kernel/linux.git/mm/huge_memory.c, branch v7.1-rc5

mm: thp: prevent memory cgroup release in folio_split_queue_lock{_irqsave}()

2026-04-18T07:10:46+00:00

In the near future, a folio will no longer pin its corresponding memory cgroup. To ensure safety, it will only be appropriate to hold the rcu read lock or acquire a reference to the memory cgroup returned by folio_memcg(), thereby preventing it from being released. In the current patch, the rcu read lock is employed to safeguard against the release of the memory cgroup in folio_split_queue_lock{_irqsave}(). Link: https://lore.kernel.org/ca2957c0df1126b2c71b40c738018fd5255525a6.1772711148.git.zhengqi.arch@bytedance.com Signed-off-by: Qi Zheng Reviewed-by: Harry Yoo Acked-by: Johannes Weiner Acked-by: Shakeel Butt Acked-by: David Hildenbrand (Red Hat) Acked-by: Muchun Song Cc: Allen Pais Cc: Axel Rasmussen Cc: Baoquan He Cc: Chengming Zhou Cc: Chen Ridong Cc: Hamza Mahfooz Cc: Hugh Dickins Cc: Imran Khan Cc: Kamalesh Babulal Cc: Lance Yang Cc: Liam Howlett Cc: Lorenzo Stoakes (Oracle) Cc: Michal Hocko Cc: Michal Koutný Cc: Mike Rapoport Cc: Muchun Song Cc: Nhat Pham Cc: Roman Gushchin Cc: Suren Baghdasaryan Cc: Usama Arif Cc: Vlastimil Babka Cc: Wei Xu Cc: Yosry Ahmed Cc: Yuanchu Xie Cc: Zi Yan Signed-off-by: Andrew Morton

mm: rename unlock_page_lruvec_irq and its variants

2026-04-18T07:10:44+00:00

It is inappropriate to use folio_lruvec_lock() variants in conjunction with unlock_page_lruvec() variants, as this involves the inconsistent operation of locking a folio while unlocking a page. To rectify this, the functions unlock_page_lruvec{_irq, _irqrestore} are renamed to lruvec_unlock{_irq,_irqrestore}. Link: https://lore.kernel.org/4e5e05271a250df4d1812e1832be65636a78c957.1772711148.git.zhengqi.arch@bytedance.com Signed-off-by: Muchun Song Signed-off-by: Qi Zheng Acked-by: Roman Gushchin Acked-by: Johannes Weiner Reviewed-by: Harry Yoo Reviewed-by: Chen Ridong Acked-by: David Hildenbrand (Red Hat) Acked-by: Shakeel Butt Cc: Allen Pais Cc: Axel Rasmussen Cc: Baoquan He Cc: Chengming Zhou Cc: Hamza Mahfooz Cc: Hugh Dickins Cc: Imran Khan Cc: Kamalesh Babulal Cc: Lance Yang Cc: Liam Howlett Cc: Lorenzo Stoakes (Oracle) Cc: Michal Hocko Cc: Michal Koutný Cc: Mike Rapoport Cc: Muchun Song Cc: Nhat Pham Cc: Suren Baghdasaryan Cc: Usama Arif Cc: Vlastimil Babka Cc: Wei Xu Cc: Yosry Ahmed Cc: Yuanchu Xie Cc: Zi Yan Signed-off-by: Andrew Morton

