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

mm: folio_may_be_lru_cached() unless folio_test_large()

2025-10-02T11:44:11+00:00

[ Upstream commit 2da6de30e60dd9bb14600eff1cc99df2fa2ddae3 ] mm/swap.c and mm/mlock.c agree to drain any per-CPU batch as soon as a large folio is added: so collect_longterm_unpinnable_folios() just wastes effort when calling lru_add_drain[_all]() on a large folio. But although there is good reason not to batch up PMD-sized folios, we might well benefit from batching a small number of low-order mTHPs (though unclear how that "small number" limitation will be implemented). So ask if folio_may_be_lru_cached() rather than !folio_test_large(), to insulate those particular checks from future change. Name preferred to "folio_is_batchable" because large folios can well be put on a batch: it's just the per-CPU LRU caches, drained much later, which need care. Marked for stable, to counter the increase in lru_add_drain_all()s from "mm/gup: check ref_count instead of lru before migration". Link: https://lkml.kernel.org/r/57d2eaf8-3607-f318-e0c5-be02dce61ad0@google.com Fixes: 9a4e9f3b2d73 ("mm: update get_user_pages_longterm to migrate pages allocated from CMA region") Signed-off-by: Hugh Dickins Suggested-by: David Hildenbrand Acked-by: David Hildenbrand Cc: "Aneesh Kumar K.V" Cc: Axel Rasmussen Cc: Chris Li Cc: Christoph Hellwig Cc: Jason Gunthorpe Cc: Johannes Weiner Cc: John Hubbard Cc: Keir Fraser Cc: Konstantin Khlebnikov Cc: Li Zhe Cc: Matthew Wilcox (Oracle) Cc: Peter Xu Cc: Rik van Riel Cc: Shivank Garg Cc: Vlastimil Babka Cc: Wei Xu Cc: Will Deacon Cc: yangge Cc: Yuanchu Xie Cc: Yu Zhao Cc: Signed-off-by: Andrew Morton [ Clean cherry-pick now into this tree ] Signed-off-by: Hugh Dickins Signed-off-by: Sasha Levin

mm/mlock: set the correct prev on failure

2024-11-07T22:14:58+00:00

After commit 94d7d9233951 ("mm: abstract the vma_merge()/split_vma() pattern for mprotect() et al."), if vma_modify_flags() return error, the vma is set to an error code. This will lead to an invalid prev be returned. Generally this shouldn't matter as the caller should treat an error as indicating state is now invalidated, however unfortunately apply_mlockall_flags() does not check for errors and assumes that mlock_fixup() correctly maintains prev even if an error were to occur. This patch fixes that assumption. [lorenzo.stoakes@oracle.com: provide a better fix and rephrase the log] Link: https://lkml.kernel.org/r/20241027123321.19511-1-richard.weiyang@gmail.com Fixes: 94d7d9233951 ("mm: abstract the vma_merge()/split_vma() pattern for mprotect() et al.") Signed-off-by: Wei Yang Reviewed-by: Lorenzo Stoakes Reviewed-by: Liam R. Howlett Cc: Vlastimil Babka Cc: Jann Horn Cc: Signed-off-by: Andrew Morton

Merge tag 'random-6.11-rc1-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/crng/random

2024-07-24T17:29:50+00:00

Pull random number generator updates from Jason Donenfeld: "This adds getrandom() support to the vDSO. First, it adds a new kind of mapping to mmap(2), MAP_DROPPABLE, which lets the kernel zero out pages anytime under memory pressure, which enables allocating memory that never gets swapped to disk but also doesn't count as being mlocked. Then, the vDSO implementation of getrandom() is introduced in a generic manner and hooked into random.c. Next, this is implemented on x86. (Also, though it's not ready for this pull, somebody has begun an arm64 implementation already) Finally, two vDSO selftests are added. There are also two housekeeping cleanup commits" * tag 'random-6.11-rc1-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/crng/random: MAINTAINERS: add random.h headers to RNG subsection random: note that RNDGETPOOL was removed in 2.6.9-rc2 selftests/vDSO: add tests for vgetrandom x86: vdso: Wire up getrandom() vDSO implementation random: introduce generic vDSO getrandom() implementation mm: add MAP_DROPPABLE for designating always lazily freeable mappings

