// 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, int isol_flags) { 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, flags)) 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, int flags) { 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, flags)) { 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]); }