[PATCH RFC v2 6/9] xdp: Add a flag for disabling napi_direct of xdp_return_frame in xdp_mem_info

[Toshiaki Makita]

From: Toshiaki Makita <makita.toshi...@lab.ntt.co.jp>

We need some mechanism to disable napi_direct on calling
xdp_return_frame_rx_napi() from some context.
When veth gets support of XDP_REDIRECT, it will redirects packets which
are redirected from other devices. On redirection veth will reuse
xdp_mem_info of the redirection source device to make return_frame work.
But in this case .ndo_xdp_xmit() called from veth redirection uses
xdp_mem_info which is not guarded by NAPI, because the .ndo_xdp_xmit is
not called directly from the rxq which owns the xdp_mem_info.

This approach introduces a flag in xdp_mem_info to indicate that
napi_direct should be disabled even when _rx_napi variant is used.

Signed-off-by: Toshiaki Makita <makita.toshi...@lab.ntt.co.jp>
---
 include/net/xdp.h | 4 ++++
 net/core/xdp.c    | 6 ++++--
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/include/net/xdp.h b/include/net/xdp.h
index 2deea7166a34..ea0c80f6c8ee 100644
--- a/include/net/xdp.h
+++ b/include/net/xdp.h
@@ -41,6 +41,9 @@ enum xdp_mem_type {
        MEM_TYPE_MAX,
 };
 
+/* XDP flags for xdp_mem_info */
+#define XDP_MEM_RF_NO_DIRECT   BIT(0)  /* don't use napi_direct */
+
 /* XDP flags for ndo_xdp_xmit */
 #define XDP_XMIT_FLUSH         (1U << 0)       /* doorbell signal consumer */
 #define XDP_XMIT_FLAGS_MASK    XDP_XMIT_FLUSH
@@ -48,6 +51,7 @@ enum xdp_mem_type {
 struct xdp_mem_info {
        u32 type; /* enum xdp_mem_type, but known size type */
        u32 id;
+       u32 flags;
 };
 
 struct page_pool;
diff --git a/net/core/xdp.c b/net/core/xdp.c
index 9d1f22072d5d..e94f146360b2 100644
--- a/net/core/xdp.c
+++ b/net/core/xdp.c
@@ -327,10 +327,12 @@ static void __xdp_return(void *data, struct xdp_mem_info 
*mem, bool napi_direct,
                /* 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)
+               if (xa) {
+                       napi_direct &= !(mem->flags & XDP_MEM_RF_NO_DIRECT);
                        page_pool_put_page(xa->page_pool, page, napi_direct);
-               else
+               } else {
                        put_page(page);
+               }
                rcu_read_unlock();
                break;
        case MEM_TYPE_PAGE_SHARED:
-- 
2.14.3