From 5679fd2c2b3e821ff39680f20e405c009d3e0f9c Mon Sep 17 00:00:00 2001 From: Axel Rasmussen Date: Fri, 14 May 2021 10:39:49 +1000 Subject: [PATCH] BACKPORT: FROMGIT: userfaultfd/shmem: advertise shmem minor fault support Now that the feature is fully implemented (the faulting path hooks exist so userspace is notified, and the ioctl to resolve such faults is available), advertise this as a supported feature. Link: https://lkml.kernel.org/r/20210503180737.2487560-6-axelrasmussen@google.com Signed-off-by: Axel Rasmussen Acked-by: Hugh Dickins Acked-by: Peter Xu Cc: Alexander Viro Cc: Andrea Arcangeli Cc: Brian Geffon Cc: "Dr . David Alan Gilbert" Cc: Jerome Glisse Cc: Joe Perches Cc: Kirill A. Shutemov Cc: Lokesh Gidra Cc: Mike Kravetz Cc: Mike Rapoport Cc: Mina Almasry Cc: Oliver Upton Cc: Shaohua Li Cc: Shuah Khan Cc: Stephen Rothwell Cc: Wang Qing Signed-off-by: Andrew Morton Signed-off-by: Stephen Rothwell (cherry picked from commit 37aa962fe33a562fd0ac21b68938023e12041fc3 https: //git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git akpm) Link: https://lore.kernel.org/patchwork/patch/1420971/ Conflicts: Documentation/admin-guide/mm/userfaultfd.rst (Manual rebase) Signed-off-by: Lokesh Gidra Bug: 187930641 Change-Id: I5fbab3783ff8671c0a5aa4826aead2d63f5cbbf3 --- Documentation/admin-guide/mm/userfaultfd.rst | 3 ++- fs/userfaultfd.c | 3 ++- include/uapi/linux/userfaultfd.h | 7 ++++++- 3 files changed, 10 insertions(+), 3 deletions(-) diff --git a/Documentation/admin-guide/mm/userfaultfd.rst b/Documentation/admin-guide/mm/userfaultfd.rst index 6a1477493441..819e09bb02ff 100644 --- a/Documentation/admin-guide/mm/userfaultfd.rst +++ b/Documentation/admin-guide/mm/userfaultfd.rst @@ -77,7 +77,8 @@ events, except page fault notifications, may be generated: - UFFD_FEATURE_MINOR_HUGETLBFS indicates that the kernel supports UFFDIO_REGISTER_MODE_MINOR registration for hugetlbfs virtual memory - areas. + areas. UFFD_FEATURE_MINOR_SHMEM is the analogous feature indicating + support for shmem virtual memory areas. The userland application should set the feature flags it intends to use when invoking the UFFDIO_API ioctl, to request that those features be diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 35db9f655a90..300f6190fb54 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -1939,7 +1939,8 @@ static int userfaultfd_api(struct userfaultfd_ctx *ctx, /* report all available features and ioctls to userland */ uffdio_api.features = UFFD_API_FEATURES; #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR - uffdio_api.features &= ~UFFD_FEATURE_MINOR_HUGETLBFS; + uffdio_api.features &= + ~(UFFD_FEATURE_MINOR_HUGETLBFS | UFFD_FEATURE_MINOR_SHMEM); #endif uffdio_api.ioctls = UFFD_API_IOCTLS; ret = -EFAULT; diff --git a/include/uapi/linux/userfaultfd.h b/include/uapi/linux/userfaultfd.h index 3158e52e95ea..0191d247894c 100644 --- a/include/uapi/linux/userfaultfd.h +++ b/include/uapi/linux/userfaultfd.h @@ -30,7 +30,8 @@ UFFD_FEATURE_MISSING_SHMEM | \ UFFD_FEATURE_SIGBUS | \ UFFD_FEATURE_THREAD_ID | \ - UFFD_FEATURE_MINOR_HUGETLBFS) + UFFD_FEATURE_MINOR_HUGETLBFS | \ + UFFD_FEATURE_MINOR_SHMEM) #define UFFD_API_IOCTLS \ ((__u64)1 << _UFFDIO_REGISTER | \ (__u64)1 << _UFFDIO_UNREGISTER | \ @@ -180,6 +181,9 @@ struct uffdio_api { * UFFD_FEATURE_MINOR_HUGETLBFS indicates that minor faults * can be intercepted (via REGISTER_MODE_MINOR) for * hugetlbfs-backed pages. + * + * UFFD_FEATURE_MINOR_SHMEM indicates the same support as + * UFFD_FEATURE_MINOR_HUGETLBFS, but for shmem-backed pages instead. */ #define UFFD_FEATURE_PAGEFAULT_FLAG_WP (1<<0) #define UFFD_FEATURE_EVENT_FORK (1<<1) @@ -191,6 +195,7 @@ struct uffdio_api { #define UFFD_FEATURE_SIGBUS (1<<7) #define UFFD_FEATURE_THREAD_ID (1<<8) #define UFFD_FEATURE_MINOR_HUGETLBFS (1<<9) +#define UFFD_FEATURE_MINOR_SHMEM (1<<10) __u64 features; __u64 ioctls;