xfs: Fix xfs_swap_extents() after removal of xfs_flushinval_pages()

Commit fb595814 removed
xfs_flushinval_pages() and changed its callers to use
filemap_write_and_wait() and  truncate_pagecache_range() directly.

But in xfs_swap_extents() this change accidental switched the argument
for 'tip' to 'ip'. This patch switches it back to 'tip'
Signed-off-by: Torsten Kaiser <just.for.lkml@googlemail.com>
Reviewed-by: Ben Myers <bpm@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

fs/xfs/xfs_dfrag.c

@@ -246,10 +246,10 @@ xfs_swap_extents(
 		goto out_unlock;
 	}
 
-	error = -filemap_write_and_wait(VFS_I(ip)->i_mapping);
+	error = -filemap_write_and_wait(VFS_I(tip)->i_mapping);
 	if (error)
 		goto out_unlock;
-	truncate_pagecache_range(VFS_I(ip), 0, -1);
+	truncate_pagecache_range(VFS_I(tip), 0, -1);
 
 	/* Verify O_DIRECT for ftmp */
 	if (VN_CACHED(VFS_I(tip)) != 0) {