kernel/git/stable/linux.git/mm/internal.h, branch master

mm/gup: factor out LRU cache draining for folio into lru_cache_drain_for_folio()

2026-08-25T01:43:00+00:00

KVM with guest_memfd wants to remove any folio references due to LRU caches, as it really must only allow to convert folios from shared to private when there are no unexpected folio references (e.g., from GUP references). So, to drive the refcount down, it needs a way to flush the LRU caches. Let's factor out what we have in lru_cache_drain_for_folio(). Document it, and also mention that concurrent folio (un)mapping might, in theory, miss detecting LRU cache references. Keep obtaining the expected refcount twice to minimize the possibility. For the current and future user that should work, and we don't really have a better alternative: we could detect if the mapcount changed, but it would still be racy and add more complexity with questionable benefit. Maybe there is a chance to avoid the draining entirely in the future, by avoiding extra references from the LRU cache: Hugh thinks there might be a way. But for the time being, this handling is unfortunately required. Make folio_may_be_lru_cached() accept a const pointer so lru_cache_drain_for_folio() can accept a const pointer as well. Link: https://lore.kernel.org/20260806-lru_cache_drain_for_folio-v1-1-c6287d295e99@kernel.org Signed-off-by: David Hildenbrand (Arm) Reviewed-by: Fuad Tabba Cc: Ackerley Tng Cc: Baoquan He Cc: Barry Song Cc: Chris Li Cc: Jason Gunthorpe Cc: John Hubbard Cc: Kairui Song Cc: Kemeng Shi Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Mike Rapoport Cc: Nhat Pham Cc: Peter Xu Cc: Sean Christopherson Cc: Suren Baghdasaryan Cc: Vlastimil Babka Signed-off-by: Andrew Morton

mm/vmscan: reduce lru_lock contention via vmstat-derived scan-balance cost

2026-08-25T01:42:56+00:00

The anon/file scan balance in get_scan_count() is driven by two scalars in struct lruvec, anon_cost and file_cost, accumulated by every reclaim producer under lruvec->lru_lock. The acquisition sites for cost work specifically are: - shrink_inactive_list() re-takes lru_lock at function exit purely to call lru_note_cost_unlock_irq() with (nr_pageout, nr_scanned - nr_reclaimed). One acquisition per inactive shrink. - shrink_active_list() does the same with (0, nr_rotated). One acquisition per active shrink. - workingset_refault() takes the lock via folio_lruvec_lock_irq() purely to record the refault cost. One acquisition per refault. - prepare_scan_control() takes lru_lock just to snapshot the two scalars into sc->{anon,file}_cost. - lru_note_cost_unlock_irq() itself walks parent_lruvec and re-acquires lru_lock on each ancestor to propagate the update, adding O(memcg-depth) acquisitions per producer call. This hurts because lru_lock is already a heavy contention point on memory-heavy workloads: every isolate_lru_folios(), move_folios_to_lru() and folio_add_lru() takes it. The cost work itself is trivial (two scalar bumps and one comparison), but