[mirror_ubuntu-bionic-kernel.git] / drivers / staging / lustre / lustre / ptlrpc / service.c

// SPDX-License-Identifier: GPL-2.0
/*
 * GPL HEADER START
 *
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 only,
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License version 2 for more details (a copy is included
 * in the LICENSE file that accompanied this code).
 *
 * You should have received a copy of the GNU General Public License
 * version 2 along with this program; If not, see
 * http://www.gnu.org/licenses/gpl-2.0.html
 *
 * GPL HEADER END
 */
/*
 * Copyright (c) 2002, 2010, Oracle and/or its affiliates. All rights reserved.
 * Use is subject to license terms.
 *
 * Copyright (c) 2010, 2015, Intel Corporation.
 */
/*
 * This file is part of Lustre, http://www.lustre.org/
 * Lustre is a trademark of Sun Microsystems, Inc.
 */

#define DEBUG_SUBSYSTEM S_RPC

#include <obd_support.h>
#include <obd_class.h>
#include <lustre_net.h>
#include <lu_object.h>
#include <uapi/linux/lnet/lnet-types.h>
#include "ptlrpc_internal.h"

/* The following are visible and mutable through /sys/module/ptlrpc */
int test_req_buffer_pressure;
module_param(test_req_buffer_pressure, int, 0444);
MODULE_PARM_DESC(test_req_buffer_pressure, "set non-zero to put pressure on request buffer pools");
module_param(at_min, int, 0644);
MODULE_PARM_DESC(at_min, "Adaptive timeout minimum (sec)");
module_param(at_max, int, 0644);
MODULE_PARM_DESC(at_max, "Adaptive timeout maximum (sec)");
module_param(at_history, int, 0644);
MODULE_PARM_DESC(at_history,
                 "Adaptive timeouts remember the slowest event that took place within this period (sec)");
module_param(at_early_margin, int, 0644);
MODULE_PARM_DESC(at_early_margin, "How soon before an RPC deadline to send an early reply");
module_param(at_extra, int, 0644);
MODULE_PARM_DESC(at_extra, "How much extra time to give with each early reply");

/* forward ref */
static int ptlrpc_server_post_idle_rqbds(struct ptlrpc_service_part *svcpt);
static void ptlrpc_server_hpreq_fini(struct ptlrpc_request *req);
static void ptlrpc_at_remove_timed(struct ptlrpc_request *req);

/** Holds a list of all PTLRPC services */
LIST_HEAD(ptlrpc_all_services);
/** Used to protect the \e ptlrpc_all_services list */
struct mutex ptlrpc_all_services_mutex;

static struct ptlrpc_request_buffer_desc *
ptlrpc_alloc_rqbd(struct ptlrpc_service_part *svcpt)
{
        struct ptlrpc_service *svc = svcpt->scp_service;
        struct ptlrpc_request_buffer_desc *rqbd;

        rqbd = kzalloc_node(sizeof(*rqbd), GFP_NOFS,
                            cfs_cpt_spread_node(svc->srv_cptable,
                                                svcpt->scp_cpt));
        if (!rqbd)
                return NULL;

        rqbd->rqbd_svcpt = svcpt;
        rqbd->rqbd_refcount = 0;
        rqbd->rqbd_cbid.cbid_fn = request_in_callback;
        rqbd->rqbd_cbid.cbid_arg = rqbd;
        INIT_LIST_HEAD(&rqbd->rqbd_reqs);
        rqbd->rqbd_buffer = libcfs_kvzalloc_cpt(svc->srv_cptable,
                                                svcpt->scp_cpt,
                                                svc->srv_buf_size,
                                                GFP_KERNEL);
        if (!rqbd->rqbd_buffer) {
                kfree(rqbd);
                return NULL;
        }

        spin_lock(&svcpt->scp_lock);
        list_add(&rqbd->rqbd_list, &svcpt->scp_rqbd_idle);
        svcpt->scp_nrqbds_total++;
        spin_unlock(&svcpt->scp_lock);

        return rqbd;
}

static void
ptlrpc_free_rqbd(struct ptlrpc_request_buffer_desc *rqbd)
{
        struct ptlrpc_service_part *svcpt = rqbd->rqbd_svcpt;

        LASSERT(rqbd->rqbd_refcount == 0);
        LASSERT(list_empty(&rqbd->rqbd_reqs));

        spin_lock(&svcpt->scp_lock);
        list_del(&rqbd->rqbd_list);
        svcpt->scp_nrqbds_total--;
        spin_unlock(&svcpt->scp_lock);

        kvfree(rqbd->rqbd_buffer);
        kfree(rqbd);
}

static int
ptlrpc_grow_req_bufs(struct ptlrpc_service_part *svcpt, int post)
{
        struct ptlrpc_service *svc = svcpt->scp_service;
        struct ptlrpc_request_buffer_desc *rqbd;
        int rc = 0;
        int i;

        if (svcpt->scp_rqbd_allocating)
                goto try_post;

        spin_lock(&svcpt->scp_lock);
        /* check again with lock */
        if (svcpt->scp_rqbd_allocating) {
                /* NB: we might allow more than one thread in the future */
                LASSERT(svcpt->scp_rqbd_allocating == 1);
                spin_unlock(&svcpt->scp_lock);
                goto try_post;
        }

        svcpt->scp_rqbd_allocating++;
        spin_unlock(&svcpt->scp_lock);

        for (i = 0; i < svc->srv_nbuf_per_group; i++) {
                /* NB: another thread might have recycled enough rqbds, we
                 * need to make sure it wouldn't over-allocate, see LU-1212.
                 */
                if (svcpt->scp_nrqbds_posted >= svc->srv_nbuf_per_group)
                        break;

                rqbd = ptlrpc_alloc_rqbd(svcpt);

                if (!rqbd) {
                        CERROR("%s: Can't allocate request buffer\n",
                               svc->srv_name);
                        rc = -ENOMEM;
                        break;
                }
        }

        spin_lock(&svcpt->scp_lock);

        LASSERT(svcpt->scp_rqbd_allocating == 1);
        svcpt->scp_rqbd_allocating--;

        spin_unlock(&svcpt->scp_lock);

        CDEBUG(D_RPCTRACE,
               "%s: allocate %d new %d-byte reqbufs (%d/%d left), rc = %d\n",
               svc->srv_name, i, svc->srv_buf_size, svcpt->scp_nrqbds_posted,
               svcpt->scp_nrqbds_total, rc);

 try_post:
        if (post && rc == 0)
                rc = ptlrpc_server_post_idle_rqbds(svcpt);

        return rc;
}

struct ptlrpc_hr_partition;

struct ptlrpc_hr_thread {
        int                             hrt_id;         /* thread ID */
        spinlock_t                      hrt_lock;
        wait_queue_head_t                       hrt_waitq;
        struct list_head                        hrt_queue;      /* RS queue */
        struct ptlrpc_hr_partition      *hrt_partition;
};

struct ptlrpc_hr_partition {
        /* # of started threads */
        atomic_t                        hrp_nstarted;
        /* # of stopped threads */
        atomic_t                        hrp_nstopped;
        /* cpu partition id */
        int                             hrp_cpt;
        /* round-robin rotor for choosing thread */
        int                             hrp_rotor;
        /* total number of threads on this partition */
        int                             hrp_nthrs;
        /* threads table */
        struct ptlrpc_hr_thread         *hrp_thrs;
};

#define HRT_RUNNING 0
#define HRT_STOPPING 1

struct ptlrpc_hr_service {
        /* CPU partition table, it's just cfs_cpt_table for now */
        struct cfs_cpt_table            *hr_cpt_table;
        /** controller sleep waitq */
        wait_queue_head_t                       hr_waitq;
        unsigned int                    hr_stopping;
        /** roundrobin rotor for non-affinity service */
        unsigned int                    hr_rotor;
        /* partition data */
        struct ptlrpc_hr_partition      **hr_partitions;
};

/** reply handling service. */
static struct ptlrpc_hr_service         ptlrpc_hr;

/**
 * Choose an hr thread to dispatch requests to.
 */
static struct ptlrpc_hr_thread *
ptlrpc_hr_select(struct ptlrpc_service_part *svcpt)
{
        struct ptlrpc_hr_partition *hrp;
        unsigned int rotor;

        if (svcpt->scp_cpt >= 0 &&
            svcpt->scp_service->srv_cptable == ptlrpc_hr.hr_cpt_table) {
                /* directly match partition */
                hrp = ptlrpc_hr.hr_partitions[svcpt->scp_cpt];

        } else {
                rotor = ptlrpc_hr.hr_rotor++;
                rotor %= cfs_cpt_number(ptlrpc_hr.hr_cpt_table);

                hrp = ptlrpc_hr.hr_partitions[rotor];
        }

        rotor = hrp->hrp_rotor++;
        return &hrp->hrp_thrs[rotor % hrp->hrp_nthrs];
}

/**
 * Put reply state into a queue for processing because we received
 * ACK from the client
 */
void ptlrpc_dispatch_difficult_reply(struct ptlrpc_reply_state *rs)
{
        struct ptlrpc_hr_thread *hrt;

        LASSERT(list_empty(&rs->rs_list));

        hrt = ptlrpc_hr_select(rs->rs_svcpt);

        spin_lock(&hrt->hrt_lock);
        list_add_tail(&rs->rs_list, &hrt->hrt_queue);
        spin_unlock(&hrt->hrt_lock);

        wake_up(&hrt->hrt_waitq);
}

void
ptlrpc_schedule_difficult_reply(struct ptlrpc_reply_state *rs)
{
        assert_spin_locked(&rs->rs_svcpt->scp_rep_lock);
        assert_spin_locked(&rs->rs_lock);
        LASSERT(rs->rs_difficult);
        rs->rs_scheduled_ever = 1;  /* flag any notification attempt */

        if (rs->rs_scheduled) {     /* being set up or already notified */
                return;
        }

        rs->rs_scheduled = 1;
        list_del_init(&rs->rs_list);
        ptlrpc_dispatch_difficult_reply(rs);
}
EXPORT_SYMBOL(ptlrpc_schedule_difficult_reply);

static int
ptlrpc_server_post_idle_rqbds(struct ptlrpc_service_part *svcpt)
{
        struct ptlrpc_request_buffer_desc *rqbd;
        int rc;
        int posted = 0;

        for (;;) {
                spin_lock(&svcpt->scp_lock);

                if (list_empty(&svcpt->scp_rqbd_idle)) {
                        spin_unlock(&svcpt->scp_lock);
                        return posted;
                }

                rqbd = list_entry(svcpt->scp_rqbd_idle.next,
                                  struct ptlrpc_request_buffer_desc,
                                  rqbd_list);
                list_del(&rqbd->rqbd_list);

                /* assume we will post successfully */
                svcpt->scp_nrqbds_posted++;
                list_add(&rqbd->rqbd_list, &svcpt->scp_rqbd_posted);

                spin_unlock(&svcpt->scp_lock);

                rc = ptlrpc_register_rqbd(rqbd);
                if (rc != 0)
                        break;

                posted = 1;
        }

        spin_lock(&svcpt->scp_lock);

        svcpt->scp_nrqbds_posted--;
        list_del(&rqbd->rqbd_list);
        list_add_tail(&rqbd->rqbd_list, &svcpt->scp_rqbd_idle);

        /* Don't complain if no request buffers are posted right now; LNET
         * won't drop requests because we set the portal lazy!
         */

        spin_unlock(&svcpt->scp_lock);

        return -1;
}

static void ptlrpc_at_timer(unsigned long castmeharder)
{
        struct ptlrpc_service_part *svcpt;

        svcpt = (struct ptlrpc_service_part *)castmeharder;

        svcpt->scp_at_check = 1;
        svcpt->scp_at_checktime = cfs_time_current();
        wake_up(&svcpt->scp_waitq);
}

static void
ptlrpc_server_nthreads_check(struct ptlrpc_service *svc,
                             struct ptlrpc_service_conf *conf)
{
        struct ptlrpc_service_thr_conf *tc = &conf->psc_thr;
        unsigned int init;
        unsigned int total;
        unsigned int nthrs;
        int weight;

        /*
         * Common code for estimating & validating threads number.
         * CPT affinity service could have percpt thread-pool instead
         * of a global thread-pool, which means user might not always
         * get the threads number they give it in conf::tc_nthrs_user
         * even they did set. It's because we need to validate threads
         * number for each CPT to guarantee each pool will have enough
         * threads to keep the service healthy.
         */
        init = PTLRPC_NTHRS_INIT + (svc->srv_ops.so_hpreq_handler != NULL);
        init = max_t(int, init, tc->tc_nthrs_init);

