diff options
Diffstat (limited to 'mm/page_isolation.c')
| -rw-r--r-- | mm/page_isolation.c | 119 |
1 files changed, 119 insertions, 0 deletions
diff --git a/mm/page_isolation.c b/mm/page_isolation.c index ff0ea6308299..df49f86a6ed1 100644 --- a/mm/page_isolation.c +++ b/mm/page_isolation.c @@ -15,6 +15,125 @@ #define CREATE_TRACE_POINTS #include <trace/events/page_isolation.h> +/* + * This function checks whether pageblock includes unmovable pages or not. + * + * 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(struct zone *zone, struct page *page, + int migratetype, int flags) +{ + unsigned long iter = 0; + unsigned long pfn = page_to_pfn(page); + unsigned long offset = pfn % 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 (; iter < pageblock_nr_pages - offset; iter++) { + page = pfn_to_page(pfn + iter); + + /* + * 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); + iter += 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)) + iter += (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; +} + static int set_migratetype_isolate(struct page *page, int migratetype, int isol_flags) { struct zone *zone = page_zone(page); |