From: Andrea Arcangeli <aarcange@xxxxxxxxxx> Subject: 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@xxxxxxxxxx Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx> Cc: "Dr. David Alan Gilbert" <dgilbert@xxxxxxxxxx> Cc: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx> Cc: Michael Rapoport <RAPOPORT@xxxxxxxxxx> Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx> Cc: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx> Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/uapi/linux/userfaultfd.h | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff -puN include/uapi/linux/userfaultfd.h~userfaultfd-hugetlbfs-uffd_feature_missing_shmem include/uapi/linux/userfaultfd.h --- a/include/uapi/linux/userfaultfd.h~userfaultfd-hugetlbfs-uffd_feature_missing_shmem +++ a/include/uapi/linux/userfaultfd.h @@ -21,7 +21,8 @@ #define UFFD_API_FEATURES (UFFD_FEATURE_EVENT_FORK | \ UFFD_FEATURE_EVENT_REMAP | \ UFFD_FEATURE_EVENT_MADVDONTNEED | \ - UFFD_FEATURE_MISSING_HUGETLBFS) + UFFD_FEATURE_MISSING_HUGETLBFS | \ + UFFD_FEATURE_MISSING_SHMEM) #define UFFD_API_IOCTLS \ ((__u64)1 << _UFFDIO_REGISTER | \ (__u64)1 << _UFFDIO_UNREGISTER | \ @@ -146,12 +147,17 @@ struct uffdio_api { * it, so userland can later check if the feature flag is * present in uffdio_api.features after UFFDIO_API * succeeded. + * + * UFFD_FEATURE_MISSING_SHMEM works the same as + * UFFD_FEATURE_MISSING_HUGETLBFS, but it applies to shmem + * (i.e. tmpfs and other shmem based APIs). */ #define UFFD_FEATURE_PAGEFAULT_FLAG_WP (1<<0) #define UFFD_FEATURE_EVENT_FORK (1<<1) #define UFFD_FEATURE_EVENT_REMAP (1<<2) #define UFFD_FEATURE_EVENT_MADVDONTNEED (1<<3) #define UFFD_FEATURE_MISSING_HUGETLBFS (1<<4) +#define UFFD_FEATURE_MISSING_SHMEM (1<<5) __u64 features; __u64 ioctls; _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
