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Message-Id: <20220725082925.366455-2-jiri@resnulli.us>
Date: Mon, 25 Jul 2022 10:29:14 +0200
From: Jiri Pirko <jiri@...nulli.us>
To: netdev@...r.kernel.org
Cc: davem@...emloft.net, kuba@...nel.org, idosch@...dia.com,
petrm@...dia.com, pabeni@...hat.com, edumazet@...gle.com,
mlxsw@...dia.com, saeedm@...dia.com, snelson@...sando.io
Subject: [patch net-next v4 01/12] net: devlink: make sure that devlink_try_get() works with valid pointer during xarray iteration
From: Jiri Pirko <jiri@...dia.com>
Remove dependency on devlink_mutex during devlinks xarray iteration.
The reason is that devlink_register/unregister() functions taking
devlink_mutex would deadlock during devlink reload operation of devlink
instance which registers/unregisters nested devlink instances.
The devlinks xarray consistency is ensured internally by xarray.
There is a reference taken when working with devlink using
devlink_try_get(). But there is no guarantee that devlink pointer
picked during xarray iteration is not freed before devlink_try_get()
is called.
Make sure that devlink_try_get() works with valid pointer.
Achieve it by:
1) Splitting devlink_put() so the completion is sent only
after grace period. Completion unblocks the devlink_unregister()
routine, which is followed-up by devlink_free()
2) During devlinks xa_array iteration, get devlink pointer from xa_array
holding RCU read lock and taking reference using devlink_try_get()
before unlock.
Signed-off-by: Jiri Pirko <jiri@...dia.com>
---
v3->v4:
- introduced an iteration helpers and convert to use them instead of
manually locking rcu_read_lock over xa_for_each_marked()
and devlink_try_get() couple
- converted devlink_get_from_attrs() to take reference during iteration
as well.
v2->v3:
- s/enf/end/ in devlink_put() comment
- added missing rcu_read_lock() call to info_get_dumpit()
- extended patch description by motivation
- removed an extra "by" from patch description
v1->v2:
- new patch (originally part of different patchset)
---
net/core/devlink.c | 171 +++++++++++++++++++++------------------------
1 file changed, 80 insertions(+), 91 deletions(-)
diff --git a/net/core/devlink.c b/net/core/devlink.c
index 98d79feeb3dc..c7abd928f389 100644
--- a/net/core/devlink.c
+++ b/net/core/devlink.c
@@ -70,6 +70,7 @@ struct devlink {
u8 reload_failed:1;
refcount_t refcount;
struct completion comp;
+ struct rcu_head rcu;
char priv[] __aligned(NETDEV_ALIGN);
};
@@ -221,8 +222,6 @@ static DEFINE_XARRAY_FLAGS(devlinks, XA_FLAGS_ALLOC);
/* devlink_mutex
*
* An overall lock guarding every operation coming from userspace.
- * It also guards devlink devices list and it is taken when
- * driver registers/unregisters it.
*/
static DEFINE_MUTEX(devlink_mutex);
@@ -232,10 +231,21 @@ struct net *devlink_net(const struct devlink *devlink)
}
EXPORT_SYMBOL_GPL(devlink_net);
+static void __devlink_put_rcu(struct rcu_head *head)
+{
+ struct devlink *devlink = container_of(head, struct devlink, rcu);
+
+ complete(&devlink->comp);
+}
+
void devlink_put(struct devlink *devlink)
{
if (refcount_dec_and_test(&devlink->refcount))
- complete(&devlink->comp);
+ /* Make sure unregister operation that may await the completion
+ * is unblocked only after all users are after the end of
+ * RCU grace period.