        /* NB: please see comments in lustre_lnet.h for definition
         * details of these members
         */
        LASSERT(tc->tc_nthrs_max != 0);

        if (tc->tc_nthrs_user != 0) {
                /* In case there is a reason to test a service with many
                 * threads, we give a less strict check here, it can
                 * be up to 8 * nthrs_max
                 */
                total = min(tc->tc_nthrs_max * 8, tc->tc_nthrs_user);
                nthrs = total / svc->srv_ncpts;
                init = max(init, nthrs);
                goto out;
        }

        total = tc->tc_nthrs_max;
        if (tc->tc_nthrs_base == 0) {
                /* don't care about base threads number per partition,
                 * this is most for non-affinity service
                 */
                nthrs = total / svc->srv_ncpts;
                goto out;
        }

        nthrs = tc->tc_nthrs_base;
        if (svc->srv_ncpts == 1) {
                int i;

                /* NB: Increase the base number if it's single partition
                 * and total number of cores/HTs is larger or equal to 4.
                 * result will always < 2 * nthrs_base
                 */
                weight = cfs_cpt_weight(svc->srv_cptable, CFS_CPT_ANY);
                for (i = 1; (weight >> (i + 1)) != 0 && /* >= 4 cores/HTs */
                            (tc->tc_nthrs_base >> i) != 0; i++)
                        nthrs += tc->tc_nthrs_base >> i;
        }

        if (tc->tc_thr_factor != 0) {
                int factor = tc->tc_thr_factor;
                const int fade = 4;

                /*
                 * User wants to increase number of threads with for
                 * each CPU core/HT, most likely the factor is larger then
                 * one thread/core because service threads are supposed to
                 * be blocked by lock or wait for IO.
                 */
                /*
                 * Amdahl's law says that adding processors wouldn't give
                 * a linear increasing of parallelism, so it's nonsense to
                 * have too many threads no matter how many cores/HTs
                 * there are.
                 */
                /* weight is # of HTs */
                if (cpumask_weight(topology_sibling_cpumask(0)) > 1) {
                        /* depress thread factor for hyper-thread */
                        factor = factor - (factor >> 1) + (factor >> 3);
                }

                weight = cfs_cpt_weight(svc->srv_cptable, 0);
                LASSERT(weight > 0);

                for (; factor > 0 && weight > 0; factor--, weight -= fade)
                        nthrs += min(weight, fade) * factor;
        }

        if (nthrs * svc->srv_ncpts > tc->tc_nthrs_max) {
                nthrs = max(tc->tc_nthrs_base,
                            tc->tc_nthrs_max / svc->srv_ncpts);
        }
 out:
        nthrs = max(nthrs, tc->tc_nthrs_init);
        svc->srv_nthrs_cpt_limit = nthrs;
        svc->srv_nthrs_cpt_init = init;

        if (nthrs * svc->srv_ncpts > tc->tc_nthrs_max) {
                CDEBUG(D_OTHER, "%s: This service may have more threads (%d) than the given soft limit (%d)\n",
                       svc->srv_name, nthrs * svc->srv_ncpts,
                       tc->tc_nthrs_max);
        }
}

/**
 * Initialize percpt data for a service
 */
static int
ptlrpc_service_part_init(struct ptlrpc_service *svc,
                         struct ptlrpc_service_part *svcpt, int cpt)
{
        struct ptlrpc_at_array  *array;
        int size;
        int index;
        int rc;

        svcpt->scp_cpt = cpt;
        INIT_LIST_HEAD(&svcpt->scp_threads);

        /* rqbd and incoming request queue */
        spin_lock_init(&svcpt->scp_lock);
        INIT_LIST_HEAD(&svcpt->scp_rqbd_idle);
        INIT_LIST_HEAD(&svcpt->scp_rqbd_posted);
        INIT_LIST_HEAD(&svcpt->scp_req_incoming);
        init_waitqueue_head(&svcpt->scp_waitq);
        /* history request & rqbd list */
        INIT_LIST_HEAD(&svcpt->scp_hist_reqs);
        INIT_LIST_HEAD(&svcpt->scp_hist_rqbds);

        /* active requests and hp requests */
        spin_lock_init(&svcpt->scp_req_lock);

        /* reply states */
        spin_lock_init(&svcpt->scp_rep_lock);
        INIT_LIST_HEAD(&svcpt->scp_rep_active);
        INIT_LIST_HEAD(&svcpt->scp_rep_idle);
        init_waitqueue_head(&svcpt->scp_rep_waitq);
        atomic_set(&svcpt->scp_nreps_difficult, 0);

        /* adaptive timeout */
        spin_lock_init(&svcpt->scp_at_lock);
        array = &svcpt->scp_at_array;

        size = at_est2timeout(at_max);
        array->paa_size = size;
        array->paa_count = 0;
        array->paa_deadline = -1;

        /* allocate memory for scp_at_array (ptlrpc_at_array) */
        array->paa_reqs_array =
                kzalloc_node(sizeof(struct list_head) * size, GFP_NOFS,
                             cfs_cpt_spread_node(svc->srv_cptable, cpt));
        if (!array->paa_reqs_array)
                return -ENOMEM;

        for (index = 0; index < size; index++)
                INIT_LIST_HEAD(&array->paa_reqs_array[index]);

        array->paa_reqs_count =
                kzalloc_node(sizeof(__u32) * size, GFP_NOFS,
                             cfs_cpt_spread_node(svc->srv_cptable, cpt));
        if (!array->paa_reqs_count)
                goto free_reqs_array;

        setup_timer(&svcpt->scp_at_timer, ptlrpc_at_timer,
                    (unsigned long)svcpt);

        /* At SOW, service time should be quick; 10s seems generous. If client
         * timeout is less than this, we'll be sending an early reply.
         */
        at_init(&svcpt->scp_at_estimate, 10, 0);

        /* assign this before call ptlrpc_grow_req_bufs */
        svcpt->scp_service = svc;
        /* Now allocate the request buffers, but don't post them now */
        rc = ptlrpc_grow_req_bufs(svcpt, 0);
        /* We shouldn't be under memory pressure at startup, so
         * fail if we can't allocate all our buffers at this time.
         */
        if (rc != 0)
                goto free_reqs_count;

        return 0;

free_reqs_count:
        kfree(array->paa_reqs_count);
        array->paa_reqs_count = NULL;
free_reqs_array:
        kfree(array->paa_reqs_array);
        array->paa_reqs_array = NULL;

        return -ENOMEM;
}

/**
 * Initialize service on a given portal.
 * This includes starting serving threads , allocating and posting rqbds and
 * so on.
 */
struct ptlrpc_service *
ptlrpc_register_service(struct ptlrpc_service_conf *conf,
                        struct kset *parent,
                        struct dentry *debugfs_entry)
{
        struct ptlrpc_service_cpt_conf *cconf = &conf->psc_cpt;
        struct ptlrpc_service *service;
        struct ptlrpc_service_part *svcpt;
        struct cfs_cpt_table *cptable;
        __u32 *cpts = NULL;
        int ncpts;
        int cpt;
        int rc;
        int i;

        LASSERT(conf->psc_buf.bc_nbufs > 0);
        LASSERT(conf->psc_buf.bc_buf_size >=
                conf->psc_buf.bc_req_max_size + SPTLRPC_MAX_PAYLOAD);
        LASSERT(conf->psc_thr.tc_ctx_tags != 0);

        cptable = cconf->cc_cptable;
        if (!cptable)
                cptable = cfs_cpt_table;

        if (!conf->psc_thr.tc_cpu_affinity) {
                ncpts = 1;
        } else {
                ncpts = cfs_cpt_number(cptable);
                if (cconf->cc_pattern) {
                        struct cfs_expr_list *el;

                        rc = cfs_expr_list_parse(cconf->cc_pattern,
                                                 strlen(cconf->cc_pattern),
                                                 0, ncpts - 1, &el);
                        if (rc != 0) {
                                CERROR("%s: invalid CPT pattern string: %s",
                                       conf->psc_name, cconf->cc_pattern);
                                return ERR_PTR(-EINVAL);
                        }

                        rc = cfs_expr_list_values(el, ncpts, &cpts);
                        cfs_expr_list_free(el);
                        if (rc <= 0) {
                                CERROR("%s: failed to parse CPT array %s: %d\n",
                                       conf->psc_name, cconf->cc_pattern, rc);
                                kfree(cpts);
                                return ERR_PTR(rc < 0 ? rc : -EINVAL);
                        }
                        ncpts = rc;
                }
        }

        service = kzalloc(offsetof(struct ptlrpc_service, srv_parts[ncpts]),
                          GFP_NOFS);
        if (!service) {
                kfree(cpts);
                return ERR_PTR(-ENOMEM);
        }

        service->srv_cptable = cptable;
        service->srv_cpts = cpts;
        service->srv_ncpts = ncpts;

        service->srv_cpt_bits = 0; /* it's zero already, easy to read... */
        while ((1 << service->srv_cpt_bits) < cfs_cpt_number(cptable))
                service->srv_cpt_bits++;

        /* public members */
        spin_lock_init(&service->srv_lock);
        service->srv_name = conf->psc_name;
        service->srv_watchdog_factor = conf->psc_watchdog_factor;
        INIT_LIST_HEAD(&service->srv_list); /* for safety of cleanup */

        /* buffer configuration */
        service->srv_nbuf_per_group = test_req_buffer_pressure ?
                                          1 : conf->psc_buf.bc_nbufs;
        service->srv_max_req_size = conf->psc_buf.bc_req_max_size +
                                          SPTLRPC_MAX_PAYLOAD;
        service->srv_buf_size = conf->psc_buf.bc_buf_size;
        service->srv_rep_portal = conf->psc_buf.bc_rep_portal;
        service->srv_req_portal = conf->psc_buf.bc_req_portal;

        /* Increase max reply size to next power of two */
        service->srv_max_reply_size = 1;
        while (service->srv_max_reply_size <
               conf->psc_buf.bc_rep_max_size + SPTLRPC_MAX_PAYLOAD)
                service->srv_max_reply_size <<= 1;

        service->srv_thread_name = conf->psc_thr.tc_thr_name;
        service->srv_ctx_tags = conf->psc_thr.tc_ctx_tags;
        service->srv_hpreq_ratio = PTLRPC_SVC_HP_RATIO;
        service->srv_ops = conf->psc_ops;

        for (i = 0; i < ncpts; i++) {
                if (!conf->psc_thr.tc_cpu_affinity)
                        cpt = CFS_CPT_ANY;
                else
                        cpt = cpts ? cpts[i] : i;

                svcpt = kzalloc_node(sizeof(*svcpt), GFP_NOFS,
                                     cfs_cpt_spread_node(cptable, cpt));
                if (!svcpt) {
                        rc = -ENOMEM;
                        goto failed;
                }

                service->srv_parts[i] = svcpt;
                rc = ptlrpc_service_part_init(service, svcpt, cpt);
                if (rc != 0)
                        goto failed;
        }

        ptlrpc_server_nthreads_check(service, conf);

        rc = LNetSetLazyPortal(service->srv_req_portal);
        LASSERT(rc == 0);

        mutex_lock(&ptlrpc_all_services_mutex);
        list_add(&service->srv_list, &ptlrpc_all_services);
        mutex_unlock(&ptlrpc_all_services_mutex);

        if (parent) {
                rc = ptlrpc_sysfs_register_service(parent, service);
                if (rc)
                        goto failed;
        }

        if (!IS_ERR_OR_NULL(debugfs_entry))
                ptlrpc_ldebugfs_register_service(debugfs_entry, service);

        rc = ptlrpc_service_nrs_setup(service);
        if (rc != 0)
                goto failed;

        CDEBUG(D_NET, "%s: Started, listening on portal %d\n",
               service->srv_name, service->srv_req_portal);

        rc = ptlrpc_start_threads(service);
        if (rc != 0) {
                CERROR("Failed to start threads for service %s: %d\n",
                       service->srv_name, rc);
                goto failed;
        }

        return service;
failed:
        ptlrpc_unregister_service(service);
        return ERR_PTR(rc);
}
EXPORT_SYMBOL(ptlrpc_register_service);

