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SubjectRe: [patch 2/2] [PATCH] mm: Save soft-dirty bits on file pages
On Thu, 8 Aug 2013 18:51:20 +0400 Cyrill Gorcunov <gorcunov@gmail.com> wrote:

> On Wed, Aug 07, 2013 at 01:28:12PM -0700, Andrew Morton wrote:
> >
> > Good god.
> >
> > I wonder if these can be turned into out-of-line functions in some form
> > which humans can understand.
> >
> > or
> >
> > #define pte_to_pgoff(pte)
> > frob(pte, PTE_FILE_SHIFT1, PTE_FILE_BITS1) +
> > frob(PTE_FILE_SHIFT2, PTE_FILE_BITS2) +
> > frob(PTE_FILE_SHIFT3, PTE_FILE_BITS3) +
> > frob(PTE_FILE_SHIFT4, PTE_FILE_BITS1 + PTE_FILE_BITS2 + PTE_FILE_BITS3)
>
> Hi, here is what I ended up with. Please take a look (I decided to post
> patch in the thread since it's related to the context of the mails).

You could have #undefed _mfrob and __frob after using them, but whatever.

I saved this patch to wave at the x86 guys for 3.12. I plan to merge
mm-save-soft-dirty-bits-on-file-pages.patch for 3.11.

> Guys, is there a reason for "if _PAGE_BIT_FILE < _PAGE_BIT_PROTNONE"
> test present in this pgtable-2level.h file at all? I can't imagine
> where it can be false on x86.

I doubt if "Guys" read this. x86 maintainers cc'ed.





From: Cyrill Gorcunov <gorcunov@gmail.com>
Subject: arch/x86/include/asm/pgtable-2level.h: clean up pte_to_pgoff and pgoff_to_pte helpers

Andrew asked if there a way to make pte_to_pgoff and pgoff_to_pte macro
helpers somehow more readable.

With this patch it should be more understandable what is happening with
bits when they come to and from pte entry.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

arch/x86/include/asm/pgtable-2level.h | 82 ++++++++++++------------
1 file changed, 41 insertions(+), 41 deletions(-)

diff -puN arch/x86/include/asm/pgtable-2level.h~arch-x86-include-asm-pgtable-2levelh-clean-up-pte_to_pgoff-and-pgoff_to_pte-helpers arch/x86/include/asm/pgtable-2level.h
--- a/arch/x86/include/asm/pgtable-2level.h~arch-x86-include-asm-pgtable-2levelh-clean-up-pte_to_pgoff-and-pgoff_to_pte-helpers
+++ a/arch/x86/include/asm/pgtable-2level.h
@@ -55,6 +55,9 @@ static inline pmd_t native_pmdp_get_and_
#define native_pmdp_get_and_clear(xp) native_local_pmdp_get_and_clear(xp)
#endif

+#define _mfrob(v,r,m,l) ((((v) >> (r)) & (m)) << (l))
+#define __frob(v,r,l) (((v) >> (r)) << (l))
+
#ifdef CONFIG_MEM_SOFT_DIRTY

/*
@@ -71,31 +74,27 @@ static inline pmd_t native_pmdp_get_and_
#define PTE_FILE_BITS2 (PTE_FILE_SHIFT3 - PTE_FILE_SHIFT2 - 1)
#define PTE_FILE_BITS3 (PTE_FILE_SHIFT4 - PTE_FILE_SHIFT3 - 1)