+ */
+ call_rcu(&devlink->rcu, __devlink_put_rcu);
}
struct devlink *__must_check devlink_try_get(struct devlink *devlink)
@@ -278,12 +288,55 @@ void devl_unlock(struct devlink *devlink)
}
EXPORT_SYMBOL_GPL(devl_unlock);
+static struct devlink *
+devlinks_xa_find_get(unsigned long *indexp, xa_mark_t filter,
+ void * (*xa_find_fn)(struct xarray *, unsigned long *,
+ unsigned long, xa_mark_t))
+{
+ struct devlink *devlink;
+
+ rcu_read_lock();
+retry:
+ devlink = xa_find_fn(&devlinks, indexp, ULONG_MAX, DEVLINK_REGISTERED);
+ if (!devlink)
+ goto unlock;
+ /* For a possible retry, the xa_find_after() should be always used */
+ xa_find_fn = xa_find_after;
+ if (!devlink_try_get(devlink))
+ goto retry;
+unlock:
+ rcu_read_unlock();
+ return devlink;
+}
+
+static struct devlink *devlinks_xa_find_get_first(unsigned long *indexp,
+ xa_mark_t filter)
+{
+ return devlinks_xa_find_get(indexp, filter, xa_find);
+}
+
+static struct devlink *devlinks_xa_find_get_next(unsigned long *indexp,
+ xa_mark_t filter)
+{
+ return devlinks_xa_find_get(indexp, filter, xa_find_after);
+}
+
+/* Iterate over devlink pointers which were possible to get reference to.
+ * devlink_put() needs to be called for each iterated devlink pointer
+ * in loop body in order to release the reference.
+ */
+#define devlinks_xa_for_each_get(index, devlink, filter) \
+ for (index = 0, devlink = devlinks_xa_find_get_first(&index, filter); \
+ devlink; devlink = devlinks_xa_find_get_next(&index, filter))
+
+#define devlinks_xa_for_each_registered_get(index, devlink) \
+ devlinks_xa_for_each_get(index, devlink, DEVLINK_REGISTERED)
+
static struct devlink *devlink_get_from_attrs(struct net *net,
struct nlattr **attrs)
{
struct devlink *devlink;
unsigned long index;
- bool found = false;
char *busname;
char *devname;
@@ -293,21 +346,15 @@ static struct devlink *devlink_get_from_attrs(struct net *net,
busname = nla_data(attrs[DEVLINK_ATTR_BUS_NAME]);
devname = nla_data(attrs[DEVLINK_ATTR_DEV_NAME]);
- lockdep_assert_held(&devlink_mutex);
-
- xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
+ devlinks_xa_for_each_registered_get(index, devlink) {
if (strcmp(devlink->dev->bus->name, busname) == 0 &&
strcmp(dev_name(devlink->dev), devname) == 0 &&
- net_eq(devlink_net(devlink), net)) {
- found = true;
- break;
- }
+ net_eq(devlink_net(devlink), net))
+ return devlink;
+ devlink_put(devlink);
}
- if (!found || !devlink_try_get(devlink))
- devlink = ERR_PTR(-ENODEV);
-
- return devlink;
+ return ERR_PTR(-ENODEV);
}
static struct devlink_port *devlink_port_get_by_index(struct devlink *devlink,
@@ -1329,10 +1376,7 @@ static int devlink_nl_cmd_rate_get_dumpit(struct sk_buff *msg,
int err = 0;
mutex_lock(&devlink_mutex);
- xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
- if (!devlink_try_get(devlink))
- continue;
-
+ devlinks_xa_for_each_registered_get(index, devlink) {
if (!net_eq(devlink_net(devlink), sock_net(msg->sk)))
goto retry;
@@ -1432,10 +1476,7 @@ static int devlink_nl_cmd_get_dumpit(struct sk_buff *msg,
int err;
mutex_lock(&devlink_mutex);
- xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
- if (!devlink_try_get(devlink))
- continue;
-
+ devlinks_xa_for_each_registered_get(index, devlink) {
if (!net_eq(devlink_net(devlink), sock_net(msg->sk))) {
