X-Git-Url: http://drtracing.org/?a=blobdiff_plain;f=mm%2Fhuge_memory.c;h=fbfb1b8d67260941b05ce7e6c8d04b81e65ee1d1;hb=3f2b1a04f44933f2d6fe0a9bf9a9c1c452df23f7;hp=1ea21e203a700114587dedca262f9267bb5a005a;hpb=9cc984e4bc089cd21b715b92ffe2d2bda0bb1d1a;p=deliverable%2Flinux.git diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 1ea21e203a70..fbfb1b8d6726 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -78,12 +78,12 @@ unsigned long transparent_hugepage_flags __read_mostly = #ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE (1< min_free_kbytes) { if (user_min_free_kbytes >= 0) - pr_info("raising min_free_kbytes from %d to %lu " - "to help transparent hugepage allocations\n", + pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n", min_free_kbytes, recommended_min); min_free_kbytes = recommended_min; @@ -270,37 +269,35 @@ static struct shrinker huge_zero_page_shrinker = { #ifdef CONFIG_SYSFS -static ssize_t double_flag_show(struct kobject *kobj, - struct kobj_attribute *attr, char *buf, - enum transparent_hugepage_flag enabled, - enum transparent_hugepage_flag req_madv) -{ - if (test_bit(enabled, &transparent_hugepage_flags)) { - VM_BUG_ON(test_bit(req_madv, &transparent_hugepage_flags)); - return sprintf(buf, "[always] madvise never\n"); - } else if (test_bit(req_madv, &transparent_hugepage_flags)) - return sprintf(buf, "always [madvise] never\n"); - else - return sprintf(buf, "always madvise [never]\n"); -} -static ssize_t double_flag_store(struct kobject *kobj, +static ssize_t triple_flag_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t count, enum transparent_hugepage_flag enabled, + enum transparent_hugepage_flag deferred, enum transparent_hugepage_flag req_madv) { - if (!memcmp("always", buf, + if (!memcmp("defer", buf, + min(sizeof("defer")-1, count))) { + if (enabled == deferred) + return -EINVAL; + clear_bit(enabled, &transparent_hugepage_flags); + clear_bit(req_madv, &transparent_hugepage_flags); + set_bit(deferred, &transparent_hugepage_flags); + } else if (!memcmp("always", buf, min(sizeof("always")-1, count))) { - set_bit(enabled, &transparent_hugepage_flags); + clear_bit(deferred, &transparent_hugepage_flags); clear_bit(req_madv, &transparent_hugepage_flags); + set_bit(enabled, &transparent_hugepage_flags); } else if (!memcmp("madvise", buf, min(sizeof("madvise")-1, count))) { clear_bit(enabled, &transparent_hugepage_flags); + clear_bit(deferred, &transparent_hugepage_flags); set_bit(req_madv, &transparent_hugepage_flags); } else if (!memcmp("never", buf, min(sizeof("never")-1, count))) { clear_bit(enabled, &transparent_hugepage_flags); clear_bit(req_madv, &transparent_hugepage_flags); + clear_bit(deferred, &transparent_hugepage_flags); } else return -EINVAL; @@ -310,17 +307,22 @@ static ssize_t double_flag_store(struct kobject *kobj, static ssize_t enabled_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { - return double_flag_show(kobj, attr, buf, - TRANSPARENT_HUGEPAGE_FLAG, - TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG); + if (test_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags)) + return sprintf(buf, "[always] madvise never\n"); + else if (test_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags)) + return sprintf(buf, "always [madvise] never\n"); + else + return sprintf(buf, "always madvise [never]\n"); } + static ssize_t enabled_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t count) { ssize_t ret; - ret = double_flag_store(kobj, attr, buf, count, + ret = triple_flag_store(kobj, attr, buf, count, + TRANSPARENT_HUGEPAGE_FLAG, TRANSPARENT_HUGEPAGE_FLAG, TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG); @@ -378,16 +380,23 @@ static ssize_t single_flag_store(struct kobject *kobj, static ssize_t defrag_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { - return double_flag_show(kobj, attr, buf, - TRANSPARENT_HUGEPAGE_DEFRAG_FLAG, - TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG); + if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags)) + return sprintf(buf, "[always] defer madvise never\n"); + if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags)) + return sprintf(buf, "always [defer] madvise never\n"); + else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags)) + return sprintf(buf, "always defer [madvise] never\n"); + else + return sprintf(buf, "always defer madvise [never]\n"); + } static ssize_t defrag_store(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t count) { - return double_flag_store(kobj, attr, buf, count, - TRANSPARENT_HUGEPAGE_DEFRAG_FLAG, + return triple_flag_store(kobj, attr, buf, count, + TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, + TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG); } static struct kobj_attribute defrag_attr = @@ -660,6 +669,18 @@ static int __init hugepage_init(void) return -EINVAL; } + khugepaged_pages_to_scan = HPAGE_PMD_NR * 8; + khugepaged_max_ptes_none = HPAGE_PMD_NR - 1; + /* + * hugepages can't be allocated by the buddy allocator + */ + MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER >= MAX_ORDER); + /* + * we use page->mapping and page->index in second tail page + * as list_head: assuming THP order >= 2 + */ + MAYBE_BUILD_BUG_ON(HPAGE_PMD_ORDER < 2); + err = hugepage_init_sysfs(&hugepage_kobj); if (err) goto err_sysfs; @@ -764,7 +785,6 @@ void prep_transhuge_page(struct page *page) * we use page->mapping and page->indexlru in second tail page * as list_head: assuming THP order >= 2 */ - BUILD_BUG_ON(HPAGE_PMD_ORDER < 2); INIT_LIST_HEAD(page_deferred_list(page)); set_compound_page_dtor(page, TRANSHUGE_PAGE_DTOR); @@ -843,9 +863,30 @@ static int __do_huge_pmd_anonymous_page(struct mm_struct *mm, return 0; } -static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp) +/* + * If THP is set to always then directly reclaim/compact as necessary + * If set to defer then do no reclaim and defer to khugepaged + * If set to madvise and the VMA is flagged then directly reclaim/compact + */ +static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma) { - return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_RECLAIM)) | extra_gfp; + gfp_t reclaim_flags = 0; + + if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags) && + (vma->vm_flags & VM_HUGEPAGE)) + reclaim_flags = __GFP_DIRECT_RECLAIM; + else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags)) + reclaim_flags = __GFP_KSWAPD_RECLAIM; + else if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags)) + reclaim_flags = __GFP_DIRECT_RECLAIM; + + return GFP_TRANSHUGE | reclaim_flags; +} + +/* Defrag for khugepaged will enter direct reclaim/compaction if necessary */ +static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void) +{ + return GFP_TRANSHUGE | (khugepaged_defrag() ? __GFP_DIRECT_RECLAIM : 0); } /* Caller must hold page table lock. */ @@ -919,7 +960,7 @@ int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, } return ret; } - gfp = alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma), 0); + gfp = alloc_hugepage_direct_gfpmask(vma); page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER); if (unlikely(!page)) { count_vm_event(THP_FAULT_FALLBACK); @@ -1279,7 +1320,7 @@ int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, alloc: if (transparent_hugepage_enabled(vma) && !transparent_hugepage_debug_cow()) { - huge_gfp = alloc_hugepage_gfpmask(transparent_hugepage_defrag(vma), 0); + huge_gfp = alloc_hugepage_direct_gfpmask(vma); new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER); } else new_page = NULL; @@ -2249,11 +2290,12 @@ static int khugepaged_find_target_node(void) return 