On Tue, 2010-12-14 at 21:42 +0000, Daniel De Graaf wrote:
> 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.
It's called by xc_gnttab_set_max_grants in libxc, although I don't see
any callers of that function.
We should probably also remove the library function.
Ian.
> >> 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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