Re: [PATCH v7 06/25] RDMA/rtrs: client: main functionality

[Leon Romanovsky <leon@kernel.org>]

On Thu, Jan 16, 2020 at 01:58:56PM +0100, Jack Wang wrote:
> From: Jack Wang <jinpu.wang@cloud.ionos.com>
>
> This is main functionality of rtrs-client module, which manages
> set of RDMA connections for each rtrs session, does multipathing,
> load balancing and failover of RDMA requests.
>
> Signed-off-by: Danil Kipnis <danil.kipnis@cloud.ionos.com>
> Signed-off-by: Jack Wang <jinpu.wang@cloud.ionos.com>
> ---
>  drivers/infiniband/ulp/rtrs/rtrs-clt.c | 2967 ++++++++++++++++++++++++
>  1 file changed, 2967 insertions(+)
>  create mode 100644 drivers/infiniband/ulp/rtrs/rtrs-clt.c
>
> diff --git a/drivers/infiniband/ulp/rtrs/rtrs-clt.c b/drivers/infiniband/ulp/rtrs/rtrs-clt.c
> new file mode 100644
> index 000000000000..717d19d4d930
> --- /dev/null
> +++ b/drivers/infiniband/ulp/rtrs/rtrs-clt.c
> @@ -0,0 +1,2967 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * RDMA Transport Layer
> + *
> + * Copyright (c) 2014 - 2018 ProfitBricks GmbH. All rights reserved.
> + *
> + * Copyright (c) 2018 - 2019 1&1 IONOS Cloud GmbH. All rights reserved.
> + *
> + * Copyright (c) 2019 - 2020 1&1 IONOS SE. All rights reserved.

Please no extra lines between Copyright lines.

> + */
> +
> +#undef pr_fmt
> +#define pr_fmt(fmt) KBUILD_MODNAME " L" __stringify(__LINE__) ": " fmt

I never understood this pr_fmt() thing, do we really need it?

> +
> +#include <linux/module.h>
> +#include <linux/rculist.h>
> +#include <linux/blkdev.h> /* for BLK_MAX_SEGMENT_SIZE */
> +
> +#include "rtrs-clt.h"
> +#include "rtrs-log.h"
> +
> +#define RTRS_CONNECT_TIMEOUT_MS 30000
> +
> +MODULE_DESCRIPTION("RDMA Transport Client");
> +MODULE_LICENSE("GPL");
> +
> +static ushort nr_cons_per_session;
> +module_param(nr_cons_per_session, ushort, 0444);
> +MODULE_PARM_DESC(nr_cons_per_session,
> +		 "Number of connections per session. (default: nr_cpu_ids)");
> +
> +static int retry_cnt = 7;
> +module_param_named(retry_cnt, retry_cnt, int, 0644);
> +MODULE_PARM_DESC(retry_cnt,
> +		 "Number of times to send the message if the remote side didn't respond with Ack or Nack (default: 7, min: "
> +		 __stringify(MIN_RTR_CNT) ", max: "
> +		 __stringify(MAX_RTR_CNT) ")");
> +
> +static int __read_mostly noreg_cnt;
> +module_param_named(noreg_cnt, noreg_cnt, int, 0444);
> +MODULE_PARM_DESC(noreg_cnt,
> +		 "Max number of SG entries when MR registration does not happen (default: 0)");

We don't like modules in new code.