0; } -static inline struct page *alloc_hugepage(int defrag) +static inline struct page *alloc_khugepaged_hugepage(void) { struct page *page; - page = alloc_pages(alloc_hugepage_gfpmask(defrag, 0), HPAGE_PMD_ORDER); + page = alloc_pages(alloc_hugepage_khugepaged_gfpmask(), + HPAGE_PMD_ORDER); if (page) prep_transhuge_page(page); return page; @@ -2264,7 +2306,7 @@ static struct page *khugepaged_alloc_hugepage(bool *wait) struct page *hpage; do { - hpage = alloc_hugepage(khugepaged_defrag()); + hpage = alloc_khugepaged_hugepage(); if (!hpage) { count_vm_event(THP_COLLAPSE_ALLOC_FAILED); if (!*wait) @@ -2335,8 +2377,7 @@ static void collapse_huge_page(struct mm_struct *mm, VM_BUG_ON(address & ~HPAGE_PMD_MASK); /* Only allocate from the target node */ - gfp = alloc_hugepage_gfpmask(khugepaged_defrag(), __GFP_OTHER_NODE) | - __GFP_THISNODE; + gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_OTHER_NODE | __GFP_THISNODE; /* release the mmap_sem read lock. */ new_page = khugepaged_alloc_page(hpage, gfp, mm, address, node); @@ -2857,7 +2898,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, page = pmd_page(*pmd); VM_BUG_ON_PAGE(!page_count(page), page); - atomic_add(HPAGE_PMD_NR - 1, &page->_count); + page_ref_add(page, HPAGE_PMD_NR - 1); write = pmd_write(*pmd); young = pmd_young(*pmd); dirty = pmd_dirty(*pmd); @@ -2947,44 +2988,33 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, } void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, - unsigned long address) + unsigned long address, bool freeze) { spinlock_t *ptl; struct mm_struct *mm = vma->vm_mm; - struct page *page = NULL; unsigned long haddr = address & HPAGE_PMD_MASK; mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE); ptl = pmd_lock(mm, pmd); if (pmd_trans_huge(*pmd)) { - page = pmd_page(*pmd); + struct page *page = pmd_page(*pmd); if (PageMlocked(page)) - get_page(page); - else - page = NULL; + clear_page_mlock(page); } else if (!pmd_devmap(*pmd)) goto out; - __split_huge_pmd_locked(vma, pmd, haddr, false); + __split_huge_pmd_locked(vma, pmd, haddr, freeze); out: spin_unlock(ptl); mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE); - if (page) { - lock_page(page); - munlock_vma_page(page); - unlock_page(page); - put_page(page); - } } -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, + bool freeze, struct page *page) { 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; @@ -2996,11 +3026,20 @@ static void split_huge_pmd_address(struct vm_area_struct *vma, pmd = pmd_offset(pud, address); if (!pmd_present(*pmd) || (!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd))) return; + + /* + * If caller asks to setup a migration entries, we need a page to check + * pmd against. Otherwise we can end up replacing wrong page. + */ + VM_BUG_ON(freeze && !page); + if (page && page != pmd_page(*pmd)) + return; + /* * Caller holds the mmap_sem write mode, so a huge pmd cannot * materialize from under us. */ - split_huge_pmd(vma, pmd, address); + __split_huge_pmd(vma, pmd, address, freeze); } void vma_adjust_trans_huge(struct vm_area_struct *vma, @@ -3016,7 +3055,7 @@ void vma_adjust_trans_huge(struct vm_area_struct *vma, if (start & ~HPAGE_PMD_MASK && (start & HPAGE_PMD_MASK) >= vma->vm_start && (start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) - split_huge_pmd_address(vma, start); + split_huge_pmd_address(vma, start, false, NULL); /* * If the new end address isn't hpage aligned and it could @@ -3026,7 +3065,7 @@ void vma_adjust_trans_huge(struct vm_area_struct *vma, if (end & ~HPAGE_PMD_MASK && (end & HPAGE_PMD_MASK) >= vma->vm_start && (end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end) - split_huge_pmd_address(vma, end); + split_huge_pmd_address(vma, end, false, NULL); /* * If we're also updating the vma->vm_next->vm_start, if