From: Zhang Yi mb_set_largest_free_order() requires the parameter bb_largest_free_order and the list bb_largest_free_order_node to be initialized, and mb_update_avg_fragment_size() requires the parameter bb_avg_fragment_size_order and bb_avg_fragment_size_node to be initialized too. But the test_mb_mark_used kunit tests do not init these parameters, and trigger the following crash issue. Pid: 35, comm: kunit_try_catch Tainted: G W N 6.16.0-rc4-00031-gbbe11dd13a3f-dirty RIP: 0033:mb_set_largest_free_order+0x5c/0xc0 RSP: 00000000a0883d98 EFLAGS: 00010206 RAX: 0000000060aeaa28 RBX: 0000000060a2d400 RCX: 0000000000000008 RDX: 0000000060aea9c0 RSI: 0000000000000000 RDI: 0000000060864000 RBP: 0000000060aea9c0 R08: 0000000000000000 R09: 0000000060a2d400 R10: 0000000000000400 R11: 0000000060a9cc00 R12: 0000000000000006 R13: 0000000000000400 R14: 0000000000000305 R15: 0000000000000000 Kernel panic - not syncing: Segfault with no mm CPU: 0 UID: 0 PID: 35 Comm: kunit_try_catch Tainted: G W N 6.16.0-rc4-00031-gbbe11dd13a3f-dirty #36 NONE Tainted: [W]=WARN, [N]=TEST Stack: 60210c60 00000200 60a9e400 00000400 40060300280 60864000 60a9cc00 60a2d400 00000400 60aea9c0 60a9cc00 60aea9c0 Call Trace: [<60210c60>] ? ext4_mb_generate_buddy+0x1f0/0x230 [<60215c3b>] ? test_mb_mark_used+0x28b/0x4e0 [<601df5bc>] ? ext4_get_group_desc+0xbc/0x150 [<600bf1c0>] ? ktime_get_ts64+0x0/0x190 [<60086370>] ? to_kthread+0x0/0x40 [<602b559b>] ? kunit_try_run_case+0x7b/0x100 [<60086370>] ? to_kthread+0x0/0x40 [<602b7850>] ? kunit_generic_run_threadfn_adapter+0x0/0x30 [<602b7862>] ? kunit_generic_run_threadfn_adapter+0x12/0x30 [<60086a51>] ? kthread+0xf1/0x250 [<6004a541>] ? new_thread_handler+0x41/0x60 [ERROR] Test: test_mb_mark_used: 0 tests run! Fixes: bbe11dd13a3f ("ext4: fix largest free orders lists corruption on mb_optimize_scan switch") Reported-by: Theodore Ts'o Closes: https://lore.kernel.org/linux-ext4/20250724145437.GD80823@mit.edu/ Signed-off-by: Zhang Yi --- This patch applies to the kernel that has only merged bbe11dd13a3f ("ext4: fix largest free orders lists corruption on mb_optimize_scan switch"), but not merged 458bfb991155 ("ext4: convert free groups order lists to xarrays"). fs/ext4/mballoc-test.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/fs/ext4/mballoc-test.c b/fs/ext4/mballoc-test.c index d634c12f1984..ba939be0ec55 100644 --- a/fs/ext4/mballoc-test.c +++ b/fs/ext4/mballoc-test.c @@ -802,6 +802,10 @@ static void test_mb_mark_used(struct kunit *test) KUNIT_ASSERT_EQ(test, ret, 0); grp->bb_free = EXT4_CLUSTERS_PER_GROUP(sb); + grp->bb_largest_free_order = -1; + grp->bb_avg_fragment_size_order = -1; + INIT_LIST_HEAD(&grp->bb_largest_free_order_node); + INIT_LIST_HEAD(&grp->bb_avg_fragment_size_node); mbt_generate_test_ranges(sb, ranges, TEST_RANGE_COUNT); for (i = 0; i < TEST_RANGE_COUNT; i++) test_mb_mark_used_range(test, &e4b, ranges[i].start, @@ -875,6 +879,10 @@ static void test_mb_free_blocks(struct kunit *test) ext4_unlock_group(sb, TEST_GOAL_GROUP); grp->bb_free = 0; + grp->bb_largest_free_order = -1; + grp->bb_avg_fragment_size_order = -1; + INIT_LIST_HEAD(&grp->bb_largest_free_order_node); + INIT_LIST_HEAD(&grp->bb_avg_fragment_size_node); memset(bitmap, 0xff, sb->s_blocksize); mbt_generate_test_ranges(sb, ranges, TEST_RANGE_COUNT); -- 2.46.1