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 <luto@xxxxxxxxxxxxxx> > >Signed-off-by: Cyrill Gorcunov <gorcunov@xxxxxxxxxx> > >Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx> > >Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > >Cc: Matt Mackall <mpm@xxxxxxxxxxx> > >Cc: Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxxxxxx> > >Cc: Marcelo Tosatti <mtosatti@xxxxxxxxxx> > >Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxx> > >Cc: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx> > >Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > >Cc: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx> > >--- > > 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. > > > 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@xxxxxxxxx. For more info on Linux MM, > >see: http://www.linux-mm.org/ . > >Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a> > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@xxxxxxxxx. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a> -- Kind regards, Minchan Kim -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>