- 13 May, 2022 40 commits
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Peter Xu authored
We used to have USERFAULTFD configs stored in init/. It makes sense as a start because that's the default place for storing syscall related configs. However userfaultfd evolved a bit in the past few years and some more config options were added. They're no longer related to syscalls and start to be not suitable to be kept in the init/ directory anymore, because they're pure mm concepts. But it's not ideal either to keep the userfaultfd configs separate from each other. Hence this patch moves the userfaultfd configs under init/ to be under mm/ so that we'll start to group all userfaultfd configs together. We do have quite a few examples of syscall related configs that are not put under init/Kconfig: FTRACE_SYSCALLS, SWAP, FILE_LOCKING, MEMFD_CREATE.. They all reside in the dir where they're more suitable for the concept. So it seems there's no restriction to keep the role of having syscall related CONFIG_* under init/ only. Link: https://lkml.kernel.org/r/20220420144823.35277-1-peterx@redhat.comSigned-off-by:
Peter Xu <peterx@redhat.com> Suggested-by:
Johannes Weiner <hannes@cmpxchg.org> Acked-by:
Axel Rasmussen <axelrasmussen@google.com> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org>
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Guo Zhengkui authored
Address the following coccicheck warning: tools/testing/selftests/vm/userfaultfd.c:1536:21-22: WARNING opportunity for swap(). tools/testing/selftests/vm/userfaultfd.c:1540:33-34: WARNING opportunity for swap(). by using swap() for the swapping of variable values and drop `tmp_area` that is not needed any more. `swap()` macro in userfaultfd.c is introduced in commit 68169686 ("selftests: vm: remove dependecy from internal kernel macros") It has been tested with gcc (Debian 8.3.0-6) 8.3.0. Link: https://lkml.kernel.org/r/20220407123141.4998-1-guozhengkui@vivo.comSigned-off-by:
Guo Zhengkui <guozhengkui@vivo.com> Reviewed-by:
Muchun Song <songmuchun@bytedance.com> Reviewed-by:
Shuah Khan <skhan@linuxfoundation.org> Signed-off-by:
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Peter Xu authored
After we added support for shmem and hugetlbfs, we can turn uffd-wp test on always now. Link: https://lkml.kernel.org/r/20220405014932.15212-1-peterx@redhat.comSigned-off-by:
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Peter Xu authored
Enable PTE markers by default. On x86_64 it means it'll auto-enable PTE_MARKER_UFFD_WP as well. [peterx@redhat.com: hide PTE_MARKER option] Link: https://lkml.kernel.org/r/20220419202531.27415-1-peterx@redhat.com Link: https://lkml.kernel.org/r/20220405014929.15158-1-peterx@redhat.comSigned-off-by:
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Peter Xu authored
We've had all the necessary changes ready for both shmem and hugetlbfs. Turn on all the shmem/hugetlbfs switches for userfaultfd-wp. We can expand UFFD_API_RANGE_IOCTLS_BASIC with _UFFDIO_WRITEPROTECT too because all existing types now support write protection mode. Since vma_can_userfault() will be used elsewhere, move into userfaultfd_k.h. Link: https://lkml.kernel.org/r/20220405014926.15101-1-peterx@redhat.comSigned-off-by:
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Peter Xu authored
This requires the pagemap code to be able to recognize the newly introduced swap special pte for uffd-wp, meanwhile the general case for hugetlb that we recently start to support. It should make pagemap uffd-wp support complete. Link: https://lkml.kernel.org/r/20220405014923.15047-1-peterx@redhat.comSigned-off-by:
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Peter Xu authored
When we're trying to collapse a 2M huge shmem page, don't retract pgtable pmd page if it's registered with uffd-wp, because that pgtable could have pte markers installed. Recycling of that pgtable means we'll lose the pte markers. That could cause data loss for an uffd-wp enabled application on shmem. Instead of disabling khugepaged on these files, simply skip retracting these special VMAs, then the page cache can still be merged into a huge thp, and other mm/vma can still map the range of file with a huge thp when proper. Note that checking VM_UFFD_WP needs to be done with mmap_sem held for write, that avoids race like: khugepaged user thread ========== =========== check VM_UFFD_WP, not set UFFDIO_REGISTER with uffd-wp on shmem wr-protect some pages (install markers) take mmap_sem write lock erase pmd and free pmd page --> pte markers are dropped unnoticed! Link: https://lkml.kernel.org/r/20220405014921.14994-1-peterx@redhat.comSigned-off-by: -
Peter Xu authored
