[RFC PATCH 19/21] core: add page recycling logic for netgpu pages

[Jonathan Lemon]

netgpu pages will always have a refcount of at least one (held by
the netgpu module).  This logic and the codepath obviously needs
work, but suffices for a proof-of-concept.

Signed-off-by: Jonathan Lemon <jonathan.le...@gmail.com>
---
 net/core/skbuff.c | 27 +++++++++++++++++++++++++--
 1 file changed, 25 insertions(+), 2 deletions(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 2a391042be53..2b4176cab578 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -69,6 +69,7 @@
 #include <net/xfrm.h>
 #include <net/mpls.h>
 #include <net/mptcp.h>
+#include <net/netgpu.h>
 
 #include <linux/uaccess.h>
 #include <trace/events/skb.h>
@@ -590,6 +591,24 @@ static void skb_free_head(struct sk_buff *skb)
                kfree(head);
 }
 
+static void skb_netgpu_unref(struct skb_shared_info *shinfo)
+{
+       struct page *page;
+       int count;
+       int i;
+
+       /* pages attached for skbs for TX shouldn't come here, since
+        * the skb is not marked as "zc_netgpu". (only RX skbs have this).
+        * dummy page does come here, but always has elevated refc.
+        */
+       for (i = 0; i < shinfo->nr_frags; i++) {
+               page = skb_frag_page(&shinfo->frags[i]);
+               count = page_ref_dec_return(page);
+               if (count <= 2)
+                       __netgpu_put_page(g_ctx, page, false);
+       }
+}
+
 static void skb_release_data(struct sk_buff *skb)
 {
        struct skb_shared_info *shinfo = skb_shinfo(skb);
@@ -600,8 +619,12 @@ static void skb_release_data(struct sk_buff *skb)
                              &shinfo->dataref))
                return;
 
-       for (i = 0; i < shinfo->nr_frags; i++)
-               __skb_frag_unref(&shinfo->frags[i]);
+       if (skb->zc_netgpu && shinfo->nr_frags) {
+               skb_netgpu_unref(shinfo);
+       } else {
+               for (i = 0; i < shinfo->nr_frags; i++)
+                       __skb_frag_unref(&shinfo->frags[i]);
+       }
 
        if (shinfo->frag_list)
                kfree_skb_list(shinfo->frag_list);
-- 
2.24.1