userfaultfd: introduce vma_can_userfault

Check whether a VMA can be used with userfault in more compact way

Link: http://lkml.kernel.org/r/20161216144821.5183-28-aarcange@redhat.com
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.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 11b5e65e8fba40c41c6ebdfa6f590203b7dcc3a5..593135c296bc2deab05fc8e046276a7ba15711aa 100644 (file)
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -1096,6 +1096,11 @@ static __always_inline int validate_range(struct mm_struct *mm,
        return 0;
 }
 
+static inline bool vma_can_userfault(struct vm_area_struct *vma)
+{
+       return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma);
+}
+
 static int userfaultfd_register(struct userfaultfd_ctx *ctx,
                                unsigned long arg)
 {
@@ -1185,7 +1190,7 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
 
                /* check not compatible vmas */
                ret = -EINVAL;
-               if (!vma_is_anonymous(cur) && !is_vm_hugetlb_page(cur))
+               if (!vma_can_userfault(cur))
                        goto out_unlock;
                /*
                 * If this vma contains ending address, and huge pages
@@ -1229,7 +1234,7 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
        do {
                cond_resched();
 
-               BUG_ON(!vma_is_anonymous(vma) && !is_vm_hugetlb_page(vma));
+               BUG_ON(!vma_can_userfault(vma));
                BUG_ON(vma->vm_userfaultfd_ctx.ctx &&
                       vma->vm_userfaultfd_ctx.ctx != ctx);
 
@@ -1367,7 +1372,7 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
                 * provides for more strict behavior to notice
                 * unregistration errors.
                 */
-               if (!vma_is_anonymous(cur) && !is_vm_hugetlb_page(cur))
+               if (!vma_can_userfault(cur))
                        goto out_unlock;
 
                found = true;
@@ -1381,7 +1386,7 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
        do {
                cond_resched();
 
-               BUG_ON(!vma_is_anonymous(vma) && !is_vm_hugetlb_page(vma));
+               BUG_ON(!vma_can_userfault(vma));
 
                /*
                 * Nothing to do: this vma is already registered into this