kernel/linux.git/mm/compaction.c, branch v7.2-rc1

mm/compaction: respect cpusets when checking retry suitability

2026-06-09T01:21:25+00:00

should_compact_retry() handles COMPACT_SKIPPED by asking compaction_zonelist_suitable() whether reclaim can make a later compaction attempt worthwhile. That answer is used for the current allocation, so it should follow the same zone eligibility rules as the allocation itself. When cpusets are enabled, allocator slowpath decisions are marked with ALLOC_CPUSET. The allocation path, direct compaction and reclaim retry all skip zones rejected by __cpuset_zone_allowed(). compaction_zonelist_suitable() does not apply that filter. It only walks ac->zonelist/ac->nodemask, so it can return true because a zone that is not usable for the current allocation would pass __compaction_suitable(). That does not let the allocation use the disallowed zone. Later allocation and direct compaction paths still apply cpuset filtering. However, it can make should_compact_retry() retry based on memory that this allocation cannot use. Pass gfp_mask down and apply the same ALLOC_CPUSET check in compaction_zonelist_suitable(). This keeps the retry decision aligned with the zones that the allocation is allowed to use. A temporary debugfs probe was also used to call the old and new compaction_zonelist_suitable() predicates in the same two-node NUMA guest. The task was restricted to mems=0 while ac->nodemask covered nodes 0-1. After putting pressure on node0, node0 failed __compaction_suitable() for order-10 and node1 passed it, but node1 was rejected by __cpuset_zone_allowed(). In that state the old predicate returned true and the patched predicate returned false. Link: https://lore.kernel.org/tencent_F59F2BA2CC5779308E10DF54593C736D3E0A@qq.com Fixes: 435b3894e742 ("mm:page_alloc: fix the NULL ac->nodemask in __alloc_pages_slowpath()") Signed-off-by: fujunjie Reviewed-by: Vlastimil Babka (SUSE) Cc: Brendan Jackman Cc: Johannes Weiner Cc: Michal Hocko Cc: Suren Baghdasaryan Cc: Zi Yan Signed-off-by: Andrew Morton

mm: remove mentions of PageWriteback

2026-06-04T21:45:07+00:00

Update two comments to refer to writeback in general instead of the specific flag. Convert the large comment in memory.c to be entirely folio-based. Link: https://lore.kernel.org/20260526195650.353196-1-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) Signed-off-by: Andrew Morton

mm/page_alloc: don't overload migratetype in find_suitable_fallback()

2026-06-02T22:22:19+00:00

This function currently returns a signed integer that encodes status in-band, as negative numbers, along with a migratetype. Switch to a more explicit/verbose style that encodes the status and migratetype separately. In the spirit of making things more explicit, also create an enum to avoid using magic integer literals with special meanings. This enables documenting the values at their definition instead of in one of the callers. Link: https://lore.kernel.org/20260513-page_alloc-unmapped-prep-v1-2-dacdf5402be8@google.com Signed-off-by: Brendan Jackman Reviewed-by: Vlastimil Babka (SUSE) Cc: Axel Rasmussen Cc: Barry Song Cc: David Hildenbrand Cc: Johannes Weiner Cc: Kairui Song Cc: Len Brown Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Mike Rapoport (Microsoft) Cc: "Rafael J. Wysocki" Cc: Shakeel Butt Cc: Suren Baghdasaryan Cc: Wei Xu Cc: Yuanchu Xie Cc: Zi Yan Signed-off-by: Andrew Morton

mm: memcontrol: prepare for reparenting LRU pages for lruvec lock

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

The following diagram illustrates how to ensure the safety of the folio lruvec lock when LRU folios undergo reparenting. In the folio_lruvec_lock(folio) function: rcu_read_lock(); retry: lruvec = folio_lruvec(folio); /* There is a possibility of folio reparenting at this point. */ spin_lock(&lruvec->lru_lock); if (unlikely(lruvec_memcg(lruvec) != folio_memcg(folio))) { /* * The wrong lruvec lock was acquired, and a retry is required. * This is because the folio resides on the parent memcg lruvec * list. */ spin_unlock(&lruvec->lru_lock); goto retry; } /* Reaching here indicates that folio_memcg() is stable. */ In the memcg_reparent_objcgs(memcg) function: spin_lock(&lruvec->lru_lock); spin_lock(&lruvec_parent->lru_lock); /* Transfer folios from the lruvec list to the parent's. */ spin_unlock(&lruvec_parent->lru_lock); spin_unlock(&lruvec->lru_lock); After acquiring the lruvec lock, it is necessary to verify whether the folio has been reparented. If reparenting has occurred, the new lruvec lock must be reacquired. During the LRU folio reparenting process, the lruvec lock will also be acquired (this will be implemented in a subsequent patch). Therefore, folio_memcg() remains unchanged while the lruvec lock is held. Given that lruvec_memcg(lruvec) is always equal to folio_memcg(folio) after the lruvec lock is acquired, the lruvec_memcg_debug() check is redundant. Hence, it is removed. This patch serves as a preparation for the reparenting of LRU folios. Link: https://lore.kernel.org/23f22cbb1419f277a3483018b32158ae2b86c666.1772711148.git.zhengqi.arch@bytedance.com Signed-off-by: Muchun Song Signed-off-by: Qi Zheng Acked-by: Johannes Weiner Acked-by: Shakeel Butt Cc: Allen Pais Cc: Axel Rasmussen Cc: Baoquan He Cc: Chengming Zhou Cc: Chen Ridong Cc: David Hildenbrand Cc: Hamza Mahfooz Cc: Harry Yoo 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/compaction: fix low_pfn advance on isolating hugetlb

