| // 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> |
| |
| /* |
| * This function checks whether the range [start_pfn, end_pfn) includes |
| * unmovable pages or not. The range must fall into a single pageblock and |
| * consequently belong to a single zone. |
| * |
| * PageLRU check without isolation or lru_lock could race so that |
| * MIGRATE_MOVABLE block might include unmovable pages. And __PageMovable |
| * check without lock_page also may miss some movable non-lru pages at |
| * race condition. So you can't expect this function should be exact. |
| * |
| * Returns a page without holding a reference. If the caller wants to |
| * dereference that page (e.g., dumping), it has to make sure that it |
| * cannot get removed (e.g., via memory unplug) concurrently. |
| * |
| */ |
| static struct page *has_unmovable_pages(unsigned long start_pfn, unsigned long end_pfn, |
| int migratetype, int flags) |
| { |
| struct page *page = pfn_to_page(start_pfn); |
| struct zone *zone = page_zone(page); |
| unsigned long pfn; |
| |
| VM_BUG_ON(ALIGN_DOWN(start_pfn, pageblock_nr_pages) != |
| ALIGN_DOWN(end_pfn - 1, pageblock_nr_pages)); |
| |
| if (is_migrate_cma_page(page)) { |
| /* |
| * CMA allocations (alloc_contig_range) really need to mark |
| * isolate CMA pageblocks even when they are not movable in fact |
| * so consider them movable here. |
| */ |
| if (is_migrate_cma(migratetype)) |
| return NULL; |
| |
| return page; |
| } |
| |
| for (pfn = start_pfn; pfn < end_pfn; pfn++) { |
| page = pfn_to_page(pfn); |
| |
| /* |
| * Both, bootmem allocations and memory holes are marked |
| * PG_reserved and are unmovable. We can even have unmovable |
| * allocations inside ZONE_MOVABLE, for example when |
| * specifying "movablecore". |
| */ |
| if (PageReserved(page)) |
| return page; |
| |
| /* |
| * If the zone is movable and we have ruled out all reserved |
| * pages then it should be reasonably safe to assume the rest |
| * is movable. |
| */ |
| if (zone_idx(zone) == ZONE_MOVABLE) |
| continue; |
| |
| /* |
| * Hugepages are not in LRU lists, but they're movable. |
| * THPs are on the LRU, but need to be counted as #small pages. |
| * We need not scan over tail pages because we don't |
| * handle each tail page individually in migration. |
| */ |
| if (PageHuge(page) || PageTransCompound(page)) { |
| struct page *head = compound_head(page); |
| unsigned int skip_pages; |
| |
| if (PageHuge(page)) { |
| if (!hugepage_migration_supported(page_hstate(head))) |
| return page; |
| } else if (!PageLRU(head) && !__PageMovable(head)) { |
| return page; |
| } |
| |
| skip_pages = compound_nr(head) - (page - head); |
| pfn += skip_pages - 1; |
| continue; |
| } |
| |
| /* |
| * We can't use page_count without pin a page |
| * because another CPU can free compound page. |
| * This check already skips compound tails of THP |
| * because their page->_refcount is zero at all time. |
| */ |
| if (!page_ref_count(page)) { |
| if (PageBuddy(page)) |
| pfn += (1 << buddy_order(page)) - 1; |
| continue; |
| } |
| |
| /* |
| * The HWPoisoned page may be not in buddy system, and |
| * page_count() is not 0. |
| */ |
| if ((flags & MEMORY_OFFLINE) && PageHWPoison(page)) |
| continue; |
| |
| /* |
| * We treat all PageOffline() pages as movable when offlining |
| * to give drivers a chance to decrement their reference count |
| * in MEM_GOING_OFFLINE in order to indicate that these pages |
| * can be offlined as there are no direct references anymore. |
| * For actually unmovable PageOffline() where the driver does |
| * not support this, we will fail later when trying to actually |
| * move these pages that still have a reference count > 0. |
