devlink: Change devlink health locking mechanism

The devlink health reporters create/destroy and user commands currently
use the devlink->lock as a locking mechanism. Different reporters have
different rules in the driver and are being created/destroyed during
different stages of driver load/unload/running. So during execution of a
reporter recover the flow can go through another reporter's destroy and
create. Such flow leads to deadlock trying to lock a mutex already
held.

With the new locking mechanism the different reporters share mutex lock
only to protect access to shared reporters list.
Added refcount per reporter, to protect the reporters from destroy while
being used.

Signed-off-by: Moshe Shemesh <moshe@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: Moshe Shemesh

include/net/devlink.h

@@ -32,6 +32,7 @@ struct devlink {
 	struct list_head region_list;
 	u32 snapshot_id;
 	struct list_head reporter_list;
+	struct mutex reporters_lock; /* protects reporter_list */
 	struct devlink_dpipe_headers *dpipe_headers;
 	const struct devlink_ops *ops;
 	struct device *dev;

net/core/devlink.c

@@ -20,6 +20,7 @@
 #include <linux/list.h>
 #include <linux/netdevice.h>
 #include <linux/spinlock.h>
+#include <linux/refcount.h>
 #include <rdma/ib_verbs.h>
 #include <net/netlink.h>
 #include <net/genetlink.h>
@@ -4432,6 +4433,7 @@ struct devlink_health_reporter {
 	u64 error_count;
 	u64 recovery_count;
 	u64 last_recovery_ts;
+	refcount_t refcount;
 };
 
 void *
@@ -4447,6 +4449,7 @@ devlink_health_reporter_find_by_name(struct devlink *devlink,
 {
 	struct devlink_health_reporter *reporter;
 
+	lockdep_assert_held(&devlink->reporters_lock);
 	list_for_each_entry(reporter, &devlink->reporter_list, list)
 		if (!strcmp(reporter->ops->name, reporter_name))
 			return reporter;
@@ -4470,7 +4473,7 @@ devlink_health_reporter_create(struct devlink *devlink,
 {
 	struct devlink_health_reporter *reporter;
 
-	mutex_lock(&devlink->lock);
+	mutex_lock(&devlink->reporters_lock);
 	if (devlink_health_reporter_find_by_name(devlink, ops->name)) {
 		reporter = ERR_PTR(-EEXIST);
 		goto unlock;
@@ -4494,9 +4497,10 @@ devlink_health_reporter_create(struct devlink *devlink,
 	reporter->graceful_period = graceful_period;
 	reporter->auto_recover = auto_recover;
 	mutex_init(&reporter->dump_lock);
+	refcount_set(&reporter->refcount, 1);
 	list_add_tail(&reporter->list, &devlink->reporter_list);
 unlock:
-	mutex_unlock(&devlink->lock);
+	mutex_unlock(&devlink->reporters_lock);
 	return reporter;
 }
 EXPORT_SYMBOL_GPL(devlink_health_reporter_create);
@@ -4509,10 +4513,12 @@ EXPORT_SYMBOL_GPL(devlink_health_reporter_create);
 void
 devlink_health_reporter_destroy(struct devlink_health_reporter *reporter)
 {
-	mutex_lock(&reporter->devlink->lock);
+	mutex_lock(&reporter->devlink->reporters_lock);
 	list_del(&reporter->list);
+	mutex_unlock(&reporter->devlink->reporters_lock);
+	while (refcount_read(&reporter->refcount) > 1)
+		msleep(100);
 	mutex_destroy(&reporter->dump_lock);
-	mutex_unlock(&reporter->devlink->lock);
 	if (reporter->dump_fmsg)
 		devlink_fmsg_free(reporter->dump_fmsg);
 	kfree(reporter);
@@ -4648,14 +4654,26 @@ static struct devlink_health_reporter *
 devlink_health_reporter_get_from_info(struct devlink *devlink,
 				      struct genl_info *info)
 {
+	struct devlink_health_reporter *reporter;
 	char *reporter_name;
 
 	if (!info->attrs[DEVLINK_ATTR_HEALTH_REPORTER_NAME])
 		return NULL;
 
 	reporter_name =
 		nla_data(info->attrs[DEVLINK_ATTR_HEALTH_REPORTER_NAME]);
-	return devlink_health_reporter_find_by_name(devlink, reporter_name);
+	mutex_lock(&devlink->reporters_lock);
+	reporter = devlink_health_reporter_find_by_name(devlink, reporter_name);
+	if (reporter)
+		refcount_inc(&reporter->refcount);
+	mutex_unlock(&devlink->reporters_lock);
+	return reporter;
+}
+
+static void
+devlink_health_reporter_put(struct devlink_health_reporter *reporter)
+{
+	refcount_dec(&reporter->refcount);
 }
 
 static int
@@ -4730,19 +4748,24 @@ static int devlink_nl_cmd_health_reporter_get_doit(struct sk_buff *skb,
 		return -EINVAL;
 
