Re: [PATCH -next 4/8] ext4: fix miss unlock 'sb->s_umount' in extents_kunit_init()

[Ritesh Harjani (IBM) <ritesh.list@gmail.com>]

Ye Bin <yebin@huaweicloud.com> writes:

> From: Ye Bin <yebin10@huawei.com>
>
> There's warning as follows when do ext4 kunit test:
> WARNING: kunit_try_catch/15923 still has locks held!
> 7.0.0-rc3-next-20260309-00028-g73f965a1bbb1-dirty #281 Tainted: G            E    N
> 1 lock held by kunit_try_catch/15923:

Strange lockdep didn't complaint this for me.. I had lockdep enabled in
my config.

>  #0: ffff888139f860e0 (&type->s_umount_key#70/1){+.+.}-{4:4}, at: alloc_super.constprop.0+0x172/0xa90
> Call Trace:
>  <TASK>
>  dump_stack_lvl+0x180/0x1b0
>  debug_check_no_locks_held+0xc8/0xd0
>  do_exit+0x1502/0x2b20
>  kthread+0x3a9/0x540
>  ret_from_fork+0xa76/0xdf0
>  ret_from_fork_asm+0x1a/0x30
>
> As sget() will return 'sb' which holds 's->s_umount' lock. However,
> "extents-test" miss unlock this lock.
> So unlock 's->s_umount' in the end of extents_kunit_init().
>
> Fixes: cb1e0c1d1fad ("ext4: kunit tests for extent splitting and conversion")
> Signed-off-by: Ye Bin <yebin10@huawei.com>
> ---
>  fs/ext4/extents-test.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/fs/ext4/extents-test.c b/fs/ext4/extents-test.c
> index 9e055f399167..5a5016ea1ecc 100644
> --- a/fs/ext4/extents-test.c
> +++ b/fs/ext4/extents-test.c
> @@ -307,6 +307,8 @@ static int extents_kunit_init(struct kunit *test)
>  	kunit_activate_static_stub(test, ext4_ext_zeroout, ext4_ext_zeroout_stub);
>  	kunit_activate_static_stub(test, ext4_issue_zeroout,
>  				   ext4_issue_zeroout_stub);
> +	up_write(&sb->s_umount);
> +

Can we re-arrange these patches please?
Let's bring the error handling fix first (I think i.e. patch-6 in this
series) so that, s_umount lock also gets unlocked properly from the
error handling paths as well.

With that, I agree releasing the s_umount lock is the right thing to do
here which is taken in:
sget()
  alloc_super()
    down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING);


So feel free to add:
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>

-ritesh