/**
 * to actually free the request, must be called without holding svc_lock.
 * note it's caller's responsibility to unlink req->rq_list.
 */
static void ptlrpc_server_free_request(struct ptlrpc_request *req)
{
        LASSERT(atomic_read(&req->rq_refcount) == 0);
        LASSERT(list_empty(&req->rq_timed_list));

         /* DEBUG_REQ() assumes the reply state of a request with a valid
          * ref will not be destroyed until that reference is dropped.
          */
        ptlrpc_req_drop_rs(req);

        sptlrpc_svc_ctx_decref(req);

        if (req != &req->rq_rqbd->rqbd_req) {
                /* NB request buffers use an embedded
                 * req if the incoming req unlinked the
                 * MD; this isn't one of them!
                 */
                ptlrpc_request_cache_free(req);
        }
}

/**
 * drop a reference count of the request. if it reaches 0, we either
 * put it into history list, or free it immediately.
 */
static void ptlrpc_server_drop_request(struct ptlrpc_request *req)
{
        struct ptlrpc_request_buffer_desc *rqbd = req->rq_rqbd;
        struct ptlrpc_service_part *svcpt = rqbd->rqbd_svcpt;
        struct ptlrpc_service *svc = svcpt->scp_service;
        int refcount;
        struct list_head *tmp;
        struct list_head *nxt;

        if (!atomic_dec_and_test(&req->rq_refcount))
                return;

        if (req->rq_at_linked) {
                spin_lock(&svcpt->scp_at_lock);
                /* recheck with lock, in case it's unlinked by
                 * ptlrpc_at_check_timed()
                 */
                if (likely(req->rq_at_linked))
                        ptlrpc_at_remove_timed(req);
                spin_unlock(&svcpt->scp_at_lock);
        }

        LASSERT(list_empty(&req->rq_timed_list));

        /* finalize request */
        if (req->rq_export) {
                class_export_put(req->rq_export);
                req->rq_export = NULL;
        }

        spin_lock(&svcpt->scp_lock);

        list_add(&req->rq_list, &rqbd->rqbd_reqs);

        refcount = --(rqbd->rqbd_refcount);
        if (refcount == 0) {
                /* request buffer is now idle: add to history */
                list_del(&rqbd->rqbd_list);

                list_add_tail(&rqbd->rqbd_list, &svcpt->scp_hist_rqbds);
                svcpt->scp_hist_nrqbds++;

                /* cull some history?
                 * I expect only about 1 or 2 rqbds need to be recycled here
                 */
                while (svcpt->scp_hist_nrqbds > svc->srv_hist_nrqbds_cpt_max) {
                        rqbd = list_entry(svcpt->scp_hist_rqbds.next,
                                          struct ptlrpc_request_buffer_desc,
                                          rqbd_list);

                        list_del(&rqbd->rqbd_list);
                        svcpt->scp_hist_nrqbds--;

                        /* remove rqbd's reqs from svc's req history while
                         * I've got the service lock
                         */
                        list_for_each(tmp, &rqbd->rqbd_reqs) {
                                req = list_entry(tmp, struct ptlrpc_request,
                                                 rq_list);
                                /* Track the highest culled req seq */
                                if (req->rq_history_seq >
                                    svcpt->scp_hist_seq_culled) {
                                        svcpt->scp_hist_seq_culled =
                                                req->rq_history_seq;
                                }
                                list_del(&req->rq_history_list);
                        }

                        spin_unlock(&svcpt->scp_lock);

                        list_for_each_safe(tmp, nxt, &rqbd->rqbd_reqs) {
                                req = list_entry(rqbd->rqbd_reqs.next,
                                                 struct ptlrpc_request,
                                                 rq_list);
                                list_del(&req->rq_list);
                                ptlrpc_server_free_request(req);
                        }

                        spin_lock(&svcpt->scp_lock);
                        /*
                         * now all reqs including the embedded req has been
                         * disposed, schedule request buffer for re-use.
                         */
                        LASSERT(atomic_read(&rqbd->rqbd_req.rq_refcount) ==
                                0);
                        list_add_tail(&rqbd->rqbd_list, &svcpt->scp_rqbd_idle);
                }

                spin_unlock(&svcpt->scp_lock);
        } else if (req->rq_reply_state && req->rq_reply_state->rs_prealloc) {
                /* If we are low on memory, we are not interested in history */
                list_del(&req->rq_list);
                list_del_init(&req->rq_history_list);

                /* Track the highest culled req seq */
                if (req->rq_history_seq > svcpt->scp_hist_seq_culled)
                        svcpt->scp_hist_seq_culled = req->rq_history_seq;

                spin_unlock(&svcpt->scp_lock);

                ptlrpc_server_free_request(req);
        } else {
                spin_unlock(&svcpt->scp_lock);
        }
}

/**
 * to finish a request: stop sending more early replies, and release
 * the request.
 */
static void ptlrpc_server_finish_request(struct ptlrpc_service_part *svcpt,
                                         struct ptlrpc_request *req)
{
        ptlrpc_server_hpreq_fini(req);

        if (req->rq_session.lc_thread) {
                lu_context_exit(&req->rq_session);
                lu_context_fini(&req->rq_session);
        }

        ptlrpc_server_drop_request(req);
}

/**
 * to finish a active request: stop sending more early replies, and release
 * the request. should be called after we finished handling the request.
 */
static void ptlrpc_server_finish_active_request(
                                        struct ptlrpc_service_part *svcpt,
                                        struct ptlrpc_request *req)
{
        spin_lock(&svcpt->scp_req_lock);
        ptlrpc_nrs_req_stop_nolock(req);
        svcpt->scp_nreqs_active--;
        if (req->rq_hp)
                svcpt->scp_nhreqs_active--;
        spin_unlock(&svcpt->scp_req_lock);

        ptlrpc_nrs_req_finalize(req);

        if (req->rq_export)
                class_export_rpc_dec(req->rq_export);

        ptlrpc_server_finish_request(svcpt, req);
}

/**
 * Sanity check request \a req.
 * Return 0 if all is ok, error code otherwise.
 */
static int ptlrpc_check_req(struct ptlrpc_request *req)
{
        struct obd_device *obd = req->rq_export->exp_obd;
        int rc = 0;

        if (unlikely(lustre_msg_get_conn_cnt(req->rq_reqmsg) <
                     req->rq_export->exp_conn_cnt)) {
                DEBUG_REQ(D_RPCTRACE, req,
                          "DROPPING req from old connection %d < %d",
                          lustre_msg_get_conn_cnt(req->rq_reqmsg),
                          req->rq_export->exp_conn_cnt);
                return -EEXIST;
        }
        if (unlikely(!obd || obd->obd_fail)) {
                /*
                 * Failing over, don't handle any more reqs, send
                 * error response instead.
                 */
                CDEBUG(D_RPCTRACE, "Dropping req %p for failed obd %s\n",
                       req, obd ? obd->obd_name : "unknown");
                rc = -ENODEV;
        } else if (lustre_msg_get_flags(req->rq_reqmsg) &
                   (MSG_REPLAY | MSG_REQ_REPLAY_DONE)) {
                DEBUG_REQ(D_ERROR, req, "Invalid replay without recovery");
                class_fail_export(req->rq_export);
                rc = -ENODEV;
        } else if (lustre_msg_get_transno(req->rq_reqmsg) != 0) {
                DEBUG_REQ(D_ERROR, req,
                          "Invalid req with transno %llu without recovery",
                          lustre_msg_get_transno(req->rq_reqmsg));
                class_fail_export(req->rq_export);
                rc = -ENODEV;
        }

        if (unlikely(rc < 0)) {
                req->rq_status = rc;
                ptlrpc_error(req);
        }
        return rc;
}

static void ptlrpc_at_set_timer(struct ptlrpc_service_part *svcpt)
{
        struct ptlrpc_at_array *array = &svcpt->scp_at_array;
        __s32 next;

        if (array->paa_count == 0) {
                del_timer(&svcpt->scp_at_timer);
                return;
        }

        /* Set timer for closest deadline */
        next = (__s32)(array->paa_deadline - ktime_get_real_seconds() -
                       at_early_margin);
        if (next <= 0) {
                ptlrpc_at_timer((unsigned long)svcpt);
        } else {
                mod_timer(&svcpt->scp_at_timer, cfs_time_shift(next));
                CDEBUG(D_INFO, "armed %s at %+ds\n",
                       svcpt->scp_service->srv_name, next);
        }
}

/* Add rpc to early reply check list */
static int ptlrpc_at_add_timed(struct ptlrpc_request *req)
{
        struct ptlrpc_service_part *svcpt = req->rq_rqbd->rqbd_svcpt;
        struct ptlrpc_at_array *array = &svcpt->scp_at_array;
        struct ptlrpc_request *rq = NULL;
        __u32 index;

        if (AT_OFF)
                return 0;

        if (req->rq_no_reply)
                return 0;

        if ((lustre_msghdr_get_flags(req->rq_reqmsg) & MSGHDR_AT_SUPPORT) == 0)
                return -ENOSYS;

        spin_lock(&svcpt->scp_at_lock);
        LASSERT(list_empty(&req->rq_timed_list));

        div_u64_rem(req->rq_deadline, array->paa_size, &index);
        if (array->paa_reqs_count[index] > 0) {
                /* latest rpcs will have the latest deadlines in the list,
                 * so search backward.
                 */
                list_for_each_entry_reverse(rq, &array->paa_reqs_array[index],
                                            rq_timed_list) {
                        if (req->rq_deadline >= rq->rq_deadline) {
                                list_add(&req->rq_timed_list,
                                         &rq->rq_timed_list);
                                break;
                        }
                }
        }

        /* Add the request at the head of the list */
        if (list_empty(&req->rq_timed_list))
                list_add(&req->rq_timed_list, &array->paa_reqs_array[index]);

        spin_lock(&req->rq_lock);
        req->rq_at_linked = 1;
        spin_unlock(&req->rq_lock);
        req->rq_at_index = index;
        array->paa_reqs_count[index]++;
        array->paa_count++;
        if (array->paa_count == 1 || array->paa_deadline > req->rq_deadline) {
                array->paa_deadline = req->rq_deadline;
                ptlrpc_at_set_timer(svcpt);
        }
        spin_unlock(&svcpt->scp_at_lock);

        return 0;
}

static void
ptlrpc_at_remove_timed(struct ptlrpc_request *req)
{
        struct ptlrpc_at_array *array;

        array = &req->rq_rqbd->rqbd_svcpt->scp_at_array;

        /* NB: must call with hold svcpt::scp_at_lock */
        LASSERT(!list_empty(&req->rq_timed_list));
        list_del_init(&req->rq_timed_list);

        spin_lock(&req->rq_lock);
        req->rq_at_linked = 0;
        spin_unlock(&req->rq_lock);

        array->paa_reqs_count[req->rq_at_index]--;
        array->paa_count--;
}

/*
 * Attempt to extend the request deadline by sending an early reply to the
 * client.
 */
static int ptlrpc_at_send_early_reply(struct ptlrpc_request *req)
{
        struct ptlrpc_service_part *svcpt = req->rq_rqbd->rqbd_svcpt;
        struct ptlrpc_request *reqcopy;
        struct lustre_msg *reqmsg;
        long olddl = req->rq_deadline - ktime_get_real_seconds();
        time64_t newdl;
        int rc;

        /* deadline is when the client expects us to reply, margin is the
         * difference between clients' and servers' expectations
         */
        DEBUG_REQ(D_ADAPTTO, req,
                  "%ssending early reply (deadline %+lds, margin %+lds) for %d+%d",
                  AT_OFF ? "AT off - not " : "",
                  olddl, olddl - at_get(&svcpt->scp_at_estimate),
                  at_get(&svcpt->scp_at_estimate), at_extra);

        if (AT_OFF)
                return 0;

        if (olddl < 0) {
                DEBUG_REQ(D_WARNING, req, "Already past deadline (%+lds), not sending early reply. Consider increasing at_early_margin (%d)?",
                          olddl, at_early_margin);

                /* Return an error so we're not re-added to the timed list. */
                return -ETIMEDOUT;
        }

        if (!(lustre_msghdr_get_flags(req->rq_reqmsg) & MSGHDR_AT_SUPPORT)) {
                DEBUG_REQ(D_INFO, req, "Wanted to ask client for more time, but no AT support");
                return -ENOSYS;
        }

