kernel/git/stable/linux.git/fs/proc/page.c, branch master

fs: stable_page_flags(): simplify KPF_IDLE handling

2026-08-07T01:57:19+00:00

For KPF_IDLE, folio_test_idle() check in set_ps_flags() already handles all config cases, so remove the duplicate code in stable_page_flags() that deals with CONFIG_PAGE_IDLE_FLAG for the 64‑bit case. No functional change is intended. Link: https://lore.kernel.org/20260720033021.4091944-4-tujinjiang@huawei.com Signed-off-by: Jinjiang Tu Acked-by: David Hildenbrand (Arm) Cc: Chengming Zhou Cc: Kefeng Wang Cc: Luiz Capitulino Cc: Matthew Wilcox (Oracle) Cc: Miaohe Lin Cc: Nanyong Sun Cc: Svetly Todorov Cc: xu xin Cc: Zi Yan Signed-off-by: Andrew Morton

fs: stable_page_flags(): use folio_test_*() helpers

2026-08-07T01:57:19+00:00

Since commit 304daa8132a9 ("maps4: add /proc/kpageflags interface"), /proc/kpageflags directly operates on page->flags to determine page status. Later, commit 177975495914 ("proc: export more page flags in /proc/kpageflags") started using page helper functions when exposing new flags, leading to a mix of both approaches. For tail pages, the original code did not return corresponding status. commit 0a71649cb724 ("/proc/kpageflags: return KPF_SLAB for slab tail pages") and commit 832fc1de01ae ("/proc/kpageflags: return KPF_BUDDY for "tail" buddy pages") made tail slab/buddy pages also return corresponding status. Then commit dee3d0bef2b0 ("proc: rewrite stable_page_flags()") made all tail pages return the same status as their head page, except for hwpoison and mapped flags. It also cached the folio's flags and operate on the flags directly to avoid concurrency issues if using folio_test_*() helpers. Since commit 476d87d6a061 ("fs: stable_page_flags(): use snapshot_page()"), we can now safely switch to folio_test_*() helpers instead of directly operating on flags, which is more readable and consistent with the rest of the kernel. Only convert cfolio-specific flags (i.e., anon, ksm, swapcache) to folio_test_*() helpers, which reduces redundant code. Keep others unchanged due to they aren't folio-specific flags or coverting them doesn't cleanup. No functional change is intended. Link: https://lore.kernel.org/20260720033021.4091944-3-tujinjiang@huawei.com Signed-off-by: Jinjiang Tu Acked-by: David Hildenbrand (Arm) Cc: Chengming Zhou Cc: Kefeng Wang Cc: Luiz Capitulino Cc: Matthew Wilcox (Oracle) Cc: Miaohe Lin Cc: Nanyong Sun Cc: Svetly Todorov Cc: xu xin Cc: Zi Yan Signed-off-by: Andrew Morton

fs: stable_page_flags(): use BIT_ULL() for KPF flags

2026-08-07T01:57:19+00:00

Patch series "cleanup for stable_page_flags()", v2. This series cleans up stable_page_flags(), see the details in the commit messages. This patch (of 3): The stable_page_flags() function currently sets page flag bits using "1 << KPF_xxx" for various KPF_* definitions. KPF_* may be larger than 32, which will trigger -Wshift-count-overflow warning. All KPF_* values currently used in "1 << KPF_xxx" are smaller than 33, so no warning is triggered with current code. Replace all occurrences of "1 << KPF_*" with the BIT_ULL() macro to ensure all shifts are performed on a 64-bit unsigned type. This makes the code robust, and safe for future extension. No functional change is intended. Link: https://lore.kernel.org/20260720033021.4091944-1-tujinjiang@huawei.com Link: https://lore.kernel.org/20260720033021.4091944-2-tujinjiang@huawei.com Signed-off-by: Jinjiang Tu Acked-by: David Hildenbrand (Arm) Acked-by: Zi Yan Cc: Chengming Zhou Cc: Kefeng Wang Cc: Luiz Capitulino Cc: Matthew Wilcox (Oracle) Cc: Miaohe Lin Cc: Nanyong Sun Cc: Svetly Todorov Cc: xu xin Signed-off-by: Andrew Morton

fs/proc: fix KPF_KSM reported for all anonymous pages

2026-07-02T02:02:54+00:00

Reading /proc/kpageflags for any anonymous page returns KPF_KSM set, even when KSM is not in use. As a result, tools misclassify all anonymous pages as KSM merged. In stable_page_flags(), if the page is anonymous, then use (mapping & FOLIO_MAPPING_KSM) check to identify if the anonymous page is KSM page. However, FOLIO_MAPPING_KSM is FOLIO_MAPPING_ANON | FOLIO_MAPPING_ANON_KSM, (mapping & FOLIO_MAPPING_KSM) check returns true for all anonymous pages. To fix it, use FOLIO_MAPPING_ANON_KSM instead. Link: https://lore.kernel.org/20260629033122.774318-1-tujinjiang@huawei.com Link: https://lore.kernel.org/20260626013252.2846774-1-tujinjiang@huawei.com Fixes: dee3d0bef2b0 ("proc: rewrite stable_page_flags()") Signed-off-by: Jinjiang Tu Acked-by: David Hildenbrand (Arm) Acked-by: Zi Yan Reviewed-by: Xu Xin Cc: Chengming Zhou Cc: Kefeng Wang Cc: Luiz Capitulino Cc: Matthew Wilcox (Oracle) Cc: Miaohe Lin Cc: Nanyong Sun Cc: Svetly Todorov Cc: Signed-off-by: Andrew Morton

