[PATCH net-next v3 0/7] net: ethtool: Introduce ethnl dump helpers

[PATCH net-next v3 0/7] net: ethtool: Introduce ethnl dump helpers

[Maxime Chevallier]

Hi everyone,

This is V3 for the ethnl dump support, allowing better handling of
per-phy dump but also any other dump operation that needs to dump more
than one message per netdev.

Changes in V3:
 - Fixed some typos and xmas tree issues
 - Added a missing check for EOPNOTSUPP in patch 1
 - Added missing kdoc
 - Added missing comments in phy_reply_size

Changes in V2:
 - Rebased on the netdev_lock work by Stanislav and the fixes from Eric
 - Fixed a bissectability issue
 - Fixed kdoc for the new ethnl ops and fields

V1: https://lore.kernel.org/netdev/20250305141938.319282-1-maxime.chevallier@bootlin.com/
V2: https://lore.kernel.org/netdev/20250308155440.267782-1-maxime.chevallier@bootlin.com/

As of today when using ethnl's default ops, the DUMP requests will
simply perform a GET for each netdev.

That hits limitations for commands that may return multiple messages for
a single netdev, such as :

 - RSS (listing contexts)
 - All PHY-specific commands (PLCA, PSE-PD, phy)
 - tsinfo (one item for the netdev +  one per phy)

 Commands that need a non-default DUMP support have to re-implement
 ->dumpit() themselves, which prevents using most of ethnl's internal
 circuitry.

This series therefore introduces a better support for dump operations in
ethnl.

The patches 1 and 2 introduce the support for filtered DUMPs, where an
ifindex/ifname can be passed in the request header for the DUMP
operation. This is for when we want to dump everything a netdev
supports, but without doing so for every single netdev. ethtool's
"--show-phys ethX" option for example performs a filtered dump.

Patch 3 introduces 3 new ethnl ops : 
 ->dump_start() to initialize a dump context
 ->dump_one_dev(), that can be implemented per-command to dump
 everything on a given netdev
 ->dump_done() to release the context

The default behaviour for dumps remains the same, calling the whole
->doit() path for each netdev.

Patch 4 introduces a set of ->dump_start(), ->dump_one_dev() and
->dump_done() callback implementations that can simply be plugged into
the existing commands that list objects per-phy, making the 
phy-targeting command behaviour more coherent.

Patch 5 uses that new set of helpers to rewrite the phy.c support, which
now uses the regulat ethnl_ops instead of fully custom genl ops. This
one is the hardest to review, sorry about that, I couldn't really manage
to incrementally rework that file :(

Patches 6 and 7 are where the new dump infra shines, adding per-netdev
per-phy dump support for PLCA and PSE-PD.

We could also consider converting tsinfo/tsconfig, rss and tunnels to
these new ->dump_***() operations as well, but that's out of this
series' scope.

Thanks,

Maxime

Maxime Chevallier (7):
  net: ethtool: netlink: Allow per-netdevice DUMP operations
  net: ethtool: netlink: Rename ethnl_default_dump_one
  net: ethtool: netlink: Introduce command-specific dump_one_dev
  net: ethtool: netlink: Introduce per-phy DUMP helpers
  net: ethtool: phy: Convert the PHY_GET command to generic phy dump
  net: ethtool: plca: Use per-PHY DUMP operations
  net: ethtool: pse-pd: Use per-PHY DUMP operations

 net/ethtool/netlink.c | 190 +++++++++++++++++------
 net/ethtool/netlink.h |  47 +++++-
 net/ethtool/phy.c     | 344 ++++++++++++------------------------------
 net/ethtool/plca.c    |  12 ++
 net/ethtool/pse-pd.c  |   6 +
 5 files changed, 309 insertions(+), 290 deletions(-)

-- 
2.48.1

[PATCH net-next v3 1/7] net: ethtool: netlink: Allow per-netdevice DUMP operations

[Maxime Chevallier]

We have a number of netlink commands in the ethnl family that may have
multiple objects to dump even for a single net_device, including :

 - PLCA, PSE-PD, phy: one message per PHY device
 - tsinfo: one message per timestamp source (netdev + phys)
 - rss: One per RSS context

To get this behaviour, these netlink commands need to roll a custom
->dumpit().

To prepare making per-netdev DUMP more generic in ethnl, introduce a
member in the ethnl ops to indicate if a given command may allow
pernetdev DUMPs (also referred to as filtered DUMPs).

Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
---
 net/ethtool/netlink.c | 45 +++++++++++++++++++++++++++++--------------
 net/ethtool/netlink.h |  2 ++
 2 files changed, 33 insertions(+), 14 deletions(-)

diff --git a/net/ethtool/netlink.c b/net/ethtool/netlink.c
index a163d40c6431..7adede5e4ff1 100644
--- a/net/ethtool/netlink.c
+++ b/net/ethtool/netlink.c
@@ -587,21 +587,38 @@ static int ethnl_default_dumpit(struct sk_buff *skb,
 	int ret = 0;
 
 	rcu_read_lock();
-	for_each_netdev_dump(net, dev, ctx->pos_ifindex) {
-		dev_hold(dev);
+	if (ctx->req_info->dev) {
+		dev = ctx->req_info->dev;
 		rcu_read_unlock();
+		/* Filtered DUMP request targeted to a single netdev. We already
+		 * hold a ref to the netdev from ->start()
+		 */
+		ret = ethnl_default_dump_one(skb, dev, ctx,
+					     genl_info_dump(cb));
+		rcu_read_lock();
+		netdev_put(ctx->req_info->dev, &ctx->req_info->dev_tracker);
 
-		ret = ethnl_default_dump_one(skb, dev, ctx, genl_info_dump(cb));
+		if (ret < 0 && ret != -EOPNOTSUPP && likely(skb->len))
+			ret = skb->len;
 
-		rcu_read_lock();
-		dev_put(dev);
+	} else {
+		for_each_netdev_dump(net, dev, ctx->pos_ifindex) {
+			dev_hold(dev);
+			rcu_read_unlock();
+
+			ret = ethnl_default_dump_one(skb, dev, ctx,
+						     genl_info_dump(cb));
+
+			rcu_read_lock();
+			dev_put(dev);
 
-		if (ret < 0 && ret != -EOPNOTSUPP) {
-			if (likely(skb->len))
-				ret = skb->len;
-			break;
+			if (ret < 0 && ret != -EOPNOTSUPP) {
+				if (likely(skb->len))
+					ret = skb->len;
+				break;
+			}
+			ret = 0;
 		}
-		ret = 0;
 	}
 	rcu_read_unlock();
 
