Re: [PATCH v3 10/17] slab: Remove folio references from build_detached_freelist()

[Vlastimil Babka <vbabka@suse.cz>]

On 10/24/25 22:44, Matthew Wilcox (Oracle) wrote:
> As with memcg_slab_post_charge(), we save a call to compound_head() for
> large kmallocs.  This has a slight change of behaviour in that non-slab,
> non-kmalloc pointers will now cause a NULL pointer dereference rather
> than a warning.  We could add that back if really needed.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Ditto

> ---
>  mm/slub.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/slub.c b/mm/slub.c
> index 4e282e7782bb..e72016ff0236 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -7244,23 +7244,23 @@ int build_detached_freelist(struct kmem_cache *s, size_t size,
>  {
>  	int lookahead = 3;
>  	void *object;
> -	struct folio *folio;
> +	struct page *page;
>  	size_t same;
>  
>  	object = p[--size];
> -	folio = virt_to_folio(object);
> +	page = virt_to_page(object);
>  	if (!s) {
>  		/* Handle kalloc'ed objects */
> -		if (unlikely(!folio_test_slab(folio))) {
> -			free_large_kmalloc(&folio->page, object);
> +		if (unlikely(PageLargeKmalloc(page))) {
> +			free_large_kmalloc(page, object);
>  			df->slab = NULL;
>  			return size;
>  		}
>  		/* Derive kmem_cache from object */
> -		df->slab = folio_slab(folio);
> +		df->slab = page_slab(page);
>  		df->s = df->slab->slab_cache;
>  	} else {
> -		df->slab = folio_slab(folio);
> +		df->slab = page_slab(page);
>  		df->s = cache_from_obj(s, object); /* Support for memcg */
>  	}
>