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: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index 1e31cdc..23d208a 100644
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -45,15 +45,15 @@
"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 @@
#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 @@
add->count = count;
add->priv = priv;
- if (add->count + priv->used > priv->limit)
- goto err;
-
return add;
err:
@@ -154,7 +149,6 @@
list_add_tail(&add->next, &priv->maps);
done:
- priv->used += add->count;
gntdev_print_maps(priv, "[new]", add->index);
}
@@ -200,7 +194,7 @@
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 @@
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 @@
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 @@
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 @@
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;