linux-kernel - Re: [PATCH] virtio_blk: fix incorrect message when disk is resized

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Date:   Fri, 4 Aug 2017 10:37:54 +0100
From:   Stefan Hajnoczi <stefanha@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Jason Wang <jasowang@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH] virtio_blk: fix incorrect message when disk is resized

On Wed, Jul 26, 2017 at 03:32:23PM +0100, Stefan Hajnoczi wrote:
> The message printed on disk resize is incorrect.  The following is
> printed when resizing to 2 GiB:
> 
>   $ truncate -s 1G test.img
>   $ qemu -device virtio-blk-pci,logical_block_size=4096,...
>   (qemu) block_resize drive1 2G
> 
>   virtio_blk virtio0: new size: 4194304 4096-byte logical blocks (17.2 GB/16.0 GiB)
> 
> The virtio_blk capacity config field is in 512-byte sector units
> regardless of logical_block_size as per the VIRTIO specification.
> Therefore the message should read:
> 
>   virtio_blk virtio0: new size: 524288 4096-byte logical blocks (2.15 GB/2.0 GiB)
> 
> Note that this only affects the printed message.  Thankfully the actual
> block device has the correct size because the block layer expects
> capacity in sectors.
> 
> Signed-off-by: Stefan Hajnoczi <stefanha@...hat.com>
> ---
>  drivers/block/virtio_blk.c | 16 ++++++++++------
>  1 file changed, 10 insertions(+), 6 deletions(-)

Ping?

> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> index 4e02aa5fdac0..69a2d1748743 100644
> --- a/drivers/block/virtio_blk.c
> +++ b/drivers/block/virtio_blk.c
> @@ -381,6 +381,7 @@ static void virtblk_config_changed_work(struct work_struct *work)
>  	struct request_queue *q = vblk->disk->queue;
>  	char cap_str_2[10], cap_str_10[10];
>  	char *envp[] = { "RESIZE=1", NULL };
> +	unsigned long long nblocks;
>  	u64 capacity;
>  
>  	/* Host must always specify the capacity. */
> @@ -393,16 +394,19 @@ static void virtblk_config_changed_work(struct work_struct *work)
>  		capacity = (sector_t)-1;
>  	}
>  
> -	string_get_size(capacity, queue_logical_block_size(q),
> +	nblocks = DIV_ROUND_UP_ULL(capacity, queue_logical_block_size(q) >> 9);
> +
> +	string_get_size(nblocks, queue_logical_block_size(q),
>  			STRING_UNITS_2, cap_str_2, sizeof(cap_str_2));
> -	string_get_size(capacity, queue_logical_block_size(q),
> +	string_get_size(nblocks, queue_logical_block_size(q),
>  			STRING_UNITS_10, cap_str_10, sizeof(cap_str_10));
>  
>  	dev_notice(&vdev->dev,
> -		  "new size: %llu %d-byte logical blocks (%s/%s)\n",
> -		  (unsigned long long)capacity,
> -		  queue_logical_block_size(q),
> -		  cap_str_10, cap_str_2);
> +		   "new size: %llu %d-byte logical blocks (%s/%s)\n",
> +		   nblocks,
> +		   queue_logical_block_size(q),
> +		   cap_str_10,
> +		   cap_str_2);
>  
>  	set_capacity(vblk->disk, capacity);
>  	revalidate_disk(vblk->disk);
> -- 
> 2.13.3
> 

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