/*
 * Collaborative memory management interface.
 *
 * Copyright (C) 2008 IBM Corporation
 * Author(s): Brian King (brking@linux.vnet.ibm.com),
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * 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 for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 */

#include <linux/ctype.h>
#include <linux/delay.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/gfp.h>
#include <linux/kthread.h>
#include <linux/module.h>
#include <linux/oom.h>
#include <linux/reboot.h>
#include <linux/sched.h>
#include <linux/stringify.h>
#include <linux/swap.h>
#include <linux/device.h>
#include <asm/firmware.h>
#include <asm/hvcall.h>
#include <asm/mmu.h>
#include <asm/pgalloc.h>
#include <asm/uaccess.h>
#include <linux/memory.h>
#include <asm/plpar_wrappers.h>

#define CMM_DRIVER_VERSION      "1.0.0"
#define CMM_DEFAULT_DELAY       1
#define CMM_HOTPLUG_DELAY       5
#define CMM_DEBUG                       0
#define CMM_DISABLE             0
#define CMM_OOM_KB              1024
#define CMM_MIN_MEM_MB          256
#define KB2PAGES(_p)            ((_p)>>(PAGE_SHIFT-10))
#define PAGES2KB(_p)            ((_p)<<(PAGE_SHIFT-10))
/*
 * The priority level tries to ensure that this notifier is called as
 * late as possible to reduce thrashing in the shared memory pool.
 */
#define CMM_MEM_HOTPLUG_PRI     1
#define CMM_MEM_ISOLATE_PRI     15

static unsigned int delay = CMM_DEFAULT_DELAY;
static unsigned int hotplug_delay = CMM_HOTPLUG_DELAY;
static unsigned int oom_kb = CMM_OOM_KB;
static unsigned int cmm_debug = CMM_DEBUG;
static unsigned int cmm_disabled = CMM_DISABLE;
static unsigned long min_mem_mb = CMM_MIN_MEM_MB;
static struct device cmm_dev;

MODULE_AUTHOR("Brian King <brking@linux.vnet.ibm.com>");
MODULE_DESCRIPTION("IBM System p Collaborative Memory Manager");
MODULE_LICENSE("GPL");
MODULE_VERSION(CMM_DRIVER_VERSION);

module_param_named(delay, delay, uint, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(delay, "Delay (in seconds) between polls to query hypervisor paging requests. "
                 "[Default=" __stringify(CMM_DEFAULT_DELAY) "]");
module_param_named(hotplug_delay, hotplug_delay, uint, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(delay, "Delay (in seconds) after memory hotplug remove "
                 "before loaning resumes. "
                 "[Default=" __stringify(CMM_HOTPLUG_DELAY) "]");
module_param_named(oom_kb, oom_kb, uint, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(oom_kb, "Amount of memory in kb to free on OOM. "
                 "[Default=" __stringify(CMM_OOM_KB) "]");
module_param_named(min_mem_mb, min_mem_mb, ulong, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(min_mem_mb, "Minimum amount of memory (in MB) to not balloon. "
                 "[Default=" __stringify(CMM_MIN_MEM_MB) "]");
module_param_named(debug, cmm_debug, uint, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(debug, "Enable module debugging logging. Set to 1 to enable. "
                 "[Default=" __stringify(CMM_DEBUG) "]");

#define CMM_NR_PAGES ((PAGE_SIZE - sizeof(void *) - sizeof(unsigned long)) / sizeof(unsigned long))

#define cmm_dbg(...) if (cmm_debug) { printk(KERN_INFO "cmm: "__VA_ARGS__); }

struct cmm_page_array {
        struct cmm_page_array *next;
        unsigned long index;
        unsigned long page[CMM_NR_PAGES];
};

static unsigned long loaned_pages;
static unsigned long loaned_pages_target;
static unsigned long oom_freed_pages;

static struct cmm_page_array *cmm_page_list;
static DEFINE_SPINLOCK(cmm_lock);

static DEFINE_MUTEX(hotplug_mutex);
static int hotplug_occurred; /* protected by the hotplug mutex */

static struct task_struct *cmm_thread_ptr;