mm: add MAP_DROPPABLE for designating always lazily freeable mappings

2024-07-19T18:22:12+00:00

The vDSO getrandom() implementation works with a buffer allocated with a new system call that has certain requirements: - It shouldn't be written to core dumps. * Easy: VM_DONTDUMP. - It should be zeroed on fork. * Easy: VM_WIPEONFORK. - It shouldn't be written to swap. * Uh-oh: mlock is rlimited. * Uh-oh: mlock isn't inherited by forks. - It shouldn't reserve actual memory, but it also shouldn't crash when page faulting in memory if none is available * Uh-oh: VM_NORESERVE means segfaults. It turns out that the vDSO getrandom() function has three really nice characteristics that we can exploit to solve this problem: 1) Due to being wiped during fork(), the vDSO code is already robust to having the contents of the pages it reads zeroed out midway through the function's execution. 2) In the absolute worst case of whatever contingency we're coding for, we have the option to fallback to the getrandom() syscall, and everything is fine. 3) The buffers the function uses are only ever useful for a maximum of 60 seconds -- a sort of cache, rather than a long term allocation. These characteristics mean that we can introduce VM_DROPPABLE, which has the following semantics: a) It never is written out to swap. b) Under memory pressure, mm can just drop the pages (so that they're zero when read back again). c) It is inherited by fork. d) It doesn't count against the mlock budget, since nothing is locked. e) If there's not enough memory to service a page fault, it's not fatal, and no signal is sent. This way, allocations used by vDSO getrandom() can use: VM_DROPPABLE | VM_DONTDUMP | VM_WIPEONFORK | VM_NORESERVE And there will be no problem with OOMing, crashing on overcommitment, using memory when not in use, not wiping on fork(), coredumps, or writing out to swap. In order to let vDSO getrandom() use this, expose these via mmap(2) as MAP_DROPPABLE. Note that this involves removing the MADV_FREE special case from sort_folio(), which according to Yu Zhao is unnecessary and will simply result in an extra call to shrink_folio_list() in the worst case. The chunk removed reenables the swapbacked flag, which we don't want for VM_DROPPABLE, and we can't conditionalize it here because there isn't a vma reference available. Finally, the provided self test ensures that this is working as desired. Cc: linux-mm@kvack.org Acked-by: David Hildenbrand Signed-off-by: Jason A. Donenfeld

mm/mlock: implement folio_mlock_step() using folio_pte_batch()

2024-07-04T02:30:09+00:00

Let's make folio_mlock_step() simply a wrapper around folio_pte_batch(), which will greatly reduce the cost of ptep_get() when scanning a range of contptes. Link: https://lkml.kernel.org/r/20240611010418.70797-1-ioworker0@gmail.com Signed-off-by: Lance Yang Acked-by: David Hildenbrand Reviewed-by: Baolin Wang Suggested-by: Barry Song <21cnbao@gmail.com> Suggested-by: Matthew Wilcox Cc: Bang Li Cc: "Huang, Ying" Cc: Ryan Roberts Cc: Yin Fengwei Cc: Zi Yan Signed-off-by: Andrew Morton

mm: add pmd_folio()

2024-04-26T03:56:19+00:00

Convert directly from a pmd to a folio without going through another representation first. For now this is just a slightly shorter way to write it, but it might end up being more efficient later. Link: https://lkml.kernel.org/r/20240326202833.523759-4-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: David Hildenbrand Signed-off-by: Andrew Morton

mm: make folios_put() the basis of release_pages()

2024-03-05T01:01:22+00:00

Patch series "Rearrange batched folio freeing", v3. Other than the obvious "remove calls to compound_head" changes, the fundamental belief here is that iterating a linked list is much slower than iterating an array (5-15x slower in my testing). There's also an associated belief that since we iterate the batch of folios three times, we do better when the array is small (ie 15 entries) than we do with a batch that is hundreds of entries long, which only gives us the opportunity for the first pages to fall out of cache by the time we get to the end. It is possible we should increase the size of folio_batch. Hopefully the bots let us know if this introduces any performance regressions. This patch (of 3): By making release_pages() call folios_put(), we can get rid of the calls to compound_head() for the callers that already know they have folios. We can also get rid of the lock_batch tracking as we know the size of the batch is limited by folio_batch. This does reduce the maximum number of pages for which the lruvec lock is held, from SWAP_CLUSTER_MAX (32) to PAGEVEC_SIZE (15). I do not expect this to make a significant difference, but if it does, we can increase PAGEVEC_SIZE to 31. Link: https://lkml.kernel.org/r/20240227174254.710559-1-willy@infradead.org Link: https://lkml.kernel.org/r/20240227174254.710559-2-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) Cc: David Hildenbrand Cc: Mel Gorman Cc: Ryan Roberts Signed-off-by: Andrew Morton

