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[Xen-devel] [PATCH 4/6] xen-gntdev: Use find_vma rather than iterating our vma list manually



This should be faster if many mappings exist, and also removes
the only user of vma that is not related to PTE modification.

Signed-off-by: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>
---
 drivers/xen/gntdev.c |   34 ++++++++++------------------------
 1 files changed, 10 insertions(+), 24 deletions(-)

diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index 773b76c..a73f07c 100644
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -74,6 +74,8 @@ struct grant_map {
        struct granted_page pages[0];
 };
 
+static struct vm_operations_struct gntdev_vmops;
+
 /* ------------------------------------------------------------------ */
 
 static void gntdev_print_maps(struct gntdev_priv *priv,
@@ -142,23 +144,6 @@ static struct grant_map *gntdev_find_map_index(struct 
gntdev_priv *priv, int ind
        return NULL;
 }
 
-static struct grant_map *gntdev_find_map_vaddr(struct gntdev_priv *priv,
-                                              unsigned long vaddr)
-{
-       struct grant_map *map;
-
-       list_for_each_entry(map, &priv->maps, next) {
-               if (!map->vma)
-                       continue;
-               if (vaddr < map->vma->vm_start)
-                       continue;
-               if (vaddr >= map->vma->vm_end)
-                       continue;
-               return map;
-       }
-       return NULL;
-}
-
 static int gntdev_del_map(struct grant_map *map)
 {
        int i;
@@ -510,6 +495,7 @@ static long gntdev_ioctl_get_offset_for_vaddr(struct 
gntdev_priv *priv,
                                              struct 
ioctl_gntdev_get_offset_for_vaddr __user *u)
 {
        struct ioctl_gntdev_get_offset_for_vaddr op;
+       struct vm_area_struct *vma;
        struct grant_map *map;
 
        if (copy_from_user(&op, u, sizeof(op)) != 0)
@@ -518,16 +504,16 @@ static long gntdev_ioctl_get_offset_for_vaddr(struct 
gntdev_priv *priv,
                printk("%s: priv %p, offset for vaddr %lx\n", __FUNCTION__, 
priv,
                       (unsigned long)op.vaddr);
 
-       spin_lock(&priv->lock);
-       map = gntdev_find_map_vaddr(priv, op.vaddr);
-       if (map == NULL ||
-           map->vma->vm_start != op.vaddr) {
-               spin_unlock(&priv->lock);
+       vma = find_vma(current->mm, op.vaddr);
+       if (!vma)
                return -EINVAL;
-       }
+
+       map = vma->vm_private_data;
+       if (vma->vm_ops != &gntdev_vmops || !map)
+               return -EINVAL;
+
        op.offset = map->index << PAGE_SHIFT;
        op.count = map->count;
-       spin_unlock(&priv->lock);
 
        if (copy_to_user(u, &op, sizeof(op)) != 0)
                return -EFAULT;
-- 
1.7.2.3


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