diff options
Diffstat (limited to 'mm/page_isolation.c')
| -rw-r--r-- | mm/page_isolation.c | 193 |
1 files changed, 188 insertions, 5 deletions
diff --git a/mm/page_isolation.c b/mm/page_isolation.c index c2f7a8bb634d..8a0f16d2e4c3 100644 --- a/mm/page_isolation.c +++ b/mm/page_isolation.c @@ -203,7 +203,7 @@ 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; @@ -280,6 +280,166 @@ __first_valid_page(unsigned long pfn, unsigned long nr_pages) } /** + * 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 + * @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, gfp_t gfp_flags, + bool isolate_before) +{ + unsigned char saved_mt; + unsigned long start_pfn; + unsigned long isolate_pageblock; + unsigned long pfn; + struct zone *zone; + + 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)); + set_pageblock_migratetype(pfn_to_page(isolate_pageblock), MIGRATE_ISOLATE); + + /* + * 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) + split_free_page(page, order, boundary_pfn - pfn); + 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)) { + unsigned long nr_pages = compound_nr(page); + struct page *head = compound_head(page); + unsigned long head_pfn = page_to_pfn(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 ret; + 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); + + ret = __alloc_contig_migrate_range(&cc, head_pfn, + head_pfn + nr_pages); + + 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))) { + if (++order >= MAX_ORDER) { + outer_pfn = pfn; + break; + } + outer_pfn &= ~0UL << order; + } + pfn = outer_pfn; + continue; + } else +#endif + goto failed; + } + + pfn++; + } + return 0; +failed: + /* restore the original migratetype */ + set_pageblock_migratetype(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. @@ -293,6 +453,8 @@ __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 @@ -301,6 +463,10 @@ __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. @@ -321,21 +487,38 @@ __first_valid_page(unsigned long pfn, unsigned long nr_pages) * 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; struct page *page; + int ret; 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; + /* isolate [start_pfn, start_pfn + pageblock_nr_pages) pageblock */ + ret = isolate_single_pageblock(start_pfn, gfp_flags, false); + if (ret) + return ret; + + /* isolate [end_pfn - pageblock_nr_pages, end_pfn) pageblock */ + ret = isolate_single_pageblock(end_pfn, gfp_flags, true); + if (ret) { + unset_migratetype_isolate(pfn_to_page(start_pfn), migratetype); + return ret; + } + + /* skip isolated pageblocks at the beginning and end */ + for (pfn = start_pfn + pageblock_nr_pages; + pfn < end_pfn - 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(start_pfn, pfn, migratetype); + unset_migratetype_isolate( + pfn_to_page(end_pfn - pageblock_nr_pages), + migratetype); return -EBUSY; } } @@ -346,7 +529,7 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn, * Make isolated pages available again. */ void undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn, - unsigned migratetype) + int migratetype) { unsigned long pfn; struct page *page; |