[net-next V8 PATCH 13/16] xdp: allow page_pool as an allocator type in xdp_return_frame

Jesper Dangaard Brouer
2018-03-31T12:06:54Z

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() (which
avoids touching any driver code during the RCU callback, which could
happen after the driver have been unloaded).

V8: address issues found by kbuild test robot
- Address sparse should be static warnings
- Allow xdp.o to be compiled without page_pool.o

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
include/net/page_pool.h | 14 +++++++++++
include/net/xdp.h | 3 ++
net/core/xdp.c | 60 ++++++++++++++++++++++++++++++++++++++---------
3 files changed, 65 insertions(+), 12 deletions(-)

diff --git a/include/net/page_pool.h b/include/net/page_pool.h
index 1fe77db59518..c79087153148 100644
--- a/include/net/page_pool.h
+++ b/include/net/page_pool.h
@@ -117,7 +117,12 @@ void __page_pool_put_page(struct page_pool *pool,

static inline void page_pool_put_page(struct page_pool *pool, struct page *page)
{
+ /* When page_pool isn't compiled-in, net/core/xdp.c doesn't
+ * allow registering MEM_TYPE_PAGE_POOL, but shield linker.
+ */
+#ifdef CONFIG_PAGE_POOL
__page_pool_put_page(pool, page, false);
+#endif
}
/* Very limited use-cases allow recycle direct */
static inline void page_pool_recycle_direct(struct page_pool *pool,
@@ -126,4 +131,13 @@ static inline void page_pool_recycle_direct(struct page_pool *pool,
__page_pool_put_page(pool, page, true);
}

+static inline bool is_page_pool_compiled_in(void)
+{
+#ifdef CONFIG_PAGE_POOL
+ return true;
+#else
+ return false;
+#endif
+}
+
#endif /* _NET_PAGE_POOL_H */
diff --git a/include/net/xdp.h b/include/net/xdp.h
index 5f67c62540aa..d0ee437753dc 100644
--- a/include/net/xdp.h
+++ b/include/net/xdp.h
@@ -36,6 +36,7 @@
enum xdp_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 8b2cb79b5de0..d8115903e454 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 @@ static 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;
@@ -225,6 +231,17 @@ static int __mem_id_cyclic_get(gfp_t gfp)
return id;
}

+static inline bool __is_supported_mem_type(enum xdp_mem_type type)
+{
+ if (type == MEM_TYPE_PAGE_POOL)
+ return is_page_pool_compiled_in();
+
+ if (type >= MEM_TYPE_MAX)
+ return false;
+
+ return true;
+}
+
int xdp_rxq_info_reg_mem_model(struct xdp_rxq_info *xdp_rxq,
enum xdp_mem_type type, void *allocator)
{
@@ -238,13 +255,16 @@ int xdp_rxq_info_reg_mem_model(struct xdp_rxq_info *xdp_rxq,
return -EFAULT;
}

- if (type >= MEM_TYPE_MAX)
- return -EINVAL;
+ if (!__is_supported_mem_type(type))
+ return -EOPNOTSUPP;

xdp_rxq->mem.type = type;

- if (!allocator)
+ if (!allocator) {
+ if (type == MEM_TYPE_PAGE_POOL)
+ return -EINVAL; /* Setup time check page_pool req */
return 0;
+ }

/* Delay init of rhashtable to save memory if feature isn't used */
if (!mem_id_init) {
@@ -290,15 +310,31 @@ EXPORT_SYMBOL_GPL(xdp_rxq_info_reg_mem_model);

void xdp_return_frame(void *data, struct xdp_mem_info *mem)
{
- if (mem->type == MEM_TYPE_PAGE_SHARED) {
+ struct xdp_mem_allocator *xa;
+ struct page *page;
+
+ switch (mem->type) {
+ case MEM_TYPE_PAGE_POOL:
+ rcu_read_lock();
+ /* mem->id is valid, checked in xdp_rxq_info_reg_mem_model() */
+ xa = rhashtable_lookup(mem_id_ht, &mem->id, mem_id_rht_params);
+ page = virt_to_head_page(data);
+ if (xa)
+ page_pool_put_page(xa->page_pool, page);
+ else
+ put_page(page);
+ rcu_read_unlock();
+ break;
+ case MEM_TYPE_PAGE_SHARED:
page_frag_free(data);
- return;
- }
-
- if (mem->type == MEM_TYPE_PAGE_ORDER0) {
- struct page *page = virt_to_page(data); /* Assumes order0 page*/
-
+ break;
+ case MEM_TYPE_PAGE_ORDER0:
+ page = virt_to_page(data); /* Assumes order0 page*/
put_page(page);
+ break;
+ default:
+ /* Not possible, checked in xdp_rxq_info_reg_mem_model() */
+ break;
}
}
EXPORT_SYMBOL_GPL(xdp_return_frame);