[PATCH] generic/735: improve test by incorporating extra hints

[Disha Goel <disgoel@linux.ibm.com>]

On power systems with 64k block size (where default page size is 64k) we
encountered a kernel oops due to an integer overflow issue when writing
near the last logical block of a file. The allocator could allocate a
range where the end exceeds the maximum supported logical block
(UINT32_MAX), leading to a subsequent BUG_ON. This issue has been
addressed in the upstream kernel with commit 2dcf5fde6dff
("ext4: prevent the normalized size from exceeding EXT_MAX_BLOCKS").

	==================================================
	kernel BUG at fs/ext4/mballoc.c:4448!
	Oops: Exception in kernel mode, sig: 5 [#1]
	CPU: 8 PID: 2880554 Comm: xfs_io
	NIP ext4_mb_use_inode_pa+0x110/0x160 [ext4]
	LR ext4_mb_use_inode_pa+0xac/0x160 [ext4]
	Call Trace:
		ext4_mb_new_inode_pa+0x134/0x3a0 [ext4]
		ext4_mb_try_best_found+0x158/0x280 [ext4]
		ext4_mb_regular_allocator+0x16c/0x940 [ext4]
		ext4_mb_new_blocks+0x610/0x960 [ext4]
		ext4_ext_map_blocks+0x858/0xa90 [ext4]
		ext4_map_blocks+0x218/0x800 [ext4]
		ext4_iomap_alloc+0x10c/0x260 [ext4]
		ext4_iomap_begin+0xfc/0x1f0 [ext4]
		iomap_iter+0xf0/0x190
		__iomap_dio_rw+0x208/0x690
		iomap_dio_rw+0x20/0x80
		ext4_dio_write_iter+0x210/0x4d0 [ext4]
		vfs_write+0x364/0x4e0
		sys_pwrite64+0xd4/0x120
		system_call_exception+0x164/0x310
		system_call_vectored_common+0xe8/0x278
	==================================================

This test has been extended to provide a hint about the relevant fix
in case of failure.

Signed-off-by: Disha Goel <disgoel@linux.ibm.com>
---
 tests/generic/735 | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/tests/generic/735 b/tests/generic/735
index 75b23d5e..0ba111a6 100755
--- a/tests/generic/735
+++ b/tests/generic/735
@@ -6,16 +6,19 @@
 #
 # Append writes to a file with logical block numbers close to 0xffffffff
 # 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")
-#
+# 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")
+# commit 2dcf5fde6dff ("ext4: prevent the normalized size from exceeding EXT_MAX_BLOCKS")
+
 . ./common/preamble
 . ./common/populate
 _begin_fstest auto quick insert prealloc
 
 # real QA test starts here
-[[ "$FSTYP" =~ ext[0-9]+ ]] && _fixed_by_kernel_commit bc056e7163ac \
-	"ext4: fix BUG in ext4_mb_new_inode_pa() due to overflow"
+if [[ "$FSTYP" =~ ext[0-9]+ ]]; then
+	_fixed_by_kernel_commit bc056e7163ac "ext4: fix BUG in ext4_mb_new_inode_pa() due to overflow"
+	_fixed_by_kernel_commit 2dcf5fde6dff "ext4: prevent the normalized size from exceeding EXT_MAX_BLOCKS"
+fi
 
 _require_odirect
 _require_xfs_io_command "falloc"
-- 
2.39.1