/**
 * cmm_alloc_pages - Allocate pages and mark them as loaned
 * @nr: number of pages to allocate
 *
 * Return value:
 *      number of pages requested to be allocated which were not
 **/
static long cmm_alloc_pages(long nr)
{
        struct cmm_page_array *pa, *npa;
        unsigned long addr;
        long rc;

        cmm_dbg("Begin request for %ld pages\n", nr);

        while (nr) {
                /* Exit if a hotplug operation is in progress or occurred */
                if (mutex_trylock(&hotplug_mutex)) {
                        if (hotplug_occurred) {
                                mutex_unlock(&hotplug_mutex);
                                break;
                        }
                        mutex_unlock(&hotplug_mutex);
                } else {
                        break;
                }

                addr = __get_free_page(GFP_NOIO | __GFP_NOWARN |
                                       __GFP_NORETRY | __GFP_NOMEMALLOC);
                if (!addr)
                        break;
                spin_lock(&cmm_lock);
                pa = cmm_page_list;
                if (!pa || pa->index >= CMM_NR_PAGES) {
                        /* Need a new page for the page list. */
                        spin_unlock(&cmm_lock);
                        npa = (struct cmm_page_array *)__get_free_page(
                                        GFP_NOIO | __GFP_NOWARN |
                                        __GFP_NORETRY | __GFP_NOMEMALLOC);
                        if (!npa) {
                                pr_info("%s: Can not allocate new page list\n", __func__);
                                free_page(addr);
                                break;
                        }
                        spin_lock(&cmm_lock);
                        pa = cmm_page_list;

                        if (!pa || pa->index >= CMM_NR_PAGES) {
                                npa->next = pa;
                                npa->index = 0;
                                pa = npa;
                                cmm_page_list = pa;
                        } else
                                free_page((unsigned long) npa);
                }

                if ((rc = plpar_page_set_loaned(__pa(addr)))) {
                        pr_err("%s: Can not set page to loaned. rc=%ld\n", __func__, rc);
                        spin_unlock(&cmm_lock);
                        free_page(addr);
                        break;
                }

                pa->page[pa->index++] = addr;
                loaned_pages++;
                totalram_pages--;
                spin_unlock(&cmm_lock);
                nr--;
        }

        cmm_dbg("End request with %ld pages unfulfilled\n", nr);
        return nr;
}

/**
 * cmm_free_pages - Free pages and mark them as active
 * @nr: number of pages to free
 *
 * Return value:
 *      number of pages requested to be freed which were not
 **/
static long cmm_free_pages(long nr)
{
        struct cmm_page_array *pa;
        unsigned long addr;

        cmm_dbg("Begin free of %ld pages.\n", nr);
        spin_lock(&cmm_lock);
        pa = cmm_page_list;
        while (nr) {
                if (!pa || pa->index <= 0)
                        break;
                addr = pa->page[--pa->index];

                if (pa->index == 0) {
                        pa = pa->next;
                        free_page((unsigned long) cmm_page_list);
                        cmm_page_list = pa;
                }

                plpar_page_set_active(__pa(addr));
                free_page(addr);
                loaned_pages--;
                nr--;
                totalram_pages++;
        }
        spin_unlock(&cmm_lock);
        cmm_dbg("End request with %ld pages unfulfilled\n", nr);
        return nr;
}

/**
 * cmm_oom_notify - OOM notifier
 * @self:       notifier block struct
 * @dummy:      not used
 * @parm:       returned - number of pages freed
 *
 * Return value:
 *      NOTIFY_OK
 **/
static int cmm_oom_notify(struct notifier_block *self,
                          unsigned long dummy, void *parm)
{
        unsigned long *freed = parm;
        long nr = KB2PAGES(oom_kb);

        cmm_dbg("OOM processing started\n");
        nr = cmm_free_pages(nr);
        loaned_pages_target = loaned_pages;
        *freed += KB2PAGES(oom_kb) - nr;
        oom_freed_pages += KB2PAGES(oom_kb) - nr;
        cmm_dbg("OOM processing complete\n");
        return NOTIFY_OK;
}

