kernel/linux.git/mm/filemap.c, branch v6.12.80

mm/memory: do not populate page table entries beyond i_size

2025-11-24T09:36:07+00:00

commit 74207de2ba10c2973334906822dc94d2e859ffc5 upstream. Patch series "Fix SIGBUS semantics with large folios", v3. Accessing memory within a VMA, but beyond i_size rounded up to the next page size, is supposed to generate SIGBUS. Darrick reported[1] an xfstests regression in v6.18-rc1. generic/749 failed due to missing SIGBUS. This was caused by my recent changes that try to fault in the whole folio where possible: 19773df031bc ("mm/fault: try to map the entire file folio in finish_fault()") 357b92761d94 ("mm/filemap: map entire large folio faultaround") These changes did not consider i_size when setting up PTEs, leading to xfstest breakage. However, the problem has been present in the kernel for a long time - since huge tmpfs was introduced in 2016. The kernel happily maps PMD-sized folios as PMD without checking i_size. And huge=always tmpfs allocates PMD-size folios on any writes. I considered this corner case when I implemented a large tmpfs, and my conclusion was that no one in their right mind should rely on receiving a SIGBUS signal when accessing beyond i_size. I cannot imagine how it could be useful for the workload. But apparently filesystem folks care a lot about preserving strict SIGBUS semantics. Generic/749 was introduced last year with reference to POSIX, but no real workloads were mentioned. It also acknowledged the tmpfs deviation from the test case. POSIX indeed says[3]: References within the address range starting at pa and continuing for len bytes to whole pages following the end of an object shall result in delivery of a SIGBUS signal. The patchset fixes the regression introduced by recent changes as well as more subtle SIGBUS breakage due to split failure on truncation. This patch (of 2): Accesses within VMA, but beyond i_size rounded up to PAGE_SIZE are supposed to generate SIGBUS. Recent changes attempted to fault in full folio where possible. They did not respect i_size, which led to populating PTEs beyond i_size and breaking SIGBUS semantics. Darrick reported generic/749 breakage because of this. However, the problem existed before the recent changes. With huge=always tmpfs, any write to a file leads to PMD-size allocation. Following the fault-in of the folio will install PMD mapping regardless of i_size. Fix filemap_map_pages() and finish_fault() to not install: - PTEs beyond i_size; - PMD mappings across i_size; Make an exception for shmem/tmpfs that for long time intentionally mapped with PMDs across i_size. Link: https://lkml.kernel.org/r/20251027115636.82382-1-kirill@shutemov.name Link: https://lkml.kernel.org/r/20251027115636.82382-2-kirill@shutemov.name Signed-off-by: Kiryl Shutsemau Fixes: 6795801366da ("xfs: Support large folios") Reported-by: "Darrick J. Wong" Cc: Al Viro Cc: Baolin Wang Cc: Christian Brauner Cc: Dave Chinner Cc: David Hildenbrand Cc: Hugh Dickins Cc: Johannes Weiner Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Mike Rapoport Cc: Rik van Riel Cc: Shakeel Butt Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Signed-off-by: Andrew Morton Signed-off-by: Kiryl Shutsemau Signed-off-by: Greg Kroah-Hartman

readahead: fix return value of page_cache_next_miss() when no hole is found

2025-08-28T14:30:58+00:00

commit bbcaee20e03ecaeeecba32a703816a0d4502b6c4 upstream. max_scan in page_cache_next_miss always decreases to zero when no hole is found, causing the return value to be index + 0. Fix this by preserving the max_scan value throughout the loop. Jan said "From what I know and have seen in the past, wrong responses from page_cache_next_miss() can lead to readahead window reduction and thus reduced read speeds." Link: https://lkml.kernel.org/r/20250605054935.2323451-1-chizhiling@163.com Fixes: 901a269ff3d5 ("filemap: fix page_cache_next_miss() when no hole found") Signed-off-by: Chi Zhiling Reviewed-by: Jan Kara Cc: Josef Bacik Cc: Matthew Wilcox (Oracle) Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