@@ -635,10 +652,10 @@ static int ethnl_default_start(struct netlink_callback *cb)
 	}
 
 	ret = ethnl_default_parse(req_info, &info->info, ops, false);
-	if (req_info->dev) {
-		/* We ignore device specification in dump requests but as the
-		 * same parser as for non-dump (doit) requests is used, it
-		 * would take reference to the device if it finds one
+	if (req_info->dev && !ops->allow_pernetdev_dump) {
+		/* We ignore device specification in unfiltered dump requests
+		 * but as the same parser as for non-dump (doit) requests is
+		 * used, it would take reference to the device if it finds one
 		 */
 		netdev_put(req_info->dev, &req_info->dev_tracker);
 		req_info->dev = NULL;
diff --git a/net/ethtool/netlink.h b/net/ethtool/netlink.h
index ec6ab5443a6f..4aaa73282d6a 100644
--- a/net/ethtool/netlink.h
+++ b/net/ethtool/netlink.h
@@ -331,6 +331,7 @@ int ethnl_sock_priv_set(struct sk_buff *skb, struct net_device *dev, u32 portid,
  * @req_info_size:    size of request info
  * @reply_data_size:  size of reply data
  * @allow_nodev_do:   allow non-dump request with no device identification
+ * @allow_pernetdev_dump: allow filtering dump requests with ifname/ifindex
  * @set_ntf_cmd:      notification to generate on changes (SET)
  * @parse_request:
  *	Parse request except common header (struct ethnl_req_info). Common
@@ -388,6 +389,7 @@ struct ethnl_request_ops {
 	unsigned int		req_info_size;
 	unsigned int		reply_data_size;
 	bool			allow_nodev_do;
+	bool			allow_pernetdev_dump;
 	u8			set_ntf_cmd;
 
 	int (*parse_request)(struct ethnl_req_info *req_info,
-- 
2.48.1

[PATCH net-next v3 2/7] net: ethtool: netlink: Rename ethnl_default_dump_one

[Maxime Chevallier]

As we work on getting more objects out of a per-netdev DUMP, rename
ethnl_default_dump_one() into ethnl_default_dump_one_dev(), making it
explicit that this dumps everything for one netdev.

Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
---
 net/ethtool/netlink.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/net/ethtool/netlink.c b/net/ethtool/netlink.c
index 7adede5e4ff1..644c202d284d 100644
--- a/net/ethtool/netlink.c
+++ b/net/ethtool/netlink.c
@@ -540,9 +540,9 @@ static int ethnl_default_doit(struct sk_buff *skb, struct genl_info *info)
 	return ret;
 }
 
-static int ethnl_default_dump_one(struct sk_buff *skb, struct net_device *dev,
-				  const struct ethnl_dump_ctx *ctx,
-				  const struct genl_info *info)
+static int ethnl_default_dump_one_dev(struct sk_buff *skb, struct net_device *dev,
+				      const struct ethnl_dump_ctx *ctx,
+				      const struct genl_info *info)
 {
 	void *ehdr;
 	int ret;
@@ -593,8 +593,8 @@ static int ethnl_default_dumpit(struct sk_buff *skb,
 		/* Filtered DUMP request targeted to a single netdev. We already
 		 * hold a ref to the netdev from ->start()
 		 */
-		ret = ethnl_default_dump_one(skb, dev, ctx,
-					     genl_info_dump(cb));
+		ret = ethnl_default_dump_one_dev(skb, dev, ctx,
+						 genl_info_dump(cb));
 		rcu_read_lock();
 		netdev_put(ctx->req_info->dev, &ctx->req_info->dev_tracker);
 
@@ -606,8 +606,8 @@ static int ethnl_default_dumpit(struct sk_buff *skb,
 			dev_hold(dev);
 			rcu_read_unlock();
 
-			ret = ethnl_default_dump_one(skb, dev, ctx,
-						     genl_info_dump(cb));
+			ret = ethnl_default_dump_one_dev(skb, dev, ctx,
+							 genl_info_dump(cb));
 
 			rcu_read_lock();
 			dev_put(dev);
-- 
2.48.1

[PATCH net-next v3 3/7] net: ethtool: netlink: Introduce command-specific dump_one_dev

[Maxime Chevallier]

Prepare more generic ethnl DUMP hanldling, by allowing netlink commands
to register their own dump_one_dev() callback. This avoids having to
roll with a fully custom genl ->dumpit callback, allowing the re-use
of some ethnl plumbing.

Fallback to the default dump_one_dev behaviour when no custom callback
is found.

The command dump context is maintained within the ethnl_dump_ctx, that
we move in netlink.h so that command handlers can access it.

This context can be allocated/freed in new ->dump_start() and
->dump_done() callbacks.

Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
---
 net/ethtool/netlink.c | 62 +++++++++++++++++++++++++------------------
 net/ethtool/netlink.h | 35 ++++++++++++++++++++++++
 2 files changed, 71 insertions(+), 26 deletions(-)

diff --git a/net/ethtool/netlink.c b/net/ethtool/netlink.c
index 644c202d284d..2dc6086e1ab5 100644
--- a/net/ethtool/netlink.c
+++ b/net/ethtool/netlink.c
@@ -339,24 +339,6 @@ int ethnl_multicast(struct sk_buff *skb, struct net_device *dev)
 
 /* GET request helpers */
 
-/**
- * struct ethnl_dump_ctx - context structure for generic dumpit() callback
- * @ops:        request ops of currently processed message type
- * @req_info:   parsed request header of processed request
- * @reply_data: data needed to compose the reply
- * @pos_ifindex: saved iteration position - ifindex
- *
- * These parameters are kept in struct netlink_callback as context preserved
- * between iterations. They are initialized by ethnl_default_start() and used
- * in ethnl_default_dumpit() and ethnl_default_done().
- */
-struct ethnl_dump_ctx {
-	const struct ethnl_request_ops	*ops;
-	struct ethnl_req_info		*req_info;
-	struct ethnl_reply_data		*reply_data;
-	unsigned long			pos_ifindex;
-};
-
 static const struct ethnl_request_ops *
 ethnl_default_requests[__ETHTOOL_MSG_USER_CNT] = {
 	[ETHTOOL_MSG_STRSET_GET]	= &ethnl_strset_request_ops,
@@ -540,9 +522,9 @@ static int ethnl_default_doit(struct sk_buff *skb, struct genl_info *info)
 	return ret;
 }
 
-static int ethnl_default_dump_one_dev(struct sk_buff *skb, struct net_device *dev,
-				      const struct ethnl_dump_ctx *ctx,
-				      const struct genl_info *info)
+static int ethnl_default_dump_one(struct sk_buff *skb,
+				  const struct ethnl_dump_ctx *ctx,
+				  const struct genl_info *info)
 {
 	void *ehdr;
 	int ret;
@@ -553,15 +535,15 @@ static int ethnl_default_dump_one_dev(struct sk_buff *skb, struct net_device *de
 	if (!ehdr)
 		return -EMSGSIZE;
 
