The patch titled Subject: mm: convert partially_mapped set/clear operations to be atomic has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-convert-partially_mapped-set-clear-operations-to-be-atomic.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: Usama Arif usamaarif642@gmail.com Subject: mm: convert partially_mapped set/clear operations to be atomic Date: Thu, 12 Dec 2024 18:33:51 +0000

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: 8422acdc97ed ("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 ---

include/linux/page-flags.h | 12 ++---------- mm/huge_memory.c | 8 ++++---- 2 files changed, 6 insertions(+), 14 deletions(-)

--- a/include/linux/page-flags.h~mm-convert-partially_mapped-set-clear-operations-to-be-atomic +++ a/include/linux/page-flags.h @@ -862,18 +862,10 @@ static inline void ClearPageCompound(str 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)) --- a/mm/huge_memory.c~mm-convert-partially_mapped-set-clear-operations-to-be-atomic +++ a/mm/huge_memory.c @@ -3577,7 +3577,7 @@ int split_huge_page_to_list_to_order(str !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(stru 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 * 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 } 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); } _

Patches currently in -mm which might be from usamaarif642@gmail.com are

mm-convert-partially_mapped-set-clear-operations-to-be-atomic.patch