net: page_pool: add page_pool_get()

There is a page_pool_put() function but no get equivalent.
Having multiple references to a page pool is quite useful.
It avoids branching in create / destroy paths in drivers
which support memory providers.

Use the new helper in bnxt.

Acked-by: Jesper Dangaard Brouer <[e-mail]>
Reviewed-by: Dragos Tatulea <[e-mail]>
Reviewed-by: Mina Almasry <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

drivers/net/ethernet/broadcom/bnxt/bnxt.c

···
 			xdp_rxq_info_unreg(&rxr->xdp_rxq);
 
 		page_pool_destroy(rxr->page_pool);
-		if (bnxt_separate_head_pool(rxr))
-			page_pool_destroy(rxr->head_pool);
+		page_pool_destroy(rxr->head_pool);
 		rxr->page_pool = rxr->head_pool = NULL;
 
 		kfree(rxr->rx_agg_bmap);
···
 		pool = page_pool_create(&pp);
 		if (IS_ERR(pool))
 			goto err_destroy_pp;
+	} else {
+		page_pool_get(pool);
 	}
 	rxr->head_pool = pool;
 
···
 	xdp_rxq_info_unreg(&clone->xdp_rxq);
 err_page_pool_destroy:
 	page_pool_destroy(clone->page_pool);
-	if (bnxt_separate_head_pool(clone))
-		page_pool_destroy(clone->head_pool);
+	page_pool_destroy(clone->head_pool);
 	clone->page_pool = NULL;
 	clone->head_pool = NULL;
 	return rc;
···
 	xdp_rxq_info_unreg(&rxr->xdp_rxq);
 
 	page_pool_destroy(rxr->page_pool);
-	if (bnxt_separate_head_pool(rxr))
-		page_pool_destroy(rxr->head_pool);
+	page_pool_destroy(rxr->head_pool);
 	rxr->page_pool = NULL;
 	rxr->head_pool = NULL;
 

include/net/page_pool/helpers.h

···
 				     offset, dma_sync_size);
 }
 
+static inline void page_pool_get(struct page_pool *pool)
+{
+	refcount_inc(&pool->user_cnt);
+}
+
 static inline bool page_pool_put(struct page_pool *pool)
 {
 	return refcount_dec_and_test(&pool->user_cnt);