From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx168.postini.com [74.125.245.168]) by kanga.kvack.org (Postfix) with SMTP id 4C5EA6B0031 for ; Sun, 4 Aug 2013 22:39:11 -0400 (EDT) Received: from /spool/local by e23smtp03.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 5 Aug 2013 12:28:34 +1000 Received: from d23relay04.au.ibm.com (d23relay04.au.ibm.com [9.190.234.120]) by d23dlp02.au.ibm.com (Postfix) with ESMTP id 743B22BB0055 for ; Mon, 5 Aug 2013 12:39:02 +1000 (EST) Received: from d23av01.au.ibm.com (d23av01.au.ibm.com [9.190.234.96]) by d23relay04.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r752NOSF54722630 for ; Mon, 5 Aug 2013 12:23:24 +1000 Received: from d23av01.au.ibm.com (localhost [127.0.0.1]) by d23av01.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id r752d0n2018203 for ; Mon, 5 Aug 2013 12:39:01 +1000 Date: Mon, 5 Aug 2013 10:38:58 +0800 From: Wanpeng Li Subject: Re: [patch 1/2] [PATCH] mm: Save soft-dirty bits on swapped pages Message-ID: <20130805023858.GA1039@hacker.(null)> Reply-To: Wanpeng Li References: <20130730204154.407090410@gmail.com> <20130730204654.844299768@gmail.com> <51ff047d.2768310a.2fc4.340fSMTPIN_ADDED_BROKEN@mx.google.com> <20130805021715.GJ32486@bbox> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130805021715.GJ32486@bbox> Sender: owner-linux-mm@kvack.org List-ID: To: Minchan Kim Cc: Cyrill Gorcunov , linux-mm@kvack.org, linux-kernel@vger.kernel.org, luto@amacapital.net, gorcunov@openvz.org, xemul@parallels.com, akpm@linux-foundation.org, mpm@selenic.com, xiaoguangrong@linux.vnet.ibm.com, mtosatti@redhat.com, kosaki.motohiro@gmail.com, sfr@canb.auug.org.au, peterz@infradead.org, aneesh.kumar@linux.vnet.ibm.com Hi Minchan, On Mon, Aug 05, 2013 at 11:17:15AM +0900, Minchan Kim wrote: >Hello Wanpeng, > >On Mon, Aug 05, 2013 at 09:48:29AM +0800, Wanpeng Li wrote: >> On Wed, Jul 31, 2013 at 12:41:55AM +0400, Cyrill Gorcunov wrote: >> >Andy Lutomirski reported that in case if a page with _PAGE_SOFT_DIRTY >> >bit set get swapped out, the bit is getting lost and no longer >> >available when pte read back. >> > >> >To resolve this we introduce _PTE_SWP_SOFT_DIRTY bit which is >> >saved in pte entry for the page being swapped out. When such page >> >is to be read back from a swap cache we check for bit presence >> >and if it's there we clear it and restore the former _PAGE_SOFT_DIRTY >> >bit back. >> > >> >One of the problem was to find a place in pte entry where we can >> >save the _PTE_SWP_SOFT_DIRTY bit while page is in swap. The >> >_PAGE_PSE was chosen for that, it doesn't intersect with swap >> >entry format stored in pte. >> > >> >Reported-by: Andy Lutomirski >> >Signed-off-by: Cyrill Gorcunov >> >Cc: Pavel Emelyanov >> >Cc: Andrew Morton >> >Cc: Matt Mackall >> >Cc: Xiao Guangrong >> >Cc: Marcelo Tosatti >> >Cc: KOSAKI Motohiro >> >Cc: Stephen Rothwell >> >Cc: Peter Zijlstra >> >Cc: "Aneesh Kumar K.V" >> >--- >> > arch/x86/include/asm/pgtable.h | 15 +++++++++++++++ >> > arch/x86/include/asm/pgtable_types.h | 13 +++++++++++++ >> > fs/proc/task_mmu.c | 21 +++++++++++++++------ >> > include/asm-generic/pgtable.h | 15 +++++++++++++++ >> > include/linux/swapops.h | 2 ++ >> > mm/memory.c | 2 ++ >> > mm/rmap.c | 6 +++++- >> > mm/swapfile.c | 19 +++++++++++++++++-- >> > 8 files changed, 84 insertions(+), 9 deletions(-) >> > >> >Index: linux-2.6.git/arch/x86/include/asm/pgtable.h >> >=================================================================== >> >--- linux-2.6.git.orig/arch/x86/include/asm/pgtable.h >> >+++ linux-2.6.git/arch/x86/include/asm/pgtable.h >> >@@ -314,6 +314,21 @@ static inline pmd_t pmd_mksoft_dirty(pmd >> > return pmd_set_flags(pmd, _PAGE_SOFT_DIRTY); >> > } >> > >> >+static inline pte_t pte_swp_mksoft_dirty(pte_t pte) >> >+{ >> >+ return pte_set_flags(pte, _PAGE_SWP_SOFT_DIRTY); >> >+} >> >+ >> >+static inline int pte_swp_soft_dirty(pte_t pte) >> >+{ >> >+ return pte_flags(pte) & _PAGE_SWP_SOFT_DIRTY; >> >+} >> >+ >> >+static inline pte_t pte_swp_clear_soft_dirty(pte_t pte) >> >+{ >> >+ return pte_clear_flags(pte, _PAGE_SWP_SOFT_DIRTY); >> >+} >> >+ >> > /* >> > * Mask out unsupported bits in a present pgprot. Non-present pgprots >> > * can use those bits for other purposes, so leave them be. >> >Index: linux-2.6.git/arch/x86/include/asm/pgtable_types.h >> >=================================================================== >> >--- linux-2.6.git.orig/arch/x86/include/asm/pgtable_types.h >> >+++ linux-2.6.git/arch/x86/include/asm/pgtable_types.h >> >@@ -67,6 +67,19 @@ >> > #define _PAGE_SOFT_DIRTY (_AT(pteval_t, 0)) >> > #endif >> > >> >+/* >> >+ * Tracking soft dirty bit when a page goes to a swap is tricky. >> >+ * We need a bit which can be stored in pte _and_ not conflict >> >+ * with swap entry format. On x86 bits 6 and 7 are *not* involved >> >+ * into swap entry computation, but bit 6 is used for nonlinear >> >+ * file mapping, so we borrow bit 7 for soft dirty tracking. >> >+ */ >> >+#ifdef CONFIG_MEM_SOFT_DIRTY >> >+#define _PAGE_SWP_SOFT_DIRTY _PAGE_PSE >> >+#else >> >+#define _PAGE_SWP_SOFT_DIRTY (_AT(pteval_t, 0)) >> >+#endif >> >+ >> > #if defined(CONFIG_X86_64) || defined(CONFIG_X86_PAE) >> > #define _PAGE_NX (_AT(pteval_t, 1) << _PAGE_BIT_NX) >> > #else >> >Index: linux-2.6.git/fs/proc/task_mmu.c >> >=================================================================== >> >--- linux-2.6.git.orig/fs/proc/task_mmu.c >> >+++ linux-2.6.git/fs/proc/task_mmu.c >> >@@ -730,8 +730,14 @@ static inline void clear_soft_dirty(stru >> > * of how soft-dirty works. >> > */ >> > pte_t ptent = *pte; >> >- ptent = pte_wrprotect(ptent); >> >- ptent = pte_clear_flags(ptent, _PAGE_SOFT_DIRTY); >> >+ >> >+ if (pte_present(ptent)) { >> >+ ptent = pte_wrprotect(ptent); >> >+ ptent = pte_clear_flags(ptent, _PAGE_SOFT_DIRTY); >> >+ } else if (is_swap_pte(ptent)) { >> >+ ptent = pte_swp_clear_soft_dirty(ptent); >> >+ } >> >+ >> > set_pte_at(vma->vm_mm, addr, pte, ptent); >> > #endif >> > } >> >@@ -752,14 +758,15 @@ static int clear_refs_pte_range(pmd_t *p >> > pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); >> > for (; addr != end; pte++, addr += PAGE_SIZE) { >> > ptent = *pte; >> >- if (!pte_present(ptent)) >> >- continue; >> > >> > if (cp->type == CLEAR_REFS_SOFT_DIRTY) { >> > clear_soft_dirty(vma, addr, pte); >> > continue; >> > } >> > >> >+ if (!pte_present(ptent)) >> >+ continue; >> >+ >> > page = vm_normal_page(vma, addr, ptent); >> > if (!page) >> > continue; >> >@@ -930,8 +937,10 @@ static void pte_to_pagemap_entry(pagemap >> > flags = PM_PRESENT; >> > page = vm_normal_page(vma, addr, pte); >> > } else if (is_swap_pte(pte)) { >> >- swp_entry_t entry = pte_to_swp_entry(pte); >> >- >> >+ swp_entry_t entry; >> >+ if (pte_swp_soft_dirty(pte)) >> >+ flags2 |= __PM_SOFT_DIRTY; >> >+ entry = pte_to_swp_entry(pte); >> > frame = swp_type(entry) | >> > (swp_offset(entry) << MAX_SWAPFILES_SHIFT); >> > flags = PM_SWAP; >> >Index: linux-2.6.git/include/asm-generic/pgtable.h >> >=================================================================== >> >--- linux-2.6.git.orig/include/asm-generic/pgtable.h >> >+++ linux-2.6.git/include/asm-generic/pgtable.h >> >@@ -417,6 +417,21 @@ static inline pmd_t pmd_mksoft_dirty(pmd >> > { >> > return pmd; >> > } >> >+ >> >+static inline pte_t pte_swp_mksoft_dirty(pte_t pte) >> >+{ >> >+ return pte; >> >+} >> >+ >> >+static inline int pte_swp_soft_dirty(pte_t pte) >> >+{ >> >+ return 0; >> >+} >> >+ >> >+static inline pte_t pte_swp_clear_soft_dirty(pte_t pte) >> >+{ >> >+ return pte; >> >+} >> > #endif >> > >> > #ifndef __HAVE_PFNMAP_TRACKING >> >Index: linux-2.6.git/include/linux/swapops.h >> >=================================================================== >> >--- linux-2.6.git.orig/include/linux/swapops.h >> >+++ linux-2.6.git/include/linux/swapops.h >> >@@ -67,6 +67,8 @@ static inline swp_entry_t pte_to_swp_ent >> > swp_entry_t arch_entry; >> > >> > BUG_ON(pte_file(pte)); >> >+ if (pte_swp_soft_dirty(pte)) >> >+ pte = pte_swp_clear_soft_dirty(pte); >> > arch_entry = __pte_to_swp_entry(pte); >> > return swp_entry(__swp_type(arch_entry), __swp_offset(arch_entry)); >> > } >> >Index: linux-2.6.git/mm/memory.c >> >=================================================================== >> >--- linux-2.6.git.orig/mm/memory.c >> >+++ linux-2.6.git/mm/memory.c >> >@@ -3115,6 +3115,8 @@ static int do_swap_page(struct mm_struct >> > exclusive = 1; >> > } >> > flush_icache_page(vma, page); >> >+ if (pte_swp_soft_dirty(orig_pte)) >> >+ pte = pte_mksoft_dirty(pte); >> >> entry = pte_to_swp_entry(orig_pte); >> orig_pte's _PTE_SWP_SOFT_DIRTY bit has already been cleared. > >You seem to walk same way with me. >Please look at my stupid questions in this thread. > I see your discussion with Cyrill, however, pte_to_swp_entry and pte_swp_soft_dirty both against orig_pte, where I miss? ;-) >> >> > set_pte_at(mm, address, page_table, pte); >> > if (page == swapcache) >> > do_page_add_anon_rmap(page, vma, address, exclusive); >> >Index: linux-2.6.git/mm/rmap.c >> >=================================================================== >> >--- linux-2.6.git.orig/mm/rmap.c >> >+++ linux-2.6.git/mm/rmap.c >> >@@ -1236,6 +1236,7 @@ int try_to_unmap_one(struct page *page, >> > swp_entry_to_pte(make_hwpoison_entry(page))); >> > } else if (PageAnon(page)) { >> > swp_entry_t entry = { .val = page_private(page) }; >> >+ pte_t swp_pte; >> > >> > if (PageSwapCache(page)) { >> > /* >> >@@ -1264,7 +1265,10 @@ int try_to_unmap_one(struct page *page, >> > BUG_ON(TTU_ACTION(flags) != TTU_MIGRATION); >> > entry = make_migration_entry(page, pte_write(pteval)); >> > } >> >- set_pte_at(mm, address, pte, swp_entry_to_pte(entry)); >> >+ swp_pte = swp_entry_to_pte(entry); >> >+ if (pte_soft_dirty(pteval)) >> >+ swp_pte = pte_swp_mksoft_dirty(swp_pte); >> >+ set_pte_at(mm, address, pte, swp_pte); >> > BUG_ON(pte_file(*pte)); >> > } else if (IS_ENABLED(CONFIG_MIGRATION) && >> > (TTU_ACTION(flags) == TTU_MIGRATION)) { >> >Index: linux-2.6.git/mm/swapfile.c >> >=================================================================== >> >--- linux-2.6.git.orig/mm/swapfile.c >> >+++ linux-2.6.git/mm/swapfile.c >> >@@ -866,6 +866,21 @@ unsigned int count_swap_pages(int type, >> > } >> > #endif /* CONFIG_HIBERNATION */ >> > >> >+static inline int maybe_same_pte(pte_t pte, pte_t swp_pte) >> >+{ >> >+#ifdef CONFIG_MEM_SOFT_DIRTY >> >+ /* >> >+ * When pte keeps soft dirty bit the pte generated >> >+ * from swap entry does not has it, still it's same >> >+ * pte from logical point of view. >> >+ */ >> >+ pte_t swp_pte_dirty = pte_swp_mksoft_dirty(swp_pte); >> >+ return pte_same(pte, swp_pte) || pte_same(pte, swp_pte_dirty); >> >+#else >> >+ return pte_same(pte, swp_pte); >> >+#endif >> >+} >> >+ >> > /* >> > * No need to decide whether this PTE shares the swap entry with others, >> > * just let do_wp_page work it out if a write is requested later - to >> >@@ -892,7 +907,7 @@ static int unuse_pte(struct vm_area_stru >> > } >> > >> > pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); >> >- if (unlikely(!pte_same(*pte, swp_entry_to_pte(entry)))) { >> >+ if (unlikely(!maybe_same_pte(*pte, swp_entry_to_pte(entry)))) { >> > mem_cgroup_cancel_charge_swapin(memcg); >> > ret = 0; >> > goto out; >> >@@ -947,7 +962,7 @@ static int unuse_pte_range(struct vm_are >> > * swapoff spends a _lot_ of time in this loop! >> > * Test inline before going to call unuse_pte. >> > */ >> >- if (unlikely(pte_same(*pte, swp_pte))) { >> >+ if (unlikely(maybe_same_pte(*pte, swp_pte))) { >> > pte_unmap(pte); >> > ret = unuse_pte(vma, pmd, addr, entry, page); >> > if (ret) >> > >> >-- >> >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 >> >> -- >> 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 > >-- >Kind regards, >Minchan Kim -- 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