page_pool: export page_pool_disable_direct_recycling()

56ef27e3 unexported page_pool_unlink_napi() and renamed it to
page_pool_disable_direct_recycling(). This is because there was no
in-tree user of page_pool_unlink_napi().

Since then Rx queue API and an implementation in bnxt got merged. In the
bnxt implementation, it broadly follows the following steps: allocate
new queue memory + page pool, stop old rx queue, swap, then destroy old
queue memory + page pool.

The existing NAPI instance is re-used so when the old page pool that is
no longer used but still linked to this shared NAPI instance is
destroyed, it will trigger warnings.

In my initial patches I unlinked a page pool from a NAPI instance
directly. Instead, export page_pool_disable_direct_recycling() and call
that instead to avoid having a driver touch a core struct.
Suggested-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David Wei <dw@davidwei.uk>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

include/net/page_pool/types.h

@@ -229,6 +229,7 @@ struct page_pool *page_pool_create_percpu(const struct page_pool_params *params,
 struct xdp_mem_info;
 
 #ifdef CONFIG_PAGE_POOL
+void page_pool_disable_direct_recycling(struct page_pool *pool);
 void page_pool_destroy(struct page_pool *pool);
 void page_pool_use_xdp_mem(struct page_pool *pool, void (*disconnect)(void *),
 			   const struct xdp_mem_info *mem);

net/core/page_pool.c

@@ -1014,7 +1014,7 @@ void page_pool_use_xdp_mem(struct page_pool *pool, void (*disconnect)(void *),
 	pool->xdp_mem_id = mem->id;
 }
 
-static void page_pool_disable_direct_recycling(struct page_pool *pool)
+void page_pool_disable_direct_recycling(struct page_pool *pool)
 {
 	/* Disable direct recycling based on pool->cpuid.
 	 * Paired with READ_ONCE() in page_pool_napi_local().
@@ -1032,6 +1032,7 @@ static void page_pool_disable_direct_recycling(struct page_pool *pool)
 
 	WRITE_ONCE(pool->p.napi, NULL);
 }
+EXPORT_SYMBOL(page_pool_disable_direct_recycling);
 
 void page_pool_destroy(struct page_pool *pool)
 {