/*
 *
 * Copyright IBM Corporation, 2012
 * Author Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of version 2.1 of the GNU Lesser General Public License
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 *
 */

#include <linux/cgroup.h>
#include <linux/page_counter.h>
#include <linux/slab.h>
#include <linux/hugetlb.h>
#include <linux/hugetlb_cgroup.h>

struct hugetlb_cgroup {
        struct cgroup_subsys_state css;
        /*
         * the counter to account for hugepages from hugetlb.
         */
        struct page_counter hugepage[HUGE_MAX_HSTATE];
};

#define MEMFILE_PRIVATE(x, val) (((x) << 16) | (val))
#define MEMFILE_IDX(val)        (((val) >> 16) & 0xffff)
#define MEMFILE_ATTR(val)       ((val) & 0xffff)

struct cgroup_subsys hugetlb_subsys __read_mostly;
static struct hugetlb_cgroup *root_h_cgroup __read_mostly;

static inline
struct hugetlb_cgroup *hugetlb_cgroup_from_css(struct cgroup_subsys_state *s)
{
        return container_of(s, struct hugetlb_cgroup, css);
}

static inline
struct hugetlb_cgroup *hugetlb_cgroup_from_cgroup(struct cgroup *cgroup)
{
        return hugetlb_cgroup_from_css(cgroup_subsys_state(cgroup,
                                                           hugetlb_subsys_id));
}

static inline
struct hugetlb_cgroup *hugetlb_cgroup_from_task(struct task_struct *task)
{
        return hugetlb_cgroup_from_css(task_subsys_state(task,
                                                         hugetlb_subsys_id));
}

static inline bool hugetlb_cgroup_is_root(struct hugetlb_cgroup *h_cg)
{
        return (h_cg == root_h_cgroup);
}

static inline struct hugetlb_cgroup *parent_hugetlb_cgroup(struct cgroup *cg)
{
        if (!cg->parent)
                return NULL;
        return hugetlb_cgroup_from_cgroup(cg->parent);
}

static inline bool hugetlb_cgroup_have_usage(struct cgroup *cg)
{
        int idx;
        struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_cgroup(cg);

        for (idx = 0; idx < hugetlb_max_hstate; idx++) {
                if (page_counter_read(&h_cg->hugepage[idx]))
                        return true;
        }
        return false;
}

static struct cgroup_subsys_state *hugetlb_cgroup_css_alloc(struct cgroup *cgroup)
{
        int idx;
        struct cgroup *parent_cgroup;
        struct hugetlb_cgroup *h_cgroup, *parent_h_cgroup;

        h_cgroup = kzalloc(sizeof(*h_cgroup), GFP_KERNEL);
        if (!h_cgroup)
                return ERR_PTR(-ENOMEM);

        parent_cgroup = cgroup->parent;
        if (parent_cgroup) {
                parent_h_cgroup = hugetlb_cgroup_from_cgroup(parent_cgroup);
                for (idx = 0; idx < HUGE_MAX_HSTATE; idx++)
                        page_counter_init(&h_cgroup->hugepage[idx],
                                          &parent_h_cgroup->hugepage[idx]);
        } else {
                root_h_cgroup = h_cgroup;
                for (idx = 0; idx < HUGE_MAX_HSTATE; idx++)
                        page_counter_init(&h_cgroup->hugepage[idx], NULL);
        }
        return &h_cgroup->css;
}

static void hugetlb_cgroup_css_free(struct cgroup *cgroup)
{
        struct hugetlb_cgroup *h_cgroup;

        h_cgroup = hugetlb_cgroup_from_cgroup(cgroup);
        kfree(h_cgroup);
}


/*
 * Should be called with hugetlb_lock held.
 * Since we are holding hugetlb_lock, pages cannot get moved from
 * active list or uncharged from the cgroup, So no need to get
 * page reference and test for page active here. This function
 * cannot fail.
 */
static void hugetlb_cgroup_move_parent(int idx, struct cgroup *cgroup,
                                       struct page *page)
{
        unsigned int nr_pages;
        struct page_counter *counter;
        struct hugetlb_cgroup *page_hcg;
        struct hugetlb_cgroup *h_cg   = hugetlb_cgroup_from_cgroup(cgroup);
        struct hugetlb_cgroup *parent = parent_hugetlb_cgroup(cgroup);

        page_hcg = hugetlb_cgroup_from_page(page);
        /*
         * We can have pages in active list without any cgroup
         * ie, hugepage with less than 3 pages. We can safely
         * ignore those pages.
         */
        if (!page_hcg || page_hcg != h_cg)
                goto out;

        nr_pages = 1 << compound_order(page);
        if (!parent) {
                parent = root_h_cgroup;
                /* root has no limit */
                page_counter_charge(&parent->hugepage[idx], nr_pages);
        }
        counter = &h_cg->hugepage[idx];
        /* Take the pages off the local counter */
        page_counter_cancel(counter, nr_pages);

        set_hugetlb_cgroup(page, parent);
out:
        return;
}

/*
 * Force the hugetlb cgroup to empty the hugetlb resources by moving them to
 * the parent cgroup.
 */
static void hugetlb_cgroup_css_offline(struct cgroup *cgroup)
{
        struct hstate *h;
        struct page *page;
        int idx = 0;

        do {
                for_each_hstate(h) {
                        spin_lock(&hugetlb_lock);
                        list_for_each_entry(page, &h->hugepage_activelist, lru)
                                hugetlb_cgroup_move_parent(idx, cgroup, page);

