xsk: Create and free buffer pool independently from umem

Create and free the buffer pool independently from the umem. Move
these operations that are performed on the buffer pool from the
umem create and destroy functions to new create and destroy
functions just for the buffer pool. This so that in later commits
we can instantiate multiple buffer pools per umem when sharing a
umem between HW queues and/or devices. We also erradicate the
back pointer from the umem to the buffer pool as this will not
work when we introduce the possibility to have multiple buffer
pools per umem.

Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Björn Töpel <bjorn.topel@intel.com>
Link: https://lore.kernel.org/bpf/1598603189-32145-4-git-send-email-magnus.karlsson@intel.com

Author: magnus-karlsson

include/net/xdp_sock.h

@@ -20,13 +20,12 @@ struct xdp_buff;
 struct xdp_umem {
 	struct xsk_queue *fq;
 	struct xsk_queue *cq;
-	struct xsk_buff_pool *pool;
 	u64 size;
 	u32 headroom;
 	u32 chunk_size;
+	u32 chunks;
 	struct user_struct *user;
 	refcount_t users;
-	struct work_struct work;
 	struct page **pgs;
 	u32 npgs;
 	u16 queue_id;

include/net/xsk_buff_pool.h

@@ -14,6 +14,7 @@ struct xdp_rxq_info;
 struct xsk_queue;
 struct xdp_desc;
 struct xdp_umem;
+struct xdp_sock;
 struct device;
 struct page;
 
@@ -46,16 +47,22 @@ struct xsk_buff_pool {
 	struct xdp_umem *umem;
 	void *addrs;
 	struct device *dev;
+	refcount_t users;
+	struct work_struct work;
 	struct xdp_buff_xsk *free_heads[];
 };
 
 /* AF_XDP core. */
-struct xsk_buff_pool *xp_create(struct xdp_umem *umem, u32 chunks,
-				u32 chunk_size, u32 headroom, u64 size,
-				bool unaligned);
+struct xsk_buff_pool *xp_create_and_assign_umem(struct xdp_sock *xs,
+						struct xdp_umem *umem);
+int xp_assign_dev(struct xsk_buff_pool *pool, struct net_device *dev,
+		  u16 queue_id, u16 flags);
 void xp_set_fq(struct xsk_buff_pool *pool, struct xsk_queue *fq);
 void xp_destroy(struct xsk_buff_pool *pool);
 void xp_release(struct xdp_buff_xsk *xskb);
+void xp_get_pool(struct xsk_buff_pool *pool);
+void xp_put_pool(struct xsk_buff_pool *pool);
+void xp_clear_dev(struct xsk_buff_pool *pool);
 
 /* AF_XDP, and XDP core. */
 void xp_free(struct xdp_buff_xsk *xskb);

net/xdp/xdp_umem.c

@@ -47,160 +47,41 @@ void xdp_del_sk_umem(struct xdp_umem *umem, struct xdp_sock *xs)
 	spin_unlock_irqrestore(&umem->xsk_tx_list_lock, flags);
 }
 
-/* The umem is stored both in the _rx struct and the _tx struct as we do
- * not know if the device has more tx queues than rx, or the opposite.
- * This might also change during run time.
- */
-static int xsk_reg_pool_at_qid(struct net_device *dev,
-			       struct xsk_buff_pool *pool,
-			       u16 queue_id)
-{
-	if (queue_id >= max_t(unsigned int,
-			      dev->real_num_rx_queues,
-			      dev->real_num_tx_queues))
-		return -EINVAL;
-
-	if (queue_id < dev->real_num_rx_queues)
-		dev->_rx[queue_id].pool = pool;
-	if (queue_id < dev->real_num_tx_queues)
-		dev->_tx[queue_id].pool = pool;
-
-	return 0;
-}
-
-struct xsk_buff_pool *xsk_get_pool_from_qid(struct net_device *dev,
-					    u16 queue_id)
+static void xdp_umem_unpin_pages(struct xdp_umem *umem)
 {
-	if (queue_id < dev->real_num_rx_queues)
-		return dev->_rx[queue_id].pool;
-	if (queue_id < dev->real_num_tx_queues)
-		return dev->_tx[queue_id].pool;
+	unpin_user_pages_dirty_lock(umem->pgs, umem->npgs, true);
 
-	return NULL;
+	kfree(umem->pgs);
+	umem->pgs = NULL;
 }
-EXPORT_SYMBOL(xsk_get_pool_from_qid);
 
-static void xsk_clear_pool_at_qid(struct net_device *dev, u16 queue_id)
+static void xdp_umem_unaccount_pages(struct xdp_umem *umem)
 {
-	if (queue_id < dev->real_num_rx_queues)
-		dev->_rx[queue_id].pool = NULL;
-	if (queue_id < dev->real_num_tx_queues)
-		dev->_tx[queue_id].pool = NULL;
+	if (umem->user) {
+		atomic_long_sub(umem->npgs, &umem->user->locked_vm);
+		free_uid(umem->user);
+	}
 }
 
-int xdp_umem_assign_dev(struct xdp_umem *umem, struct net_device *dev,
-			u16 queue_id, u16 flags)
+void xdp_umem_assign_dev(struct xdp_umem *umem, struct net_device *dev,
+			 u16 queue_id)
 {
-	bool force_zc, force_copy;
-	struct netdev_bpf bpf;
-	int err = 0;
-
-	ASSERT_RTNL();
-
-	force_zc = flags & XDP_ZEROCOPY;
-	force_copy = flags & XDP_COPY;
-
-	if (force_zc && force_copy)
-		return -EINVAL;
-
-	if (xsk_get_pool_from_qid(dev, queue_id))
-		return -EBUSY;
-
-	err = xsk_reg_pool_at_qid(dev, umem->pool, queue_id);
-	if (err)
-		return err;
-
 	umem->dev = dev;
 	umem->queue_id = queue_id;
 
