[063/141] xen-netback: avoid allocating variable size array on stack

Steven Rostedt
2013-07-03T18:44:34Z

[-- Attachment #1: 0063-xen-netback-avoid-allocating-variable-size-array-on-.patch --]
[-- Type: text/plain, Size: 2234 bytes --]

3.6.11.6 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Wei Liu <wei.liu2@citrix.com>

[ Upstream commit 59ccb4ebbc35e36a3c143f2d1355deb75c2e628f ]

Tune xen_netbk_count_requests to not touch working array beyond limit, so that
we can make working array size constant.

Suggested-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
drivers/net/xen-netback/netback.c | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index b78839e..4925188 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -905,11 +905,14 @@ static int netbk_count_requests(struct xenvif *vif,
RING_IDX cons = vif->tx.req_cons;
int slots = 0;
int drop_err = 0;
+ int more_data;

if (!(first->flags & XEN_NETTXF_more_data))
return 0;

do {
+ struct xen_netif_tx_request dropped_tx = { 0 };
+
if (slots >= work_to_do) {
netdev_err(vif->dev,
"Asked for %d slots but exceeds this limit\n",
@@ -943,6 +946,9 @@ static int netbk_count_requests(struct xenvif *vif,
drop_err = -E2BIG;
}

+ if (drop_err)
+ txp = &dropped_tx;
+
memcpy(txp, RING_GET_REQUEST(&vif->tx, cons + slots),
sizeof(*txp));

@@ -972,7 +978,13 @@ static int netbk_count_requests(struct xenvif *vif,
netbk_fatal_tx_err(vif);
return -EINVAL;
}
- } while ((txp++)->flags & XEN_NETTXF_more_data);
+
+ more_data = txp->flags & XEN_NETTXF_more_data;
+
+ if (!drop_err)
+ txp++;
+
+ } while (more_data);

if (drop_err) {
netbk_tx_err(vif, first, cons + slots);
@@ -1384,7 +1396,7 @@ static unsigned xen_netbk_tx_build_gops(struct xen_netbk *netbk)
!list_empty(&netbk->net_schedule_list)) {
struct xenvif *vif;
struct xen_netif_tx_request txreq;
- struct xen_netif_tx_request txfrags[max_skb_slots];
+ struct xen_netif_tx_request txfrags[XEN_NETIF_NR_SLOTS_MIN];
struct page *page;
struct xen_netif_extra_info extras[XEN_NETIF_EXTRA_TYPE_MAX-1];
u16 pending_idx;
--
1.7.10.4