-	ethnl_init_reply_data(ctx->reply_data, ctx->ops, dev);
 	rtnl_lock();
-	netdev_lock_ops(dev);
+	netdev_lock_ops(ctx->reply_data->dev);
 	ret = ctx->ops->prepare_data(ctx->req_info, ctx->reply_data, info);
-	netdev_unlock_ops(dev);
+	netdev_unlock_ops(ctx->reply_data->dev);
 	rtnl_unlock();
 	if (ret < 0)
 		goto out;
-	ret = ethnl_fill_reply_header(skb, dev, ctx->ops->hdr_attr);
+	ret = ethnl_fill_reply_header(skb, ctx->reply_data->dev,
+				      ctx->ops->hdr_attr);
 	if (ret < 0)
 		goto out;
 	ret = ctx->ops->fill_reply(skb, ctx->req_info, ctx->reply_data);
@@ -569,11 +551,29 @@ static int ethnl_default_dump_one_dev(struct sk_buff *skb, struct net_device *de
 out:
 	if (ctx->ops->cleanup_data)
 		ctx->ops->cleanup_data(ctx->reply_data);
-	ctx->reply_data->dev = NULL;
+
 	if (ret < 0)
 		genlmsg_cancel(skb, ehdr);
 	else
 		genlmsg_end(skb, ehdr);
+
+	return ret;
+}
+
+static int ethnl_default_dump_one_dev(struct sk_buff *skb, struct net_device *dev,
+				      struct ethnl_dump_ctx *ctx,
+				      const struct genl_info *info)
+{
+	int ret;
+
+	ethnl_init_reply_data(ctx->reply_data, ctx->ops, dev);
+
+	if (ctx->ops->dump_one_dev)
+		ret = ctx->ops->dump_one_dev(skb, ctx, info);
+	else
+		ret = ethnl_default_dump_one(skb, ctx, info);
+
+	ctx->reply_data->dev = NULL;
 	return ret;
 }
 
@@ -606,6 +606,7 @@ static int ethnl_default_dumpit(struct sk_buff *skb,
 			dev_hold(dev);
 			rcu_read_unlock();
 
+			ctx->req_info->dev = dev;
 			ret = ethnl_default_dump_one_dev(skb, dev, ctx,
 							 genl_info_dump(cb));
 
@@ -668,6 +669,12 @@ static int ethnl_default_start(struct netlink_callback *cb)
 	ctx->reply_data = reply_data;
 	ctx->pos_ifindex = 0;
 
+	if (ctx->ops->dump_start) {
+		ret = ctx->ops->dump_start(ctx);
+		if (ret)
+			goto free_reply_data;
+	}
+
 	return 0;
 
 free_reply_data:
@@ -683,6 +690,9 @@ static int ethnl_default_done(struct netlink_callback *cb)
 {
 	struct ethnl_dump_ctx *ctx = ethnl_dump_context(cb);
 
+	if (ctx->ops->dump_done)
+		ctx->ops->dump_done(ctx);
+
 	kfree(ctx->reply_data);
 	kfree(ctx->req_info);
 
diff --git a/net/ethtool/netlink.h b/net/ethtool/netlink.h
index 4aaa73282d6a..79fe98190c64 100644
--- a/net/ethtool/netlink.h
+++ b/net/ethtool/netlink.h
@@ -307,6 +307,26 @@ struct ethnl_reply_data {
 	struct net_device		*dev;
 };
 
+/**
+ * struct ethnl_dump_ctx - context structure for generic dumpit() callback
+ * @ops:        request ops of currently processed message type
+ * @req_info:   parsed request header of processed request
+ * @reply_data: data needed to compose the reply
+ * @pos_ifindex: saved iteration position - ifindex
+ * @cmd_ctx: command-specific context to maintain across the dump.
+ *
+ * These parameters are kept in struct netlink_callback as context preserved
+ * between iterations. They are initialized by ethnl_default_start() and used
+ * in ethnl_default_dumpit() and ethnl_default_done().
+ */
+struct ethnl_dump_ctx {
+	const struct ethnl_request_ops	*ops;
+	struct ethnl_req_info		*req_info;
+	struct ethnl_reply_data		*reply_data;
+	unsigned long			pos_ifindex;
+	void				*cmd_ctx;
+};
+
 int ethnl_ops_begin(struct net_device *dev);
 void ethnl_ops_complete(struct net_device *dev);
 
@@ -373,6 +393,15 @@ int ethnl_sock_priv_set(struct sk_buff *skb, struct net_device *dev, u32 portid,
  *	 - 0 if no configuration has changed
  *	 - 1 if configuration changed and notification should be generated
  *	 - negative errno on errors
+ * @dump_start:
+ *	Optional callback to prepare a dump operation, should there be a need
+ *	to maintain some context across the dump.
+ * @dump_one_dev:
+ *	Optional callback to generate all messages for a given netdev. This
+ *	is relevant only when a request can produce different results for the
+ *	same netdev depending on command-specific attributes.
+ * @dump_done:
+ *	Optional callback to cleanup any context allocated in ->dump_start()
  *
  * Description of variable parts of GET request handling when using the
  * unified infrastructure. When used, a pointer to an instance of this
@@ -409,6 +438,12 @@ struct ethnl_request_ops {
 			    struct genl_info *info);
 	int (*set)(struct ethnl_req_info *req_info,
 		   struct genl_info *info);
+
+	int (*dump_start)(struct ethnl_dump_ctx *ctx);
+	int (*dump_one_dev)(struct sk_buff *skb,
+			    struct ethnl_dump_ctx *ctx,
+			    const struct genl_info *info);
+	void (*dump_done)(struct ethnl_dump_ctx *ctx);
 };
 
 /* request handlers */
-- 
2.48.1

[PATCH net-next v3 4/7] net: ethtool: netlink: Introduce per-phy DUMP helpers

[Maxime Chevallier]

As there are multiple ethnl commands that report messages based on
phy_device information, let's introduce a set of ethnl generic dump
helpers to allow DUMP support for each PHY on a given netdev.

This logic iterates over the phy_link_topology of each netdev (or a
single netdev for filtered DUMP), and call ethnl_default_dump_one() with
the req_info populated with ifindex + phyindex.

This allows re-using all the existing infra for phy-targetting commands
that already use ethnl generic helpers.

Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
---
 net/ethtool/netlink.c | 78 +++++++++++++++++++++++++++++++++++++++++++
 net/ethtool/netlink.h |  6 ++++
 2 files changed, 84 insertions(+)

diff --git a/net/ethtool/netlink.c b/net/ethtool/netlink.c
index 2dc6086e1ab5..821bc8b99306 100644
--- a/net/ethtool/netlink.c
+++ b/net/ethtool/netlink.c
@@ -560,6 +560,84 @@ static int ethnl_default_dump_one(struct sk_buff *skb,
 	return ret;
 }
 
+/* Specific context for phy-targeting command DUMP operatins. We keep in context
+ * the latest phy_index we dumped, in case of an interrupted DUMP.
+ */
+struct ethnl_dump_ctx_perphy {
+	unsigned long phy_index;
+};
+
+/**
+ * ethnl_dump_start_perphy() - Initialise a dump for PHY cmds
+ * @ctx: Generic ethnl dump context whose cmd_ctx will be initialized
+ *
+ * Initializes a dump context for ethnl commands that may return
+ * one message per PHY on a single netdev.
+ *
+ * Returns: 0 for success, a negative value for errors.
+ */
+int ethnl_dump_start_perphy(struct ethnl_dump_ctx *ctx)
+{
+	struct ethnl_dump_ctx_perphy *dump_ctx;
+
+	dump_ctx = kzalloc(sizeof(*dump_ctx), GFP_KERNEL);
+	if (!dump_ctx)
+		return -ENOMEM;
+
+	ctx->cmd_ctx = dump_ctx;
+
+	return 0;
+}
+
+/**
+ * ethnl_dump_done_perphy() - Releases the per-phy dump context
+ * @ctx: Generic ethnl dump context whose cmd_ctx will be released
+ */
+void ethnl_dump_done_perphy(struct ethnl_dump_ctx *ctx)
+{
+	kfree(ctx->cmd_ctx);
+}
+
+/**
+ * ethnl_dump_one_dev_perphy() - Dump all PHY-related messages for one netdev
+ * @skb: skb containing the DUMP result
+ * @ctx: Dump context. Will be kept across the DUMP operation.
+ * @info: Genl receive info
+ *
+ * Some commands are related to PHY devices attached to netdevs. As there may be
+ * multiple PHYs, this DUMP handler will populate the reply with one message per
+ * PHY on a single netdev.
+ *
+ * Returns: 0 for success or when nothing to do, a negative value otherwise.
+ */
+int ethnl_dump_one_dev_perphy(struct sk_buff *skb,
+			      struct ethnl_dump_ctx *ctx,
+			      const struct genl_info *info)
+{
+	struct ethnl_dump_ctx_perphy *dump_ctx = ctx->cmd_ctx;
+	struct net_device *dev = ctx->reply_data->dev;
+	struct phy_device_node *pdn;
+	int ret = 0;
+
+	if (!dev->link_topo)
+		return 0;
+
+	xa_for_each_start(&dev->link_topo->phys, dump_ctx->phy_index,
+			  pdn, dump_ctx->phy_index) {
+		ctx->req_info->phy_index = dump_ctx->phy_index;
+
+		/* We can re-use the original dump_one as ->prepare_data in
+		 * commands use ethnl_req_get_phydev(), which gets the PHY from
+		 * what's in req_info
+		 */
+		ret = ethnl_default_dump_one(skb, ctx, info);
+		if (ret)
+			break;
+	}
+
+	return ret;
+}
+
 static int ethnl_default_dump_one_dev(struct sk_buff *skb, struct net_device *dev,
 				      struct ethnl_dump_ctx *ctx,
 				      const struct genl_info *info)
diff --git a/net/ethtool/netlink.h b/net/ethtool/netlink.h
index 79fe98190c64..530a9b5c8b39 100644
--- a/net/ethtool/netlink.h
+++ b/net/ethtool/netlink.h
@@ -327,6 +327,12 @@ struct ethnl_dump_ctx {
 	void				*cmd_ctx;
 };
 
+/* Generic callbacks to be used by PHY targeting commands */
+int ethnl_dump_start_perphy(struct ethnl_dump_ctx *ctx);
+int ethnl_dump_one_dev_perphy(struct sk_buff *skb, struct ethnl_dump_ctx *ctx,
+			      const struct genl_info *info);
+void ethnl_dump_done_perphy(struct ethnl_dump_ctx *ctx);
+
 int ethnl_ops_begin(struct net_device *dev);
 void ethnl_ops_complete(struct net_device *dev);
 
-- 
2.48.1

[PATCH net-next v3 5/7] net: ethtool: phy: Convert the PHY_GET command to generic phy dump

[Maxime Chevallier]

Now that we have an infrastructure in ethnl for perphy DUMPs, we can get
rid of the custom ->doit and ->dumpit to deal with PHY listing commands.

As most of the code was custom, this basically means re-writing how we
deal with PHY listing.

Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
---
 net/ethtool/netlink.c |   9 +-
 net/ethtool/netlink.h |   4 -
 net/ethtool/phy.c     | 344 ++++++++++++------------------------------
 3 files changed, 105 insertions(+), 252 deletions(-)

diff --git a/net/ethtool/netlink.c b/net/ethtool/netlink.c
index 821bc8b99306..b32ddfe7cf88 100644
--- a/net/ethtool/netlink.c
+++ b/net/ethtool/netlink.c
@@ -382,6 +382,7 @@ ethnl_default_requests[__ETHTOOL_MSG_USER_CNT] = {
 	[ETHTOOL_MSG_MM_SET]		= &ethnl_mm_request_ops,
 	[ETHTOOL_MSG_TSCONFIG_GET]	= &ethnl_tsconfig_request_ops,
 	[ETHTOOL_MSG_TSCONFIG_SET]	= &ethnl_tsconfig_request_ops,
+	[ETHTOOL_MSG_PHY_GET]		= &ethnl_phy_request_ops,
 };
 
 static struct ethnl_dump_ctx *ethnl_dump_context(struct netlink_callback *cb)
@@ -1374,10 +1375,10 @@ static const struct genl_ops ethtool_genl_ops[] = {
 	},
 	{
 		.cmd	= ETHTOOL_MSG_PHY_GET,
-		.doit	= ethnl_phy_doit,
-		.start	= ethnl_phy_start,
-		.dumpit	= ethnl_phy_dumpit,
-		.done	= ethnl_phy_done,
+		.doit	= ethnl_default_doit,
+		.start	= ethnl_default_start,
+		.dumpit	= ethnl_default_dumpit,
+		.done	= ethnl_default_done,
 		.policy = ethnl_phy_get_policy,
 		.maxattr = ARRAY_SIZE(ethnl_phy_get_policy) - 1,
 	},
diff --git a/net/ethtool/netlink.h b/net/ethtool/netlink.h
index 530a9b5c8b39..60f16090640f 100644
--- a/net/ethtool/netlink.h
+++ b/net/ethtool/netlink.h
@@ -542,10 +542,6 @@ int ethnl_tunnel_info_dumpit(struct sk_buff *skb, struct netlink_callback *cb);
 int ethnl_act_module_fw_flash(struct sk_buff *skb, struct genl_info *info);
 int ethnl_rss_dump_start(struct netlink_callback *cb);
 int ethnl_rss_dumpit(struct sk_buff *skb, struct netlink_callback *cb);
-int ethnl_phy_start(struct netlink_callback *cb);
-int ethnl_phy_doit(struct sk_buff *skb, struct genl_info *info);
-int ethnl_phy_dumpit(struct sk_buff *skb, struct netlink_callback *cb);
-int ethnl_phy_done(struct netlink_callback *cb);
 int ethnl_tsinfo_start(struct netlink_callback *cb);
 int ethnl_tsinfo_dumpit(struct sk_buff *skb, struct netlink_callback *cb);
 int ethnl_tsinfo_done(struct netlink_callback *cb);
diff --git a/net/ethtool/phy.c b/net/ethtool/phy.c
index 1f590e8d75ed..88343fed7366 100644
--- a/net/ethtool/phy.c
+++ b/net/ethtool/phy.c
@@ -12,304 +12,160 @@
 #include <net/netdev_lock.h>
 
 struct phy_req_info {
-	struct ethnl_req_info		base;
-	struct phy_device_node		*pdn;
+	struct ethnl_req_info base;
 };
 
