netpoll: Drop budget parameter from NAPI polling call hierarchy
For some reason we were carrying the budget value around between the
various calls to napi->poll. If for example one of the drivers called had
a bug in which it returned a non-zero value for work this could result in
the budget value becoming negative.
Rather than carry around a value of budget that is 0 or less we can instead
just loop through and pass 0 to each napi->poll call. If any driver
returns a value for work done that is non-zero then we can report that
driver and continue rather than allowing a bad actor to make the budget
value negative and pass that negative value to napi->poll.
Note, the only actual change here is that instead of letting budget become
negative we are keeping it at 0 regardless of the value returned for work
since it should not be possible for the polling routine to do any actual
work with a budget of 0. So if the polling routine returns a non-0 value
we are just reporting it and continuing with a budget of 0 rather than
letting that work value be subtracted from the budget of 0.
Signed-off-by: Alexander Duyck <aduyck@mirantis.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index 8bdada2..94acfc8 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -140,7 +140,7 @@
* case. Further, we test the poll_owner to avoid recursion on UP
* systems where the lock doesn't exist.
*/
-static int poll_one_napi(struct napi_struct *napi, int budget)
+static void poll_one_napi(struct napi_struct *napi)
{
int work = 0;
@@ -149,33 +149,33 @@
* holding the napi->poll_lock.
*/
if (!test_bit(NAPI_STATE_SCHED, &napi->state))
- return budget;
+ return;
/* If we set this bit but see that it has already been set,
* that indicates that napi has been disabled and we need
* to abort this operation
*/
if (test_and_set_bit(NAPI_STATE_NPSVC, &napi->state))
- goto out;
+ return;
- work = napi->poll(napi, budget);
- WARN_ONCE(work > budget, "%pF exceeded budget in poll\n", napi->poll);
+ /* We explicilty pass the polling call a budget of 0 to
+ * indicate that we are clearing the Tx path only.
+ */
+ work = napi->poll(napi, 0);
+ WARN_ONCE(work, "%pF exceeded budget in poll\n", napi->poll);
trace_napi_poll(napi);
clear_bit(NAPI_STATE_NPSVC, &napi->state);
-
-out:
- return budget - work;
}
-static void poll_napi(struct net_device *dev, int budget)
+static void poll_napi(struct net_device *dev)
{
struct napi_struct *napi;
list_for_each_entry(napi, &dev->napi_list, dev_list) {
if (napi->poll_owner != smp_processor_id() &&
spin_trylock(&napi->poll_lock)) {
- budget = poll_one_napi(napi, budget);
+ poll_one_napi(napi);
spin_unlock(&napi->poll_lock);
}
}
@@ -185,7 +185,6 @@
{
const struct net_device_ops *ops;
struct netpoll_info *ni = rcu_dereference_bh(dev->npinfo);
- int budget = 0;
/* Don't do any rx activity if the dev_lock mutex is held
* the dev_open/close paths use this to block netpoll activity
@@ -208,7 +207,7 @@
/* Process pending work on NIC */
ops->ndo_poll_controller(dev);
- poll_napi(dev, budget);
+ poll_napi(dev);
up(&ni->dev_lock);