[PATCH net-next] net: dqs: introduce NETIF_F_NO_BQL device feature

[Jason Xing <kerneljasonxing@gmail.com>]

From: Jason Xing <kernelxing@tencent.com>

Since commit 74293ea1c4db6 ("net: sysfs: Do not create sysfs for non
BQL device") limits the non-BQL driver not creating byte_queue_limits
directory, I found there is one exception, namely, virtio-net driver,
which should also be limited in netdev_uses_bql().

I decided to introduce a NO_BQL bit in device feature because
1) it can help us limit virtio-net driver for now.
2) if we found another non-BQL driver, we can take it into account.
3) we can replace all the driver meeting those two statements in
netdev_uses_bql() in future.

For now, I would like to make the first step to use this new bit for dqs
use instead of replacing/applying all the non-BQL drivers.

After this patch, 1) there is no byte_queue_limits directory in virtio-net
driver. 2) running ethtool -k eth1 shows "no-bql: on [fixed]".

Signed-off-by: Jason Xing <kernelxing@tencent.com>
---
 drivers/net/virtio_net.c        | 2 +-
 include/linux/netdev_features.h | 3 ++-
 net/core/net-sysfs.c            | 2 +-
 net/ethtool/common.c            | 1 +
 4 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 61a57d134544..619908fed14b 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -5634,7 +5634,7 @@ static int virtnet_probe(struct virtio_device *vdev)
 			   IFF_TX_SKB_NO_LINEAR;
 	dev->netdev_ops = &virtnet_netdev;
 	dev->stat_ops = &virtnet_stat_ops;
-	dev->features = NETIF_F_HIGHDMA;
+	dev->features = NETIF_F_HIGHDMA | NETIF_F_NO_BQL;
 
 	dev->ethtool_ops = &virtnet_ethtool_ops;
 	SET_NETDEV_DEV(dev, &vdev->dev);
diff --git a/include/linux/netdev_features.h b/include/linux/netdev_features.h
index 7c2d77d75a88..9bc603bb4227 100644
--- a/include/linux/netdev_features.h
+++ b/include/linux/netdev_features.h
@@ -14,7 +14,6 @@ typedef u64 netdev_features_t;
 enum {
 	NETIF_F_SG_BIT,			/* Scatter/gather IO. */
 	NETIF_F_IP_CSUM_BIT,		/* Can checksum TCP/UDP over IPv4. */
-	__UNUSED_NETIF_F_1,
 	NETIF_F_HW_CSUM_BIT,		/* Can checksum all the packets. */
 	NETIF_F_IPV6_CSUM_BIT,		/* Can checksum TCP/UDP over IPV6 */
 	NETIF_F_HIGHDMA_BIT,		/* Can DMA to high memory. */
@@ -91,6 +90,7 @@ enum {
 	NETIF_F_HW_HSR_FWD_BIT,		/* Offload HSR forwarding */
 	NETIF_F_HW_HSR_DUP_BIT,		/* Offload HSR duplication */
 
+	NETIF_F_NO_BQL_BIT,		/* non-BQL driver */
 	/*
 	 * Add your fresh new feature above and remember to update
 	 * netdev_features_strings[] in net/ethtool/common.c and maybe
@@ -168,6 +168,7 @@ enum {
 #define NETIF_F_HW_HSR_TAG_RM	__NETIF_F(HW_HSR_TAG_RM)
 #define NETIF_F_HW_HSR_FWD	__NETIF_F(HW_HSR_FWD)
 #define NETIF_F_HW_HSR_DUP	__NETIF_F(HW_HSR_DUP)
+#define NETIF_F_NO_BQL		__NETIF_F(NO_BQL)
 
 /* Finds the next feature with the highest number of the range of start-1 till 0.
  */
diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index 4c27a360c294..ff397a76f1fe 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -1764,7 +1764,7 @@ static const struct kobj_type netdev_queue_ktype = {
 
 static bool netdev_uses_bql(const struct net_device *dev)
 {
-	if (dev->features & NETIF_F_LLTX ||
+	if (dev->features & (NETIF_F_LLTX | NETIF_F_NO_BQL) ||
 	    dev->priv_flags & IFF_NO_QUEUE)
 		return false;
 
diff --git a/net/ethtool/common.c b/net/ethtool/common.c
index 6b2a360dcdf0..efa7ac4158ce 100644
--- a/net/ethtool/common.c
+++ b/net/ethtool/common.c
@@ -74,6 +74,7 @@ const char netdev_features_strings[NETDEV_FEATURE_COUNT][ETH_GSTRING_LEN] = {
 	[NETIF_F_HW_HSR_TAG_RM_BIT] =	 "hsr-tag-rm-offload",
 	[NETIF_F_HW_HSR_FWD_BIT] =	 "hsr-fwd-offload",
 	[NETIF_F_HW_HSR_DUP_BIT] =	 "hsr-dup-offload",
+	[NETIF_F_NO_BQL_BIT] =		 "no-bql",
 };
 
 const char
-- 
2.37.3