-#define PHY_REQINFO(__req_base) \
-	container_of(__req_base, struct phy_req_info, base)
+struct phy_reply_data {
+	struct ethnl_reply_data	base;
+	u32 phyindex;
+	char *drvname;
+	char *name;
+	unsigned int upstream_type;
+	char *upstream_sfp_name;
+	unsigned int upstream_index;
+	char *downstream_sfp_name;
+};
+
+#define PHY_REPDATA(__reply_base) \
+	container_of(__reply_base, struct phy_reply_data, base)
 
 const struct nla_policy ethnl_phy_get_policy[ETHTOOL_A_PHY_HEADER + 1] = {
 	[ETHTOOL_A_PHY_HEADER] = NLA_POLICY_NESTED(ethnl_header_policy),
 };
 
-/* Caller holds rtnl */
-static ssize_t
-ethnl_phy_reply_size(const struct ethnl_req_info *req_base,
-		     struct netlink_ext_ack *extack)
+static int phy_reply_size(const struct ethnl_req_info *req_info,
+			  const struct ethnl_reply_data *reply_data)
 {
-	struct phy_req_info *req_info = PHY_REQINFO(req_base);
-	struct phy_device_node *pdn = req_info->pdn;
-	struct phy_device *phydev = pdn->phy;
+	struct phy_reply_data *rep_data = PHY_REPDATA(reply_data);
 	size_t size = 0;
 
-	ASSERT_RTNL();
-
 	/* ETHTOOL_A_PHY_INDEX */
 	size += nla_total_size(sizeof(u32));
 
 	/* ETHTOOL_A_DRVNAME */
-	if (phydev->drv)
-		size += nla_total_size(strlen(phydev->drv->name) + 1);
+	if (rep_data->drvname)
+		size += nla_total_size(strlen(rep_data->drvname) + 1);
 
 	/* ETHTOOL_A_NAME */
-	size += nla_total_size(strlen(dev_name(&phydev->mdio.dev)) + 1);
+	size += nla_total_size(strlen(rep_data->name) + 1);
 
 	/* ETHTOOL_A_PHY_UPSTREAM_TYPE */
 	size += nla_total_size(sizeof(u32));
 
-	if (phy_on_sfp(phydev)) {
-		const char *upstream_sfp_name = sfp_get_name(pdn->parent_sfp_bus);
-
-		/* ETHTOOL_A_PHY_UPSTREAM_SFP_NAME */
-		if (upstream_sfp_name)
-			size += nla_total_size(strlen(upstream_sfp_name) + 1);
+	/* ETHTOOL_A_PHY_UPSTREAM_SFP_NAME */
+	if (rep_data->upstream_sfp_name)
+		size += nla_total_size(strlen(rep_data->upstream_sfp_name) + 1);
 
-		/* ETHTOOL_A_PHY_UPSTREAM_INDEX */
+	/* ETHTOOL_A_PHY_UPSTREAM_INDEX */
+	if (rep_data->upstream_index)
 		size += nla_total_size(sizeof(u32));
-	}
 
 	/* ETHTOOL_A_PHY_DOWNSTREAM_SFP_NAME */
-	if (phydev->sfp_bus) {
-		const char *sfp_name = sfp_get_name(phydev->sfp_bus);
-
-		if (sfp_name)
-			size += nla_total_size(strlen(sfp_name) + 1);
-	}
+	if (rep_data->downstream_sfp_name)
+		size += nla_total_size(strlen(rep_data->downstream_sfp_name) + 1);
 
 	return size;
 }
 
-static int
-ethnl_phy_fill_reply(const struct ethnl_req_info *req_base, struct sk_buff *skb)
+static int phy_prepare_data(const struct ethnl_req_info *req_info,
+			    struct ethnl_reply_data *reply_data,
+			    const struct genl_info *info)
 {
-	struct phy_req_info *req_info = PHY_REQINFO(req_base);
-	struct phy_device_node *pdn = req_info->pdn;
-	struct phy_device *phydev = pdn->phy;
-	enum phy_upstream ptype;
+	struct phy_link_topology *topo = reply_data->dev->link_topo;
+	struct phy_reply_data *rep_data = PHY_REPDATA(reply_data);
+	struct nlattr **tb = info->attrs;
+	struct phy_device_node *pdn;
+	struct phy_device *phydev;
 
-	ptype = pdn->upstream_type;
+	/* RTNL is held by the caller */
+	phydev = ethnl_req_get_phydev(req_info, tb, ETHTOOL_A_PHY_HEADER,
+				      info->extack);
+	if (IS_ERR_OR_NULL(phydev))
+		return -EOPNOTSUPP;
 
-	if (nla_put_u32(skb, ETHTOOL_A_PHY_INDEX, phydev->phyindex) ||
-	    nla_put_string(skb, ETHTOOL_A_PHY_NAME, dev_name(&phydev->mdio.dev)) ||
-	    nla_put_u32(skb, ETHTOOL_A_PHY_UPSTREAM_TYPE, ptype))
-		return -EMSGSIZE;
+	pdn = xa_load(&topo->phys, phydev->phyindex);
+	if (!pdn)
+		return -EOPNOTSUPP;
 
-	if (phydev->drv &&
-	    nla_put_string(skb, ETHTOOL_A_PHY_DRVNAME, phydev->drv->name))
-		return -EMSGSIZE;
+	rep_data->phyindex = phydev->phyindex;
+	rep_data->name = kstrdup(dev_name(&phydev->mdio.dev), GFP_KERNEL);
+	rep_data->drvname = kstrdup(phydev->drv->name, GFP_KERNEL);
+	rep_data->upstream_type = pdn->upstream_type;
 
