Re: [PATCH 3/7] xen-blkfront: handle Xen major numbers other than XENVBD

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Wed, Feb 16, 2011 at 05:53:03PM +0000, stefano.stabellini@eu.citrix.com wrote:
> From: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> 
> This patch makes sure blkfront handles correctly virtual device numbers
> corresponding to Xen emulated IDE and SCSI disks: in those cases
> blkfront translates the major number to XENVBD and the minor number to a
> low xvd minor.
> 
> Note: this behaviour is different from what old xenlinux PV guests used
> to do: they used to steal an IDE or SCSI major number and use it
> instead.
> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> Acked-by: Jeremy Fitzhardinge <jeremy@goop.org>
> ---
>  drivers/block/xen-blkfront.c     |   79 +++++++++++++++++++++++++++++++++++--
>  include/xen/interface/io/blkif.h |   21 ++++++++++
>  2 files changed, 95 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
> index d7aa39e..64d9c6d 100644
> --- a/drivers/block/xen-blkfront.c
> +++ b/drivers/block/xen-blkfront.c
> @@ -120,6 +120,10 @@ static DEFINE_SPINLOCK(minor_lock);
>  #define EXTENDED (1<<EXT_SHIFT)
>  #define VDEV_IS_EXTENDED(dev) ((dev)&(EXTENDED))
>  #define BLKIF_MINOR_EXT(dev) ((dev)&(~EXTENDED))
> +#define EMULATED_HD_DISK_MINOR_OFFSET (0)
> +#define EMULATED_HD_DISK_NAME_OFFSET (EMULATED_HD_DISK_MINOR_OFFSET / 256)

0 / 256 ? Why not just 0?

