xen/gntalloc: Change gref_lock to a mutex

The event channel release function cannot be called under a spinlock
because it can attempt to acquire a mutex due to the event channel
reference acquired when setting up unmap notifications.

Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 21 insertions, 20 deletions

diff --git a/drivers/xen/gntalloc.c b/drivers/xen/gntalloc.c
index f6832f46aea..439352d094d 100644
--- a/drivers/xen/gntalloc.c
+++ b/drivers/xen/gntalloc.c
@@ -74,7 +74,7 @@ MODULE_PARM_DESC(limit, "Maximum number of grants that may be allocated by "
                 "the gntalloc device");
 
 static LIST_HEAD(gref_list);
-static DEFINE_SPINLOCK(gref_lock);
+static DEFINE_MUTEX(gref_mutex);
 static int gref_size;
 
 struct notify_info {
@@ -143,15 +143,15 @@ static int add_grefs(struct ioctl_gntalloc_alloc_gref *op,
         }
 
         /* Add to gref lists. */
-        spin_lock(&gref_lock);
+        mutex_lock(&gref_mutex);
         list_splice_tail(&queue_gref, &gref_list);
         list_splice_tail(&queue_file, &priv->list);
-        spin_unlock(&gref_lock);
+        mutex_unlock(&gref_mutex);
 
         return 0;
 
 undo:
-        spin_lock(&gref_lock);
+        mutex_lock(&gref_mutex);
         gref_size -= (op->count - i);
 
         list_for_each_entry(gref, &queue_file, next_file) {
@@ -167,7 +167,7 @@ undo:
          */
         if (unlikely(!list_empty(&queue_gref)))
                 list_splice_tail(&queue_gref, &gref_list);
-        spin_unlock(&gref_lock);
+        mutex_unlock(&gref_mutex);
         return rc;
 }
 
@@ -251,7 +251,7 @@ static int gntalloc_release(struct inode *inode, struct file *filp)
 
         pr_debug("%s: priv %p\n", __func__, priv);
 
-        spin_lock(&gref_lock);
+        mutex_lock(&gref_mutex);
         while (!list_empty(&priv->list)) {
                 gref = list_entry(priv->list.next,
                         struct gntalloc_gref, next_file);
@@ -261,7 +261,7 @@ static int gntalloc_release(struct inode *inode, struct file *filp)
                         __del_gref(gref);
         }
         kfree(priv);
-        spin_unlock(&gref_lock);
+        mutex_unlock(&gref_mutex);
 
         return 0;
 }
@@ -286,21 +286,21 @@ static long gntalloc_ioctl_alloc(struct gntalloc_file_private_data *priv,
                 goto out;
         }
 
-        spin_lock(&gref_lock);
+        mutex_lock(&gref_mutex);
         /* Clean up pages that were at zero (local) users but were still mapped
          * by remote domains. Since those pages count towards the limit that we
          * are about to enforce, removing them here is a good idea.
          */
         do_cleanup();
         if (gref_size + op.count > limit) {
-                spin_unlock(&gref_lock);
+                mutex_unlock(&gref_mutex);
                 rc = -ENOSPC;
                 goto out_free;
         }
         gref_size += op.count;
         op.index = priv->index;
         priv->index += op.count * PAGE_SIZE;
-        spin_unlock(&gref_lock);
+        mutex_unlock(&gref_mutex);
 
         rc = add_grefs(&op, gref_ids, priv);
         if (rc < 0)
@@ -343,7 +343,7 @@ static long gntalloc_ioctl_dealloc(struct gntalloc_file_private_data *priv,
                 goto dealloc_grant_out;
         }
 
-        spin_lock(&gref_lock);
+        mutex_lock(&gref_mutex);
         gref = find_grefs(priv, op.index, op.count);
         if (gref) {
                 /* Remove from the file list only, and decrease reference count.
@@ -363,7 +363,7 @@ static long gntalloc_ioctl_dealloc(struct gntalloc_file_private_data *priv,
 
         do_cleanup();
 
-        spin_unlock(&gref_lock);
+        mutex_unlock(&gref_mutex);
 dealloc_grant_out:
         return rc;
 }
@@ -383,7 +383,7 @@ static long gntalloc_ioctl_unmap_notify(struct gntalloc_file_private_data *priv,
         index = op.index & ~(PAGE_SIZE - 1);
         pgoff = op.index & (PAGE_SIZE - 1);
 
-        spin_lock(&gref_lock);
+        mutex_lock(&gref_mutex);
 
         gref = find_grefs(priv, index, 1);
         if (!gref) {
@@ -400,8 +400,9 @@ static long gntalloc_ioctl_unmap_notify(struct gntalloc_file_private_data *priv,
         gref->notify.pgoff = pgoff;
         gref->notify.event = op.event_channel_port;
         rc = 0;
+
  unlock_out:
-        spin_unlock(&gref_lock);
+        mutex_unlock(&gref_mutex);
         return rc;
 }
 
@@ -433,9 +434,9 @@ static void gntalloc_vma_open(struct vm_area_struct *vma)
         if (!gref)
                 return;
 
-        spin_lock(&gref_lock);
+        mutex_lock(&gref_mutex);
         gref->users++;
-        spin_unlock(&gref_lock);
+        mutex_unlock(&gref_mutex);
 }
 
 static void gntalloc_vma_close(struct vm_area_struct *vma)
@@ -444,11 +445,11 @@ static void gntalloc_vma_close(struct vm_area_struct *vma)
         if (!gref)
                 return;
 
-        spin_lock(&gref_lock);
+        mutex_lock(&gref_mutex);
         gref->users--;
         if (gref->users == 0)
                 __del_gref(gref);
-        spin_unlock(&gref_lock);
+        mutex_unlock(&gref_mutex);
 }
 
 static struct vm_operations_struct gntalloc_vmops = {
@@ -471,7 +472,7 @@ static int gntalloc_mmap(struct file *filp, struct vm_area_struct *vma)
                 return -EINVAL;
         }
 
-        spin_lock(&gref_lock);
+        mutex_lock(&gref_mutex);
         gref = find_grefs(priv, vma->vm_pgoff << PAGE_SHIFT, count);
         if (gref == NULL) {
                 rv = -ENOENT;
@@ -499,7 +500,7 @@ static int gntalloc_mmap(struct file *filp, struct vm_area_struct *vma)
         rv = 0;
 
 out_unlock:
-        spin_unlock(&gref_lock);
+        mutex_unlock(&gref_mutex);
         return rv;
 }