/**
 * cmm_get_mpp - Read memory performance parameters
 *
 * Makes hcall to query the current page loan request from the hypervisor.
 *
 * Return value:
 *      nothing
 **/
static void cmm_get_mpp(void)
{
        int rc;
        struct hvcall_mpp_data mpp_data;
        signed long active_pages_target, page_loan_request, target;
        signed long total_pages = totalram_pages + loaned_pages;
        signed long min_mem_pages = (min_mem_mb * 1024 * 1024) / PAGE_SIZE;

        rc = h_get_mpp(&mpp_data);

        if (rc != H_SUCCESS)
                return;

        page_loan_request = div_s64((s64)mpp_data.loan_request, PAGE_SIZE);
        target = page_loan_request + (signed long)loaned_pages;

        if (target < 0 || total_pages < min_mem_pages)
                target = 0;

        if (target > oom_freed_pages)
                target -= oom_freed_pages;
        else
                target = 0;

        active_pages_target = total_pages - target;

        if (min_mem_pages > active_pages_target)
                target = total_pages - min_mem_pages;

        if (target < 0)
                target = 0;

        loaned_pages_target = target;

        cmm_dbg("delta = %ld, loaned = %lu, target = %lu, oom = %lu, totalram = %lu\n",
                page_loan_request, loaned_pages, loaned_pages_target,
                oom_freed_pages, totalram_pages);
}

static struct notifier_block cmm_oom_nb = {
        .notifier_call = cmm_oom_notify
};

/**
 * cmm_thread - CMM task thread
 * @dummy:      not used
 *
 * Return value:
 *      0
 **/
static int cmm_thread(void *dummy)
{
        unsigned long timeleft;

        while (1) {
                timeleft = msleep_interruptible(delay * 1000);

                if (kthread_should_stop() || timeleft)
                        break;

                if (mutex_trylock(&hotplug_mutex)) {
                        if (hotplug_occurred) {
                                hotplug_occurred = 0;
                                mutex_unlock(&hotplug_mutex);
                                cmm_dbg("Hotplug operation has occurred, "
                                                "loaning activity suspended "
                                                "for %d seconds.\n",
                                                hotplug_delay);
                                timeleft = msleep_interruptible(hotplug_delay *
                                                1000);
                                if (kthread_should_stop() || timeleft)
                                        break;
                                continue;
                        }
                        mutex_unlock(&hotplug_mutex);
                } else {
                        cmm_dbg("Hotplug operation in progress, activity "
                                        "suspended\n");
                        continue;
                }

                cmm_get_mpp();

                if (loaned_pages_target > loaned_pages) {
                        if (cmm_alloc_pages(loaned_pages_target - loaned_pages))
                                loaned_pages_target = loaned_pages;
                } else if (loaned_pages_target < loaned_pages)
                        cmm_free_pages(loaned_pages - loaned_pages_target);
        }
        return 0;
}

#define CMM_SHOW(name, format, args...)                 \
        static ssize_t show_##name(struct device *dev,  \
                                   struct device_attribute *attr,       \
                                   char *buf)                   \
        {                                                       \
                return sprintf(buf, format, ##args);            \
        }                                                       \
        static DEVICE_ATTR(name, S_IRUGO, show_##name, NULL)

