linux-kernel - Re: [PATCH 2/6] kill-the-BKL/reiserfs: release the write lock before rescheduling on do_journal

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Message-ID: <20090501133147.GF6011@nowhere>
Date:	Fri, 1 May 2009 15:31:48 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	LKML <linux-kernel@...r.kernel.org>, Jeff Mahoney <jeffm@...e.com>,
	ReiserFS Development List <reiserfs-devel@...r.kernel.org>,
	Chris Mason <chris.mason@...cle.com>,
	Alexander Beregalov <a.beregalov@...il.com>,
	Alessio Igor Bogani <abogani@...ware.it>,
	Jonathan Corbet <corbet@....net>,
	Alexander Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH 2/6] kill-the-BKL/reiserfs: release the write lock
	before rescheduling on do_journal_end()

On Fri, May 01, 2009 at 09:09:11AM +0200, Ingo Molnar wrote:
> 
> * Frederic Weisbecker <fweisbec@...il.com> wrote:
> 
> > When do_journal_end() copies data to the journal blocks buffers in memory,
> > it reschedules if needed between each block copied and dirtyfied.
> > 
> > We can also release the write lock at this rescheduling stage,
> > like did the bkl implicitly.
> > 
> > [ Impact: release the reiserfs write lock when it is not needed ]
> > 
> > Cc: Jeff Mahoney <jeffm@...e.com>
> > Cc: Chris Mason <chris.mason@...cle.com>
> > Cc: Alexander Beregalov <a.beregalov@...il.com>
> > Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
> > ---
> >  fs/reiserfs/journal.c |    2 ++
> >  1 files changed, 2 insertions(+), 0 deletions(-)
> > 
> > diff --git a/fs/reiserfs/journal.c b/fs/reiserfs/journal.c
> > index 7976d7d..373d080 100644
> > --- a/fs/reiserfs/journal.c
> > +++ b/fs/reiserfs/journal.c
> > @@ -4232,7 +4232,9 @@ static int do_journal_end(struct reiserfs_transaction_handle *th,
> >  		next = cn->next;
> >  		free_cnode(sb, cn);
> >  		cn = next;
> > +		reiserfs_write_unlock(sb);
> >  		cond_resched();
> > +		reiserfs_write_lock(sb);
> 
> There's 8 cond_resched()'s in the code - i'd suggest to introduce a 
> helper for this - reiserfs_write_cond_resched(sb) or so?
> 
> 	Ingo

Indeed, that + the pattern suggested by Al.

Thanks.

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