diff options
Diffstat (limited to 'mm/page_isolation.c')
| -rw-r--r-- | mm/page_isolation.c | 520 |
1 files changed, 450 insertions, 70 deletions
diff --git a/mm/page_isolation.c b/mm/page_isolation.c index aa94afb63823..cd0ea3668253 100644 --- a/mm/page_isolation.c +++ b/mm/page_isolation.c @@ -15,11 +15,142 @@ #define CREATE_TRACE_POINTS #include <trace/events/page_isolation.h> -static int set_migratetype_isolate(struct page *page, int migratetype, int isol_flags) +/* + * 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(pageblock_start_pfn(start_pfn) != + pageblock_start_pfn(end_pfn - 1)); + + 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 folio *folio = page_folio(page); + unsigned int skip_pages; + + if (PageHuge(page)) { + if (!hugepage_migration_supported(folio_hstate(folio))) + return page; + } else if (!folio_test_lru(folio) && !__folio_test_movable(folio)) { + return page; + } + + skip_pages = folio_nr_pages(folio) - folio_page_idx(folio, page); + 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); @@ -36,8 +167,16 @@ static int set_migratetype_isolate(struct page *page, int migratetype, int isol_ /* * 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. */ - unmovable = has_unmovable_pages(zone, page, migratetype, isol_flags); + check_unmovable_start = max(page_to_pfn(page), start_pfn); + check_unmovable_end = min(pageblock_end_pfn(page_to_pfn(page)), + 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); @@ -49,7 +188,6 @@ static int set_migratetype_isolate(struct page *page, int migratetype, int isol_ __mod_zone_freepage_state(zone, -nr_pages, mt); spin_unlock_irqrestore(&zone->lock, flags); - drain_all_pages(zone); return 0; } @@ -65,13 +203,12 @@ static int set_migratetype_isolate(struct page *page, int migratetype, int isol_ return -EBUSY; } -static void unset_migratetype_isolate(struct page *page, unsigned migratetype) +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; - unsigned long pfn, buddy_pfn; struct page *buddy; zone = page_zone(page); @@ -88,16 +225,18 @@ static void unset_migratetype_isolate(struct page *page, unsigned migratetype) * 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; + order = buddy_order(page); + if (order >= pageblock_order && order < MAX_PAGE_ORDER) { + 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); } } } @@ -106,6 +245,11 @@ static void unset_migratetype_isolate(struct page *page, unsigned migratetype) * 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); @@ -136,11 +280,211 @@ __first_valid_page(unsigned long pfn, unsigned long nr_pages) } /** - * 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. - * start_pfn/end_pfn must be aligned to pageblock_order. + * 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 + * @skip_isolation: the flag to skip the pageblock isolation in second + * isolate_single_pageblock() + * @migratetype: migrate type to set in error recovery. + * + * Free and in-use pages can be as big as MAX_PAGE_ORDER 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_PAGE_ORDER = pageblock_order + 1, a MAX_PAGE_ORDER page has two + * pagelbocks. + * [ MAX_PAGE_ORDER ] + * [ 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, + int migratetype) +{ + unsigned long start_pfn; + unsigned long isolate_pageblock; + unsigned long pfn; + struct zone *zone; + int ret; + + VM_BUG_ON(!pageblock_aligned(boundary_pfn)); + + 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); + + if (skip_isolation) { + int mt __maybe_unused = get_pageblock_migratetype(pfn_to_page(isolate_pageblock)); + + VM_BUG_ON(!is_migrate_isolate(mt)); + } else { + ret = set_migratetype_isolate(pfn_to_page(isolate_pageblock), migratetype, + 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_PAGE_ORDER, 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_PAGE_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), migratetype); + return -EBUSY; +} + +/** + * start_isolate_page_range() - mark page range MIGRATE_ISOLATE + * @start_pfn: The first PFN of the range to be isolated. + * @end_pfn: The last 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) @@ -149,6 +493,8 @@ __first_valid_page(unsigned long pfn, unsigned long nr_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 @@ -157,6 +503,10 @@ __first_valid_page(unsigned long pfn, unsigned long nr_pages) * 