WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

[Xen-devel] [PATCH 1/6] xen-gntdev: Change page limit to be global inste

To: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-devel] [PATCH 1/6] xen-gntdev: Change page limit to be global instead of per-open
From: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>
Date: Thu, 3 Feb 2011 12:18:59 -0500
Cc: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>, jeremy@xxxxxxxx, Ian.Campbell@xxxxxxxxxx, konrad.wilk@xxxxxxxxxx
Delivery-date: Thu, 03 Feb 2011 09:25:05 -0800
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <1296753544-13323-1-git-send-email-dgdegra@xxxxxxxxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
References: <1296753544-13323-1-git-send-email-dgdegra@xxxxxxxxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
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@xxxxxxxxxxxxx>
---
 drivers/xen/gntdev.c |   50 ++++++++++++++------------------------------------
 1 files changed, 14 insertions(+), 36 deletions(-)

diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index 2b777c0..3ca47d1 100644
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -45,15 +45,15 @@ MODULE_AUTHOR("Derek G. Murray <Derek.Murray@xxxxxxxxxxxx>, 
"
              "Gerd Hoffmann <kraxel@xxxxxxxxxx>");
 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;
 }
@@ -385,7 +379,6 @@ 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) {
@@ -442,19 +435,24 @@ 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;
@@ -517,23 +515,6 @@ 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)
 {
@@ -550,9 +531,6 @@ 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;
-- 
1.7.3.4


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel

<Prev in Thread] Current Thread [Next in Thread>