linux-kernel - Re: [PATCHv4 00/10] add on-demand device creation

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Message-ID: <20150507074159.GA3624@blaptop>
Date:	Thu, 7 May 2015 16:41:59 +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>,
	Nitin Gupta <ngupta@...are.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv4 00/10] add on-demand device creation

On Thu, May 07, 2015 at 09:33:22AM +0900, Sergey Senozhatsky wrote:
> On (05/06/15 17:20), Minchan Kim wrote:
> > I'm fine, too.
> > 
> > > 
> > > 
> > > 
> > > can you please test this patch?
> > 
> > I tested it and couldn't reproduce it during 5 minutes so it seems
> > we are correct about culpit.
> > However, it's trick and we should find a right way. :)
> > 
> 
> well, I can't reproduce this race.
> 
> btw, just for info. your script does
> 
> zram_add
> dd &
> zram_remove
> 
> by the time dd starts writing zramX device may be gone, so along with
> block devices we can see regular files in /dev/
> 
> [..]
> brw-rw---- 1 root disk   254, 0 May  7 09:16 /dev/zram0
> -rw-r--r-- 1 root root 10485760 May  7 09:17 /dev/zram1
> -rw-r--r-- 1 root root 10485760 May  7 09:20 /dev/zram10
> [..]
> 
> 
> can you please test thit patch?

Hello Sergey,

Unfortunately, I can reproduce in a few second with this patch.

> 
> ---
> 
>  drivers/block/zram/zram_drv.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index e6c4316..1e99d9f 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -1278,6 +1278,8 @@ out_free_dev:
>  static int zram_remove(struct zram *zram)
>  {
>  	struct block_device *bdev;
> +	struct request_queue *q;
> +	int device_id;
>  
>  	bdev = bdget_disk(zram->disk, 0);
>  	if (!bdev)
> @@ -1306,14 +1308,18 @@ static int zram_remove(struct zram *zram)
>  	/* Make sure all the pending I/O are finished */
>  	fsync_bdev(bdev);
>  	zram_reset_device(zram);
> -	bdput(bdev);
> +
> +	q = zram->disk->queue;
> +	device_id = zram->disk->first_minor;
>  
>  	pr_info("Removed device: %s\n", zram->disk->disk_name);
>  
> -	idr_remove(&zram_index_idr, zram->disk->first_minor);
> -	blk_cleanup_queue(zram->disk->queue);
>  	del_gendisk(zram->disk);
>  	put_disk(zram->disk);
> +	blk_cleanup_queue(q);
> +	bdput(bdev);
> +
> +	idr_remove(&zram_index_idr, device_id);
>  	kfree(zram);
>  	return 0;
>  }

-- 
Kind regards,
Minchan Kim
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