| * (false negatives in this function only) |
| */ |
| if ((flags & MEMORY_OFFLINE) && PageOffline(page)) |
| continue; |
| |
| if (__PageMovable(page) || PageLRU(page)) |
| continue; |
| |
| /* |
| * If there are RECLAIMABLE pages, we need to check |
| * it. But now, memory offline itself doesn't call |
| * shrink_node_slabs() and it still to be fixed. |
| */ |
| return page; |
| } |
| return NULL; |
| } |
| |
| /* |
| * This function set pageblock migratetype to isolate if no unmovable page is |
| * present in [start_pfn, end_pfn). The pageblock must intersect with |
| * [start_pfn, end_pfn). |
| */ |
| static int set_migratetype_isolate(struct page *page, int migratetype, int isol_flags, |
| unsigned long start_pfn, unsigned long end_pfn) |
| { |
| struct zone *zone = page_zone(page); |
| struct page *unmovable; |
| unsigned long flags; |
| unsigned long check_unmovable_start, check_unmovable_end; |
| |
| 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. |
| */ |
| if (is_migrate_isolate_page(page)) { |
| spin_unlock_irqrestore(&zone->lock, flags); |
| return -EBUSY; |
| } |
| |
| /* |
| * FIXME: Now, memory hotplug doesn't call shrink_slab() by itself. |
| * We just check MOVABLE pages. |
| * |
| * Pass the intersection of [start_pfn, end_pfn) and the page's pageblock |
| * to avoid redundant checks. |
| */ |
| check_unmovable_start = max(page_to_pfn(page), start_pfn); |
| check_unmovable_end = min(ALIGN(page_to_pfn(page) + 1, pageblock_nr_pages), |
| end_pfn); |
| |
| unmovable = has_unmovable_pages(check_unmovable_start, check_unmovable_end, |
| migratetype, isol_flags); |
| if (!unmovable) { |
| 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); |
| return 0; |
| } |
| |
| spin_unlock_irqrestore(&zone->lock, flags); |
| if (isol_flags & REPORT_FAILURE) { |
| /* |
| * printk() with zone->lock held will likely trigger a |
| * lockdep splat, so defer it here. |
| */ |
| dump_page(unmovable, "unmovable page"); |
| } |
| |
| return -EBUSY; |
| } |
| |
| static void unset_migratetype_isolate(struct page *page, int migratetype) |
| { |
| struct zone *zone; |
| unsigned long flags, nr_pages; |
| bool isolated_page = false; |
| unsigned int order; |
| 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 = buddy_order(page); |
| if (order >= pageblock_order && order < MAX_ORDER - 1) { |
| buddy = find_buddy_page_pfn(page, page_to_pfn(page), |
| order, NULL); |
| if (buddy && !is_migrate_isolate_page(buddy)) { |
| isolated_page = !!__isolate_free_page(page, order); |
| /* |
| * Isolating a free page in an isolated pageblock |
| * is expected to always work as watermarks don't |
| * apply here. |
| */ |
| VM_WARN_ON(!isolated_page); |
| } |
| } |
| } |
| |
| /* |
| * 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. |
| * |
| * We didn't actually touch any of the isolated pages, so place them |
| * to the tail of the freelist. This is an optimization for memory |
| * onlining - just onlined memory won't immediately be considered for |
| * allocation. |
| */ |
| 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); |
| if (isolated_page) |
| __putback_isolated_page(page, order, migratetype); |
| zone->nr_isolate_pageblock--; |
| 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++) { |
| struct page *page; |
| |
| page = pfn_to_online_page(pfn + i); |
| if (!page) |
| continue; |
| return page; |
| } |
| return NULL; |
| } |
| |
| /** |
| * isolate_single_pageblock() -- tries to isolate a pageblock that might be |
| * within a free or in-use page. |
| * @boundary_pfn: pageblock-aligned pfn that a page might cross |
| * @flags: isolation flags |
| * @gfp_flags: GFP flags used for migrating pages |
