netdev - Re: [PATCH 3/8] aio: store event at final iocb

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Date:   Mon, 11 Mar 2019 22:52:30 +0000
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Christoph Hellwig <hch@....de>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Eric Dumazet <eric.dumazet@...il.com>,
        David Miller <davem@...emloft.net>,
        Jason Baron <jbaron@...mai.com>, kgraul@...ux.ibm.com,
        ktkhai@...tuozzo.com, kyeongdon.kim@....com,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        Netdev <netdev@...r.kernel.org>, pabeni@...hat.com,
        syzkaller-bugs@...glegroups.com, xiyou.wangcong@...il.com,
        zhengbin <zhengbin13@...wei.com>, bcrl@...ck.org,
        linux-fsdevel@...r.kernel.org, linux-aio@...ck.org,
        houtao1@...wei.com, yi.zhang@...wei.com
Subject: Re: [PATCH 3/8] aio: store event at final iocb_put()

On Mon, Mar 11, 2019 at 09:13:28PM +0000, Al Viro wrote:
> On Mon, Mar 11, 2019 at 08:44:31PM +0100, Christoph Hellwig wrote:
> > On Sun, Mar 10, 2019 at 07:08:17AM +0000, Al Viro wrote:
> > > From: Al Viro <viro@...iv.linux.org.uk>
> > > 
> > > Instead of having aio_complete() set ->ki_res.{res,res2}, do that
> > > explicitly in its callers, drop the reference (as aio_complete()
> > > used to do) and delay the rest until the final iocb_put().
> > > 
> > > Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
> > > ---
> > >  fs/aio.c | 45 ++++++++++++++++++++-------------------------
> > >  1 file changed, 20 insertions(+), 25 deletions(-)
> > > 
> > > diff --git a/fs/aio.c b/fs/aio.c
> > > index 2249a7a1d6b3..b9c4c1894020 100644
> > > --- a/fs/aio.c
> > > +++ b/fs/aio.c
> > > @@ -1077,24 +1077,10 @@ static inline void iocb_destroy(struct aio_kiocb *iocb)
> > >  	kmem_cache_free(kiocb_cachep, iocb);
> > >  }
> > >  
> > > -static inline void iocb_put(struct aio_kiocb *iocb)
> > > -{
> > > -	if (refcount_dec_and_test(&iocb->ki_refcnt))
> > > -		iocb_destroy(iocb);
> > > -}
> > 
> > Maybe iocb_put should just have been added in the place you move
> > it to in patch 1?
> 
> Might as well...

Actually, that wouldn't be any better - it would need at least a declaration
before aio_complete(), since in the original patch aio_complete() calls it.
So that wouldn't be less noisy...