it contends with and causes contention for actual LRU manipulation. The parent_lruvec() walk also multiplies cost-update overhead by memcg hierarchy depth. The balance formula for anon and file, respectively, is this: cost = nr_io * SWAP_CLUSTER_MAX + nr_rotated Instead of recording cost and running averaging logic directly when these events occur, snapshot running vmstat counters once per reclaim cycle and derive the balance from event deltas since the last run. Use PGROTATE_* from the preceding patch for the rotation input. WORKINGSET_RESTORE_* and NR_VMSCAN_WRITE provide the remaining event counters. Charge NR_VMSCAN_WRITE through lruvec stats so all inputs can be sampled per lruvec and aggregated through the memcg hierarchy. This is overall cheaper and has fewer lock acquisition sites. Moving accumulation and decay to the reclaim side also improves the cost model across reclaim gaps. With producer-side decay, events that happen while reclaim is idle still age each other before reclaim ever samples the costs. If a workload refaults a large anon set and then a smaller file set before reclaim runs again, the later file activity can age the earlier anon activity out of the cost model. The new scheme observes the whole between-reclaim delta and decays anon and file proportionally, so the scan-balance history better represents what happened since the last reclaim pass. A dedicated per-lruvec spinlock, cost_lock, serialises the delta extraction, the cost->count update and the halving loop against concurrent reclaimers in the same memcg+node. NR_VMSCAN_WRITE is accounted at writeout(), so reclaim_stat.nr_pageout is no longer needed and is removed. memcg-v1's memory.stat anon_cost/file_cost is now sourced from cost[].count instead of the removed lruvec anon_cost/file_cost fields. The reported values only refresh when prepare_scan_control() runs and are bounded at ~lrusize/4 by the halving loop; the scan-balance signal they express is unchanged. Under pure MGLRU the scan-balance signal itself is not consumed (both prepare_scan_control() and get_scan_count() are short-circuited on the MGLRU paths, and MGLRU's own type/tier selection comes from read_ctrl_pos() on lrugen->{avg_refaulted,avg_total,refaulted,evicted}, not from anon_cost/file_cost). NR_VMSCAN_WRITE naturally covers writeout from either reclaim implementation. The preceding patch also bumps PGROTATE_{ANON,FILE} from evict_folios(), so rotation-driven reclaim work is accounted consistently across both implementations. Link: https://lore.kernel.org/20260727162550.2032-4-usama.arif@linux.dev Signed-off-by: Usama Arif Acked-by: Shakeel Butt Acked-by: Johannes Weiner Acked-by: Vlastimil Babka (SUSE) Cc: Axel Rasmussen Cc: Baoquan He Cc: Chris Li Cc: David Hildenbrand Cc: David Rientjes Cc: Kairui Song Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Mike Rapoport Cc: Muchun Song Cc: Nhat Pham Cc: Roman Gushchin Cc: Suren Baghdasaryan Cc: Wei Xu Cc: Yuanchu Xie Signed-off-by: Andrew Morton

