/*
 * 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, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA
 *
 * GPL HEADER END
 */
/*
 * Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
 * Copyright (c) 2012, Intel Corporation.
 */
/*
 * This file is part of Lustre, http://www.lustre.org/
 * Lustre is a trademark of Sun Microsystems, Inc.
 *
 * Author: liang@whamcloud.com
 */

#define DEBUG_SUBSYSTEM S_LNET

#include <linux/cpu.h>
#include <linux/sched.h>
#include "../../../include/linux/libcfs/libcfs.h"

#ifdef CONFIG_SMP

/**
 * modparam for setting number of partitions
 *
 *  0 : estimate best value based on cores or NUMA nodes
 *  1 : disable multiple partitions
 * >1 : specify number of partitions
 */
static int      cpu_npartitions;
module_param(cpu_npartitions, int, 0444);
MODULE_PARM_DESC(cpu_npartitions, "# of CPU partitions");

/**
 * modparam for setting CPU partitions patterns:
 *
 * i.e: "0[0,1,2,3] 1[4,5,6,7]", number before bracket is CPU partition ID,
 *      number in bracket is processor ID (core or HT)
 *
 * i.e: "N 0[0,1] 1[2,3]" the first character 'N' means numbers in bracket
 *       are NUMA node ID, number before bracket is CPU partition ID.
 *
 * NB: If user specified cpu_pattern, cpu_npartitions will be ignored
 */
static char     *cpu_pattern = "";
module_param(cpu_pattern, charp, 0444);
MODULE_PARM_DESC(cpu_pattern, "CPU partitions pattern");

struct cfs_cpt_data {
        /* serialize hotplug etc */
        spinlock_t              cpt_lock;
        /* reserved for hotplug */
        unsigned long           cpt_version;
        /* mutex to protect cpt_cpumask */
        struct mutex            cpt_mutex;
        /* scratch buffer for set/unset_node */
        cpumask_t               *cpt_cpumask;
};

static struct cfs_cpt_data      cpt_data;

static void cfs_cpu_core_siblings(int cpu, cpumask_t *mask)
{
        /* return cpumask of cores in the same socket */
        cpumask_copy(mask, topology_core_cpumask(cpu));
}

/* return cpumask of HTs in the same core */
static void cfs_cpu_ht_siblings(int cpu, cpumask_t *mask)
{
        cpumask_copy(mask, topology_thread_cpumask(cpu));
}

static void cfs_node_to_cpumask(int node, cpumask_t *mask)
{
        cpumask_copy(mask, cpumask_of_node(node));
}

void
cfs_cpt_table_free(struct cfs_cpt_table *cptab)
{
        int     i;

        if (cptab->ctb_cpu2cpt != NULL) {
                LIBCFS_FREE(cptab->ctb_cpu2cpt,
                            num_possible_cpus() *
                            sizeof(cptab->ctb_cpu2cpt[0]));
        }

        for (i = 0; cptab->ctb_parts != NULL && i < cptab->ctb_nparts; i++) {
                struct cfs_cpu_partition *part = &cptab->ctb_parts[i];

                if (part->cpt_nodemask != NULL) {
                        LIBCFS_FREE(part->cpt_nodemask,
                                    sizeof(*part->cpt_nodemask));
                }

                if (part->cpt_cpumask != NULL)
                        LIBCFS_FREE(part->cpt_cpumask, cpumask_size());
        }

        if (cptab->ctb_parts != NULL) {
                LIBCFS_FREE(cptab->ctb_parts,
                            cptab->ctb_nparts * sizeof(cptab->ctb_parts[0]));
        }

        if (cptab->ctb_nodemask != NULL)
                LIBCFS_FREE(cptab->ctb_nodemask, sizeof(*cptab->ctb_nodemask));
        if (cptab->ctb_cpumask != NULL)
                LIBCFS_FREE(cptab->ctb_cpumask, cpumask_size());

        LIBCFS_FREE(cptab, sizeof(*cptab));
}
EXPORT_SYMBOL(cfs_cpt_table_free);

struct cfs_cpt_table *
cfs_cpt_table_alloc(unsigned int ncpt)
{
        struct cfs_cpt_table *cptab;
        int     i;

