linux-kernel - Re: [PATCH] xfs: use kmem_cache_free() for kmem

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Message-ID: <3928ef69-eaac-241c-eb32-d2dd2eab9384@suse.cz>
Date:   Wed, 13 Oct 2021 09:38:31 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     "Darrick J. Wong" <djwong@...nel.org>
Cc:     David Rientjes <rientjes@...gle.com>,
        Rustam Kovhaev <rkovhaev@...il.com>,
        Dave Chinner <david@...morbit.com>, linux-xfs@...r.kernel.org,
        cl@...ux.com, penberg@...nel.org, iamjoonsoo.kim@....com,
        akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, gregkh@...uxfoundation.org,
        Al Viro <viro@...iv.linux.org.uk>, dvyukov@...gle.com
Subject: Re: [PATCH] xfs: use kmem_cache_free() for kmem_cache objects

On 10/13/21 01:22, Darrick J. Wong wrote:
> On Tue, Oct 12, 2021 at 11:32:25PM +0200, Vlastimil Babka wrote:
>> 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:
>> >>
>> >> 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?
> 
> It's probably better to fix slob to be able to tell that a kmem_free'd
> object actually belongs to a cache and should get freed that way, just
> like its larger sl[ua]b cousins.

Agreed. Rustam, do you still plan to do that?

> However, even if that does come to pass, anybody /else/ who wants to
> start(?) using XFS on a SLOB system will need this patch to fix the
> minor papercut.  Now that I've checked the rest of the codebase, I don't
> find it reasonable to make XFS mutually exclusive with SLOB over two
> instances of slab cache misuse.  Hence the RVB. :)

Ok. I was just wondering because Dave's first reply was that actually you'll
need to expand the use of kfree() instead of kmem_cache_free().