fs/proc/page: remove unused KPMBITS

2025-11-20T22:03:42+00:00

KPMBITS is never referenced in the code. Just remove it. Link: https://lkml.kernel.org/r/20251106010735.1603-1-zhangjiao2@cmss.chinamobile.com Signed-off-by: zhang jiao Reviewed-by: Zi Yan Cc: David Hildenbrand Cc: Liu Ye Cc: Luiz Capitulino Cc: Matthew Wilcox (Oracle) Cc: Miaohe Lin Signed-off-by: Andrew Morton

mm/hwpoison: decouple hwpoison_filter from mm/memory-failure.c

2025-09-21T21:22:21+00:00

mm/memory-failure.c defines and uses hwpoison_filter_* parameters but the values of those parameters can only be modified via mm/hwpoison-inject.c from userspace. They have a potentially different life time. Decouple those parameters from mm/memory-failure.c to fix this broken layering. Link: https://lkml.kernel.org/r/20250904062258.3336092-1-linmiaohe@huawei.com Signed-off-by: Miaohe Lin Suggested-by: Michal Hocko Cc: David Hildenbrand Cc: Naoya Horiguchi Signed-off-by: Andrew Morton

mm: introduce memdesc_flags_t

2025-09-13T23:55:07+00:00

Patch series "Add and use memdesc_flags_t". At some point struct page will be separated from struct slab and struct folio. This is a step towards that by introducing a type for the 'flags' word of all three structures. This gives us a certain amount of type safety by establishing that some of these unsigned longs are different from other unsigned longs in that they contain things like node ID, section number and zone number in the upper bits. That lets us have functions that can be easily called by anyone who has a slab, folio or page (but not easily by anyone else) to get the node or zone. There's going to be some unusual merge problems with this as some odd bits of the kernel decide they want to print out the flags value or something similar by writing page->flags and now they'll need to write page->flags.f instead. That's most of the churn here. Maybe we should be removing these things from the debug output? This patch (of 11): Wrap the unsigned long flags in a typedef. In upcoming patches, this will provide a strong hint that you can't just pass a random unsigned long to functions which take this as an argument. [willy@infradead.org: s/flags/flags.f/ in several architectures] Link: https://lkml.kernel.org/r/aKMgPRLD-WnkPxYm@casper.infradead.org [nicola.vetrini@gmail.com: mips: fix compilation error] Link: https://lore.kernel.org/lkml/CA+G9fYvkpmqGr6wjBNHY=dRp71PLCoi2341JxOudi60yqaeUdg@mail.gmail.com/ Link: https://lkml.kernel.org/r/20250825214245.1838158-1-nicola.vetrini@gmail.com Link: https://lkml.kernel.org/r/20250805172307.1302730-1-willy@infradead.org Link: https://lkml.kernel.org/r/20250805172307.1302730-2-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) Signed-off-by: Matthew Wilcox (Oracle) Acked-by: Zi Yan Cc: Shakeel Butt Signed-off-by: Andrew Morton

fs: stable_page_flags(): use snapshot_page()

2025-07-25T02:12:35+00:00

A race condition is possible in stable_page_flags() where user-space is reading /proc/kpageflags concurrently to a folio split. This may lead to oopses or BUG_ON()s being triggered. To fix this, this commit uses snapshot_page() in stable_page_flags() so that stable_page_flags() works with a stable page and folio snapshots instead. Note that stable_page_flags() makes use of some functions that require the original page or folio pointer to work properly (eg. is_free_budy_page() and folio_test_idle()). Since those functions can't be used on the page snapshot, we replace their usage with flags that were set by snapshot_page() for this purpose. Link: https://lkml.kernel.org/r/52c16c0f00995a812a55980c2f26848a999a34ab.1752499009.git.luizcap@redhat.com Signed-off-by: Luiz Capitulino Reviewed-by: Shivank Garg Tested-by: Harry Yoo Acked-by: David Hildenbrand Cc: Matthew Wilcox (Oracle) Cc: Oscar Salvador Cc: SeongJae Park Signed-off-by: Andrew Morton

proc: kpagecount: use snapshot_page()

