From mboxrd@z Thu Jan 1 00:00:00 1970 From: Theodore Ts'o Subject: Re: [PATCH 01/25] e2fsck/debugfs: fix descriptor block size handling errors with journal_csum Date: Thu, 11 Sep 2014 12:43:02 -0400 Message-ID: <20140911164302.GI26178@thunk.org> References: <20140908231135.25904.66591.stgit@birch.djwong.org> <20140908231143.25904.98802.stgit@birch.djwong.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-ext4@vger.kernel.org, TR Reardon To: "Darrick J. Wong" Return-path: Received: from imap.thunk.org ([74.207.234.97]:51435 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751507AbaIKQnF (ORCPT ); Thu, 11 Sep 2014 12:43:05 -0400 Content-Disposition: inline In-Reply-To: <20140908231143.25904.98802.stgit@birch.djwong.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Mon, Sep 08, 2014 at 04:11:43PM -0700, Darrick J. Wong wrote: > It turns out that there are some serious problems with the on-disk > format of journal checksum v2. The foremost is that the function to > calculate descriptor tag size returns sizes that are too big. This > causes alignment issues on some architectures and is compounded by the > fact that some parts of jbd2 use the structure size (incorrectly) to > determine the presence of a 64bit journal instead of checking the > feature flags. These errors regrettably lead to the journal > corruption reported by Mr. Reardon. > > Therefore, introduce journal checksum v3, which enlarges the > descriptor block tag format to allow for full 32-bit checksums of > journal blocks, fix the journal tag function to return the correct > sizes, and fix the jbd2 recovery code to use feature flags to > determine 64bitness. > > Add a few function helpers so we don't have to open-code quite so > many pieces. > > Switching to a 16-byte block size was found to increase journal size > overhead by a maximum of 0.1%, to convert a 32-bit journal with no > checksumming to a 32-bit journal with checksum v3 enabled. > > Signed-off-by: Darrick J. Wong > Reported-by: TR Reardon Applied, thanks. - Ted