From 8c6e2d122b71b8cca7b215bca1cd586a1c09999a Mon Sep 17 00:00:00 2001 From: Hyeonggon Yoo <42.hyeyoo@gmail.com> Date: Tue, 10 Dec 2024 21:48:07 +0900 Subject: [PATCH] mm/migrate: remove slab checks in isolate_movable_page() Commit 8b8817630ae8 ("mm/migrate: make isolate_movable_page() skip slab pages") introduced slab checks to prevent mis-identification of slab pages as movable kernel pages. However, after Matthew's frozen folio series, these slab checks became unnecessary as the migration logic fails to increase the reference count for frozen slab folios. Remove these redundant slab checks and associated memory barriers. Link: https://lkml.kernel.org/r/20241210124807.8584-1-42.hyeyoo@gmail.com Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> Acked-by: David Hildenbrand Reviewed-by: Vlastimil Babka Acked-by: David Rientjes Cc: Christoph Lameter Cc: Joonsoo Kim Cc: Matthew Wilcox Cc: Pekka Enberg Cc: Roman Gushchin Signed-off-by: Andrew Morton --- mm/migrate.c | 8 -------- mm/slub.c | 4 ---- 2 files changed, 12 deletions(-) diff --git a/mm/migrate.c b/mm/migrate.c index e9e00d1d1d19..32cc8e0b1cce 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -68,10 +68,6 @@ bool isolate_movable_page(struct page *page, isolate_mode_t mode) if (!folio) goto out; - if (unlikely(folio_test_slab(folio))) - goto out_putfolio; - /* Pairs with smp_wmb() in slab freeing, e.g. SLUB's __free_slab() */ - smp_rmb(); /* * Check movable flag before taking the page lock because * we use non-atomic bitops on newly allocated page flags so @@ -79,10 +75,6 @@ bool isolate_movable_page(struct page *page, isolate_mode_t mode) */ if (unlikely(!__folio_test_movable(folio))) goto out_putfolio; - /* Pairs with smp_wmb() in slab allocation, e.g. SLUB's alloc_slab_page() */ - smp_rmb(); - if (unlikely(folio_test_slab(folio))) - goto out_putfolio; /* * As movable pages are not isolated from LRU lists, concurrent diff --git a/mm/slub.c b/mm/slub.c index a8e9b5106f4c..996691c137eb 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -2429,8 +2429,6 @@ static inline struct slab *alloc_slab_page(gfp_t flags, int node, slab = folio_slab(folio); __folio_set_slab(folio); - /* Make the flag visible before any changes to folio->mapping */ - smp_wmb(); if (folio_is_pfmemalloc(folio)) slab_set_pfmemalloc(slab); @@ -2651,8 +2649,6 @@ static void __free_slab(struct kmem_cache *s, struct slab *slab) __slab_clear_pfmemalloc(slab); folio->mapping = NULL; - /* Make the mapping reset visible before clearing the flag */ - smp_wmb(); __folio_clear_slab(folio); mm_account_reclaimed_pages(pages); unaccount_slab(slab, order, s); -- 2.50.1