        /*
         * We want to extend the request deadline by at_extra seconds,
         * so we set our service estimate to reflect how much time has
         * passed since this request arrived plus an additional
         * at_extra seconds. The client will calculate the new deadline
         * based on this service estimate (plus some additional time to
         * account for network latency). See ptlrpc_at_recv_early_reply
         */
        at_measured(&svcpt->scp_at_estimate, at_extra +
                    ktime_get_real_seconds() - req->rq_arrival_time.tv_sec);
        newdl = req->rq_arrival_time.tv_sec + at_get(&svcpt->scp_at_estimate);

        /* Check to see if we've actually increased the deadline -
         * we may be past adaptive_max
         */
        if (req->rq_deadline >= newdl) {
                DEBUG_REQ(D_WARNING, req, "Couldn't add any time (%ld/%lld), not sending early reply\n",
                          olddl, newdl - ktime_get_real_seconds());
                return -ETIMEDOUT;
        }

        reqcopy = ptlrpc_request_cache_alloc(GFP_NOFS);
        if (!reqcopy)
                return -ENOMEM;
        reqmsg = libcfs_kvzalloc(req->rq_reqlen, GFP_NOFS);
        if (!reqmsg) {
                rc = -ENOMEM;
                goto out_free;
        }

        *reqcopy = *req;
        reqcopy->rq_reply_state = NULL;
        reqcopy->rq_rep_swab_mask = 0;
        reqcopy->rq_pack_bulk = 0;
        reqcopy->rq_pack_udesc = 0;
        reqcopy->rq_packed_final = 0;
        sptlrpc_svc_ctx_addref(reqcopy);
        /* We only need the reqmsg for the magic */
        reqcopy->rq_reqmsg = reqmsg;
        memcpy(reqmsg, req->rq_reqmsg, req->rq_reqlen);

        LASSERT(atomic_read(&req->rq_refcount));
        /** if it is last refcount then early reply isn't needed */
        if (atomic_read(&req->rq_refcount) == 1) {
                DEBUG_REQ(D_ADAPTTO, reqcopy, "Normal reply already sent out, abort sending early reply\n");
                rc = -EINVAL;
                goto out;
        }

        /* Connection ref */
        reqcopy->rq_export = class_conn2export(
                                     lustre_msg_get_handle(reqcopy->rq_reqmsg));
        if (!reqcopy->rq_export) {
                rc = -ENODEV;
                goto out;
        }

        /* RPC ref */
        class_export_rpc_inc(reqcopy->rq_export);
        if (reqcopy->rq_export->exp_obd &&
            reqcopy->rq_export->exp_obd->obd_fail) {
                rc = -ENODEV;
                goto out_put;
        }

        rc = lustre_pack_reply_flags(reqcopy, 1, NULL, NULL, LPRFL_EARLY_REPLY);
        if (rc)
                goto out_put;

        rc = ptlrpc_send_reply(reqcopy, PTLRPC_REPLY_EARLY);

        if (!rc) {
                /* Adjust our own deadline to what we told the client */
                req->rq_deadline = newdl;
                req->rq_early_count++; /* number sent, server side */
        } else {
                DEBUG_REQ(D_ERROR, req, "Early reply send failed %d", rc);
        }

        /* Free the (early) reply state from lustre_pack_reply.
         * (ptlrpc_send_reply takes it's own rs ref, so this is safe here)
         */
        ptlrpc_req_drop_rs(reqcopy);

out_put:
        class_export_rpc_dec(reqcopy->rq_export);
        class_export_put(reqcopy->rq_export);
out:
        sptlrpc_svc_ctx_decref(reqcopy);
        kvfree(reqmsg);
out_free:
        ptlrpc_request_cache_free(reqcopy);
        return rc;
}

/* Send early replies to everybody expiring within at_early_margin
 * asking for at_extra time
 */
static void ptlrpc_at_check_timed(struct ptlrpc_service_part *svcpt)
{
        struct ptlrpc_at_array *array = &svcpt->scp_at_array;
        struct ptlrpc_request *rq, *n;
        struct list_head work_list;
        __u32 index, count;
        time64_t deadline;
        time64_t now = ktime_get_real_seconds();
        long delay;
        int first, counter = 0;

        spin_lock(&svcpt->scp_at_lock);
        if (svcpt->scp_at_check == 0) {
                spin_unlock(&svcpt->scp_at_lock);
                return;
        }
        delay = cfs_time_sub(cfs_time_current(), svcpt->scp_at_checktime);
        svcpt->scp_at_check = 0;

        if (array->paa_count == 0) {
                spin_unlock(&svcpt->scp_at_lock);
                return;
        }

        /* The timer went off, but maybe the nearest rpc already completed. */
        first = array->paa_deadline - now;
        if (first > at_early_margin) {
                /* We've still got plenty of time.  Reset the timer. */
                ptlrpc_at_set_timer(svcpt);
                spin_unlock(&svcpt->scp_at_lock);
                return;
        }

        /* We're close to a timeout, and we don't know how much longer the
         * server will take. Send early replies to everyone expiring soon.
         */
        INIT_LIST_HEAD(&work_list);
        deadline = -1;
        div_u64_rem(array->paa_deadline, array->paa_size, &index);
        count = array->paa_count;
        while (count > 0) {
                count -= array->paa_reqs_count[index];
                list_for_each_entry_safe(rq, n, &array->paa_reqs_array[index],
                                         rq_timed_list) {
                        if (rq->rq_deadline > now + at_early_margin) {
                                /* update the earliest deadline */
                                if (deadline == -1 ||
                                    rq->rq_deadline < deadline)
                                        deadline = rq->rq_deadline;
                                break;
                        }

                        ptlrpc_at_remove_timed(rq);
                        /**
                         * ptlrpc_server_drop_request() may drop
                         * refcount to 0 already. Let's check this and
                         * don't add entry to work_list
                         */
                        if (likely(atomic_inc_not_zero(&rq->rq_refcount)))
                                list_add(&rq->rq_timed_list, &work_list);
                        counter++;
                }

                if (++index >= array->paa_size)
                        index = 0;
        }
        array->paa_deadline = deadline;
        /* we have a new earliest deadline, restart the timer */
        ptlrpc_at_set_timer(svcpt);

        spin_unlock(&svcpt->scp_at_lock);

        CDEBUG(D_ADAPTTO, "timeout in %+ds, asking for %d secs on %d early replies\n",
               first, at_extra, counter);
        if (first < 0) {
                /* We're already past request deadlines before we even get a
                 * chance to send early replies
                 */
                LCONSOLE_WARN("%s: This server is not able to keep up with request traffic (cpu-bound).\n",
                              svcpt->scp_service->srv_name);
                CWARN("earlyQ=%d reqQ=%d recA=%d, svcEst=%d, delay=%ld(jiff)\n",
                      counter, svcpt->scp_nreqs_incoming,
                      svcpt->scp_nreqs_active,
                      at_get(&svcpt->scp_at_estimate), delay);
        }

        /* we took additional refcount so entries can't be deleted from list, no
         * locking is needed
         */
        while (!list_empty(&work_list)) {
                rq = list_entry(work_list.next, struct ptlrpc_request,
                                rq_timed_list);
                list_del_init(&rq->rq_timed_list);

                if (ptlrpc_at_send_early_reply(rq) == 0)
                        ptlrpc_at_add_timed(rq);

                ptlrpc_server_drop_request(rq);
        }
}

/**
 * Put the request to the export list if the request may become
 * a high priority one.
 */
static int ptlrpc_server_hpreq_init(struct ptlrpc_service_part *svcpt,
                                    struct ptlrpc_request *req)
{
        int rc = 0;

        if (svcpt->scp_service->srv_ops.so_hpreq_handler) {
                rc = svcpt->scp_service->srv_ops.so_hpreq_handler(req);
                if (rc < 0)
                        return rc;
                LASSERT(rc == 0);
        }
        if (req->rq_export && req->rq_ops) {
                /* Perform request specific check. We should do this check
                 * before the request is added into exp_hp_rpcs list otherwise
                 * it may hit swab race at LU-1044.
                 */
                if (req->rq_ops->hpreq_check) {
                        rc = req->rq_ops->hpreq_check(req);
                        if (rc == -ESTALE) {
                                req->rq_status = rc;
                                ptlrpc_error(req);
                        }
                        /** can only return error,
                         * 0 for normal request,
                         *  or 1 for high priority request
                         */
                        LASSERT(rc <= 1);
                }

                spin_lock_bh(&req->rq_export->exp_rpc_lock);
                list_add(&req->rq_exp_list, &req->rq_export->exp_hp_rpcs);
                spin_unlock_bh(&req->rq_export->exp_rpc_lock);
        }

        ptlrpc_nrs_req_initialize(svcpt, req, rc);

        return rc;
}

/** Remove the request from the export list. */
static void ptlrpc_server_hpreq_fini(struct ptlrpc_request *req)
{
        if (req->rq_export && req->rq_ops) {
                /* refresh lock timeout again so that client has more
                 * room to send lock cancel RPC.
                 */
                if (req->rq_ops->hpreq_fini)
                        req->rq_ops->hpreq_fini(req);

                spin_lock_bh(&req->rq_export->exp_rpc_lock);
                list_del_init(&req->rq_exp_list);
                spin_unlock_bh(&req->rq_export->exp_rpc_lock);
        }
}

static int ptlrpc_server_request_add(struct ptlrpc_service_part *svcpt,
                                     struct ptlrpc_request *req)
{
        int     rc;

        rc = ptlrpc_server_hpreq_init(svcpt, req);
        if (rc < 0)
                return rc;

        ptlrpc_nrs_req_add(svcpt, req, !!rc);

        return 0;
}

/**
 * Allow to handle high priority request
 * User can call it w/o any lock but need to hold
 * ptlrpc_service_part::scp_req_lock to get reliable result
 */
static bool ptlrpc_server_allow_high(struct ptlrpc_service_part *svcpt,
                                     bool force)
{
        int running = svcpt->scp_nthrs_running;

        if (!nrs_svcpt_has_hp(svcpt))
                return false;

        if (force)
                return true;

        if (unlikely(svcpt->scp_service->srv_req_portal == MDS_REQUEST_PORTAL &&
                     CFS_FAIL_PRECHECK(OBD_FAIL_PTLRPC_CANCEL_RESEND))) {
                /* leave just 1 thread for normal RPCs */
                running = PTLRPC_NTHRS_INIT;
                if (svcpt->scp_service->srv_ops.so_hpreq_handler)
                        running += 1;
        }

        if (svcpt->scp_nreqs_active >= running - 1)
                return false;

        if (svcpt->scp_nhreqs_active == 0)
                return true;

        return !ptlrpc_nrs_req_pending_nolock(svcpt, false) ||
               svcpt->scp_hreq_count < svcpt->scp_service->srv_hpreq_ratio;
}

static bool ptlrpc_server_high_pending(struct ptlrpc_service_part *svcpt,
                                       bool force)
{
        return ptlrpc_server_allow_high(svcpt, force) &&
               ptlrpc_nrs_req_pending_nolock(svcpt, true);
}

/**
 * Only allow normal priority requests on a service that has a high-priority
 * queue if forced (i.e. cleanup), if there are other high priority requests
 * already being processed (i.e. those threads can service more high-priority
 * requests), or if there are enough idle threads that a later thread can do
 * a high priority request.
 * User can call it w/o any lock but need to hold
 * ptlrpc_service_part::scp_req_lock to get reliable result
 */
static bool ptlrpc_server_allow_normal(struct ptlrpc_service_part *svcpt,
                                       bool force)
{
        int running = svcpt->scp_nthrs_running;

        if (unlikely(svcpt->scp_service->srv_req_portal == MDS_REQUEST_PORTAL &&
                     CFS_FAIL_PRECHECK(OBD_FAIL_PTLRPC_CANCEL_RESEND))) {
                /* leave just 1 thread for normal RPCs */
                running = PTLRPC_NTHRS_INIT;
                if (svcpt->scp_service->srv_ops.so_hpreq_handler)
                        running += 1;
        }

        if (force ||
            svcpt->scp_nreqs_active < running - 2)
                return true;

        if (svcpt->scp_nreqs_active >= running - 1)
                return false;

        return svcpt->scp_nhreqs_active > 0 || !nrs_svcpt_has_hp(svcpt);
}

static bool ptlrpc_server_normal_pending(struct ptlrpc_service_part *svcpt,
                                         bool force)
{
        return ptlrpc_server_allow_normal(svcpt, force) &&
               ptlrpc_nrs_req_pending_nolock(svcpt, false);
}

