userfaultfd: introduce vma_can_userfault

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

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Mike Rapoport <[email protected]>
Signed-off-by: Andrea Arcangeli <[email protected]>
Acked-by: Hillf Danton <[email protected]>
Cc: "Dr. David Alan Gilbert" <[email protected]>
Cc: Michael Rapoport <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: rppt

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