From: Leon Romanovsky <leon@kernel.org>
To: Jakub Kicinski <kuba@kernel.org>
Cc: "David S . Miller" <davem@davemloft.net>,
linux-kernel@vger.kernel.org, netdev@vger.kernel.org
Subject: Re: [PATCH net-next v1] netdevsim: Forbid devlink reload when adding or deleting ports
Date: Thu, 5 Aug 2021 16:51:31 +0300 [thread overview]
Message-ID: <YQvs4wRIIEDG6Dcu@unreal> (raw)
In-Reply-To: <20210805061547.3e0869ad@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
On Thu, Aug 05, 2021 at 06:15:47AM -0700, Jakub Kicinski wrote:
> On Thu, 5 Aug 2021 14:05:41 +0300 Leon Romanovsky wrote:
> > From: Leon Romanovsky <leonro@nvidia.com>
> >
> > In order to remove complexity in devlink core related to
> > devlink_reload_enable/disable, let's rewrite new_port/del_port
> > logic to rely on internal to netdevsim lock.
> >
> > We should protect only reload_down flow because it destroys nsim_dev,
> > which is needed for nsim_dev_port_add/nsim_dev_port_del to hold
> > port_list_lock.
>
> I don't understand why we only have to protect reload_down.
I assumed that if we succeeded to pass reload_down and we are in
reload_up stage, everything was already bailed out.
>
> What protects us from adding a port right after down? That'd hit a
> destroyed mutex, up wipes the port list etc...
You will have very similar crash to already existing one:
* parallel call to del_device and add_port will hit same issue.
The idea is not make netdevsim universally correct, but to ensure that
it doesn't crash immediately.
>
> > + nsim_bus_dev = nsim_dev->nsim_bus_dev;
> > + if (!mutex_trylock(&nsim_bus_dev->nsim_bus_reload_lock))
> > + return -EOPNOTSUPP;
>
> Why not -EBUSY?
This is what devlink_reload_disable() returns, so I kept same error.
It is not important at all.
What about the following change on top of this patch?
diff --git a/drivers/net/netdevsim/bus.c b/drivers/net/netdevsim/bus.c
index a29ec264119d..62d033a1a557 100644
--- a/drivers/net/netdevsim/bus.c
+++ b/drivers/net/netdevsim/bus.c
@@ -196,6 +196,11 @@ new_port_store(struct device *dev, struct device_attribute *attr,
if (!mutex_trylock(&nsim_bus_dev->nsim_bus_reload_lock))
return -EBUSY;
+ if (nsim_bus_dev->in_reload) {
+ mutex_unlock(&nsim_bus_dev->nsim_bus_reload_lock);
+ return -EBUSY;
+ }
+
ret = nsim_dev_port_add(nsim_bus_dev, NSIM_DEV_PORT_TYPE_PF, port_index);
mutex_unlock(&nsim_bus_dev->nsim_bus_reload_lock);
return ret ? ret : count;
@@ -221,6 +226,11 @@ del_port_store(struct device *dev, struct device_attribute *attr,
if (!mutex_trylock(&nsim_bus_dev->nsim_bus_reload_lock))
return -EBUSY;
+ if (nsim_bus_dev->in_reload) {
+ mutex_unlock(&nsim_bus_dev->nsim_bus_reload_lock);
+ return -EBUSY;
+ }
+
ret = nsim_dev_port_del(nsim_bus_dev, NSIM_DEV_PORT_TYPE_PF, port_index);
mutex_unlock(&nsim_bus_dev->nsim_bus_reload_lock);
return ret ? ret : count;
diff --git a/drivers/net/netdevsim/dev.c b/drivers/net/netdevsim/dev.c
index ff5714209b86..53068e184c90 100644
--- a/drivers/net/netdevsim/dev.c
+++ b/drivers/net/netdevsim/dev.c
@@ -878,6 +878,7 @@ static int nsim_dev_reload_down(struct devlink *devlink, bool netns_change,
mutex_unlock(&nsim_bus_dev->nsim_bus_reload_lock);
return -EOPNOTSUPP;
}
+ nsim_bus_dev->in_reload = true;
nsim_dev_reload_destroy(nsim_dev);
mutex_unlock(&nsim_bus_dev->nsim_bus_reload_lock);
@@ -889,17 +890,26 @@ static int nsim_dev_reload_up(struct devlink *devlink, enum devlink_reload_actio
struct netlink_ext_ack *extack)
{
struct nsim_dev *nsim_dev = devlink_priv(devlink);
+ struct nsim_bus_dev *nsim_bus_dev;
+ int ret;
+
+ nsim_bus_dev = nsim_dev->nsim_bus_dev;
+ mutex_lock(&nsim_bus_dev->nsim_bus_reload_lock);
+ nsim_bus_dev->in_reload = false;
if (nsim_dev->fail_reload) {
/* For testing purposes, user set debugfs fail_reload
* value to true. Fail right away.
*/
NL_SET_ERR_MSG_MOD(extack, "User setup the reload to fail for testing purposes");
+ mutex_unlock(&nsim_bus_dev->nsim_bus_reload_lock);
return -EINVAL;
}
*actions_performed = BIT(DEVLINK_RELOAD_ACTION_DRIVER_REINIT);
- return nsim_dev_reload_create(nsim_dev, extack);
+ ret = nsim_dev_reload_create(nsim_dev, extack);
+ mutex_unlock(&nsim_bus_dev->nsim_bus_reload_lock);
+ return ret;
}
static int nsim_dev_info_get(struct devlink *devlink,
diff --git a/drivers/net/netdevsim/netdevsim.h b/drivers/net/netdevsim/netdevsim.h
index 1c20bcbd9d91..793c86dc5a9c 100644
--- a/drivers/net/netdevsim/netdevsim.h
+++ b/drivers/net/netdevsim/netdevsim.h
@@ -362,6 +362,7 @@ struct nsim_bus_dev {
struct nsim_vf_config *vfconfigs;
/* Lock for devlink->reload_enabled in netdevsim module */
struct mutex nsim_bus_reload_lock;
+ bool in_reload;
bool init;
};
Thanks
next prev parent reply other threads:[~2021-08-05 13:51 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-05 11:02 [PATCH net-next] netdevsim: Forbid devlink reload when adding or deleting ports Leon Romanovsky
2021-08-05 11:05 ` [PATCH net-next v1] " Leon Romanovsky
2021-08-05 12:40 ` [PATCH net-next] " patchwork-bot+netdevbpf
2021-08-05 13:15 ` [PATCH net-next v1] " Jakub Kicinski
2021-08-05 13:51 ` Leon Romanovsky [this message]
2021-08-05 14:23 ` Jakub Kicinski
2021-08-05 14:33 ` Leon Romanovsky
2021-08-05 15:27 ` Jakub Kicinski
2021-08-05 17:35 ` Leon Romanovsky
2021-08-05 18:02 ` Leon Romanovsky
2021-08-05 19:12 ` Jakub Kicinski
2021-08-06 11:19 ` Leon Romanovsky
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