> +#define EMULATED_SD_DISK_MINOR_OFFSET (EMULATED_HD_DISK_MINOR_OFFSET + (4 * 16))
> +#define EMULATED_SD_DISK_NAME_OFFSET (EMULATED_HD_DISK_NAME_OFFSET + 4)
>  
>  #define DEV_NAME	"xvd"	/* name in /dev */
>  
> @@ -434,6 +438,65 @@ static void xlvbd_flush(struct blkfront_info *info)
>  	       info->feature_flush ? "enabled" : "disabled");
>  }
>  
> +static int xen_translate_vdev(int vdevice, int *minor, unsigned int *offset)
> +{
> +	int major;
> +	major = BLKIF_MAJOR(vdevice);
> +	*minor = BLKIF_MINOR(vdevice);
> +	switch (major) {
> +		case XEN_IDE0_MAJOR:
> +			*offset = (*minor / 64) + EMULATED_HD_DISK_NAME_OFFSET;
> +			*minor = ((*minor / 64) * PARTS_PER_DISK) +
> +				EMULATED_HD_DISK_MINOR_OFFSET;
> +			break;
> +		case XEN_IDE1_MAJOR:
> +			*offset = (*minor / 64) + 2 + EMULATED_HD_DISK_NAME_OFFSET;
> +			*minor = (((*minor / 64) + 2) * PARTS_PER_DISK) +
> +				EMULATED_HD_DISK_MINOR_OFFSET;
> +			break;
> +		case XEN_SCSI_DISK0_MAJOR:
> +			*offset = (*minor / PARTS_PER_DISK) + EMULATED_SD_DISK_NAME_OFFSET;
> +			*minor = *minor + EMULATED_SD_DISK_MINOR_OFFSET;
> +			break;
> +		case XEN_SCSI_DISK1_MAJOR:
> +		case XEN_SCSI_DISK2_MAJOR:
> +		case XEN_SCSI_DISK3_MAJOR:
> +		case XEN_SCSI_DISK4_MAJOR:
> +		case XEN_SCSI_DISK5_MAJOR:
> +		case XEN_SCSI_DISK6_MAJOR:
> +		case XEN_SCSI_DISK7_MAJOR:
> +			*offset = (*minor / PARTS_PER_DISK) + 
> +				((major - XEN_SCSI_DISK1_MAJOR + 1) * 16) +
> +				EMULATED_SD_DISK_NAME_OFFSET;
> +			*minor = *minor +
> +				((major - XEN_SCSI_DISK1_MAJOR + 1) * 16 * PARTS_PER_DISK) +
> +				EMULATED_SD_DISK_MINOR_OFFSET;
> +			break;
> +		case XEN_SCSI_DISK8_MAJOR:
> +		case XEN_SCSI_DISK9_MAJOR:
> +		case XEN_SCSI_DISK10_MAJOR:
> +		case XEN_SCSI_DISK11_MAJOR:
> +		case XEN_SCSI_DISK12_MAJOR:
> +		case XEN_SCSI_DISK13_MAJOR:
> +		case XEN_SCSI_DISK14_MAJOR:
> +		case XEN_SCSI_DISK15_MAJOR:
> +			*offset = (*minor / PARTS_PER_DISK) + 
> +				((major - XEN_SCSI_DISK8_MAJOR + 8) * 16) +
> +				EMULATED_SD_DISK_NAME_OFFSET;
> +			*minor = *minor +
> +				((major - XEN_SCSI_DISK8_MAJOR + 8) * 16 * PARTS_PER_DISK) +
> +				EMULATED_SD_DISK_MINOR_OFFSET;
> +			break;
> +		case XENVBD_MAJOR:
> +			*offset = *minor / PARTS_PER_DISK;
> +			break;
> +		default:
> +			printk(KERN_WARNING "blkfront: your disk configuration is "
> +					"incorrect, please use an xvd device instead\n");
> +			return -ENODEV;
> +	}
> +	return 0;
> +}
>  
>  static int xlvbd_alloc_gendisk(blkif_sector_t capacity,
>  			       struct blkfront_info *info,
> @@ -441,7 +504,7 @@ static int xlvbd_alloc_gendisk(blkif_sector_t capacity,
>  {
>  	struct gendisk *gd;
>  	int nr_minors = 1;
> -	int err = -ENODEV;
> +	int err;
>  	unsigned int offset;
>  	int minor;
>  	int nr_parts;
> @@ -456,12 +519,20 @@ static int xlvbd_alloc_gendisk(blkif_sector_t capacity,
>  	}
>  
>  	if (!VDEV_IS_EXTENDED(info->vdevice)) {
> -		minor = BLKIF_MINOR(info->vdevice);
> -		nr_parts = PARTS_PER_DISK;
> +		err = xen_translate_vdev(info->vdevice, &minor, &offset);
> +		if (err)
> +			return err;		
> + 		nr_parts = PARTS_PER_DISK;
>  	} else {
>  		minor = BLKIF_MINOR_EXT(info->vdevice);
>  		nr_parts = PARTS_PER_EXT_DISK;
> +		offset = minor / nr_parts;
> +		if (xen_hvm_domain() && offset <= EMULATED_HD_DISK_NAME_OFFSET + 4)
> +			printk(KERN_WARNING "blkfront: vdevice 0x%x might conflict with "
> +					"emulated IDE disks,\n\t choose an xvd device name"
> +					"from xvde on\n", info->vdevice);
>  	}
> +	err = -ENODEV;
>  
>  	if ((minor % nr_parts) == 0)
>  		nr_minors = nr_parts;
> @@ -475,8 +546,6 @@ static int xlvbd_alloc_gendisk(blkif_sector_t capacity,
>  	if (gd == NULL)
>  		goto release;
>  
> -	offset = minor / nr_parts;
> -
>  	if (nr_minors > 1) {
>  		if (offset < 26)
>  			sprintf(gd->disk_name, "%s%c", DEV_NAME, 'a' + offset);
> diff --git a/include/xen/interface/io/blkif.h b/include/xen/interface/io/blkif.h
> index c2d1fa4..68dd2b4 100644
> --- a/include/xen/interface/io/blkif.h
> +++ b/include/xen/interface/io/blkif.h
> @@ -91,4 +91,25 @@ DEFINE_RING_TYPES(blkif, struct blkif_request, struct blkif_response);
>  #define VDISK_REMOVABLE    0x2
>  #define VDISK_READONLY     0x4
>  
> +/* Xen-defined major numbers for virtual disks, they look strangely
> + * familiar */
> +#define XEN_IDE0_MAJOR	3
> +#define XEN_IDE1_MAJOR	22
> +#define XEN_SCSI_DISK0_MAJOR	8
> +#define XEN_SCSI_DISK1_MAJOR	65
> +#define XEN_SCSI_DISK2_MAJOR	66
> +#define XEN_SCSI_DISK3_MAJOR	67
> +#define XEN_SCSI_DISK4_MAJOR	68
> +#define XEN_SCSI_DISK5_MAJOR	69
> +#define XEN_SCSI_DISK6_MAJOR	70
> +#define XEN_SCSI_DISK7_MAJOR	71
> +#define XEN_SCSI_DISK8_MAJOR	128
> +#define XEN_SCSI_DISK9_MAJOR	129
> +#define XEN_SCSI_DISK10_MAJOR	130
> +#define XEN_SCSI_DISK11_MAJOR	131
> +#define XEN_SCSI_DISK12_MAJOR	132
> +#define XEN_SCSI_DISK13_MAJOR	133
> +#define XEN_SCSI_DISK14_MAJOR	134
> +#define XEN_SCSI_DISK15_MAJOR	135
> +
>  #endif /* __XEN_PUBLIC_IO_BLKIF_H__ */
> -- 
> 1.5.6.5