mm: fix filemap_get_folios_contig returning batches of identical folios

2025-04-25T08:47:53+00:00

commit 8ab1b16023961dc640023b10436d282f905835ad upstream. filemap_get_folios_contig() is supposed to return distinct folios found within [start, end]. Large folios in the Xarray become multi-index entries. xas_next() can iterate through the sub-indexes before finding a sibling entry and breaking out of the loop. This can result in a returned folio_batch containing an indeterminate number of duplicate folios, which forces the callers to skeptically handle the returned batch. This is inefficient and incurs a large maintenance overhead. We can fix this by calling xas_advance() after we have successfully adding a folio to the batch to ensure our Xarray is positioned such that it will correctly find the next folio - similar to filemap_get_read_batch(). Link: https://lkml.kernel.org/r/Z-8s1-kiIDkzgRbc@fedora Fixes: 35b471467f88 ("filemap: add filemap_get_folios_contig()") Signed-off-by: Vishal Moola (Oracle) Reported-by: Qu Wenruo Closes: https://lkml.kernel.org/r/b714e4de-2583-4035-b829-72cfb5eb6fc6@gmx.com Tested-by: Qu Wenruo Cc: Matthew Wilcox (Oracle) Cc: Vivek Kasireddy Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

mm: fix error handling in __filemap_get_folio() with FGP_NOWAIT

2025-03-28T21:03:30+00:00

commit 182db972c9568dc530b2f586a2f82dfd039d9f2a upstream. original report: https://lore.kernel.org/all/CAKhLTr1UL3ePTpYjXOx2AJfNk8Ku2EdcEfu+CH1sf3Asr=B-Dw@mail.gmail.com/T/ When doing buffered writes with FGP_NOWAIT, under memory pressure, the system returned ENOMEM despite there being plenty of available memory, to be reclaimed from page cache. The user space used io_uring interface, which in turn submits I/O with FGP_NOWAIT (the fast path). retsnoop pointed to iomap_get_folio: 00:34:16.180612 -> 00:34:16.180651 TID/PID 253786/253721 (reactor-1/combined_tests): entry_SYSCALL_64_after_hwframe+0x76 do_syscall_64+0x82 __do_sys_io_uring_enter+0x265 io_submit_sqes+0x209 io_issue_sqe+0x5b io_write+0xdd xfs_file_buffered_write+0x84 iomap_file_buffered_write+0x1a6 32us [-ENOMEM] iomap_write_begin+0x408 iter=&{.inode=0xffff8c67aa031138,.len=4096,.flags=33,.iomap={.addr=0xffffffffffffffff,.length=4096,.type=1,.flags=3,.bdev=0x… pos=0 len=4096 foliop=0xffffb32c296b7b80 ! 4us [-ENOMEM] iomap_get_folio iter=&{.inode=0xffff8c67aa031138,.len=4096,.flags=33,.iomap={.addr=0xffffffffffffffff,.length=4096,.type=1,.flags=3,.bdev=0x… pos=0 len=4096 This is likely a regression caused by 66dabbb65d67 ("mm: return an ERR_PTR from __filemap_get_folio"), which moved error handling from io_map_get_folio() to __filemap_get_folio(), but broke FGP_NOWAIT handling, so ENOMEM is being escaped to user space. Had it correctly returned -EAGAIN with NOWAIT, either io_uring or user space itself would be able to retry the request. It's not enough to patch io_uring since the iomap interface is the one responsible for it, and pwritev2(RWF_NOWAIT) and AIO interfaces must return the proper error too. The patch was tested with scylladb test suite (its original reproducer), and the tests all pass now when memory is pressured. Link: https://lkml.kernel.org/r/20250224143700.23035-1-raphaelsc@scylladb.com Fixes: 66dabbb65d67 ("mm: return an ERR_PTR from __filemap_get_folio") Signed-off-by: Raphael S. Carvalho Reviewed-by: Christoph Hellwig Reviewed-by: Dave Chinner Cc: "Darrick J. Wong" Cc: Matthew Wilcow (Oracle) Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