| * @isolate_before: isolate the pageblock before the boundary_pfn |
| * |
| * Free and in-use pages can be as big as MAX_ORDER-1 and contain more than one |
| * pageblock. When not all pageblocks within a page are isolated at the same |
| * time, free page accounting can go wrong. For example, in the case of |
| * MAX_ORDER-1 = pageblock_order + 1, a MAX_ORDER-1 page has two pagelbocks. |
| * [ MAX_ORDER-1 ] |
| * [ pageblock0 | pageblock1 ] |
| * When either pageblock is isolated, if it is a free page, the page is not |
| * split into separate migratetype lists, which is supposed to; if it is an |
| * in-use page and freed later, __free_one_page() does not split the free page |
| * either. The function handles this by splitting the free page or migrating |
| * the in-use page then splitting the free page. |
| */ |
| static int isolate_single_pageblock(unsigned long boundary_pfn, int flags, |
| gfp_t gfp_flags, bool isolate_before, bool skip_isolation) |
| { |
| unsigned char saved_mt; |
| unsigned long start_pfn; |
| unsigned long isolate_pageblock; |
| unsigned long pfn; |
| struct zone *zone; |
| int ret; |
| |
| VM_BUG_ON(!IS_ALIGNED(boundary_pfn, pageblock_nr_pages)); |
| |
| if (isolate_before) |
| isolate_pageblock = boundary_pfn - pageblock_nr_pages; |
| else |
| isolate_pageblock = boundary_pfn; |
| |
| /* |
| * scan at the beginning of MAX_ORDER_NR_PAGES aligned range to avoid |
| * only isolating a subset of pageblocks from a bigger than pageblock |
| * free or in-use page. Also make sure all to-be-isolated pageblocks |
| * are within the same zone. |
| */ |
| zone = page_zone(pfn_to_page(isolate_pageblock)); |
| start_pfn = max(ALIGN_DOWN(isolate_pageblock, MAX_ORDER_NR_PAGES), |
| zone->zone_start_pfn); |
| |
| saved_mt = get_pageblock_migratetype(pfn_to_page(isolate_pageblock)); |
| |
| if (skip_isolation) |
| VM_BUG_ON(!is_migrate_isolate(saved_mt)); |
| else { |
| ret = set_migratetype_isolate(pfn_to_page(isolate_pageblock), saved_mt, flags, |
| isolate_pageblock, isolate_pageblock + pageblock_nr_pages); |
| |
| if (ret) |
| return ret; |
| } |
| |
| /* |
| * Bail out early when the to-be-isolated pageblock does not form |
| * a free or in-use page across boundary_pfn: |
| * |
| * 1. isolate before boundary_pfn: the page after is not online |
| * 2. isolate after boundary_pfn: the page before is not online |
| * |
| * This also ensures correctness. Without it, when isolate after |
| * boundary_pfn and [start_pfn, boundary_pfn) are not online, |
| * __first_valid_page() will return unexpected NULL in the for loop |
| * below. |
| */ |
| if (isolate_before) { |
| if (!pfn_to_online_page(boundary_pfn)) |
| return 0; |
| } else { |
| if (!pfn_to_online_page(boundary_pfn - 1)) |
| return 0; |
| } |
| |
| for (pfn = start_pfn; pfn < boundary_pfn;) { |
| struct page *page = __first_valid_page(pfn, boundary_pfn - pfn); |
| |
| VM_BUG_ON(!page); |
| pfn = page_to_pfn(page); |
| /* |
| * start_pfn is MAX_ORDER_NR_PAGES aligned, if there is any |
| * free pages in [start_pfn, boundary_pfn), its head page will |
| * always be in the range. |
| */ |
| if (PageBuddy(page)) { |
| int order = buddy_order(page); |
| |
| if (pfn + (1UL << order) > boundary_pfn) { |
| /* free page changed before split, check it again */ |
| if (split_free_page(page, order, boundary_pfn - pfn)) |
| continue; |
| } |
| |
| pfn += 1UL << order; |
| continue; |
| } |
| /* |
| * migrate compound pages then let the free page handling code |
| * above do the rest. If migration is not possible, just fail. |
| */ |
| if (PageCompound(page)) { |
| struct page *head = compound_head(page); |
| unsigned long head_pfn = page_to_pfn(head); |
