Re: [PATCH v2] mm, swap: disallow swapon() on zoned block devices

From: Christoph Hellwig <hch@infradead.org>
To: Naohiro Aota <naohiro.aota@wdc.com>
Cc: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
	linux-block@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH v2] mm, swap: disallow swapon() on zoned block devices
Date: Tue, 15 Oct 2019 02:06:41 -0700	[thread overview]
Message-ID: <20191015090641.GB7199@infradead.org> (raw)
In-Reply-To: <20191015085814.637837-1-naohiro.aota@wdc.com>

On Tue, Oct 15, 2019 at 05:58:14PM +0900, Naohiro Aota wrote:
> A zoned block device consists of a number of zones. Zones are either
> conventional and accepting random writes or sequential and requiring that
> writes be issued in LBA order from each zone write pointer position. For
> the write restriction, zoned block devices are not suitable for a swap
> device. Disallow swapon on them.
> 
> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
> ---
> v2: add comments according to Christoph's feedback, reformat chengelog.
> ---
>  mm/swapfile.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index dab43523afdd..f2c4224d1f8a 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -2887,6 +2887,14 @@ static int claim_swapfile(struct swap_info_struct *p, struct inode *inode)
>  		error = set_blocksize(p->bdev, PAGE_SIZE);
>  		if (error < 0)
>  			return error;
> +		/*
> +		 * Zoned block device contains zones that have
> +		 * sequential write only restriction. For the restriction,
> +		 * zoned block devices are not suitable for a swap device.
> +		 * Disallow them here.
> +		 */
> +		if (blk_queue_is_zoned(p->bdev->bd_queue))

Please use up all 80 chars per line  Otherwise this looks fine:

Reviewed-by: Christoph Hellwig <hch@lst.de>