        LIBCFS_ALLOC(cptab, sizeof(*cptab));
        if (cptab == NULL)
                return NULL;

        cptab->ctb_nparts = ncpt;

        LIBCFS_ALLOC(cptab->ctb_cpumask, cpumask_size());
        LIBCFS_ALLOC(cptab->ctb_nodemask, sizeof(*cptab->ctb_nodemask));

        if (cptab->ctb_cpumask == NULL || cptab->ctb_nodemask == NULL)
                goto failed;

        LIBCFS_ALLOC(cptab->ctb_cpu2cpt,
                     num_possible_cpus() * sizeof(cptab->ctb_cpu2cpt[0]));
        if (cptab->ctb_cpu2cpt == NULL)
                goto failed;

        memset(cptab->ctb_cpu2cpt, -1,
               num_possible_cpus() * sizeof(cptab->ctb_cpu2cpt[0]));

        LIBCFS_ALLOC(cptab->ctb_parts, ncpt * sizeof(cptab->ctb_parts[0]));
        if (cptab->ctb_parts == NULL)
                goto failed;

        for (i = 0; i < ncpt; i++) {
                struct cfs_cpu_partition *part = &cptab->ctb_parts[i];

                LIBCFS_ALLOC(part->cpt_cpumask, cpumask_size());
                LIBCFS_ALLOC(part->cpt_nodemask, sizeof(*part->cpt_nodemask));
                if (part->cpt_cpumask == NULL || part->cpt_nodemask == NULL)
                        goto failed;
        }

        spin_lock(&cpt_data.cpt_lock);
        /* Reserved for hotplug */
        cptab->ctb_version = cpt_data.cpt_version;
        spin_unlock(&cpt_data.cpt_lock);

        return cptab;

 failed:
        cfs_cpt_table_free(cptab);
        return NULL;
}
EXPORT_SYMBOL(cfs_cpt_table_alloc);

int
cfs_cpt_table_print(struct cfs_cpt_table *cptab, char *buf, int len)
{
        char    *tmp = buf;
        int     rc = 0;
        int     i;
        int     j;

        for (i = 0; i < cptab->ctb_nparts; i++) {
                if (len > 0) {
                        rc = snprintf(tmp, len, "%d\t: ", i);
                        len -= rc;
                }

                if (len <= 0) {
                        rc = -EFBIG;
                        goto out;
                }

                tmp += rc;
                for_each_cpu_mask(j, *cptab->ctb_parts[i].cpt_cpumask) {
                        rc = snprintf(tmp, len, "%d ", j);
                        len -= rc;
                        if (len <= 0) {
                                rc = -EFBIG;
                                goto out;
                        }
                        tmp += rc;
                }

                *tmp = '\n';
                tmp++;
                len--;
        }

 out:
        if (rc < 0)
                return rc;

        return tmp - buf;
}
EXPORT_SYMBOL(cfs_cpt_table_print);

int
cfs_cpt_number(struct cfs_cpt_table *cptab)
{
        return cptab->ctb_nparts;
}
EXPORT_SYMBOL(cfs_cpt_number);

int
cfs_cpt_weight(struct cfs_cpt_table *cptab, int cpt)
{
        LASSERT(cpt == CFS_CPT_ANY || (cpt >= 0 && cpt < cptab->ctb_nparts));

        return cpt == CFS_CPT_ANY ?
               cpus_weight(*cptab->ctb_cpumask) :
               cpus_weight(*cptab->ctb_parts[cpt].cpt_cpumask);
}
EXPORT_SYMBOL(cfs_cpt_weight);

int
cfs_cpt_online(struct cfs_cpt_table *cptab, int cpt)
{
        LASSERT(cpt == CFS_CPT_ANY || (cpt >= 0 && cpt < cptab->ctb_nparts));

        return cpt == CFS_CPT_ANY ?
               any_online_cpu(*cptab->ctb_cpumask) != NR_CPUS :
               any_online_cpu(*cptab->ctb_parts[cpt].cpt_cpumask) != NR_CPUS;
}
EXPORT_SYMBOL(cfs_cpt_online);

cpumask_t *
cfs_cpt_cpumask(struct cfs_cpt_table *cptab, int cpt)
{
        LASSERT(cpt == CFS_CPT_ANY || (cpt >= 0 && cpt < cptab->ctb_nparts));