mm/rmap: use anon pgoff to track MAP_PRIVATE file-backed anon folios

2026-08-25T01:42:53+00:00

Currently anonymous folios belonging to CoW'd MAP_PRIVATE file-backed mappings are indexed by their page offset within the file in which they were originally mapped. This differs from anonymous folios belonging to pure anon mappings which are indexed by their anonymous page offset (the address at which they'd belong in the VMA when first faulted). This change fixes this inconsistency, always indexing anonymous folios by their anonymous page offset regardless of the VMA to which they belong. The foundations have been laid such that we need only switch this functionality on such by: * Using linear_anon_page_index() in __folio_set_anon() to assign the folio's index to the anonymous linear index rather than the file-backed one. * Otherwise using linear_anon_page_index() in all instances where anonymous folios are being referenced or manipulated. * Replacing vma_address() with vma_filebacked_address() or vma_anon_address() as appropriate. * Updating the merging logic to check that anonymous page offsets are aligned as well as filebacked ones for MAP_PRIVATE file-backed VMAs, introducing needs_adjacent_anon_pgoff() to figure out when this is required. * Updating linear_folio_page_index() to invoke linear_anon_page_index() if the folio is anonymous. * Updating vma_address_end() to use the VMA's anonymous page offset when pvmw->pgoff is anonymous. * Correcting folio_within_range() to use anonymous page offset for anonymous folios. This will have no impact on merging of anonymous VMAs, whose page offset and anonymous page offset are identical, nor will it impact shared file-backed VMAs, which will continue to be merged based on the file-backed page offset. However, MAP_PRIVATE file-backed mappings must now be aligned on anonymous page offset as well. In most instances this should have no impact on merging of file-backed mappings, which are usually not merged all that often, let alone MAP_PRIVATE mapped ones, and rarely remapped and faulted before being moved back in place (the case in which a merge may now fail). One subtle impact of this change is in NUMA interleaving - since commit 88c91dc58582 ("mempolicy: migration attempt to match interleave nodes"), migration heuristically tries to maintain interleaving behaviour matching the policy using folio indices. When doing migration of CoW'd MAP_PRIVATE-file backed ranges, the 'base' upon which the interleaving behaviour is performed will vary for these ranges. However the commit notes that ranges spanning multiple VMAs will already cause varying bases, and that this is an acceptable approximation. It is very unlikely real world use-cases will be impacted by this (MAP_PRIVATE file-backed mappings are already an edge case), and all that will happen is that such ranges will cause interleaving to be rotated over the CoW'd range, with little to no impact. This commit lays the foundations for future scalable CoW work which needs to track some remaps, meaning that most remap tracking can be avoided, and in nearly all cases the anonymous page offset will be able to be used to quickly find the VMA in an mm. Note that the need_rmap_locks check doesn't need to be updated, as any remapping will offset both the anonymous and file-backed page offset, so it suffices to check only one. Link: https://lore.kernel.org/20260813-b4-scalable-cow-virt-pgoff-v5-14-c21581c0c3c8@kernel.org Signed-off-by: Lorenzo Stoakes (ARM) Acked-by: David Hildenbrand (Arm) Cc: Adrian Hunter Cc: Alexander Deucher Cc: Alexander Gordeev Cc: Alexander Shishkin Cc: Alistair Popple Cc: Arnaldo Carvalho de Melo Cc: Arnd Bergmann Cc: Baolin Wang Cc: Baoquan He Cc: Barry Song Cc: Boris Brezillon Cc: Byungchul Park Cc: Chengming Zhou Cc: Chris Li Cc: Christan König Cc: Christian Borntraeger Cc: Claudio Imbrenda Cc: Dave Airlie Cc: Dev Jain Cc: Gerald Schaefer Cc: Greg Kroah-Hartman Cc: Gregory Price (Meta) Cc: Harry Yoo Cc: Heiko Carstens Cc: Huang Ray Cc: "Huang, Ying" Cc: Ian Rogers Cc: Ingo Molnar Cc: James Clark Cc: Jan Kara Cc: Jann Horn Cc: Janosch Frank Cc: Jason Gunthorpe Cc: Jiri Olsa Cc: John Hubbard Cc: Joshua Hahn Cc: Kairui Song Cc: Kees Cook Cc: Kemeng Shi Cc: Lance Yang Cc: Liam R. Howlett Cc: Liviu Dudau Cc: Maarten Lankhorst Cc: Marc Rutland Cc: "Masami Hiramatsu (Google)" Cc: Matthew Auld Cc: Matthew Brost Cc: Matthew Wilcox (Oracle) Cc: Maxime Ripard Cc: Miaohe Lin Cc: Michal Hocko Cc: Mike Rapoport Cc: Muchun Song Cc: Namhyung kim Cc: Naoya Horiguchi Cc: Nhat Pham Cc: Nico Pache Cc: Oleg Nesterov Cc: Oscar Salvador Cc: Pedro Falcato Cc: Peter Xu Cc: Peter Zijlstra Cc: Rakie Kim Cc: Rik van Riel Cc: Rodrigo Vivi Cc: Ryan Roberts Cc: Steven Price Cc: Suren Baghdasaryan Cc: Sven Schnelle Cc: Thomas Hellström Cc: Thomas Zimemrmann Cc: Vasily Gorbik Cc: Vlastimil Babka Cc: xu xin Cc: Zi Yan Signed-off-by: Andrew Morton

mm: clean up vma_address_end()