mm: mlock: avoid folio_within_range() on KSM pages

2023-10-25T23:47:14+00:00

Since commit dc68badcede4 ("mm: mlock: update mlock_pte_range to handle large folio") I've just occasionally seen VM_WARN_ON_FOLIO(folio_test_ksm) warnings from folio_within_range(), in a splurge after testing with KSM hyperactive. folio_referenced_one()'s use of folio_within_vma() is safe because it checks folio_test_large() first; but allow_mlock_munlock() needs to do the same to avoid those warnings (or check !folio_test_ksm() itself? Or move either check into folio_within_range()? Hard to tell without more examples of its use). Link: https://lkml.kernel.org/r/23852f6a-5bfa-1ffd-30db-30c5560ad426@google.com Fixes: dc68badcede4 ("mm: mlock: update mlock_pte_range to handle large folio") Signed-off-by: Hugh Dickins Reviewed-by: Yin Fengwei Cc: Lorenzo Stoakes Cc: Matthew Wilcox (Oracle) Cc: Stefan Roesch Signed-off-by: Andrew Morton

mm: abstract the vma_merge()/split_vma() pattern for mprotect() et al.

2023-10-18T21:34:18+00:00

mprotect() and other functions which change VMA parameters over a range each employ a pattern of:- 1. Attempt to merge the range with adjacent VMAs. 2. If this fails, and the range spans a subset of the VMA, split it accordingly. This is open-coded and duplicated in each case. Also in each case most of the parameters passed to vma_merge() remain the same. Create a new function, vma_modify(), which abstracts this operation, accepting only those parameters which can be changed. To avoid the mess of invoking each function call with unnecessary parameters, create inline wrapper functions for each of the modify operations, parameterised only by what is required to perform the action. We can also significantly simplify the logic - by returning the VMA if we split (or merged VMA if we do not) we no longer need specific handling for merge/split cases in any of the call sites. Note that the userfaultfd_release() case works even though it does not split VMAs - since start is set to vma->vm_start and end is set to vma->vm_end, the split logic does not trigger. In addition, since we calculate pgoff to be equal to vma->vm_pgoff + (start - vma->vm_start) >> PAGE_SHIFT, and start - vma->vm_start will be 0 in this instance, this invocation will remain unchanged. We eliminate a VM_WARN_ON() in mprotect_fixup() as this simply asserts that vma_merge() correctly ensures that flags remain the same, something that is already checked in is_mergeable_vma() and elsewhere, and in any case is not specific to mprotect(). Link: https://lkml.kernel.org/r/0dfa9368f37199a423674bf0ee312e8ea0619044.1697043508.git.lstoakes@gmail.com Signed-off-by: Lorenzo Stoakes Reviewed-by: Vlastimil Babka Cc: Alexander Viro Cc: Christian Brauner Cc: Liam R. Howlett Signed-off-by: Andrew Morton

mm: mlock: update mlock_pte_range to handle large folio

2023-10-04T17:32:32+00:00

Current kernel only lock base size folio during mlock syscall. Add large folio support with following rules: - Only mlock large folio when it's in VM_LOCKED VMA range and fully mapped to page table. fully mapped folio is required as if folio is not fully mapped to a VM_LOCKED VMA, if system is in memory pressure, page reclaim is allowed to pick up this folio, split it and reclaim the pages which are not in VM_LOCKED VMA. - munlock will apply to the large folio which is in VMA range or cross the VMA boundary. This is required to handle the case that the large folio is mlocked, later the VMA is split in the middle of large folio. Link: https://lkml.kernel.org/r/20230918073318.1181104-4-fengwei.yin@intel.com Signed-off-by: Yin Fengwei Cc: David Hildenbrand Cc: Hugh Dickins Cc: Matthew Wilcox (Oracle) Cc: Ryan Roberts Cc: Yang Shi Cc: Yosry Ahmed Cc: Yu Zhao Signed-off-by: Andrew Morton