From 2a52bcbcc688eecead2953143f7ef695b8e44575 Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" Date: Thu, 17 Mar 2016 14:20:04 -0700 Subject: [PATCH] rmap: extend try_to_unmap() to be usable by split_huge_page() Add support for two ttu_flags: - TTU_SPLIT_HUGE_PMD would split PMD if it's there, before trying to unmap page; - TTU_RMAP_LOCKED indicates that caller holds relevant rmap lock; Also, change rwc->done to !page_mapcount() instead of !page_mapped(). try_to_unmap() works on pte level, so we are really interested in the mappedness of this small page rather than of the compound page it's a part of. Signed-off-by: Kirill A. Shutemov Cc: Andrea Arcangeli Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/huge_mm.h | 7 +++++++ include/linux/rmap.h | 3 +++ mm/huge_memory.c | 5 +---- mm/rmap.c | 24 ++++++++++++++++-------- 4 files changed, 27 insertions(+), 12 deletions(-) diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h index a4cecb4801ec..01ad22e938b0 100644 --- a/include/linux/huge_mm.h +++ b/include/linux/huge_mm.h @@ -106,6 +106,9 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, __split_huge_pmd(__vma, __pmd, __address); \ } while (0) + +void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address); + #if HPAGE_PMD_ORDER >= MAX_ORDER #error "hugepages can't be allocated by the buddy allocator" #endif @@ -173,6 +176,10 @@ static inline int split_huge_page(struct page *page) static inline void deferred_split_huge_page(struct page *page) {} #define split_huge_pmd(__vma, __pmd, __address) \ do { } while (0) + +static inline void split_huge_pmd_address(struct vm_area_struct *vma, + unsigned long address) {} + static inline int hugepage_madvise(struct vm_area_struct *vma, unsigned long *vm_flags, int advice) { diff --git a/include/linux/rmap.h b/include/linux/rmap.h index a5875e9b4a27..3d975e2252d4 100644 --- a/include/linux/rmap.h +++ b/include/linux/rmap.h @@ -86,6 +86,7 @@ enum ttu_flags { TTU_MIGRATION = 2, /* migration mode */ TTU_MUNLOCK = 4, /* munlock mode */ TTU_LZFREE = 8, /* lazy free mode */ + TTU_SPLIT_HUGE_PMD = 16, /* split huge PMD if any */ TTU_IGNORE_MLOCK = (1 << 8), /* ignore mlock */ TTU_IGNORE_ACCESS = (1 << 9), /* don't age */ @@ -93,6 +94,8 @@ enum ttu_flags { TTU_BATCH_FLUSH = (1 << 11), /* Batch TLB flushes where possible * and caller guarantees they will * do a final flush if necessary */ + TTU_RMAP_LOCKED = (1 << 12) /* do not grab rmap lock: + * caller holds it */ }; #ifdef CONFIG_MMU diff --git a/mm/huge_memory.c b/mm/huge_memory.c index e1a177c20791..11d15674ff38 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -3006,15 +3006,12 @@ out: } } -static void split_huge_pmd_address(struct vm_area_struct *vma, - unsigned long address) +void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address) { pgd_t *pgd; pud_t *pud; pmd_t *pmd; - VM_BUG_ON(!(address & ~HPAGE_PMD_MASK)); - pgd = pgd_offset(vma->vm_mm, address); if (!pgd_present(*pgd)) return; diff --git a/mm/rmap.c b/mm/rmap.c index 30b739ce0ffa..945933a01010 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1431,6 +1431,8 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, if ((flags & TTU_MUNLOCK) && !(vma->vm_flags & VM_LOCKED)) goto out; + if (flags & TTU_SPLIT_HUGE_PMD) + split_huge_pmd_address(vma, address); pte = page_check_address(page, mm, address, &ptl, 0); if (!pte) goto out; @@ -1576,10 +1578,10 @@ static bool invalid_migration_vma(struct vm_area_struct *vma, void *arg) return is_vma_temporary_stack(vma); } -static int page_not_mapped(struct page *page) +static int page_mapcount_is_zero(struct page *page) { - return !page_mapped(page); -}; + return !page_mapcount(page); +} /** * try_to_unmap - try to remove all page table mappings to a page @@ -1606,12 +1608,10 @@ int try_to_unmap(struct page *page, enum ttu_flags flags) struct rmap_walk_control rwc = { .rmap_one = try_to_unmap_one, .arg = &rp, - .done = page_not_mapped, + .done = page_mapcount_is_zero, .anon_lock = page_lock_anon_vma_read, }; - VM_BUG_ON_PAGE(!PageHuge(page) && PageTransHuge(page), page); - /* * During exec, a temporary VMA is setup and later moved. * The VMA is moved under the anon_vma lock but not the @@ -1623,9 +1623,12 @@ int try_to_unmap(struct page *page, enum ttu_flags flags) if ((flags & TTU_MIGRATION) && !PageKsm(page) && PageAnon(page)) rwc.invalid_vma = invalid_migration_vma; - ret = rmap_walk(page, &rwc); + if (flags & TTU_RMAP_LOCKED) + ret = rmap_walk_locked(page, &rwc); + else + ret = rmap_walk(page, &rwc); - if (ret != SWAP_MLOCK && !page_mapped(page)) { + if (ret != SWAP_MLOCK && !page_mapcount(page)) { ret = SWAP_SUCCESS; if (rp.lazyfreed && !PageDirty(page)) ret = SWAP_LZFREE; @@ -1633,6 +1636,11 @@ int try_to_unmap(struct page *page, enum ttu_flags flags) return ret; } +static int page_not_mapped(struct page *page) +{ + return !page_mapped(page); +}; + /** * try_to_munlock - try to munlock a page * @page: the page to be munlocked