page_isolation.c

Go to the documentation of this file.

/*
 * linux/mm/page_isolation.c
 */

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

/* called while holding zone->lock */
static void set_pageblock_isolate(struct page *page)
{
    if (get_pageblock_migratetype(page) == MIGRATE_ISOLATE)
        return;

    set_pageblock_migratetype(page, MIGRATE_ISOLATE);
    page_zone(page)->nr_pageblock_isolate++;
}

/* called while holding zone->lock */
static void restore_pageblock_isolate(struct page *page, int migratetype)
{
    struct zone *zone = page_zone(page);
    if (WARN_ON(get_pageblock_migratetype(page) != MIGRATE_ISOLATE))
        return;

    BUG_ON(zone->nr_pageblock_isolate <= 0);
    set_pageblock_migratetype(page, migratetype);
    zone->nr_pageblock_isolate--;
}

int set_migratetype_isolate(struct page *page)
{
    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);

    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))
        ret = 0;

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

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

        set_pageblock_isolate(page);
        nr_pages = move_freepages_block(zone, page, MIGRATE_ISOLATE);

        __mod_zone_freepage_state(zone, -nr_pages, migratetype);
    }

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

void unset_migratetype_isolate(struct page *page, unsigned migratetype)
{
    struct zone *zone;
    unsigned long flags, nr_pages;

    zone = page_zone(page);
    spin_lock_irqsave(&zone->lock, flags);
    if (get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
        goto out;
    nr_pages = move_freepages_block(zone, page, migratetype);
    __mod_zone_freepage_state(zone, nr_pages, migratetype);
    restore_pageblock_isolate(page, migratetype);
out:
    spin_unlock_irqrestore(&zone->lock, flags);
}

static inline struct page *
__first_valid_page(unsigned long pfn, unsigned long nr_pages)
{
    int i;
    for (i = 0; i < nr_pages; i++)
        if (pfn_valid_within(pfn + i))
            break;
    if (unlikely(i == nr_pages))
        return NULL;
    return pfn_to_page(pfn + i);
}

/*
 * 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.
 * Returns 0 on success and -EBUSY if any part of range cannot be isolated.
 */
int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
                 unsigned migratetype)
{
    unsigned long pfn;
    unsigned long undo_pfn;
    struct page *page;

    BUG_ON((start_pfn) & (pageblock_nr_pages - 1));
    BUG_ON((end_pfn) & (pageblock_nr_pages - 1));

    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)) {
            undo_pfn = pfn;
            goto undo;
        }
    }
    return 0;
undo:
    for (pfn = start_pfn;
         pfn < undo_pfn;
         pfn += pageblock_nr_pages)
        unset_migratetype_isolate(pfn_to_page(pfn), 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((start_pfn) & (pageblock_nr_pages - 1));
    BUG_ON((end_pfn) & (pageblock_nr_pages - 1));
    for (pfn = start_pfn;
         pfn < end_pfn;
         pfn += pageblock_nr_pages) {
        page = __first_valid_page(pfn, pageblock_nr_pages);
        if (!page || get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
            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 1 if all pages in the range are isolated.
 */
static int
__test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn)
{
    struct page *page;

    while (pfn < end_pfn) {
        if (!pfn_valid_within(pfn)) {
            pfn++;
            continue;
        }
        page = pfn_to_page(pfn);
        if (PageBuddy(page)) {
            /*
             * If race between isolatation and allocation happens,
             * some free pages could be in MIGRATE_MOVABLE list
             * although pageblock's migratation type of the page
             * is MIGRATE_ISOLATE. Catch it and move the page into
             * MIGRATE_ISOLATE list.
             */
            if (get_freepage_migratetype(page) != MIGRATE_ISOLATE) {
                struct page *end_page;

                end_page = page + (1 << page_order(page)) - 1;
                move_freepages(page_zone(page), page, end_page,
                        MIGRATE_ISOLATE);
            }
            pfn += 1 << page_order(page);
        }
        else if (page_count(page) == 0 &&
            get_freepage_migratetype(page) == MIGRATE_ISOLATE)
            pfn += 1;
        else
            break;
    }
    if (pfn < end_pfn)
        return 0;
    return 1;
}

int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn)
{
    unsigned long pfn, flags;
    struct page *page;
    struct zone *zone;
    int ret;

    /*
     * Note: pageblock_nr_page != MAX_ORDER. Then, chunks of free page
     * is not aligned to pageblock_nr_pages.
     * Then we just check pagetype fist.
     */
    for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) {
        page = __first_valid_page(pfn, pageblock_nr_pages);
        if (page && get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
            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);
    ret = __test_page_isolated_in_pageblock(start_pfn, end_pfn);
    spin_unlock_irqrestore(&zone->lock, flags);
    return ret ? 0 : -EBUSY;
}

struct page *alloc_migrate_target(struct page *page, unsigned long private,
                  int **resultp)
{
    gfp_t gfp_mask = GFP_USER | __GFP_MOVABLE;

    if (PageHighMem(page))
        gfp_mask |= __GFP_HIGHMEM;

    return alloc_page(gfp_mask);
}