Re: [PATCH net-next 09/14] devlink: restart dump based on devlink instance ids (simple)

[Jiri Pirko <jiri@resnulli.us>]

Wed, Jan 04, 2023 at 05:16:31AM CET, kuba@kernel.org wrote:
>xarray gives each devlink instance an id and allows us to restart
>walk based on that id quite neatly. This is nice both from the
>perspective of code brevity and from the stability of the dump
>(devlink instances disappearing from before the resumption point
>will not cause inconsistent dumps).
>
>This patch takes care of simple cases where dump->idx counts
>devlink instances only.
>
>Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
>Signed-off-by: Jakub Kicinski <kuba@kernel.org>
>---
> net/devlink/core.c          |  2 +-
> net/devlink/devl_internal.h | 14 ++++++++++++++
> net/devlink/leftover.c      | 36 ++++++++----------------------------
> 3 files changed, 23 insertions(+), 29 deletions(-)
>
>diff --git a/net/devlink/core.c b/net/devlink/core.c
>index 3a99bf84632e..371d6821315d 100644
>--- a/net/devlink/core.c
>+++ b/net/devlink/core.c
>@@ -91,7 +91,7 @@ void devlink_put(struct devlink *devlink)
> 		call_rcu(&devlink->rcu, __devlink_put_rcu);
> }
> 
>-static struct devlink *
>+struct devlink *
> devlinks_xa_find_get(struct net *net, unsigned long *indexp,
> 		     void * (*xa_find_fn)(struct xarray *, unsigned long *,
> 					  unsigned long, xa_mark_t))
>diff --git a/net/devlink/devl_internal.h b/net/devlink/devl_internal.h
>index ee98f3bdcd33..a567ff77601d 100644
>--- a/net/devlink/devl_internal.h
>+++ b/net/devlink/devl_internal.h
>@@ -87,6 +87,10 @@ extern struct genl_family devlink_nl_family;
> 	     devlink; devlink = devlinks_xa_find_get_next(net, &index))
> 
> struct devlink *
>+devlinks_xa_find_get(struct net *net, unsigned long *indexp,
>+		     void * (*xa_find_fn)(struct xarray *, unsigned long *,
>+					  unsigned long, xa_mark_t));
>+struct devlink *
> devlinks_xa_find_get_first(struct net *net, unsigned long *indexp);
> struct devlink *
> devlinks_xa_find_get_next(struct net *net, unsigned long *indexp);
>@@ -104,6 +108,7 @@ enum devlink_multicast_groups {
> 
> /* state held across netlink dumps */
> struct devlink_nl_dump_state {
>+	unsigned long instance;
> 	int idx;
> 	union {
> 		/* DEVLINK_CMD_REGION_READ */
>@@ -117,6 +122,15 @@ struct devlink_nl_dump_state {
> 	};
> };
> 
>+/* Iterate over devlink pointers which were possible to get reference to.
>+ * devlink_put() needs to be called for each iterated devlink pointer
>+ * in loop body in order to release the reference.
>+ */
>+#define devlink_dump_for_each_instance_get(msg, dump, devlink)		\
>+	for (; (devlink = devlinks_xa_find_get(sock_net(msg->sk),	\

I undestand that the "dump" is zeroed at the beginning of dumpit call,
however, if you call this helper multiple times, the second iteration
would't not work.

Perhaps better to initialize instance=0 at the beginning of the loop to
make this helper calls behaviour independent on context.