        return cpt == CFS_CPT_ANY ?
               cptab->ctb_cpumask : cptab->ctb_parts[cpt].cpt_cpumask;
}
EXPORT_SYMBOL(cfs_cpt_cpumask);

nodemask_t *
cfs_cpt_nodemask(struct cfs_cpt_table *cptab, int cpt)
{
        LASSERT(cpt == CFS_CPT_ANY || (cpt >= 0 && cpt < cptab->ctb_nparts));

        return cpt == CFS_CPT_ANY ?
               cptab->ctb_nodemask : cptab->ctb_parts[cpt].cpt_nodemask;
}
EXPORT_SYMBOL(cfs_cpt_nodemask);

int
cfs_cpt_set_cpu(struct cfs_cpt_table *cptab, int cpt, int cpu)
{
        int     node;

        LASSERT(cpt >= 0 && cpt < cptab->ctb_nparts);

        if (cpu < 0 || cpu >= NR_CPUS || !cpu_online(cpu)) {
                CDEBUG(D_INFO, "CPU %d is invalid or it's offline\n", cpu);
                return 0;
        }

        if (cptab->ctb_cpu2cpt[cpu] != -1) {
                CDEBUG(D_INFO, "CPU %d is already in partition %d\n",
                       cpu, cptab->ctb_cpu2cpt[cpu]);
                return 0;
        }

        cptab->ctb_cpu2cpt[cpu] = cpt;

        LASSERT(!cpu_isset(cpu, *cptab->ctb_cpumask));
        LASSERT(!cpu_isset(cpu, *cptab->ctb_parts[cpt].cpt_cpumask));

        cpu_set(cpu, *cptab->ctb_cpumask);
        cpu_set(cpu, *cptab->ctb_parts[cpt].cpt_cpumask);

        node = cpu_to_node(cpu);

        /* first CPU of @node in this CPT table */
        if (!node_isset(node, *cptab->ctb_nodemask))
                node_set(node, *cptab->ctb_nodemask);

        /* first CPU of @node in this partition */
        if (!node_isset(node, *cptab->ctb_parts[cpt].cpt_nodemask))
                node_set(node, *cptab->ctb_parts[cpt].cpt_nodemask);

        return 1;
}
EXPORT_SYMBOL(cfs_cpt_set_cpu);

void
cfs_cpt_unset_cpu(struct cfs_cpt_table *cptab, int cpt, int cpu)
{
        int     node;
        int     i;

        LASSERT(cpt == CFS_CPT_ANY || (cpt >= 0 && cpt < cptab->ctb_nparts));

        if (cpu < 0 || cpu >= NR_CPUS) {
                CDEBUG(D_INFO, "Invalid CPU id %d\n", cpu);
                return;
        }

        if (cpt == CFS_CPT_ANY) {
                /* caller doesn't know the partition ID */
                cpt = cptab->ctb_cpu2cpt[cpu];
                if (cpt < 0) { /* not set in this CPT-table */
                        CDEBUG(D_INFO, "Try to unset cpu %d which is not in CPT-table %p\n",
                               cpt, cptab);
                        return;
                }

        } else if (cpt != cptab->ctb_cpu2cpt[cpu]) {
                CDEBUG(D_INFO,
                       "CPU %d is not in cpu-partition %d\n", cpu, cpt);
                return;
        }

        LASSERT(cpu_isset(cpu, *cptab->ctb_parts[cpt].cpt_cpumask));
        LASSERT(cpu_isset(cpu, *cptab->ctb_cpumask));

        cpu_clear(cpu, *cptab->ctb_parts[cpt].cpt_cpumask);
        cpu_clear(cpu, *cptab->ctb_cpumask);
        cptab->ctb_cpu2cpt[cpu] = -1;

        node = cpu_to_node(cpu);

