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mm: convert partially_mapped set/clear operations to be atomic

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Other page flags in the 2nd page, like PG_hwpoison and PG_anon_exclusive
can get modified concurrently.  Changes to other page flags might be lost
if they are happening at the same time as non-atomic partially_mapped
operations.  Hence, make partially_mapped operations atomic.

Link: https://lkml.kernel.org/r/20241212183351.1345389-1-usamaarif642@gmail.com
Fixes: 8422acdc97 ("mm: introduce a pageflag for partially mapped folios")
Reported-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/all/e53b04ad-1827-43a2-a1ab-864c7efecf6e@redhat.com/
Signed-off-by: Usama Arif <usamaarif642@gmail.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Barry Song <baohua@kernel.org>
Cc: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Nico Pache <npache@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Yu Zhao <yuzhao@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Usama Arif 2024-12-12 18:33:51 +00:00 committed by Andrew Morton
parent 6309b8ce98
commit 42b2eb6983
2 changed files with 6 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
include/linux/page-flags.h
View File

@ -862,18 +862,10 @@ static inline void ClearPageCompound(struct page *page)
ClearPageHead(page);
}
FOLIO_FLAG(large_rmappable, FOLIO_SECOND_PAGE)
FOLIO_TEST_FLAG(partially_mapped, FOLIO_SECOND_PAGE)
/*
* PG_partially_mapped is protected by deferred_split split_queue_lock,
* so its safe to use non-atomic set/clear.
*/
__FOLIO_SET_FLAG(partially_mapped, FOLIO_SECOND_PAGE)
__FOLIO_CLEAR_FLAG(partially_mapped, FOLIO_SECOND_PAGE)
FOLIO_FLAG(partially_mapped, FOLIO_SECOND_PAGE)
#else
FOLIO_FLAG_FALSE(large_rmappable)
FOLIO_TEST_FLAG_FALSE(partially_mapped)
__FOLIO_SET_FLAG_NOOP(partially_mapped)
__FOLIO_CLEAR_FLAG_NOOP(partially_mapped)
FOLIO_FLAG_FALSE(partially_mapped)
#endif
#define PG_head_mask ((1UL << PG_head))

8
mm/huge_memory.c
View File

@ -3577,7 +3577,7 @@ int split_huge_page_to_list_to_order(struct page *page, struct list_head *list,
!list_empty(&folio->_deferred_list)) {
ds_queue->split_queue_len--;
if (folio_test_partially_mapped(folio)) {
__folio_clear_partially_mapped(folio);
folio_clear_partially_mapped(folio);
mod_mthp_stat(folio_order(folio),
MTHP_STAT_NR_ANON_PARTIALLY_MAPPED, -1);
}
@ -3689,7 +3689,7 @@ bool __folio_unqueue_deferred_split(struct folio *folio)
if (!list_empty(&folio->_deferred_list)) {
ds_queue->split_queue_len--;
if (folio_test_partially_mapped(folio)) {
__folio_clear_partially_mapped(folio);
folio_clear_partially_mapped(folio);
mod_mthp_stat(folio_order(folio),
MTHP_STAT_NR_ANON_PARTIALLY_MAPPED, -1);
}
@ -3733,7 +3733,7 @@ void deferred_split_folio(struct folio *folio, bool partially_mapped)
spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
if (partially_mapped) {
if (!folio_test_partially_mapped(folio)) {
__folio_set_partially_mapped(folio);
folio_set_partially_mapped(folio);
if (folio_test_pmd_mappable(folio))
count_vm_event(THP_DEFERRED_SPLIT_PAGE);
count_mthp_stat(folio_order(folio), MTHP_STAT_SPLIT_DEFERRED);
@ -3826,7 +3826,7 @@ static unsigned long deferred_split_scan(struct shrinker *shrink,
} else {
/* We lost race with folio_put() */
if (folio_test_partially_mapped(folio)) {
__folio_clear_partially_mapped(folio);
folio_clear_partially_mapped(folio);
mod_mthp_stat(folio_order(folio),
MTHP_STAT_NR_ANON_PARTIALLY_MAPPED, -1);
}