Firstly, we'll need to pass in dst_vma into copy_hugetlb_page_range() because for uffd-wp it's the dst vma that matters on deciding how we should treat uffd-wp protected ptes. We should recognize pte markers during fork and do the pte copy if needed. [lkp@intel.com: vma_needs_copy can be static] Link: https://lkml.kernel.org/r/Ylb0CGeFJlc4EzLk@7ec4ff11d4ae Link: https://lkml.kernel.org/r/20220405014918.14932-1-peterx@redhat.comSigned-off-by:
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Peter Xu authored
As with shmem uffd-wp special ptes, only drop the uffd-wp special swap pte if unmapping an entire vma or synchronized such that faults can not race with the unmap operation. This requires passing zap_flags all the way to the lowest level hugetlb unmap routine: __unmap_hugepage_range. In general, unmap calls originated in hugetlbfs code will pass the ZAP_FLAG_DROP_MARKER flag as synchronization is in place to prevent faults. The exception is hole punch which will first unmap without any synchronization. Later when hole punch actually removes the page from the file, it will check to see if there was a subsequent fault and if so take the hugetlb fault mutex while unmapping again. This second unmap will pass in ZAP_FLAG_DROP_MARKER. The justification of "whether to apply ZAP_FLAG_DROP_MARKER flag when unmap a hugetlb range" is (IMHO): we should never reach a state when a page fault could errornously fault in a page-cache page that was wr-protected to be writable, even in an extremely short period. That could happen if e.g. we pass ZAP_FLAG_DROP_MARKER when hugetlbfs_punch_hole() calls hugetlb_vmdelete_list(), because if a page faults after that call and before remove_inode_hugepages() is executed, the page cache can be mapped writable again in the small racy window, that can cause unexpected data overwritten. [peterx@redhat.com: fix sparse warning] Link: https://lkml.kernel.org/r/Ylcdw8I1L5iAoWhb@xz-m1.local [akpm@linux-foundation.org: move zap_flags_t from mm.h to mm_types.h to fix build issues] Link: https://lkml.kernel.org/r/20220405014915.14873-1-peterx@redhat.comSigned-off-by:
Mike Kravetz <mike.kravetz@oracle.com> Cc: Alistair Popple <apopple@nvidia.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Axel Rasmussen <axelrasmussen@google.com> Cc: David Hildenbrand <david@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Jerome Glisse <jglisse@redhat.com> Cc: "Kirill A . Shutemov" <kirill@shutemov.name> Cc: Matthew Wilcox <willy@infradead.org> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Nadav Amit <nadav.amit@gmail.com> Signed-off-by:
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Peter Xu authored
Teach hugetlbfs code to wr-protect none ptes just in case the page cache existed for that pte. Meanwhile we also need to be able to recognize a uffd-wp marker pte and remove it for uffd_wp_resolve. Since at it, introduce a variable "psize" to replace all references to the huge page size fetcher. Link: https://lkml.kernel.org/r/20220405014912.14815-1-peterx@redhat.comSigned-off-by:
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Peter Xu authored
Allow hugetlb code to handle pte markers just like none ptes. It's mostly there, we just need to make sure we don't assume hugetlb_no_page() only handles none pte, so when detecting pte change we should use pte_same() rather than pte_none(). We need to pass in the old_pte to do the comparison. Check the original pte to see whether it's a pte marker, if it is, we should recover uffd-wp bit on the new pte to be installed, so that the next write will be trapped by uffd. Link: https://lkml.kernel.org/r/20220405014909.14761-1-peterx@redhat.comSigned-off-by:
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Peter Xu authored
This starts from passing cp_flags into hugetlb_change_protection() so hugetlb will be able to handle MM_CP_UFFD_WP[_RESOLVE] requests. huge_pte_clear_uffd_wp() is introduced to handle the case where the UFFDIO_WRITEPROTECT is requested upon migrating huge page entries. Link: https://lkml.kernel.org/r/20220405014906.14708-1-peterx@redhat.comSigned-off-by:
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Peter Xu authored
Pass the wp_copy variable into hugetlb_mcopy_atomic_pte() thoughout the stack. Apply the UFFD_WP bit if UFFDIO_COPY_MODE_WP is with UFFDIO_COPY. Hugetlb pages are only managed by hugetlbfs, so we're safe even without setting dirty bit in the huge pte if the page is installed as read-only. However we'd better still keep the dirty bit set for a read-only UFFDIO_COPY pte (when UFFDIO_COPY_MODE_WP bit is set), not only to match what we do with shmem, but also because the page does contain dirty data that the kernel just copied from the userspace. Link: https://lkml.kernel.org/r/20220405014904.14643-1-peterx@redhat.comSigned-off-by:
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Peter Xu authored
