xfs: factor DIO write mapping from get_blocks

Clarify and separate the buffer mapping logic so that the direct IO mapping is
not tangled up in propagating the extent status to teh mapping buffer. This
makes it easier to extend the direct IO mapping to use an ioend in future.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

fs/xfs/xfs_aops.c

@@ -1233,6 +1233,22 @@ xfs_vm_releasepage(
 	return try_to_free_buffers(page);
 }
 
+/*
+ * do all the direct IO specific mapping buffer manipulation here.
+ */
+static void
+xfs_map_direct(
+	struct inode		*inode,
+	struct buffer_head	*bh_result,
+	struct xfs_bmbt_irec	*imap,
+	xfs_off_t		offset)
+{
+	if (ISUNWRITTEN(imap)) {
+		bh_result->b_private = inode;
+		set_buffer_defer_completion(bh_result);
+	}
+}
+
 STATIC int
 __xfs_get_blocks(
 	struct inode		*inode,
@@ -1331,21 +1347,19 @@ __xfs_get_blocks(
 		goto out_unlock;
 	}
 
-	if (imap.br_startblock != HOLESTARTBLOCK &&
-	    imap.br_startblock != DELAYSTARTBLOCK) {
 	/*
-		 * For unwritten extents do not report a disk address on
-		 * the read case (treat as if we're reading into a hole).
+	 * For unwritten extents do not report a disk address in the buffered
+	 * read case (treat as if we're reading into a hole).
 	 */
-		if (create || !ISUNWRITTEN(&imap))
+	if (imap.br_startblock != HOLESTARTBLOCK &&
+	    imap.br_startblock != DELAYSTARTBLOCK &&
+	    (create || !ISUNWRITTEN(&imap))) {
 		xfs_map_buffer(inode, bh_result, &imap, offset);
-		if (create && ISUNWRITTEN(&imap)) {
-			if (direct) {
-				bh_result->b_private = inode;
-				set_buffer_defer_completion(bh_result);
-			}
+		if (ISUNWRITTEN(&imap))
 			set_buffer_unwritten(bh_result);
-		}
+		/* direct IO needs special help */
+		if (create && direct)
+			xfs_map_direct(inode, bh_result, &imap, offset);
 	}
 
 	/*