 	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
-	if (!msg)
-		return -ENOMEM;
+	if (!msg) {
+		err = -ENOMEM;
+		goto out;
+	}
 
 	err = devlink_nl_health_reporter_fill(msg, devlink, reporter,
 					      DEVLINK_CMD_HEALTH_REPORTER_GET,
 					      info->snd_portid, info->snd_seq,
 					      0);
 	if (err) {
 		nlmsg_free(msg);
-		return err;
+		goto out;
 	}
 
-	return genlmsg_reply(msg, info);
+	err = genlmsg_reply(msg, info);
+out:
+	devlink_health_reporter_put(reporter);
+	return err;
 }
 
 static int
@@ -4759,7 +4782,7 @@ devlink_nl_cmd_health_reporter_get_dumpit(struct sk_buff *msg,
 	list_for_each_entry(devlink, &devlink_list, list) {
 		if (!net_eq(devlink_net(devlink), sock_net(msg->sk)))
 			continue;
-		mutex_lock(&devlink->lock);
+		mutex_lock(&devlink->reporters_lock);
 		list_for_each_entry(reporter, &devlink->reporter_list,
 				    list) {
 			if (idx < start) {
@@ -4773,12 +4796,12 @@ devlink_nl_cmd_health_reporter_get_dumpit(struct sk_buff *msg,
 							      cb->nlh->nlmsg_seq,
 							      NLM_F_MULTI);
 			if (err) {
-				mutex_unlock(&devlink->lock);
+				mutex_unlock(&devlink->reporters_lock);
 				goto out;
 			}
 			idx++;
 		}
-		mutex_unlock(&devlink->lock);
+		mutex_unlock(&devlink->reporters_lock);
 	}
 out:
 	mutex_unlock(&devlink_mutex);
@@ -4793,15 +4816,18 @@ devlink_nl_cmd_health_reporter_set_doit(struct sk_buff *skb,
 {
 	struct devlink *devlink = info->user_ptr[0];
 	struct devlink_health_reporter *reporter;
+	int err;
 
 	reporter = devlink_health_reporter_get_from_info(devlink, info);
 	if (!reporter)
 		return -EINVAL;
 
 	if (!reporter->ops->recover &&
 	    (info->attrs[DEVLINK_ATTR_HEALTH_REPORTER_GRACEFUL_PERIOD] ||
-	     info->attrs[DEVLINK_ATTR_HEALTH_REPORTER_AUTO_RECOVER]))
-		return -EOPNOTSUPP;
+	     info->attrs[DEVLINK_ATTR_HEALTH_REPORTER_AUTO_RECOVER])) {
+		err = -EOPNOTSUPP;
+		goto out;
+	}
 
 	if (info->attrs[DEVLINK_ATTR_HEALTH_REPORTER_GRACEFUL_PERIOD])
 		reporter->graceful_period =
@@ -4811,20 +4837,28 @@ devlink_nl_cmd_health_reporter_set_doit(struct sk_buff *skb,
 		reporter->auto_recover =
 			nla_get_u8(info->attrs[DEVLINK_ATTR_HEALTH_REPORTER_AUTO_RECOVER]);
 
+	devlink_health_reporter_put(reporter);
 	return 0;
+out:
+	devlink_health_reporter_put(reporter);
+	return err;
 }
 
 static int devlink_nl_cmd_health_reporter_recover_doit(struct sk_buff *skb,
 						       struct genl_info *info)
 {
 	struct devlink *devlink = info->user_ptr[0];
 	struct devlink_health_reporter *reporter;
+	int err;
 
 	reporter = devlink_health_reporter_get_from_info(devlink, info);
 	if (!reporter)
 		return -EINVAL;
 
-	return devlink_health_reporter_recover(reporter, NULL);
+	err = devlink_health_reporter_recover(reporter, NULL);
+
+	devlink_health_reporter_put(reporter);
+	return err;
 }
 
 static int devlink_nl_cmd_health_reporter_diagnose_doit(struct sk_buff *skb,
@@ -4839,12 +4873,16 @@ static int devlink_nl_cmd_health_reporter_diagnose_doit(struct sk_buff *skb,
 	if (!reporter)
 		return -EINVAL;
 
-	if (!reporter->ops->diagnose)
+	if (!reporter->ops->diagnose) {
+		devlink_health_reporter_put(reporter);
 		return -EOPNOTSUPP;
+	}
 
 	fmsg = devlink_fmsg_alloc();
-	if (!fmsg)
+	if (!fmsg) {
+		devlink_health_reporter_put(reporter);
 		return -ENOMEM;
+	}
 
 	err = devlink_fmsg_obj_nest_start(fmsg);
 	if (err)
@@ -4863,6 +4901,7 @@ static int devlink_nl_cmd_health_reporter_diagnose_doit(struct sk_buff *skb,
 
 out:
 	devlink_fmsg_free(fmsg);
+	devlink_health_reporter_put(reporter);
 	return err;
 }
 
