linux-kernel - Re: [PATCH v1 2/2] zram: remove init_lock in zram_make

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Date:	Mon, 2 Feb 2015 12:47:30 +0900
From:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:	Minchan Kim <minchan@...nel.org>
Cc:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linux-MM <linux-mm@...ck.org>, Nitin Gupta <ngupta@...are.org>,
	Jerome Marchand <jmarchan@...hat.com>,
	Ganesh Mahendran <opensource.ganesh@...il.com>
Subject: Re: [PATCH v1 2/2] zram: remove init_lock in zram_make_request

On (02/02/15 11:45), Minchan Kim wrote:
> On Mon, Feb 02, 2015 at 10:59:40AM +0900, Sergey Senozhatsky wrote:
> > On (02/02/15 10:43), Minchan Kim wrote:
> > > >  static inline int init_done(struct zram *zram)
> > > >  {
> > > > -	return zram->meta != NULL;
> > > > +	return atomic_read(&zram->refcount);
> > > 
> > > As I said previous mail, it could make livelock so I want to use disksize
> > > in here to prevent further I/O handling.
> > 
> > just as I said in my previous email -- is this live lock really possible?
> > we need to umount device to continue with reset. and umount will kill IOs out
> > of our way.
> > 
> > the other reset caller is  __exit zram_exit(). but once again, I don't
> > expect this function being executed on mounted device and module being
> > in use.
> > 
> > 
> > > > +static inline void zram_put(struct zram *zram)
> > > > +{
> > > > +	if (atomic_dec_and_test(&zram->refcount))
> > > > +		complete(&zram->io_done);
> > > > +}
> > > 
> > > Although I suggested this complete, it might be rather overkill(pz,
> > > understand me it was work in midnight. :))
> > > Instead, we could use just atomic_dec in here and
> > > use wait_event(event, atomic_read(&zram->refcount) == 0) in reset.
> > > 
> > 
> > yes, I think it can do the trick.
> 
> Hey, it's not a trick. It suits for the our goal well. Completion
> was too much, I think.
> 

sure :)

	-ss
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