f2fs: fix to check return value in f2fs_insert_range()

In f2fs_insert_range(), it missed to check return value of
filemap_write_and_wait_range(), fix it.

Meanwhile, just return error number once __exchange_data_block()
fails.
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/file.c

@@ -1679,10 +1679,12 @@ static int f2fs_insert_range(struct inode *inode, loff_t offset, loff_t len)
 	}
 	filemap_invalidate_unlock(mapping);
 	f2fs_up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
+	if (ret)
+		return ret;
 
 	/* write out all moved pages, if possible */
 	filemap_invalidate_lock(mapping);
-	filemap_write_and_wait_range(mapping, offset, LLONG_MAX);
+	ret = filemap_write_and_wait_range(mapping, offset, LLONG_MAX);
 	truncate_pagecache(inode, offset);
 	filemap_invalidate_unlock(mapping);