Btrfs: free sys_array eb as soon as possible

While reading sys_chunk_array in superblock, btrfs creates a temporary
extent buffer.  Since we don't use it after finishing reading
 sys_chunk_array, we don't need to keep it in memory.
Signed-off-by: NLiu Bo <bo.li.liu@oracle.com>
Signed-off-by: NDavid Sterba <dsterba@suse.com>

fs/btrfs/volumes.c

@@ -6630,13 +6630,13 @@ int btrfs_read_sys_array(struct btrfs_root *root)
 		sb_array_offset += len;
 		cur_offset += len;
 	}
-	free_extent_buffer(sb);
+	free_extent_buffer_stale(sb);
 	return ret;
 
 out_short_read:
 	printk(KERN_ERR "BTRFS: sys_array too short to read %u bytes at offset %u\n",
 			len, cur_offset);
-	free_extent_buffer(sb);
+	free_extent_buffer_stale(sb);
 	return -EIO;
 }