                        spin_unlock(&hugetlb_lock);
                        idx++;
                }
                cond_resched();
        } while (hugetlb_cgroup_have_usage(cgroup));
}

int hugetlb_cgroup_charge_cgroup(int idx, unsigned long nr_pages,
                                 struct hugetlb_cgroup **ptr)
{
        int ret = 0;
        struct page_counter *counter;
        struct hugetlb_cgroup *h_cg = NULL;

        if (hugetlb_cgroup_disabled())
                goto done;
        /*
         * We don't charge any cgroup if the compound page have less
         * than 3 pages.
         */
        if (huge_page_order(&hstates[idx]) < HUGETLB_CGROUP_MIN_ORDER)
                goto done;
again:
        rcu_read_lock();
        h_cg = hugetlb_cgroup_from_task(current);
        if (!css_tryget(&h_cg->css)) {
                rcu_read_unlock();
                goto again;
        }
        rcu_read_unlock();

        if (!page_counter_try_charge(&h_cg->hugepage[idx], nr_pages, &counter))
                ret = -ENOMEM;
        css_put(&h_cg->css);
done:
        *ptr = h_cg;
        return ret;
}

/* Should be called with hugetlb_lock held */
void hugetlb_cgroup_commit_charge(int idx, unsigned long nr_pages,
                                  struct hugetlb_cgroup *h_cg,
                                  struct page *page)
{
        if (hugetlb_cgroup_disabled() || !h_cg)
                return;

        set_hugetlb_cgroup(page, h_cg);
        return;
}

/*
 * Should be called with hugetlb_lock held
 */
void hugetlb_cgroup_uncharge_page(int idx, unsigned long nr_pages,
                                  struct page *page)
{
        struct hugetlb_cgroup *h_cg;

        if (hugetlb_cgroup_disabled())
                return;
        VM_BUG_ON(!spin_is_locked(&hugetlb_lock));
        h_cg = hugetlb_cgroup_from_page(page);
        if (unlikely(!h_cg))
                return;
        set_hugetlb_cgroup(page, NULL);
        page_counter_uncharge(&h_cg->hugepage[idx], nr_pages);
        return;
}

void hugetlb_cgroup_uncharge_cgroup(int idx, unsigned long nr_pages,
                                    struct hugetlb_cgroup *h_cg)
{
        if (hugetlb_cgroup_disabled() || !h_cg)
                return;

        if (huge_page_order(&hstates[idx]) < HUGETLB_CGROUP_MIN_ORDER)
                return;

        page_counter_uncharge(&h_cg->hugepage[idx], nr_pages);
        return;
}

enum {
        RES_USAGE,
        RES_LIMIT,
        RES_MAX_USAGE,
        RES_FAILCNT,
};

static ssize_t hugetlb_cgroup_read(struct cgroup *cgroup, struct cftype *cft,
                                   struct file *file, char __user *buf,
                                   size_t nbytes, loff_t *ppos)
{
        u64 val;
        char str[64];
        int len;
        struct page_counter *counter;
        struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_cgroup(cgroup);

        counter = &h_cg->hugepage[MEMFILE_IDX(cft->private)];

        switch (MEMFILE_ATTR(cft->private)) {
        case RES_USAGE:
                val = (u64)page_counter_read(counter) * PAGE_SIZE;
                break;
        case RES_LIMIT:
                val = (u64)counter->limit * PAGE_SIZE;
                break;
        case RES_MAX_USAGE:
                val = (u64)counter->watermark * PAGE_SIZE;
                break;
        case RES_FAILCNT:
                val = counter->failcnt;
                break;
        default:
                BUG();
        }

        len = scnprintf(str, sizeof(str), "%llu\n", (unsigned long long)val);
        return simple_read_from_buffer(buf, nbytes, ppos, str, len);
}

static DEFINE_MUTEX(hugetlb_limit_mutex);

static int hugetlb_cgroup_write(struct cgroup *cgroup, struct cftype *cft,
                                const char *buffer)
{
        int idx, ret;
        unsigned long nr_pages;
        struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_cgroup(cgroup);

        if (hugetlb_cgroup_is_root(h_cg)) /* Can't set limit on root */
                return -EINVAL;

        ret = page_counter_memparse(buffer, &nr_pages);
        if (ret)
                return ret;

        idx = MEMFILE_IDX(cft->private);