the new @@ -3040,184 +3079,36 @@ void vma_adjust_trans_huge(struct vm_area_struct *vma, if (nstart & ~HPAGE_PMD_MASK && (nstart & HPAGE_PMD_MASK) >= next->vm_start && (nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end) - split_huge_pmd_address(next, nstart); + split_huge_pmd_address(next, nstart, false, NULL); } } -static void freeze_page_vma(struct vm_area_struct *vma, struct page *page, - unsigned long address) +static void freeze_page(struct page *page) { - unsigned long haddr = address & HPAGE_PMD_MASK; - spinlock_t *ptl; - pgd_t *pgd; - pud_t *pud; - pmd_t *pmd; - pte_t *pte; - int i, nr = HPAGE_PMD_NR; - - /* Skip pages which doesn't belong to the VMA */ - if (address < vma->vm_start) { - int off = (vma->vm_start - address) >> PAGE_SHIFT; - page += off; - nr -= off; - address = vma->vm_start; - } - - pgd = pgd_offset(vma->vm_mm, address); - if (!pgd_present(*pgd)) - return; - pud = pud_offset(pgd, address); - if (!pud_present(*pud)) - return; - pmd = pmd_offset(pud, address); - ptl = pmd_lock(vma->vm_mm, pmd); - if (!pmd_present(*pmd)) { - spin_unlock(ptl); - return; - } - if (pmd_trans_huge(*pmd)) { - if (page == pmd_page(*pmd)) - __split_huge_pmd_locked(vma, pmd, haddr, true); - spin_unlock(ptl); - return; - } - spin_unlock(ptl); - - pte = pte_offset_map_lock(vma->vm_mm, pmd, address, &ptl); - for (i = 0; i < nr; i++, address += PAGE_SIZE, page++, pte++) { - pte_t entry, swp_pte; - swp_entry_t swp_entry; - - /* - * We've just crossed page table boundary: need to map next one. - * It can happen if THP was mremaped to non PMD-aligned address. - */ - if (unlikely(address == haddr + HPAGE_PMD_SIZE)) { - pte_unmap_unlock(pte - 1, ptl); - pmd = mm_find_pmd(vma->vm_mm, address); - if (!pmd) - return; - pte = pte_offset_map_lock(vma->vm_mm, pmd, - address, &ptl); - } - - if (!pte_present(*pte)) - continue; - if (page_to_pfn(page) != pte_pfn(*pte)) - continue; - flush_cache_page(vma, address, page_to_pfn(page)); - entry = ptep_clear_flush(vma, address, pte); - if (pte_dirty(entry)) - SetPageDirty(page); - swp_entry = make_migration_entry(page, pte_write(entry)); - swp_pte = swp_entry_to_pte(swp_entry); - if (pte_soft_dirty(entry)) - swp_pte = pte_swp_mksoft_dirty(swp_pte); - set_pte_at(vma->vm_mm, address, pte, swp_pte); - page_remove_rmap(page, false); - put_page(page); - } - pte_unmap_unlock(pte - 1, ptl); -} - -static void freeze_page(struct anon_vma *anon_vma, struct page *page) -{ - struct anon_vma_chain *avc; - pgoff_t pgoff = page_to_pgoff(page); + enum ttu_flags ttu_flags = TTU_MIGRATION | TTU_IGNORE_MLOCK | + TTU_IGNORE_ACCESS | TTU_RMAP_LOCKED; + int i, ret; VM_BUG_ON_PAGE(!PageHead(page), page); - anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, - pgoff + HPAGE_PMD_NR - 1) { - unsigned long address = __vma_address(page, avc->vma); - - mmu_notifier_invalidate_range_start(avc->vma->vm_mm, - address, address + HPAGE_PMD_SIZE); - freeze_page_vma(avc->vma, page, address); - mmu_notifier_invalidate_range_end(avc->vma->vm_mm, - address, address + HPAGE_PMD_SIZE); - } -} - -static void unfreeze_page_vma(struct vm_area_struct *vma, struct page *page, - unsigned long address) -{ - spinlock_t *ptl; - pmd_t *pmd; - pte_t *pte, entry; - swp_entry_t swp_entry; - unsigned long haddr = address & HPAGE_PMD_MASK; - int i, nr = HPAGE_PMD_NR; - - /* Skip pages which doesn't belong to the VMA */ - if (address < vma->vm_start) { - int off = (vma->vm_start - address) >> PAGE_SHIFT; - page += off; - nr -= off; - address = vma->vm_start; - } - - pmd = mm_find_pmd(vma->vm_mm, address); - if (!pmd) - return; - - pte = pte_offset_map_lock(vma->vm_mm, pmd, address, &ptl); - for (i = 0; i < nr; i++, address += PAGE_SIZE, page++, pte++) { - /* - * We've just crossed page table boundary: need to map next one. - * It can happen