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Date: Tue, 17 Oct 2023 10:04:46 +0200
From: Jiri Pirko <jiri@...nulli.us>
To: Ido Schimmel <idosch@...dia.com>
Cc: netdev@...r.kernel.org, linux-pci@...r.kernel.org, davem@...emloft.net,
kuba@...nel.org, pabeni@...hat.com, edumazet@...gle.com,
bhelgaas@...gle.com, alex.williamson@...hat.com, lukas@...ner.de,
petrm@...dia.com, jiri@...dia.com, mlxsw@...dia.com
Subject: Re: [RFC PATCH net-next 03/12] devlink: Acquire device lock during
reload
Tue, Oct 17, 2023 at 09:42:48AM CEST, idosch@...dia.com wrote:
>Device drivers register with devlink from their probe routines (under
>the device lock) by acquiring the devlink instance lock and calling
>devl_register().
>
>Drivers that support a devlink reload usually implement the
>reload_{down, up}() operations in a similar fashion to their remove and
>probe routines, respectively.
>
>However, while the remove and probe routines are invoked with the device
>lock held, the reload operations are only invoked with the devlink
>instance lock held. It is therefore impossible for drivers to acquire
>the device lock from their reload operations, as this would result in
>lock inversion.
>
>The motivating use case for invoking the reload operations with the
>device lock held is in mlxsw which needs to trigger a PCI reset as part
>of the reload. The driver cannot call pci_reset_function() as this
>function acquires the device lock. Instead, it needs to call
>__pci_reset_function_locked which expects the device lock to be held.
>
>To that end, adjust devlink to always acquire the device lock before the
>devlink instance lock when performing a reload. Do that both when reload
>is triggered explicitly by user space and when it is triggered as part
>of netns dismantle.
>
>Tested the following flows with netdevsim and mlxsw while lockdep is
>enabled:
>
>netdevsim:
>
> # echo "10 1" > /sys/bus/netdevsim/new_device
> # devlink dev reload netdevsim/netdevsim10
> # ip netns add bla
> # devlink dev reload netdevsim/netdevsim10 netns bla
> # ip netns del bla
> # echo 10 > /sys/bus/netdevsim/del_device
>
>mlxsw:
>
> # devlink dev reload pci/0000:01:00.0
> # ip netns add bla
> # devlink dev reload pci/0000:01:00.0 netns bla
> # ip netns del bla
> # echo 1 > /sys/bus/pci/devices/0000\:01\:00.0/remove
> # echo 1 > /sys/bus/pci/rescan
>
>Signed-off-by: Ido Schimmel <idosch@...dia.com>
>---
> net/devlink/core.c | 4 ++--
> net/devlink/dev.c | 8 ++++++++
> net/devlink/devl_internal.h | 19 ++++++++++++++++++-
> net/devlink/health.c | 3 ++-
> net/devlink/netlink.c | 21 ++++++++++++++-------
> net/devlink/region.c | 3 ++-
> 6 files changed, 46 insertions(+), 12 deletions(-)
>
>diff --git a/net/devlink/core.c b/net/devlink/core.c
>index 5b8b692b8c76..0f866f2cbaf6 100644
>--- a/net/devlink/core.c
>+++ b/net/devlink/core.c
>@@ -502,14 +502,14 @@ static void __net_exit devlink_pernet_pre_exit(struct net *net)
> * all devlink instances from this namespace into init_net.
> */
> devlinks_xa_for_each_registered_get(net, index, devlink) {
>- devl_lock(devlink);
>+ devl_dev_lock(devlink, true);
> err = 0;
> if (devl_is_registered(devlink))
> err = devlink_reload(devlink, &init_net,
> DEVLINK_RELOAD_ACTION_DRIVER_REINIT,
> DEVLINK_RELOAD_LIMIT_UNSPEC,
> &actions_performed, NULL);
>- devl_unlock(devlink);
>+ devl_dev_unlock(devlink, true);
> devlink_put(devlink);
> if (err && err != -EOPNOTSUPP)
> pr_warn("Failed to reload devlink instance into init_net\n");
>diff --git a/net/devlink/dev.c b/net/devlink/dev.c
>index dc8039ca2b38..70cebe716187 100644
>--- a/net/devlink/dev.c
>+++ b/net/devlink/dev.c
>@@ -4,6 +4,7 @@
> * Copyright (c) 2016 Jiri Pirko <jiri@...lanox.com>
> */
>
>+#include <linux/device.h>
> #include <net/genetlink.h>
> #include <net/sock.h>
> #include "devl_internal.h"
>@@ -433,6 +434,13 @@ int devlink_reload(struct devlink *devlink, struct net *dest_net,
> struct net *curr_net;
> int err;
>
>+ /* Make sure the reload operations are invoked with the device lock
>+ * held to allow drivers to trigger functionality that expects it
>+ * (e.g., PCI reset) and to close possible races between these
>+ * operations and probe/remove.