        switch (MEMFILE_ATTR(cft->private)) {
        case RES_LIMIT:
                mutex_lock(&hugetlb_limit_mutex);
                ret = page_counter_limit(&h_cg->hugepage[idx], nr_pages);
                mutex_unlock(&hugetlb_limit_mutex);
                break;
        default:
                ret = -EINVAL;
                break;
        }
        return ret;
}

static int hugetlb_cgroup_reset(struct cgroup *cgroup, unsigned int event)
{
        int ret = 0;
        struct page_counter *counter;
        struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_cgroup(cgroup);

        counter = &h_cg->hugepage[MEMFILE_IDX(event)];

        switch (MEMFILE_ATTR(event)) {
        case RES_MAX_USAGE:
                page_counter_reset_watermark(counter);
                break;
        case RES_FAILCNT:
                counter->failcnt = 0;
                break;
        default:
                ret = -EINVAL;
                break;
        }
        return ret;
}

static char *mem_fmt(char *buf, int size, unsigned long hsize)
{
        if (hsize >= (1UL << 30))
                snprintf(buf, size, "%luGB", hsize >> 30);
        else if (hsize >= (1UL << 20))
                snprintf(buf, size, "%luMB", hsize >> 20);
        else
                snprintf(buf, size, "%luKB", hsize >> 10);
        return buf;
}

static void __init __hugetlb_cgroup_file_init(int idx)
{
        char buf[32];
        struct cftype *cft;
        struct hstate *h = &hstates[idx];

        /* format the size */
        mem_fmt(buf, 32, huge_page_size(h));

        /* Add the limit file */
        cft = &h->cgroup_files[0];
        snprintf(cft->name, MAX_CFTYPE_NAME, "%s.limit_in_bytes", buf);
        cft->private = MEMFILE_PRIVATE(idx, RES_LIMIT);
        cft->read = hugetlb_cgroup_read;
        cft->write_string = hugetlb_cgroup_write;

        /* Add the usage file */
        cft = &h->cgroup_files[1];
        snprintf(cft->name, MAX_CFTYPE_NAME, "%s.usage_in_bytes", buf);
        cft->private = MEMFILE_PRIVATE(idx, RES_USAGE);
        cft->read = hugetlb_cgroup_read;

        /* Add the MAX usage file */
        cft = &h->cgroup_files[2];
        snprintf(cft->name, MAX_CFTYPE_NAME, "%s.max_usage_in_bytes", buf);
        cft->private = MEMFILE_PRIVATE(idx, RES_MAX_USAGE);
        cft->trigger = hugetlb_cgroup_reset;
        cft->read = hugetlb_cgroup_read;

        /* Add the failcntfile */
        cft = &h->cgroup_files[3];
        snprintf(cft->name, MAX_CFTYPE_NAME, "%s.failcnt", buf);
        cft->private  = MEMFILE_PRIVATE(idx, RES_FAILCNT);
        cft->trigger  = hugetlb_cgroup_reset;
        cft->read = hugetlb_cgroup_read;

        /* NULL terminate the last cft */
        cft = &h->cgroup_files[4];
        memset(cft, 0, sizeof(*cft));

        WARN_ON(cgroup_add_cftypes(&hugetlb_subsys, h->cgroup_files));

        return;
}

void __init hugetlb_cgroup_file_init(void)
{
        struct hstate *h;

        for_each_hstate(h) {
                /*
                 * Add cgroup control files only if the huge page consists
                 * of more than two normal pages. This is because we use
                 * page[2].lru.next for storing cgroup details.
                 */
                if (huge_page_order(h) >= HUGETLB_CGROUP_MIN_ORDER)
                        __hugetlb_cgroup_file_init(hstate_index(h));
        }
}

/*
 * hugetlb_lock will make sure a parallel cgroup rmdir won't happen
 * when we migrate hugepages
 */
void hugetlb_cgroup_migrate(struct page *oldhpage, struct page *newhpage)
{
        struct hugetlb_cgroup *h_cg;
        struct hstate *h = page_hstate(oldhpage);

        if (hugetlb_cgroup_disabled())
                return;

        VM_BUG_ON_PAGE(!PageHuge(oldhpage), oldhpage);
        spin_lock(&hugetlb_lock);
        h_cg = hugetlb_cgroup_from_page(oldhpage);
        set_hugetlb_cgroup(oldhpage, NULL);

        /* move the h_cg details to new cgroup */
        set_hugetlb_cgroup(newhpage, h_cg);
        list_move(&newhpage->lru, &h->hugepage_activelist);
        spin_unlock(&hugetlb_lock);
        return;
}

struct cgroup_subsys hugetlb_subsys = {
        .name = "hugetlb",
        .css_alloc      = hugetlb_cgroup_css_alloc,
        .css_offline    = hugetlb_cgroup_css_offline,
        .css_free       = hugetlb_cgroup_css_free,
        .subsys_id      = hugetlb_subsys_id,
};