CMM_SHOW(loaned_kb, "%lu\n", PAGES2KB(loaned_pages));
CMM_SHOW(loaned_target_kb, "%lu\n", PAGES2KB(loaned_pages_target));

static ssize_t show_oom_pages(struct device *dev,
                              struct device_attribute *attr, char *buf)
{
        return sprintf(buf, "%lu\n", PAGES2KB(oom_freed_pages));
}

static ssize_t store_oom_pages(struct device *dev,
                               struct device_attribute *attr,
                               const char *buf, size_t count)
{
        unsigned long val = simple_strtoul (buf, NULL, 10);

        if (!capable(CAP_SYS_ADMIN))
                return -EPERM;
        if (val != 0)
                return -EBADMSG;

        oom_freed_pages = 0;
        return count;
}

static DEVICE_ATTR(oom_freed_kb, S_IWUSR | S_IRUGO,
                   show_oom_pages, store_oom_pages);

static struct device_attribute *cmm_attrs[] = {
        &dev_attr_loaned_kb,
        &dev_attr_loaned_target_kb,
        &dev_attr_oom_freed_kb,
};

static struct bus_type cmm_subsys = {
        .name = "cmm",
        .dev_name = "cmm",
};

/**
 * cmm_sysfs_register - Register with sysfs
 *
 * Return value:
 *      0 on success / other on failure
 **/
static int cmm_sysfs_register(struct device *dev)
{
        int i, rc;

        if ((rc = subsys_system_register(&cmm_subsys, NULL)))
                return rc;

        dev->id = 0;
        dev->bus = &cmm_subsys;

        if ((rc = device_register(dev)))
                goto subsys_unregister;

        for (i = 0; i < ARRAY_SIZE(cmm_attrs); i++) {
                if ((rc = device_create_file(dev, cmm_attrs[i])))
                        goto fail;
        }

        return 0;

fail:
        while (--i >= 0)
                device_remove_file(dev, cmm_attrs[i]);
        device_unregister(dev);
subsys_unregister:
        bus_unregister(&cmm_subsys);
        return rc;
}

/**
 * cmm_unregister_sysfs - Unregister from sysfs
 *
 **/
static void cmm_unregister_sysfs(struct device *dev)
{
        int i;

        for (i = 0; i < ARRAY_SIZE(cmm_attrs); i++)
                device_remove_file(dev, cmm_attrs[i]);
        device_unregister(dev);
        bus_unregister(&cmm_subsys);
}

/**
 * cmm_reboot_notifier - Make sure pages are not still marked as "loaned"
 *
 **/
static int cmm_reboot_notifier(struct notifier_block *nb,
                               unsigned long action, void *unused)
{
        if (action == SYS_RESTART) {
                if (cmm_thread_ptr)
                        kthread_stop(cmm_thread_ptr);
                cmm_thread_ptr = NULL;
                cmm_free_pages(loaned_pages);
        }
        return NOTIFY_DONE;
}

static struct notifier_block cmm_reboot_nb = {
        .notifier_call = cmm_reboot_notifier,
};

/**
 * cmm_count_pages - Count the number of pages loaned in a particular range.
 *
 * @arg: memory_isolate_notify structure with address range and count
 *
 * Return value:
 *      0 on success
 **/
static unsigned long cmm_count_pages(void *arg)
{
        struct memory_isolate_notify *marg = arg;
        struct cmm_page_array *pa;
        unsigned long start = (unsigned long)pfn_to_kaddr(marg->start_pfn);
        unsigned long end = start + (marg->nr_pages << PAGE_SHIFT);
        unsigned long idx;

        spin_lock(&cmm_lock);
        pa = cmm_page_list;
        while (pa) {
                if ((unsigned long)pa >= start && (unsigned long)pa < end)
                        marg->pages_found++;
                for (idx = 0; idx < pa->index; idx++)
                        if (pa->page[idx] >= start && pa->page[idx] < end)
                                marg->pages_found++;
                pa = pa->next;
        }
        spin_unlock(&cmm_lock);
        return 0;
}