/**
 * Returns true if there are requests available in incoming
 * request queue for processing and it is allowed to fetch them.
 * User can call it w/o any lock but need to hold ptlrpc_service::scp_req_lock
 * to get reliable result
 * \see ptlrpc_server_allow_normal
 * \see ptlrpc_server_allow high
 */
static inline bool
ptlrpc_server_request_pending(struct ptlrpc_service_part *svcpt, bool force)
{
        return ptlrpc_server_high_pending(svcpt, force) ||
               ptlrpc_server_normal_pending(svcpt, force);
}

/**
 * Fetch a request for processing from queue of unprocessed requests.
 * Favors high-priority requests.
 * Returns a pointer to fetched request.
 */
static struct ptlrpc_request *
ptlrpc_server_request_get(struct ptlrpc_service_part *svcpt, bool force)
{
        struct ptlrpc_request *req = NULL;

        spin_lock(&svcpt->scp_req_lock);

        if (ptlrpc_server_high_pending(svcpt, force)) {
                req = ptlrpc_nrs_req_get_nolock(svcpt, true, force);
                if (req) {
                        svcpt->scp_hreq_count++;
                        goto got_request;
                }
        }

        if (ptlrpc_server_normal_pending(svcpt, force)) {
                req = ptlrpc_nrs_req_get_nolock(svcpt, false, force);
                if (req) {
                        svcpt->scp_hreq_count = 0;
                        goto got_request;
                }
        }

        spin_unlock(&svcpt->scp_req_lock);
        return NULL;

got_request:
        svcpt->scp_nreqs_active++;
        if (req->rq_hp)
                svcpt->scp_nhreqs_active++;

        spin_unlock(&svcpt->scp_req_lock);

        if (likely(req->rq_export))
                class_export_rpc_inc(req->rq_export);

        return req;
}

/**
 * Handle freshly incoming reqs, add to timed early reply list,
 * pass on to regular request queue.
 * All incoming requests pass through here before getting into
 * ptlrpc_server_handle_req later on.
 */
static int
ptlrpc_server_handle_req_in(struct ptlrpc_service_part *svcpt,
                            struct ptlrpc_thread *thread)
{
        struct ptlrpc_service *svc = svcpt->scp_service;
        struct ptlrpc_request *req;
        __u32 deadline;
        int rc;

        spin_lock(&svcpt->scp_lock);
        if (list_empty(&svcpt->scp_req_incoming)) {
                spin_unlock(&svcpt->scp_lock);
                return 0;
        }

        req = list_entry(svcpt->scp_req_incoming.next,
                         struct ptlrpc_request, rq_list);
        list_del_init(&req->rq_list);
        svcpt->scp_nreqs_incoming--;
        /* Consider this still a "queued" request as far as stats are
         * concerned
         */
        spin_unlock(&svcpt->scp_lock);

        /* go through security check/transform */
        rc = sptlrpc_svc_unwrap_request(req);
        switch (rc) {
        case SECSVC_OK:
                break;
        case SECSVC_COMPLETE:
                target_send_reply(req, 0, OBD_FAIL_MDS_ALL_REPLY_NET);
                goto err_req;
        case SECSVC_DROP:
                goto err_req;
        default:
                LBUG();
        }

        /*
         * for null-flavored rpc, msg has been unpacked by sptlrpc, although
         * redo it wouldn't be harmful.
         */
        if (SPTLRPC_FLVR_POLICY(req->rq_flvr.sf_rpc) != SPTLRPC_POLICY_NULL) {
                rc = ptlrpc_unpack_req_msg(req, req->rq_reqlen);
                if (rc != 0) {
                        CERROR("error unpacking request: ptl %d from %s x%llu\n",
                               svc->srv_req_portal, libcfs_id2str(req->rq_peer),
                               req->rq_xid);
                        goto err_req;
                }
        }

        rc = lustre_unpack_req_ptlrpc_body(req, MSG_PTLRPC_BODY_OFF);
        if (rc) {
                CERROR("error unpacking ptlrpc body: ptl %d from %s x%llu\n",
                       svc->srv_req_portal, libcfs_id2str(req->rq_peer),
                       req->rq_xid);
                goto err_req;
        }

        if (OBD_FAIL_CHECK(OBD_FAIL_PTLRPC_DROP_REQ_OPC) &&
            lustre_msg_get_opc(req->rq_reqmsg) == cfs_fail_val) {
                CERROR("drop incoming rpc opc %u, x%llu\n",
                       cfs_fail_val, req->rq_xid);
                goto err_req;
        }

        rc = -EINVAL;
        if (lustre_msg_get_type(req->rq_reqmsg) != PTL_RPC_MSG_REQUEST) {
                CERROR("wrong packet type received (type=%u) from %s\n",
                       lustre_msg_get_type(req->rq_reqmsg),
                       libcfs_id2str(req->rq_peer));
                goto err_req;
        }

        switch (lustre_msg_get_opc(req->rq_reqmsg)) {
        case MDS_WRITEPAGE:
        case OST_WRITE:
                req->rq_bulk_write = 1;
                break;
        case MDS_READPAGE:
        case OST_READ:
        case MGS_CONFIG_READ:
                req->rq_bulk_read = 1;
                break;
        }

        CDEBUG(D_RPCTRACE, "got req x%llu\n", req->rq_xid);

        req->rq_export = class_conn2export(
                lustre_msg_get_handle(req->rq_reqmsg));
        if (req->rq_export) {
                rc = ptlrpc_check_req(req);
                if (rc == 0) {
                        rc = sptlrpc_target_export_check(req->rq_export, req);
                        if (rc)
                                DEBUG_REQ(D_ERROR, req, "DROPPING req with illegal security flavor,");
                }

                if (rc)
                        goto err_req;
        }

        /* req_in handling should/must be fast */
        if (ktime_get_real_seconds() - req->rq_arrival_time.tv_sec > 5)
                DEBUG_REQ(D_WARNING, req, "Slow req_in handling %llds",
                          (s64)(ktime_get_real_seconds() -
                                req->rq_arrival_time.tv_sec));

        /* Set rpc server deadline and add it to the timed list */
        deadline = (lustre_msghdr_get_flags(req->rq_reqmsg) &
                    MSGHDR_AT_SUPPORT) ?
                   /* The max time the client expects us to take */
                   lustre_msg_get_timeout(req->rq_reqmsg) : obd_timeout;
        req->rq_deadline = req->rq_arrival_time.tv_sec + deadline;
        if (unlikely(deadline == 0)) {
                DEBUG_REQ(D_ERROR, req, "Dropping request with 0 timeout");
                goto err_req;
        }

        req->rq_svc_thread = thread;
        if (thread) {
                /* initialize request session, it is needed for request
                 * processing by target
                 */
                rc = lu_context_init(&req->rq_session,
                                     LCT_SERVER_SESSION | LCT_NOREF);
                if (rc) {
                        CERROR("%s: failure to initialize session: rc = %d\n",
                               thread->t_name, rc);
                        goto err_req;
                }
                req->rq_session.lc_thread = thread;
                lu_context_enter(&req->rq_session);
                req->rq_svc_thread->t_env->le_ses = &req->rq_session;
        }

        ptlrpc_at_add_timed(req);

        /* Move it over to the request processing queue */
        rc = ptlrpc_server_request_add(svcpt, req);
        if (rc)
                goto err_req;

        wake_up(&svcpt->scp_waitq);
        return 1;

err_req:
        ptlrpc_server_finish_request(svcpt, req);

        return 1;
}

/**
 * Main incoming request handling logic.
 * Calls handler function from service to do actual processing.
 */
static int
ptlrpc_server_handle_request(struct ptlrpc_service_part *svcpt,
                             struct ptlrpc_thread *thread)
{
        struct ptlrpc_service *svc = svcpt->scp_service;
        struct ptlrpc_request *request;
        struct timespec64 work_start;
        struct timespec64 work_end;
        struct timespec64 timediff;
        struct timespec64 arrived;
        unsigned long timediff_usecs;
        unsigned long arrived_usecs;
        int fail_opc = 0;

        request = ptlrpc_server_request_get(svcpt, false);
        if (!request)
                return 0;

        if (OBD_FAIL_CHECK(OBD_FAIL_PTLRPC_HPREQ_NOTIMEOUT))
                fail_opc = OBD_FAIL_PTLRPC_HPREQ_NOTIMEOUT;
        else if (OBD_FAIL_CHECK(OBD_FAIL_PTLRPC_HPREQ_TIMEOUT))
                fail_opc = OBD_FAIL_PTLRPC_HPREQ_TIMEOUT;

        if (unlikely(fail_opc)) {
                if (request->rq_export && request->rq_ops)
                        OBD_FAIL_TIMEOUT(fail_opc, 4);
        }

        ptlrpc_rqphase_move(request, RQ_PHASE_INTERPRET);

        if (OBD_FAIL_CHECK(OBD_FAIL_PTLRPC_DUMP_LOG))
                libcfs_debug_dumplog();

        ktime_get_real_ts64(&work_start);
        timediff = timespec64_sub(work_start, request->rq_arrival_time);
        timediff_usecs = timediff.tv_sec * USEC_PER_SEC +
                         timediff.tv_nsec / NSEC_PER_USEC;
        if (likely(svc->srv_stats)) {
                lprocfs_counter_add(svc->srv_stats, PTLRPC_REQWAIT_CNTR,
                                    timediff_usecs);
                lprocfs_counter_add(svc->srv_stats, PTLRPC_REQQDEPTH_CNTR,
                                    svcpt->scp_nreqs_incoming);
                lprocfs_counter_add(svc->srv_stats, PTLRPC_REQACTIVE_CNTR,
                                    svcpt->scp_nreqs_active);
                lprocfs_counter_add(svc->srv_stats, PTLRPC_TIMEOUT,
                                    at_get(&svcpt->scp_at_estimate));
        }

        if (likely(request->rq_export)) {
                if (unlikely(ptlrpc_check_req(request)))
                        goto put_conn;
        }

        /* Discard requests queued for longer than the deadline.
         * The deadline is increased if we send an early reply.
         */
        if (ktime_get_real_seconds() > request->rq_deadline) {
                DEBUG_REQ(D_ERROR, request, "Dropping timed-out request from %s: deadline %lld:%llds ago\n",
                          libcfs_id2str(request->rq_peer),
                          request->rq_deadline -
                          request->rq_arrival_time.tv_sec,
                          ktime_get_real_seconds() - request->rq_deadline);
                goto put_conn;
        }

        CDEBUG(D_RPCTRACE, "Handling RPC pname:cluuid+ref:pid:xid:nid:opc %s:%s+%d:%d:x%llu:%s:%d\n",
               current_comm(),
               (request->rq_export ?
                (char *)request->rq_export->exp_client_uuid.uuid : "0"),
               (request->rq_export ?
                atomic_read(&request->rq_export->exp_refcount) : -99),
               lustre_msg_get_status(request->rq_reqmsg), request->rq_xid,
               libcfs_id2str(request->rq_peer),
               lustre_msg_get_opc(request->rq_reqmsg));

        if (lustre_msg_get_opc(request->rq_reqmsg) != OBD_PING)
                CFS_FAIL_TIMEOUT_MS(OBD_FAIL_PTLRPC_PAUSE_REQ, cfs_fail_val);

        CDEBUG(D_NET, "got req %llu\n", request->rq_xid);