        LASSERT(node_isset(node, *cptab->ctb_parts[cpt].cpt_nodemask));
        LASSERT(node_isset(node, *cptab->ctb_nodemask));

        for_each_cpu_mask(i, *cptab->ctb_parts[cpt].cpt_cpumask) {
                /* this CPT has other CPU belonging to this node? */
                if (cpu_to_node(i) == node)
                        break;
        }

        if (i == NR_CPUS)
                node_clear(node, *cptab->ctb_parts[cpt].cpt_nodemask);

        for_each_cpu_mask(i, *cptab->ctb_cpumask) {
                /* this CPT-table has other CPU belonging to this node? */
                if (cpu_to_node(i) == node)
                        break;
        }

        if (i == NR_CPUS)
                node_clear(node, *cptab->ctb_nodemask);

        return;
}
EXPORT_SYMBOL(cfs_cpt_unset_cpu);

int
cfs_cpt_set_cpumask(struct cfs_cpt_table *cptab, int cpt, cpumask_t *mask)
{
        int     i;

        if (cpus_weight(*mask) == 0 || any_online_cpu(*mask) == NR_CPUS) {
                CDEBUG(D_INFO, "No online CPU is found in the CPU mask for CPU partition %d\n",
                       cpt);
                return 0;
        }

        for_each_cpu_mask(i, *mask) {
                if (!cfs_cpt_set_cpu(cptab, cpt, i))
                        return 0;
        }

        return 1;
}
EXPORT_SYMBOL(cfs_cpt_set_cpumask);

void
cfs_cpt_unset_cpumask(struct cfs_cpt_table *cptab, int cpt, cpumask_t *mask)
{
        int     i;

        for_each_cpu_mask(i, *mask)
                cfs_cpt_unset_cpu(cptab, cpt, i);
}
EXPORT_SYMBOL(cfs_cpt_unset_cpumask);

int
cfs_cpt_set_node(struct cfs_cpt_table *cptab, int cpt, int node)
{
        cpumask_t       *mask;
        int             rc;

        if (node < 0 || node >= MAX_NUMNODES) {
                CDEBUG(D_INFO,
                       "Invalid NUMA id %d for CPU partition %d\n", node, cpt);
                return 0;
        }

        mutex_lock(&cpt_data.cpt_mutex);

        mask = cpt_data.cpt_cpumask;
        cfs_node_to_cpumask(node, mask);

        rc = cfs_cpt_set_cpumask(cptab, cpt, mask);

        mutex_unlock(&cpt_data.cpt_mutex);

        return rc;
}
EXPORT_SYMBOL(cfs_cpt_set_node);

void
cfs_cpt_unset_node(struct cfs_cpt_table *cptab, int cpt, int node)
{
        cpumask_t *mask;

        if (node < 0 || node >= MAX_NUMNODES) {
                CDEBUG(D_INFO,
                       "Invalid NUMA id %d for CPU partition %d\n", node, cpt);
                return;
        }

        mutex_lock(&cpt_data.cpt_mutex);

        mask = cpt_data.cpt_cpumask;
        cfs_node_to_cpumask(node, mask);

        cfs_cpt_unset_cpumask(cptab, cpt, mask);

        mutex_unlock(&cpt_data.cpt_mutex);
}
EXPORT_SYMBOL(cfs_cpt_unset_node);

int
cfs_cpt_set_nodemask(struct cfs_cpt_table *cptab, int cpt, nodemask_t *mask)
{
        int     i;

        for_each_node_mask(i, *mask) {
                if (!cfs_cpt_set_node(cptab, cpt, i))
                        return 0;
        }

        return 1;
}
EXPORT_SYMBOL(cfs_cpt_set_nodemask);

void
cfs_cpt_unset_nodemask(struct cfs_cpt_table *cptab, int cpt, nodemask_t *mask)
{
        int     i;

        for_each_node_mask(i, *mask)
                cfs_cpt_unset_node(cptab, cpt, i);
}
EXPORT_SYMBOL(cfs_cpt_unset_nodemask);

void
cfs_cpt_clear(struct cfs_cpt_table *cptab, int cpt)
{
        int     last;
        int     i;

        if (cpt == CFS_CPT_ANY) {
                last = cptab->ctb_nparts - 1;
                cpt = 0;
        } else {
                last = cpt;
        }

        for (; cpt <= last; cpt++) {
                for_each_cpu_mask(i, *cptab->ctb_parts[cpt].cpt_cpumask)
                        cfs_cpt_unset_cpu(cptab, cpt, i);
        }
}
EXPORT_SYMBOL(cfs_cpt_clear);

int
cfs_cpt_spread_node(struct cfs_cpt_table *cptab, int cpt)
{
        nodemask_t      *mask;
        int             weight;
        int             rotor;
        int             node;

