/*
 *
 * Copyright IBM Corporation, 2012
 * Author Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
 *
 * Cgroup v2
 * Copyright (C) 2019 Red Hat, Inc.
 * Author: Giuseppe Scrivano <gscrivan@redhat.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>

enum hugetlb_memory_event {
        HUGETLB_MAX,
        HUGETLB_NR_MEMORY_EVENTS,
};

struct hugetlb_cgroup {
        struct cgroup_subsys_state css;

        /*
         * the counter to account for hugepages from hugetlb.
         */
        struct page_counter hugepage[HUGE_MAX_HSTATE];

        atomic_long_t events[HUGE_MAX_HSTATE][HUGETLB_NR_MEMORY_EVENTS];
        atomic_long_t events_local[HUGE_MAX_HSTATE][HUGETLB_NR_MEMORY_EVENTS];

        /* Handle for "hugetlb.events" */
        struct cgroup_file events_file[HUGE_MAX_HSTATE];

        /* Handle for "hugetlb.events.local" */
        struct cgroup_file events_local_file[HUGE_MAX_HSTATE];
};

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

#define hugetlb_cgroup_from_counter(counter, idx)                   \
        container_of(counter, struct hugetlb_cgroup, hugepage[idx])

static struct hugetlb_cgroup *root_h_cgroup __read_mostly;

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

static inline
struct hugetlb_cgroup *hugetlb_cgroup_from_task(struct task_struct *task)
{
        return hugetlb_cgroup_from_css(task_css(task, hugetlb_cgrp_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 hugetlb_cgroup *h_cg)
{
        return hugetlb_cgroup_from_css(h_cg->css.parent);
}

static inline bool hugetlb_cgroup_have_usage(struct hugetlb_cgroup *h_cg)
{
        int idx;

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

static void hugetlb_cgroup_init(struct hugetlb_cgroup *h_cgroup,
                                struct hugetlb_cgroup *parent_h_cgroup)
{
        int idx;

        for (idx = 0; idx < HUGE_MAX_HSTATE; idx++) {
                struct page_counter *counter = &h_cgroup->hugepage[idx];
                struct page_counter *parent = NULL;
                unsigned long limit;
                int ret;

                if (parent_h_cgroup)
                        parent = &parent_h_cgroup->hugepage[idx];
                page_counter_init(counter, parent);

                limit = round_down(PAGE_COUNTER_MAX,
                                   1 << huge_page_order(&hstates[idx]));
                ret = page_counter_set_max(counter, limit);
                VM_BUG_ON(ret);
        }
}

static struct cgroup_subsys_state *
hugetlb_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
{
        struct hugetlb_cgroup *parent_h_cgroup = hugetlb_cgroup_from_css(parent_css);
        struct hugetlb_cgroup *h_cgroup;

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

        if (!parent_h_cgroup)
                root_h_cgroup = h_cgroup;

        hugetlb_cgroup_init(h_cgroup, parent_h_cgroup);
        return &h_cgroup->css;
}

static void hugetlb_cgroup_css_free(struct cgroup_subsys_state *css)
{
        struct hugetlb_cgroup *h_cgroup;

        h_cgroup = hugetlb_cgroup_from_css(css);
        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 hugetlb_cgroup *h_cg,
                                       struct page *page)
{
        unsigned int nr_pages;
        struct page_counter *counter;
        struct hugetlb_cgroup *page_hcg;
        struct hugetlb_cgroup *parent = parent_hugetlb_cgroup(h_cg);

        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 = compound_nr(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_subsys_state *css)
{
        struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_css(css);
        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, h_cg, page);

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

static inline void hugetlb_event(struct hugetlb_cgroup *hugetlb, int idx,
                                 enum hugetlb_memory_event event)
{
        atomic_long_inc(&hugetlb->events_local[idx][event]);
        cgroup_file_notify(&hugetlb->events_local_file[idx]);

        do {
                atomic_long_inc(&hugetlb->events[idx][event]);
                cgroup_file_notify(&hugetlb->events_file[idx]);
        } while ((hugetlb = parent_hugetlb_cgroup(hugetlb)) &&
                 !hugetlb_cgroup_is_root(hugetlb));
}