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. @@ -167,66 +517,79 @@ __first_valid_page(unsigned long pfn, unsigned long nr_pages) * * Please note that there is no strong synchronization with the page allocator * either. Pages might be freed while their page blocks are marked ISOLATED. - * In some cases pages might still end up on pcp lists and that would allow + * 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 drain_all_pages might be needed - * (e.g. __offline_pages will need to call it after check for isolated range for - * a next retry). + * 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: the number of isolated pageblocks on success and -EBUSY if any part - * of range cannot be isolated. + * 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, - unsigned migratetype, int flags) + int migratetype, int flags, gfp_t gfp_flags) { unsigned long pfn; - unsigned long undo_pfn; struct page *page; - int nr_isolate_pageblock = 0; + /* isolation is done at page block granularity */ + unsigned long isolate_start = pageblock_start_pfn(start_pfn); + unsigned long isolate_end = pageblock_align(end_pfn); + int ret; + bool skip_isolation = false; - BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages)); - BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages)); + /* isolate [isolate_start, isolate_start + pageblock_nr_pages) pageblock */ + ret = isolate_single_pageblock(isolate_start, flags, gfp_flags, false, + skip_isolation, migratetype); + if (ret) + return ret; - for (pfn = start_pfn; - pfn < end_pfn; + 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, migratetype); + 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) { - if (set_migratetype_isolate(page, migratetype, flags)) { - undo_pfn = pfn; - goto undo; - } - nr_isolate_pageblock++; + 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 nr_isolate_pageblock; -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; + return 0; } -/* - * Make isolated pages available again. +/** + * undo_isolate_page_range - undo effects of start_isolate_page_range() + * @start_pfn: The first PFN of the isolated range + * @end_pfn: The last PFN of the isolated range + * @migratetype: New migrate type to set on the range + * + * This finds every MIGRATE_ISOLATE page block in the given range + * and switches it to @migratetype. */ void undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn, - unsigned migratetype) + int migratetype) { unsigned long pfn; struct page *page; + unsigned long isolate_start = pageblock_start_pfn(start_pfn); + unsigned long isolate_end = pageblock_align(end_pfn); - 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; + 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)) @@ -248,10 +611,6 @@ __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)) /* @@ -259,7 +618,7 @@ __test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn, * the correct MIGRATE_ISOLATE freelist. There is no * simple way to verify that as VM_BUG_ON(), though. */ - pfn += 1 << page_order(page); + pfn += 1 << buddy_order(page); else if ((flags & MEMORY_OFFLINE) && PageHWPoison(page)) /* A HWPoisoned page cannot be also PageBuddy */ pfn++; @@ -278,17 +637,32 @@ __test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn, return pfn; } -/* Caller should ensure that requested range is in a single zone */ +/** + * test_pages_isolated - check if pageblocks in range are isolated + * @start_pfn: The first PFN of the isolated range + * @end_pfn: The first PFN *after* the isolated range + * @isol_flags: Testing mode flags + * + * This tests if all in the specified range are free. + * + * If %MEMORY_OFFLINE is specified in @flags, it will consider + * poisoned and offlined pages free as well. + * + * Caller must ensure the requested range doesn't span zones. + * + * Returns 0 if true, -EBUSY if one or more pages are in use. + */ 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. + * Note: pageblock_nr_pages != MAX_PAGE_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) { @@ -297,15 +671,21 @@ int test_pages_isolated(unsigned long start_pfn, unsigned long end_pfn, break; } page = __first_valid_page(start_pfn, end_pfn - start_pfn); - if ((pfn < end_pfn) || !page) - return -EBUSY; + 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 pfn < end_pfn ? -EBUSY : 0; + return ret; } |