        /* convert CPU partition ID to HW node id */

        if (cpt < 0 || cpt >= cptab->ctb_nparts) {
                mask = cptab->ctb_nodemask;
                rotor = cptab->ctb_spread_rotor++;
        } else {
                mask = cptab->ctb_parts[cpt].cpt_nodemask;
                rotor = cptab->ctb_parts[cpt].cpt_spread_rotor++;
        }

        weight = nodes_weight(*mask);
        LASSERT(weight > 0);

        rotor %= weight;

        for_each_node_mask(node, *mask) {
                if (rotor-- == 0)
                        return node;
        }

        LBUG();
        return 0;
}
EXPORT_SYMBOL(cfs_cpt_spread_node);

int
cfs_cpt_current(struct cfs_cpt_table *cptab, int remap)
{
        int     cpu = smp_processor_id();
        int     cpt = cptab->ctb_cpu2cpt[cpu];

        if (cpt < 0) {
                if (!remap)
                        return cpt;

                /* don't return negative value for safety of upper layer,
                 * instead we shadow the unknown cpu to a valid partition ID */
                cpt = cpu % cptab->ctb_nparts;
        }

        return cpt;
}
EXPORT_SYMBOL(cfs_cpt_current);

int
cfs_cpt_of_cpu(struct cfs_cpt_table *cptab, int cpu)
{
        LASSERT(cpu >= 0 && cpu < NR_CPUS);

        return cptab->ctb_cpu2cpt[cpu];
}
EXPORT_SYMBOL(cfs_cpt_of_cpu);

int
cfs_cpt_bind(struct cfs_cpt_table *cptab, int cpt)
{
        cpumask_t       *cpumask;
        nodemask_t      *nodemask;
        int             rc;
        int             i;

        LASSERT(cpt == CFS_CPT_ANY || (cpt >= 0 && cpt < cptab->ctb_nparts));

        if (cpt == CFS_CPT_ANY) {
                cpumask = cptab->ctb_cpumask;
                nodemask = cptab->ctb_nodemask;
        } else {
                cpumask = cptab->ctb_parts[cpt].cpt_cpumask;
                nodemask = cptab->ctb_parts[cpt].cpt_nodemask;
        }

        if (any_online_cpu(*cpumask) == NR_CPUS) {
                CERROR("No online CPU found in CPU partition %d, did someone do CPU hotplug on system? You might need to reload Lustre modules to keep system working well.\n",
                       cpt);
                return -EINVAL;
        }

        for_each_online_cpu(i) {
                if (cpu_isset(i, *cpumask))
                        continue;

                rc = set_cpus_allowed_ptr(current, cpumask);
                set_mems_allowed(*nodemask);
                if (rc == 0)
                        schedule(); /* switch to allowed CPU */

                return rc;
        }

        /* don't need to set affinity because all online CPUs are covered */
        return 0;
}
EXPORT_SYMBOL(cfs_cpt_bind);

/**
 * Choose max to \a number CPUs from \a node and set them in \a cpt.
 * We always prefer to choose CPU in the same core/socket.
 */
static int
cfs_cpt_choose_ncpus(struct cfs_cpt_table *cptab, int cpt,
                     cpumask_t *node, int number)
{
        cpumask_t       *socket = NULL;
        cpumask_t       *core = NULL;
        int             rc = 0;
        int             cpu;

        LASSERT(number > 0);

        if (number >= cpus_weight(*node)) {
                while (!cpus_empty(*node)) {
                        cpu = first_cpu(*node);

                        rc = cfs_cpt_set_cpu(cptab, cpt, cpu);
                        if (!rc)
                                return -EINVAL;
                        cpu_clear(cpu, *node);
                }
                return 0;
        }

        /* allocate scratch buffer */
        LIBCFS_ALLOC(socket, cpumask_size());
        LIBCFS_ALLOC(core, cpumask_size());
        if (socket == NULL || core == NULL) {
                rc = -ENOMEM;
                goto out;
        }

        while (!cpus_empty(*node)) {
                cpu = first_cpu(*node);