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;
                hugetlb_event(h_cg, idx, HUGETLB_MAX);
        }
        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;
        lockdep_assert_held(&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 u64 hugetlb_cgroup_read_u64(struct cgroup_subsys_state *css,
                                   struct cftype *cft)
{
        struct page_counter *counter;
        struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_css(css);

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

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

static int hugetlb_cgroup_read_u64_max(struct seq_file *seq, void *v)
{
        int idx;
        u64 val;
        struct cftype *cft = seq_cft(seq);
        unsigned long limit;
        struct page_counter *counter;
        struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_css(seq_css(seq));

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

        limit = round_down(PAGE_COUNTER_MAX,
                           1 << huge_page_order(&hstates[idx]));

        switch (MEMFILE_ATTR(cft->private)) {
        case RES_USAGE:
                val = (u64)page_counter_read(counter);
                seq_printf(seq, "%llu\n", val * PAGE_SIZE);
                break;
        case RES_LIMIT:
                val = (u64)counter->max;
                if (val == limit)
                        seq_puts(seq, "max\n");
                else
                        seq_printf(seq, "%llu\n", val * PAGE_SIZE);
                break;
        default:
                BUG();
        }

        return 0;
}

static DEFINE_MUTEX(hugetlb_limit_mutex);

static ssize_t hugetlb_cgroup_write(struct kernfs_open_file *of,
                                    char *buf, size_t nbytes, loff_t off,
                                    const char *max)
{
        int ret, idx;
        unsigned long nr_pages;
        struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_css(of_css(of));

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

        buf = strstrip(buf);
        ret = page_counter_memparse(buf, max, &nr_pages);
        if (ret)
                return ret;

        idx = MEMFILE_IDX(of_cft(of)->private);
        nr_pages = round_down(nr_pages, 1 << huge_page_order(&hstates[idx]));

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

static ssize_t hugetlb_cgroup_write_legacy(struct kernfs_open_file *of,
                                           char *buf, size_t nbytes, loff_t off)
{
        return hugetlb_cgroup_write(of, buf, nbytes, off, "-1");
}

static ssize_t hugetlb_cgroup_write_dfl(struct kernfs_open_file *of,
                                        char *buf, size_t nbytes, loff_t off)
{
        return hugetlb_cgroup_write(of, buf, nbytes, off, "max");
}

static ssize_t hugetlb_cgroup_reset(struct kernfs_open_file *of,
                                    char *buf, size_t nbytes, loff_t off)
{
        int ret = 0;
        struct page_counter *counter;
        struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_css(of_css(of));

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

        switch (MEMFILE_ATTR(of_cft(of)->private)) {
        case RES_MAX_USAGE:
                page_counter_reset_watermark(counter);
                break;
        case RES_FAILCNT:
                counter->failcnt = 0;
                break;
        default:
                ret = -EINVAL;
                break;
        }
        return ret ?: nbytes;
}

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 int __hugetlb_events_show(struct seq_file *seq, bool local)
{
        int idx;
        long max;
        struct cftype *cft = seq_cft(seq);
        struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_css(seq_css(seq));

        idx = MEMFILE_IDX(cft->private);

        if (local)
                max = atomic_long_read(&h_cg->events_local[idx][HUGETLB_MAX]);
        else
                max = atomic_long_read(&h_cg->events[idx][HUGETLB_MAX]);

        seq_printf(seq, "max %lu\n", max);

        return 0;
}

static int hugetlb_events_show(struct seq_file *seq, void *v)
{
        return __hugetlb_events_show(seq, false);
}

static int hugetlb_events_local_show(struct seq_file *seq, void *v)
{
        return __hugetlb_events_show(seq, true);
}

static void __init __hugetlb_cgroup_file_dfl_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_dfl[0];
        snprintf(cft->name, MAX_CFTYPE_NAME, "%s.max", buf);
        cft->private = MEMFILE_PRIVATE(idx, RES_LIMIT);
        cft->seq_show = hugetlb_cgroup_read_u64_max;
        cft->write = hugetlb_cgroup_write_dfl;
        cft->flags = CFTYPE_NOT_ON_ROOT;

