Re: [PATCH] xfs: use kmem_cache_free() for kmem_cache objects

Vlastimil Babka
2021-10-12T21:32:30Z

On 10/12/2021 10:43 PM, Darrick J. Wong wrote:
> On Tue, Oct 12, 2021 at 01:43:20PM -0700, Darrick J. Wong wrote:
>> On Sun, Oct 03, 2021 at 06:07:20PM -0700, David Rientjes wrote:
>>> On Thu, 30 Sep 2021, Rustam Kovhaev wrote:
>>>
>>>>>>> I think it's fair if something like XFS (not meant for tiny systems AFAIK?)
>>>>>>> excludes SLOB (meant for tiny systems). Clearly nobody tried to use these
>>>>>>> two together last 5 years anyway.
>>>>>>
>>>>>> +1 for adding Kconfig option, it seems like some things are not meant to
>>>>>> be together.
>>>>>
>>>>> But if we patch SLOB, we won't need it.
>>>>
>>>> OK, so we consider XFS on SLOB a supported configuration that might be
>>>> used and should be tested.
>>>> I'll look into maybe adding a config with CONFIG_SLOB and CONFIG_XFS_FS
>>>> to syzbot.
>>>>
>>>> It seems that we need to patch SLOB anyway, because any other code can
>>>> hit the very same issue.
>>>>
>>>
>>> It's probably best to introduce both (SLOB fix and Kconfig change for
>>> XFS), at least in the interim because the combo of XFS and SLOB could be
>>> broken in other ways. If syzbot doesn't complain with a patched kernel to
>>> allow SLOB to be used with XFS, then we could potentially allow them to be
>>> used together.
>>>
>>> (I'm not sure that this freeing issue is the *only* thing that is broken,
>>> nor that we have sufficient information to make that determination right
>>> now..)
>>
>> I audited the entire xfs (kernel) codebase and didn't find any other
>> usage errors. Thanks for the patch; I'll apply it to for-next.

Which patch, the one that started this thread and uses kmem_cache_free() instead
of kfree()? I thought we said it's not the best way?

> Also, the obligatory
>
> Reviewed-by: Darrick J. Wong <djwong@kernel.org>
>
> --D
>
>>
>> --D