                /* get cpumask for cores in the same socket */
                cfs_cpu_core_siblings(cpu, socket);
                cpus_and(*socket, *socket, *node);

                LASSERT(!cpus_empty(*socket));

                while (!cpus_empty(*socket)) {
                        int     i;

                        /* get cpumask for hts in the same core */
                        cfs_cpu_ht_siblings(cpu, core);
                        cpus_and(*core, *core, *node);

                        LASSERT(!cpus_empty(*core));

                        for_each_cpu_mask(i, *core) {
                                cpu_clear(i, *socket);
                                cpu_clear(i, *node);

                                rc = cfs_cpt_set_cpu(cptab, cpt, i);
                                if (!rc) {
                                        rc = -EINVAL;
                                        goto out;
                                }

                                if (--number == 0)
                                        goto out;
                        }
                        cpu = first_cpu(*socket);
                }
        }

 out:
        if (socket != NULL)
                LIBCFS_FREE(socket, cpumask_size());
        if (core != NULL)
                LIBCFS_FREE(core, cpumask_size());
        return rc;
}

#define CPT_WEIGHT_MIN  4u

static unsigned int
cfs_cpt_num_estimate(void)
{
        unsigned nnode = num_online_nodes();
        unsigned ncpu  = num_online_cpus();
        unsigned ncpt;

        if (ncpu <= CPT_WEIGHT_MIN) {
                ncpt = 1;
                goto out;
        }

        /* generate reasonable number of CPU partitions based on total number
         * of CPUs, Preferred N should be power2 and match this condition:
         * 2 * (N - 1)^2 < NCPUS <= 2 * N^2 */
        for (ncpt = 2; ncpu > 2 * ncpt * ncpt; ncpt <<= 1) {}

        if (ncpt <= nnode) { /* fat numa system */
                while (nnode > ncpt)
                        nnode >>= 1;

        } else { /* ncpt > nnode */
                while ((nnode << 1) <= ncpt)
                        nnode <<= 1;
        }

        ncpt = nnode;

 out:
#if (BITS_PER_LONG == 32)
        /* config many CPU partitions on 32-bit system could consume
         * too much memory */
        ncpt = min(2U, ncpt);
#endif
        while (ncpu % ncpt != 0)
                ncpt--; /* worst case is 1 */

        return ncpt;
}

static struct cfs_cpt_table *
cfs_cpt_table_create(int ncpt)
{
        struct cfs_cpt_table *cptab = NULL;
        cpumask_t       *mask = NULL;
        int             cpt = 0;
        int             num;
        int             rc;
        int             i;

        rc = cfs_cpt_num_estimate();
        if (ncpt <= 0)
                ncpt = rc;

        if (ncpt > num_online_cpus() || ncpt > 4 * rc) {
                CWARN("CPU partition number %d is larger than suggested value (%d), your system may have performance issue or run out of memory while under pressure\n",
                      ncpt, rc);
        }

        if (num_online_cpus() % ncpt != 0) {
                CERROR("CPU number %d is not multiple of cpu_npartition %d, please try different cpu_npartitions value or set pattern string by cpu_pattern=STRING\n",
                       (int)num_online_cpus(), ncpt);
                goto failed;
        }

        cptab = cfs_cpt_table_alloc(ncpt);
        if (cptab == NULL) {
                CERROR("Failed to allocate CPU map(%d)\n", ncpt);
                goto failed;
        }

        num = num_online_cpus() / ncpt;
        if (num == 0) {
                CERROR("CPU changed while setting CPU partition\n");
                goto failed;
        }

        LIBCFS_ALLOC(mask, cpumask_size());
        if (mask == NULL) {
                CERROR("Failed to allocate scratch cpumask\n");
                goto failed;
        }

        for_each_online_node(i) {
                cfs_node_to_cpumask(i, mask);

                while (!cpus_empty(*mask)) {
                        struct cfs_cpu_partition *part;
                        int    n;

                        if (cpt >= ncpt)
                                goto failed;

                        part = &cptab->ctb_parts[cpt];

                        n = num - cpus_weight(*part->cpt_cpumask);
                        LASSERT(n > 0);

                        rc = cfs_cpt_choose_ncpus(cptab, cpt, mask, n);
                        if (rc < 0)
                                goto failed;

