kernel/linux.git/mm/compaction.c, branch v6.18.40

mm/compaction: handle free_pages_prepare() properly in compaction_free()

2026-07-24T14:17:15+00:00

commit 7da7d599b8a83271c464adfd5ef160202b470570 upstream. free_pages_prepare() can fail but compaction_free() does not handle the failure case. Failed pages should not be added back to cc->freepages for future use, since they can be either PageHWPoison or free_page_is_bad() and might cause data corruption. Link: https://lore.kernel.org/20260622-handle_free_pages_prepare_in_compaction_free-v1-1-fcf3b14abcf7@nvidia.com Fixes: 733aea0b3a7b ("mm/compaction: add support for >0 order folio memory compaction.") Signed-off-by: Zi Yan Reviewed-by: Vlastimil Babka (SUSE) Acked-by: Johannes Weiner Reviewed-by: Baolin Wang Reviewed-by: Lance Yang Cc: Brendan Jackman Cc: Jiaqi Yan Cc: Michal Hocko Cc: Suren Baghdasaryan Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

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

mm/migration: remove PageMovable()

2025-07-13T23:38:28+00:00

Previously, if __ClearPageMovable() were invoked on a page, this would cause __PageMovable() to return false, but due to the continued existence of page movable ops, PageMovable() would have returned true. With __ClearPageMovable() gone, the two are exactly equivalent. So we can replace PageMovable() checks by __PageMovable(). In fact, __PageMovable() cannot change until a page is freed, so we can turn some PageMovable() into sanity checks for __PageMovable(). Link: https://lkml.kernel.org/r/20250704102524.326966-16-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/migrate: remove __ClearPageMovable()

2025-07-13T23:38:28+00:00

Unused, let's remove it. The Chinese docs in Documentation/translations/zh_CN/mm/page_migration.rst still mention it, but that whole docs is destined to get outdated and updated by somebody that actually speaks that language. Link: https://lkml.kernel.org/r/20250704102524.326966-15-david@redhat.com Signed-off-by: David Hildenbrand Reviewed-by: Zi Yan Reviewed-by: Harry Yoo 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: "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/migrate: rename isolate_movable_page() to isolate_movable_ops_page()

2025-07-13T23:38:26+00:00

... and start moving back to per-page things that will absolutely not be folio things in the future. Add documentation and a comment that the remaining folio stuff (lock, refcount) will have to be reworked as well. While at it, convert the VM_BUG_ON() into a WARN_ON_ONCE() and handle it gracefully (relevant with further changes), and convert a WARN_ON_ONCE() into a VM_WARN_ON_ONCE_PAGE(). Note that we will leave anything that needs a rework (lock, refcount, ->lru) to be using folios for now: that perfectly highlights the problematic bits. Link: https://lkml.kernel.org/r/20250704102524.326966-8-david@redhat.com Signed-off-by: David Hildenbrand Reviewed-by: Zi Yan Reviewed-by: Harry Yoo 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: "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: page_alloc: tighten up find_suitable_fallback()

2025-05-12T00:48:18+00:00

find_suitable_fallback() is not as efficient as it could be, and somewhat difficult to follow. 1. should_try_claim_block() is a loop invariant. There is no point in checking fallback areas if the caller is interested in claimable blocks but the order and the migratetype don't allow for that. 2. __rmqueue_steal() doesn't care about claimability, so it shouldn't have to run those tests. Different callers want different things from this helper: 1. __compact_finished() scans orders up until it finds a claimable block 2. __rmqueue_claim() scans orders down as long as blocks are claimable 3. __rmqueue_steal() doesn't care about claimability at all Move should_try_claim_block() out of the loop. Only test it for the two callers who care in the first place. Distinguish "no blocks" from "order + mt are not claimable" in the return value; __rmqueue_claim() can stop once order becomes unclaimable, __compact_finished() can keep advancing until order becomes claimable. Before: Performance counter stats for './run case-lru-file-mmap-read' (5 runs): 85,294.85 msec task-clock # 5.644 CPUs utilized ( +- 0.32% ) 15,968 context-switches # 187.209 /sec ( +- 3.81% ) 153 cpu-migrations # 1.794 /sec ( +- 3.29% ) 801,808 page-faults # 9.400 K/sec ( +- 0.10% ) 733,358,331,786 instructions # 1.87 insn per cycle ( +- 0.20% ) (64.94%) 392,622,904,199 cycles # 4.603 GHz ( +- 0.31% ) (64.84%) 148,563,488,531 branches # 1.742 G/sec ( +- 0.18% ) (63.86%) 152,143,228 branch-misses # 0.10% of all branches ( +- 1.19% ) (62.82%) 15.1128 +- 0.0637 seconds time elapsed ( +- 0.42% ) After: Performance counter stats for './run case-lru-file-mmap-read' (5 runs): 84,380.21 msec task-clock # 5.664 CPUs utilized ( +- 0.21% ) 16,656 context-switches # 197.392 /sec ( +- 3.27% ) 151 cpu-migrations # 1.790 /sec ( +- 3.28% ) 801,703 page-faults # 9.501 K/sec ( +- 0.09% ) 731,914,183,060 instructions # 1.88 insn per cycle ( +- 0.38% ) (64.90%) 388,673,535,116 cycles # 4.606 GHz ( +- 0.24% ) (65.06%) 148,251,482,143 branches # 1.757 G/sec ( +- 0.37% ) (63.92%) 149,766,550 branch-misses # 0.10% of all branches ( +- 1.22% ) (62.88%) 14.8968 +- 0.0486 seconds time elapsed ( +- 0.33% ) Link: https://lkml.kernel.org/r/20250407180154.63348-2-hannes@cmpxchg.org Signed-off-by: Johannes Weiner Reviewed-by: Brendan Jackman Tested-by: Shivank Garg Reviewed-by: Vlastimil Babka Cc: Carlos Song Cc: Mel Gorman Signed-off-by: Andrew Morton