[PATCH net] devlink: Hold devlink lock on health reporter dump get

[PATCH net] devlink: Hold devlink lock on health reporter dump get

[Moshe Shemesh]

Devlink health dump get callback should take devlink lock as any other
devlink callback. Add devlink lock to the callback and to any call for
devlink_health_do_dump().

As devlink lock is added to any callback of dump, the reporter dump_lock
is now redundant and can be removed.

Fixes: d3efc2a6a6d8 ("net: devlink: remove devlink_mutex")
Signed-off-by: Moshe Shemesh <moshe@nvidia.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
---
 net/devlink/health.c | 30 ++++++++++++++++--------------
 1 file changed, 16 insertions(+), 14 deletions(-)

diff --git a/net/devlink/health.c b/net/devlink/health.c
index 638cad8d5c65..51e6e81e31bb 100644
--- a/net/devlink/health.c
+++ b/net/devlink/health.c
@@ -58,7 +58,6 @@ struct devlink_health_reporter {
 	struct devlink *devlink;
 	struct devlink_port *devlink_port;
 	struct devlink_fmsg *dump_fmsg;
-	struct mutex dump_lock; /* lock parallel read/write from dump buffers */
 	u64 graceful_period;
 	bool auto_recover;
 	bool auto_dump;
@@ -125,7 +124,6 @@ __devlink_health_reporter_create(struct devlink *devlink,
 	reporter->graceful_period = graceful_period;
 	reporter->auto_recover = !!ops->recover;
 	reporter->auto_dump = !!ops->dump;
-	mutex_init(&reporter->dump_lock);
 	return reporter;
 }
 
@@ -226,7 +224,6 @@ EXPORT_SYMBOL_GPL(devlink_health_reporter_create);
 static void
 devlink_health_reporter_free(struct devlink_health_reporter *reporter)
 {
-	mutex_destroy(&reporter->dump_lock);
 	if (reporter->dump_fmsg)
 		devlink_fmsg_free(reporter->dump_fmsg);
 	kfree(reporter);
@@ -625,10 +622,10 @@ int devlink_health_report(struct devlink_health_reporter *reporter,
 	}
 
 	if (reporter->auto_dump) {
-		mutex_lock(&reporter->dump_lock);
+		devl_lock(devlink);
 		/* store current dump of current error, for later analysis */
 		devlink_health_do_dump(reporter, priv_ctx, NULL);
-		mutex_unlock(&reporter->dump_lock);
+		devl_unlock(devlink);
 	}
 
 	if (!reporter->auto_recover)
@@ -1262,7 +1259,7 @@ int devlink_nl_cmd_health_reporter_diagnose_doit(struct sk_buff *skb,
 }
 
 static struct devlink_health_reporter *
-devlink_health_reporter_get_from_cb(struct netlink_callback *cb)
+devlink_health_reporter_get_from_cb_lock(struct netlink_callback *cb)
 {
 	const struct genl_info *info = genl_info_dump(cb);
 	struct devlink_health_reporter *reporter;
@@ -1272,10 +1269,12 @@ devlink_health_reporter_get_from_cb(struct netlink_callback *cb)
 	devlink = devlink_get_from_attrs_lock(sock_net(cb->skb->sk), attrs);
 	if (IS_ERR(devlink))
 		return NULL;
-	devl_unlock(devlink);
 
 	reporter = devlink_health_reporter_get_from_attrs(devlink, attrs);
-	devlink_put(devlink);
+	if (!reporter) {
+		devl_unlock(devlink);
+		devlink_put(devlink);
+	}
 	return reporter;
 }
 
@@ -1284,16 +1283,20 @@ int devlink_nl_cmd_health_reporter_dump_get_dumpit(struct sk_buff *skb,
 {
 	struct devlink_nl_dump_state *state = devlink_dump_state(cb);
 	struct devlink_health_reporter *reporter;
+	struct devlink *devlink;
 	int err;
 
-	reporter = devlink_health_reporter_get_from_cb(cb);
+	reporter = devlink_health_reporter_get_from_cb_lock(cb);
 	if (!reporter)
 		return -EINVAL;
 
-	if (!reporter->ops->dump)
+	devlink = reporter->devlink;
+	if (!reporter->ops->dump) {
+		devl_unlock(devlink);
+		devlink_put(devlink);
 		return -EOPNOTSUPP;
+	}
 