        /* re-assign request and sesson thread to the current one */
        request->rq_svc_thread = thread;
        if (thread) {
                LASSERT(request->rq_session.lc_thread);
                request->rq_session.lc_thread = thread;
                request->rq_session.lc_cookie = 0x55;
                thread->t_env->le_ses = &request->rq_session;
        }
        svc->srv_ops.so_req_handler(request);

        ptlrpc_rqphase_move(request, RQ_PHASE_COMPLETE);

put_conn:
        if (unlikely(ktime_get_real_seconds() > request->rq_deadline)) {
                DEBUG_REQ(D_WARNING, request,
                          "Request took longer than estimated (%lld:%llds); "
                          "client may timeout.",
                          (s64)request->rq_deadline -
                               request->rq_arrival_time.tv_sec,
                          (s64)ktime_get_real_seconds() - request->rq_deadline);
        }

        ktime_get_real_ts64(&work_end);
        timediff = timespec64_sub(work_end, work_start);
        timediff_usecs = timediff.tv_sec * USEC_PER_SEC +
                         timediff.tv_nsec / NSEC_PER_USEC;
        arrived = timespec64_sub(work_end, request->rq_arrival_time);
        arrived_usecs = arrived.tv_sec * USEC_PER_SEC +
                         arrived.tv_nsec / NSEC_PER_USEC;
        CDEBUG(D_RPCTRACE, "Handled RPC pname:cluuid+ref:pid:xid:nid:opc %s:%s+%d:%d:x%llu:%s:%d Request processed in %ldus (%ldus total) trans %llu rc %d/%d\n",
               current_comm(),
               (request->rq_export ?
                (char *)request->rq_export->exp_client_uuid.uuid : "0"),
               (request->rq_export ?
                atomic_read(&request->rq_export->exp_refcount) : -99),
               lustre_msg_get_status(request->rq_reqmsg),
               request->rq_xid,
               libcfs_id2str(request->rq_peer),
               lustre_msg_get_opc(request->rq_reqmsg),
               timediff_usecs,
               arrived_usecs,
               (request->rq_repmsg ?
                lustre_msg_get_transno(request->rq_repmsg) :
                request->rq_transno),
               request->rq_status,
               (request->rq_repmsg ?
                lustre_msg_get_status(request->rq_repmsg) : -999));
        if (likely(svc->srv_stats && request->rq_reqmsg)) {
                __u32 op = lustre_msg_get_opc(request->rq_reqmsg);
                int opc = opcode_offset(op);

                if (opc > 0 && !(op == LDLM_ENQUEUE || op == MDS_REINT)) {
                        LASSERT(opc < LUSTRE_MAX_OPCODES);
                        lprocfs_counter_add(svc->srv_stats,
                                            opc + EXTRA_MAX_OPCODES,
                                            timediff_usecs);
                }
        }
        if (unlikely(request->rq_early_count)) {
                DEBUG_REQ(D_ADAPTTO, request,
                          "sent %d early replies before finishing in %llds",
                          request->rq_early_count,
                          (s64)work_end.tv_sec -
                          request->rq_arrival_time.tv_sec);
        }

        ptlrpc_server_finish_active_request(svcpt, request);

        return 1;
}

/**
 * An internal function to process a single reply state object.
 */
static int
ptlrpc_handle_rs(struct ptlrpc_reply_state *rs)
{
        struct ptlrpc_service_part *svcpt = rs->rs_svcpt;
        struct ptlrpc_service *svc = svcpt->scp_service;
        struct obd_export *exp;
        int nlocks;
        int been_handled;

        exp = rs->rs_export;

        LASSERT(rs->rs_difficult);
        LASSERT(rs->rs_scheduled);
        LASSERT(list_empty(&rs->rs_list));

        spin_lock(&exp->exp_lock);
        /* Noop if removed already */
        list_del_init(&rs->rs_exp_list);
        spin_unlock(&exp->exp_lock);

        /* The disk commit callback holds exp_uncommitted_replies_lock while it
         * iterates over newly committed replies, removing them from
         * exp_uncommitted_replies.  It then drops this lock and schedules the
         * replies it found for handling here.
         *
         * We can avoid contention for exp_uncommitted_replies_lock between the
         * HRT threads and further commit callbacks by checking rs_committed
         * which is set in the commit callback while it holds both
         * rs_lock and exp_uncommitted_reples.
         *
         * If we see rs_committed clear, the commit callback _may_ not have
         * handled this reply yet and we race with it to grab
         * exp_uncommitted_replies_lock before removing the reply from
         * exp_uncommitted_replies.  Note that if we lose the race and the
         * reply has already been removed, list_del_init() is a noop.
         *
         * If we see rs_committed set, we know the commit callback is handling,
         * or has handled this reply since store reordering might allow us to
         * see rs_committed set out of sequence.  But since this is done
         * holding rs_lock, we can be sure it has all completed once we hold
         * rs_lock, which we do right next.
         */
        if (!rs->rs_committed) {
                spin_lock(&exp->exp_uncommitted_replies_lock);
                list_del_init(&rs->rs_obd_list);
                spin_unlock(&exp->exp_uncommitted_replies_lock);
        }

        spin_lock(&rs->rs_lock);

        been_handled = rs->rs_handled;
        rs->rs_handled = 1;

        nlocks = rs->rs_nlocks;          /* atomic "steal", but */
        rs->rs_nlocks = 0;                    /* locks still on rs_locks! */

        if (nlocks == 0 && !been_handled) {
                /* If we see this, we should already have seen the warning
                 * in mds_steal_ack_locks()
                 */
                CDEBUG(D_HA, "All locks stolen from rs %p x%lld.t%lld o%d NID %s\n",
                       rs,
                       rs->rs_xid, rs->rs_transno, rs->rs_opc,
                       libcfs_nid2str(exp->exp_connection->c_peer.nid));
        }

        if ((!been_handled && rs->rs_on_net) || nlocks > 0) {
                spin_unlock(&rs->rs_lock);

                if (!been_handled && rs->rs_on_net) {
                        LNetMDUnlink(rs->rs_md_h);
                        /* Ignore return code; we're racing with completion */
                }

                while (nlocks-- > 0)
                        ldlm_lock_decref(&rs->rs_locks[nlocks],
                                         rs->rs_modes[nlocks]);

                spin_lock(&rs->rs_lock);
        }

        rs->rs_scheduled = 0;

        if (!rs->rs_on_net) {
                /* Off the net */
                spin_unlock(&rs->rs_lock);

                class_export_put(exp);
                rs->rs_export = NULL;
                ptlrpc_rs_decref(rs);
                if (atomic_dec_and_test(&svcpt->scp_nreps_difficult) &&
                    svc->srv_is_stopping)
                        wake_up_all(&svcpt->scp_waitq);
                return 1;
        }

        /* still on the net; callback will schedule */
        spin_unlock(&rs->rs_lock);
        return 1;
}

static void
ptlrpc_check_rqbd_pool(struct ptlrpc_service_part *svcpt)
{
        int avail = svcpt->scp_nrqbds_posted;
        int low_water = test_req_buffer_pressure ? 0 :
                        svcpt->scp_service->srv_nbuf_per_group / 2;

        /* NB I'm not locking; just looking. */

        /* CAVEAT EMPTOR: We might be allocating buffers here because we've
         * allowed the request history to grow out of control.  We could put a
         * sanity check on that here and cull some history if we need the
         * space.
         */

        if (avail <= low_water)
                ptlrpc_grow_req_bufs(svcpt, 1);

        if (svcpt->scp_service->srv_stats) {
                lprocfs_counter_add(svcpt->scp_service->srv_stats,
                                    PTLRPC_REQBUF_AVAIL_CNTR, avail);
        }
}

static int
ptlrpc_retry_rqbds(void *arg)
{
        struct ptlrpc_service_part *svcpt = arg;

        svcpt->scp_rqbd_timeout = 0;
        return -ETIMEDOUT;
}

static inline int
ptlrpc_threads_enough(struct ptlrpc_service_part *svcpt)
{
        return svcpt->scp_nreqs_active <
               svcpt->scp_nthrs_running - 1 -
               (svcpt->scp_service->srv_ops.so_hpreq_handler != NULL);
}

/**
 * allowed to create more threads
 * user can call it w/o any lock but need to hold
 * ptlrpc_service_part::scp_lock to get reliable result
 */
static inline int
ptlrpc_threads_increasable(struct ptlrpc_service_part *svcpt)
{
        return svcpt->scp_nthrs_running +
               svcpt->scp_nthrs_starting <
               svcpt->scp_service->srv_nthrs_cpt_limit;
}

/**
 * too many requests and allowed to create more threads
 */
static inline int
ptlrpc_threads_need_create(struct ptlrpc_service_part *svcpt)
{
        return !ptlrpc_threads_enough(svcpt) &&
                ptlrpc_threads_increasable(svcpt);
}

static inline int
ptlrpc_thread_stopping(struct ptlrpc_thread *thread)
{
        return thread_is_stopping(thread) ||
               thread->t_svcpt->scp_service->srv_is_stopping;
}

static inline int
ptlrpc_rqbd_pending(struct ptlrpc_service_part *svcpt)
{
        return !list_empty(&svcpt->scp_rqbd_idle) &&
               svcpt->scp_rqbd_timeout == 0;
}

static inline int
ptlrpc_at_check(struct ptlrpc_service_part *svcpt)
{
        return svcpt->scp_at_check;
}

/**
 * requests wait on preprocessing
 * user can call it w/o any lock but need to hold
 * ptlrpc_service_part::scp_lock to get reliable result
 */
static inline int
ptlrpc_server_request_incoming(struct ptlrpc_service_part *svcpt)
{
        return !list_empty(&svcpt->scp_req_incoming);
}

static __attribute__((__noinline__)) int
ptlrpc_wait_event(struct ptlrpc_service_part *svcpt,
                  struct ptlrpc_thread *thread)
{
        /* Don't exit while there are replies to be handled */
        struct l_wait_info lwi = LWI_TIMEOUT(svcpt->scp_rqbd_timeout,
                                             ptlrpc_retry_rqbds, svcpt);

        /* XXX: Add this back when libcfs watchdog is merged upstream
        lc_watchdog_disable(thread->t_watchdog);
         */

        cond_resched();

        l_wait_event_exclusive_head(svcpt->scp_waitq,
                                    ptlrpc_thread_stopping(thread) ||
                                    ptlrpc_server_request_incoming(svcpt) ||
                                    ptlrpc_server_request_pending(svcpt,
                                                                  false) ||
                                    ptlrpc_rqbd_pending(svcpt) ||
                                    ptlrpc_at_check(svcpt), &lwi);

        if (ptlrpc_thread_stopping(thread))
                return -EINTR;

        /*
        lc_watchdog_touch(thread->t_watchdog,
                          ptlrpc_server_get_timeout(svcpt));
         */
        return 0;
}

/**
 * Main thread body for service threads.
 * Waits in a loop waiting for new requests to process to appear.
 * Every time an incoming requests is added to its queue, a waitq
 * is woken up and one of the threads will handle it.
 */
static int ptlrpc_main(void *arg)
{
        struct ptlrpc_thread *thread = arg;
        struct ptlrpc_service_part *svcpt = thread->t_svcpt;
        struct ptlrpc_service *svc = svcpt->scp_service;
        struct ptlrpc_reply_state *rs;
        struct group_info *ginfo = NULL;
        struct lu_env *env;
        int counter = 0, rc = 0;

        thread->t_pid = current_pid();
        unshare_fs_struct();

        /* NB: we will call cfs_cpt_bind() for all threads, because we
         * might want to run lustre server only on a subset of system CPUs,
         * in that case ->scp_cpt is CFS_CPT_ANY
         */
        rc = cfs_cpt_bind(svc->srv_cptable, svcpt->scp_cpt);
        if (rc != 0) {
                CWARN("%s: failed to bind %s on CPT %d\n",
                      svc->srv_name, thread->t_name, svcpt->scp_cpt);
        }

        ginfo = groups_alloc(0);
        if (!ginfo) {
                rc = -ENOMEM;
                goto out;
        }

        set_current_groups(ginfo);
        put_group_info(ginfo);

        if (svc->srv_ops.so_thr_init) {
                rc = svc->srv_ops.so_thr_init(thread);
                if (rc)
                        goto out;
        }

        env = kzalloc(sizeof(*env), GFP_NOFS);
        if (!env) {
                rc = -ENOMEM;
                goto out_srv_fini;
        }

        rc = lu_context_init(&env->le_ctx,
                             svc->srv_ctx_tags | LCT_REMEMBER | LCT_NOREF);
        if (rc)
                goto out_srv_fini;

        thread->t_env = env;
        env->le_ctx.lc_thread = thread;
        env->le_ctx.lc_cookie = 0x6;

        while (!list_empty(&svcpt->scp_rqbd_idle)) {
                rc = ptlrpc_server_post_idle_rqbds(svcpt);
                if (rc >= 0)
                        continue;

                CERROR("Failed to post rqbd for %s on CPT %d: %d\n",
                       svc->srv_name, svcpt->scp_cpt, rc);
                goto out_srv_fini;
        }

        /* Alloc reply state structure for this one */
        rs = libcfs_kvzalloc(svc->srv_max_reply_size, GFP_NOFS);
        if (!rs) {
                rc = -ENOMEM;
                goto out_srv_fini;
        }

        spin_lock(&svcpt->scp_lock);

        LASSERT(thread_is_starting(thread));
        thread_clear_flags(thread, SVC_STARTING);

        LASSERT(svcpt->scp_nthrs_starting == 1);
        svcpt->scp_nthrs_starting--;