Hook up hugetlbfs_fault() with the capability to handle userfaultfd-wp faults. We do this slightly earlier than hugetlb_cow() so that we can avoid taking some extra locks that we definitely don't need. Link: https://lkml.kernel.org/r/20220405014901.14590-1-peterx@redhat.comSigned-off-by:
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Peter Xu authored
They will be used in the follow up patches to either check/set/clear uffd-wp bit of a huge pte. So far it reuses all the small pte helpers. Archs can overwrite these versions when necessary (with __HAVE_ARCH_HUGE_PTE_UFFD_WP* macros) in the future. Link: https://lkml.kernel.org/r/20220405014858.14531-1-peterx@redhat.comSigned-off-by:
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Peter Xu authored
Normally we skip copy page when fork() for VM_SHARED shmem, but we can't skip it anymore if uffd-wp is enabled on dst vma. This should only happen when the src uffd has UFFD_FEATURE_EVENT_FORK enabled on uffd-wp shmem vma, so that VM_UFFD_WP will be propagated onto dst vma too, then we should copy the pgtables with uffd-wp bit and pte markers, because these information will be lost otherwise. Since the condition checks will become even more complicated for deciding "whether a vma needs to copy the pgtable during fork()", introduce a helper vma_needs_copy() for it, so everything will be clearer. Link: https://lkml.kernel.org/r/20220405014855.14468-1-peterx@redhat.comSigned-off-by:
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Peter Xu authored
We don't have "huge" version of pte markers, instead when necessary we split the thp. However split the thp is not enough, because file-backed thp is handled totally differently comparing to anonymous thps: rather than doing a real split, the thp pmd will simply got cleared in __split_huge_pmd_locked(). That is not enough if e.g. when there is a thp covers range [0, 2M) but we want to wr-protect small page resides in [4K, 8K) range, because after __split_huge_pmd() returns, there will be a none pmd, and change_pmd_range() will just skip it right after the split. Here we leverage the previously introduced change_pmd_prepare() macro so that we'll populate the pmd with a pgtable page after the pmd split (in which process the pmd will be cleared for cases like shmem). Then change_pte_range() will do all the rest for us by installing the uffd-wp pte marker at any none pte that we'd like to wr-protect. Link: https://lkml.kernel.org/r/20220405014852.14413-1-peterx@redhat.comSigned-off-by:
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Peter Xu authored
File-backed memory differs from anonymous memory in that even if the pte is missing, the data could still resides either in the file or in page/swap cache. So when wr-protect a pte, we need to consider none ptes too. We do that by installing the uffd-wp pte markers when necessary. So when there's a future write to the pte, the fault handler will go the special path to first fault-in the page as read-only, then report to userfaultfd server with the wr-protect message. On the other hand, when unprotecting a page, it's also possible that the pte got unmapped but replaced by the special uffd-wp marker. Then we'll need to be able to recover from a uffd-wp pte marker into a none pte, so that the next access to the page will fault in correctly as usual when accessed the next time. Special care needs to be taken throughout the change_protection_range() process. Since now we allow user to wr-protect a none pte, we need to be able to pre-populate the page table entries if we see (!anonymous && MM_CP_UFFD_WP) requests, otherwise change_protection_range() will always skip when the pgtable entry does not exist. For example, the pgtable can be missing for a whole chunk of 2M pmd, but the page cache can exist for the 2M range. When we want to wr-protect one 4K page within the 2M pmd range, we need to pre-populate the pgtable and install the pte marker showing that we want to get a message and block the thread when the page cache of that 4K page is written. Without pre-populating the pmd, change_protection() will simply skip that whole pmd. Note that this patch only covers the small pages (pte level) but not covering any of the transparent huge pages yet. That will be done later, and this patch will be a preparation for it too. Link: https://lkml.kernel.org/r/20220405014850.14352-1-peterx@redhat.comSigned-off-by:
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Peter Xu authored
File-backed memory is prone to being unmapped at any time. It means all information in the pte will be dropped, including the uffd-wp flag. To persist the uffd-wp flag, we'll use the pte markers. This patch teaches the zap code to understand uffd-wp and know when to keep or drop the uffd-wp bit. Add a new flag ZAP_FLAG_DROP_MARKER and set it in zap_details when we don't want to persist such an information, for example, when destroying the whole vma, or punching a hole in a shmem file. For the rest cases we should never drop the uffd-wp bit, or the wr-protect information will get lost. The new ZAP_FLAG_DROP_MARKER needs to be put into mm.h rather than memory.c because it'll be further referenced in hugetlb files later. Link: https://lkml.kernel.org/r/20220405014847.14295-1-peterx@redhat.comSigned-off-by:
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Peter Xu authored
File-backed memories are prone to unmap/swap so the ptes are always unstable, because they can be easily faulted back later using the page cache. This could lead to uffd-wp getting lost when unmapping or swapping out such memory. One example is shmem. PTE markers are needed to store those information. This patch prepares it by handling uffd-wp pte markers first it is applied elsewhere, so that the page fault handler can recognize uffd-wp pte markers. The handling of uffd-wp pte markers is similar to missing fault, it's just that we'll handle this "missing fault" when we see the pte markers, meanwhile we need to make sure the marker information is kept during processing the fault. This is a slow path of uffd-wp handling, because zapping of wr-protected shmem ptes should be rare. So far it should only trigger in two conditions: (1) When trying to punch holes in shmem_fallocate(), there is an optimization to zap the pgtables before evicting the page. (2) When swapping out shmem pages. Because of this, the page fault handling is simplifed too by not sending the wr-protect message in the 1st page fault, instead the page will be installed read-only, so the uffd-wp message will be generated in the next fault, which will trigger the do_wp_page() path of general uffd-wp handling. Disable fault-around for all uffd-wp registered ranges for extra safety just like uffd-minor fault, and clean the code up. Link: https://lkml.kernel.org/r/20220405014844.14239-1-peterx@redhat.comSigned-off-by: -
Peter Xu authored
Pass wp_copy into shmem_mfill_atomic_pte() through the stack, then apply the UFFD_WP bit properly when the UFFDIO_COPY on shmem is with UFFDIO_COPY_MODE_WP. wp_copy lands mfill_atomic_install_pte() finally. Note: we must do pte_wrprotect() if !writable in mfill_atomic_install_pte(), as mk_pte() could return a writable pte (e.g., when VM_SHARED on a shmem file). Link: https://lkml.kernel.org/r/20220405014841.14185-1-peterx@redhat.comSigned-off-by:
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Peter Xu authored
This patch introduces the 1st user of pte marker: the uffd-wp marker. When the pte marker is installed with the uffd-wp bit set, it means this pte was wr-protected by uffd. We will use this special pte to arm the ptes that got either unmapped or swapped out for a file-backed region that was previously wr-protected. This special pte could trigger a page fault just like swap entries. This idea is greatly inspired by Hugh and Andrea in the discussion, which is referenced in the links below. Some helpers are introduced to detect whether a swap pte is uffd wr-protected. After the pte marker introduced, one swap pte can be wr-protected in two forms: either it is a normal swap pte and it has _PAGE_SWP_UFFD_WP set, or it's a pte marker that has PTE_MARKER_UFFD_WP set. [peterx@redhat.com: fixup] Link: https://lkml.kernel.org/r/YkzKiM8tI4+qOfXF@xz-m1.local Link: https://lore.kernel.org/lkml/20201126222359.8120-1-peterx@redhat.com/ Link: https://lore.kernel.org/lkml/20201130230603.46187-1-peterx@redhat.com/ Link: https://lkml.kernel.org/r/20220405014838.14131-1-peterx@redhat.comSigned-off-by:
Andrea Arcangeli <aarcange@redhat.com> Suggested-by:
Hugh Dickins <hughd@google.com> Cc: Alistair Popple <apopple@nvidia.com> Cc: Axel Rasmussen <axelrasmussen@google.com> Cc: David Hildenbrand <david@redhat.com> Cc: Jerome Glisse <jglisse@redhat.com> Cc: "Kirill A . Shutemov" <kirill@shutemov.name> Cc: Matthew Wilcox <willy@infradead.org> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Nadav Amit <nadav.amit@gmail.com> Signed-off-by:
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Peter Xu authored
This patch allows do_fault() to trigger on !pte_none() cases too. This prepares for the pte markers to be handled by do_fault() just like none pte. To achieve this, instead of unconditionally check against pte_none() in finish_fault(), we may hit the case that the orig_pte was some pte marker so what we want to do is to replace the pte marker with some valid pte entry. Then if orig_pte was set we'd want to check the current *pte (under pgtable lock) against orig_pte rather than none pte. Right now there's no solid way to safely reference orig_pte because when pmd is not allocated handle_pte_fault() will not initialize orig_pte, so it's not safe to reference it. There's another solution proposed before this patch to do pte_clear() for vmf->orig_pte for pmd==NULL case, however it turns out it'll break arm32 