2025-09-28T18:51:29+00:00

Commit 56ae0bb349b4 ("mm: compaction: convert to use a folio in isolate_migratepages_block()") converts api from page to folio. But the low_pfn advance for hugetlb page seems wrong when low_pfn doesn't point to head page. Originally, if page is a hugetlb tail page, compound_nr() return 1, which means low_pfn only advance one in next iteration. After the change, low_pfn would advance more than the hugetlb range, since folio_nr_pages() always return total number of the large page. This results in skipping some range to isolate and then to migrate. The worst case for alloc_contig is it does all the isolation and migration, but finally find some range is still not isolated. And then undo all the work and try a new range. Advance low_pfn to the end of hugetlb. Link: https://lkml.kernel.org/r/20250910092240.3981-1-richard.weiyang@gmail.com Fixes: 56ae0bb349b4 ("mm: compaction: convert to use a folio in isolate_migratepages_block()") Signed-off-by: Wei Yang Acked-by: Zi Yan Cc: "Vishal Moola (Oracle)" Cc: Kefeng Wang Cc: Oscar Salvador Cc: Brendan Jackman Cc: Johannes Weiner Cc: Michal Hocko Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Wei Yang Signed-off-by: Andrew Morton

mm: rename PG_isolated to PG_movable_ops_isolated

2025-07-13T23:38:30+00:00

Let's rename the flag to make it clearer where it applies (not folios ...). While at it, define the flag only with CONFIG_MIGRATION. Link: https://lkml.kernel.org/r/20250704102524.326966-22-david@redhat.com Signed-off-by: David Hildenbrand Reviewed-by: Zi Yan Reviewed-by: Lorenzo Stoakes Reviewed-by: Harry Yoo Cc: Alistair Popple Cc: Al Viro Cc: Arnd Bergmann Cc: Brendan Jackman Cc: Byungchul Park Cc: Chengming Zhou Cc: Christian Brauner Cc: Christophe Leroy Cc: Eugenio Pé rez Cc: Greg Kroah-Hartman Cc: Gregory Price Cc: "Huang, Ying" Cc: Jan Kara Cc: Jason Gunthorpe Cc: Jason Wang Cc: Jerrin Shaji George Cc: Johannes Weiner Cc: John Hubbard Cc: Jonathan Corbet Cc: Joshua Hahn Cc: Liam Howlett Cc: Madhavan Srinivasan Cc: Mathew Brost Cc: Matthew Wilcox (Oracle) Cc: Miaohe Lin Cc: Michael Ellerman Cc: "Michael S. Tsirkin" Cc: Michal Hocko Cc: Mike Rapoport Cc: Minchan Kim Cc: Naoya Horiguchi Cc: Nicholas Piggin Cc: Oscar Salvador Cc: Peter Xu Cc: Qi Zheng Cc: Rakie Kim Cc: Rik van Riel Cc: Sergey Senozhatsky Cc: Shakeel Butt Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Xuan Zhuo Cc: xu xin Signed-off-by: Andrew Morton

