On 12/14/2010 04:12 PM, Jeremy Fitzhardinge wrote:
> On 12/14/2010 06:55 AM, Daniel De Graaf wrote:
>> 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.
>
> Does anyone use this ioctl? Wouldn't it be safer to replace it with a
> no-op version?
>
> J
>
I do not know of any users. If it's preferred to replace with a noop ioctl
instead of the current -ENOSYS return, that's easy to do.
>> Signed-off-by: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>
>> ---
>> drivers/xen/gntdev.c | 48 ++++++++++++++----------------------------------
>> 1 files changed, 14 insertions(+), 34 deletions(-)
>>
>> diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
>> index c582804..62639af 100644
>> --- a/drivers/xen/gntdev.c
>> +++ b/drivers/xen/gntdev.c
>> @@ -44,13 +44,12 @@ MODULE_DESCRIPTION("User-space granted page access
>> driver");
>>
>> static int debug = 0;
>> module_param(debug, int, 0644);
>> -static int limit = 1024;
>> +static int limit = 1024*1024;
>> module_param(limit, int, 0644);
>> +static atomic_t pages_mapped = ATOMIC_INIT(0);
>>
>> struct gntdev_priv {
>> struct list_head maps;
>> - uint32_t used;
>> - uint32_t limit;
>> spinlock_t lock;
>> struct mm_struct *mm;
>> struct mmu_notifier mn;
>> @@ -76,8 +75,8 @@ static void gntdev_print_maps(struct gntdev_priv *priv,
>> {
>> struct grant_map *map;
>>
>> - printk("%s: maps list (priv %p, usage %d/%d)\n",
>> - __FUNCTION__, priv, priv->used, priv->limit);
>> + printk("%s: maps list (priv %p)\n",
>> + __FUNCTION__, priv);
>> list_for_each_entry(map, &priv->maps, next)
>> printk(" index %2d, count %2d %s\n",
>> map->index, map->count,
>> @@ -104,9 +103,6 @@ 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:
>> @@ -131,7 +127,6 @@ 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;
>> if (debug)
>> gntdev_print_maps(priv, "[new]", add->index);
>> }
>> @@ -178,7 +173,7 @@ 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;
>> }
>> @@ -360,7 +355,6 @@ 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) {
>> @@ -416,19 +410,26 @@ static long gntdev_ioctl_map_grant_ref(struct
>> gntdev_priv *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))
>> + {
>> + if (debug)
>> + printk("%s: can't map: over limit\n", __FUNCTION__);
>> + gntdev_free_map(map);
>> + return err;
>> + }
>> +
>> spin_lock(&priv->lock);
>> gntdev_add_map(priv, map);
>> op.index = map->index << PAGE_SHIFT;
>> @@ -495,24 +496,6 @@ 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;
>> - if (debug)
>> - printk("%s: priv %p, limit %d\n", __FUNCTION__, priv, op.count);
>> - if (op.count > limit)
>> - return -EINVAL;
>> -
>> - 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)
>> {
>> @@ -529,9 +512,6 @@ 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:
>> if (debug)
>> printk("%s: priv %p, unknown cmd %x\n",
>
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