        /* Add the current usage file */
        cft = &h->cgroup_files_dfl[1];
        snprintf(cft->name, MAX_CFTYPE_NAME, "%s.current", buf);
        cft->private = MEMFILE_PRIVATE(idx, RES_USAGE);
        cft->seq_show = hugetlb_cgroup_read_u64_max;
        cft->flags = CFTYPE_NOT_ON_ROOT;

        /* Add the events file */
        cft = &h->cgroup_files_dfl[2];
        snprintf(cft->name, MAX_CFTYPE_NAME, "%s.events", buf);
        cft->private = MEMFILE_PRIVATE(idx, 0);
        cft->seq_show = hugetlb_events_show;
        cft->file_offset = offsetof(struct hugetlb_cgroup, events_file[idx]),
        cft->flags = CFTYPE_NOT_ON_ROOT;

        /* Add the events.local file */
        cft = &h->cgroup_files_dfl[3];
        snprintf(cft->name, MAX_CFTYPE_NAME, "%s.events.local", buf);
        cft->private = MEMFILE_PRIVATE(idx, 0);
        cft->seq_show = hugetlb_events_local_show;
        cft->file_offset = offsetof(struct hugetlb_cgroup,
                                    events_local_file[idx]),
        cft->flags = CFTYPE_NOT_ON_ROOT;

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

        WARN_ON(cgroup_add_dfl_cftypes(&hugetlb_cgrp_subsys,
                                       h->cgroup_files_dfl));
}

static void __init __hugetlb_cgroup_file_legacy_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_legacy[0];
        snprintf(cft->name, MAX_CFTYPE_NAME, "%s.limit_in_bytes", buf);
        cft->private = MEMFILE_PRIVATE(idx, RES_LIMIT);
        cft->read_u64 = hugetlb_cgroup_read_u64;
        cft->write = hugetlb_cgroup_write_legacy;

        /* Add the usage file */
        cft = &h->cgroup_files_legacy[1];
        snprintf(cft->name, MAX_CFTYPE_NAME, "%s.usage_in_bytes", buf);
        cft->private = MEMFILE_PRIVATE(idx, RES_USAGE);
        cft->read_u64 = hugetlb_cgroup_read_u64;

        /* Add the MAX usage file */
        cft = &h->cgroup_files_legacy[2];
        snprintf(cft->name, MAX_CFTYPE_NAME, "%s.max_usage_in_bytes", buf);
        cft->private = MEMFILE_PRIVATE(idx, RES_MAX_USAGE);
        cft->write = hugetlb_cgroup_reset;
        cft->read_u64 = hugetlb_cgroup_read_u64;

        /* Add the failcntfile */
        cft = &h->cgroup_files_legacy[3];
        snprintf(cft->name, MAX_CFTYPE_NAME, "%s.failcnt", buf);
        cft->private  = MEMFILE_PRIVATE(idx, RES_FAILCNT);
        cft->write = hugetlb_cgroup_reset;
        cft->read_u64 = hugetlb_cgroup_read_u64;

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

        WARN_ON(cgroup_add_legacy_cftypes(&hugetlb_cgrp_subsys,
                                          h->cgroup_files_legacy));
}

static void __init __hugetlb_cgroup_file_init(int idx)
{
        __hugetlb_cgroup_file_dfl_init(idx);
        __hugetlb_cgroup_file_legacy_init(idx);
}

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].private 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;
}

static struct cftype hugetlb_files[] = {
        {} /* terminate */
};

struct cgroup_subsys hugetlb_cgrp_subsys = {
        .css_alloc      = hugetlb_cgroup_css_alloc,
        .css_offline    = hugetlb_cgroup_css_offline,
        .css_free       = hugetlb_cgroup_css_free,
        .dfl_cftypes    = hugetlb_files,
        .legacy_cftypes = hugetlb_files,
};