-	if (flags & XDP_USE_NEED_WAKEUP) {
-		umem->flags |= XDP_UMEM_USES_NEED_WAKEUP;
-		/* Tx needs to be explicitly woken up the first time.
-		 * Also for supporting drivers that do not implement this
-		 * feature. They will always have to call sendto().
-		 */
-		xsk_set_tx_need_wakeup(umem->pool);
-	}
-
 	dev_hold(dev);
-
-	if (force_copy)
-		/* For copy-mode, we are done. */
-		return 0;
-
-	if (!dev->netdev_ops->ndo_bpf || !dev->netdev_ops->ndo_xsk_wakeup) {
-		err = -EOPNOTSUPP;
-		goto err_unreg_umem;
-	}
-
-	bpf.command = XDP_SETUP_XSK_POOL;
-	bpf.xsk.pool = umem->pool;
-	bpf.xsk.queue_id = queue_id;
-
-	err = dev->netdev_ops->ndo_bpf(dev, &bpf);
-	if (err)
-		goto err_unreg_umem;
-
-	umem->zc = true;
-	return 0;
-
-err_unreg_umem:
-	if (!force_zc)
-		err = 0; /* fallback to copy mode */
-	if (err)
-		xsk_clear_pool_at_qid(dev, queue_id);
-	return err;
 }
 
 void xdp_umem_clear_dev(struct xdp_umem *umem)
 {
-	struct netdev_bpf bpf;
-	int err;
-
-	ASSERT_RTNL();
-
-	if (!umem->dev)
-		return;
-
-	if (umem->zc) {
-		bpf.command = XDP_SETUP_XSK_POOL;
-		bpf.xsk.pool = NULL;
-		bpf.xsk.queue_id = umem->queue_id;
-
-		err = umem->dev->netdev_ops->ndo_bpf(umem->dev, &bpf);
-
-		if (err)
-			WARN(1, "failed to disable umem!\n");
-	}
-
-	xsk_clear_pool_at_qid(umem->dev, umem->queue_id);
-
 	dev_put(umem->dev);
 	umem->dev = NULL;
 	umem->zc = false;
 }
 
-static void xdp_umem_unpin_pages(struct xdp_umem *umem)
-{
-	unpin_user_pages_dirty_lock(umem->pgs, umem->npgs, true);
-
-	kfree(umem->pgs);
-	umem->pgs = NULL;
-}
-
-static void xdp_umem_unaccount_pages(struct xdp_umem *umem)
-{
-	if (umem->user) {
-		atomic_long_sub(umem->npgs, &umem->user->locked_vm);
-		free_uid(umem->user);
-	}
-}
-
 static void xdp_umem_release(struct xdp_umem *umem)
 {
-	rtnl_lock();
 	xdp_umem_clear_dev(umem);
-	rtnl_unlock();
 
 	ida_simple_remove(&umem_ida, umem->id);
 
@@ -214,20 +95,12 @@ static void xdp_umem_release(struct xdp_umem *umem)
 		umem->cq = NULL;
 	}
 
-	xp_destroy(umem->pool);
 	xdp_umem_unpin_pages(umem);
 
 	xdp_umem_unaccount_pages(umem);
 	kfree(umem);
 }
 
-static void xdp_umem_release_deferred(struct work_struct *work)
-{
-	struct xdp_umem *umem = container_of(work, struct xdp_umem, work);
-
-	xdp_umem_release(umem);
-}
-
 void xdp_get_umem(struct xdp_umem *umem)
 {
 	refcount_inc(&umem->users);
@@ -238,10 +111,8 @@ void xdp_put_umem(struct xdp_umem *umem)
 	if (!umem)
 		return;
 
-	if (refcount_dec_and_test(&umem->users)) {
-		INIT_WORK(&umem->work, xdp_umem_release_deferred);
-		schedule_work(&umem->work);
-	}
+	if (refcount_dec_and_test(&umem->users))
+		xdp_umem_release(umem);
 }
 
 static int xdp_umem_pin_pages(struct xdp_umem *umem, unsigned long address)
@@ -357,6 +228,7 @@ static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)
 	umem->size = size;
 	umem->headroom = headroom;
 	umem->chunk_size = chunk_size;
+	umem->chunks = chunks;
 	umem->npgs = (u32)npgs;
 	umem->pgs = NULL;
 	umem->user = NULL;
@@ -374,16 +246,8 @@ static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)
 	if (err)
 		goto out_account;
 
-	umem->pool = xp_create(umem, chunks, chunk_size, headroom, size,
-			       unaligned_chunks);
-	if (!umem->pool) {
-		err = -ENOMEM;
-		goto out_pin;
-	}
 	return 0;
 
-out_pin:
-	xdp_umem_unpin_pages(umem);
 out_account:
 	xdp_umem_unaccount_pages(umem);
 	return err;

net/xdp/xdp_umem.h

@@ -8,8 +8,8 @@
 
 #include <net/xdp_sock_drv.h>
 
-int xdp_umem_assign_dev(struct xdp_umem *umem, struct net_device *dev,
-			u16 queue_id, u16 flags);
+void xdp_umem_assign_dev(struct xdp_umem *umem, struct net_device *dev,
+			 u16 queue_id);
 void xdp_umem_clear_dev(struct xdp_umem *umem);
 bool xdp_umem_validate_queues(struct xdp_umem *umem);
 void xdp_get_umem(struct xdp_umem *umem);