2026-08-25T01:42:52+00:00

vma_address_end() is a confusing function with a lot of moving parts so clean it up prior to extending it for anon page indexed mappings. Const-ify some variables and establish pgoff_vma_start and pgoff_end variables to clearly identify the page offset for the start of the VMA and the end of the page offset range specified by the page walk. This simplifies the function significantly and lays the groundwork for a future change to update this function to account for anonymously page indexed folios. No functional change intended. Link: https://lore.kernel.org/20260813-b4-scalable-cow-virt-pgoff-v5-11-c21581c0c3c8@kernel.org Signed-off-by: Lorenzo Stoakes (ARM) Acked-by: David Hildenbrand (Arm) Cc: Adrian Hunter Cc: Alexander Deucher Cc: Alexander Gordeev Cc: Alexander Shishkin Cc: Alistair Popple Cc: Arnaldo Carvalho de Melo Cc: Arnd Bergmann Cc: Baolin Wang Cc: Baoquan He Cc: Barry Song Cc: Boris Brezillon Cc: Byungchul Park Cc: Chengming Zhou Cc: Chris Li Cc: Christan König Cc: Christian Borntraeger Cc: Claudio Imbrenda Cc: Dave Airlie Cc: Dev Jain Cc: Gerald Schaefer Cc: Greg Kroah-Hartman Cc: Gregory Price (Meta) Cc: Harry Yoo Cc: Heiko Carstens Cc: Huang Ray Cc: "Huang, Ying" Cc: Ian Rogers Cc: Ingo Molnar Cc: James Clark Cc: Jan Kara Cc: Jann Horn Cc: Janosch Frank Cc: Jason Gunthorpe Cc: Jiri Olsa Cc: John Hubbard Cc: Joshua Hahn Cc: Kairui Song Cc: Kees Cook Cc: Kemeng Shi Cc: Lance Yang Cc: Liam R. Howlett Cc: Liviu Dudau Cc: Maarten Lankhorst Cc: Marc Rutland Cc: "Masami Hiramatsu (Google)" Cc: Matthew Auld Cc: Matthew Brost Cc: Matthew Wilcox (Oracle) Cc: Maxime Ripard Cc: Miaohe Lin Cc: Michal Hocko Cc: Mike Rapoport Cc: Muchun Song Cc: Namhyung kim Cc: Naoya Horiguchi Cc: Nhat Pham Cc: Nico Pache Cc: Oleg Nesterov Cc: Oscar Salvador Cc: Pedro Falcato Cc: Peter Xu Cc: Peter Zijlstra Cc: Rakie Kim Cc: Rik van Riel Cc: Rodrigo Vivi Cc: Ryan Roberts Cc: Steven Price Cc: Suren Baghdasaryan Cc: Sven Schnelle Cc: Thomas Hellström Cc: Thomas Zimemrmann Cc: Vasily Gorbik Cc: Vlastimil Babka Cc: xu xin Cc: Zi Yan Signed-off-by: Andrew Morton

mm: introduce and use vma_filebacked_address()

2026-08-25T01:42:51+00:00

In cases where we know that the VMA is file-backed, use vma_filebacked_address() rather than vma_address(). This lays the foundation for using the anonymous page offset via vma_anon_address(). Also add an assert to ensure that the VMA whose address is required is not anonymous. No functional change intended. Link: https://lore.kernel.org/20260813-b4-scalable-cow-virt-pgoff-v5-6-c21581c0c3c8@kernel.org Signed-off-by: Lorenzo Stoakes (ARM) Tested-by: syzbot@syzkaller.appspotmail.com Acked-by: David Hildenbrand (Arm) Cc: Adrian Hunter Cc: Alexander Deucher Cc: Alexander Gordeev Cc: Alexander Shishkin Cc: Alistair Popple Cc: Arnaldo Carvalho de Melo Cc: Arnd Bergmann Cc: Baolin Wang Cc: Baoquan He Cc: Barry Song Cc: Boris Brezillon Cc: Byungchul Park Cc: Chengming Zhou Cc: Chris Li Cc: Christan König Cc: Christian Borntraeger Cc: Claudio Imbrenda Cc: Dave Airlie Cc: Dev Jain Cc: Gerald Schaefer Cc: Greg Kroah-Hartman Cc: Gregory Price (Meta) Cc: Harry Yoo Cc: Heiko Carstens Cc: Huang Ray Cc: "Huang, Ying" Cc: Ian Rogers Cc: Ingo Molnar Cc: James Clark Cc: Jan Kara Cc: Jann Horn Cc: Janosch Frank Cc: Jason Gunthorpe Cc: Jiri Olsa Cc: John Hubbard Cc: Joshua Hahn Cc: Kairui Song Cc: Kees Cook Cc: Kemeng Shi Cc: Lance Yang Cc: Liam R. Howlett Cc: Liviu Dudau Cc: Maarten Lankhorst Cc: Marc Rutland Cc: "Masami Hiramatsu (Google)" Cc: Matthew Auld Cc: Matthew Brost Cc: Matthew Wilcox (Oracle) Cc: Maxime Ripard Cc: Miaohe Lin Cc: Michal Hocko Cc: Mike Rapoport Cc: Muchun Song Cc: Namhyung kim Cc: Naoya Horiguchi Cc: Nhat Pham Cc: Nico Pache Cc: Oleg Nesterov Cc: Oscar Salvador Cc: Pedro Falcato Cc: Peter Xu Cc: Peter Zijlstra Cc: Rakie Kim Cc: Rik van Riel Cc: Rodrigo Vivi Cc: Ryan Roberts Cc: Steven Price Cc: Suren Baghdasaryan Cc: Sven Schnelle Cc: Thomas Hellström Cc: Thomas Zimemrmann Cc: Vasily Gorbik Cc: Vlastimil Babka Cc: xu xin Cc: Zi Yan Signed-off-by: Andrew Morton