devlink_put(devlink);
continue;
@@ -1495,10 +1536,7 @@ static int devlink_nl_cmd_port_get_dumpit(struct sk_buff *msg,
int err;
mutex_lock(&devlink_mutex);
- xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
- if (!devlink_try_get(devlink))
- continue;
-
+ devlinks_xa_for_each_registered_get(index, devlink) {
if (!net_eq(devlink_net(devlink), sock_net(msg->sk)))
goto retry;
@@ -2177,10 +2215,7 @@ static int devlink_nl_cmd_linecard_get_dumpit(struct sk_buff *msg,
int err;
mutex_lock(&devlink_mutex);
- xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
- if (!devlink_try_get(devlink))
- continue;
-
+ devlinks_xa_for_each_registered_get(index, devlink) {
if (!net_eq(devlink_net(devlink), sock_net(msg->sk)))
goto retry;
@@ -2449,10 +2484,7 @@ static int devlink_nl_cmd_sb_get_dumpit(struct sk_buff *msg,
int err;
mutex_lock(&devlink_mutex);
- xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
- if (!devlink_try_get(devlink))
- continue;
-
+ devlinks_xa_for_each_registered_get(index, devlink) {
if (!net_eq(devlink_net(devlink), sock_net(msg->sk)))
goto retry;
@@ -2601,10 +2633,7 @@ static int devlink_nl_cmd_sb_pool_get_dumpit(struct sk_buff *msg,
int err = 0;
mutex_lock(&devlink_mutex);
- xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
- if (!devlink_try_get(devlink))
- continue;
-
+ devlinks_xa_for_each_registered_get(index, devlink) {
if (!net_eq(devlink_net(devlink), sock_net(msg->sk)) ||
!devlink->ops->sb_pool_get)
goto retry;
@@ -2822,10 +2851,7 @@ static int devlink_nl_cmd_sb_port_pool_get_dumpit(struct sk_buff *msg,
int err = 0;
mutex_lock(&devlink_mutex);
- xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
- if (!devlink_try_get(devlink))
- continue;
-
+ devlinks_xa_for_each_registered_get(index, devlink) {
if (!net_eq(devlink_net(devlink), sock_net(msg->sk)) ||
!devlink->ops->sb_port_pool_get)
goto retry;
@@ -3071,10 +3097,7 @@ devlink_nl_cmd_sb_tc_pool_bind_get_dumpit(struct sk_buff *msg,
int err = 0;
mutex_lock(&devlink_mutex);
- xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
- if (!devlink_try_get(devlink))
- continue;
-
+ devlinks_xa_for_each_registered_get(index, devlink) {
if (!net_eq(devlink_net(devlink), sock_net(msg->sk)) ||
!devlink->ops->sb_tc_pool_bind_get)
goto retry;
@@ -5158,10 +5181,7 @@ static int devlink_nl_cmd_param_get_dumpit(struct sk_buff *msg,
int err = 0;
mutex_lock(&devlink_mutex);
- xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
- if (!devlink_try_get(devlink))
- continue;
-
+ devlinks_xa_for_each_registered_get(index, devlink) {
if (!net_eq(devlink_net(devlink), sock_net(msg->sk)))
goto retry;
@@ -5393,10 +5413,7 @@ static int devlink_nl_cmd_port_param_get_dumpit(struct sk_buff *msg,
int err = 0;
mutex_lock(&devlink_mutex);
- xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
- if (!devlink_try_get(devlink))
- continue;
-
+ devlinks_xa_for_each_registered_get(index, devlink) {
if (!net_eq(devlink_net(devlink), sock_net(msg->sk)))
goto retry;
@@ -5977,10 +5994,7 @@ static int devlink_nl_cmd_region_get_dumpit(struct sk_buff *msg,
int err = 0;
mutex_lock(&devlink_mutex);
- xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
- if (!devlink_try_get(devlink))
- continue;
-
+ devlinks_xa_for_each_registered_get(index, devlink) {
if (!net_eq(devlink_net(devlink), sock_net(msg->sk)))