-	if (ptype == PHY_UPSTREAM_PHY) {
+	if (pdn->upstream_type == PHY_UPSTREAM_PHY) {
 		struct phy_device *upstream = pdn->upstream.phydev;
-		const char *sfp_upstream_name;
-
-		/* Parent index */
-		if (nla_put_u32(skb, ETHTOOL_A_PHY_UPSTREAM_INDEX, upstream->phyindex))
-			return -EMSGSIZE;
-
-		if (pdn->parent_sfp_bus) {
-			sfp_upstream_name = sfp_get_name(pdn->parent_sfp_bus);
-			if (sfp_upstream_name &&
-			    nla_put_string(skb, ETHTOOL_A_PHY_UPSTREAM_SFP_NAME,
-					   sfp_upstream_name))
-				return -EMSGSIZE;
-		}
+		rep_data->upstream_index = upstream->phyindex;
 	}
 
-	if (phydev->sfp_bus) {
-		const char *sfp_name = sfp_get_name(phydev->sfp_bus);
+	if (pdn->parent_sfp_bus)
+		rep_data->upstream_sfp_name = kstrdup(sfp_get_name(pdn->parent_sfp_bus),
+						      GFP_KERNEL);
 
-		if (sfp_name &&
-		    nla_put_string(skb, ETHTOOL_A_PHY_DOWNSTREAM_SFP_NAME,
-				   sfp_name))
-			return -EMSGSIZE;
-	}
+	if (phydev->sfp_bus)
+		rep_data->downstream_sfp_name = kstrdup(sfp_get_name(phydev->sfp_bus),
+							GFP_KERNEL);
 
 	return 0;
 }
 
-static int ethnl_phy_parse_request(struct ethnl_req_info *req_base,
-				   struct nlattr **tb,
-				   struct netlink_ext_ack *extack)
+static int phy_fill_reply(struct sk_buff *skb,
+			  const struct ethnl_req_info *req_info,
+			  const struct ethnl_reply_data *reply_data)
 {
-	struct phy_link_topology *topo = req_base->dev->link_topo;
-	struct phy_req_info *req_info = PHY_REQINFO(req_base);
-	struct phy_device *phydev;
-
-	phydev = ethnl_req_get_phydev(req_base, tb, ETHTOOL_A_PHY_HEADER,
-				      extack);
-	if (!phydev)
-		return 0;
-
-	if (IS_ERR(phydev))
-		return PTR_ERR(phydev);
-
-	if (!topo)
-		return 0;
-
-	req_info->pdn = xa_load(&topo->phys, phydev->phyindex);
-
-	return 0;
-}
-
-int ethnl_phy_doit(struct sk_buff *skb, struct genl_info *info)
-{
-	struct phy_req_info req_info = {};
-	struct nlattr **tb = info->attrs;
-	struct sk_buff *rskb;
-	void *reply_payload;
-	int reply_len;
-	int ret;
-
-	ret = ethnl_parse_header_dev_get(&req_info.base,
-					 tb[ETHTOOL_A_PHY_HEADER],
-					 genl_info_net(info), info->extack,
-					 true);
-	if (ret < 0)
-		return ret;
-
-	rtnl_lock();
-	netdev_lock_ops(req_info.base.dev);
-
-	ret = ethnl_phy_parse_request(&req_info.base, tb, info->extack);
-	if (ret < 0)
-		goto err_unlock;
-
-	/* No PHY, return early */
-	if (!req_info.pdn)
-		goto err_unlock;
-
-	ret = ethnl_phy_reply_size(&req_info.base, info->extack);
-	if (ret < 0)
-		goto err_unlock;
-	reply_len = ret + ethnl_reply_header_size();
-
-	rskb = ethnl_reply_init(reply_len, req_info.base.dev,
-				ETHTOOL_MSG_PHY_GET_REPLY,
-				ETHTOOL_A_PHY_HEADER,
-				info, &reply_payload);
-	if (!rskb) {
-		ret = -ENOMEM;
-		goto err_unlock;
-	}
+	struct phy_reply_data *rep_data = PHY_REPDATA(reply_data);
 
-	ret = ethnl_phy_fill_reply(&req_info.base, rskb);
-	if (ret)
-		goto err_free_msg;
-
-	netdev_unlock_ops(req_info.base.dev);
-	rtnl_unlock();
-	ethnl_parse_header_dev_put(&req_info.base);
-	genlmsg_end(rskb, reply_payload);
-
-	return genlmsg_reply(rskb, info);
-
-err_free_msg:
-	nlmsg_free(rskb);
-err_unlock:
-	netdev_unlock_ops(req_info.base.dev);
-	rtnl_unlock();
-	ethnl_parse_header_dev_put(&req_info.base);
-	return ret;
-}
-
-struct ethnl_phy_dump_ctx {
-	struct phy_req_info	*phy_req_info;
-	unsigned long ifindex;
-	unsigned long phy_index;
-};
-
-int ethnl_phy_start(struct netlink_callback *cb)
-{
-	const struct genl_info *info = genl_info_dump(cb);
-	struct ethnl_phy_dump_ctx *ctx = (void *)cb->ctx;
-	int ret;
+	if (nla_put_u32(skb, ETHTOOL_A_PHY_INDEX, rep_data->phyindex) ||
+	    nla_put_string(skb, ETHTOOL_A_PHY_NAME, rep_data->name) ||
+	    nla_put_u32(skb, ETHTOOL_A_PHY_UPSTREAM_TYPE, rep_data->upstream_type))
+		return -EMSGSIZE;
 
-	BUILD_BUG_ON(sizeof(*ctx) > sizeof(cb->ctx));
+	if (rep_data->drvname &&
+	    nla_put_string(skb, ETHTOOL_A_PHY_DRVNAME, rep_data->drvname))
+		return -EMSGSIZE;
 
-	ctx->phy_req_info = kzalloc(sizeof(*ctx->phy_req_info), GFP_KERNEL);
-	if (!ctx->phy_req_info)
-		return -ENOMEM;
+	if (rep_data->upstream_index &&
+	    nla_put_u32(skb, ETHTOOL_A_PHY_UPSTREAM_INDEX,
+			rep_data->upstream_index))
+		return -EMSGSIZE;
 
-	ret = ethnl_parse_header_dev_get(&ctx->phy_req_info->base,
-					 info->attrs[ETHTOOL_A_PHY_HEADER],
-					 sock_net(cb->skb->sk), cb->extack,
-					 false);
-	ctx->ifindex = 0;
-	ctx->phy_index = 0;
+	if (rep_data->upstream_sfp_name &&
+	    nla_put_string(skb, ETHTOOL_A_PHY_UPSTREAM_SFP_NAME,
+			   rep_data->upstream_sfp_name))
+		return -EMSGSIZE;
 
-	if (ret)
-		kfree(ctx->phy_req_info);
+	if (rep_data->downstream_sfp_name &&
+	    nla_put_string(skb, ETHTOOL_A_PHY_DOWNSTREAM_SFP_NAME,
+			   rep_data->downstream_sfp_name))
+		return -EMSGSIZE;
 