mm: abstract vma_address() and introduce vma_anon_address()

2026-08-25T01:42:50+00:00

Introduce __vma_address() which abstracts the VMA start page offset field as pgoff_start, then update vma_address() to use it. Then introduce vma_anon_address() which does the equivalent of vma_address(), only using the anonymous page offset of the VMA rather than the file-backed one. Also add an assert to ensure that the function is not called for mappings which are file-backed but not MAP_PRIVATE to ensure it is only used in the correct places. This will be necessary for determining the address of a folio's index within a VMA when the folio belongs to a MAP_PRIVATE file-backed VMA but has been CoW'd, and thus is anonymous, once the anonymous VMA page offset field is used for the reverse mapping. No callers are updated, so no functional change intended. Link: https://lore.kernel.org/20260813-b4-scalable-cow-virt-pgoff-v5-4-c21581c0c3c8@kernel.org Signed-off-by: Lorenzo Stoakes (ARM) Acked-by: David Hildenbrand (Arm) Cc: Adrian Hunter Cc: Alexander Deucher Cc: Alexander Gordeev Cc: Alexander Shishkin Cc: Alistair Popple Cc: Arnaldo Carvalho de Melo Cc: Arnd Bergmann Cc: Baolin Wang Cc: Baoquan He Cc: Barry Song Cc: Boris Brezillon Cc: Byungchul Park Cc: Chengming Zhou Cc: Chris Li Cc: Christan König Cc: Christian Borntraeger Cc: Claudio Imbrenda Cc: Dave Airlie Cc: Dev Jain Cc: Gerald Schaefer Cc: Greg Kroah-Hartman Cc: Gregory Price (Meta) Cc: Harry Yoo Cc: Heiko Carstens Cc: Huang Ray Cc: "Huang, Ying" Cc: Ian Rogers Cc: Ingo Molnar Cc: James Clark Cc: Jan Kara Cc: Jann Horn Cc: Janosch Frank Cc: Jason Gunthorpe Cc: Jiri Olsa Cc: John Hubbard Cc: Joshua Hahn Cc: Kairui Song Cc: Kees Cook Cc: Kemeng Shi Cc: Lance Yang Cc: Liam R. Howlett Cc: Liviu Dudau Cc: Maarten Lankhorst Cc: Marc Rutland Cc: "Masami Hiramatsu (Google)" Cc: Matthew Auld Cc: Matthew Brost Cc: Matthew Wilcox (Oracle) Cc: Maxime Ripard Cc: Miaohe Lin Cc: Michal Hocko Cc: Mike Rapoport Cc: Muchun Song Cc: Namhyung kim Cc: Naoya Horiguchi Cc: Nhat Pham Cc: Nico Pache Cc: Oleg Nesterov Cc: Oscar Salvador Cc: Pedro Falcato Cc: Peter Xu Cc: Peter Zijlstra Cc: Rakie Kim Cc: Rik van Riel Cc: Rodrigo Vivi Cc: Ryan Roberts Cc: Steven Price Cc: Suren Baghdasaryan Cc: Sven Schnelle Cc: Thomas Hellström Cc: Thomas Zimemrmann Cc: Vasily Gorbik Cc: Vlastimil Babka Cc: xu xin Cc: Zi Yan Signed-off-by: Andrew Morton

mm: provide vma_[flags_]is_cow_mapping() and remove is_cow_mapping()