-	mutex_lock(&reporter->dump_lock);
 	if (!state->idx) {
 		err = devlink_health_do_dump(reporter, NULL, cb->extack);
 		if (err)
@@ -1309,7 +1312,8 @@ int devlink_nl_cmd_health_reporter_dump_get_dumpit(struct sk_buff *skb,
 	err = devlink_fmsg_dumpit(reporter->dump_fmsg, skb, cb,
 				  DEVLINK_CMD_HEALTH_REPORTER_DUMP_GET);
 unlock:
-	mutex_unlock(&reporter->dump_lock);
+	devl_unlock(devlink);
+	devlink_put(devlink);
 	return err;
 }
 
@@ -1326,9 +1330,7 @@ int devlink_nl_cmd_health_reporter_dump_clear_doit(struct sk_buff *skb,
 	if (!reporter->ops->dump)
 		return -EOPNOTSUPP;
 
-	mutex_lock(&reporter->dump_lock);
 	devlink_health_dump_clear(reporter);
-	mutex_unlock(&reporter->dump_lock);
 	return 0;
 }
 
-- 
2.27.0

Re: [PATCH net] devlink: Hold devlink lock on health reporter dump get

[Simon Horman]

On Sun, Oct 01, 2023 at 06:19:40PM +0300, Moshe Shemesh wrote:
> Devlink health dump get callback should take devlink lock as any other
> devlink callback. Add devlink lock to the callback and to any call for
> devlink_health_do_dump().
> 
> As devlink lock is added to any callback of dump, the reporter dump_lock
> is now redundant and can be removed.
> 
> Fixes: d3efc2a6a6d8 ("net: devlink: remove devlink_mutex")
> Signed-off-by: Moshe Shemesh <moshe@nvidia.com>
> Reviewed-by: Jiri Pirko <jiri@nvidia.com>

Reviewed-by: Simon Horman <horms@kernel.org>

Re: [PATCH net] devlink: Hold devlink lock on health reporter dump get

[Jakub Kicinski]

On Sun, 1 Oct 2023 18:19:40 +0300 Moshe Shemesh wrote:
> Devlink health dump get callback should take devlink lock as any other
> devlink callback. Add devlink lock to the callback and to any call for
> devlink_health_do_dump().
> 
> As devlink lock is added to any callback of dump, the reporter dump_lock
> is now redundant and can be removed.

I love the change but it needs more info in the commit message :)

 1. what exact / example but real problem are you solving?
 2. some words of reassurance that you checked all the drivers
    and the locking change should be safe (none of them take
    instance locks in reporter callbacks etc)
-- 
pw-bot: cr

Re: [PATCH net] devlink: Hold devlink lock on health reporter dump get

[Moshe Shemesh]

On 10/5/2023 2:39 AM, Jakub Kicinski wrote:
> External email: Use caution opening links or attachments
> 
> 
> On Sun, 1 Oct 2023 18:19:40 +0300 Moshe Shemesh wrote:
>> Devlink health dump get callback should take devlink lock as any other
>> devlink callback. Add devlink lock to the callback and to any call for
>> devlink_health_do_dump().
>>
>> As devlink lock is added to any callback of dump, the reporter dump_lock
>> is now redundant and can be removed.
> 
> I love the change but it needs more info in the commit message :)
> 
>   1. what exact / example but real problem are you solving?

Sure, will send v2

>   2. some words of reassurance that you checked all the drivers
>      and the locking change should be safe (none of them take
>      instance locks in reporter callbacks etc)

That's what I checked, looking at the code, I didn't find any devlink 
instance lock through all drivers health dump callbacks in current code: 
bnxt_fw_dump(), hinic_hw_reporter_dump(), hinic_fw_reporter_dump(), 
rvu_hw_nix_intr_dump() , rvu_hw_nix_gen_dump(), rvu_hw_nix_err_dump(), 
rvu_hw_nix_ras_dump(), rvu_hw_npa_intr_dump(), rvu_hw_npa_gen_dump(), 
rvu_hw_npa_err_dump(), rvu_hw_npa_ras_dump(), 
mlxsw_core_health_fw_fatal_dump(), mlx5e_rx_reporter_dump(), 
mlx5e_tx_reporter_dump(), mlx5_fw_reporter_dump(), 
mlx5_fw_fatal_reporter_dump(), qed_fw_fatal_reporter_dump(), 
nsim_dev_empty_reporter_dump(), nsim_dev_dummy_reporter_dump(), 
qlge_reporter_coredump()


> --
> pw-bot: cr