From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752677AbcKQX4b (ORCPT ); Thu, 17 Nov 2016 18:56:31 -0500 Received: from mail-wm0-f68.google.com ([74.125.82.68]:34257 "EHLO mail-wm0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752173AbcKQX42 (ORCPT ); Thu, 17 Nov 2016 18:56:28 -0500 Date: Fri, 18 Nov 2016 02:56:24 +0300 From: "Kirill A. Shutemov" To: Naoya Horiguchi Cc: linux-mm@kvack.org, "Kirill A. Shutemov" , Hugh Dickins , Andrew Morton , Dave Hansen , Andrea Arcangeli , Mel Gorman , Michal Hocko , Vlastimil Babka , Pavel Emelyanov , Zi Yan , Balbir Singh , linux-kernel@vger.kernel.org, Naoya Horiguchi Subject: Re: [PATCH v2 07/12] mm: thp: check pmd migration entry in common path Message-ID: <20161117235624.GA8891@node> References: <1478561517-4317-1-git-send-email-n-horiguchi@ah.jp.nec.com> <1478561517-4317-8-git-send-email-n-horiguchi@ah.jp.nec.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1478561517-4317-8-git-send-email-n-horiguchi@ah.jp.nec.com> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 08, 2016 at 08:31:52AM +0900, Naoya Horiguchi wrote: > If one of callers of page migration starts to handle thp, memory management code > start to see pmd migration entry, so we need to prepare for it before enabling. > This patch changes various code point which checks the status of given pmds in > order to prevent race between thp migration and the pmd-related works. > > Signed-off-by: Naoya Horiguchi > --- > ChangeLog v1 -> v2: > - introduce pmd_related() (I know the naming is not good, but can't think up > no better name. Any suggesntion is welcomed.) > --- > arch/x86/mm/gup.c | 4 +-- > fs/proc/task_mmu.c | 23 +++++++------ > include/linux/huge_mm.h | 9 ++++- > mm/gup.c | 10 ++++-- > mm/huge_memory.c | 88 ++++++++++++++++++++++++++++++++++++++++--------- > mm/madvise.c | 2 +- > mm/memcontrol.c | 2 ++ > mm/memory.c | 6 +++- > mm/mprotect.c | 2 ++ > mm/mremap.c | 2 +- > 10 files changed, 114 insertions(+), 34 deletions(-) > > diff --git v4.9-rc2-mmotm-2016-10-27-18-27/arch/x86/mm/gup.c v4.9-rc2-mmotm-2016-10-27-18-27_patched/arch/x86/mm/gup.c > index 0d4fb3e..78a153d 100644 > --- v4.9-rc2-mmotm-2016-10-27-18-27/arch/x86/mm/gup.c > +++ v4.9-rc2-mmotm-2016-10-27-18-27_patched/arch/x86/mm/gup.c > @@ -222,9 +222,9 @@ static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end, > pmd_t pmd = *pmdp; > > next = pmd_addr_end(addr, end); > - if (pmd_none(pmd)) > + if (!pmd_present(pmd)) > return 0; > - if (unlikely(pmd_large(pmd) || !pmd_present(pmd))) { > + if (unlikely(pmd_large(pmd))) { > /* > * NUMA hinting faults need to be handled in the GUP > * slowpath for accounting purposes and so that they > diff --git v4.9-rc2-mmotm-2016-10-27-18-27/fs/proc/task_mmu.c v4.9-rc2-mmotm-2016-10-27-18-27_patched/fs/proc/task_mmu.c > index 35b92d8..c1f9cf4 100644 > --- v4.9-rc2-mmotm-2016-10-27-18-27/fs/proc/task_mmu.c > +++ v4.9-rc2-mmotm-2016-10-27-18-27_patched/fs/proc/task_mmu.c > @@ -596,7 +596,8 @@ static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, > > ptl = pmd_trans_huge_lock(pmd, vma); > if (ptl) { > - smaps_pmd_entry(pmd, addr, walk); > + if (pmd_present(*pmd)) > + smaps_pmd_entry(pmd, addr, walk); > spin_unlock(ptl); > return 