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

On Wed, Feb 16, 2011 at 05:53:03PM +0000, stefano.stabellini@xxxxxxxxxxxxx 
wrote:
> From: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> 
> 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@xxxxxxxxxxxxx>
> Acked-by: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
> ---
>  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

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