Re: [PATCH -next 5/8] ext4: fix miss free super_block in extents_kunit_exit()

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

Ye Bin <yebin@huaweicloud.com> writes:

> From: Ye Bin <yebin10@huawei.com>
>
> There's issue as follows:
> ODEBUG: free active (active state 0) object: ffff88812f2d68a0 object type: percpu_counter hint: 0x0
>  <TASK>
>  debug_check_no_obj_freed+0x3d9/0x4d0
>  kfree+0x2bb/0x6c0
>  extents_kunit_exit+0x65/0x90 [ext4_test]
>  kunit_try_run_case_cleanup+0xbc/0x100 [kunit]
>  kunit_generic_run_threadfn_adapter+0x89/0x100 [kunit]
>  kthread+0x408/0x540
>  ret_from_fork+0xa76/0xdf0
>  ret_from_fork_asm+0x1a/0x30
>
> The above issue was caused because the super_block cleanup process
> was not properly performed.
> Therefore, deactivate_super() is called in extents_kunit_exit() to
> cleanup the super_block.
>
> 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, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/ext4/extents-test.c b/fs/ext4/extents-test.c
> index 5a5016ea1ecc..70d84c0a18e2 100644
> --- a/fs/ext4/extents-test.c
> +++ b/fs/ext4/extents-test.c
> @@ -144,7 +144,7 @@ static void extents_kunit_exit(struct kunit *test)
>  {
>  	struct ext4_sb_info *sbi = k_ctx.k_ei->vfs_inode.i_sb->s_fs_info;
>  
> -	kfree(sbi);
> +	deactivate_super(sbi->s_sb);

This doesn't look correct. We don't have sbi->s_sb->s_op->put_super() registered, so
kfree(sbi) never happens. Maybe it will be good to check with kmemleak
too, that this could cause a memory leak.

I think we can do:

  ext4_es_unregister_shrinker(sbi); // already taken care in [1]
  deactivate_super(sbi->s_sb)
  kfree(sbi);

[1]: https://lore.kernel.org/linux-ext4/5bb9041471dab8ce870c191c19cbe4df57473be8.1772381213.git.ritesh.list@gmail.com/

-ritesh