linux-kernel - Re: [PATCH 4/4] slab: use struct freelist_counters as parameters in relevant functions

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Message-ID: <8633ea79-db53-4157-932b-30a814283c03@suse.cz>
Date: Thu, 13 Nov 2025 10:13:49 +0100
From: Vlastimil Babka <vbabka@...e.cz>
To: Harry Yoo <harry.yoo@...cle.com>
Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
 Christoph Lameter <cl@...two.org>, David Rientjes <rientjes@...gle.com>,
 Roman Gushchin <roman.gushchin@...ux.dev>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] slab: use struct freelist_counters as parameters in
 relevant functions

On 11/13/25 09:32, Harry Yoo wrote:
> On Fri, Nov 07, 2025 at 02:51:26PM +0100, Vlastimil Babka wrote:
>> In functions such as [__]slab_update_freelist() and
>> __slab_update_freelist_fast/slow() we pass old and new freelist and
>> counters as 4 separate parameters. The underlying
>> __update_freelist_fast() then constructs struct freelist_counters
>> variables for passing the full freelist+counter combinations to cmpxchg
>> double.
>> 
>> In most cases we actually start with struct freelist_counters variables,
>> but then pass the individual fields, only to construct new struct
>> freelist_counters variables. While it's all inlined and thus should be
>> efficient, we can simplify this code.
>> 
>> Thus replace the 4 parameters for individual fields with two
>> freelist_aba_t pointers wherever applicable. __update_freelist_fast()
> 
> nit: I guess you meant struct freelist_counters pointers, because
> freelist_aba_t is gone.

Yeah, stale text from before removing freelist_aba_t, will update, thanks.

>> can then pass them directly to try_cmpxchg_freelist().
>> 
>> The code is also more obvious as the pattern becomes unified such that
>> we set up "old" and "new" struct freelist_counters variables upfront as
>> we fully need them to be, and simply call [__]slab_update_freelist() on
>> them.  Previously some of the "new" values would be hidden as one of the
>> many parameters and thus make it harder to figure out what the code
>> does.
>> 
>> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
>> ---
> 
> Nice!
> 
> Looks good to me,
> Reviewed-by: Harry Yoo <harry.yoo@...cle.com>

Thanks a lot for all your reviews!