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

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Date:	Mon, 2 Feb 2015 14:09:12 +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


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)

>  	zram->queue = blk_alloc_queue(GFP_KERNEL);
>  	if (!zram->queue) {


	-ss
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