>+ */
>+ device_lock_assert(devlink->dev);
>+
> memcpy(remote_reload_stats, devlink->stats.remote_reload_stats,
> sizeof(remote_reload_stats));
>
>diff --git a/net/devlink/devl_internal.h b/net/devlink/devl_internal.h
>index 741d1bf1bec8..a9c5e52c40a7 100644
>--- a/net/devlink/devl_internal.h
>+++ b/net/devlink/devl_internal.h
>@@ -3,6 +3,7 @@
> * Copyright (c) 2016 Jiri Pirko <jiri@...lanox.com>
> */
>
>+#include <linux/device.h>
> #include <linux/etherdevice.h>
> #include <linux/mutex.h>
> #include <linux/netdevice.h>
>@@ -96,6 +97,20 @@ static inline bool devl_is_registered(struct devlink *devlink)
> return xa_get_mark(&devlinks, devlink->index, DEVLINK_REGISTERED);
> }
>
>+static inline void devl_dev_lock(struct devlink *devlink, bool dev_lock)
>+{
>+ if (dev_lock)
>+ device_lock(devlink->dev);
>+ devl_lock(devlink);
>+}
>+
>+static inline void devl_dev_unlock(struct devlink *devlink, bool dev_lock)
>+{
>+ devl_unlock(devlink);
>+ if (dev_lock)
>+ device_unlock(devlink->dev);
>+}
>+
> typedef void devlink_rel_notify_cb_t(struct devlink *devlink, u32 obj_index);
> typedef void devlink_rel_cleanup_cb_t(struct devlink *devlink, u32 obj_index,
> u32 rel_index);
>@@ -113,6 +128,7 @@ int devlink_rel_devlink_handle_put(struct sk_buff *msg, struct devlink *devlink,
> /* Netlink */
> #define DEVLINK_NL_FLAG_NEED_PORT BIT(0)
> #define DEVLINK_NL_FLAG_NEED_DEVLINK_OR_PORT BIT(1)
>+#define DEVLINK_NL_FLAG_NEED_DEV_LOCK BIT(2)
>
> enum devlink_multicast_groups {
> DEVLINK_MCGRP_CONFIG,
>@@ -140,7 +156,8 @@ typedef int devlink_nl_dump_one_func_t(struct sk_buff *msg,
> int flags);
>
> struct devlink *
>-devlink_get_from_attrs_lock(struct net *net, struct nlattr **attrs);
>+devlink_get_from_attrs_lock(struct net *net, struct nlattr **attrs,
>+ bool dev_lock);
>
> int devlink_nl_dumpit(struct sk_buff *msg, struct netlink_callback *cb,
> devlink_nl_dump_one_func_t *dump_one);
>diff --git a/net/devlink/health.c b/net/devlink/health.c
>index 51e6e81e31bb..3c4c049c3636 100644
>--- a/net/devlink/health.c
>+++ b/net/devlink/health.c
>@@ -1266,7 +1266,8 @@ devlink_health_reporter_get_from_cb_lock(struct netlink_callback *cb)
> struct nlattr **attrs = info->attrs;
> struct devlink *devlink;
>
>- devlink = devlink_get_from_attrs_lock(sock_net(cb->skb->sk), attrs);
>+ devlink = devlink_get_from_attrs_lock(sock_net(cb->skb->sk), attrs,
>+ false);
> if (IS_ERR(devlink))
> return NULL;
>
>diff --git a/net/devlink/netlink.c b/net/devlink/netlink.c
>index 499304d9de49..14d598000d72 100644
>--- a/net/devlink/netlink.c
>+++ b/net/devlink/netlink.c
>@@ -124,7 +124,8 @@ int devlink_nl_msg_reply_and_new(struct sk_buff **msg, struct genl_info *info)
> }
>
> struct devlink *
>-devlink_get_from_attrs_lock(struct net *net, struct nlattr **attrs)
>+devlink_get_from_attrs_lock(struct net *net, struct nlattr **attrs,
>+ bool dev_lock)
> {
> struct devlink *devlink;
> unsigned long index;
>@@ -138,12 +139,12 @@ devlink_get_from_attrs_lock(struct net *net, struct nlattr **attrs)
> devname = nla_data(attrs[DEVLINK_ATTR_DEV_NAME]);