2026-08-25T01:42:50+00:00

All remaining callers of is_cow_mapping() are invoking it in the form of is_cow_mapping(vma->vm_flags) or an indirected version of this. Therefore, provide a helper - vma_is_cow_mapping() to directly test the VMA. Additionally provide a new helper vma_flags_is_cow_mapping() which performs the check using the new vma_flags_t type, and share this logic between vma_is_cow_mapping() and vma_desc_is_cow_mapping(). With these changes, no callers of is_cow_mapping() remain, so remove it. Also update the userland VMA tests to reflect the change. No functional change intended. [akpm@linux-foundation.org: fix kerneldoc comment typo, per Lorenzo] Link: https://lore.kernel.org/aob1goSSPH6sTN9y@gremlin Link: https://lore.kernel.org/20260813-b4-scalable-cow-virt-pgoff-v5-2-c21581c0c3c8@kernel.org Signed-off-by: Lorenzo Stoakes (ARM) Acked-by: David Hildenbrand (Arm) Cc: Adrian Hunter Cc: Alexander Deucher Cc: Alexander Gordeev Cc: Alexander Shishkin Cc: Alistair Popple Cc: Arnaldo Carvalho de Melo Cc: Arnd Bergmann Cc: Baolin Wang Cc: Baoquan He Cc: Barry Song Cc: Boris Brezillon Cc: Byungchul Park Cc: Chengming Zhou Cc: Chris Li Cc: Christan König Cc: Christian Borntraeger Cc: Claudio Imbrenda Cc: Dave Airlie Cc: Dev Jain Cc: Gerald Schaefer Cc: Greg Kroah-Hartman Cc: Gregory Price (Meta) Cc: Harry Yoo Cc: Heiko Carstens Cc: Huang Ray Cc: "Huang, Ying" Cc: Ian Rogers Cc: Ingo Molnar Cc: James Clark Cc: Jan Kara Cc: Jann Horn Cc: Janosch Frank Cc: Jason Gunthorpe Cc: Jiri Olsa Cc: John Hubbard Cc: Joshua Hahn Cc: Kairui Song Cc: Kees Cook Cc: Kemeng Shi Cc: Lance Yang Cc: Liam R. Howlett Cc: Liviu Dudau Cc: Maarten Lankhorst Cc: Marc Rutland Cc: "Masami Hiramatsu (Google)" Cc: Matthew Auld Cc: Matthew Brost Cc: Matthew Wilcox (Oracle) Cc: Maxime Ripard Cc: Miaohe Lin Cc: Michal Hocko Cc: Mike Rapoport Cc: Muchun Song Cc: Namhyung kim Cc: Naoya Horiguchi Cc: Nhat Pham Cc: Nico Pache Cc: Oleg Nesterov Cc: Oscar Salvador Cc: Pedro Falcato Cc: Peter Xu Cc: Peter Zijlstra Cc: Rakie Kim Cc: Rik van Riel Cc: Rodrigo Vivi Cc: Ryan Roberts Cc: Steven Price Cc: Suren Baghdasaryan Cc: Sven Schnelle Cc: Thomas Hellström Cc: Thomas Zimemrmann Cc: Vasily Gorbik Cc: Vlastimil Babka Cc: xu xin Cc: Zi Yan Signed-off-by: Andrew Morton