0; > } > @@ -929,6 +930,9 @@ static int clear_refs_pte_range(pmd_t *pmd, unsigned long addr, > goto out; > } > > + if (!pmd_present(*pmd)) > + goto out; > + Hm. Looks like clear_soft_dirty_pmd() should handle !present. It doesn't. Ah.. Found it in 08/12. > page = pmd_page(*pmd); > > /* Clear accessed and referenced bits. */ > @@ -1208,19 +1212,18 @@ static int pagemap_pmd_range(pmd_t *pmdp, unsigned long addr, unsigned long end, > if (ptl) { > u64 flags = 0, frame = 0; > pmd_t pmd = *pmdp; > + struct page *page; > > if ((vma->vm_flags & VM_SOFTDIRTY) || pmd_soft_dirty(pmd)) > flags |= PM_SOFT_DIRTY; > > - /* > - * Currently pmd for thp is always present because thp > - * can not be swapped-out, migrated, or HWPOISONed > - * (split in such cases instead.) > - * This if-check is just to prepare for future implementation. > - */ > - if (pmd_present(pmd)) { > - struct page *page = pmd_page(pmd); > - > + if (is_pmd_migration_entry(pmd)) { > + swp_entry_t entry = pmd_to_swp_entry(pmd); > + frame = swp_type(entry) | > + (swp_offset(entry) << MAX_SWAPFILES_SHIFT); > + page = migration_entry_to_page(entry); > + } else if (pmd_present(pmd)) { > + page = pmd_page(pmd); > if (page_mapcount(page) == 1) > flags |= PM_MMAP_EXCLUSIVE; > > diff --git v4.9-rc2-mmotm-2016-10-27-18-27/include/linux/huge_mm.h v4.9-rc2-mmotm-2016-10-27-18-27_patched/include/linux/huge_mm.h > index fcbca51..3c252cd 100644 > --- v4.9-rc2-mmotm-2016-10-27-18-27/include/linux/huge_mm.h > +++ v4.9-rc2-mmotm-2016-10-27-18-27_patched/include/linux/huge_mm.h > @@ -125,12 +125,19 @@ extern void vma_adjust_trans_huge(struct vm_area_struct *vma, > long adjust_next); > extern spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, > struct vm_area_struct *vma); > + > +static inline int pmd_related(pmd_t pmd) > +{ > + return !pmd_none(pmd) && > + (!pmd_present(pmd) || pmd_trans_huge(pmd) || pmd_devmap(pmd)); > +} > + I would rather create is_swap_pmd() -- (!none && !present) and leave the reset open-codded. > /* mmap_sem must be held on entry */ > static inline spinlock_t *pmd_trans_huge_lock(pmd_t *pmd, > struct vm_area_struct *vma) > { > VM_BUG_ON_VMA(!rwsem_is_locked(&vma->vm_mm->mmap_sem), vma); > - if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd)) > + if (pmd_related(*pmd)) > return __pmd_trans_huge_lock(pmd, vma); > else > return NULL; > diff --git v4.9-rc2-mmotm-2016-10-27-18-27/mm/gup.c v4.9-rc2-mmotm-2016-10-27-18-27_patched/mm/gup.c > index e50178c..2dc4978 100644 > --- v4.9-rc2-mmotm-2016-10-27-18-27/mm/gup.c > +++ v4.9-rc2-mmotm-2016-10-27-18-27_patched/mm/gup.c > @@ -267,6 +267,8 @@ struct page *follow_page_mask(struct vm_area_struct *vma, > } > if ((flags & FOLL_NUMA) && pmd_protnone(*pmd)) > return no_page_table(vma, flags); > + if (!pmd_present(*pmd)) > + return no_page_table(vma, flags); Don't we need FOLL_MIGRATION, like on pte side? > if (pmd_devmap(*pmd)) { > ptl = pmd_lock(mm, pmd); > page = follow_devmap_pmd(vma, address, pmd, flags); > @@ -278,6 +280,10 @@ struct page *follow_page_mask(struct vm_area_struct *vma, > return follow_page_pte(vma, address, pmd, flags); > > ptl = pmd_lock(mm, pmd); > + if (unlikely(!pmd_present(*pmd))) { > + spin_unlock(ptl); > + return no_page_table(vma, flags); > + } Ditto. > if (unlikely(!pmd_trans_huge(*pmd))) { > spin_unlock(ptl); > return follow_page_pte(vma, address, pmd, flags); > @@ -333,7 +339,7 @@ static int get_gate_page(struct mm_struct *mm, unsigned long address, > pud = pud_offset(pgd, address); > BUG_ON(pud_none(*pud)); > pmd = pmd_offset(pud, address); > - if (pmd_none(*pmd)) > + if (!pmd_present(*pmd)) > return -EFAULT; > VM_BUG_ON(pmd_trans_huge(*pmd)); > pte = pte_offset_map(pmd, address); > @@ -1357,7 +1363,7 @@ static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end, > pmd_t pmd = READ_ONCE(*pmdp); > > next = pmd_addr_end(addr, end); > - if (pmd_none(pmd)) > + if (!pmd_present(pmd)) > return 0; > > if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd))) { > diff --git v4.9-rc2-mmotm-2016-10-27-18-27/mm/huge_memory.c v4.9-rc2-mmotm-2016-10-27-18-27_patched/mm/huge_memory.c > index b3022b3..4e9090c 100644 > --- v4.9-rc2-mmotm-2016-10-27-18-27/mm/huge_memory.c > +++ v4.9-rc2-mmotm-2016-10-27-18-27_patched/mm/huge_memory.c > @@ -825,6 +825,20 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, > > ret = -EAGAIN; > pmd = *src_pmd; > + > + if (unlikely(is_pmd_migration_entry(pmd))) { > + swp_entry_t entry = pmd_to_swp_entry(pmd); > + > + if (is_write_migration_entry(entry)) { > + make_migration_entry_read(&entry); > + pmd = swp_entry_to_pmd(entry); > + set_pmd_at(src_mm, addr, src_pmd, pmd); > + } I think we should put at least WARN_ONCE() in 'else' here. We don't want to miss such places when swap will be supported (or other swap entry type). > + set_pmd_at(dst_mm, addr, dst_pmd, pmd); > + ret = 0; > + goto out_unlock; > + } > + > if (unlikely(!pmd_trans_huge(pmd))) { > pte_free(dst_mm, pgtable); > goto out_unlock; > @@ -1013,6 +1027,9 @@ int do_huge_pmd_wp_page(struct fault_env *fe, pmd_t orig_pmd) > if (unlikely(!pmd_same(*fe->pmd, orig_pmd))) > goto out_unlock; > > + if (unlikely(!pmd_present(orig_pmd))) > + goto out_unlock; > + > page = pmd_page(orig_pmd); > VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page); > /* > @@ -1137,7 +1154,14 @@ struct page *follow_trans_huge_pmd(struct vm_area_struct *vma, > if ((flags & FOLL_NUMA) && pmd_protnone(*pmd)) > goto out; > > - page = pmd_page(*pmd); > + if (is_pmd_migration_entry(*pmd)) { > + swp_entry_t entry; > + entry = pmd_to_swp_entry(*pmd); > + page = pfn_to_page(swp_offset(entry)); > + if (!is_migration_entry(entry)) > + goto out; follow_page_pte() does different thing: wait for page to be migrated and retry. Any reason you don't do the same? > + } else > + page = pmd_page(*pmd); > VM_BUG_ON_PAGE(!PageHead(page) && !is_zone_device_page(page), page); > if (flags & FOLL_TOUCH) > touch_pmd(vma, addr, pmd); > @@ -1332,6 +1356,9 @@ bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, > if (is_huge_zero_pmd(orig_pmd)) > goto out; > > + if (unlikely(!pmd_present(orig_pmd))) > + goto out; > + > page = pmd_page(orig_pmd); > /* > * If other processes are mapping this page, we couldn't discard > @@ -1410,20 +1437,35 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, > tlb_remove_page_size(tlb, pmd_page(orig_pmd), HPAGE_PMD_SIZE); > } else { > struct page *page = pmd_page(orig_pmd); > - page_remove_rmap(page, true); > - VM_BUG_ON_PAGE(page_mapcount(page) < 0, page); > - VM_BUG_ON_PAGE(!PageHead(page), page); > - if (PageAnon(page)) { > - pgtable_t pgtable; > - pgtable = pgtable_trans_huge_withdraw(tlb->mm, pmd); > - pte_free(tlb->mm, pgtable); > - atomic_long_dec(&tlb->mm->nr_ptes); > - add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR); > + int migration = 0; > + > + if (!is_pmd_migration_entry(orig_pmd)) { > + page_remove_rmap(page, true); > + VM_BUG_ON_PAGE(page_mapcount(page) < 0, page); > + VM_BUG_ON_PAGE(!PageHead(page), page); > + if (PageAnon(page)) { > + pgtable_t pgtable; > + pgtable = pgtable_trans_huge_withdraw(tlb->mm, > + pmd); > + pte_free(tlb->mm, pgtable); > + atomic_long_dec(&tlb->mm->nr_ptes); > + add_mm_counter(tlb->mm, MM_ANONPAGES, > + -HPAGE_PMD_NR); > + } else { > + add_mm_counter(tlb->mm, MM_FILEPAGES, > + -HPAGE_PMD_NR); > + } > } else { > - add_mm_counter(tlb->mm, MM_FILEPAGES, -HPAGE_PMD_NR); > + swp_entry_t entry; > + > + entry = pmd_to_swp_entry(orig_pmd); > + free_swap_and_cache(entry); /* waring in failure? */ > + add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR); > + migration = 1; > } > spin_unlock(ptl); > - tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE); > + if (!migration) > + tlb_remove_page_size(tlb, page, HPAGE_PMD_SIZE); > } > return 1; > } > @@ -1496,14 +1538,27 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, > bool preserve_write = prot_numa && pmd_write(*pmd); > ret = 1; > > + if (!pmd_present(*pmd)) > + goto unlock; > /* > * Avoid trapping faults against the zero page. The read-only > * data is likely to be read-cached on the local CPU and > * local/remote hits to the zero page are not interesting. > */ > - if (prot_numa && is_huge_zero_pmd(*pmd)) { > - spin_unlock(ptl); > - return ret; > + if (prot_numa && is_huge_zero_pmd(*pmd)) > + goto unlock; > + > + if (is_pmd_migration_entry(*pmd)) { Hm? But we filtered out !present above? > + swp_entry_t entry = pmd_to_swp_entry(*pmd); > + > + if (is_write_migration_entry(entry)) { > + pmd_t newpmd; > + > + make_migration_entry_read(&entry); > + newpmd = swp_entry_to_pmd(entry); > + set_pmd_at(mm, addr, pmd, newpmd); > + } > + goto unlock; > } > > if (!prot_numa || !pmd_protnone(*pmd)) { > @@ -1516,6 +1571,7 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, > BUG_ON(vma_is_anonymous(vma) && !preserve_write && > pmd_write(entry)); > } > +unlock: > spin_unlock(ptl); > } > > @@ -1532,7 +1588,7 @@ spinlock_t *__pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma) > { > spinlock_t *ptl; > ptl = pmd_lock(vma->vm_mm, pmd); > - if (likely(pmd_trans_huge(*pmd) || pmd_devmap(*pmd))) > + if (likely(pmd_related(*pmd))) > return ptl; > spin_unlock(ptl); > return NULL; > diff --git v4.9-rc2-mmotm-2016-10-27-18-27/mm/madvise.c v4.9-rc2-mmotm-2016-10-27-18-27_patched/mm/madvise.c > index 0e3828e..eaa2b02 100644 > --- v4.9-rc2-mmotm-2016-10-27-18-27/mm/madvise.c > +++ v4.9-rc2-mmotm-2016-10-27-18-27_patched/mm/madvise.c > @@ -274,7 +274,7 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr, > unsigned long next; > > next = pmd_addr_end(addr, end); > - if (pmd_trans_huge(*pmd)) > + if (pmd_related(*pmd)) I don't see a point going for madvise_free_huge_pmd(), just to fall off on !present inside. And is it safe for devmap? > if (madvise_free_huge_pmd(tlb, vma, pmd, addr, next)) > goto next; > > diff --git v4.9-rc2-mmotm-2016-10-27-18-27/mm/memcontrol.c v4.9-rc2-mmotm-2016-10-27-18-27_patched/mm/memcontrol.c > index 91dfc7c..ebc2c42 100644 > --- v4.9-rc2-mmotm-2016-10-27-18-27/mm/memcontrol.c > +++ v4.9-rc2-mmotm-2016-10-27-18-27_patched/mm/memcontrol.c > @@ -4635,6 +4635,8 @@ static enum mc_target_type get_mctgt_type_thp(struct vm_area_struct *vma, > struct page *page = NULL; > enum mc_target_type ret = MC_TARGET_NONE; > > + if (unlikely(!pmd_present(pmd))) > + return ret; > page = pmd_page(pmd); > VM_BUG_ON_PAGE(!page || !PageHead(page), page); > if (!(mc.flags & MOVE_ANON)) > diff --git v4.9-rc2-mmotm-2016-10-27-18-27/mm/memory.c v4.9-rc2-mmotm-2016-10-27-18-27_patched/mm/memory.c > index 94b5e2c..33fa439 100644 > --- v4.9-rc2-mmotm-2016-10-27-18-27/mm/memory.c > +++ v4.9-rc2-mmotm-2016-10-27-18-27_patched/mm/memory.c > @@ -999,7 +999,7 @@ static inline int copy_pmd_range(struct mm_struct *dst_mm, struct mm_struct *src > src_pmd = pmd_offset(src_pud, addr); > do { > next = pmd_addr_end(addr, end); > - if (pmd_trans_huge(*src_pmd) || pmd_devmap(*src_pmd)) { > + if (pmd_related(*src_pmd)) { > int err; > VM_BUG_ON(next-addr != HPAGE_PMD_SIZE); > err = copy_huge_pmd(dst_mm, src_mm, > @@ -3591,6 +3591,10 @@ static int __handle_mm_fault(struct vm_area_struct *vma, unsigned long address, > int ret; > > barrier(); > + if (unlikely(is_pmd_migration_entry(orig_pmd))) { > + pmd_migration_entry_wait(mm, fe.pmd); > + return 0; > + } > if (pmd_trans_huge(orig_pmd) || pmd_devmap(orig_pmd)) { > if (pmd_protnone(orig_pmd) && vma_is_accessible(vma)) > return do_huge_pmd_numa_page(&fe, orig_pmd); > diff --git v4.9-rc2-mmotm-2016-10-27-18-27/mm/mprotect.c v4.9-rc2-mmotm-2016-10-27-18-27_patched/mm/mprotect.c > index c5ba2aa..81186e3 100644 > --- v4.9-rc2-mmotm-2016-10-27-18-27/mm/mprotect.c > +++ v4.9-rc2-mmotm-2016-10-27-18-27_patched/mm/mprotect.c > @@ -164,6 +164,8 @@ static inline unsigned long change_pmd_range(struct vm_area_struct *vma, > unsigned long this_pages; > > next = pmd_addr_end(addr, end); > + if (!pmd_present(*pmd)) > + continue; > if (!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd) > && pmd_none_or_clear_bad(pmd)) > continue; > diff --git v4.9-rc2-mmotm-2016-10-27-18-27/mm/mremap.c v4.9-rc2-mmotm-2016-10-27-18-27_patched/mm/mremap.c > index da22ad2..a94a698 100644 > --- v4.9-rc2-mmotm-2016-10-27-18-27/mm/mremap.c > +++ v4.9-rc2-mmotm-2016-10-27-18-27_patched/mm/mremap.c > @@ -194,7 +194,7 @@ unsigned long move_page_tables(struct vm_area_struct *vma, > new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr); > if (!new_pmd) > break; > - if (pmd_trans_huge(*old_pmd)) { > + if (pmd_related(*old_pmd)) { > if (extent == HPAGE_PMD_SIZE) { > bool moved; > /* See comment in move_ptes() */ > -- > 2.7.0 > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@kvack.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: email@kvack.org -- Kirill A. Shutemov