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
> --- a/drivers/infiniband/core/nldev.c
> +++ 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);
> +
> + return err;
> +}
> +
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. Then thread 1
continues and calls the ops->dellink function which has been unloaded.
I think the above code needs a module reference before the
ib_device_put(), and a module dereference after calling ops->dellink.
Thoughts?
Steve.