goto retry;
@@ -6511,10 +6525,7 @@ static int devlink_nl_cmd_info_get_dumpit(struct sk_buff *msg,
int err = 0;
mutex_lock(&devlink_mutex);
- xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
- if (!devlink_try_get(devlink))
- continue;
-
+ devlinks_xa_for_each_registered_get(index, devlink) {
if (!net_eq(devlink_net(devlink), sock_net(msg->sk)))
goto retry;
@@ -7691,10 +7702,7 @@ devlink_nl_cmd_health_reporter_get_dumpit(struct sk_buff *msg,
int err;
mutex_lock(&devlink_mutex);
- xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
- if (!devlink_try_get(devlink))
- continue;
-
+ devlinks_xa_for_each_registered_get(index, devlink) {
if (!net_eq(devlink_net(devlink), sock_net(msg->sk)))
goto retry_rep;
@@ -7721,10 +7729,7 @@ devlink_nl_cmd_health_reporter_get_dumpit(struct sk_buff *msg,
devlink_put(devlink);
}
- xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
- if (!devlink_try_get(devlink))
- continue;
-
+ devlinks_xa_for_each_registered_get(index, devlink) {
if (!net_eq(devlink_net(devlink), sock_net(msg->sk)))
goto retry_port;
@@ -8291,10 +8296,7 @@ static int devlink_nl_cmd_trap_get_dumpit(struct sk_buff *msg,
int err;
mutex_lock(&devlink_mutex);
- xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
- if (!devlink_try_get(devlink))
- continue;
-
+ devlinks_xa_for_each_registered_get(index, devlink) {
if (!net_eq(devlink_net(devlink), sock_net(msg->sk)))
goto retry;
@@ -8518,10 +8520,7 @@ static int devlink_nl_cmd_trap_group_get_dumpit(struct sk_buff *msg,
int err;
mutex_lock(&devlink_mutex);
- xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
- if (!devlink_try_get(devlink))
- continue;
-
+ devlinks_xa_for_each_registered_get(index, devlink) {
if (!net_eq(devlink_net(devlink), sock_net(msg->sk)))
goto retry;
@@ -8832,10 +8831,7 @@ static int devlink_nl_cmd_trap_policer_get_dumpit(struct sk_buff *msg,
int err;
mutex_lock(&devlink_mutex);
- xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
- if (!devlink_try_get(devlink))
- continue;
-
+ devlinks_xa_for_each_registered_get(index, devlink) {
if (!net_eq(devlink_net(devlink), sock_net(msg->sk)))
goto retry;
@@ -9589,10 +9585,8 @@ void devlink_register(struct devlink *devlink)
ASSERT_DEVLINK_NOT_REGISTERED(devlink);
/* Make sure that we are in .probe() routine */
- mutex_lock(&devlink_mutex);
xa_set_mark(&devlinks, devlink->index, DEVLINK_REGISTERED);
devlink_notify_register(devlink);
- mutex_unlock(&devlink_mutex);
}
EXPORT_SYMBOL_GPL(devlink_register);
@@ -9609,10 +9603,8 @@ void devlink_unregister(struct devlink *devlink)
devlink_put(devlink);
wait_for_completion(&devlink->comp);
- mutex_lock(&devlink_mutex);
devlink_notify_unregister(devlink);
xa_clear_mark(&devlinks, devlink->index, DEVLINK_REGISTERED);
- mutex_unlock(&devlink_mutex);
}
EXPORT_SYMBOL_GPL(devlink_unregister);
@@ -12281,10 +12273,7 @@ static void __net_exit devlink_pernet_pre_exit(struct net *net)
* all devlink instances from this namespace into init_net.
*/
mutex_lock(&devlink_mutex);
- xa_for_each_marked(&devlinks, index, devlink, DEVLINK_REGISTERED) {
- if (!devlink_try_get(devlink))
- continue;
-
+ devlinks_xa_for_each_registered_get(index, devlink) {
if (!net_eq(devlink_net(devlink), net))
goto retry;
--
2.35.3
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