cachestat: fix page cache statistics permission checking

2025-02-01T17:39:38+00:00

commit 5f537664e705b0bf8b7e329861f20128534f6a83 upstream. When the 'cachestat()' system call was added in commit cf264e1329fb ("cachestat: implement cachestat syscall"), it was meant to be a much more convenient (and performant) version of mincore() that didn't need mapping things into the user virtual address space in order to work. But it ended up missing the "check for writability or ownership" fix for mincore(), done in commit 134fca9063ad ("mm/mincore.c: make mincore() more conservative"). This just adds equivalent logic to 'cachestat()', modified for the file context (rather than vma). Reported-by: Sudheendra Raghav Neela Fixes: cf264e1329fb ("cachestat: implement cachestat syscall") Tested-by: Johannes Weiner Acked-by: Johannes Weiner Acked-by: Nhat Pham Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

filemap: avoid truncating 64-bit offset to 32 bits

2025-01-23T16:23:00+00:00

commit f505e6c91e7a22d10316665a86d79f84d9f0ba76 upstream. On 32-bit kernels, folio_seek_hole_data() was inadvertently truncating a 64-bit value to 32 bits, leading to a possible infinite loop when writing to an xfs filesystem. Link: https://lkml.kernel.org/r/20250102190540.1356838-1-marco.nelissen@gmail.com Fixes: 54fa39ac2e00 ("iomap: use mapping_seek_hole_data") Signed-off-by: Marco Nelissen Cc: Matthew Wilcox (Oracle) Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

filemap: Fix bounds checking in filemap_read()

2024-11-10T22:07:08+00:00

If the caller supplies an iocb->ki_pos value that is close to the filesystem upper limit, and an iterator with a count that causes us to overflow that limit, then filemap_read() enters an infinite loop. This behaviour was discovered when testing xfstests generic/525 with the "localio" optimisation for loopback NFS mounts. Reported-by: Mike Snitzer Fixes: c2a9737f45e2 ("vfs,mm: fix a dead loop in truncate_inode_pages_range()") Tested-by: Mike Snitzer Signed-off-by: Trond Myklebust Signed-off-by: Linus Torvalds

mm/filemap: fix filemap_get_folios_contig THP panic

2024-09-26T21:01:43+00:00

Patch series "memfd-pin huge page fixes". Fix multiple bugs that occur when using memfd_pin_folios with hugetlb pages and THP. The hugetlb bugs only bite when the page is not yet faulted in when memfd_pin_folios is called. The THP bug bites when the starting offset passed to memfd_pin_folios is not huge page aligned. See the commit messages for details. This patch (of 5): memfd_pin_folios on memory backed by THP panics if the requested start offset is not huge page aligned: BUG: kernel NULL pointer dereference, address: 0000000000000036 RIP: 0010:filemap_get_folios_contig+0xdf/0x290 RSP: 0018:ffffc9002092fbe8 EFLAGS: 00010202 RAX: 0000000000000002 RBX: 0000000000000002 RCX: 0000000000000002 The fault occurs here, because xas_load returns a folio with value 2: filemap_get_folios_contig() for (folio = xas_load(&xas); folio && xas.xa_index <= end; folio = xas_next(&xas)) { ... if (!folio_try_get(folio)) <-- BOOM "2" is an xarray sibling entry. We get it because memfd_pin_folios does not round the indices passed to filemap_get_folios_contig to huge page boundaries for THP, so we load from the middle of a huge page range see a sibling. (It does round for hugetlbfs, at the is_file_hugepages test). To fix, if the folio is a sibling, then return the next index as the starting point for the next call to filemap_get_folios_contig. Link: https://lkml.kernel.org/r/1725373521-451395-1-git-send-email-steven.sistare@oracle.com Link: https://lkml.kernel.org/r/1725373521-451395-2-git-send-email-steven.sistare@oracle.com Fixes: 89c1905d9c14 ("mm/gup: introduce memfd_pin_folios() for pinning memfd folios") Signed-off-by: Steve Sistare Cc: David Hildenbrand Cc: Jason Gunthorpe Cc: Matthew Wilcox Cc: Muchun Song Cc: Peter Xu Cc: Vivek Kasireddy Cc: Signed-off-by: Andrew Morton

Merge tag 'pull-stable-struct_fd' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2024-09-23T16:35:36+00:00

Pull 'struct fd' updates from Al Viro: "Just the 'struct fd' layout change, with conversion to accessor helpers" * tag 'pull-stable-struct_fd' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: add struct fd constructors, get rid of __to_fd() struct fd: representation change introduce fd_file(), convert all accessors to it.