-	return ret;
+	return 0;
 }
 
-int ethnl_phy_done(struct netlink_callback *cb)
+static void phy_cleanup_data(struct ethnl_reply_data *reply_data)
 {
-	struct ethnl_phy_dump_ctx *ctx = (void *)cb->ctx;
-
-	if (ctx->phy_req_info->base.dev)
-		ethnl_parse_header_dev_put(&ctx->phy_req_info->base);
-
-	kfree(ctx->phy_req_info);
+	struct phy_reply_data *rep_data = PHY_REPDATA(reply_data);
 
-	return 0;
+	kfree(rep_data->drvname);
+	kfree(rep_data->name);
+	kfree(rep_data->upstream_sfp_name);
+	kfree(rep_data->downstream_sfp_name);
 }
 
-static int ethnl_phy_dump_one_dev(struct sk_buff *skb, struct net_device *dev,
-				  struct netlink_callback *cb)
-{
-	struct ethnl_phy_dump_ctx *ctx = (void *)cb->ctx;
-	struct phy_req_info *pri = ctx->phy_req_info;
-	struct phy_device_node *pdn;
-	int ret = 0;
-	void *ehdr;
-
-	if (!dev->link_topo)
-		return 0;
-
-	xa_for_each_start(&dev->link_topo->phys, ctx->phy_index, pdn, ctx->phy_index) {
-		ehdr = ethnl_dump_put(skb, cb, ETHTOOL_MSG_PHY_GET_REPLY);
-		if (!ehdr) {
-			ret = -EMSGSIZE;
-			break;
-		}
-
-		ret = ethnl_fill_reply_header(skb, dev, ETHTOOL_A_PHY_HEADER);
-		if (ret < 0) {
-			genlmsg_cancel(skb, ehdr);
-			break;
-		}
-
-		pri->pdn = pdn;
-		ret = ethnl_phy_fill_reply(&pri->base, skb);
-		if (ret < 0) {
-			genlmsg_cancel(skb, ehdr);
-			break;
-		}
-
-		genlmsg_end(skb, ehdr);
-	}
+const struct ethnl_request_ops ethnl_phy_request_ops = {
+	.request_cmd		= ETHTOOL_MSG_PHY_GET,
+	.reply_cmd		= ETHTOOL_MSG_PHY_GET_REPLY,
+	.hdr_attr		= ETHTOOL_A_PHY_HEADER,
+	.req_info_size		= sizeof(struct phy_req_info),
+	.reply_data_size	= sizeof(struct phy_reply_data),
 
-	return ret;
-}
+	.prepare_data		= phy_prepare_data,
+	.reply_size		= phy_reply_size,
+	.fill_reply		= phy_fill_reply,
+	.cleanup_data		= phy_cleanup_data,
 
-int ethnl_phy_dumpit(struct sk_buff *skb, struct netlink_callback *cb)
-{
-	struct ethnl_phy_dump_ctx *ctx = (void *)cb->ctx;
-	struct net *net = sock_net(skb->sk);
-	struct net_device *dev;
-	int ret = 0;
-
-	rtnl_lock();
-
-	if (ctx->phy_req_info->base.dev) {
-		dev = ctx->phy_req_info->base.dev;
-		netdev_lock_ops(dev);
-		ret = ethnl_phy_dump_one_dev(skb, dev, cb);
-		netdev_unlock_ops(dev);
-	} else {
-		for_each_netdev_dump(net, dev, ctx->ifindex) {
-			netdev_lock_ops(dev);
-			ret = ethnl_phy_dump_one_dev(skb, dev, cb);
-			netdev_unlock_ops(dev);
-			if (ret)
-				break;
-
-			ctx->phy_index = 0;
-		}
-	}
-	rtnl_unlock();
+	.dump_start		= ethnl_dump_start_perphy,
+	.dump_one_dev		= ethnl_dump_one_dev_perphy,
+	.dump_done		= ethnl_dump_done_perphy,
 
-	return ret;
-}
+	.allow_pernetdev_dump	= true,
+};
-- 
2.48.1

[PATCH net-next v3 6/7] net: ethtool: plca: Use per-PHY DUMP operations

[Maxime Chevallier]

Leverage the per-phy ethnl DUMP helpers in case we have more that one
PLCA-able PHY on the link.

This is done for both PLCA status and PLCA config.

Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
---
 net/ethtool/plca.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/net/ethtool/plca.c b/net/ethtool/plca.c
index e1f7820a6158..2148ff607561 100644
--- a/net/ethtool/plca.c
+++ b/net/ethtool/plca.c
@@ -191,6 +191,12 @@ const struct ethnl_request_ops ethnl_plca_cfg_request_ops = {
 
 	.set			= ethnl_set_plca,
 	.set_ntf_cmd		= ETHTOOL_MSG_PLCA_NTF,
+
+	.dump_start		= ethnl_dump_start_perphy,
+	.dump_one_dev		= ethnl_dump_one_dev_perphy,
+	.dump_done		= ethnl_dump_done_perphy,
+
+	.allow_pernetdev_dump	= true,
 };
 
 // PLCA get status message -------------------------------------------------- //
@@ -268,4 +274,10 @@ const struct ethnl_request_ops ethnl_plca_status_request_ops = {
 	.prepare_data		= plca_get_status_prepare_data,
 	.reply_size		= plca_get_status_reply_size,
 	.fill_reply		= plca_get_status_fill_reply,
+
+	.dump_start		= ethnl_dump_start_perphy,
+	.dump_one_dev		= ethnl_dump_one_dev_perphy,
+	.dump_done		= ethnl_dump_done_perphy,
+
+	.allow_pernetdev_dump	= true,
 };
-- 
2.48.1

[PATCH net-next v3 7/7] net: ethtool: pse-pd: Use per-PHY DUMP operations

[Maxime Chevallier]

Leverage the per-phy ethnl DUMP helpers in case we have more that one
PSE PHY on the link.

Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
---
 net/ethtool/pse-pd.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/net/ethtool/pse-pd.c b/net/ethtool/pse-pd.c
index 4f6b99eab2a6..f3d14be8bdd9 100644
--- a/net/ethtool/pse-pd.c
+++ b/net/ethtool/pse-pd.c
@@ -314,4 +314,10 @@ const struct ethnl_request_ops ethnl_pse_request_ops = {
 
 	.set			= ethnl_set_pse,
 	/* PSE has no notification */
+
+	.dump_start		= ethnl_dump_start_perphy,
+	.dump_one_dev		= ethnl_dump_one_dev_perphy,
+	.dump_done		= ethnl_dump_done_perphy,
+
+	.allow_pernetdev_dump	= true,
 };
-- 
2.48.1

Re: [PATCH net-next v3 1/7] net: ethtool: netlink: Allow per-netdevice DUMP operations

[Paolo Abeni]

On 3/13/25 7:26 PM, Maxime Chevallier wrote:
> We have a number of netlink commands in the ethnl family that may have
> multiple objects to dump even for a single net_device, including :
> 
>  - PLCA, PSE-PD, phy: one message per PHY device
>  - tsinfo: one message per timestamp source (netdev + phys)
>  - rss: One per RSS context
> 
> To get this behaviour, these netlink commands need to roll a custom
> ->dumpit().
> 
> To prepare making per-netdev DUMP more generic in ethnl, introduce a
> member in the ethnl ops to indicate if a given command may allow
> pernetdev DUMPs (also referred to as filtered DUMPs).
> 
> Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
> ---
>  net/ethtool/netlink.c | 45 +++++++++++++++++++++++++++++--------------
>  net/ethtool/netlink.h |  2 ++
>  2 files changed, 33 insertions(+), 14 deletions(-)
> 
> diff --git a/net/ethtool/netlink.c b/net/ethtool/netlink.c
> index a163d40c6431..7adede5e4ff1 100644
> --- a/net/ethtool/netlink.c
> +++ b/net/ethtool/netlink.c
> @@ -587,21 +587,38 @@ static int ethnl_default_dumpit(struct sk_buff *skb,
>  	int ret = 0;
>  
>  	rcu_read_lock();

Maintain the RCU read lock here is IMHO confusing...

> -	for_each_netdev_dump(net, dev, ctx->pos_ifindex) {
> -		dev_hold(dev);
> +	if (ctx->req_info->dev) {
> +		dev = ctx->req_info->dev;

.. as this is refcounted.

I suggest to move the rcu_read_lock inside the if.


>  		rcu_read_unlock();
> +		/* Filtered DUMP request targeted to a single netdev. We already
> +		 * hold a ref to the netdev from ->start()
> +		 */
> +		ret = ethnl_default_dump_one(skb, dev, ctx,
> +					     genl_info_dump(cb));
> +		rcu_read_lock();
> +		netdev_put(ctx->req_info->dev, &ctx->req_info->dev_tracker);
>  
> -		ret = ethnl_default_dump_one(skb, dev, ctx, genl_info_dump(cb));
> +		if (ret < 0 && ret != -EOPNOTSUPP && likely(skb->len))
> +			ret = skb->len;
>  
> -		rcu_read_lock();
> -		dev_put(dev);
> +	} else {
> +		for_each_netdev_dump(net, dev, ctx->pos_ifindex) {
> +			dev_hold(dev);
> +			rcu_read_unlock();
> +
> +			ret = ethnl_default_dump_one(skb, dev, ctx,
> +						     genl_info_dump(cb));
> +
> +			rcu_read_lock();
> +			dev_put(dev);
>  
> -		if (ret < 0 && ret != -EOPNOTSUPP) {
> -			if (likely(skb->len))
> -				ret = skb->len;
> -			break;
> +			if (ret < 0 && ret != -EOPNOTSUPP) {
> +				if (likely(skb->len))
> +					ret = skb->len;

IMHO a bit too many levels of indentation. It's possibly better to move
this code in a separate helper.

Thanks,

Paolo

Re: [PATCH net-next v3 1/7] net: ethtool: netlink: Allow per-netdevice DUMP operations

[Maxime Chevallier]

On Fri, 21 Mar 2025 17:31:17 +0100
Paolo Abeni <pabeni@redhat.com> wrote:

> On 3/13/25 7:26 PM, Maxime Chevallier wrote:
> > We have a number of netlink commands in the ethnl family that may have
> > multiple objects to dump even for a single net_device, including :
> > 
> >  - PLCA, PSE-PD, phy: one message per PHY device
> >  - tsinfo: one message per timestamp source (netdev + phys)
> >  - rss: One per RSS context
> > 
> > To get this behaviour, these netlink commands need to roll a custom  
> > ->dumpit().  
> > 
> > To prepare making per-netdev DUMP more generic in ethnl, introduce a
> > member in the ethnl ops to indicate if a given command may allow
> > pernetdev DUMPs (also referred to as filtered DUMPs).
> > 
> > Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
> > ---
> >  net/ethtool/netlink.c | 45 +++++++++++++++++++++++++++++--------------
> >  net/ethtool/netlink.h |  2 ++
> >  2 files changed, 33 insertions(+), 14 deletions(-)
> > 
> > diff --git a/net/ethtool/netlink.c b/net/ethtool/netlink.c
> > index a163d40c6431..7adede5e4ff1 100644
> > --- a/net/ethtool/netlink.c
> > +++ b/net/ethtool/netlink.c
> > @@ -587,21 +587,38 @@ static int ethnl_default_dumpit(struct sk_buff *skb,
> >  	int ret = 0;
> >  
> >  	rcu_read_lock();  
> 
> Maintain the RCU read lock here is IMHO confusing...
> 
> > -	for_each_netdev_dump(net, dev, ctx->pos_ifindex) {
> > -		dev_hold(dev);
> > +	if (ctx->req_info->dev) {
> > +		dev = ctx->req_info->dev;  
> 
> .. as this is refcounted.
> 
> I suggest to move the rcu_read_lock inside the if.

Indeed, maybe not the best place indeed. I'll address that, thanks for
pointing this out

> 
> >  		rcu_read_unlock();
> > +		/* Filtered DUMP request targeted to a single netdev. We already
> > +		 * hold a ref to the netdev from ->start()
> > +		 */
> > +		ret = ethnl_default_dump_one(skb, dev, ctx,
> > +					     genl_info_dump(cb));
> > +		rcu_read_lock();
> > +		netdev_put(ctx->req_info->dev, &ctx->req_info->dev_tracker);
> >  
> > -		ret = ethnl_default_dump_one(skb, dev, ctx, genl_info_dump(cb));
> > +		if (ret < 0 && ret != -EOPNOTSUPP && likely(skb->len))
> > +			ret = skb->len;
> >  
> > -		rcu_read_lock();
> > -		dev_put(dev);
> > +	} else {
> > +		for_each_netdev_dump(net, dev, ctx->pos_ifindex) {
> > +			dev_hold(dev);
> > +			rcu_read_unlock();
> > +
> > +			ret = ethnl_default_dump_one(skb, dev, ctx,
> > +						     genl_info_dump(cb));
> > +
> > +			rcu_read_lock();
> > +			dev_put(dev);
> >  
> > -		if (ret < 0 && ret != -EOPNOTSUPP) {
> > -			if (likely(skb->len))
> > -				ret = skb->len;
> > -			break;
> > +			if (ret < 0 && ret != -EOPNOTSUPP) {
> > +				if (likely(skb->len))
> > +					ret = skb->len;  
> 
> IMHO a bit too many levels of indentation. It's possibly better to move
> this code in a separate helper.

That's true, not the prettiest piece of that patch. I'll refactor this
better then.

Thanks for the review,

Maxime