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

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Date:	Mon, 2 Feb 2015 14:18:05 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Cc:	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 Mon, Feb 02, 2015 at 02:09:12PM +0900, Sergey Senozhatsky wrote:
> 
> the patch mosly looks good, except for one place:
> 
> On (02/02/15 13:28), Minchan Kim wrote:
> > @@ -783,6 +812,8 @@ static ssize_t disksize_store(struct device *dev,
> >  		goto out_destroy_comp;
> >  	}
> >  
> > +	init_waitqueue_head(&zram->io_done);
> > +	zram_meta_get(zram);
> 
> it was
> +       init_completion(&zram->io_done);
> +       atomic_set(&zram->refcount, 1);
> 
> I think we need to replace zram_meta_get(zram) with atomic_set(&zram->refcount, 1).
> 
> ->refcount is 0 by default and atomic_inc_not_zero(&zram->refcount) will not
> increment it here, nor anywhere else.
> 
> 
> >  	zram->meta = meta;
> >  	zram->comp = comp;
> >  	zram->disksize = disksize;
> > @@ -838,8 +869,8 @@ static ssize_t reset_store(struct device *dev,
> >  	/* Make sure all pending I/O is finished */
> >  	fsync_bdev(bdev);
> >  	bdput(bdev);
> > -
> 
> [..]
> 
> > @@ -1041,6 +1075,7 @@ static int create_device(struct zram *zram, int device_id)
> >  	int ret = -ENOMEM;
> >  
> >  	init_rwsem(&zram->init_lock);
> > +	atomic_set(&zram->refcount, 0);
> 
> sorry, I forgot that zram is kzalloc()-ated. so we can drop
> 
> 	atomic_set(&zram->refcount, 0)
> 

Everything are fixed. Ready to send a patch.
But before sending, hope we fix umount race issue first.

Thanks a lot, Sergey!

-- 
Kind regards,
Minchan Kim
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