-#define pte_to_pgoff(pte) \
- ((((pte).pte_low >> (PTE_FILE_SHIFT1)) \
- & ((1U << PTE_FILE_BITS1) - 1))) \
- + ((((pte).pte_low >> (PTE_FILE_SHIFT2)) \
- & ((1U << PTE_FILE_BITS2) - 1)) \
- << (PTE_FILE_BITS1)) \
- + ((((pte).pte_low >> (PTE_FILE_SHIFT3)) \
- & ((1U << PTE_FILE_BITS3) - 1)) \
- << (PTE_FILE_BITS1 + PTE_FILE_BITS2)) \
- + ((((pte).pte_low >> (PTE_FILE_SHIFT4))) \
- << (PTE_FILE_BITS1 + PTE_FILE_BITS2 + PTE_FILE_BITS3))
-
-#define pgoff_to_pte(off) \
- ((pte_t) { .pte_low = \
- ((((off)) & ((1U << PTE_FILE_BITS1) - 1)) << PTE_FILE_SHIFT1) \
- + ((((off) >> PTE_FILE_BITS1) \
- & ((1U << PTE_FILE_BITS2) - 1)) \
- << PTE_FILE_SHIFT2) \
- + ((((off) >> (PTE_FILE_BITS1 + PTE_FILE_BITS2)) \
- & ((1U << PTE_FILE_BITS3) - 1)) \
- << PTE_FILE_SHIFT3) \
- + ((((off) >> \
- (PTE_FILE_BITS1 + PTE_FILE_BITS2 + PTE_FILE_BITS3))) \
- << PTE_FILE_SHIFT4) \
- + _PAGE_FILE })
+#define PTE_FILE_MASK1 ((1U << PTE_FILE_BITS1) - 1)
+#define PTE_FILE_MASK2 ((1U << PTE_FILE_BITS2) - 1)
+#define PTE_FILE_MASK3 ((1U << PTE_FILE_BITS3) - 1)
+
+#define PTE_FILE_LSHIFT2 (PTE_FILE_BITS1)
+#define PTE_FILE_LSHIFT3 (PTE_FILE_BITS1 + PTE_FILE_BITS2)
+#define PTE_FILE_LSHIFT4 (PTE_FILE_BITS1 + PTE_FILE_BITS2 + PTE_FILE_BITS3)
+
+#define pte_to_pgoff(pte) \
+ (_mfrob((pte).pte_low, PTE_FILE_SHIFT1, PTE_FILE_MASK1, 0) + \
+ _mfrob((pte).pte_low, PTE_FILE_SHIFT2, PTE_FILE_MASK2, PTE_FILE_LSHIFT2) + \
+ _mfrob((pte).pte_low, PTE_FILE_SHIFT3, PTE_FILE_MASK3, PTE_FILE_LSHIFT3) + \
+ __frob((pte).pte_low, PTE_FILE_SHIFT4, PTE_FILE_LSHIFT4))
+
+#define pgoff_to_pte(off) \
+ ((pte_t) { .pte_low = \
+ _mfrob(off, 0, PTE_FILE_MASK1, PTE_FILE_SHIFT1) + \
+ _mfrob(off, PTE_FILE_LSHIFT2, PTE_FILE_MASK2, PTE_FILE_SHIFT2) + \
+ _mfrob(off, PTE_FILE_LSHIFT3, PTE_FILE_MASK3, PTE_FILE_SHIFT3) + \
+ __frob(off, PTE_FILE_LSHIFT4, PTE_FILE_SHIFT4) + \
+ _PAGE_FILE })

#else /* CONFIG_MEM_SOFT_DIRTY */

@@ -115,22 +114,23 @@ static inline pmd_t native_pmdp_get_and_
#define PTE_FILE_BITS1 (PTE_FILE_SHIFT2 - PTE_FILE_SHIFT1 - 1)
#define PTE_FILE_BITS2 (PTE_FILE_SHIFT3 - PTE_FILE_SHIFT2 - 1)

-#define pte_to_pgoff(pte) \
- ((((pte).pte_low >> PTE_FILE_SHIFT1) \
- & ((1U << PTE_FILE_BITS1) - 1)) \
- + ((((pte).pte_low >> PTE_FILE_SHIFT2) \
- & ((1U << PTE_FILE_BITS2) - 1)) << PTE_FILE_BITS1) \
- + (((pte).pte_low >> PTE_FILE_SHIFT3) \
- << (PTE_FILE_BITS1 + PTE_FILE_BITS2)))
-
-#define pgoff_to_pte(off) \
- ((pte_t) { .pte_low = \
- (((off) & ((1U << PTE_FILE_BITS1) - 1)) << PTE_FILE_SHIFT1) \
- + ((((off) >> PTE_FILE_BITS1) & ((1U << PTE_FILE_BITS2) - 1)) \
- << PTE_FILE_SHIFT2) \
- + (((off) >> (PTE_FILE_BITS1 + PTE_FILE_BITS2)) \
- << PTE_FILE_SHIFT3) \
- + _PAGE_FILE })
+#define PTE_FILE_MASK1 ((1U << PTE_FILE_BITS1) - 1)
+#define PTE_FILE_MASK2 ((1U << PTE_FILE_BITS2) - 1)
+
+#define PTE_FILE_LSHIFT2 (PTE_FILE_BITS1)
+#define PTE_FILE_LSHIFT3 (PTE_FILE_BITS1 + PTE_FILE_BITS2)
+
+#define pte_to_pgoff(pte) \
+ (_mfrob((pte).pte_low, PTE_FILE_SHIFT1, PTE_FILE_MASK1, 0) + \
+ _mfrob((pte).pte_low, PTE_FILE_SHIFT2, PTE_FILE_MASK2, PTE_FILE_LSHIFT2) + \
+ __frob((pte).pte_low, PTE_FILE_SHIFT3, PTE_FILE_LSHIFT3))
+
+#define pgoff_to_pte(off) \
+ ((pte_t) { .pte_low = \
+ _mfrob(off, 0, PTE_FILE_MASK1, PTE_FILE_SHIFT1) + \
+ _mfrob(off, PTE_FILE_LSHIFT2, PTE_FILE_MASK2, PTE_FILE_SHIFT2) + \
+ __frob(off, PTE_FILE_LSHIFT3, PTE_FILE_SHIFT3) + \
+ _PAGE_FILE })

#endif /* CONFIG_MEM_SOFT_DIRTY */

_


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