From: "Theodore Ts'o" Subject: FIEMAP sometimes returns bad information for delalloc extents Date: Sat, 27 Mar 2010 11:07:30 -0400 Message-ID: To: linux-ext4@vger.kernel.org Return-path: Received: from THUNK.ORG ([69.25.196.29]:45826 "EHLO thunker.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753396Ab0C0PHg (ORCPT ); Sat, 27 Mar 2010 11:07:36 -0400 Sender: linux-ext4-owner@vger.kernel.org List-ID: I was monitoring the progress of a distributed download program, and saw the following output from two runs of filefrag taken a few seconds apart: 8 790 8825663 8825551 65 9 855 0 8825727 319 unknown,delalloc 10 1174 8798367 318 128 7 790 8825663 8825559 69 8 1174 8798367 8825731 128 The length of the delalloc extent, 319, is bogus. The 319 seems to come from 1174 - 855. But it's not actually the number of delayed allocation blocks, as we can see when the blocks finally get written; apparently it was only 4 blocks long. I don't have time to try to track this down just now, and it's not all that serious a bug since delalloc regions are by definition highly transient, but it does look like we have a bug here. - Ted