@@ -4877,8 +4916,10 @@ static int devlink_nl_cmd_health_reporter_dump_get_doit(struct sk_buff *skb,
 	if (!reporter)
 		return -EINVAL;
 
-	if (!reporter->ops->dump)
+	if (!reporter->ops->dump) {
+		devlink_health_reporter_put(reporter);
 		return -EOPNOTSUPP;
+	}
 
 	mutex_lock(&reporter->dump_lock);
 	err = devlink_health_do_dump(reporter, NULL);
@@ -4890,6 +4931,7 @@ static int devlink_nl_cmd_health_reporter_dump_get_doit(struct sk_buff *skb,
 
 out:
 	mutex_unlock(&reporter->dump_lock);
+	devlink_health_reporter_put(reporter);
 	return err;
 }
 
@@ -4904,12 +4946,15 @@ devlink_nl_cmd_health_reporter_dump_clear_doit(struct sk_buff *skb,
 	if (!reporter)
 		return -EINVAL;
 
-	if (!reporter->ops->dump)
+	if (!reporter->ops->dump) {
+		devlink_health_reporter_put(reporter);
 		return -EOPNOTSUPP;
+	}
 
 	mutex_lock(&reporter->dump_lock);
 	devlink_health_dump_clear(reporter);
 	mutex_unlock(&reporter->dump_lock);
+	devlink_health_reporter_put(reporter);
 	return 0;
 }
 
@@ -5191,29 +5236,33 @@ static const struct genl_ops devlink_nl_ops[] = {
 		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
 		.doit = devlink_nl_cmd_health_reporter_get_doit,
 		.dumpit = devlink_nl_cmd_health_reporter_get_dumpit,
-		.internal_flags = DEVLINK_NL_FLAG_NEED_DEVLINK,
+		.internal_flags = DEVLINK_NL_FLAG_NEED_DEVLINK |
+				  DEVLINK_NL_FLAG_NO_LOCK,
 		/* can be retrieved by unprivileged users */
 	},
 	{
 		.cmd = DEVLINK_CMD_HEALTH_REPORTER_SET,
 		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
 		.doit = devlink_nl_cmd_health_reporter_set_doit,
 		.flags = GENL_ADMIN_PERM,
-		.internal_flags = DEVLINK_NL_FLAG_NEED_DEVLINK,
+		.internal_flags = DEVLINK_NL_FLAG_NEED_DEVLINK |
+				  DEVLINK_NL_FLAG_NO_LOCK,
 	},
 	{
 		.cmd = DEVLINK_CMD_HEALTH_REPORTER_RECOVER,
 		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
 		.doit = devlink_nl_cmd_health_reporter_recover_doit,
 		.flags = GENL_ADMIN_PERM,
-		.internal_flags = DEVLINK_NL_FLAG_NEED_DEVLINK,
+		.internal_flags = DEVLINK_NL_FLAG_NEED_DEVLINK |
+				  DEVLINK_NL_FLAG_NO_LOCK,
 	},
 	{
 		.cmd = DEVLINK_CMD_HEALTH_REPORTER_DIAGNOSE,
 		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
 		.doit = devlink_nl_cmd_health_reporter_diagnose_doit,
 		.flags = GENL_ADMIN_PERM,
-		.internal_flags = DEVLINK_NL_FLAG_NEED_DEVLINK,
+		.internal_flags = DEVLINK_NL_FLAG_NEED_DEVLINK |
+				  DEVLINK_NL_FLAG_NO_LOCK,
 	},
 	{
 		.cmd = DEVLINK_CMD_HEALTH_REPORTER_DUMP_GET,
@@ -5284,6 +5333,7 @@ struct devlink *devlink_alloc(const struct devlink_ops *ops, size_t priv_size)
 	INIT_LIST_HEAD(&devlink->region_list);
 	INIT_LIST_HEAD(&devlink->reporter_list);
 	mutex_init(&devlink->lock);
+	mutex_init(&devlink->reporters_lock);
 	return devlink;
 }
 EXPORT_SYMBOL_GPL(devlink_alloc);
@@ -5326,6 +5376,7 @@ EXPORT_SYMBOL_GPL(devlink_unregister);
  */
 void devlink_free(struct devlink *devlink)
 {
+	mutex_destroy(&devlink->reporters_lock);
 	mutex_destroy(&devlink->lock);
 	WARN_ON(!list_empty(&devlink->reporter_list));
 	WARN_ON(!list_empty(&devlink->region_list));