// SPDX-License-Identifier: GPL-2.0
/*
 * linux/mm/page_isolation.c
 */

#include <linux/mm.h>
#include <linux/page-isolation.h>
#include <linux/pageblock-flags.h>
#include <linux/memory.h>
#include <linux/hugetlb.h>
#include <linux/page_owner.h>
#include <linux/migrate.h>
#include "internal.h"

#define CREATE_TRACE_POINTS
#include <trace/events/page_isolation.h>

static int set_migratetype_isolate(struct page *page, int migratetype,
                                bool skip_hwpoisoned_pages)
{
        struct zone *zone;
        unsigned long flags, pfn;
        struct memory_isolate_notify arg;
        int notifier_ret;
        int ret = -EBUSY;

        zone = page_zone(page);

        spin_lock_irqsave(&zone->lock, flags);

        /*
         * We assume the caller intended to SET migrate type to isolate.
         * If it is already set, then someone else must have raced and
         * set it before us.  Return -EBUSY
         */
        if (is_migrate_isolate_page(page))
                goto out;

        pfn = page_to_pfn(page);
        arg.start_pfn = pfn;
        arg.nr_pages = pageblock_nr_pages;
        arg.pages_found = 0;

        /*
         * It may be possible to isolate a pageblock even if the
         * migratetype is not MIGRATE_MOVABLE. The memory isolation
         * notifier chain is used by balloon drivers to return the
         * number of pages in a range that are held by the balloon
         * driver to shrink memory. If all the pages are accounted for
         * by balloons, are free, or on the LRU, isolation can continue.
         * Later, for example, when memory hotplug notifier runs, these
         * pages reported as "can be isolated" should be isolated(freed)
         * by the balloon driver through the memory notifier chain.
         */
        notifier_ret = memory_isolate_notify(MEM_ISOLATE_COUNT, &arg);
        notifier_ret = notifier_to_errno(notifier_ret);
        if (notifier_ret)
                goto out;
        /*
         * FIXME: Now, memory hotplug doesn't call shrink_slab() by itself.
         * We just check MOVABLE pages.
         */
        if (!has_unmovable_pages(zone, page, arg.pages_found, migratetype,
                                 skip_hwpoisoned_pages))
                ret = 0;

        /*
         * immobile means "not-on-lru" pages. If immobile is larger than
         * removable-by-driver pages reported by notifier, we'll fail.
         */

out:
        if (!ret) {
                unsigned long nr_pages;
                int mt = get_pageblock_migratetype(page);

                set_pageblock_migratetype(page, MIGRATE_ISOLATE);
                zone->nr_isolate_pageblock++;
                nr_pages = move_freepages_block(zone, page, MIGRATE_ISOLATE,
                                                                        NULL);

                __mod_zone_freepage_state(zone, -nr_pages, mt);
        }

        spin_unlock_irqrestore(&zone->lock, flags);
        if (!ret)
                drain_all_pages(zone);
        return ret;
}

static void unset_migratetype_isolate(struct page *page, unsigned migratetype)
{
        struct zone *zone;
        unsigned long flags, nr_pages;
        bool isolated_page = false;
        unsigned int order;
        unsigned long pfn, buddy_pfn;
        struct page *buddy;

        zone = page_zone(page);
        spin_lock_irqsave(&zone->lock, flags);
        if (!is_migrate_isolate_page(page))
                goto out;

        /*
         * Because freepage with more than pageblock_order on isolated
         * pageblock is restricted to merge due to freepage counting problem,
         * it is possible that there is free buddy page.
         * move_freepages_block() doesn't care of merge so we need other
         * approach in order to merge them. Isolation and free will make
         * these pages to be merged.
         */
        if (PageBuddy(page)) {
                order = page_order(page);
                if (order >= pageblock_order) {
                        pfn = page_to_pfn(page);
                        buddy_pfn = __find_buddy_pfn(pfn, order);
                        buddy = page + (buddy_pfn - pfn);

                        if (pfn_valid_within(buddy_pfn) &&
                            !is_migrate_isolate_page(buddy)) {
                                __isolate_free_page(page, order);
                                isolated_page = true;
                        }
                }
        }

        /*
         * If we isolate freepage with more than pageblock_order, there
         * should be no freepage in the range, so we could avoid costly
         * pageblock scanning for freepage moving.
         */
        if (!isolated_page) {
                nr_pages = move_freepages_block(zone, page, migratetype, NULL);
                __mod_zone_freepage_state(zone, nr_pages, migratetype);
        }
        set_pageblock_migratetype(page, migratetype);
        zone->nr_isolate_pageblock--;
out:
        spin_unlock_irqrestore(&zone->lock, flags);
        if (isolated_page) {
                post_alloc_hook(page, order, __GFP_MOVABLE);
                __free_pages(page, order);
        }
}

static inline struct page *
__first_valid_page(unsigned long pfn, unsigned long nr_pages)
{
        int i;

        for (i = 0; i < nr_pages; i++) {
                struct page *page;

                if (!pfn_valid_within(pfn + i))
                        continue;
                page = pfn_to_online_page(pfn + i);
                if (!page)
                        continue;
                return page;
        }
        return NULL;
}

