Re: [PATCH v2 11/16] mm/slab: allow kmem_cache_alloc_bulk() with any gfp flags

[Vlastimil Babka (SUSE)]

On 6/12/26 05:21, Hao Li wrote:
> On Wed, Jun 10, 2026 at 05:40:13PM +0200, Vlastimil Babka (SUSE) wrote:
>> The last user of gfpflags_allow_spinning() in slab is
>> alloc_from_pcs_bulk(), which is only called from
>> kmem_cache_alloc_bulk().
>> 
>> It turns out that gfpflags_allow_spinning() is not necessary, because
>> kmem_cache_alloc_bulk() is only expected to be called from context that
>> does allow spinning, so simply replace it with 'true'.
>> 
>> With that, we can remove the "@flags must allow spinning" part of the
>> kernel doc, as there is no more connection to the gfp flags in the slab
>> implementation.
>> 
>> Also remove a comment in alloc_slab_obj_exts() because there should be
>> no more false positives possible due to gfp_allowed_mask during early
>> boot.
>> 
>> Signed-off-by: Vlastimil Babka (SUSE) <vbabka@xxxxxxxxxx>
>> ---
>>  mm/slub.c | 11 ++---------
>>  1 file changed, 2 insertions(+), 9 deletions(-)
>> 
>> diff --git a/mm/slub.c b/mm/slub.c
>> index 0b9974bfcb24..ef457e07db83 100644
>> --- a/mm/slub.c
>> +++ b/mm/slub.c
>> @@ -2171,12 +2171,6 @@ int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,
>>  
>>  	sz = obj_exts_alloc_size(s, slab, gfp);
>>  
>> -	/*
>> -	 * Note that allow_spin may be false during early boot and its
>> -	 * restricted GFP_BOOT_MASK. Due to kmalloc_nolock() only supporting
>> -	 * architectures with cmpxchg16b, early obj_exts will be missing for
>> -	 * very early allocations on those.
>> -	 */
>>  	if (unlikely(!allow_spin))
>>  		vec = kmalloc_nolock(sz, __GFP_ZERO | __GFP_NO_OBJ_EXT,
>>  				     slab_nid(slab));
>> @@ -4867,7 +4861,7 @@ unsigned int alloc_from_pcs_bulk(struct kmem_cache *s, gfp_t gfp, size_t size,
>>  		}
>>  
>>  		full = barn_replace_empty_sheaf(barn, pcs->main,
>> -						gfpflags_allow_spinning(gfp));
>> +						/* allow_spin = */ true);
> 
> we can remove the `gfp` arg as this function no longer use it.

True, done!