On 12/6/2018 2:42 PM, Steve Wise wrote:
> On 12/6/2018 1:26 PM, Jason Gunthorpe wrote:
>> On Thu, Dec 06, 2018 at 09:44:11AM -0600, Steve Wise wrote:
>>> Commenting on my own submission:
>>>
>>> On 12/5/2018 9:14 AM, Steve Wise wrote:
>>>> Add support for new LINK messages to allow adding and deleting rdma
>>>> interfaces. This will be used initially for soft rdma drivers which
>>>> instantiate device instances dynamically by the admin specifying a
>>>> netdev device to use. The rdma_rxe module will be the first user of
>>>> these messages.
>>>>
>>>> The design is modeled after RTNL_NEWLINK/DELLINK: rdma drivers
>>>> register with the rdma core if they provide link add/delete functions.
>>>> Each driver registers with a unique "type" string, that is used to
>>>> dispatch messages coming from user space. A new RDMA_NLDEV_ATTR
>>>> is defined for the "type" string. User mode will pass 3 attributes
>>>> in a NEWLINK message: RDMA_NLDEV_ATTR_DEV_NAME for the desired rdma
>>>> device name to be created, RDMA_NLDEV_ATTR_LINK_TYPE for the "type"
>>>> of link being added, and RDMA_NLDEV_ATTR_NDEV_NAME for the net_device
>>>> interface to use for this link. The DELLINK message will contain the
>>>> RDMA_NLDEV_ATTR_DEV_INDEX of the device to delete.
>>>>
>>>> Signed-off-by: Steve Wise <swise@xxxxxxxxxxxxxxxxxxxxx>
>>>> Reviewed-by: Leon Romanovsky <leonro@xxxxxxxxxxxx>
>>>> drivers/infiniband/core/nldev.c | 134 +++++++++++++++++++++++++++++++++++++++
>>>> include/rdma/ib_verbs.h | 2 +
>>>> include/rdma/rdma_netlink.h | 13 ++++
>>>> include/uapi/rdma/rdma_netlink.h | 11 +++-
>>>> 4 files changed, 158 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/infiniband/core/nldev.c b/drivers/infiniband/core/nldev.c
>>>> index 9abbadb9e366..b6d97c592074 100644
>>>> +++ b/drivers/infiniband/core/nldev.c
>>>> @@ -33,6 +33,7 @@
>>>> #include <linux/module.h>
>>>> #include <linux/pid.h>
>>>> #include <linux/pid_namespace.h>
>>>> +#include <linux/mutex.h>
>>>> #include <net/netlink.h>
>>>> #include <rdma/rdma_cm.h>
>>>> #include <rdma/rdma_netlink.h>
>>>> @@ -107,6 +108,8 @@
>>>> [RDMA_NLDEV_ATTR_DRIVER_U32] = { .type = NLA_U32 },
>>>> [RDMA_NLDEV_ATTR_DRIVER_S64] = { .type = NLA_S64 },
>>>> [RDMA_NLDEV_ATTR_DRIVER_U64] = { .type = NLA_U64 },
>>>> + [RDMA_NLDEV_ATTR_LINK_TYPE] = { .type = NLA_NUL_STRING,
>>>> + .len = RDMA_NLDEV_ATTR_ENTRY_STRLEN },
>>>> };
>>>>
>>>> static int put_driver_name_print_type(struct sk_buff *msg, const char *name,
>>>> @@ -1104,6 +1107,129 @@ static int nldev_res_get_pd_dumpit(struct sk_buff *skb,
>>>> return res_get_common_dumpit(skb, cb, RDMA_RESTRACK_PD);
>>>> }
>>>>
>>>> +static LIST_HEAD(link_ops);
>>>> +static DECLARE_RWSEM(link_ops_rwsem);
>>>> +
>>>> +static const struct rdma_link_ops *link_ops_get(const char *type)
>>>> +{
>>>> + const struct rdma_link_ops *ops;
>>>> +
>>>> + list_for_each_entry(ops, &link_ops, list) {
>>>> + if (!strcmp(ops->type, type))
>>>> + goto out;
>>>> + }
>>>> + ops = NULL;
>>>> +out:
>>>> + return ops;
>>>> +}
>>>> +
>>>> +void rdma_link_register(struct rdma_link_ops *ops)
>>>> +{
>>>> + down_write(&link_ops_rwsem);
>>>> + if (link_ops_get(ops->type)) {
>>>> + WARN_ONCE("Duplicate rdma_link_ops! %s\n", ops->type);
>>>> + goto out;
>>>> + }
>>>> + list_add(&ops->list, &link_ops);
>>>> +out:
>>>> + up_write(&link_ops_rwsem);
>>>> +}
>>>> +EXPORT_SYMBOL(rdma_link_register);
>>>> +
>>>> +void rdma_link_unregister(struct rdma_link_ops *ops)
>>>> +{
>>>> + down_write(&link_ops_rwsem);
>>>> + list_del(&ops->list);
>>>> + up_write(&link_ops_rwsem);
>>>> +}
>>>> +EXPORT_SYMBOL(rdma_link_unregister);
>>>> +
>>>> +static int nldev_newlink(struct sk_buff *skb, struct nlmsghdr *nlh,
