ocfs2: release page lock before calling ->page_mkwrite

__do_fault() was calling ->page_mkwrite() with the page lock held, which
violates the locking rules for that callback.  Release and retake the page
lock around the callback to avoid deadlocking file systems which manually
take it.
Signed-off-by: NMark Fasheh <mark.fasheh@oracle.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/memory.c

@@ -2369,11 +2369,14 @@ static int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 			 * address space wants to know that the page is about
 			 * to become writable
 			 */
-			if (vma->vm_ops->page_mkwrite &&
-			    vma->vm_ops->page_mkwrite(vma, page) < 0) {
-				fdata.type = VM_FAULT_SIGBUS;
-				anon = 1; /* no anon but release faulted_page */
-				goto out;
+			if (vma->vm_ops->page_mkwrite) {
+				unlock_page(page);
+				if (vma->vm_ops->page_mkwrite(vma, page) < 0) {
+					fdata.type = VM_FAULT_SIGBUS;
+					anon = 1; /* no anon but release faulted_page */
+					goto out_unlocked;
+				}
+				lock_page(page);
 			}
 		}
 
@@ -2425,6 +2428,7 @@ static int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 
 out:
 	unlock_page(faulted_page);
+out_unlocked:
 	if (anon)
 		page_cache_release(faulted_page);
 	else if (dirty_page) {