $seqres.full 2>&1
+
+# Remove reserved space to gain free space for allocation
+rm -f ${SCRATCH_MNT}/tmp
+
+# Trying to allocate two blocks triggers BUG_ON.
+$XFS_IO_PROG -c "open -ad ${SCRATCH_MNT}/file" -c "pwrite -S 0xff 0 8192" >> $seqres.full 2>&1
+
+umount "${SCRATCH_MNT}"
+echo "Silence is golden"
+
+# success, all done
+status=0
+exit
diff --git a/tests/ext4/062.out b/tests/ext4/062.out
new file mode 100644
index 00000000..a1578f48
--- /dev/null
+++ b/tests/ext4/062.out
@@ -0,0 +1,2 @@
+QA output created by 062
+Silence is golden
-- 
2.31.1