Commit 8c6e2d12 authored by Harry Yoo's avatar Harry Yoo Committed by Andrew Morton
Browse files

mm/migrate: remove slab checks in isolate_movable_page() 

Commit 8b881763 ("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: default avatarHyeonggon Yoo <42.hyeyoo@gmail.com>
Acked-by: default avatarDavid Hildenbrand <david@redhat.com>
Reviewed-by: default avatarVlastimil Babka <vbabka@suse.cz>
Acked-by: default avatarDavid Rientjes <rientjes@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 15e01f39

mm/migrate.c

+0 −8
Original line number Diff line number Diff line
@@ -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

mm/slub.c

+0 −4
Original line number Diff line number Diff line
@@ -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);