userfaultfd: hugetlbfs: UFFD_FEATURE_MISSING_SHMEM
Userland developers asked to be notified immediately by the UFFDIO_API ioctl if shmem missing mode is supported by userfaultfd in the running kernel. This avoids the need to run UFFDIO_REGISTER on a shmem virtual memory range to find out. Link: http://lkml.kernel.org/r/20161216144821.5183-38-aarcange@redhat.com Signed-off-by: Andrea Arcangeli <aarcange@redhat.com> Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com> Cc: Hillf Danton <hillf.zj@alibaba-inc.com> Cc: Michael Rapoport <RAPOPORT@il.ibm.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Pavel Emelyanov <xemul@parallels.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -21,7 +21,8 @@
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#define UFFD_API_FEATURES (UFFD_FEATURE_EVENT_FORK | \
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UFFD_FEATURE_EVENT_REMAP | \
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UFFD_FEATURE_EVENT_MADVDONTNEED | \
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UFFD_FEATURE_MISSING_HUGETLBFS)
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UFFD_FEATURE_MISSING_HUGETLBFS | \
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UFFD_FEATURE_MISSING_SHMEM)
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#define UFFD_API_IOCTLS \
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((__u64)1 << _UFFDIO_REGISTER | \
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(__u64)1 << _UFFDIO_UNREGISTER | \
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@ -146,12 +147,17 @@ struct uffdio_api {
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* it, so userland can later check if the feature flag is
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* present in uffdio_api.features after UFFDIO_API
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* succeeded.
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*
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* UFFD_FEATURE_MISSING_SHMEM works the same as
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* UFFD_FEATURE_MISSING_HUGETLBFS, but it applies to shmem
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* (i.e. tmpfs and other shmem based APIs).
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*/
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#define UFFD_FEATURE_PAGEFAULT_FLAG_WP (1<<0)
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#define UFFD_FEATURE_EVENT_FORK (1<<1)
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#define UFFD_FEATURE_EVENT_REMAP (1<<2)
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#define UFFD_FEATURE_EVENT_MADVDONTNEED (1<<3)
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#define UFFD_FEATURE_MISSING_HUGETLBFS (1<<4)
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#define UFFD_FEATURE_MISSING_SHMEM (1<<5)
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__u64 features;
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__u64 ioctls;
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