linux-kernel - Re: [PATCH] fs/inode: No need to take ->i_lock right after alloc

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Message-ID: <14058048.nDrCfeHD0z@sandpuppy>
Date:	Fri, 10 Jan 2014 10:48:57 +0100
From:	Richard Weinberger <richard@....at>
To:	Christoph Hellwig <hch@....de>
Cc:	viro@...iv.linux.org.uk, dchinner@...hat.com,
	eric.dumazet@...il.com, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fs/inode: No need to take ->i_lock right after alloc_inode()

Am Freitag, 10. Januar 2014, 10:22:29 schrieb Christoph Hellwig:
> On Wed, Jan 08, 2014 at 11:21:13AM +0100, Richard Weinberger wrote:
> > > In all three cases, new_inode_pseudo(), iget_locked() and
> > > iget5_locked(),
> > > we own the new inode exclusively at this point and therefore taking
> > > ->i_lock to protect ->i_state/->i_hash against concurrent access is
> > > superfluous.
> 
> We'd still need some sort of barrier to make sure the state is visible
> to all CPUs before it becomes visible, usually by another spin_unlock
> happing later.  If you have a workload where removing these is critical
> please document these issues in the code and resubmit it with an explanation
> of the workload where it helps.  If it's just a cleanup I wouldn't bother
> with it.

The patch was indented as cleanup patch, but as you pointed out I've failed to
think about the barrier.
Let's drop the patch. :D

Thanks,
//richard
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