if THP was mremaped to non-PMD aligned address. - */ - if (unlikely(address == haddr + HPAGE_PMD_SIZE)) { - pte_unmap_unlock(pte - 1, ptl); - pmd = mm_find_pmd(vma->vm_mm, address); - if (!pmd) - return; - pte = pte_offset_map_lock(vma->vm_mm, pmd, - address, &ptl); - } - - if (!is_swap_pte(*pte)) - continue; - - swp_entry = pte_to_swp_entry(*pte); - if (!is_migration_entry(swp_entry)) - continue; - if (migration_entry_to_page(swp_entry) != page) - continue; - - get_page(page); - page_add_anon_rmap(page, vma, address, false); - - entry = pte_mkold(mk_pte(page, vma->vm_page_prot)); - if (PageDirty(page)) - entry = pte_mkdirty(entry); - if (is_write_migration_entry(swp_entry)) - entry = maybe_mkwrite(entry, vma); - - flush_dcache_page(page); - set_pte_at(vma->vm_mm, address, pte, entry); + /* We only need TTU_SPLIT_HUGE_PMD once */ + ret = try_to_unmap(page, ttu_flags | TTU_SPLIT_HUGE_PMD); + for (i = 1; !ret && i < HPAGE_PMD_NR; i++) { + /* Cut short if the page is unmapped */ + if (page_count(page) == 1) + return; - /* No need to invalidate - it was non-present before */ - update_mmu_cache(vma, address, pte); + ret = try_to_unmap(page + i, ttu_flags); } - pte_unmap_unlock(pte - 1, ptl); + VM_BUG_ON(ret); } -static void unfreeze_page(struct anon_vma *anon_vma, struct page *page) +static void unfreeze_page(struct page *page) { - struct anon_vma_chain *avc; - pgoff_t pgoff = page_to_pgoff(page); - - anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, - pgoff, pgoff + HPAGE_PMD_NR - 1) { - unsigned long address = __vma_address(page, avc->vma); + int i; - mmu_notifier_invalidate_range_start(avc->vma->vm_mm, - address, address + HPAGE_PMD_SIZE); - unfreeze_page_vma(avc->vma, page, address); - mmu_notifier_invalidate_range_end(avc->vma->vm_mm, - address, address + HPAGE_PMD_SIZE); - } + for (i = 0; i < HPAGE_PMD_NR; i++) + remove_migration_ptes(page + i, page + i, true); } static void __split_huge_page_tail(struct page *head, int tail, @@ -3226,7 +3117,7 @@ static void __split_huge_page_tail(struct page *head, int tail, struct page *page_tail = head + tail; VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail); - VM_BUG_ON_PAGE(atomic_read(&page_tail->_count) != 0, page_tail); + VM_BUG_ON_PAGE(page_ref_count(page_tail) != 0, page_tail); /* * tail_page->_count is zero and not changing from under us. But @@ -3239,7 +3130,7 @@ static void __split_huge_page_tail(struct page *head, int tail, * atomic_set() here would be safe on all archs (and not only on x86), * it's safer to use atomic_inc(). */ - atomic_inc(&page_tail->_count); + page_ref_inc(page_tail); page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP; page_tail->flags |= (head->flags & @@ -3295,7 +3186,7 @@ static void __split_huge_page(struct page *page, struct list_head *list) ClearPageCompound(head); spin_unlock_irq(&zone->lru_lock); - unfreeze_page(page_anon_vma(head), head); + unfreeze_page(head); for (i = 0; i < HPAGE_PMD_NR; i++) { struct page *subpage = head + i; @@ -3391,7 +3282,7 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) } mlocked = PageMlocked(page); - freeze_page(anon_vma, head); + freeze_page(head); VM_BUG_ON_PAGE(compound_mapcount(head), head); /* Make sure the page is not on per-CPU pagevec as it takes pin */ @@ -3420,7 +3311,7 @@ int split_huge_page_to_list(struct page *page, struct list_head *list) BUG(); } else { spin_unlock_irqrestore(&pgdata->split_queue_lock, flags); - unfreeze_page(anon_vma, head); + unfreeze_page(head); ret = -EBUSY; } @@ -3455,6 +3346,7 @@ void deferred_split_huge_page(struct page *page) spin_lock_irqsave(&pgdata->split_queue_lock, flags); if (list_empty(page_deferred_list(page))) { + count_vm_event(THP_DEFERRED_SPLIT_PAGE); list_add_tail(page_deferred_list(page), &pgdata->split_queue); pgdata->split_queue_len++; }