/**
 * cmm_memory_isolate_cb - Handle memory isolation notifier calls
 * @self:       notifier block struct
 * @action:     action to take
 * @arg:        struct memory_isolate_notify data for handler
 *
 * Return value:
 *      NOTIFY_OK or notifier error based on subfunction return value
 **/
static int cmm_memory_isolate_cb(struct notifier_block *self,
                                 unsigned long action, void *arg)
{
        int ret = 0;

        if (action == MEM_ISOLATE_COUNT)
                ret = cmm_count_pages(arg);

        return notifier_from_errno(ret);
}

static struct notifier_block cmm_mem_isolate_nb = {
        .notifier_call = cmm_memory_isolate_cb,
        .priority = CMM_MEM_ISOLATE_PRI
};

/**
 * cmm_mem_going_offline - Unloan pages where memory is to be removed
 * @arg: memory_notify structure with page range to be offlined
 *
 * Return value:
 *      0 on success
 **/
static int cmm_mem_going_offline(void *arg)
{
        struct memory_notify *marg = arg;
        unsigned long start_page = (unsigned long)pfn_to_kaddr(marg->start_pfn);
        unsigned long end_page = start_page + (marg->nr_pages << PAGE_SHIFT);
        struct cmm_page_array *pa_curr, *pa_last, *npa;
        unsigned long idx;
        unsigned long freed = 0;

        cmm_dbg("Memory going offline, searching 0x%lx (%ld pages).\n",
                        start_page, marg->nr_pages);
        spin_lock(&cmm_lock);

        /* Search the page list for pages in the range to be offlined */
        pa_last = pa_curr = cmm_page_list;
        while (pa_curr) {
                for (idx = (pa_curr->index - 1); (idx + 1) > 0; idx--) {
                        if ((pa_curr->page[idx] < start_page) ||
                            (pa_curr->page[idx] >= end_page))
                                continue;

                        plpar_page_set_active(__pa(pa_curr->page[idx]));
                        free_page(pa_curr->page[idx]);
                        freed++;
                        loaned_pages--;
                        totalram_pages++;
                        pa_curr->page[idx] = pa_last->page[--pa_last->index];
                        if (pa_last->index == 0) {
                                if (pa_curr == pa_last)
                                        pa_curr = pa_last->next;
                                pa_last = pa_last->next;
                                free_page((unsigned long)cmm_page_list);
                                cmm_page_list = pa_last;
                        }
                }
                pa_curr = pa_curr->next;
        }

        /* Search for page list structures in the range to be offlined */
        pa_last = NULL;
        pa_curr = cmm_page_list;
        while (pa_curr) {
                if (((unsigned long)pa_curr >= start_page) &&
                                ((unsigned long)pa_curr < end_page)) {
                        npa = (struct cmm_page_array *)__get_free_page(
                                        GFP_NOIO | __GFP_NOWARN |
                                        __GFP_NORETRY | __GFP_NOMEMALLOC);
                        if (!npa) {
                                spin_unlock(&cmm_lock);
                                cmm_dbg("Failed to allocate memory for list "
                                                "management. Memory hotplug "
                                                "failed.\n");
                                return -ENOMEM;
                        }
                        memcpy(npa, pa_curr, PAGE_SIZE);
                        if (pa_curr == cmm_page_list)
                                cmm_page_list = npa;
                        if (pa_last)
                                pa_last->next = npa;
                        free_page((unsigned long) pa_curr);
                        freed++;
                        pa_curr = npa;
                }

                pa_last = pa_curr;
                pa_curr = pa_curr->next;
        }

        spin_unlock(&cmm_lock);
        cmm_dbg("Released %ld pages in the search range.\n", freed);

        return 0;
}

/**
 * cmm_memory_cb - Handle memory hotplug notifier calls
 * @self:       notifier block struct
 * @action:     action to take
 * @arg:        struct memory_notify data for handler
 *
 * Return value:
 *      NOTIFY_OK or notifier error based on subfunction return value
 *
 **/
static int cmm_memory_cb(struct notifier_block *self,
                        unsigned long action, void *arg)
{
        int ret = 0;

