linux-kernel - Re: [PATCH 1/2] JBD2: Allow feature checks before journal recovery

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Message-ID: <20100721175024.GF1215@atrey.karlin.mff.cuni.cz>
Date:	Wed, 21 Jul 2010 19:50:24 +0200
From:	Jan Kara <jack@...e.cz>
To:	"Patrick J. LoPresti" <lopresti@...il.com>
Cc:	Jan Kara <jack@...e.cz>, ocfs2-devel@....oracle.com,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-ext4@...r.kernel.org
Subject: Re: [PATCH 1/2] JBD2: Allow feature checks before journal recovery

> On Wed, Jul 21, 2010 at 10:27 AM, Jan Kara <jack@...e.cz> wrote:
> >> Signed-off-by: Patrick LoPresti <lopresti@...il.com>
> >>
> >> 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...
> 
> How about this?
> 
>          if (!compat && !ro && !incompat)
>                 return 1;
> +        if (journal->j_format_version == 0 &&
> journal_get_superblock(journal) != 0)
> +               return 0;
>         if (journal->j_format_version == 1)
>                 return 0;
> 
> journal_init_common() uses kzalloc() to allocate the journal_t, and
> journal_get_superblock() fills it in, so I believe this is a valid
> test.
  Yes, this looks OK. Just add a comment before the check like
/* Load journal super block if it isn't loaded yet */

								Honza
-- 
Jan Kara <jack@...e.cz>
SuSE CR Labs
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