From: Shakeel Butt Date: Tue, 15 Dec 2020 03:06:39 +0000 (-0800) Subject: mm/rmap: always do TTU_IGNORE_ACCESS X-Git-Tag: v5.15~2223^2~140 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=013339df116c2ee0d796dd8bfb8f293a2030c063;p=platform%2Fkernel%2Flinux-starfive.git mm/rmap: always do TTU_IGNORE_ACCESS Since commit 369ea8242c0f ("mm/rmap: update to new mmu_notifier semantic v2"), the code to check the secondary MMU's page table access bit is broken for !(TTU_IGNORE_ACCESS) because the page is unmapped from the secondary MMU's page table before the check. More specifically for those secondary MMUs which unmap the memory in mmu_notifier_invalidate_range_start() like kvm. However memory reclaim is the only user of !(TTU_IGNORE_ACCESS) or the absence of TTU_IGNORE_ACCESS and it explicitly performs the page table access check before trying to unmap the page. So, at worst the reclaim will miss accesses in a very short window if we remove page table access check in unmapping code. There is an unintented consequence of !(TTU_IGNORE_ACCESS) for the memcg reclaim. From memcg reclaim the page_referenced() only account the accesses from the processes which are in the same memcg of the target page but the unmapping code is considering accesses from all the processes, so, decreasing the effectiveness of memcg reclaim. The simplest solution is to always assume TTU_IGNORE_ACCESS in unmapping code. Link: https://lkml.kernel.org/r/20201104231928.1494083-1-shakeelb@google.com Fixes: 369ea8242c0f ("mm/rmap: update to new mmu_notifier semantic v2") Signed-off-by: Shakeel Butt Acked-by: Johannes Weiner Cc: Hugh Dickins Cc: Jerome Glisse Cc: Vlastimil Babka Cc: Michal Hocko Cc: Andrea Arcangeli Cc: Dan Williams Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/include/linux/rmap.h b/include/linux/rmap.h index 3a6adfa..70085ca 100644 --- a/include/linux/rmap.h +++ b/include/linux/rmap.h @@ -91,7 +91,6 @@ enum ttu_flags { TTU_SPLIT_HUGE_PMD = 0x4, /* split huge PMD if any */ TTU_IGNORE_MLOCK = 0x8, /* ignore mlock */ - TTU_IGNORE_ACCESS = 0x10, /* don't age */ TTU_IGNORE_HWPOISON = 0x20, /* corrupted page is recoverable */ TTU_BATCH_FLUSH = 0x40, /* Batch TLB flushes where possible * and caller guarantees they will diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 42b18d4..c11c800 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2321,7 +2321,7 @@ void vma_adjust_trans_huge(struct vm_area_struct *vma, static void unmap_page(struct page *page) { - enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS | + enum ttu_flags ttu_flags = TTU_IGNORE_MLOCK | TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD; bool unmap_success; diff --git a/mm/memory-failure.c b/mm/memory-failure.c index 5d880d4..71295bb 100644 --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -989,7 +989,7 @@ static int get_hwpoison_page(struct page *page) static bool hwpoison_user_mappings(struct page *p, unsigned long pfn, int flags, struct page **hpagep) { - enum ttu_flags ttu = TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS; + enum ttu_flags ttu = TTU_IGNORE_MLOCK; struct address_space *mapping; LIST_HEAD(tokill); bool unmap_success = true; diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 63b2e46..0f855de 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -1304,7 +1304,7 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn) if (WARN_ON(PageLRU(page))) isolate_lru_page(page); if (page_mapped(page)) - try_to_unmap(page, TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS); + try_to_unmap(page, TTU_IGNORE_MLOCK); continue; } diff --git a/mm/migrate.c