xdp: rhashtable with allocator ID to pointer mapping

Use the IDA infrastructure for getting a cyclic increasing ID number,
that is used for keeping track of each registered allocator per
RX-queue xdp_rxq_info.  Instead of using the IDR infrastructure, which
uses a radix tree, use a dynamic rhashtable, for creating ID to
pointer lookup table, because this is faster.

The problem that is being solved here is that, the xdp_rxq_info
pointer (stored in xdp_buff) cannot be used directly, as the
guaranteed lifetime is too short.  The info is needed on a
(potentially) remote CPU during DMA-TX completion time . In an
xdp_frame the xdp_mem_info is stored, when it got converted from an
xdp_buff, which is sufficient for the simple page refcnt based recycle
schemes.

For more advanced allocators there is a need to store a pointer to the
registered allocator.  Thus, there is a need to guard the lifetime or
validity of the allocator pointer, which is done through this
rhashtable ID map to pointer. The removal and validity of of the
allocator and helper struct xdp_mem_allocator is guarded by RCU.  The
allocator will be created by the driver, and registered with
xdp_rxq_info_reg_mem_model().

It is up-to debate who is responsible for freeing the allocator
pointer or invoking the allocator destructor function.  In any case,
this must happen via RCU freeing.

Use the IDA infrastructure for getting a cyclic increasing ID number,
that is used for keeping track of each registered allocator per
RX-queue xdp_rxq_info.

V4: Per req of Jason Wang
- Use xdp_rxq_info_reg_mem_model() in all drivers implementing
  XDP_REDIRECT, even-though it's not strictly necessary when
  allocator==NULL for type MEM_TYPE_PAGE_SHARED (given it's zero).

V6: Per req of Alex Duyck
- Introduce rhashtable_lookup() call in later patch

V8: Address sparse should be static warnings (from kbuild test robot)

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 12 deletions

diff --git a/include/net/xdp.h b/include/net/xdp.h
index ea3773f94f65..5f67c62540aa 100644
--- a/include/net/xdp.h
+++ b/include/net/xdp.h
@@ -41,6 +41,7 @@ enum xdp_mem_type {
 
 struct xdp_mem_info {
 	u32 type; /* enum xdp_mem_type, but known size type */
+	u32 id;
 };
 
 struct xdp_rxq_info {
@@ -99,18 +100,7 @@ struct xdp_frame *convert_to_xdp_frame(struct xdp_buff *xdp)
 	return xdp_frame;
 }
 
-static inline
-void xdp_return_frame(void *data, struct xdp_mem_info *mem)
-{
-	if (mem->type == MEM_TYPE_PAGE_SHARED)
-		page_frag_free(data);
-
-	if (mem->type == MEM_TYPE_PAGE_ORDER0) {
-		struct page *page = virt_to_page(data); /* Assumes order0 page*/
-
-		put_page(page);
-	}
-}
+void xdp_return_frame(void *data, struct xdp_mem_info *mem);
 
 int xdp_rxq_info_reg(struct xdp_rxq_info *xdp_rxq,
 		     struct net_device *dev, u32 queue_index);