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Date: Thu, 5 Aug 2021 16:51:31 +0300 From: Leon Romanovsky <leon@...nel.org> To: Jakub Kicinski <kuba@...nel.org> Cc: "David S . Miller" <davem@...emloft.net>, linux-kernel@...r.kernel.org, netdev@...r.kernel.org Subject: Re: [PATCH net-next v1] netdevsim: Forbid devlink reload when adding or deleting ports 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@...dia.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
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