        /* SVC_STOPPING may already be set here if someone else is trying
         * to stop the service while this new thread has been dynamically
         * forked. We still set SVC_RUNNING to let our creator know that
         * we are now running, however we will exit as soon as possible
         */
        thread_add_flags(thread, SVC_RUNNING);
        svcpt->scp_nthrs_running++;
        spin_unlock(&svcpt->scp_lock);

        /* wake up our creator in case he's still waiting. */
        wake_up(&thread->t_ctl_waitq);

        /*
        thread->t_watchdog = lc_watchdog_add(ptlrpc_server_get_timeout(svcpt),
                                             NULL, NULL);
         */

        spin_lock(&svcpt->scp_rep_lock);
        list_add(&rs->rs_list, &svcpt->scp_rep_idle);
        wake_up(&svcpt->scp_rep_waitq);
        spin_unlock(&svcpt->scp_rep_lock);

        CDEBUG(D_NET, "service thread %d (#%d) started\n", thread->t_id,
               svcpt->scp_nthrs_running);

        /* XXX maintain a list of all managed devices: insert here */
        while (!ptlrpc_thread_stopping(thread)) {
                if (ptlrpc_wait_event(svcpt, thread))
                        break;

                ptlrpc_check_rqbd_pool(svcpt);

                if (ptlrpc_threads_need_create(svcpt)) {
                        /* Ignore return code - we tried... */
                        ptlrpc_start_thread(svcpt, 0);
                }

                /* Process all incoming reqs before handling any */
                if (ptlrpc_server_request_incoming(svcpt)) {
                        lu_context_enter(&env->le_ctx);
                        env->le_ses = NULL;
                        ptlrpc_server_handle_req_in(svcpt, thread);
                        lu_context_exit(&env->le_ctx);

                        /* but limit ourselves in case of flood */
                        if (counter++ < 100)
                                continue;
                        counter = 0;
                }

                if (ptlrpc_at_check(svcpt))
                        ptlrpc_at_check_timed(svcpt);

                if (ptlrpc_server_request_pending(svcpt, false)) {
                        lu_context_enter(&env->le_ctx);
                        ptlrpc_server_handle_request(svcpt, thread);
                        lu_context_exit(&env->le_ctx);
                }

                if (ptlrpc_rqbd_pending(svcpt) &&
                    ptlrpc_server_post_idle_rqbds(svcpt) < 0) {
                        /* I just failed to repost request buffers.
                         * Wait for a timeout (unless something else
                         * happens) before I try again
                         */
                        svcpt->scp_rqbd_timeout = cfs_time_seconds(1) / 10;
                        CDEBUG(D_RPCTRACE, "Posted buffers: %d\n",
                               svcpt->scp_nrqbds_posted);
                }
        }

        /*
        lc_watchdog_delete(thread->t_watchdog);
        thread->t_watchdog = NULL;
        */

out_srv_fini:
        /*
         * deconstruct service specific state created by ptlrpc_start_thread()
         */
        if (svc->srv_ops.so_thr_done)
                svc->srv_ops.so_thr_done(thread);

        if (env) {
                lu_context_fini(&env->le_ctx);
                kfree(env);
        }
out:
        CDEBUG(D_RPCTRACE, "service thread [ %p : %u ] %d exiting: rc %d\n",
               thread, thread->t_pid, thread->t_id, rc);

        spin_lock(&svcpt->scp_lock);
        if (thread_test_and_clear_flags(thread, SVC_STARTING))
                svcpt->scp_nthrs_starting--;

        if (thread_test_and_clear_flags(thread, SVC_RUNNING)) {
                /* must know immediately */
                svcpt->scp_nthrs_running--;
        }

        thread->t_id = rc;
        thread_add_flags(thread, SVC_STOPPED);

        wake_up(&thread->t_ctl_waitq);
        spin_unlock(&svcpt->scp_lock);

        return rc;
}

static int hrt_dont_sleep(struct ptlrpc_hr_thread *hrt,
                          struct list_head *replies)
{
        int result;

        spin_lock(&hrt->hrt_lock);

        list_splice_init(&hrt->hrt_queue, replies);
        result = ptlrpc_hr.hr_stopping || !list_empty(replies);

        spin_unlock(&hrt->hrt_lock);
        return result;
}

/**
 * Main body of "handle reply" function.
 * It processes acked reply states
 */
static int ptlrpc_hr_main(void *arg)
{
        struct ptlrpc_hr_thread *hrt = arg;
        struct ptlrpc_hr_partition *hrp = hrt->hrt_partition;
        LIST_HEAD(replies);
        char threadname[20];
        int rc;

        snprintf(threadname, sizeof(threadname), "ptlrpc_hr%02d_%03d",
                 hrp->hrp_cpt, hrt->hrt_id);
        unshare_fs_struct();

        rc = cfs_cpt_bind(ptlrpc_hr.hr_cpt_table, hrp->hrp_cpt);
        if (rc != 0) {
                CWARN("Failed to bind %s on CPT %d of CPT table %p: rc = %d\n",
                      threadname, hrp->hrp_cpt, ptlrpc_hr.hr_cpt_table, rc);
        }

        atomic_inc(&hrp->hrp_nstarted);
        wake_up(&ptlrpc_hr.hr_waitq);

        while (!ptlrpc_hr.hr_stopping) {
                l_wait_condition(hrt->hrt_waitq, hrt_dont_sleep(hrt, &replies));

                while (!list_empty(&replies)) {
                        struct ptlrpc_reply_state *rs;

                        rs = list_entry(replies.prev, struct ptlrpc_reply_state,
                                        rs_list);
                        list_del_init(&rs->rs_list);
                        ptlrpc_handle_rs(rs);
                }
        }

        atomic_inc(&hrp->hrp_nstopped);
        wake_up(&ptlrpc_hr.hr_waitq);

        return 0;
}

static void ptlrpc_stop_hr_threads(void)
{
        struct ptlrpc_hr_partition *hrp;
        int i;
        int j;

        ptlrpc_hr.hr_stopping = 1;

        cfs_percpt_for_each(hrp, i, ptlrpc_hr.hr_partitions) {
                if (!hrp->hrp_thrs)
                        continue; /* uninitialized */
                for (j = 0; j < hrp->hrp_nthrs; j++)
                        wake_up_all(&hrp->hrp_thrs[j].hrt_waitq);
        }

        cfs_percpt_for_each(hrp, i, ptlrpc_hr.hr_partitions) {
                if (!hrp->hrp_thrs)
                        continue; /* uninitialized */
                wait_event(ptlrpc_hr.hr_waitq,
                           atomic_read(&hrp->hrp_nstopped) ==
                           atomic_read(&hrp->hrp_nstarted));
        }
}

static int ptlrpc_start_hr_threads(void)
{
        struct ptlrpc_hr_partition *hrp;
        int i;
        int j;

        cfs_percpt_for_each(hrp, i, ptlrpc_hr.hr_partitions) {
                int rc = 0;

                for (j = 0; j < hrp->hrp_nthrs; j++) {
                        struct  ptlrpc_hr_thread *hrt = &hrp->hrp_thrs[j];
                        struct task_struct *task;

                        task = kthread_run(ptlrpc_hr_main,
                                           &hrp->hrp_thrs[j],
                                           "ptlrpc_hr%02d_%03d",
                                           hrp->hrp_cpt, hrt->hrt_id);
                        if (IS_ERR(task)) {
                                rc = PTR_ERR(task);
                                break;
                        }
                }
                wait_event(ptlrpc_hr.hr_waitq,
                           atomic_read(&hrp->hrp_nstarted) == j);

                if (rc < 0) {
                        CERROR("cannot start reply handler thread %d:%d: rc = %d\n",
                               i, j, rc);
                        ptlrpc_stop_hr_threads();
                        return rc;
                }
        }
        return 0;
}

static void ptlrpc_svcpt_stop_threads(struct ptlrpc_service_part *svcpt)
{
        struct l_wait_info lwi = { 0 };
        struct ptlrpc_thread *thread;
        LIST_HEAD(zombie);

        CDEBUG(D_INFO, "Stopping threads for service %s\n",
               svcpt->scp_service->srv_name);

        spin_lock(&svcpt->scp_lock);
        /* let the thread know that we would like it to stop asap */
        list_for_each_entry(thread, &svcpt->scp_threads, t_link) {
                CDEBUG(D_INFO, "Stopping thread %s #%u\n",
                       svcpt->scp_service->srv_thread_name, thread->t_id);
                thread_add_flags(thread, SVC_STOPPING);
        }

        wake_up_all(&svcpt->scp_waitq);

        while (!list_empty(&svcpt->scp_threads)) {
                thread = list_entry(svcpt->scp_threads.next,
                                    struct ptlrpc_thread, t_link);
                if (thread_is_stopped(thread)) {
                        list_del(&thread->t_link);
                        list_add(&thread->t_link, &zombie);
                        continue;
                }
                spin_unlock(&svcpt->scp_lock);

                CDEBUG(D_INFO, "waiting for stopping-thread %s #%u\n",
                       svcpt->scp_service->srv_thread_name, thread->t_id);
                l_wait_event(thread->t_ctl_waitq,
                             thread_is_stopped(thread), &lwi);

                spin_lock(&svcpt->scp_lock);
        }

        spin_unlock(&svcpt->scp_lock);

        while (!list_empty(&zombie)) {
                thread = list_entry(zombie.next,
                                    struct ptlrpc_thread, t_link);
                list_del(&thread->t_link);
                kfree(thread);
        }
}

/**
 * Stops all threads of a particular service \a svc
 */
static void ptlrpc_stop_all_threads(struct ptlrpc_service *svc)
{
        struct ptlrpc_service_part *svcpt;
        int i;

        ptlrpc_service_for_each_part(svcpt, i, svc) {
                if (svcpt->scp_service)
                        ptlrpc_svcpt_stop_threads(svcpt);
        }
}

int ptlrpc_start_threads(struct ptlrpc_service *svc)
{
        int rc = 0;
        int i;
        int j;

        /* We require 2 threads min, see note in ptlrpc_server_handle_request */
        LASSERT(svc->srv_nthrs_cpt_init >= PTLRPC_NTHRS_INIT);

        for (i = 0; i < svc->srv_ncpts; i++) {
                for (j = 0; j < svc->srv_nthrs_cpt_init; j++) {
                        rc = ptlrpc_start_thread(svc->srv_parts[i], 1);
                        if (rc == 0)
                                continue;

                        if (rc != -EMFILE)
                                goto failed;
                        /* We have enough threads, don't start more. b=15759 */
                        break;
                }
        }

        return 0;
 failed:
        CERROR("cannot start %s thread #%d_%d: rc %d\n",
               svc->srv_thread_name, i, j, rc);
        ptlrpc_stop_all_threads(svc);
        return rc;
}

int ptlrpc_start_thread(struct ptlrpc_service_part *svcpt, int wait)
{
        struct l_wait_info lwi = { 0 };
        struct ptlrpc_thread *thread;
        struct ptlrpc_service *svc;
        struct task_struct *task;
        int rc;

        svc = svcpt->scp_service;

        CDEBUG(D_RPCTRACE, "%s[%d] started %d min %d max %d\n",
               svc->srv_name, svcpt->scp_cpt, svcpt->scp_nthrs_running,
               svc->srv_nthrs_cpt_init, svc->srv_nthrs_cpt_limit);

 again:
        if (unlikely(svc->srv_is_stopping))
                return -ESRCH;

        if (!ptlrpc_threads_increasable(svcpt) ||
            (OBD_FAIL_CHECK(OBD_FAIL_TGT_TOOMANY_THREADS) &&
             svcpt->scp_nthrs_running == svc->srv_nthrs_cpt_init - 1))
                return -EMFILE;

        thread = kzalloc_node(sizeof(*thread), GFP_NOFS,
                              cfs_cpt_spread_node(svc->srv_cptable,
                                                  svcpt->scp_cpt));
        if (!thread)
                return -ENOMEM;
        init_waitqueue_head(&thread->t_ctl_waitq);

        spin_lock(&svcpt->scp_lock);
        if (!ptlrpc_threads_increasable(svcpt)) {
                spin_unlock(&svcpt->scp_lock);
                kfree(thread);
                return -EMFILE;
        }

        if (svcpt->scp_nthrs_starting != 0) {
                /* serialize starting because some modules (obdfilter)
                 * might require unique and contiguous t_id
                 */
                LASSERT(svcpt->scp_nthrs_starting == 1);
                spin_unlock(&svcpt->scp_lock);
                kfree(thread);
                if (wait) {
                        CDEBUG(D_INFO, "Waiting for creating thread %s #%d\n",
                               svc->srv_thread_name, svcpt->scp_thr_nextid);
                        schedule();
                        goto again;
                }

