xsk: add id to umem

This commit adds an id to the umem structure. The id uniquely
identifies a umem instance, and will be exposed to user-space via the
socket monitoring interface.
Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

include/net/xdp_sock.h

@@ -42,6 +42,7 @@ struct xdp_umem {
 	struct work_struct work;
 	struct page **pgs;
 	u32 npgs;
+	int id;
 	struct net_device *dev;
 	struct xdp_umem_fq_reuse *fq_reuse;
 	u16 queue_id;

net/xdp/xdp_umem.c

@@ -13,12 +13,15 @@
 #include <linux/mm.h>
 #include <linux/netdevice.h>
 #include <linux/rtnetlink.h>
+#include <linux/idr.h>
 
 #include "xdp_umem.h"
 #include "xsk_queue.h"
 
 #define XDP_UMEM_MIN_CHUNK_SIZE 2048
 
+static DEFINE_IDA(umem_ida);
+
 void xdp_add_sk_umem(struct xdp_umem *umem, struct xdp_sock *xs)
 {
 	unsigned long flags;
@@ -183,6 +186,8 @@ static void xdp_umem_release(struct xdp_umem *umem)
 
 	xdp_umem_clear_dev(umem);
 
+	ida_simple_remove(&umem_ida, umem->id);
+
 	if (umem->fq) {
 		xskq_destroy(umem->fq);
 		umem->fq = NULL;
@@ -389,8 +394,16 @@ struct xdp_umem *xdp_umem_create(struct xdp_umem_reg *mr)
 	if (!umem)
 		return ERR_PTR(-ENOMEM);
 
+	err = ida_simple_get(&umem_ida, 0, 0, GFP_KERNEL);
+	if (err < 0) {
+		kfree(umem);
+		return ERR_PTR(err);
+	}
+	umem->id = err;
+
 	err = xdp_umem_reg(umem, mr);
 	if (err) {
+		ida_simple_remove(&umem_ida, umem->id);
 		kfree(umem);
 		return ERR_PTR(err);
 	}