linux-kernel - Re: [PATCH 07/17] fs: icache atomic inodes

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Message-Id: <20100929233705.dc959855.akpm@linux-foundation.org>
Date:	Wed, 29 Sep 2010 23:37:05 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Dave Chinner <david@...morbit.com>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 07/17] fs: icache atomic inodes_stat

On Thu, 30 Sep 2010 16:20:57 +1000 Dave Chinner <david@...morbit.com> wrote:

> > > --- a/fs/fs-writeback.c
> > > +++ b/fs/fs-writeback.c
> > > @@ -764,7 +764,8 @@ static long wb_check_old_data_flush(struct bdi_writeback *wb)
> > >  	wb->last_old_flush = jiffies;
> > >  	nr_pages = global_page_state(NR_FILE_DIRTY) +
> > >  			global_page_state(NR_UNSTABLE_NFS) +
> > > -			(inodes_stat.nr_inodes - inodes_stat.nr_unused);
> > > +			(atomic_read(&inodes_stat.nr_inodes) -
> > > +			atomic_read(&inodes_stat.nr_unused));
> > 
> > race bug.
> 
> What new race?  The code has gone from using subtraction of unlocked
> counters to using subtraction of unlocked atomic counters. I can't
> see any new race condition in that transformation....

Oh.  I assumed that all the above used to happen under inode_lock.

Coz that's wot the changelog told me :)
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