From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kara Subject: Re: [PATCH 1/2] JBD2: Allow feature checks before journal recovery Date: Wed, 21 Jul 2010 19:27:21 +0200 Message-ID: <20100721172721.GD1215@atrey.karlin.mff.cuni.cz> References: <871vbax86w.fsf@patl.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: ocfs2-devel@oss.oracle.com, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org To: "Patrick J. LoPresti" Return-path: Content-Disposition: inline In-Reply-To: <871vbax86w.fsf@patl.com> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org > Before we start accessing a huge (> 16 TiB) OCFS2 volume, we need to > confirm that its journal supports 64-bit offsets. So we need to check > the journal's feature bits before recovering the journal. > > This is not possible with JBD2 at present, because the journal > superblock (where the feature bits reside) is not loaded from disk until > the journal is recovered. > > This patch loads the journal superblock in > jbd2_journal_check_used_features() if it has not already been loaded, > allowing us to check the feature bits before journal recovery. > > Signed-off-by: Patrick LoPresti > > diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c > index bc2ff59..c5a864f 100644 > --- a/fs/jbd2/journal.c > +++ b/fs/jbd2/journal.c > @@ -1365,6 +1365,8 @@ int jbd2_journal_check_used_features (journal_t *journal, unsigned long compat, > > if (!compat && !ro && !incompat) > return 1; > + if (journal_get_superblock(journal)) > + return 0; > if (journal->j_format_version == 1) > return 0; This looks OK in principle. It would be even nicer to avoid all the checks journal_get_superblock() when the superblock is actually loaded so that we don't do them each time jbd2_journal_check_used_features is called... Honza -- Jan Kara SuSE CR Labs