userfaultfd: shmem: allow registration of shared memory ranges

Expand the userfaultfd_register/unregister routines to allow shared
memory VMAs.

Currently, there is no UFFDIO_ZEROPAGE and write-protection support for
shared memory VMAs, which is reflected in ioctl methods supported by
uffdio_register.

Link: http://lkml.kernel.org/r/20161216144821.5183-34-aarcange@redhat.com
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.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: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 593135c296bc2deab05fc8e046276a7ba15711aa..18406158e13fbf5e9b4e7041489f2d20e404c075 100644 (file)
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -1098,7 +1098,8 @@ static __always_inline int validate_range(struct mm_struct *mm,
 
 static inline bool vma_can_userfault(struct vm_area_struct *vma)
 {
-       return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma);
+       return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma) ||
+               vma_is_shmem(vma);
 }
 
 static int userfaultfd_register(struct userfaultfd_ctx *ctx,
@@ -1111,7 +1112,7 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
        struct uffdio_register __user *user_uffdio_register;
        unsigned long vm_flags, new_flags;
        bool found;
-       bool huge_pages;
+       bool non_anon_pages;
        unsigned long start, end, vma_end;
 
        user_uffdio_register = (struct uffdio_register __user *) arg;
@@ -1175,13 +1176,9 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
 
        /*
         * Search for not compatible vmas.
-        *
-        * FIXME: this shall be relaxed later so that it doesn't fail
-        * on tmpfs backed vmas (in addition to the current allowance
-        * on anonymous vmas).
         */
        found = false;
-       huge_pages = false;
+       non_anon_pages = false;
        for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) {
                cond_resched();
 
@@ -1220,8 +1217,8 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
                /*
                 * Note vmas containing huge pages
                 */
-               if (is_vm_hugetlb_page(cur))
-                       huge_pages = true;
+               if (is_vm_hugetlb_page(cur) || vma_is_shmem(cur))
+                       non_anon_pages = true;
 
                found = true;
        }
@@ -1292,7 +1289,7 @@ out_unlock:
                 * userland which ioctls methods are guaranteed to
                 * succeed on this range.
                 */
-               if (put_user(huge_pages ? UFFD_API_RANGE_IOCTLS_HPAGE :
+               if (put_user(non_anon_pages ? UFFD_API_RANGE_IOCTLS_BASIC :
                             UFFD_API_RANGE_IOCTLS,
                             &user_uffdio_register->ioctls))
                        ret = -EFAULT;
@@ -1352,10 +1349,6 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
 
        /*
         * Search for not compatible vmas.
-        *
-        * FIXME: this shall be relaxed later so that it doesn't fail
-        * on tmpfs backed vmas (in addition to the current allowance
-        * on anonymous vmas).
         */
        found = false;
        ret = -EINVAL;

diff --git a/include/uapi/linux/userfaultfd.h b/include/uapi/linux/userfaultfd.h
index 7293321abdfb0117e769c14eb48da3189ef8ff41..10631a4cdb24c0bac419aa8c6ce5833667f1a562 100644 (file)
--- a/include/uapi/linux/userfaultfd.h
+++ b/include/uapi/linux/userfaultfd.h
@@ -30,7 +30,7 @@
        ((__u64)1 << _UFFDIO_WAKE |             \
         (__u64)1 << _UFFDIO_COPY |             \
         (__u64)1 << _UFFDIO_ZEROPAGE)
-#define UFFD_API_RANGE_IOCTLS_HPAGE            \
+#define UFFD_API_RANGE_IOCTLS_BASIC            \
        ((__u64)1 << _UFFDIO_WAKE |             \
         (__u64)1 << _UFFDIO_COPY)
 

diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
index 3011711212ca994dce4ccb43f24665c62fe43eb7..d753a9161411304ba593051e2036f89c858bc7e1 100644 (file)
--- a/tools/testing/selftests/vm/userfaultfd.c
+++ b/tools/testing/selftests/vm/userfaultfd.c
@@ -129,7 +129,7 @@ static void allocate_area(void **alloc_area)
 
 #else /* HUGETLB_TEST */
 
-#define EXPECTED_IOCTLS                UFFD_API_RANGE_IOCTLS_HPAGE
+#define EXPECTED_IOCTLS                UFFD_API_RANGE_IOCTLS_BASIC
 
 static int release_pages(char *rel_area)
 {