/*
 * start_isolate_page_range() -- make page-allocation-type of range of pages
 * to be MIGRATE_ISOLATE.
 * @start_pfn: The lower PFN of the range to be isolated.
 * @end_pfn: The upper PFN of the range to be isolated.
 * @migratetype: migrate type to set in error recovery.
 *
 * Making page-allocation-type to be MIGRATE_ISOLATE means free pages in
 * the range will never be allocated. Any free pages and pages freed in the
 * future will not be allocated again.
 *
 * start_pfn/end_pfn must be aligned to pageblock_order.
 * Return 0 on success and -EBUSY if any part of range cannot be isolated.
 *
 * There is no high level synchronization mechanism that prevents two threads
 * from trying to isolate overlapping ranges.  If this happens, one thread
 * will notice pageblocks in the overlapping range already set to isolate.
 * This happens in set_migratetype_isolate, and set_migratetype_isolate
 * returns an error.  We then clean up by restoring the migration type on
 * pageblocks we may have modified and return -EBUSY to caller.  This
 * prevents two threads from simultaneously working on overlapping ranges.
 */
int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
                             unsigned migratetype, bool skip_hwpoisoned_pages)
{
        unsigned long pfn;
        unsigned long undo_pfn;
        struct page *page;

        BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages));
        BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages));

        for (pfn = start_pfn;
             pfn < end_pfn;
             pfn += pageblock_nr_pages) {
                page = __first_valid_page(pfn, pageblock_nr_pages);
                if (page &&
                    set_migratetype_isolate(page, migratetype, skip_hwpoisoned_pages)) {
                        undo_pfn = pfn;
                        goto undo;
                }
        }
        return 0;
undo:
        for (pfn = start_pfn;
             pfn < undo_pfn;
             pfn += pageblock_nr_pages) {
                struct page *page = pfn_to_online_page(pfn);
                if (!page)
                        continue;
                unset_migratetype_isolate(page, migratetype);
        }

        return -EBUSY;
}

/*
 * Make isolated pages available again.
 */
int undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
                            unsigned migratetype)
{
        unsigned long pfn;
        struct page *page;

        BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages));
        BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages));

        for (pfn = start_pfn;
             pfn < end_pfn;
             pfn += pageblock_nr_pages) {
                page = __first_valid_page(pfn, pageblock_nr_pages);
                if (!page || !is_migrate_isolate_page(page))
                        continue;
                unset_migratetype_isolate(page, migratetype);
        }
        return 0;
}
/*
 * Test all pages in the range is free(means isolated) or not.
 * all pages in [start_pfn...end_pfn) must be in the same zone.
 * zone->lock must be held before call this.
 *
 * Returns the last tested pfn.
 */
static unsigned long
__test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn,
                                  bool skip_hwpoisoned_pages)
{
        struct page *page;

        while (pfn < end_pfn) {
                if (!pfn_valid_within(pfn)) {
                        pfn++;
                        continue;
                }
                page = pfn_to_page(pfn);
                if (PageBuddy(page))
                        /*
                         * If the page is on a free list, it has to be on
                         * the correct MIGRATE_ISOLATE freelist. There is no
                         * simple way to verify that as VM_BUG_ON(), though.
                         */
                        pfn += 1 << page_order(page);
                else if (skip_hwpoisoned_pages && PageHWPoison(page))
                        /* A HWPoisoned page cannot be also PageBuddy */
                        pfn++;
                else
                        break;
        }

        return pfn;
}

/* Caller should ensure that requested range is in a single zone */
int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn,
                        bool skip_hwpoisoned_pages)
{
        unsigned long pfn, flags;
        struct page *page;
        struct zone *zone;

        /*
         * Note: pageblock_nr_pages != MAX_ORDER. Then, chunks of free pages
         * are not aligned to pageblock_nr_pages.
         * Then we just check migratetype first.
         */
        for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
                page = __first_valid_page(pfn, pageblock_nr_pages);
                if (page && !is_migrate_isolate_page(page))
                        break;
        }
        page = __first_valid_page(start_pfn, end_pfn - start_pfn);
        if ((pfn < end_pfn) || !page)
                return -EBUSY;
        /* Check all pages are free or marked as ISOLATED */
        zone = page_zone(page);
        spin_lock_irqsave(&zone->lock, flags);
        pfn = __test_page_isolated_in_pageblock(start_pfn, end_pfn,
                                                skip_hwpoisoned_pages);
        spin_unlock_irqrestore(&zone->lock, flags);

        trace_test_pages_isolated(start_pfn, end_pfn, pfn);

        return pfn < end_pfn ? -EBUSY : 0;
}

struct page *alloc_migrate_target(struct page *page, unsigned long private)
{
        return new_page_nodemask(page, numa_node_id(), &node_states[N_MEMORY]);
}