linux-kernel - Re: [PATCH 3.15 093/122] zram: revalidate disk after capacity change

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Message-ID: <20140708105617.GA947@swordfish>
Date:	Tue, 8 Jul 2014 19:56:17 +0900
From:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	Minchan Kim <minchan@...nel.org>,
	Sasha Levin <sasha.levin@...cle.com>,
	"Alexander E. Patrakov" <patrakov@...il.com>,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Nitin Gupta <ngupta@...are.org>,
	Jerome Marchand <jmarchan@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 3.15 093/122] zram: revalidate disk after capacity change

On (07/07/14 16:57), Greg Kroah-Hartman wrote:
> Date: Mon,  7 Jul 2014 16:57:35 -0700
> From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> To: linux-kernel@...r.kernel.org
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
>  stable@...r.kernel.org, Minchan Kim <minchan@...nel.org>, "Alexander E.
>  Patrakov" <patrakov@...il.com>, Sergey Senozhatsky
>  <sergey.senozhatsky@...il.com>, Nitin Gupta <ngupta@...are.org>, Jerome
>  Marchand <jmarchan@...hat.com>, Andrew Morton <akpm@...ux-foundation.org>,
>  Linus Torvalds <torvalds@...ux-foundation.org>
> Subject: [PATCH 3.15 093/122] zram: revalidate disk after capacity change
> X-Mailer: git-send-email 2.0.0.254.g50f84e3
> User-Agent: quilt/0.63-1
> 
> 3.15-stable review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Minchan Kim <minchan@...nel.org>
> 
> commit 2e32baea46ce542c561a519414c840295b229c8f upstream.
> 
> Alexander reported mkswap on /dev/zram0 is failed if other process is
> opening the block device file.
> 
> Step is as follows,
> 
> 0. Reset the unused zram device.
> 1. Use a program that opens /dev/zram0 with O_RDWR and sleeps
>    until killed.
> 2. While that program sleeps, echo the correct value to
>    /sys/block/zram0/disksize.
> 3. Verify (e.g. in /proc/partitions) that the disk size is applied
>    correctly. It is.
> 4. While that program still sleeps, attempt to mkswap /dev/zram0.
>    This fails: mkswap: error: swap area needs to be at least 40 KiB
> 
> When I investigated, the size get by ioctl(fd, BLKGETSIZE64, xxx) on
> mkswap to get a size of blockdev was zero although zram0 has right size by
> 2.
> 
> The reason is zram didn't revalidate disk after changing capacity so that
> size of blockdev's inode is not uptodate until all of file is close.
> 
> This patch should fix the BUG.
> 
> Signed-off-by: Minchan Kim <minchan@...nel.org>
> Reported-by: Alexander E. Patrakov <patrakov@...il.com>
> Tested-by: Alexander E. Patrakov <patrakov@...il.com>
> Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
> Cc: Nitin Gupta <ngupta@...are.org>
> Acked-by: Jerome Marchand <jmarchan@...hat.com>
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

Hello,

this patch is known to cause problems. please see
https://lkml.org/lkml/2014/7/3/885

	-ss


> ---
>  drivers/block/zram/zram_drv.c |    5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -622,8 +622,10 @@ static void zram_reset_device(struct zra
>  	memset(&zram->stats, 0, sizeof(zram->stats));
>  
>  	zram->disksize = 0;
> -	if (reset_capacity)
> +	if (reset_capacity) {
>  		set_capacity(zram->disk, 0);
> +		revalidate_disk(zram->disk);
> +	}
>  	up_write(&zram->init_lock);
>  }
>  
> @@ -664,6 +666,7 @@ static ssize_t disksize_store(struct dev
>  	zram->comp = comp;
>  	zram->disksize = disksize;
>  	set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT);
> +	revalidate_disk(zram->disk);
>  	up_write(&zram->init_lock);
>  	return len;
>  
> 
> 
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