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Commit ef91082e authored by Daniel De Graaf's avatar Daniel De Graaf Committed by Konrad Rzeszutek Wilk
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xen-gntdev: Change page limit to be global instead of per-open 



Because there is no limitation on how many times a user can open a
given device file, an per-file-description limit on the number of
pages granted offers little to no benefit. Change to a global limit
and remove the ioctl() as the parameter can now be changed via sysfs.

Xen tools changeset 22768:f8d801e5573e is needed to eliminate the
error this change produces in xc_gnttab_set_max_grants.

Signed-off-by: default avatarDaniel De Graaf <dgdegra@tycho.nsa.gov>
Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
parent 100b33c8

drivers/xen/gntdev.c

+14 −36
Original line number Diff line number Diff line
@@ -45,15 +45,15 @@ MODULE_AUTHOR("Derek G. Murray <Derek.Murray@cl.cam.ac.uk>, " 
	      "Gerd Hoffmann <kraxel@redhat.com>");

MODULE_DESCRIPTION("User-space granted page access driver");



static int limit = 1024;

static int limit = 1024*1024;

module_param(limit, int, 0644);

MODULE_PARM_DESC(limit, "Maximum number of grants that may be mapped at "

		"once by a gntdev instance");

MODULE_PARM_DESC(limit, "Maximum number of grants that may be mapped by "

		"the gntdev device");



static atomic_t pages_mapped = ATOMIC_INIT(0);



struct gntdev_priv {

	struct list_head maps;

	uint32_t used;

	uint32_t limit;

	/* lock protects maps from concurrent changes */

	spinlock_t lock;

	struct mm_struct *mm;
@@ -82,9 +82,7 @@ static void gntdev_print_maps(struct gntdev_priv *priv, 
#ifdef DEBUG

	struct grant_map *map;



	pr_debug("maps list (priv %p, usage %d/%d)\n",

	       priv, priv->used, priv->limit);



	pr_debug("%s: maps list (priv %p)\n", __func__, priv);

	list_for_each_entry(map, &priv->maps, next)

		pr_debug("  index %2d, count %2d %s\n",

		       map->index, map->count,
@@ -121,9 +119,6 @@ static struct grant_map *gntdev_alloc_map(struct gntdev_priv *priv, int count) 
	add->count = count;

	add->priv  = priv;



	if (add->count + priv->used > priv->limit)

		goto err;



	return add;



err:
@@ -154,7 +149,6 @@ static void gntdev_add_map(struct gntdev_priv *priv, struct grant_map *add) 
	list_add_tail(&add->next, &priv->maps);



done:

	priv->used += add->count;

	gntdev_print_maps(priv, "[new]", add->index);

}
@@ -200,7 +194,7 @@ static int gntdev_del_map(struct grant_map *map) 
		if (map->unmap_ops[i].handle)

			return -EBUSY;



	map->priv->used -= map->count;

	atomic_sub(map->count, &pages_mapped);

	list_del(&map->next);

	return 0;

}
@@ -386,7 +380,6 @@ static int gntdev_open(struct inode *inode, struct file *flip) 


	INIT_LIST_HEAD(&priv->maps);

	spin_lock_init(&priv->lock);

	priv->limit = limit;



	priv->mm = get_task_mm(current);

	if (!priv->mm) {
@@ -443,19 +436,24 @@ static long gntdev_ioctl_map_grant_ref(struct gntdev_priv *priv, 
	pr_debug("priv %p, add %d\n", priv, op.count);

	if (unlikely(op.count <= 0))

		return -EINVAL;

	if (unlikely(op.count > priv->limit))

		return -EINVAL;



	err = -ENOMEM;

	map = gntdev_alloc_map(priv, op.count);

	if (!map)

		return err;



	if (copy_from_user(map->grants, &u->refs,

			   sizeof(map->grants[0]) * op.count) != 0) {

		gntdev_free_map(map);

		return err;

	}



	if (unlikely(atomic_add_return(op.count, &pages_mapped) > limit)) {

		pr_debug("can't map: over limit\n");

		gntdev_free_map(map);

		return err;

	}



	spin_lock(&priv->lock);

	gntdev_add_map(priv, map);

	op.index = map->index << PAGE_SHIFT;
@@ -518,23 +516,6 @@ static long gntdev_ioctl_get_offset_for_vaddr(struct gntdev_priv *priv, 
	return 0;

}



static long gntdev_ioctl_set_max_grants(struct gntdev_priv *priv,

					struct ioctl_gntdev_set_max_grants __user *u)

{

	struct ioctl_gntdev_set_max_grants op;



	if (copy_from_user(&op, u, sizeof(op)) != 0)

		return -EFAULT;

	pr_debug("priv %p, limit %d\n", priv, op.count);

	if (op.count > limit)

		return -E2BIG;



	spin_lock(&priv->lock);

	priv->limit = op.count;

	spin_unlock(&priv->lock);

	return 0;

}



static long gntdev_ioctl(struct file *flip,

			 unsigned int cmd, unsigned long arg)

{
@@ -551,9 +532,6 @@ static long gntdev_ioctl(struct file *flip, 
	case IOCTL_GNTDEV_GET_OFFSET_FOR_VADDR:

		return gntdev_ioctl_get_offset_for_vaddr(priv, ptr);



	case IOCTL_GNTDEV_SET_MAX_GRANTS:

		return gntdev_ioctl_set_max_grants(priv, ptr);



	default:

		pr_debug("priv %p, unknown cmd %x\n", priv, cmd);

		return -ENOIOCTLCMD;