b/mm/migrate.c index 5795cb8..8ea0c65 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1122,8 +1122,7 @@ static int __unmap_and_move(struct page *page, struct page *newpage, /* Establish migration ptes */ VM_BUG_ON_PAGE(PageAnon(page) && !PageKsm(page) && !anon_vma, page); - try_to_unmap(page, - TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS); + try_to_unmap(page, TTU_MIGRATION|TTU_IGNORE_MLOCK); page_was_mapped = 1; } @@ -1329,8 +1328,7 @@ static int unmap_and_move_huge_page(new_page_t get_new_page, if (page_mapped(hpage)) { bool mapping_locked = false; - enum ttu_flags ttu = TTU_MIGRATION|TTU_IGNORE_MLOCK| - TTU_IGNORE_ACCESS; + enum ttu_flags ttu = TTU_MIGRATION|TTU_IGNORE_MLOCK; if (!PageAnon(hpage)) { /* @@ -2688,7 +2686,7 @@ static void migrate_vma_prepare(struct migrate_vma *migrate) */ static void migrate_vma_unmap(struct migrate_vma *migrate) { - int flags = TTU_MIGRATION | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS; + int flags = TTU_MIGRATION | TTU_IGNORE_MLOCK; const unsigned long npages = migrate->npages; const unsigned long start = migrate->start; unsigned long addr, i, restore = 0; diff --git a/mm/rmap.c b/mm/rmap.c index 31b2932..6657000 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1533,15 +1533,6 @@ static bool try_to_unmap_one(struct page *page, struct vm_area_struct *vma, goto discard; } - if (!(flags & TTU_IGNORE_ACCESS)) { - if (ptep_clear_flush_young_notify(vma, address, - pvmw.pte)) { - ret = false; - page_vma_mapped_walk_done(&pvmw); - break; - } - } - /* Nuke the page table entry. */ flush_cache_page(vma, address, pte_pfn(*pvmw.pte)); if (should_defer_flush(mm, flags)) { diff --git a/mm/vmscan.c b/mm/vmscan.c index 7b4e31e..0ec6321 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1072,7 +1072,6 @@ static void page_check_dirty_writeback(struct page *page, static unsigned int shrink_page_list(struct list_head *page_list, struct pglist_data *pgdat, struct scan_control *sc, - enum ttu_flags ttu_flags, struct reclaim_stat *stat, bool ignore_references) { @@ -1297,7 +1296,7 @@ static unsigned int shrink_page_list(struct list_head *page_list, * processes. Try to unmap it here. */ if (page_mapped(page)) { - enum ttu_flags flags = ttu_flags | TTU_BATCH_FLUSH; + enum ttu_flags flags = TTU_BATCH_FLUSH; bool was_swapbacked = PageSwapBacked(page); if (unlikely(PageTransHuge(page))) @@ -1514,7 +1513,7 @@ unsigned int reclaim_clean_pages_from_list(struct zone *zone, } nr_reclaimed = shrink_page_list(&clean_pages, zone->zone_pgdat, &sc, - TTU_IGNORE_ACCESS, &stat, true); + &stat, true); list_splice(&clean_pages, page_list); mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE, -(long)nr_reclaimed); @@ -1958,8 +1957,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec, if (nr_taken == 0) return 0; - nr_reclaimed = shrink_page_list(&page_list, pgdat, sc, 0, - &stat, false); + nr_reclaimed = shrink_page_list(&page_list, pgdat, sc, &stat, false); spin_lock_irq(&pgdat->lru_lock); @@ -2131,8 +2129,7 @@ unsigned long reclaim_pages(struct list_head *page_list) nr_reclaimed += shrink_page_list(&node_page_list, NODE_DATA(nid), - &sc, 0, - &dummy_stat, false); + &sc, &dummy_stat, false); while (!list_empty(&node_page_list)) { page = lru_to_page(&node_page_list); list_del(&page->lru); @@ -2145,8 +2142,7 @@ unsigned long reclaim_pages(struct list_head *page_list) if (!list_empty(&node_page_list)) { nr_reclaimed += shrink_page_list(&node_page_list, NODE_DATA(nid), - &sc, 0, - &dummy_stat, false); + &sc, &dummy_stat, false); while (!list_empty(&node_page_list)) { page = lru_to_page(&node_page_list); list_del(&page->lru);