2025-07-25T02:12:35+00:00

Currently, the call to folio_precise_page_mapcount() from kpage_read() can race with a folio split. When the race happens we trigger a VM_BUG_ON_FOLIO() in folio_entire_mapcount() (see splat below). This commit fixes this race by using snapshot_page() so that we retrieve the folio mapcount using a folio snapshot. [ 2356.558576] page: refcount:1 mapcount:1 mapping:0000000000000000 index:0xffff85200 pfn:0x6f7c00 [ 2356.558748] memcg:ffff000651775780 [ 2356.558763] anon flags: 0xafffff60020838(uptodate|dirty|lru|owner_2|swapbacked|node=1|zone=2|lastcpupid=0xfffff) [ 2356.558796] raw: 00afffff60020838 fffffdffdb5d0048 fffffdffdadf7fc8 ffff00064c1629c1 [ 2356.558817] raw: 0000000ffff85200 0000000000000000 0000000100000000 ffff000651775780 [ 2356.558839] page dumped because: VM_BUG_ON_FOLIO(!folio_test_large(folio)) [ 2356.558882] ------------[ cut here ]------------ [ 2356.558897] kernel BUG at ./include/linux/mm.h:1103! [ 2356.558982] Internal error: Oops - BUG: 00000000f2000800 [#1] SMP [ 2356.564729] CPU: 8 UID: 0 PID: 1864 Comm: folio-split-rac Tainted: G S W 6.15.0+ #3 PREEMPT(voluntary) [ 2356.566196] Tainted: [S]=CPU_OUT_OF_SPEC, [W]=WARN [ 2356.566814] Hardware name: Red Hat KVM, BIOS edk2-20241117-3.el9 11/17/2024 [ 2356.567684] pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) [ 2356.568563] pc : kpage_read.constprop.0+0x26c/0x290 [ 2356.569605] lr : kpage_read.constprop.0+0x26c/0x290 [ 2356.569992] sp : ffff80008fb739b0 [ 2356.570263] x29: ffff80008fb739b0 x28: ffff00064aa69580 x27: 00000000ff000000 [ 2356.570842] x26: 0000fffffffffff8 x25: ffff00064aa69580 x24: ffff80008fb73ae0 [ 2356.571411] x23: 0000000000000001 x22: 0000ffff86c6e8b8 x21: 0000000000000008 [ 2356.571978] x20: 00000000006f7c00 x19: 0000ffff86c6e8b8 x18: 0000000000000000 [ 2356.572581] x17: 3630303066666666 x16: 0000000000000003 x15: 0000000000001000 [ 2356.573217] x14: 00000000ffffffff x13: 0000000000000004 x12: 00aaaaaa00aaaaaa [ 2356.577674] x11: 0000000000000000 x10: 00aaaaaa00aaaaaa x9 : ffffbf3afca6c300 [ 2356.578332] x8 : 0000000000000002 x7 : 0000000000000001 x6 : 0000000000000001 [ 2356.578984] x5 : ffff000c79812408 x4 : 0000000000000000 x3 : 0000000000000000 [ 2356.579635] x2 : 0000000000000000 x1 : ffff00064aa69580 x0 : 000000000000003e [ 2356.580286] Call trace: [ 2356.580524] kpage_read.constprop.0+0x26c/0x290 (P) [ 2356.580982] kpagecount_read+0x28/0x40 [ 2356.581336] proc_reg_read+0x38/0x100 [ 2356.581681] vfs_read+0xcc/0x320 [ 2356.581992] ksys_read+0x74/0x118 [ 2356.582306] __arm64_sys_read+0x24/0x38 [ 2356.582668] invoke_syscall+0x70/0x100 [ 2356.583022] el0_svc_common.constprop.0+0x48/0xf8 [ 2356.583456] do_el0_svc+0x28/0x40 [ 2356.583930] el0_svc+0x38/0x118 [ 2356.584328] el0t_64_sync_handler+0x144/0x168 [ 2356.584883] el0t_64_sync+0x19c/0x1a0 [ 2356.585350] Code: aa0103e0 9003a541 91082021 97f813fc (d4210000) [ 2356.586130] ---[ end trace 0000000000000000 ]--- [ 2356.587377] note: folio-split-rac[1864] exited with irqs disabled [ 2356.588050] note: folio-split-rac[1864] exited with preempt_count 1 Link: https://lkml.kernel.org/r/1c05cc725b90962d56323ff2e28e9cc3ae397b68.1752499009.git.luizcap@redhat.com Signed-off-by: Luiz Capitulino Reported-by: syzbot+3d7dc5eaba6b932f8535@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/67812fbd.050a0220.d0267.0030.GAE@google.com/Reviewed-by: Shivank Garg Tested-by: Harry Yoo Acked-by: David Hildenbrand Cc: Matthew Wilcox (Oracle) Cc: Oscar Salvador Cc: SeongJae Park Signed-off-by: Andrew Morton

mm: rename PAGE_MAPPING_* to FOLIO_MAPPING_*

2025-07-13T23:38:31+00:00

Now that the mapping flags are only used for folios, let's rename the defines. Link: https://lkml.kernel.org/r/20250704102524.326966-27-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