| unsigned long nr_pages = compound_nr(head); |
| |
| if (head_pfn + nr_pages <= boundary_pfn) { |
| pfn = head_pfn + nr_pages; |
| continue; |
| } |
| #if defined CONFIG_COMPACTION || defined CONFIG_CMA |
| /* |
| * hugetlb, lru compound (THP), and movable compound pages |
| * can be migrated. Otherwise, fail the isolation. |
| */ |
| if (PageHuge(page) || PageLRU(page) || __PageMovable(page)) { |
| int order; |
| unsigned long outer_pfn; |
| int page_mt = get_pageblock_migratetype(page); |
| bool isolate_page = !is_migrate_isolate_page(page); |
| struct compact_control cc = { |
| .nr_migratepages = 0, |
| .order = -1, |
| .zone = page_zone(pfn_to_page(head_pfn)), |
| .mode = MIGRATE_SYNC, |
| .ignore_skip_hint = true, |
| .no_set_skip_hint = true, |
| .gfp_mask = gfp_flags, |
| .alloc_contig = true, |
| }; |
| INIT_LIST_HEAD(&cc.migratepages); |
| |
| /* |
| * XXX: mark the page as MIGRATE_ISOLATE so that |
| * no one else can grab the freed page after migration. |
| * Ideally, the page should be freed as two separate |
| * pages to be added into separate migratetype free |
| * lists. |
| */ |
| if (isolate_page) { |
| ret = set_migratetype_isolate(page, page_mt, |
| flags, head_pfn, head_pfn + nr_pages); |
| if (ret) |
| goto failed; |
| } |
| |
| ret = __alloc_contig_migrate_range(&cc, head_pfn, |
| head_pfn + nr_pages); |
| |
| /* |
| * restore the page's migratetype so that it can |
| * be split into separate migratetype free lists |
| * later. |
| */ |
| if (isolate_page) |
| unset_migratetype_isolate(page, page_mt); |
| |
| if (ret) |
| goto failed; |
| /* |
| * reset pfn to the head of the free page, so |
| * that the free page handling code above can split |
| * the free page to the right migratetype list. |
| * |
| * head_pfn is not used here as a hugetlb page order |
| * can be bigger than MAX_ORDER-1, but after it is |
| * freed, the free page order is not. Use pfn within |
| * the range to find the head of the free page. |
| */ |
| order = 0; |
| outer_pfn = pfn; |
| while (!PageBuddy(pfn_to_page(outer_pfn))) { |
| /* stop if we cannot find the free page */ |
| if (++order >= MAX_ORDER) |
| goto failed; |
| outer_pfn &= ~0UL << order; |
| } |
| pfn = outer_pfn; |
| continue; |
| } else |
| #endif |
| goto failed; |
| } |
| |
| pfn++; |
| } |
| return 0; |
| failed: |
| /* restore the original migratetype */ |
| if (!skip_isolation) |
| unset_migratetype_isolate(pfn_to_page(isolate_pageblock), saved_mt); |
| return -EBUSY; |
| } |
| |
| /** |
| * 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. |
| * @flags: The following flags are allowed (they can be combined in |
| * a bit mask) |
| * MEMORY_OFFLINE - isolate to offline (!allocate) memory |
| * e.g., skip over PageHWPoison() pages |
| * and PageOffline() pages. |
| * REPORT_FAILURE - report details about the failure to |
| * isolate the range |
| * @gfp_flags: GFP flags used for migrating pages that sit across the |
| * range boundaries. |
| * |
| * 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. If specified range includes migrate types |
| * other than MOVABLE or CMA, this will fail with -EBUSY. For isolating all |
| * pages in the range finally, the caller have to free all pages in the range. |
| * test_page_isolated() can be used for test it. |
| * |
| * The function first tries to isolate the pageblocks at the beginning and end |
| * of the range, since there might be pages across the range boundaries. |
| * Afterwards, it isolates the rest of the range. |
| * |
| * 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. |
| * |
| * Please note that there is no strong synchronization with the page allocator |