> +
> +static const struct rtrs_rdma_dev_pd_ops dev_pd_ops;
> +static struct rtrs_rdma_dev_pd dev_pd = {
> +	.ops = &dev_pd_ops
> +};
> +
> +static struct workqueue_struct *rtrs_wq;
> +static struct class *rtrs_clt_dev_class;
> +
> +static inline bool rtrs_clt_is_connected(const struct rtrs_clt *clt)
> +{
> +	struct rtrs_clt_sess *sess;
> +	bool connected = false;
> +
> +	rcu_read_lock();
> +	list_for_each_entry_rcu(sess, &clt->paths_list, s.entry)
> +		connected |= (READ_ONCE(sess->state) == RTRS_CLT_CONNECTED);
> +	rcu_read_unlock();
> +
> +	return connected;
> +}
> +
> +static inline struct rtrs_permit *
> +__rtrs_get_permit(struct rtrs_clt *clt, enum rtrs_clt_con_type con_type)
> +{
> +	size_t max_depth = clt->queue_depth;
> +	struct rtrs_permit *permit;
> +	int cpu, bit;
> +
> +	/* Combined with cq_vector, we pin the IO to the the cpu it comes */
> +	cpu = get_cpu();
> +	do {
> +		bit = find_first_zero_bit(clt->permits_map, max_depth);
> +		if (unlikely(bit >= max_depth)) {
> +			put_cpu();
> +			return NULL;
> +		}
> +
> +	} while (unlikely(test_and_set_bit_lock(bit, clt->permits_map)));
> +	put_cpu();
> +
> +	permit = GET_PERMIT(clt, bit);
> +	WARN_ON(permit->mem_id != bit);
> +	permit->cpu_id = cpu;
> +	permit->con_type = con_type;
> +
> +	return permit;
> +}
> +
> +static inline void __rtrs_put_permit(struct rtrs_clt *clt,
> +				      struct rtrs_permit *permit)
> +{
> +	clear_bit_unlock(permit->mem_id, clt->permits_map);
> +}
> +
> +struct rtrs_permit *rtrs_clt_get_permit(struct rtrs_clt *clt,
> +					  enum rtrs_clt_con_type con_type,
> +					  int can_wait)
> +{
> +	struct rtrs_permit *permit;
> +	DEFINE_WAIT(wait);
> +
> +	permit = __rtrs_get_permit(clt, con_type);
> +	if (likely(permit) || !can_wait)
> +		return permit;
> +
> +	do {
> +		prepare_to_wait(&clt->permits_wait, &wait,
> +				TASK_UNINTERRUPTIBLE);
> +		permit = __rtrs_get_permit(clt, con_type);
> +		if (likely(permit))
> +			break;
> +
> +		io_schedule();
> +	} while (1);
> +
> +	finish_wait(&clt->permits_wait, &wait);
> +
> +	return permit;
> +}
> +EXPORT_SYMBOL(rtrs_clt_get_permit);
> +
> +void rtrs_clt_put_permit(struct rtrs_clt *clt, struct rtrs_permit *permit)
> +{
> +	if (WARN_ON(!test_bit(permit->mem_id, clt->permits_map)))
> +		return;
> +
> +	__rtrs_put_permit(clt, permit);
> +
> +	/*
> +	 * Putting a permit is a barrier, so we will observe
> +	 * new entry in the wait list, no worries.
> +	 */
> +	if (waitqueue_active(&clt->permits_wait))

Where do you put permit? Does it include barrier?

> +		wake_up(&clt->permits_wait);
> +}
> +EXPORT_SYMBOL(rtrs_clt_put_permit);
> +
> +struct rtrs_permit *rtrs_permit_from_pdu(void *pdu)
> +{
> +	return pdu - sizeof(struct rtrs_permit);

C standard doesn't allow pointer arithmetic on void*.

> +}
> +EXPORT_SYMBOL(rtrs_permit_from_pdu);
> +
> +void *rtrs_permit_to_pdu(struct rtrs_permit *permit)
> +{
> +	return permit + 1;
> +}
> +EXPORT_SYMBOL(rtrs_permit_to_pdu);
> +
> +/**
> + * rtrs_permit_to_clt_con() - returns RDMA connection pointer by the permit
> + * @sess: client session pointer
> + * @permit: permit for the allocation of the RDMA buffer
> + * Note:
> + *     IO connection starts from 1.
> + *     0 connection is for user messages.
> + */
> +static
> +struct rtrs_clt_con *rtrs_permit_to_clt_con(struct rtrs_clt_sess *sess,
> +					    struct rtrs_permit *permit)
> +{
> +	int id = 0;
> +
> +	if (likely(permit->con_type == RTRS_IO_CON))
> +		id = (permit->cpu_id % (sess->s.con_num - 1)) + 1;
> +
> +	return to_clt_con(sess->s.con[id]);
> +}
> +
> +static bool __rtrs_clt_change_state(struct rtrs_clt_sess *sess,
> +				     enum rtrs_clt_state new_state)
> +{
> +	enum rtrs_clt_state old_state;
> +	bool changed = false;
> +
> +	lockdep_assert_held(&sess->state_wq.lock);
> +
> +	old_state = sess->state;
> +	switch (new_state) {
> +	case RTRS_CLT_CONNECTING:
> +		switch (old_state) {

Double switch is better to be avoided.

> +		case RTRS_CLT_RECONNECTING:
> +			changed = true;
> +			/* FALLTHRU */
> +		default:
> +			break;
> +		}
> +		break;


....

Thanks