Re: [PATCH] slab: remove alloc_full_sheaf()

[vbabka@kernel.org]

On 3/12/26 04:31, Qing Wang wrote:
> On Thu, 12 Mar 2026 at 02:22, "Vlastimil Babka (SUSE)" <vbabka@kernel.org> wrote:
>> -	if (!full)
>> +	if (refill_sheaf(s, empty, gfp | __GFP_NOMEMALLOC | __GFP_NOWARN)) {
>> +		/*
>> +		 * we must be very low on memory so don't bother
>> +		 * with the barn
>> +		 */
>> +		sheaf_flush_unused(s, empty);
>> +		free_empty_sheaf(s, empty);
>> +
>>  		return NULL;
>> +	}
>> +
>> +	full = empty;
>> +	empty = NULL;
> 
> 'empty = NULL' is meaningless since 'empty' is not used after here.

Exactly, it's only for humans reading the code to make it explicit. And if
someone tries to make a change that will start using empty, it will oops
immediately instead of something more subtle.

>>  
>>  	if (!local_trylock(&s->cpu_sheaves->lock))
>>  		goto barn_put;
>>  	pcs = this_cpu_ptr(s->cpu_sheaves);
>>  
>>  	/*
>> -	 * If we are returning empty sheaf, we either got it from the
>> -	 * barn or had to allocate one. If we are returning a full
>> -	 * sheaf, it's due to racing or being migrated to a different
>> -	 * cpu. Breaching the barn's sheaf limits should be thus rare
>> -	 * enough so just ignore them to simplify the recovery.
>> +	 * If we put any empty or full sheaf to the barn below, it's due to
>> +	 * racing or being migrated to a different cpu. Breaching the barn's
>> +	 * sheaf limits should be thus rare enough so just ignore them to
>> +	 * simplify the recovery.
>>  	 */
>>  
>>  	if (pcs->main->size == 0) {
> 
> LGTM.
> 
> Reviewed-by: Qing Wang <wangqing7171@gmail.com>

Thanks!

> --
> Cheers,
> Qing