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

[Hao Li <hao.li@linux.dev>]

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@kernel.org>
> ---
>  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.

>  
>  		if (full) {
>  			stat(s, BARN_GET);
> @@ -7333,8 +7327,7 @@ static bool __kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags,
>   * Allocate @size objects from @s and places them into @p.  @size must be larger
>   * than 0.
>   *
> - * Interrupts must be enabled when calling this function and @flags must allow
> - * spinning.
> + * Interrupts must be enabled when calling this function.
>   *
>   * Unlike alloc_pages_bulk(), this function does not check for already allocated
>   * objects in @p, and thus the caller does not need to zero it.
> 
> -- 
> 2.54.0
>