[PATCH v3] 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>
---
V1->V2:
	Changes to make the use case more generic, not just for testing
	ext4.(ext4 and xfs have been tested)
V2->V3:
	Clean up the code and remove hardcoding.

 tests/generic/737     | 53 +++++++++++++++++++++++++++++++++++++++++++
 tests/generic/737.out |  2 ++
 2 files changed, 55 insertions(+)
 create mode 100755 tests/generic/737
 create mode 100644 tests/generic/737.out

diff --git a/tests/generic/737 b/tests/generic/737
new file mode 100755
index 00000000..29d428ad
--- /dev/null
+++ b/tests/generic/737
@@ -0,0 +1,53 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2023 HUAWEI.  All Rights Reserved.
+#
+# FS QA Test No. 737
+#
+# 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
+. ./common/populate
+_begin_fstest auto quick insert prealloc
+
+# real QA test starts here
+[[ "$FSTYP" =~ ext* ]] && _fixed_by_kernel_commit bc056e7163ac \
+	"ext4: fix BUG in ext4_mb_new_inode_pa() due to overflow"
+
+_require_odirect
+_require_xfs_io_command "falloc"
+_require_xfs_io_command "finsert"
+
+dev_size=$((100 * 1024 * 1024))
+_scratch_mkfs_sized $dev_size >>$seqres.full 2>&1 || _fail "mkfs failed"
+
+_scratch_mount
+blksz="$(_get_block_size ${SCRATCH_MNT})"
+
+# Reserve 1M space
+$XFS_IO_PROG -f -c "falloc 0 1M" "${SCRATCH_MNT}/tmp" >> $seqres.full
+
+# Create a file (~16T) with logical block numbers close to overflow
+$XFS_IO_PROG -f -c "falloc 0 10M" "${SCRATCH_MNT}/file" >> $seqres.full
+insert_size=$((blksz * 4096 - 10 - 3))
+$XFS_IO_PROG -f -c "finsert 1M ${insert_size}M" "${SCRATCH_MNT}/file" >> $seqres.full
+
+# Filling up the free space ensures that the pre-allocated space is the reserved space.
+nr_free=$(stat -f -c '%f' ${SCRATCH_MNT})
+_fill_fs $((nr_free * blksz)) ${SCRATCH_MNT}/fill $blksz 0 >> $seqres.full 2>&1
+sync
+
+# 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 $((2 * blksz))" >> $seqres.full
+
+echo "Silence is golden"
+
+# success, all done
+status=0
+exit
diff --git a/tests/generic/737.out b/tests/generic/737.out
new file mode 100644
index 00000000..67b83d78
--- /dev/null
+++ b/tests/generic/737.out
@@ -0,0 +1,2 @@
+QA output created by 737
+Silence is golden
-- 
2.31.1