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Subject[PATCH v6 net-next 1/5] xdp: allow same allocator usage
Date
First of all, it is an absolute requirement that each RX-queue have
their own page_pool object/allocator. And this change is intendant
to handle special case, where a single RX-queue can receive packets
from two different net_devices.

In order to protect against using same allocator for 2 different rx
queues, add queue_index to xdp_mem_allocator to catch the obvious
mistake where queue_index mismatch, as proposed by Jesper Dangaard
Brouer.

Adding this on xdp allocator level allows drivers with such dependency
change the allocators w/o modifications.

Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
---
include/net/xdp_priv.h | 2 ++
net/core/xdp.c | 55 ++++++++++++++++++++++++++++++++++++++++++
2 files changed, 57 insertions(+)

diff --git a/include/net/xdp_priv.h b/include/net/xdp_priv.h
index 6a8cba6ea79a..9858a4057842 100644
--- a/include/net/xdp_priv.h
+++ b/include/net/xdp_priv.h
@@ -18,6 +18,8 @@ struct xdp_mem_allocator {
struct rcu_head rcu;
struct delayed_work defer_wq;
unsigned long defer_warn;
+ unsigned long refcnt;
+ u32 queue_index;
};

#endif /* __LINUX_NET_XDP_PRIV_H__ */
diff --git a/net/core/xdp.c b/net/core/xdp.c
index 829377cc83db..4f0ddbb3717a 100644
--- a/net/core/xdp.c
+++ b/net/core/xdp.c
@@ -98,6 +98,18 @@ static bool __mem_id_disconnect(int id, bool force)
WARN(1, "Request remove non-existing id(%d), driver bug?", id);
return true;
}
+
+ /* to avoid calling hash lookup twice, decrement refcnt here till it
+ * reaches zero, then it can be called from workqueue afterwards.
+ */
+ if (xa->refcnt)
+ xa->refcnt--;
+
+ if (xa->refcnt) {
+ mutex_unlock(&mem_id_lock);
+ return true;
+ }
+
xa->disconnect_cnt++;

/* Detects in-flight packet-pages for page_pool */
@@ -312,6 +324,33 @@ static bool __is_supported_mem_type(enum xdp_mem_type type)
return true;
}

+static struct xdp_mem_allocator *xdp_allocator_find(void *allocator)
+{
+ struct xdp_mem_allocator *xae, *xa = NULL;
+ struct rhashtable_iter iter;
+
+ if (!allocator)
+ return xa;
+
+ rhashtable_walk_enter(mem_id_ht, &iter);
+ do {
+ rhashtable_walk_start(&iter);
+
+ while ((xae = rhashtable_walk_next(&iter)) && !IS_ERR(xae)) {
+ if (xae->allocator == allocator) {
+ xa = xae;
+ break;
+ }
+ }
+
+ rhashtable_walk_stop(&iter);
+
+ } while (xae == ERR_PTR(-EAGAIN));
+ rhashtable_walk_exit(&iter);
+
+ return xa;
+}
+
int xdp_rxq_info_reg_mem_model(struct xdp_rxq_info *xdp_rxq,
enum xdp_mem_type type, void *allocator)
{
@@ -347,6 +386,20 @@ int xdp_rxq_info_reg_mem_model(struct xdp_rxq_info *xdp_rxq,
}
}

+ mutex_lock(&mem_id_lock);
+ xdp_alloc = xdp_allocator_find(allocator);
+ if (xdp_alloc) {
+ /* One allocator per queue is supposed only */
+ if (xdp_alloc->queue_index != xdp_rxq->queue_index)
+ return -EINVAL;
+
+ xdp_rxq->mem.id = xdp_alloc->mem.id;
+ xdp_alloc->refcnt++;
+ mutex_unlock(&mem_id_lock);
+ return 0;
+ }
+ mutex_unlock(&mem_id_lock);
+
xdp_alloc = kzalloc(sizeof(*xdp_alloc), gfp);
if (!xdp_alloc)
return -ENOMEM;
@@ -360,6 +413,8 @@ int xdp_rxq_info_reg_mem_model(struct xdp_rxq_info *xdp_rxq,
xdp_rxq->mem.id = id;
xdp_alloc->mem = xdp_rxq->mem;
xdp_alloc->allocator = allocator;
+ xdp_alloc->refcnt = 1;
+ xdp_alloc->queue_index = xdp_rxq->queue_index;

/* Insert allocator into ID lookup table */
ptr = rhashtable_insert_slow(mem_id_ht, &id, &xdp_alloc->node);
--
2.17.1
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