                        LASSERT(num >= cpus_weight(*part->cpt_cpumask));
                        if (num == cpus_weight(*part->cpt_cpumask))
                                cpt++;
                }
        }

        if (cpt != ncpt ||
            num != cpus_weight(*cptab->ctb_parts[ncpt - 1].cpt_cpumask)) {
                CERROR("Expect %d(%d) CPU partitions but got %d(%d), CPU hotplug/unplug while setting?\n",
                       cptab->ctb_nparts, num, cpt,
                       cpus_weight(*cptab->ctb_parts[ncpt - 1].cpt_cpumask));
                goto failed;
        }

        LIBCFS_FREE(mask, cpumask_size());

        return cptab;

 failed:
        CERROR("Failed to setup CPU-partition-table with %d CPU-partitions, online HW nodes: %d, HW cpus: %d.\n",
               ncpt, num_online_nodes(), num_online_cpus());

        if (mask != NULL)
                LIBCFS_FREE(mask, cpumask_size());

        if (cptab != NULL)
                cfs_cpt_table_free(cptab);

        return NULL;
}

static struct cfs_cpt_table *
cfs_cpt_table_create_pattern(char *pattern)
{
        struct cfs_cpt_table    *cptab;
        char                    *str    = pattern;
        int                     node    = 0;
        int                     high;
        int                     ncpt;
        int                     c;

        for (ncpt = 0;; ncpt++) { /* quick scan bracket */
                str = strchr(str, '[');
                if (str == NULL)
                        break;
                str++;
        }

        str = cfs_trimwhite(pattern);
        if (*str == 'n' || *str == 'N') {
                pattern = str + 1;
                node = 1;
        }

        if (ncpt == 0 ||
            (node && ncpt > num_online_nodes()) ||
            (!node && ncpt > num_online_cpus())) {
                CERROR("Invalid pattern %s, or too many partitions %d\n",
                       pattern, ncpt);
                return NULL;
        }

        high = node ? MAX_NUMNODES - 1 : NR_CPUS - 1;

        cptab = cfs_cpt_table_alloc(ncpt);
        if (cptab == NULL) {
                CERROR("Failed to allocate cpu partition table\n");
                return NULL;
        }

        for (str = cfs_trimwhite(pattern), c = 0;; c++) {
                struct cfs_range_expr   *range;
                struct cfs_expr_list    *el;
                char                    *bracket = strchr(str, '[');
                int                     cpt;
                int                     rc;
                int                     i;
                int                     n;

                if (bracket == NULL) {
                        if (*str != 0) {
                                CERROR("Invalid pattern %s\n", str);
                                goto failed;
                        } else if (c != ncpt) {
                                CERROR("expect %d partitions but found %d\n",
                                       ncpt, c);
                                goto failed;
                        }
                        break;
                }

                if (sscanf(str, "%d%n", &cpt, &n) < 1) {
                        CERROR("Invalid cpu pattern %s\n", str);
                        goto failed;
                }

                if (cpt < 0 || cpt >= ncpt) {
                        CERROR("Invalid partition id %d, total partitions %d\n",
                               cpt, ncpt);
                        goto failed;
                }

                if (cfs_cpt_weight(cptab, cpt) != 0) {
                        CERROR("Partition %d has already been set.\n", cpt);
                        goto failed;
                }

                str = cfs_trimwhite(str + n);
                if (str != bracket) {
                        CERROR("Invalid pattern %s\n", str);
                        goto failed;
                }

                bracket = strchr(str, ']');
                if (bracket == NULL) {
                        CERROR("missing right bracket for cpt %d, %s\n",
                               cpt, str);
                        goto failed;
                }

                if (cfs_expr_list_parse(str, (bracket - str) + 1,
                                        0, high, &el) != 0) {
                        CERROR("Can't parse number range: %s\n", str);
                        goto failed;
                }

                list_for_each_entry(range, &el->el_exprs, re_link) {
                        for (i = range->re_lo; i <= range->re_hi; i++) {
                                if ((i - range->re_lo) % range->re_stride != 0)
                                        continue;