>>>> + struct netlink_ext_ack *extack)
>>>> +{
>>>> + struct nlattr *tb[RDMA_NLDEV_ATTR_MAX];
>>>> + char ibdev_name[IB_DEVICE_NAME_MAX];
>>>> + const struct rdma_link_ops *ops;
>>>> + struct ib_device *device;
>>>> + char ndev_name[IFNAMSIZ];
>>>> + char type[IFNAMSIZ];
>>>> + int err;
>>>> +
>>>> + err = nlmsg_parse(nlh, 0, tb, RDMA_NLDEV_ATTR_MAX - 1,
>>>> + nldev_policy, extack);
>>>> + if (err || !tb[RDMA_NLDEV_ATTR_DEV_NAME] ||
>>>> + !tb[RDMA_NLDEV_ATTR_LINK_TYPE] || !tb[RDMA_NLDEV_ATTR_NDEV_NAME])
>>>> + return -EINVAL;
>>>> +
>>>> + nla_strlcpy(ibdev_name, tb[RDMA_NLDEV_ATTR_DEV_NAME],
>>>> + sizeof(ibdev_name));
>>>> + if (strchr(ibdev_name, '%'))
>>>> + return -EINVAL;
>>>> +
>>>> + nla_strlcpy(type, tb[RDMA_NLDEV_ATTR_LINK_TYPE], sizeof(type));
>>>> + nla_strlcpy(ndev_name, tb[RDMA_NLDEV_ATTR_NDEV_NAME],
>>>> + sizeof(ndev_name));
>>>> +
>>>> + down_read(&link_ops_rwsem);
>>>> + ops = link_ops_get(type);
>>>> +#ifdef CONFIG_MODULES
>>>> + if (!ops) {
>>>> + up_read(&link_ops_rwsem);
>>>> + request_module("rdma-link-%s", type);
>>>> + down_read(&link_ops_rwsem);
>>>> + ops = link_ops_get(type);
>>>> + }
>>>> +#endif
>>>> + if (ops) {
>>>> + device = ops->newlink(ibdev_name, ndev_name);
>>>> + if (IS_ERR(device))
>>>> + err = PTR_ERR(device);
>>>> + else
>>>> + device->link_ops = ops;
>>>> + } else {
>>>> + err = -ENODEV;
>>>> + }
>>>> + up_read(&link_ops_rwsem);
>>>> +
>>>> + return err;
>>>> +}
>>>> +
>>>> +static int nldev_dellink(struct sk_buff *skb, struct nlmsghdr *nlh,
>>>> + struct netlink_ext_ack *extack)
>>>> +{
>>>> + struct nlattr *tb[RDMA_NLDEV_ATTR_MAX];
>>>> + const struct rdma_link_ops *ops;
>>>> + struct device *dma_device;
>>>> + struct ib_device *device;
>>>> + u32 index;
>>>> + int err;
>>>> +
>>>> + err = nlmsg_parse(nlh, 0, tb, RDMA_NLDEV_ATTR_MAX - 1,
>>>> + nldev_policy, extack);
>>>> + if (err || !tb[RDMA_NLDEV_ATTR_DEV_INDEX])
>>>> + return -EINVAL;
>>>> +
>>>> + index = nla_get_u32(tb[RDMA_NLDEV_ATTR_DEV_INDEX]);
>>>> + device = ib_device_get_by_index(index);
>>>> + if (!device)
>>>> + return -EINVAL;
>>>> +
>>>> + ops = device->link_ops;
>>>> +
>>>> + /*
>>>> + * Deref the ib_device before deleting it. Otherwise we
>>>> + * deadlock unregistering the device. Hold a ref on the
>>>> + * underlying dma_device though to keep the memory around
>>>> + * until we're done.
>>>> + */
>>>> + dma_device = get_device(device->dma_device);
>>>> + ib_device_put(device);
>>>> + err = ops ? ops->dellink(device) : -ENODEV;
>>>> + put_device(dma_device);
>> What is the weirndness with dma_device? It should just be device
> Do you mean ibdev->dev?
>
>
>>> There is still a problem with the above code. If thread 1 is running
>>> this code and gets up to just after ib_device_put() but before calling
>>> ops->dellink, and then thread2 runs the rmmod code of rxe, thread 2 can
>>> remove the device and complete the module unload.
>> Yes.. You can't use a lot of the ib device outside the
>> ib_device_get_by_index/ib_device_put critical region.
>>
>> The driver, or perhaps the core code, has to be the one to unput it,
>> and the unput has to be done under proper locking to resolve the race.
> We could define that the link_ops dellink function must do the final
> ib_device_put(). That would work...
This requires exporting ib_device_put() for drivers to use.
Jason, This feature took a step back, imo, by using
ib_device_get_by_index() in nldev_dellink() and passing the struct
ib_device ptr vs simply passing the ibdev name string to the driver's
dellink() function and letting the driver deal with it all. I'm
inclined to go back to that approach. I don't see things getting
cleaner and simpler on this current path.
Do you?