mm: fix deferred split queue races during migration

2026-04-05T20:53:47+00:00

migrate_folio_move() records the deferred split queue state from src and replays it on dst. Replaying it after remove_migration_ptes(src, dst, 0) makes dst visible before it is requeued, so a concurrent rmap-removal path can mark dst partially mapped and trip the WARN in deferred_split_folio(). Move the requeue before remove_migration_ptes() so dst is back on the deferred split queue before it becomes visible again. Because migration still holds dst locked at that point, teach deferred_split_scan() to requeue a folio when folio_trylock() fails. Otherwise a fully mapped underused folio can be dequeued by the shrinker and silently lost from split_queue. [ziy@nvidia.com: move the comment] Link: https://lkml.kernel.org/r/FB71A764-0F10-4E5A-B4A0-BA4C7F138408@nvidia.com Link: https://syzkaller.appspot.com/bug?extid=a7067a757858ac8eb085 Link: https://lkml.kernel.org/r/20260401131032.13011-1-lance.yang@linux.dev Fixes: 8a8ca142a488 ("mm: migrate: requeue destination folio on deferred split queue") Signed-off-by: Lance Yang Signed-off-by: Zi Yan Reported-by: syzbot+a7067a757858ac8eb085@syzkaller.appspotmail.com Closes: https://lore.kernel.org/linux-mm/69ccb65b.050a0220.183828.003a.GAE@google.com/ Suggested-by: David Hildenbrand (Arm) Acked-by: David Hildenbrand (Arm) Acked-by: Zi Yan Cc: Alistair Popple Cc: Baolin Wang Cc: Barry Song Cc: Byungchul Park Cc: David Hildenbrand Cc: Deepanshu Kartikey Cc: Dev Jain Cc: Gregory Price Cc: "Huang, Ying" Cc: Joshua Hahn Cc: Lance Yang Cc: Liam Howlett Cc: Lorenzo Stoakes (Oracle) Cc: Matthew Brost Cc: Nico Pache Cc: Rakie Kim Cc: Ryan Roberts Cc: Wei Yang Cc: Ying Huang Cc: Usama Arif Cc: Signed-off-by: Andrew Morton

mm/huge_memory: add and use has_deposited_pgtable()

2026-04-05T20:53:47+00:00

Rather than thread has_deposited through zap_huge_pmd(), make things clearer by adding has_deposited_pgtable() with comments describing why in each case. [ljs@kernel.org: fix folio_put()-before-recheck issue, per Sashiko] Link: https://lkml.kernel.org/r/0a917f80-902f-49b0-a75f-1bbaf23d7f94@lucifer.local Link: https://lkml.kernel.org/r/f9db59ca90937e39913d50ecb4f662e2bad17bbb.1774029655.git.ljs@kernel.org Signed-off-by: Lorenzo Stoakes (Oracle) Reviewed-by: Suren Baghdasaryan Cc: Baolin Wang Cc: Barry Song Cc: David Hildenbrand Cc: Dev Jain Cc: Lance Yang Cc: Liam Howlett Cc: Michal Hocko Cc: Mike Rapoport Cc: Nico Pache Cc: Qi Zheng Cc: Ryan Roberts Cc: Zi Yan Signed-off-by: Andrew Morton

mm/huge_memory: add and use normal_or_softleaf_folio_pmd()

2026-04-05T20:53:46+00:00

Now we have pmd_to_softleaf_folio() available to us which also raises a CONFIG_DEBUG_VM warning if unexpectedly an invalid softleaf entry, we can now abstract folio handling altogether. vm_normal_folio() deals with the huge zero page (which is present), as well as PFN map/mixed map mappings in both cases returning NULL. Otherwise, we try to obtain the softleaf folio. This makes the logic far easier to comprehend and has it use the standard vm_normal_folio_pmd() path for decoding of present entries. Finally, we have to update the flushing logic to only do so if a folio is established. This patch also makes the 'is_present' value more accurate - because PFN map, mixed map and zero huge pages are present, just not present and 'normal'. [ljs@kernel.org: avoid bisection hazard] Link: https://lkml.kernel.org/r/d0cc6161-77a4-42ba-a411-96c23c78df1b@lucifer.local Link: https://lkml.kernel.org/r/c2be872d64ef9573b80727d9ab5446cf002f17b5.1774029655.git.ljs@kernel.org Signed-off-by: Lorenzo Stoakes (Oracle) Reviewed-by: Suren Baghdasaryan Cc: Baolin Wang Cc: Barry Song Cc: David Hildenbrand Cc: Dev Jain Cc: Lance Yang Cc: Liam Howlett Cc: Michal Hocko Cc: Mike Rapoport Cc: Nico Pache Cc: Qi Zheng Cc: Ryan Roberts Cc: Zi Yan Signed-off-by: Andrew Morton

mm/huge_memory: separate out the folio part of zap_huge_pmd()

