Subject: [to-be-updated] mm-save-soft-dirty-bits-on-swapped-pages.patch removed from -mm tree
To: gorcunov@xxxxxxxxx,James.Bottomley@xxxxxxxxxxxxxxxxxxxxx,gorcunov@xxxxxxxxxx,hush.bensen@xxxxxxxxx,kosaki.motohiro@xxxxxxxxx,luto@xxxxxxxxxxxxxx,mpm@xxxxxxxxxxx,mtosatti@xxxxxxxxxx,sfr@xxxxxxxxxxxxxxxx,xemul@xxxxxxxxxxxxx,xiaoguangrong@xxxxxxxxxxxxxxxxxx,mm-commits@xxxxxxxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Tue, 30 Jul 2013 13:33:12 -0700
The patch titled
Subject: mm: save soft-dirty bits on swapped pages
has been removed from the -mm tree. Its filename was
mm-save-soft-dirty-bits-on-swapped-pages.patch
This patch was dropped because an updated version will be merged
------------------------------------------------------
From: Cyrill Gorcunov <gorcunov@xxxxxxxxx>
Subject: mm: save soft-dirty bits on swapped pages
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: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
Signed-off-by: Cyrill Gorcunov <gorcunov@xxxxxxxxxx>
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: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
Cc: Hush Bensen <hush.bensen@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/x86/include/asm/pgtable.h | 15 +++++++++++++++
arch/x86/include/asm/pgtable_types.h | 13 +++++++++++++
fs/proc/task_mmu.c | 23 +++++++++++++++++------
include/linux/swapops.h | 4 ++++
mm/memory.c | 4 ++++
mm/rmap.c | 6 +++++-
6 files changed, 58 insertions(+), 7 deletions(-)
diff -puN arch/x86/include/asm/pgtable.h~mm-save-soft-dirty-bits-on-swapped-pages arch/x86/include/asm/pgtable.h
--- a/arch/x86/include/asm/pgtable.h~mm-save-soft-dirty-bits-on-swapped-pages
+++ a/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.
diff -puN arch/x86/include/asm/pgtable_types.h~mm-save-soft-dirty-bits-on-swapped-pages arch/x86/include/asm/pgtable_types.h
--- a/arch/x86/include/asm/pgtable_types.h~mm-save-soft-dirty-bits-on-swapped-pages
+++ a/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
diff -puN fs/proc/task_mmu.c~mm-save-soft-dirty-bits-on-swapped-pages fs/proc/task_mmu.c
--- a/fs/proc/task_mmu.c~mm-save-soft-dirty-bits-on-swapped-pages
+++ a/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 (pte_swp_soft_dirty(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 +937,12 @@ 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;
+#ifdef CONFIG_MEM_SOFT_DIRTY
+ if (pte_swp_soft_dirty(pte))
+ flags2 |= __PM_SOFT_DIRTY;
+#endif
+ entry = pte_to_swp_entry(pte);
frame = swp_type(entry) |
(swp_offset(entry) << MAX_SWAPFILES_SHIFT);
flags = PM_SWAP;
diff -puN include/linux/swapops.h~mm-save-soft-dirty-bits-on-swapped-pages include/linux/swapops.h
--- a/include/linux/swapops.h~mm-save-soft-dirty-bits-on-swapped-pages
+++ a/include/linux/swapops.h
@@ -67,6 +67,10 @@ static inline swp_entry_t pte_to_swp_ent
swp_entry_t arch_entry;
BUG_ON(pte_file(pte));
+#ifdef CONFIG_MEM_SOFT_DIRTY
+ if (pte_swp_soft_dirty(pte))
+ pte = pte_swp_clear_soft_dirty(pte);
+#endif
arch_entry = __pte_to_swp_entry(pte);
return swp_entry(__swp_type(arch_entry), __swp_offset(arch_entry));
}
diff -puN mm/memory.c~mm-save-soft-dirty-bits-on-swapped-pages mm/memory.c
--- a/mm/memory.c~mm-save-soft-dirty-bits-on-swapped-pages
+++ a/mm/memory.c
@@ -3115,6 +3115,10 @@ static int do_swap_page(struct mm_struct
exclusive = 1;
}
flush_icache_page(vma, page);
+#ifdef CONFIG_MEM_SOFT_DIRTY
+ if (pte_swp_soft_dirty(orig_pte))
+ pte = pte_mksoft_dirty(pte);
+#endif
set_pte_at(mm, address, page_table, pte);
if (page == swapcache)
do_page_add_anon_rmap(page, vma, address, exclusive);
diff -puN mm/rmap.c~mm-save-soft-dirty-bits-on-swapped-pages mm/rmap.c
--- a/mm/rmap.c~mm-save-soft-dirty-bits-on-swapped-pages
+++ a/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)) {
_
Patches currently in -mm which might be from gorcunov@xxxxxxxxx are
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