because arm32 could have assumption that pte_t* pointer will always reside on a real ram32 pgtable, not any kernel stack variable. To solve this, we add a new flag FAULT_FLAG_ORIG_PTE_VALID, and it'll be set along with orig_pte when there is valid orig_pte, or it'll be cleared when orig_pte was not initialized. It'll be updated every time we call handle_pte_fault(), so e.g. if a page fault retry happened it'll be properly updated along with orig_pte. [1] https://lore.kernel.org/lkml/710c48c9-406d-e4c5-a394-10501b951316@samsung.com/ [akpm@linux-foundation.org: coding-style cleanups] [peterx@redhat.com: fix crash reported by Marek] Link: https://lkml.kernel.org/r/Ylb9rXJyPm8/ao8f@xz-m1.local Link: https://lkml.kernel.org/r/20220405014836.14077-1-peterx@redhat.comSigned-off-by:
Alistair Popple <apopple@nvidia.com> Tested-by:
Marek Szyprowski <m.szyprowski@samsung.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Axel Rasmussen <axelrasmussen@google.com> Cc: David Hildenbrand <david@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Jerome Glisse <jglisse@redhat.com> Cc: "Kirill A . Shutemov" <kirill@shutemov.name> Cc: Matthew Wilcox <willy@infradead.org> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Nadav Amit <nadav.amit@gmail.com> Signed-off-by:
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Peter Xu authored
This patch still does not use pte marker in any way, however it teaches the core mm about the pte marker idea. For example, handle_pte_marker() is introduced that will parse and handle all the pte marker faults. Many of the places are more about commenting it up - so that we know there's the possibility of pte marker showing up, and why we don't need special code for the cases. [peterx@redhat.com: userfaultfd.c needs swapops.h] Link: https://lkml.kernel.org/r/YmRlVj3cdizYJsr0@xz-m1.local Link: https://lkml.kernel.org/r/20220405014833.14015-1-peterx@redhat.comSigned-off-by:
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Peter Xu authored
Patch series "userfaultfd-wp: Support shmem and hugetlbfs", v8. Overview ======== Userfaultfd-wp anonymous support was merged two years ago. There're quite a few applications that started to leverage this capability either to take snapshots for user-app memory, or use it for full user controled swapping. This series tries to complete the feature for uffd-wp so as to cover all the RAM-based memory types. So far uffd-wp is the only missing piece of the rest features (uffd-missing & uffd-minor mode). One major reason to do so is that anonymous pages are sometimes not satisfying the need of applications, and there're growing users of either shmem and hugetlbfs for either sharing purpose (e.g., sharing guest mem between hypervisor process and device emulation process, shmem local live migration for upgrades), or for performance on tlb hits. All these mean that if a uffd-wp app wants to switch to any of the memory types, it'll stop working. I think it's worthwhile to have the kernel to cover all these aspects. This series chose to protect pages in pte level not page level. One major reason is safety. I have no idea how we could make it safe if any of the uffd-privileged app can wr-protect a page that any other application can use. It means this app can block any process potentially for any time it wants. The other reason is that it aligns very well with not only the anonymous uffd-wp solution, but also uffd as a whole. For example, userfaultfd is implemented fundamentally based on VMAs. We set flags to VMAs showing the status of uffd tracking. For another per-page based protection solution, it'll be crossing the fundation line on VMA-based, and it could simply be too far away already from what's called userfaultfd. PTE markers =========== The patchset is based on the idea called PTE markers. It was discussed in one of the mm alignment sessions, proposed starting from v6, and this is the 2nd version of it using PTE marker idea. PTE marker is a new type of swap entry that is ony applicable to file backed memories like shmem and hugetlbfs. It's used to persist some pte-level information even if the original present ptes in pgtable are zapped. Logically pte markers can store more than uffd-wp information, but so far only one bit is used for uffd-wp purpose. When the pte marker is installed with uffd-wp bit set, it means this pte is wr-protected by uffd. It solves the problem on e.g. file-backed memory mapped ptes got zapped due to any reason (e.g. thp split, or swapped out), we can still keep the wr-protect information in the ptes. Then when the page fault triggers again, we'll know this pte is wr-protected so we can treat the pte the same as a normal uffd wr-protected pte. The extra information is encoded into the swap entry, or swp_offset to be explicit, with the swp_type being PTE_MARKER. So far uffd-wp only uses