2026-04-05T20:53:46+00:00

Place the part of the logic that manipulates counters and possibly updates the accessed bit of the folio into its own function to make zap_huge_pmd() more readable. Also rename flush_needed to is_present as we only require a flush for present entries. Additionally add comments as to why we're doing what we're doing with respect to softleaf entries. This also lays the ground for further refactoring. Link: https://lkml.kernel.org/r/6c4db67952f5529da4db102a6149b9050b5dda4e.1774029655.git.ljs@kernel.org Signed-off-by: Lorenzo Stoakes (Oracle) Reviewed-by: Baolin Wang Reviewed-by: Suren Baghdasaryan Cc: Barry Song Cc: David Hildenbrand Cc: Dev Jain Cc: Lance Yang Cc: Liam Howlett Cc: Michal Hocko Cc: Mike Rapoport Cc: Nico Pache Cc: Qi Zheng Cc: Ryan Roberts Cc: Suren Baghdasaryan Cc: Zi Yan Signed-off-by: Andrew Morton

mm/huge_memory: use mm instead of tlb->mm

2026-04-05T20:53:46+00:00

Reduce the repetition, and lay the ground for further refactorings by keeping this variable separate. Link: https://lkml.kernel.org/r/98104cde87e4b2aabeb16f236b8731591594457f.1774029655.git.ljs@kernel.org Signed-off-by: Lorenzo Stoakes (Oracle) Reviewed-by: Baolin Wang Reviewed-by: Suren Baghdasaryan Cc: Barry Song Cc: David Hildenbrand Cc: Dev Jain Cc: Lance Yang Cc: Liam Howlett Cc: Michal Hocko Cc: Mike Rapoport Cc: Nico Pache Cc: Qi Zheng Cc: Ryan Roberts Cc: Zi Yan Signed-off-by: Andrew Morton

mm/huge_memory: remove unnecessary sanity checks

2026-04-05T20:53:46+00:00

These checks have been in place since 2014, I think we can safely assume that we are in a place where we don't need these as runtime checks. In addition there are 4 other invocations of folio_remove_rmap_pmd(), none of which make this assertion. If we need to add this assertion, it should be in folio_remove_rmap_pmd(), and as a VM_WARN_ON_ONCE(), however these seem superfluous so just remove them. Link: https://lkml.kernel.org/r/0c4c5ab247c90f80cf44718e8124b217d6a22544.1774029655.git.ljs@kernel.org Signed-off-by: Lorenzo Stoakes (Oracle) Reviewed-by: Suren Baghdasaryan Cc: Baolin Wang Cc: Barry Song Cc: David Hildenbrand Cc: Dev Jain Cc: Lance Yang Cc: Liam Howlett Cc: Michal Hocko Cc: Mike Rapoport Cc: Nico Pache Cc: Qi Zheng Cc: Ryan Roberts Cc: Zi Yan Signed-off-by: Andrew Morton

mm/huge_memory: deduplicate zap deposited table call

2026-04-05T20:53:46+00:00

Rather than having separate logic for each case determining whether to zap the deposited table, simply track this via a boolean. We default this to whether the architecture requires it, and update it as required elsewhere. Link: https://lkml.kernel.org/r/71f576a1fbcd27a86322d12caa937bcdacf75407.1774029655.git.ljs@kernel.org Signed-off-by: Lorenzo Stoakes (Oracle) Reviewed-by: Baolin Wang Reviewed-by: Suren Baghdasaryan Cc: Barry Song Cc: David Hildenbrand Cc: Dev Jain Cc: Lance Yang Cc: Liam Howlett Cc: Michal Hocko Cc: Mike Rapoport Cc: Nico Pache Cc: Qi Zheng Cc: Ryan Roberts Cc: Zi Yan Signed-off-by: Andrew Morton

mm/huge_memory: remove unnecessary VM_BUG_ON_PAGE()

2026-04-05T20:53:46+00:00

This has been around since the beginnings of the THP implementation. I think we can safely assume that, if we have a THP folio, it will have a head page. Link: https://lkml.kernel.org/r/f3fa8eb4634ccb2e78209f570cc1a769a02ce93e.1774029655.git.ljs@kernel.org Signed-off-by: Lorenzo Stoakes (Oracle) Reviewed-by: Baolin Wang Reviewed-by: Suren Baghdasaryan Cc: Barry Song Cc: David Hildenbrand Cc: Dev Jain Cc: Lance Yang Cc: Liam Howlett Cc: Michal Hocko Cc: Mike Rapoport Cc: Nico Pache Cc: Qi Zheng Cc: Ryan Roberts Cc: Zi Yan Signed-off-by: Andrew Morton