Commit 9246b5f0 authored by Chris Lalancette's avatar Chris Lalancette Committed by Jens Axboe
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block: Expand Xen blkfront for > 16 xvd 



Until recently, the maximum number of xvd block devices you could attach
to a Xen domU was 16. This limitation turned out to be problematic for
some users, so it was expanded to handle a much larger number of disks.
However, this requires a couple of changes in the way that blkfront
scans for disks. This functionality is already present in the Xen
linux-2.6.18-xen.hg tree; the attached patch adds this functionality to
the mainline xen-blkfront implementation. I successfully tested it on a
2.6.25 tree, and build tested it on 2.6.27-rc3.

Signed-off-by: default avatarChris Lalancette <clalance@redhat.com>
Acked-by: default avatarJeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent 9c02f2b0

drivers/block/xen-blkfront.c

+55 −21
Original line number Diff line number Diff line
@@ -105,15 +105,17 @@ static DEFINE_SPINLOCK(blkif_io_lock); 
#define GRANT_INVALID_REF	0



#define PARTS_PER_DISK		16

#define PARTS_PER_EXT_DISK      256



#define BLKIF_MAJOR(dev) ((dev)>>8)

#define BLKIF_MINOR(dev) ((dev) & 0xff)



#define DEV_NAME	"xvd"	/* name in /dev */

#define EXT_SHIFT 28

#define EXTENDED (1<<EXT_SHIFT)

#define VDEV_IS_EXTENDED(dev) ((dev)&(EXTENDED))

#define BLKIF_MINOR_EXT(dev) ((dev)&(~EXTENDED))



/* Information about our VBDs. */

#define MAX_VBDS 64

static LIST_HEAD(vbds_list);

#define DEV_NAME	"xvd"	/* name in /dev */



static int get_id_from_freelist(struct blkfront_info *info)

{
@@ -386,31 +388,60 @@ static int xlvbd_barrier(struct blkfront_info *info) 
}





static int xlvbd_alloc_gendisk(int minor, blkif_sector_t capacity,

			       int vdevice, u16 vdisk_info, u16 sector_size,

			       struct blkfront_info *info)

static int xlvbd_alloc_gendisk(blkif_sector_t capacity,

			       struct blkfront_info *info,

			       u16 vdisk_info, u16 sector_size)

{

	struct gendisk *gd;

	int nr_minors = 1;

	int err = -ENODEV;

	unsigned int offset;

	int minor;

	int nr_parts;



	BUG_ON(info->gd != NULL);

	BUG_ON(info->rq != NULL);



	if ((minor % PARTS_PER_DISK) == 0)

		nr_minors = PARTS_PER_DISK;

	if ((info->vdevice>>EXT_SHIFT) > 1) {

		/* this is above the extended range; something is wrong */

		printk(KERN_WARNING "blkfront: vdevice 0x%x is above the extended range; ignoring\n", info->vdevice);

		return -ENODEV;

	}



	if (!VDEV_IS_EXTENDED(info->vdevice)) {

		minor = BLKIF_MINOR(info->vdevice);

		nr_parts = PARTS_PER_DISK;

	} else {

		minor = BLKIF_MINOR_EXT(info->vdevice);

		nr_parts = PARTS_PER_EXT_DISK;

	}



	if ((minor % nr_parts) == 0)

		nr_minors = nr_parts;



	gd = alloc_disk(nr_minors);

	if (gd == NULL)

		goto out;



	if (nr_minors > 1)

		sprintf(gd->disk_name, "%s%c", DEV_NAME,

			'a' + minor / PARTS_PER_DISK);

	offset = minor / nr_parts;



	if (nr_minors > 1) {

		if (offset < 26)

			sprintf(gd->disk_name, "%s%c", DEV_NAME, 'a' + offset);

		else

			sprintf(gd->disk_name, "%s%c%c", DEV_NAME,

				'a' + ((offset / 26)-1), 'a' + (offset % 26));

	} else {

		if (offset < 26)

			sprintf(gd->disk_name, "%s%c%d", DEV_NAME,

			'a' + minor / PARTS_PER_DISK,

			minor % PARTS_PER_DISK);

				'a' + offset,

				minor & (nr_parts - 1));

		else

			sprintf(gd->disk_name, "%s%c%c%d", DEV_NAME,

				'a' + ((offset / 26) - 1),

				'a' + (offset % 26),

				minor & (nr_parts - 1));

	}



	gd->major = XENVBD_MAJOR;

	gd->first_minor = minor;
@@ -698,10 +729,15 @@ static int blkfront_probe(struct xenbus_device *dev, 
	/* FIXME: Use dynamic device id if this is not set. */

	err = xenbus_scanf(XBT_NIL, dev->nodename,

			   "virtual-device", "%i", &vdevice);

	if (err != 1) {

		/* go looking in the extended area instead */

		err = xenbus_scanf(XBT_NIL, dev->nodename, "virtual-device-ext",

				   "%i", &vdevice);

		if (err != 1) {

			xenbus_dev_fatal(dev, err, "reading virtual-device");

			return err;

		}

	}



	info = kzalloc(sizeof(*info), GFP_KERNEL);

	if (!info) {
@@ -861,9 +897,7 @@ static void blkfront_connect(struct blkfront_info *info) 
	if (err)

		info->feature_barrier = 0;



	err = xlvbd_alloc_gendisk(BLKIF_MINOR(info->vdevice),

				  sectors, info->vdevice,

				  binfo, sector_size, info);

	err = xlvbd_alloc_gendisk(sectors, info, binfo, sector_size);

	if (err) {

		xenbus_dev_fatal(info->xbdev, err, "xlvbd_add at %s",

				 info->xbdev->otherend);

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