Merge tag 'mm-stable-2024-09-20-02-31' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

2024-09-21T14:29:05+00:00

Pull MM updates from Andrew Morton: "Along with the usual shower of singleton patches, notable patch series in this pull request are: - "Align kvrealloc() with krealloc()" from Danilo Krummrich. Adds consistency to the APIs and behaviour of these two core allocation functions. This also simplifies/enables Rustification. - "Some cleanups for shmem" from Baolin Wang. No functional changes - mode code reuse, better function naming, logic simplifications. - "mm: some small page fault cleanups" from Josef Bacik. No functional changes - code cleanups only. - "Various memory tiering fixes" from Zi Yan. A small fix and a little cleanup. - "mm/swap: remove boilerplate" from Yu Zhao. Code cleanups and simplifications and .text shrinkage. - "Kernel stack usage histogram" from Pasha Tatashin and Shakeel Butt. This is a feature, it adds new feilds to /proc/vmstat such as $ grep kstack /proc/vmstat kstack_1k 3 kstack_2k 188 kstack_4k 11391 kstack_8k 243 kstack_16k 0 which tells us that 11391 processes used 4k of stack while none at all used 16k. Useful for some system tuning things, but partivularly useful for "the dynamic kernel stack project". - "kmemleak: support for percpu memory leak detect" from Pavel Tikhomirov. Teaches kmemleak to detect leaksage of percpu memory. - "mm: memcg: page counters optimizations" from Roman Gushchin. "3 independent small optimizations of page counters". - "mm: split PTE/PMD PT table Kconfig cleanups+clarifications" from David Hildenbrand. Improves PTE/PMD splitlock detection, makes powerpc/8xx work correctly by design rather than by accident. - "mm: remove arch_make_page_accessible()" from David Hildenbrand. Some folio conversions which make arch_make_page_accessible() unneeded. - "mm, memcg: cg2 memory{.swap,}.peak write handlers" fro David Finkel. Cleans up and fixes our handling of the resetting of the cgroup/process peak-memory-use detector. - "Make core VMA operations internal and testable" from Lorenzo Stoakes. Rationalizaion and encapsulation of the VMA manipulation APIs. With a view to better enable testing of the VMA functions, even from a userspace-only harness. - "mm: zswap: fixes for global shrinker" from Takero Funaki. Fix issues in the zswap global shrinker, resulting in improved performance. - "mm: print the promo watermark in zoneinfo" from Kaiyang Zhao. Fill in some missing info in /proc/zoneinfo. - "mm: replace follow_page() by folio_walk" from David Hildenbrand. Code cleanups and rationalizations (conversion to folio_walk()) resulting in the removal of follow_page(). - "improving dynamic zswap shrinker protection scheme" from Nhat Pham. Some tuning to improve zswap's dynamic shrinker. Significant reductions in swapin and improvements in performance are shown. - "mm: Fix several issues with unaccepted memory" from Kirill Shutemov. Improvements to the new unaccepted memory feature, - "mm/mprotect: Fix dax puds" from Peter Xu. Implements mprotect on DAX PUDs. This was missing, although nobody seems to have notied yet. - "Introduce a store type enum for the Maple tree" from Sidhartha Kumar. Cleanups and modest performance improvements for the maple tree library code. - "memcg: further decouple v1 code from v2" from Shakeel Butt. Move more cgroup v1 remnants away from the v2 memcg code. - "memcg: initiate deprecation of v1 features" from Shakeel Butt. Adds various warnings telling users that memcg v1 features are deprecated. - "mm: swap: mTHP swap allocator base on swap cluster order" from Chris Li. Greatly improves the success rate of the mTHP swap allocation. - "mm: introduce numa_memblks" from Mike Rapoport. Moves various disparate per-arch implementations of numa_memblk code into generic code. - "mm: batch free swaps for zap_pte_range()" from Barry Song. Greatly improves the performance of munmap() of swap-filled ptes. - "support large folio swap-out and swap-in for shmem" from Baolin Wang. With this series we no longer split shmem large folios into simgle-page folios when swapping out shmem. - "mm/hugetlb: alloc/free gigantic folios" from Yu Zhao. Nice performance improvements and code reductions for gigantic folios. - "support shmem mTHP collapse" from