do_mremap() untangling, part 3

Take the check for being able to expand vma in place into a separate
helper.

Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Acked-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 12 insertions, 4 deletions

diff --git a/mm/mremap.c b/mm/mremap.c
index 5f346178f16f..90e422c9f410 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -366,6 +366,17 @@ out:
         return ret;
 }
 
+static int vma_expandable(struct vm_area_struct *vma, unsigned long delta)
+{
+        unsigned long max_addr = TASK_SIZE;
+        if (vma->vm_next)
+                max_addr = vma->vm_next->vm_start;
+        if (max_addr - vma->vm_end < delta)
+                return 0;
+        /* we need to do arch-specific checks here */
+        return 1;
+}
+
 /*
  * Expand (or shrink) an existing mapping, potentially moving it at the
  * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
@@ -430,11 +441,8 @@ unsigned long do_mremap(unsigned long addr,
         /* old_len exactly to the end of the area..
          */
         if (old_len == vma->vm_end - addr) {
-                unsigned long max_addr = TASK_SIZE;
-                if (vma->vm_next)
-                        max_addr = vma->vm_next->vm_start;
                 /* can we just expand the current mapping? */
-                if (max_addr - addr >= new_len) {
+                if (vma_expandable(vma, new_len - old_len)) {
                         int pages = (new_len - old_len) >> PAGE_SHIFT;
 
                         vma_adjust(vma, vma->vm_start,