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-rw-r--r--drivers/xen/evtchn.c20
1 files changed, 8 insertions, 12 deletions
diff --git a/drivers/xen/evtchn.c b/drivers/xen/evtchn.c
index 38272ad24551..f4edd6df3df2 100644
--- a/drivers/xen/evtchn.c
+++ b/drivers/xen/evtchn.c
@@ -316,7 +316,6 @@ static int evtchn_resize_ring(struct per_user_data *u)
{
unsigned int new_size;
evtchn_port_t *new_ring, *old_ring;
- unsigned int p, c;
/*
* Ensure the ring is large enough to capture all possible
@@ -346,20 +345,17 @@ static int evtchn_resize_ring(struct per_user_data *u)
/*
* Copy the old ring contents to the new ring.
*
- * If the ring contents crosses the end of the current ring,
- * it needs to be copied in two chunks.
+ * To take care of wrapping, a full ring, and the new index
+ * pointing into the second half, simply copy the old contents
+ * twice.
*
* +---------+ +------------------+
- * |34567 12| -> | 1234567 |
- * +-----p-c-+ +------------------+
+ * |34567 12| -> |34567 1234567 12|
+ * +-----p-c-+ +-------c------p---+
*/
- p = evtchn_ring_offset(u, u->ring_prod);
- c = evtchn_ring_offset(u, u->ring_cons);
- if (p < c) {
- memcpy(new_ring + c, u->ring + c, (u->ring_size - c) * sizeof(*u->ring));
- memcpy(new_ring + u->ring_size, u->ring, p * sizeof(*u->ring));
- } else
- memcpy(new_ring + c, u->ring + c, (p - c) * sizeof(*u->ring));
+ memcpy(new_ring, old_ring, u->ring_size * sizeof(*u->ring));
+ memcpy(new_ring + u->ring_size, old_ring,
+ u->ring_size * sizeof(*u->ring));
u->ring = new_ring;
u->ring_size = new_size;