| * either. Pages might be freed while their page blocks are marked ISOLATED. |
| * A call to drain_all_pages() after isolation can flush most of them. However |
| * in some cases pages might still end up on pcp lists and that would allow |
| * for their allocation even when they are in fact isolated already. Depending |
| * on how strong of a guarantee the caller needs, zone_pcp_disable/enable() |
| * might be used to flush and disable pcplist before isolation and enable after |
| * unisolation. |
| * |
| * Return: 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, |
| int migratetype, int flags, gfp_t gfp_flags) |
| { |
| unsigned long pfn; |
| struct page *page; |
| /* isolation is done at page block granularity */ |
| unsigned long isolate_start = ALIGN_DOWN(start_pfn, pageblock_nr_pages); |
| unsigned long isolate_end = ALIGN(end_pfn, pageblock_nr_pages); |
| int ret; |
| bool skip_isolation = false; |
| |
| /* isolate [isolate_start, isolate_start + pageblock_nr_pages) pageblock */ |
| ret = isolate_single_pageblock(isolate_start, flags, gfp_flags, false, skip_isolation); |
| if (ret) |
| return ret; |
| |
| if (isolate_start == isolate_end - pageblock_nr_pages) |
| skip_isolation = true; |
| |
| /* isolate [isolate_end - pageblock_nr_pages, isolate_end) pageblock */ |
| ret = isolate_single_pageblock(isolate_end, flags, gfp_flags, true, skip_isolation); |
| if (ret) { |
| unset_migratetype_isolate(pfn_to_page(isolate_start), migratetype); |
| return ret; |
| } |
| |
| /* skip isolated pageblocks at the beginning and end */ |
| for (pfn = isolate_start + pageblock_nr_pages; |
| pfn < isolate_end - pageblock_nr_pages; |
| pfn += pageblock_nr_pages) { |
| page = __first_valid_page(pfn, pageblock_nr_pages); |
| if (page && set_migratetype_isolate(page, migratetype, flags, |
| start_pfn, end_pfn)) { |
| undo_isolate_page_range(isolate_start, pfn, migratetype); |
| unset_migratetype_isolate( |
| pfn_to_page(isolate_end - pageblock_nr_pages), |
| migratetype); |
| return -EBUSY; |
| } |
| } |
| return 0; |
| } |
| |
| /* |
| * Make isolated pages available again. |
| */ |
| void undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn, |
| int migratetype) |
| { |
| unsigned long pfn; |
| struct page *page; |
| unsigned long isolate_start = ALIGN_DOWN(start_pfn, pageblock_nr_pages); |
| unsigned long isolate_end = ALIGN(end_pfn, pageblock_nr_pages); |
| |
| |
| for (pfn = isolate_start; |
| pfn < isolate_end; |
| 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); |
| } |
| } |
| /* |
| * 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, |
| int flags) |
| { |
| struct page *page; |
| |
| while (pfn < end_pfn) { |
| 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 << buddy_order(page); |
| else if ((flags & MEMORY_OFFLINE) && PageHWPoison(page)) |
| /* A HWPoisoned page cannot be also PageBuddy */ |
| pfn++; |
| else if ((flags & MEMORY_OFFLINE) && PageOffline(page) && |
| !page_count(page)) |
| /* |
| * The responsible driver agreed to skip PageOffline() |
| * pages when offlining memory by dropping its |
| * reference in MEM_GOING_OFFLINE. |
| */ |
| 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, |
| int isol_flags) |
| { |
| unsigned long pfn, flags; |
| struct page *page; |
| struct zone *zone; |
| int ret; |
| |
| /* |
| * 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) { |
| ret = -EBUSY; |
| goto out; |
| } |
| |
| /* 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, isol_flags); |
| spin_unlock_irqrestore(&zone->lock, flags); |
| |
| ret = pfn < end_pfn ? -EBUSY : 0; |
| |
| out: |
| trace_test_pages_isolated(start_pfn, end_pfn, pfn); |
| |
| return ret; |
| } |