From 2bcd3800f2da1be13b972858f63c66d035b1ec6d Mon Sep 17 00:00:00 2001 From: "Matthew Wilcox (Oracle)" Date: Thu, 13 Nov 2025 00:09:15 +0000 Subject: slab: Reimplement page_slab() In order to separate slabs from folios, we need to convert from any page in a slab to the slab directly without going through a page to folio conversion first. Up to this point, page_slab() has followed the example of other memdesc converters (page_folio(), page_ptdesc() etc) and just cast the pointer to the requested type, regardless of whether the pointer is actually a pointer to the correct type or not. That changes with this commit; we check that the page actually belongs to a slab and return NULL if it does not. Other memdesc converters will adopt this convention in future. kfence was the only user of page_slab(), so adjust it to the new way of working. It will need to be touched again when we separate slab from page. Signed-off-by: Matthew Wilcox (Oracle) Cc: Alexander Potapenko Cc: Marco Elver Cc: kasan-dev@googlegroups.com Link: https://patch.msgid.link/20251113000932.1589073-2-willy@infradead.org Acked-by: David Hildenbrand (Red Hat) Tested-by: Marco Elver Reviewed-by: Harry Yoo Signed-off-by: Vlastimil Babka --- mm/kfence/core.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) (limited to 'mm/kfence') diff --git a/mm/kfence/core.c b/mm/kfence/core.c index 727c20c94ac5..e62b5516bf48 100644 --- a/mm/kfence/core.c +++ b/mm/kfence/core.c @@ -612,14 +612,15 @@ static unsigned long kfence_init_pool(void) * enters __slab_free() slow-path. */ for (i = 0; i < KFENCE_POOL_SIZE / PAGE_SIZE; i++) { - struct slab *slab; + struct page *page; if (!i || (i % 2)) continue; - slab = page_slab(pfn_to_page(start_pfn + i)); - __folio_set_slab(slab_folio(slab)); + page = pfn_to_page(start_pfn + i); + __SetPageSlab(page); #ifdef CONFIG_MEMCG + struct slab *slab = page_slab(page); slab->obj_exts = (unsigned long)&kfence_metadata_init[i / 2 - 1].obj_exts | MEMCG_DATA_OBJEXTS; #endif @@ -665,16 +666,17 @@ static unsigned long kfence_init_pool(void) reset_slab: for (i = 0; i < KFENCE_POOL_SIZE / PAGE_SIZE; i++) { - struct slab *slab; + struct page *page; if (!i || (i % 2)) continue; - slab = page_slab(pfn_to_page(start_pfn + i)); + page = pfn_to_page(start_pfn + i); #ifdef CONFIG_MEMCG + struct slab *slab = page_slab(page); slab->obj_exts = 0; #endif - __folio_clear_slab(slab_folio(slab)); + __ClearPageSlab(page); } return addr; -- cgit v1.2.3