one bit out of the swap entry, the rest bits of swp_offset are still reserved for other purposes. There're two configs to enable/disable PTE markers: CONFIG_PTE_MARKER CONFIG_PTE_MARKER_UFFD_WP We can set !PTE_MARKER to completely disable all the PTE markers, along with uffd-wp support. I made two config so we can also enable PTE marker but disable uffd-wp file-backed for other purposes. At the end of current series, I'll enable CONFIG_PTE_MARKER by default, but that patch is standalone and if anyone worries about having it by default, we can also consider turn it off by dropping that oneliner patch. So far I don't see a huge risk of doing so, so I kept that patch. In most cases, PTE markers should be treated as none ptes. It is because that unlike most of the other swap entry types, there's no PFN or block offset information encoded into PTE markers but some extra well-defined bits showing the status of the pte. These bits should only be used as extra data when servicing an upcoming page fault, and then we behave as if it's a none pte. I did spend a lot of time observing all the pte_none() users this time. It is indeed a challenge because there're a lot, and I hope I didn't miss a single of them when we should take care of pte markers. Luckily, I don't think it'll need to be considered in many cases, for example: boot code, arch code (especially non-x86), kernel-only page handlings (e.g. CPA), or device driver codes when we're tackling with pure PFN mappings. I introduced pte_none_mostly() in this series when we need to handle pte markers the same as none pte, the "mostly" is the other way to write "either none pte or a pte marker". I didn't replace pte_none() to cover pte markers for below reasons: - Very rare case of pte_none() callers will handle pte markers. E.g., all the kernel pages do not require knowledge of pte markers. So we don't pollute the major use cases. - Unconditionally change pte_none() semantics could confuse people, because pte_none() existed for so long a time. - Unconditionally change pte_none() semantics could make pte_none() slower even if in many cases pte markers do not exist. - There're cases where we'd like to handle pte markers differntly from pte_none(), so a full replace is also impossible. E.g. khugepaged should still treat pte markers as normal swap ptes rather than none ptes, because pte markers will always need a fault-in to merge the marker with a valid pte. Or the smap code will need to parse PTE markers not none ptes. Patch Layout ============ Introducing PTE marker and uffd-wp bit in PTE marker: mm: Introduce PTE_MARKER swap entry mm: Teach core mm about pte markers mm: Check against orig_pte for finish_fault() mm/uffd: PTE_MARKER_UFFD_WP Adding support for shmem uffd-wp: mm/shmem: Take care of UFFDIO_COPY_MODE_WP mm/shmem: Handle uffd-wp special pte in page fault handler mm/shmem: Persist uffd-wp bit across zapping for file-backed mm/shmem: Allow uffd wr-protect none pte for file-backed mem mm/shmem: Allows file-back mem to be uffd wr-protected on thps mm/shmem: Handle uffd-wp during fork() Adding support for hugetlbfs uffd-wp: mm/hugetlb: Introduce huge pte version of uffd-wp helpers mm/hugetlb: Hook page faults for uffd write protection mm/hugetlb: Take care of UFFDIO_COPY_MODE_WP mm/hugetlb: Handle UFFDIO_WRITEPROTECT mm/hugetlb: Handle pte markers in page faults mm/hugetlb: Allow uffd wr-protect none ptes mm/hugetlb: Only drop uffd-wp special pte if required mm/hugetlb: Handle uffd-wp during fork() Misc handling on the rest mm for uffd-wp file-backed: mm/khugepaged: Don't recycle vma pgtable if uffd-wp registered mm/pagemap: Recognize uffd-wp bit for shmem/hugetlbfs Enabling of uffd-wp on file-backed memory: mm/uffd: Enable write protection for shmem & hugetlbfs mm: Enable PTE markers by default selftests/uffd: Enable uffd-wp for shmem/hugetlbfs Tests ===== - Compile test on x86_64 and aarch64 on different configs - Kernel selftests - uffd-test [0] - Umapsort [1,2] test for shmem/hugetlb, with swap on/off [0] https://github.com/xzpeter/clibs/tree/master/uffd-test [1] https://github.com/xzpeter/umap-apps/tree/peter [2] https://github.com/xzpeter/umap/tree/peter-shmem-hugetlbfs This patch (of 23): Introduces a new swap entry type called PTE_MARKER. It can be installed for any pte that maps a file-backed memory when the pte is temporarily zapped, so as to maintain per-pte information. The information that kept in the pte is called a "marker". Here we define the marker as "unsigned long" just to match pgoff_t, however it will only work if it still fits in swp_offset(), which is e.g. currently 58 bits on x86_64. A new config CONFIG_PTE_MARKER is introduced too; it's by default off. A bunch of helpers are defined altogether to service the rest of the pte marker code. [peterx@redhat.com: fixup] Link: https://lkml.kernel.org/r/Yk2rdB7SXZf+2BDF@xz-m1.local Link: https://lkml.kernel.org/r/20220405014646.13522-1-peterx@redhat.com Link: https://lkml.kernel.org/r/20220405014646.13522-2-peterx@redhat.comSigned-off-by: -