                                rc = node ? cfs_cpt_set_node(cptab, cpt, i) :
                                            cfs_cpt_set_cpu(cptab, cpt, i);
                                if (!rc) {
                                        cfs_expr_list_free(el);
                                        goto failed;
                                }
                        }
                }

                cfs_expr_list_free(el);

                if (!cfs_cpt_online(cptab, cpt)) {
                        CERROR("No online CPU is found on partition %d\n", cpt);
                        goto failed;
                }

                str = cfs_trimwhite(bracket + 1);
        }

        return cptab;

 failed:
        cfs_cpt_table_free(cptab);
        return NULL;
}

#ifdef CONFIG_HOTPLUG_CPU
static int
cfs_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu)
{
        unsigned int  cpu = (unsigned long)hcpu;
        bool         warn;

        switch (action) {
        case CPU_DEAD:
        case CPU_DEAD_FROZEN:
        case CPU_ONLINE:
        case CPU_ONLINE_FROZEN:
                spin_lock(&cpt_data.cpt_lock);
                cpt_data.cpt_version++;
                spin_unlock(&cpt_data.cpt_lock);
        default:
                if (action != CPU_DEAD && action != CPU_DEAD_FROZEN) {
                        CDEBUG(D_INFO, "CPU changed [cpu %u action %lx]\n",
                               cpu, action);
                        break;
                }

                mutex_lock(&cpt_data.cpt_mutex);
                /* if all HTs in a core are offline, it may break affinity */
                cfs_cpu_ht_siblings(cpu, cpt_data.cpt_cpumask);
                warn = any_online_cpu(*cpt_data.cpt_cpumask) >= nr_cpu_ids;
                mutex_unlock(&cpt_data.cpt_mutex);
                CDEBUG(warn ? D_WARNING : D_INFO,
                       "Lustre: can't support CPU plug-out well now, performance and stability could be impacted [CPU %u action: %lx]\n",
                       cpu, action);
        }

        return NOTIFY_OK;
}

static struct notifier_block cfs_cpu_notifier = {
        .notifier_call  = cfs_cpu_notify,
        .priority       = 0
};

#endif

void
cfs_cpu_fini(void)
{
        if (cfs_cpt_table != NULL)
                cfs_cpt_table_free(cfs_cpt_table);

#ifdef CONFIG_HOTPLUG_CPU
        unregister_hotcpu_notifier(&cfs_cpu_notifier);
#endif
        if (cpt_data.cpt_cpumask != NULL)
                LIBCFS_FREE(cpt_data.cpt_cpumask, cpumask_size());
}

int
cfs_cpu_init(void)
{

        LASSERT(cfs_cpt_table == NULL);

        memset(&cpt_data, 0, sizeof(cpt_data));

        LIBCFS_ALLOC(cpt_data.cpt_cpumask, cpumask_size());
        if (cpt_data.cpt_cpumask == NULL) {
                CERROR("Failed to allocate scratch buffer\n");
                return -1;
        }

        spin_lock_init(&cpt_data.cpt_lock);
        mutex_init(&cpt_data.cpt_mutex);

#ifdef CONFIG_HOTPLUG_CPU
        register_hotcpu_notifier(&cfs_cpu_notifier);
#endif

        if (*cpu_pattern != 0) {
                cfs_cpt_table = cfs_cpt_table_create_pattern(cpu_pattern);
                if (cfs_cpt_table == NULL) {
                        CERROR("Failed to create cptab from pattern %s\n",
                               cpu_pattern);
                        goto failed;
                }

        } else {
                cfs_cpt_table = cfs_cpt_table_create(cpu_npartitions);
                if (cfs_cpt_table == NULL) {
                        CERROR("Failed to create ptable with npartitions %d\n",
                               cpu_npartitions);
                        goto failed;
                }
        }

        spin_lock(&cpt_data.cpt_lock);
        if (cfs_cpt_table->ctb_version != cpt_data.cpt_version) {
                spin_unlock(&cpt_data.cpt_lock);
                CERROR("CPU hotplug/unplug during setup\n");
                goto failed;
        }
        spin_unlock(&cpt_data.cpt_lock);

        LCONSOLE(0, "HW CPU cores: %d, npartitions: %d\n",
                 num_online_cpus(), cfs_cpt_number(cfs_cpt_table));
        return 0;

 failed:
        cfs_cpu_fini();
        return -1;
}

#endif