>
> devlinks_xa_for_each_registered_get(net, index, devlink) {
>- devl_lock(devlink);
>+ devl_dev_lock(devlink, dev_lock);
> if (devl_is_registered(devlink) &&
> strcmp(devlink->dev->bus->name, busname) == 0 &&
> strcmp(dev_name(devlink->dev), devname) == 0)
> return devlink;
>- devl_unlock(devlink);
>+ devl_dev_unlock(devlink, dev_lock);
> devlink_put(devlink);
> }
>
>@@ -155,9 +156,12 @@ static int __devlink_nl_pre_doit(struct sk_buff *skb, struct genl_info *info,
> {
> struct devlink_port *devlink_port;
> struct devlink *devlink;
>+ bool dev_lock;
> int err;
>
>- devlink = devlink_get_from_attrs_lock(genl_info_net(info), info->attrs);
>+ dev_lock = !!(flags & DEVLINK_NL_FLAG_NEED_DEV_LOCK);
I know you are aware, but just for the record: This conflicts
with my patchset "devlink: finish conversion to generated split_ops"
where I'm removing use of internal_flags. Ops that need this (should
be only reload) would need separate devlink_nl_pre/post_doit() helpers.
Otherwise the patch looks fine to me.
>+ devlink = devlink_get_from_attrs_lock(genl_info_net(info), info->attrs,
>+ dev_lock);
> if (IS_ERR(devlink))
> return PTR_ERR(devlink);
>
>@@ -177,7 +181,7 @@ static int __devlink_nl_pre_doit(struct sk_buff *skb, struct genl_info *info,
> return 0;
>
> unlock:
>- devl_unlock(devlink);
>+ devl_dev_unlock(devlink, dev_lock);
> devlink_put(devlink);
> return err;
> }
>@@ -205,9 +209,11 @@ void devlink_nl_post_doit(const struct genl_split_ops *ops,
> struct sk_buff *skb, struct genl_info *info)
> {
> struct devlink *devlink;
>+ bool dev_lock;
>
>+ dev_lock = !!(ops->internal_flags & DEVLINK_NL_FLAG_NEED_DEV_LOCK);
> devlink = info->user_ptr[0];
>- devl_unlock(devlink);
>+ devl_dev_unlock(devlink, dev_lock);
> devlink_put(devlink);
> }
>
>@@ -219,7 +225,7 @@ static int devlink_nl_inst_single_dumpit(struct sk_buff *msg,
> struct devlink *devlink;
> int err;
>
>- devlink = devlink_get_from_attrs_lock(sock_net(msg->sk), attrs);
>+ devlink = devlink_get_from_attrs_lock(sock_net(msg->sk), attrs, false);
> if (IS_ERR(devlink))
> return PTR_ERR(devlink);
> err = dump_one(msg, devlink, cb, flags | NLM_F_DUMP_FILTERED);
>@@ -420,6 +426,7 @@ static const struct genl_small_ops devlink_nl_small_ops[40] = {
> .validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
> .doit = devlink_nl_cmd_reload,
> .flags = GENL_ADMIN_PERM,
>+ .internal_flags = DEVLINK_NL_FLAG_NEED_DEV_LOCK,
> },
> {
> .cmd = DEVLINK_CMD_PARAM_SET,
>diff --git a/net/devlink/region.c b/net/devlink/region.c
>index d197cdb662db..30c6c49ec10b 100644
>--- a/net/devlink/region.c
>+++ b/net/devlink/region.c
>@@ -883,7 +883,8 @@ int devlink_nl_cmd_region_read_dumpit(struct sk_buff *skb,
>
> start_offset = state->start_offset;
>
>- devlink = devlink_get_from_attrs_lock(sock_net(cb->skb->sk), attrs);
>+ devlink = devlink_get_from_attrs_lock(sock_net(cb->skb->sk), attrs,
>+ false);
> if (IS_ERR(devlink))
> return PTR_ERR(devlink);
>
>--
>2.40.1
>
>
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