From ba3c4ce6def4915093be80585ff69f780630f32f Mon Sep 17 00:00:00 2001 From: Huang Ying Date: Wed, 6 Sep 2017 16:22:19 -0700 Subject: [PATCH] mm, THP, swap: make reuse_swap_page() works for THP swapped out After supporting to delay THP (Transparent Huge Page) splitting after swapped out, it is possible that some page table mappings of the THP are turned into swap entries. So reuse_swap_page() need to check the swap count in addition to the map count as before. This patch done that. In the huge PMD write protect fault handler, in addition to the page map count, the swap count need to be checked too, so the page lock need to be acquired too when calling reuse_swap_page() in addition to the page table lock. [ying.huang@intel.com: silence a compiler warning] Link: http://lkml.kernel.org/r/87bmnzizjy.fsf@yhuang-dev.intel.com Link: http://lkml.kernel.org/r/20170724051840.2309-4-ying.huang@intel.com Signed-off-by: "Huang, Ying" Cc: Johannes Weiner Cc: Minchan Kim Cc: Hugh Dickins Cc: Shaohua Li Cc: Rik van Riel Cc: Andrea Arcangeli Cc: "Kirill A . Shutemov" Cc: Dan Williams Cc: Jens Axboe Cc: Michal Hocko Cc: Ross Zwisler [for brd.c, zram_drv.c, pmem.c] Cc: Vishal L Verma Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/swap.h | 4 +- mm/huge_memory.c | 16 ++++++- mm/memory.c | 6 +-- mm/swapfile.c | 102 +++++++++++++++++++++++++++++++++++++++---- 4 files changed, 113 insertions(+), 15 deletions(-) diff --git a/include/linux/swap.h b/include/linux/swap.h index 964b4f1fba4a..7176ba780e83 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -510,8 +510,8 @@ static inline int swp_swapcount(swp_entry_t entry) return 0; } -#define reuse_swap_page(page, total_mapcount) \ - (page_trans_huge_mapcount(page, total_mapcount) == 1) +#define reuse_swap_page(page, total_map_swapcount) \ + (page_trans_huge_mapcount(page, total_map_swapcount) == 1) static inline int try_to_free_swap(struct page *page) { diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 7f0b3f6db923..02dfe635c9fe 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1240,15 +1240,29 @@ int do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd) * We can only reuse the page if nobody else maps the huge page or it's * part. */ - if (page_trans_huge_mapcount(page, NULL) == 1) { + if (!trylock_page(page)) { + get_page(page); + spin_unlock(vmf->ptl); + lock_page(page); + spin_lock(vmf->ptl); + if (unlikely(!pmd_same(*vmf->pmd, orig_pmd))) { + unlock_page(page); + put_page(page); + goto out_unlock; + } + put_page(page); + } + if (reuse_swap_page(page, NULL)) { pmd_t entry; entry = pmd_mkyoung(orig_pmd); entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); if (pmdp_set_access_flags(vma, haddr, vmf->pmd, entry, 1)) update_mmu_cache_pmd(vma, vmf->address, vmf->pmd); ret |= VM_FAULT_WRITE; + unlock_page(page); goto out_unlock; } + unlock_page(page); get_page(page); spin_unlock(vmf->ptl); alloc: diff --git a/mm/memory.c b/mm/memory.c index 1416485e278c..3dd8bb46391b 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2619,7 +2619,7 @@ static int do_wp_page(struct vm_fault *vmf) * not dirty accountable. */ if (PageAnon(vmf->page) && !PageKsm(vmf->page)) { - int total_mapcount; + int total_map_swapcount; if (!trylock_page(vmf->page)) { get_page(vmf->page); pte_unmap_unlock(vmf->pte, vmf->ptl); @@ -2634,8 +2634,8 @@ static int do_wp_page(struct vm_fault *vmf) } put_page(vmf->page); } - if (reuse_swap_page(vmf->page, &total_mapcount)) { - if (total_mapcount == 1) { + if (reuse_swap_page(vmf->page, &total_map_swapcount)) { + if (total_map_swapcount == 1) { /* * The page is all ours. Move it to * our anon_vma so the rmap code will diff --git a/mm/swapfile.c b/mm/swapfile.c index 164d9624d7d2..2bfbfb87123a 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -1405,9 +1405,89 @@ static bool page_swapped(struct page *page) return swap_page_trans_huge_swapped(si, entry); return false; } + +static int page_trans_huge_map_swapcount(struct page *page, int *total_mapcount, + int *total_swapcount) +{ + int i, map_swapcount, _total_mapcount, _total_swapcount; + unsigned long offset = 0; + struct swap_info_struct *si; + struct swap_cluster_info *ci = NULL; + unsigned char *map = NULL; + int mapcount, swapcount = 0; + + /* hugetlbfs shouldn't call it */ + VM_BUG_ON_PAGE(PageHuge(page), page); + + if (likely(!PageTransCompound(page))) { + mapcount = atomic_read(&page->_mapcount) + 1; + if (total_mapcount) + *total_mapcount = mapcount; + if (PageSwapCache(page)) + swapcount = page_swapcount(page); + if (total_swapcount) + *total_swapcount = swapcount; + return mapcount + swapcount; + } + + page = compound_head(page); + + _total_mapcount = _total_swapcount = map_swapcount = 0; + if (PageSwapCache(page)) { + swp_entry_t entry; + + entry.val = page_private(page); + si = _swap_info_get(entry); + if (si) { + map = si->swap_map; + offset = swp_offset(entry); + } + } + if (map) + ci = lock_cluster(si, offset); + for (i = 0; i < HPAGE_PMD_NR; i++) { + mapcount = atomic_read(&page[i]._mapcount) + 1; + _total_mapcount += mapcount; + if (map) { + swapcount = swap_count(map[offset + i]); + _total_swapcount += swapcount; + } + map_swapcount = max(map_swapcount, mapcount + swapcount); + } + unlock_cluster(ci); + if (PageDoubleMap(page)) { + map_swapcount -= 1; + _total_mapcount -= HPAGE_PMD_NR; + } + mapcount = compound_mapcount(page); + map_swapcount += mapcount; + _total_mapcount += mapcount; + if (total_mapcount) + *total_mapcount = _total_mapcount; + if (total_swapcount) + *total_swapcount = _total_swapcount; + + return map_swapcount; +} #else #define swap_page_trans_huge_swapped(si, entry) swap_swapcount(si, entry) #define page_swapped(page) (page_swapcount(page) != 0) + +static int page_trans_huge_map_swapcount(struct page *page, int *total_mapcount, + int *total_swapcount) +{ + int mapcount, swapcount = 0; + + /* hugetlbfs shouldn't call it */ + VM_BUG_ON_PAGE(PageHuge(page), page); + + mapcount = page_trans_huge_mapcount(page, total_mapcount); + if (PageSwapCache(page)) + swapcount = page_swapcount(page); + if (total_swapcount) + *total_swapcount = swapcount; + return mapcount + swapcount; +} #endif /* @@ -1416,23 +1496,27 @@ static bool page_swapped(struct page *page) * on disk will never be read, and seeking back there to write new content * later would only waste time away from clustering. * - * NOTE: total_mapcount should not be relied upon by the caller if + * NOTE: total_map_swapcount should not be relied upon by the caller if * reuse_swap_page() returns false, but it may be always overwritten * (see the other implementation for CONFIG_SWAP=n). */ -bool reuse_swap_page(struct page *page, int *total_mapcount) +bool reuse_swap_page(struct page *page, int *total_map_swapcount) { - int count; + int count, total_mapcount, total_swapcount; VM_BUG_ON_PAGE(!PageLocked(page), page); if (unlikely(PageKsm(page))) return false; - count = page_trans_huge_mapcount(page, total_mapcount); - if (count <= 1 && PageSwapCache(page)) { - count += page_swapcount(page); - if (count != 1) - goto out; + count = page_trans_huge_map_swapcount(page, &total_mapcount, + &total_swapcount); + if (total_map_swapcount) + *total_map_swapcount = total_mapcount + total_swapcount; + if (count == 1 && PageSwapCache(page) && + (likely(!PageTransCompound(page)) || + /* The remaining swap count will be freed soon */ + total_swapcount == page_swapcount(page))) { if (!PageWriteback(page)) { + page = compound_head(page); delete_from_swap_cache(page); SetPageDirty(page); } else { @@ -1448,7 +1532,7 @@ bool reuse_swap_page(struct page *page, int *total_mapcount) spin_unlock(&p->lock); } } -out: + return count <= 1; } -- 2.34.1