>+					       &dump->instance, xa_find)); \
>+	     dump->instance++)
>+
> extern const struct genl_small_ops devlink_nl_ops[56];
> 
> struct devlink *devlink_get_from_attrs(struct net *net, struct nlattr **attrs);
>diff --git a/net/devlink/leftover.c b/net/devlink/leftover.c
>index e3cfb64990b4..0f24b321b0bb 100644
>--- a/net/devlink/leftover.c
>+++ b/net/devlink/leftover.c
>@@ -1319,17 +1319,9 @@ static int devlink_nl_cmd_get_dumpit(struct sk_buff *msg,
> {
> 	struct devlink_nl_dump_state *dump = devl_dump_state(cb);
> 	struct devlink *devlink;
>-	unsigned long index;
>-	int idx = 0;
> 	int err;
> 
>-	devlinks_xa_for_each_registered_get(sock_net(msg->sk), index, devlink) {
>-		if (idx < dump->idx) {
>-			idx++;
>-			devlink_put(devlink);
>-			continue;
>-		}
>-
>+	devlink_dump_for_each_instance_get(msg, dump, devlink) {

The name suggests on the first sight that you are iterating some dump,
which is slightly confusing. Perhaps better to have
"devlinks_xa_for_each_" in the prefix somehow?

	devlinks_xa_for_each_registered_get_dumping()

I know it is long :)


> 		devl_lock(devlink);
> 		err = devlink_nl_fill(msg, devlink, DEVLINK_CMD_NEW,
> 				      NETLINK_CB(cb->skb).portid,
>@@ -1339,10 +1331,8 @@ static int devlink_nl_cmd_get_dumpit(struct sk_buff *msg,
> 
> 		if (err)
> 			goto out;
>-		idx++;
> 	}
> out:
>-	dump->idx = idx;
> 	return msg->len;
> }
> 
>@@ -4872,13 +4862,13 @@ static int devlink_nl_cmd_selftests_get_dumpit(struct sk_buff *msg,
> {
> 	struct devlink_nl_dump_state *dump = devl_dump_state(cb);
> 	struct devlink *devlink;
>-	unsigned long index;
>-	int idx = 0;
> 	int err = 0;
> 
>-	devlinks_xa_for_each_registered_get(sock_net(msg->sk), index, devlink) {
>-		if (idx < dump->idx || !devlink->ops->selftest_check)
>-			goto inc;
>+	devlink_dump_for_each_instance_get(msg, dump, devlink) {
>+		if (!devlink->ops->selftest_check) {
>+			devlink_put(devlink);
>+			continue;
>+		}
> 
> 		devl_lock(devlink);
> 		err = devlink_nl_selftests_fill(msg, devlink,
>@@ -4890,15 +4880,13 @@ static int devlink_nl_cmd_selftests_get_dumpit(struct sk_buff *msg,
> 			devlink_put(devlink);
> 			break;
> 		}
>-inc:
>-		idx++;
>+
> 		devlink_put(devlink);
> 	}
> 
> 	if (err != -EMSGSIZE)
> 		return err;
> 
>-	dump->idx = idx;
> 	return msg->len;
> }
> 
>@@ -6747,14 +6735,9 @@ static int devlink_nl_cmd_info_get_dumpit(struct sk_buff *msg,
> {
> 	struct devlink_nl_dump_state *dump = devl_dump_state(cb);
> 	struct devlink *devlink;
>-	unsigned long index;
>-	int idx = 0;
> 	int err = 0;
> 
>-	devlinks_xa_for_each_registered_get(sock_net(msg->sk), index, devlink) {
>-		if (idx < dump->idx)
>-			goto inc;
>-
>+	devlink_dump_for_each_instance_get(msg, dump, devlink) {
> 		devl_lock(devlink);
> 		err = devlink_nl_info_fill(msg, devlink, DEVLINK_CMD_INFO_GET,
> 					   NETLINK_CB(cb->skb).portid,
>@@ -6767,15 +6750,12 @@ static int devlink_nl_cmd_info_get_dumpit(struct sk_buff *msg,
> 			devlink_put(devlink);
> 			break;
> 		}
>-inc:
>-		idx++;
> 		devlink_put(devlink);
> 	}
> 
> 	if (err != -EMSGSIZE)
> 		return err;
> 
>-	dump->idx = idx;
> 	return msg->len;
> }
> 
>-- 
>2.38.1
>