mm: page_alloc: fix non-movable reclaim storm in defrag_mode

2026-08-07T01:57:24+00:00

As we deployed defrag_mode into Meta production, pressure spikes and excessive swapping were observed on some workloads. Tracing confirmed that this is unmovable/reclaimable requests spinning in the allocator and direct reclaim, causing excessive amounts of swap. The initial plan for defrag_mode was to rely on kswapd/kcompactd to produce blocks, and if those are overwhelmed under high pressure, let the allocator fall back (__rmqueue_steal()) after its retry loops. However, that retrying results in more reclaim on some of these workloads than we'd hoped, sometimes excessively so, spurred on by the !costly order conditions in should_reclaim_retry(). The storms are dependent on the request type. Reclaim will inevitably make room in existing movable blocks, since that's where the LRU pages live. So if movable requests retry on reclaim, they make progress. When non-movable requests spin in reclaim that isn't productive. They cannot use the individually freed pages, and the process is unlikely to accidentally free whole blocks to meet the ALLOC_NOFRAGMENT bar. They spin and overreclaim excessively, which tanks performance and triggers userspace guards like swap exhaustion or pressure based OOM. To fix this, send non-movable requests, regardless of order, into pageblock reclaim/compaction. This way, they help move things along to meet the ALLOC_NOFRAGMENT bar. After this patch, the reclaim storms and excess OOM rates are no longer observed in production. The longer-term plan is still to have all requests, including the movable ones, help make blocks to spread the cost of defragmenting more evenly and fairly; combined with proper watermarking to reduce allocation latencies in the common case. However, doing this naively unearths scaling and concurrency limitations in compaction that need to be addressed first. Promoting just non-movables for now is the minimally viable bug fix for the above issue. [brendan.jackman@linux.dev: fix try_to_compact_pages() kerneldoc] Link: https://lore.kernel.org/DK7NM9RPUJOD.11PNJJ5N2OBED@linux.dev Link: https://lore.kernel.org/20260722150006.3848560-5-hannes@cmpxchg.org Fixes: e3aa7df331bc ("mm: page_alloc: defrag_mode") Signed-off-by: Johannes Weiner Signed-off-by: "Brendan Jackman" Reviewed-by: Vlastimil Babka (SUSE) Cc: Brendan Jackman Cc: David Hildenbrand Cc: Gregory Price Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Mike Rapoport Cc: Shakeel Butt Cc: Suren Baghdasaryan Cc: Zi Yan Cc: Signed-off-by: Andrew Morton

mm: page_alloc: move capture_control to the page allocator

2026-08-07T01:57:24+00:00

The compaction capturing code assumes the allocation request order and compaction target order are the same. That won't be true once defrag_mode promotes sub-block allocations to pageblock-order compaction: compaction targets the larger order, while capture should remain at the original allocation order. Move the capture_control to the page allocator and give it its own copies of what the page freeing path matches against - zone, migratetype and the allocation order - rather than reaching into compaction's live compact_control. __alloc_pages_direct_compact() fills in migratetype and order, and installs and hides current->capture_control around the whole compaction call; try_to_compact_pages() aims capc->zone at each zone while it is being compacted. compact_zone_order() no longer deals with capture at all. Pass the capture_control through try_to_compact_pages() / compact_zone_order() in place of the bare struct page **. No functional change. Link: https://lore.kernel.org/20260722150006.3848560-4-hannes@cmpxchg.org Fixes: e3aa7df331bc ("mm: page_alloc: defrag_mode") Signed-off-by: Vlastimil Babka (SUSE) Co-developed-by: Johannes Weiner Signed-off-by: Johannes Weiner Reviewed-by: Gregory Price Cc: Brendan Jackman Cc: Brendan Jackman Cc: David Hildenbrand Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Mike Rapoport Cc: Shakeel Butt Cc: Suren Baghdasaryan Cc: Zi Yan Cc: Signed-off-by: Andrew Morton

mm/memory: batch set uffd-wp markers during zapping

2026-08-07T01:57:20+00:00

Enable batch setting of uffd-wp PTE markers. The code paths passing nr > 1 to zap_install_uffd_wp_if_needed() produce that nr through either folio_pte_batch() or swap_pte_batch(), therefore batching is correct: 1) All PTEs belong to the same type of VMA: anonymous or non-anonymous, wp-armed or non-wp-armed. 2) All PTEs are either marked with uffd-wp or not marked with uffd-wp; the same applies to the pte_swp_uffd_any() check. 3) uffd_supports_wp_marker() is independent of the function parameters. Use set_pte_at() in a loop instead of set_ptes(), because set_ptes() cannot handle nonpresent to nonpresent conversion for nr_pages > 1. Rename the helper to cond_install_uffd_wp_ptes(). Link: https://lore.kernel.org/20260720065508.2695106-3-dev.jain@arm.com Signed-off-by: Dev Jain Acked-by: David Hildenbrand (Arm) Cc: Anshuman Khandual Cc: Axel Rasmussen Cc: Barry Song Cc: Harry Yoo Cc: Jann Horn Cc: Kairui Song Cc: Lance Yang Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Mike Rapoport Cc: Rik van Riel Cc: Ryan Roberts Cc: Shakeel Butt Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Wei Xu Cc: Yuanchu Xie Signed-off-by: Andrew Morton