mm: convert "movable" flag in page->mapping to a page flag

2025-07-13T23:38:30+00:00

Instead, let's use a page flag. As the page flag can result in false-positives, glue it to the page types for which we support/implement movable_ops page migration. We are reusing PG_uptodate, that is for example used to track file system state and does not apply to movable_ops pages. So warning in case it is set in page_has_movable_ops() on other page types could result in false-positive warnings. Likely we could set the bit using a non-atomic update: in contrast to page->mapping, we could have others trying to update the flags concurrently when trying to lock the folio. In isolate_movable_ops_page(), we already take care of that by checking if the page has movable_ops before locking it. Let's start with the atomic variant, we could later switch to the non-atomic variant once we are sure other cases are similarly fine. Once we perform the switch, we'll have to introduce __SETPAGEFLAG_NOOP(). [david@redhat.com: add missing `:' in kerneldoc] Link: https://lkml.kernel.org/r/d96e2916-2c43-462c-b6a1-2375ef397d8b@redhat.com Link: https://lkml.kernel.org/r/20250704102524.326966-21-david@redhat.com Signed-off-by: David Hildenbrand Reviewed-by: Zi Yan Reviewed-by: Lorenzo Stoakes Cc: Alistair Popple Cc: Al Viro Cc: Arnd Bergmann Cc: Brendan Jackman Cc: Byungchul Park Cc: Chengming Zhou Cc: Christian Brauner Cc: Christophe Leroy Cc: Eugenio Pé rez Cc: Greg Kroah-Hartman Cc: Gregory Price Cc: Harry Yoo Cc: "Huang, Ying" Cc: Jan Kara Cc: Jason Gunthorpe Cc: Jason Wang Cc: Jerrin Shaji George Cc: Johannes Weiner Cc: John Hubbard Cc: Jonathan Corbet Cc: Joshua Hahn Cc: Liam Howlett Cc: Madhavan Srinivasan Cc: Mathew Brost Cc: Matthew Wilcox (Oracle) Cc: Miaohe Lin Cc: Michael Ellerman Cc: "Michael S. Tsirkin" Cc: Michal Hocko Cc: Mike Rapoport Cc: Minchan Kim Cc: Naoya Horiguchi Cc: Nicholas Piggin Cc: Oscar Salvador Cc: Peter Xu Cc: Qi Zheng Cc: Rakie Kim Cc: Rik van Riel Cc: Sergey Senozhatsky Cc: Shakeel Butt Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Xuan Zhuo Cc: xu xin Signed-off-by: Andrew Morton

mm: stop storing migration_ops in page->mapping

2025-07-13T23:38:29+00:00

... instead, look them up statically based on the page type. Maybe in the future we want a registration interface? At least for now, it can be easily handled using the two page types that actually support page migration. The remaining usage of page->mapping is to flag such pages as actually being movable (having movable_ops), which we will change next. Link: https://lkml.kernel.org/r/20250704102524.326966-20-david@redhat.com Signed-off-by: David Hildenbrand Reviewed-by: Zi Yan Reviewed-by: Lorenzo Stoakes Reviewed-by: Harry Yoo Cc: Alistair Popple Cc: Al Viro Cc: Arnd Bergmann Cc: Brendan Jackman Cc: Byungchul Park Cc: Chengming Zhou Cc: Christian Brauner Cc: Christophe Leroy Cc: Eugenio Pé rez Cc: Greg Kroah-Hartman Cc: Gregory Price Cc: "Huang, Ying" Cc: Jan Kara Cc: Jason Gunthorpe Cc: Jason Wang Cc: Jerrin Shaji George Cc: Johannes Weiner Cc: John Hubbard Cc: Jonathan Corbet Cc: Joshua Hahn Cc: Liam Howlett Cc: Madhavan Srinivasan Cc: Mathew Brost Cc: Matthew Wilcox (Oracle) Cc: Miaohe Lin Cc: Michael Ellerman Cc: "Michael S. Tsirkin" Cc: Michal Hocko Cc: Mike Rapoport Cc: Minchan Kim Cc: Naoya Horiguchi Cc: Nicholas Piggin Cc: Oscar Salvador Cc: Peter Xu Cc: Qi Zheng Cc: Rakie Kim Cc: Rik van Riel Cc: Sergey Senozhatsky Cc: Shakeel Butt Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Xuan Zhuo Cc: xu xin Signed-off-by: Andrew Morton

mm: rename __PageMovable() to page_has_movable_ops()

2025-07-13T23:38:29+00:00

Let's make it clearer that we are talking about movable_ops pages. While at it, convert a VM_BUG_ON to a VM_WARN_ON_ONCE_PAGE. Link: https://lkml.kernel.org/r/20250704102524.326966-17-david@redhat.com Signed-off-by: David Hildenbrand Reviewed-by: Zi Yan Reviewed-by: Lorenzo Stoakes Reviewed-by: Harry Yoo Cc: Alistair Popple Cc: Al Viro Cc: Arnd Bergmann Cc: Brendan Jackman Cc: Byungchul Park Cc: Chengming Zhou Cc: Christian Brauner Cc: Christophe Leroy Cc: Eugenio Pé rez Cc: Greg Kroah-Hartman Cc: Gregory Price Cc: "Huang, Ying" Cc: Jan Kara Cc: Jason Gunthorpe Cc: Jason Wang Cc: Jerrin Shaji George Cc: Johannes Weiner Cc: John Hubbard Cc: Jonathan Corbet Cc: Joshua Hahn Cc: Liam Howlett Cc: Madhavan Srinivasan Cc: Mathew Brost Cc: Matthew Wilcox (Oracle) Cc: Miaohe Lin Cc: Michael Ellerman Cc: "Michael S. Tsirkin" Cc: Michal Hocko Cc: Mike Rapoport Cc: Minchan Kim Cc: Naoya Horiguchi Cc: Nicholas Piggin Cc: Oscar Salvador Cc: Peter Xu Cc: Qi Zheng Cc: Rakie Kim Cc: Rik van Riel Cc: Sergey Senozhatsky Cc: Shakeel Butt Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Xuan Zhuo Cc: xu xin Signed-off-by: Andrew Morton