The patch titled
Subject: mm/migrate: remove slab checks in isolate_movable_page()
has been added to the -mm mm-unstable branch. Its filename is
mm-migrate-remove-slab-checks-in-isolate_movable_page.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-migrate-remove-slab-checks-in-isolate_movable_page.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx>
Subject: mm/migrate: remove slab checks in isolate_movable_page()
Date: Tue, 10 Dec 2024 21:48:07 +0900
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@xxxxxxxxx
Signed-off-by: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: Roman Gushchin <roman.gushchin@xxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/migrate.c | 8 --------
mm/slub.c | 4 ----
2 files changed, 12 deletions(-)
--- a/mm/migrate.c~mm-migrate-remove-slab-checks-in-isolate_movable_page
+++ a/mm/migrate.c
@@ -68,10 +68,6 @@ bool isolate_movable_page(struct page *p
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 *p
*/
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
--- a/mm/slub.c~mm-migrate-remove-slab-checks-in-isolate_movable_page
+++ a/mm/slub.c
@@ -2414,8 +2414,6 @@ static inline struct slab *alloc_slab_pa
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);
@@ -2636,8 +2634,6 @@ static void __free_slab(struct kmem_cach
__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);
_
Patches currently in -mm which might be from 42.hyeyoo@xxxxxxxxx are
mm-migrate-remove-slab-checks-in-isolate_movable_page.patch
