linux-kernel - Re: [PATCH] virtio_blk: Add help function to format mass of disks

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Message-ID: <4F8430DA.2010608@redhat.com>
Date:	Tue, 10 Apr 2012 21:08:42 +0800
From:	Asias He <asias@...hat.com>
To:	Ren Mingxin <renmx@...fujitsu.com>
CC:	mst@...hat.com, rusty@...tcorp.com.au, axboe@...nel.dk,
	tj@...nel.org, James.Bottomley@...senPartnership.com,
	asamymuthupa@...ron.com, linux-kernel@...r.kernel.org,
	linux-scsi@...r.kernel.org, kvm@...r.kernel.org,
	virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH] virtio_blk: Add help function to format mass of disks

On 04/10/2012 03:28 PM, Ren Mingxin wrote:
> The current virtio block's naming algorithm just supports 18278
> (26^3 + 26^2 + 26) disks. If there are mass of virtio blocks,
> there will be disks with the same name.
>
> Based on commit 3e1a7ff8a0a7b948f2684930166954f9e8e776fe, I add
> function "virtblk_name_format()" for virtio block to support mass
> of disks naming.
>
> Signed-off-by: Ren Mingxin<renmx@...fujitsu.com>

Make sense to me.

Acked-by: Asias He <asias@...hat.com>

> ---
>   drivers/block/virtio_blk.c |   38 ++++++++++++++++++++++++++------------
>   1 files changed, 26 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> index c4a60ba..86516c8 100644
> --- a/drivers/block/virtio_blk.c
> +++ b/drivers/block/virtio_blk.c
> @@ -374,6 +374,31 @@ static int init_vq(struct virtio_blk *vblk)
>   	return err;
>   }
>
> +static int virtblk_name_format(char *prefix, int index, char *buf, int buflen)
> +{
> +	const int base = 'z' - 'a' + 1;
> +	char *begin = buf + strlen(prefix);
> +	char *begin = buf + strlen(prefix);
> +	char *end = buf + buflen;
> +	char *p;
> +	int unit;
> +
> +	p = end - 1;
> +	*p = '\0';
> +	unit = base;
> +	do {
> +		if (p == begin)
> +			return -EINVAL;
> +		*--p = 'a' + (index % unit);
> +		index = (index / unit) - 1;
> +	} while (index>= 0);
> +
> +	memmove(begin, p, end - p);
> +	memcpy(buf, prefix, strlen(prefix));
> +
> +	return 0;
> +}
> +
>   static int __devinit virtblk_probe(struct virtio_device *vdev)
>   {
>   	struct virtio_blk *vblk;
> @@ -442,18 +467,7 @@ static int __devinit virtblk_probe(struct virtio_device *vdev)
>
>   	q->queuedata = vblk;
>
> -	if (index<  26) {
> -		sprintf(vblk->disk->disk_name, "vd%c", 'a' + index % 26);
> -	} else if (index<  (26 + 1) * 26) {
> -		sprintf(vblk->disk->disk_name, "vd%c%c",
> -			'a' + index / 26 - 1, 'a' + index % 26);
> -	} else {
> -		const unsigned int m1 = (index / 26 - 1) / 26 - 1;
> -		const unsigned int m2 = (index / 26 - 1) % 26;
> -		const unsigned int m3 =  index % 26;
> -		sprintf(vblk->disk->disk_name, "vd%c%c%c",
> -			'a' + m1, 'a' + m2, 'a' + m3);
> -	}
> +	virtblk_name_format("vd", index, vblk->disk->disk_name, DISK_NAME_LEN);
>
>   	vblk->disk->major = major;
>   	vblk->disk->first_minor = index_to_minor(index);


-- 
Asias
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