Baolin Wang. Adds support for khugepaged's collapsing of shmem mTHP folios. - "mm: Optimize mseal checks" from Pedro Falcato. Fixes an mprotect() performance regression due to the addition of mseal(). - "Increase the number of bits available in page_type" from Matthew Wilcox. Increases the number of bits available in page_type! - "Simplify the page flags a little" from Matthew Wilcox. Many legacy page flags are now folio flags, so the page-based flags and their accessors/mutators can be removed. - "mm: store zero pages to be swapped out in a bitmap" from Usama Arif. An optimization which permits us to avoid writing/reading zero-filled zswap pages to backing store. - "Avoid MAP_FIXED gap exposure" from Liam Howlett. Fixes a race window which occurs when a MAP_FIXED operqtion is occurring during an unrelated vma tree walk. - "mm: remove vma_merge()" from Lorenzo Stoakes. Major rotorooting of the vma_merge() functionality, making ot cleaner, more testable and better tested. - "misc fixups for DAMON {self,kunit} tests" from SeongJae Park. Minor fixups of DAMON selftests and kunit tests. - "mm: memory_hotplug: improve do_migrate_range()" from Kefeng Wang. Code cleanups and folio conversions. - "Shmem mTHP controls and stats improvements" from Ryan Roberts. Cleanups for shmem controls and stats. - "mm: count the number of anonymous THPs per size" from Barry Song. Expose additional anon THP stats to userspace for improved tuning. - "mm: finish isolate/putback_lru_page()" from Kefeng Wang: more folio conversions and removal of now-unused page-based APIs. - "replace per-quota region priorities histogram buffer with per-context one" from SeongJae Park. DAMON histogram rationalization. - "Docs/damon: update GitHub repo URLs and maintainer-profile" from SeongJae Park. DAMON documentation updates. - "mm/vdpa: correct misuse of non-direct-reclaim __GFP_NOFAIL and improve related doc and warn" from Jason Wang: fixes usage of page allocator __GFP_NOFAIL and GFP_ATOMIC flags. - "mm: split underused THPs" from Yu Zhao. Improve THP=always policy. This was overprovisioning THPs in sparsely accessed memory areas. - "zram: introduce custom comp backends API" frm Sergey Senozhatsky. Add support for zram run-time compression algorithm tuning. - "mm: Care about shadow stack guard gap when getting an unmapped area" from Mark Brown. Fix up the various arch_get_unmapped_area() implementations to better respect guard areas. - "Improve mem_cgroup_iter()" from Kinsey Ho. Improve the reliability of mem_cgroup_iter() and various code cleanups. - "mm: Support huge pfnmaps" from Peter Xu. Extends the usage of huge pfnmap support. - "resource: Fix region_intersects() vs add_memory_driver_managed()" from Huang Ying. Fix a bug in region_intersects() for systems with CXL memory. - "mm: hwpoison: two more poison recovery" from Kefeng Wang. Teaches a couple more code paths to correctly recover from the encountering of poisoned memry. - "mm: enable large folios swap-in support" from Barry Song. Support the swapin of mTHP memory into appropriately-sized folios, rather than into single-page folios" * tag 'mm-stable-2024-09-20-02-31' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (416 commits) zram: free secondary algorithms names uprobes: turn xol_area->pages[2] into xol_area->page uprobes: introduce the global struct vm_special_mapping xol_mapping Revert "uprobes: use vm_special_mapping close() functionality" mm: support large folios swap-in for sync io devices mm: add nr argument in mem_cgroup_swapin_uncharge_swap() helper to support large folios mm: fix swap_read_folio_zeromap() for large folios with partial zeromap mm/debug_vm_pgtable: Use pxdp_get() for accessing page table entries set_memory: add __must_check to generic stubs mm/vma: return the exact errno in vms_gather_munmap_vmas() memcg: cleanup with !CONFIG_MEMCG_V1 mm/show_mem.c: report alloc tags in human readable units mm: support poison recovery from copy_present_page() mm: support poison recovery from do_cow_fault() resource, kunit: add test case for region_intersects() resource: make alloc_free_mem_region() works for iomem_resource mm: z3fold: deprecate CONFIG_Z3FOLD vfio/pci: implement huge_fault support mm/arm64: support large pfn mappings mm/x86: support large pfn mappings ...