        switch (action) {
        case MEM_GOING_OFFLINE:
                mutex_lock(&hotplug_mutex);
                hotplug_occurred = 1;
                ret = cmm_mem_going_offline(arg);
                break;
        case MEM_OFFLINE:
        case MEM_CANCEL_OFFLINE:
                mutex_unlock(&hotplug_mutex);
                cmm_dbg("Memory offline operation complete.\n");
                break;
        case MEM_GOING_ONLINE:
        case MEM_ONLINE:
        case MEM_CANCEL_ONLINE:
                break;
        }

        return notifier_from_errno(ret);
}

static struct notifier_block cmm_mem_nb = {
        .notifier_call = cmm_memory_cb,
        .priority = CMM_MEM_HOTPLUG_PRI
};

/**
 * cmm_init - Module initialization
 *
 * Return value:
 *      0 on success / other on failure
 **/
static int cmm_init(void)
{
        int rc = -ENOMEM;

        if (!firmware_has_feature(FW_FEATURE_CMO))
                return -EOPNOTSUPP;

        if ((rc = register_oom_notifier(&cmm_oom_nb)) < 0)
                return rc;

        if ((rc = register_reboot_notifier(&cmm_reboot_nb)))
                goto out_oom_notifier;

        if ((rc = cmm_sysfs_register(&cmm_dev)))
                goto out_reboot_notifier;

        if (register_memory_notifier(&cmm_mem_nb) ||
            register_memory_isolate_notifier(&cmm_mem_isolate_nb))
                goto out_unregister_notifier;

        if (cmm_disabled)
                return rc;

        cmm_thread_ptr = kthread_run(cmm_thread, NULL, "cmmthread");
        if (IS_ERR(cmm_thread_ptr)) {
                rc = PTR_ERR(cmm_thread_ptr);
                goto out_unregister_notifier;
        }

        return rc;

out_unregister_notifier:
        unregister_memory_notifier(&cmm_mem_nb);
        unregister_memory_isolate_notifier(&cmm_mem_isolate_nb);
        cmm_unregister_sysfs(&cmm_dev);
out_reboot_notifier:
        unregister_reboot_notifier(&cmm_reboot_nb);
out_oom_notifier:
        unregister_oom_notifier(&cmm_oom_nb);
        return rc;
}

/**
 * cmm_exit - Module exit
 *
 * Return value:
 *      nothing
 **/
static void cmm_exit(void)
{
        if (cmm_thread_ptr)
                kthread_stop(cmm_thread_ptr);
        unregister_oom_notifier(&cmm_oom_nb);
        unregister_reboot_notifier(&cmm_reboot_nb);
        unregister_memory_notifier(&cmm_mem_nb);
        unregister_memory_isolate_notifier(&cmm_mem_isolate_nb);
        cmm_free_pages(loaned_pages);
        cmm_unregister_sysfs(&cmm_dev);
}

/**
 * cmm_set_disable - Disable/Enable CMM
 *
 * Return value:
 *      0 on success / other on failure
 **/
static int cmm_set_disable(const char *val, struct kernel_param *kp)
{
        int disable = simple_strtoul(val, NULL, 10);

        if (disable != 0 && disable != 1)
                return -EINVAL;

        if (disable && !cmm_disabled) {
                if (cmm_thread_ptr)
                        kthread_stop(cmm_thread_ptr);
                cmm_thread_ptr = NULL;
                cmm_free_pages(loaned_pages);
        } else if (!disable && cmm_disabled) {
                cmm_thread_ptr = kthread_run(cmm_thread, NULL, "cmmthread");
                if (IS_ERR(cmm_thread_ptr))
                        return PTR_ERR(cmm_thread_ptr);
        }

        cmm_disabled = disable;
        return 0;
}

module_param_call(disable, cmm_set_disable, param_get_uint,
                  &cmm_disabled, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(disable, "Disable CMM. Set to 1 to disable. "
                 "[Default=" __stringify(CMM_DISABLE) "]");

module_init(cmm_init);
module_exit(cmm_exit);