[bpf-next V3 PATCH 12/15] xdp: allow page_pool as an allocator type in xdp_return_frame

Jesper Dangaard Brouer
2018-03-09T20:56:06Z

New allocator type MEM_TYPE_PAGE_POOL for page_pool usage.

The registered allocator page_pool pointer is not available directly
from xdp_rxq_info, but it could be (if needed). For now, the driver
should keep separate track of the page_pool pointer, which it should
use for RX-ring page allocation.

As suggested by Saeed, to maintain a symmetric API it is the drivers
responsibility to allocate/create and free/destroy the page_pool.
Thus, after the driver have called xdp_rxq_info_unreg(), it is drivers
responsibility to free the page_pool, but with a RCU free call. This
is done easily via the page_pool helper page_pool_destroy_rcu() (which
avoids touching any driver code during the RCU callback, which could
happen after the driver have been unloaded).

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
include/net/xdp.h | 3 +++
net/core/xdp.c | 23 ++++++++++++++++++++---
2 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/include/net/xdp.h b/include/net/xdp.h
index 859aa9b737fe..98b55eaf8fd7 100644
--- a/include/net/xdp.h
+++ b/include/net/xdp.h
@@ -36,6 +36,7 @@
enum mem_type {
MEM_TYPE_PAGE_SHARED = 0, /* Split-page refcnt based model */
MEM_TYPE_PAGE_ORDER0, /* Orig XDP full page model */
+ MEM_TYPE_PAGE_POOL,
MEM_TYPE_MAX,
};

@@ -44,6 +45,8 @@ struct xdp_mem_info {
u32 id;
};

+struct page_pool;
+
struct xdp_rxq_info {
struct net_device *dev;
u32 queue_index;
diff --git a/net/core/xdp.c b/net/core/xdp.c
index 06a5b39491ad..fe8e87abc266 100644
--- a/net/core/xdp.c
+++ b/net/core/xdp.c
@@ -8,6 +8,7 @@
#include <linux/slab.h>
#include <linux/idr.h>
#include <linux/rhashtable.h>
+#include <net/page_pool.h>

#include <net/xdp.h>

@@ -27,7 +28,10 @@ static struct rhashtable *mem_id_ht;

struct xdp_mem_allocator {
struct xdp_mem_info mem;
- void *allocator;
+ union {
+ void *allocator;
+ struct page_pool *page_pool;
+ };
struct rhash_head node;
struct rcu_head rcu;
};
@@ -74,7 +78,9 @@ void __xdp_mem_allocator_rcu_free(struct rcu_head *rcu)
/* Allow this ID to be reused */
ida_simple_remove(&mem_id_pool, xa->mem.id);

- /* TODO: Depending on allocator type/pointer free resources */
+ /* Notice, driver is expected to free the *allocator,
+ * e.g. page_pool, and MUST also use RCU free.
+ */

/* Poison memory */
xa->mem.id = 0xFFFF;
@@ -290,11 +296,21 @@ EXPORT_SYMBOL_GPL(xdp_rxq_info_reg_mem_model);

void xdp_return_frame(void *data, struct xdp_mem_info *mem)
{
- struct xdp_mem_allocator *xa;
+ struct xdp_mem_allocator *xa = NULL;

rcu_read_lock();
if (mem->id)
xa = rhashtable_lookup(mem_id_ht, &mem->id, mem_id_rht_params);
+
+ if (mem->type == MEM_TYPE_PAGE_POOL) {
+ struct page *page = virt_to_head_page(data);
+
+ if (xa)
+ page_pool_put_page(xa->page_pool, page);
+ else
+ put_page(page);
+ return;
+ }
rcu_read_unlock();

if (mem->type == MEM_TYPE_PAGE_SHARED) {
@@ -306,6 +322,7 @@ void xdp_return_frame(void *data, struct xdp_mem_info *mem)
struct page *page = virt_to_page(data); /* Assumes order0 page*/

put_page(page);
+ return;
}
}
EXPORT_SYMBOL_GPL(xdp_return_frame);