Wonhyuk Yang authored
To spread dirty pages, nodes are checked whether they have reached the dirty limit using the expensive node_dirty_ok(). To reduce the frequency of calling node_dirty_ok(), the last node that hit the dirty limit can be cached. Instead of caching the node, caching both the node and its node_dirty_ok() status can reduce the number of calle to node_dirty_ok(). [akpm@linux-foundation.org: rename last_pgdat_dirty_limit to last_pgdat_dirty_ok] Link: https://lkml.kernel.org/r/20220430011032.64071-1-vvghjk1234@gmail.comSigned-off-by:
Wonhyuk Yang <vvghjk1234@gmail.com> Acked-by:
Mel Gorman <mgorman@suse.de> Cc: Donghyeok Kim <dthex5d@gmail.com> Cc: JaeSang Yoo <jsyoo5b@gmail.com> Cc: Jiyoup Kim <lakroforce@gmail.com> Cc: Ohhoon Kwon <ohkwon1043@gmail.com> Signed-off-by:
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SeongJae Park authored
This commit documents the new DAMON_RECLAIM parameter, 'commit_inputs' in its usage document. Link: https://lkml.kernel.org/r/20220429160606.127307-15-sj@kernel.orgSigned-off-by:
SeongJae Park <sj@kernel.org> Signed-off-by:
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SeongJae Park authored
DAMON_RECLAIM reads the user input parameters only when it starts. To allow more efficient online tuning, this commit implements a new input parameter called 'commit_inputs'. Writing true to the parameter makes DAMON_RECLAIM reads the input parameters again. Link: https://lkml.kernel.org/r/20220429160606.127307-14-sj@kernel.orgSigned-off-by:
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SeongJae Park authored
This commit documents the newly added 'state' sysfs file input keyword, 'commit', which allows online tuning of DAMON contexts. Link: https://lkml.kernel.org/r/20220429160606.127307-13-sj@kernel.orgSigned-off-by:
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SeongJae Park authored
Currently, DAMON sysfs interface doesn't provide a way for adjusting DAMON input parameters while it is turned on. Therefore, users who want to reconfigure DAMON need to stop DAMON and restart. This means all the monitoring results that accumulated so far, which could be useful, should be flushed. This would be inefficient for many cases. For an example, let's suppose a sysadmin was running a DAMON-based Operation Scheme to find memory regions not accessed for more than 5 mins and page out the regions. If it turns out the 5 mins threshold was too long and therefore the sysadmin wants to reduce it to 4 mins, the sysadmin should turn off DAMON, restart it, and wait for at least 4 more minutes so that DAMON can find the cold memory regions, even though DAMON was knowing there are regions that not accessed for 4 mins at the time of shutdown. This commit makes DAMON sysfs interface to support online DAMON input parameters updates by adding a new input keyword for the 'state' DAMON sysfs file, 'commit'. Writing the keyword to the 'state' file while the corresponding kdamond is running makes the kdamond to read the sysfs file values again and update the DAMON context. Link: https://lkml.kernel.org/r/20220429160606.127307-12-sj@kernel.orgSigned-off-by:
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SeongJae Park authored
Only '->kdamond' and '->kdamond_stop' are protected by 'kdamond_lock' of 'struct damon_ctx'. All other DAMON context internal data items are recommended to be accessed in DAMON callbacks, or under some additional synchronizations. But, DAMON sysfs is accessing the schemes stat under 'kdamond_lock'. It makes no big issue as the read values are not used anywhere inside kernel, but would better to be fixed. This commit moves the reads to DAMON callback context, as supposed to be used for the purpose. Link: https://lkml.kernel.org/r/20220429160606.127307-11-sj@kernel.orgSigned-off-by:
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SeongJae Park authored
DAMON sysfs 'state' file handling code is using string literals in both 'state_show()' and 'state_store()'. This makes the code error prone and inflexible for future extensions. To improve the situation, this commit defines possible input strings and 'enum' for identifying each input keyword only once, and refactors the code to reuse those. Link: https://lkml.kernel.org/r/20220429160606.127307-10-sj@kernel.orgSigned-off-by:
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SeongJae Park authored
'damon_set_regions()' is general enough so that it can also be used for only creating regions. This commit makes DAMON sysfs interface to reuse the function rather keeping two implementations for a same purpose. Link: https://lkml.kernel.org/r/20220429160606.127307-9-sj@kernel.orgSigned-off-by:
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SeongJae Park authored
This commit separates DAMON sysfs interface's monitoring context targets setup code to a new function for better readability. Link: https://lkml.kernel.org/r/20220429160606.127307-8-sj@kernel.orgSigned-off-by:
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SeongJae Park authored
Having multiple targets for physical address space monitoring makes no sense. This commit prohibits such a ridiculous DAMON context setup my making the DAMON context build function to check and return an error for the case. Link: https://lkml.kernel.org/r/20220429160606.127307-7-sj@kernel.orgSigned-off-by:
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SeongJae Park authored
'damon_va_apply_three_regions()' is just a wrapper of its general version, 'damon_set_regions()'. This commit replaces the wrapper calls to directly call the general version. Link: https://lkml.kernel.org/r/20220429160606.127307-6-sj@kernel.orgSigned-off-by:
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SeongJae Park authored
This commit moves 'damon_set_regions()' from vaddr to core, as it is aimed to be used by not only 'vaddr' but also other parts of DAMON. Link: https://lkml.kernel.org/r/20220429160606.127307-5-sj@kernel.orgSigned-off-by:
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SeongJae Park authored
'damon_va_apply_three_regions()' is for adjusting address ranges to fit in three discontiguous ranges. The function can be generalized for arbitrary number of discontiguous ranges and reused for future usage, such as arbitrary online regions update. For such future usage, this commit introduces a generalized version of the function called 'damon_set_regions()'. Link: https://lkml.kernel.org/r/20220429160606.127307-4-sj@kernel.orgSigned-off-by:
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SeongJae Park authored
When 'after_sampling()' or 'after_aggregation()' DAMON callbacks return an error, kdamond continues the remaining loop once. It makes no much sense to run the remaining part while something wrong already happened. The context might be corrupted or having invalid data. This commit therefore makes kdamond skips the remaining works and immediately finish in the cases. Link: https://lkml.kernel.org/r/20220429160606.127307-3-sj@kernel.orgSigned-off-by:
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SeongJae Park authored
Patch series "mm/damon: Support online tuning". Effects of DAMON and DAMON-based Operation Schemes highly depends on the configurations. Wrong configurations could even result in unexpected efficiency degradations. For finding a best configuration, repeating incremental configuration changes and results measurements, in other words, online tuning, could be helpful. Nevertheless, DAMON kernel API supports only restrictive online tuning. Worse yet, the sysfs-based DAMON user interface doesn't support online tuning at all. DAMON_RECLAIM also doesn't support online tuning. This patchset makes the DAMON kernel API, DAMON sysfs interface, and DAMON_RECLAIM supports online tuning. Sequence of patches ------------------- First two patches enhance DAMON online tuning for kernel API users. Specifically, patch 1 let kernel API users to be able to do DAMON online tuning without a restriction, and patch 2 makes error handling easier. Following seven patches (patches 3-9) refactor code for better readability and easier reuse of code fragments that will be useful for online tuning support. Patch 10 introduces DAMON callback based user request handling structure for DAMON sysfs interface, and patch 11 enables DAMON online tuning via DAMON sysfs interface. Documentation patch (patch 12) for usage of it follows. Patch 13 enables online tuning of DAMON_RECLAIM and finally patch 14 documents the DAMON_RECLAIM online tuning usage. This patch (of 14): For updating input parameters for running DAMON contexts, DAMON kernel API users can use the contexts' callbacks, as it is the safe place for context internal data accesses. When the context has DAMON-based operation schemes and all schemes are deactivated due to their watermarks, however, DAMON does nothing but only watermarks checks. As a result, no callbacks will be called back, and therefore the kernel API users cannot update the input parameters including monitoring attributes, DAMON-based operation schemes, and watermarks. To let users easily update such DAMON input parameters in such a case, this commit adds a new callback, 'after_wmarks_check()'. It will be called after each watermarks check. Users can do the online input parameters update in the callback even under the schemes deactivated case. Link: https://lkml.kernel.org/r/20220429160606.127307-2-sj@kernel.orgSigned-off-by:
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