                CDEBUG(D_INFO, "Creating thread %s #%d race, retry later\n",
                       svc->srv_thread_name, svcpt->scp_thr_nextid);
                return -EAGAIN;
        }

        svcpt->scp_nthrs_starting++;
        thread->t_id = svcpt->scp_thr_nextid++;
        thread_add_flags(thread, SVC_STARTING);
        thread->t_svcpt = svcpt;

        list_add(&thread->t_link, &svcpt->scp_threads);
        spin_unlock(&svcpt->scp_lock);

        if (svcpt->scp_cpt >= 0) {
                snprintf(thread->t_name, sizeof(thread->t_name), "%s%02d_%03d",
                         svc->srv_thread_name, svcpt->scp_cpt, thread->t_id);
        } else {
                snprintf(thread->t_name, sizeof(thread->t_name), "%s_%04d",
                         svc->srv_thread_name, thread->t_id);
        }

        CDEBUG(D_RPCTRACE, "starting thread '%s'\n", thread->t_name);
        task = kthread_run(ptlrpc_main, thread, "%s", thread->t_name);
        if (IS_ERR(task)) {
                rc = PTR_ERR(task);
                CERROR("cannot start thread '%s': rc = %d\n",
                       thread->t_name, rc);
                spin_lock(&svcpt->scp_lock);
                --svcpt->scp_nthrs_starting;
                if (thread_is_stopping(thread)) {
                        /* this ptlrpc_thread is being handled
                         * by ptlrpc_svcpt_stop_threads now
                         */
                        thread_add_flags(thread, SVC_STOPPED);
                        wake_up(&thread->t_ctl_waitq);
                        spin_unlock(&svcpt->scp_lock);
                } else {
                        list_del(&thread->t_link);
                        spin_unlock(&svcpt->scp_lock);
                        kfree(thread);
                }
                return rc;
        }

        if (!wait)
                return 0;

        l_wait_event(thread->t_ctl_waitq,
                     thread_is_running(thread) || thread_is_stopped(thread),
                     &lwi);

        rc = thread_is_stopped(thread) ? thread->t_id : 0;
        return rc;
}

int ptlrpc_hr_init(void)
{
        struct ptlrpc_hr_partition *hrp;
        struct ptlrpc_hr_thread *hrt;
        int rc;
        int i;
        int j;
        int weight;

        memset(&ptlrpc_hr, 0, sizeof(ptlrpc_hr));
        ptlrpc_hr.hr_cpt_table = cfs_cpt_table;

        ptlrpc_hr.hr_partitions = cfs_percpt_alloc(ptlrpc_hr.hr_cpt_table,
                                                   sizeof(*hrp));
        if (!ptlrpc_hr.hr_partitions)
                return -ENOMEM;

        init_waitqueue_head(&ptlrpc_hr.hr_waitq);

        weight = cpumask_weight(topology_sibling_cpumask(0));

        cfs_percpt_for_each(hrp, i, ptlrpc_hr.hr_partitions) {
                hrp->hrp_cpt = i;

                atomic_set(&hrp->hrp_nstarted, 0);
                atomic_set(&hrp->hrp_nstopped, 0);

                hrp->hrp_nthrs = cfs_cpt_weight(ptlrpc_hr.hr_cpt_table, i);
                hrp->hrp_nthrs /= weight;
                if (hrp->hrp_nthrs == 0)
                        hrp->hrp_nthrs = 1;

                hrp->hrp_thrs =
                        kzalloc_node(hrp->hrp_nthrs * sizeof(*hrt), GFP_NOFS,
                                     cfs_cpt_spread_node(ptlrpc_hr.hr_cpt_table,
                                                         i));
                if (!hrp->hrp_thrs) {
                        rc = -ENOMEM;
                        goto out;
                }

                for (j = 0; j < hrp->hrp_nthrs; j++) {
                        hrt = &hrp->hrp_thrs[j];

                        hrt->hrt_id = j;
                        hrt->hrt_partition = hrp;
                        init_waitqueue_head(&hrt->hrt_waitq);
                        spin_lock_init(&hrt->hrt_lock);
                        INIT_LIST_HEAD(&hrt->hrt_queue);
                }
        }

        rc = ptlrpc_start_hr_threads();
out:
        if (rc != 0)
                ptlrpc_hr_fini();
        return rc;
}

void ptlrpc_hr_fini(void)
{
        struct ptlrpc_hr_partition *hrp;
        int i;

        if (!ptlrpc_hr.hr_partitions)
                return;

        ptlrpc_stop_hr_threads();

        cfs_percpt_for_each(hrp, i, ptlrpc_hr.hr_partitions) {
                kfree(hrp->hrp_thrs);
        }

        cfs_percpt_free(ptlrpc_hr.hr_partitions);
        ptlrpc_hr.hr_partitions = NULL;
}

/**
 * Wait until all already scheduled replies are processed.
 */
static void ptlrpc_wait_replies(struct ptlrpc_service_part *svcpt)
{
        while (1) {
                int rc;
                struct l_wait_info lwi = LWI_TIMEOUT(cfs_time_seconds(10),
                                                     NULL, NULL);

                rc = l_wait_event(svcpt->scp_waitq,
                                  atomic_read(&svcpt->scp_nreps_difficult) == 0,
                                  &lwi);
                if (rc == 0)
                        break;
                CWARN("Unexpectedly long timeout %s %p\n",
                      svcpt->scp_service->srv_name, svcpt->scp_service);
        }
}

static void
ptlrpc_service_del_atimer(struct ptlrpc_service *svc)
{
        struct ptlrpc_service_part *svcpt;
        int i;

        /* early disarm AT timer... */
        ptlrpc_service_for_each_part(svcpt, i, svc) {
                if (svcpt->scp_service)
                        del_timer(&svcpt->scp_at_timer);
        }
}

static void
ptlrpc_service_unlink_rqbd(struct ptlrpc_service *svc)
{
        struct ptlrpc_service_part *svcpt;
        struct ptlrpc_request_buffer_desc *rqbd;
        struct l_wait_info lwi;
        int rc;
        int i;

        /* All history will be culled when the next request buffer is
         * freed in ptlrpc_service_purge_all()
         */
        svc->srv_hist_nrqbds_cpt_max = 0;

        rc = LNetClearLazyPortal(svc->srv_req_portal);
        LASSERT(rc == 0);

        ptlrpc_service_for_each_part(svcpt, i, svc) {
                if (!svcpt->scp_service)
                        break;

                /* Unlink all the request buffers.  This forces a 'final'
                 * event with its 'unlink' flag set for each posted rqbd
                 */
                list_for_each_entry(rqbd, &svcpt->scp_rqbd_posted,
                                    rqbd_list) {
                        rc = LNetMDUnlink(rqbd->rqbd_md_h);
                        LASSERT(rc == 0 || rc == -ENOENT);
                }
        }

        ptlrpc_service_for_each_part(svcpt, i, svc) {
                if (!svcpt->scp_service)
                        break;

                /* Wait for the network to release any buffers
                 * it's currently filling
                 */
                spin_lock(&svcpt->scp_lock);
                while (svcpt->scp_nrqbds_posted != 0) {
                        spin_unlock(&svcpt->scp_lock);
                        /* Network access will complete in finite time but
                         * the HUGE timeout lets us CWARN for visibility
                         * of sluggish LNDs
                         */
                        lwi = LWI_TIMEOUT_INTERVAL(
                                        cfs_time_seconds(LONG_UNLINK),
                                        cfs_time_seconds(1), NULL, NULL);
                        rc = l_wait_event(svcpt->scp_waitq,
                                          svcpt->scp_nrqbds_posted == 0, &lwi);
                        if (rc == -ETIMEDOUT) {
                                CWARN("Service %s waiting for request buffers\n",
                                      svcpt->scp_service->srv_name);
                        }
                        spin_lock(&svcpt->scp_lock);
                }
                spin_unlock(&svcpt->scp_lock);
        }
}

static void
ptlrpc_service_purge_all(struct ptlrpc_service *svc)
{
        struct ptlrpc_service_part *svcpt;
        struct ptlrpc_request_buffer_desc *rqbd;
        struct ptlrpc_request *req;
        struct ptlrpc_reply_state *rs;
        int i;

        ptlrpc_service_for_each_part(svcpt, i, svc) {
                if (!svcpt->scp_service)
                        break;

                spin_lock(&svcpt->scp_rep_lock);
                while (!list_empty(&svcpt->scp_rep_active)) {
                        rs = list_entry(svcpt->scp_rep_active.next,
                                        struct ptlrpc_reply_state, rs_list);
                        spin_lock(&rs->rs_lock);
                        ptlrpc_schedule_difficult_reply(rs);
                        spin_unlock(&rs->rs_lock);
                }
                spin_unlock(&svcpt->scp_rep_lock);

                /* purge the request queue.  NB No new replies (rqbds
                 * all unlinked) and no service threads, so I'm the only
                 * thread noodling the request queue now
                 */
                while (!list_empty(&svcpt->scp_req_incoming)) {
                        req = list_entry(svcpt->scp_req_incoming.next,
                                         struct ptlrpc_request, rq_list);

                        list_del(&req->rq_list);
                        svcpt->scp_nreqs_incoming--;
                        ptlrpc_server_finish_request(svcpt, req);
                }

                while (ptlrpc_server_request_pending(svcpt, true)) {
                        req = ptlrpc_server_request_get(svcpt, true);
                        ptlrpc_server_finish_active_request(svcpt, req);
                }

                LASSERT(list_empty(&svcpt->scp_rqbd_posted));
                LASSERT(svcpt->scp_nreqs_incoming == 0);
                LASSERT(svcpt->scp_nreqs_active == 0);
                /* history should have been culled by
                 * ptlrpc_server_finish_request
                 */
                LASSERT(svcpt->scp_hist_nrqbds == 0);

                /* Now free all the request buffers since nothing
                 * references them any more...
                 */

                while (!list_empty(&svcpt->scp_rqbd_idle)) {
                        rqbd = list_entry(svcpt->scp_rqbd_idle.next,
                                          struct ptlrpc_request_buffer_desc,
                                          rqbd_list);
                        ptlrpc_free_rqbd(rqbd);
                }
                ptlrpc_wait_replies(svcpt);

                while (!list_empty(&svcpt->scp_rep_idle)) {
                        rs = list_entry(svcpt->scp_rep_idle.next,
                                        struct ptlrpc_reply_state,
                                        rs_list);
                        list_del(&rs->rs_list);
                        kvfree(rs);
                }
        }
}

static void
ptlrpc_service_free(struct ptlrpc_service *svc)
{
        struct ptlrpc_service_part *svcpt;
        struct ptlrpc_at_array *array;
        int i;

        ptlrpc_service_for_each_part(svcpt, i, svc) {
                if (!svcpt->scp_service)
                        break;

                /* In case somebody rearmed this in the meantime */
                del_timer(&svcpt->scp_at_timer);
                array = &svcpt->scp_at_array;

                kfree(array->paa_reqs_array);
                array->paa_reqs_array = NULL;
                kfree(array->paa_reqs_count);
                array->paa_reqs_count = NULL;
        }

        ptlrpc_service_for_each_part(svcpt, i, svc)
                kfree(svcpt);

        if (svc->srv_cpts)
                cfs_expr_list_values_free(svc->srv_cpts, svc->srv_ncpts);

        kfree(svc);
}

int ptlrpc_unregister_service(struct ptlrpc_service *service)
{
        CDEBUG(D_NET, "%s: tearing down\n", service->srv_name);

        service->srv_is_stopping = 1;

        mutex_lock(&ptlrpc_all_services_mutex);
        list_del_init(&service->srv_list);
        mutex_unlock(&ptlrpc_all_services_mutex);

        ptlrpc_service_del_atimer(service);
        ptlrpc_stop_all_threads(service);

        ptlrpc_service_unlink_rqbd(service);
        ptlrpc_service_purge_all(service);
        ptlrpc_service_nrs_cleanup(service);

        ptlrpc_lprocfs_unregister_service(service);
        ptlrpc_sysfs_unregister_service(service);

        ptlrpc_service_free(service);

        return 0;
}
EXPORT_SYMBOL(ptlrpc_unregister_service);