[PATCH net-next v2 12/12] page_pool: make sure struct device is stable

[Jesper Dangaard Brouer]

For DMA mapping use-case the page_pool keeps a pointer
to the struct device, which is used in DMA map/unmap calls.

For our in-flight handling, we also need to make sure that
the struct device have not disappeared.  This is assured
via using get_device/put_device API.

Signed-off-by: Jesper Dangaard Brouer <bro...@redhat.com>
Reported-by: Ivan Khoronzhuk <ivan.khoronz...@linaro.org>
---
 net/core/page_pool.c |    8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index f55ab055d543..b366f59885c1 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -8,6 +8,7 @@
 #include <linux/types.h>
 #include <linux/kernel.h>
 #include <linux/slab.h>
+#include <linux/device.h>
 
 #include <net/page_pool.h>
 #include <linux/dma-direction.h>
@@ -48,6 +49,9 @@ static int page_pool_init(struct page_pool *pool,
 
        atomic_set(&pool->pages_state_release_cnt, 0);
 
+       if (pool->p.flags & PP_FLAG_DMA_MAP)
+               get_device(pool->p.dev);
+
        return 0;
 }
 
@@ -360,6 +364,10 @@ void __page_pool_free(struct page_pool *pool)
                __warn_in_flight(pool);
 
        ptr_ring_cleanup(&pool->ring, NULL);
+
+       if (pool->p.flags & PP_FLAG_DMA_MAP)
+               put_device(pool->p.dev);
+
        kfree(pool);
 }
 EXPORT_SYMBOL(__page_pool_free);