page_pool: Add function to batch and return stats

Adds a function page_pool_get_stats which can be used by drivers to obtain
stats for a specified page_pool.
Signed-off-by: Joe Damato <jdamato@fastly.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/page_pool.h

@@ -107,6 +107,23 @@ struct page_pool_recycle_stats {
 			      * refcnt
 			      */
 };
+
+/* This struct wraps the above stats structs so users of the
+ * page_pool_get_stats API can pass a single argument when requesting the
+ * stats for the page pool.
+ */
+struct page_pool_stats {
+	struct page_pool_alloc_stats alloc_stats;
+	struct page_pool_recycle_stats recycle_stats;
+};
+
+/*
+ * Drivers that wish to harvest page pool stats and report them to users
+ * (perhaps via ethtool, debugfs, or another mechanism) can allocate a
+ * struct page_pool_stats call page_pool_get_stats to get stats for the specified pool.
+ */
+bool page_pool_get_stats(struct page_pool *pool,
+			 struct page_pool_stats *stats);
 #endif
 
 struct page_pool {

net/core/page_pool.c

@@ -35,6 +35,31 @@
 		struct page_pool_recycle_stats __percpu *s = pool->recycle_stats;	\
 		this_cpu_inc(s->__stat);						\
 	} while (0)
+
+bool page_pool_get_stats(struct page_pool *pool,
+			 struct page_pool_stats *stats)
+{
+	int cpu = 0;
+
+	if (!stats)
+		return false;
+
+	memcpy(&stats->alloc_stats, &pool->alloc_stats, sizeof(pool->alloc_stats));
+
+	for_each_possible_cpu(cpu) {
+		const struct page_pool_recycle_stats *pcpu =
+			per_cpu_ptr(pool->recycle_stats, cpu);
+
+		stats->recycle_stats.cached += pcpu->cached;
+		stats->recycle_stats.cache_full += pcpu->cache_full;
+		stats->recycle_stats.ring += pcpu->ring;
+		stats->recycle_stats.ring_full += pcpu->ring_full;
+		stats->recycle_stats.released_refcnt += pcpu->released_refcnt;
+	}
+
+	return true;
+}
+EXPORT_SYMBOL(page_pool_get_stats);
 #else
 #define alloc_stat_inc(pool, __stat)
 #define recycle_stat_inc(pool, __stat)