[PATCH -mm] mm: Unify pte_to_pgoff and pgoff_to_pte helpers

[PATCH -mm] mm: Unify pte_to_pgoff and pgoff_to_pte helpers

[Cyrill Gorcunov]

Use unified pte_bfop helper to manipulate bits in pte/pgoff bitfield.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Matt Mackall <mpm@selenic.com>
Cc: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
---
 arch/x86/include/asm/pgtable-2level.h |   51 ++++++++++++++++++----------------
 1 file changed, 27 insertions(+), 24 deletions(-)

Index: linux-2.6.git/arch/x86/include/asm/pgtable-2level.h
===================================================================
--- linux-2.6.git.orig/arch/x86/include/asm/pgtable-2level.h
+++ linux-2.6.git/arch/x86/include/asm/pgtable-2level.h
@@ -55,8 +55,11 @@ 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))
+/*
+ * For readable bitfield manipulations.
+ */
+#define PTE_FILE_NOMASK		(-1U)
+#define pte_bfop(v,r,m,l)	((((v) >> (r)) & (m)) << (l))
 
 #ifdef CONFIG_MEM_SOFT_DIRTY
 
@@ -82,18 +85,18 @@ static inline pmd_t native_pmdp_get_and_
 #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)			+	\
+#define pte_to_pgoff(pte)								  \
+	(pte_bfop((pte).pte_low, PTE_FILE_SHIFT1, PTE_FILE_MASK1, 0)			+ \
+	 pte_bfop((pte).pte_low, PTE_FILE_SHIFT2, PTE_FILE_MASK2, PTE_FILE_LSHIFT2)	+ \
+	 pte_bfop((pte).pte_low, PTE_FILE_SHIFT3, PTE_FILE_MASK3, PTE_FILE_LSHIFT3)	+ \
+	 pte_bfop((pte).pte_low, PTE_FILE_SHIFT4, PTE_FILE_NOMASK, PTE_FILE_LSHIFT4))
+
+#define pgoff_to_pte(off)							  \
+	((pte_t) { .pte_low =							  \
+	pte_bfop(off,                0, PTE_FILE_MASK1, PTE_FILE_SHIFT1)	+ \
+	pte_bfop(off, PTE_FILE_LSHIFT2, PTE_FILE_MASK2, PTE_FILE_SHIFT2)	+ \
+	pte_bfop(off, PTE_FILE_LSHIFT3, PTE_FILE_MASK3, PTE_FILE_SHIFT3)	+ \
+	pte_bfop(off, PTE_FILE_LSHIFT4, PTE_FILE_NOMASK, PTE_FILE_SHIFT4)	+ \
 	_PAGE_FILE })
 
 #else /* CONFIG_MEM_SOFT_DIRTY */
@@ -120,16 +123,16 @@ static inline pmd_t native_pmdp_get_and_
 #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)			+	\
+#define pte_to_pgoff(pte)								  \
+	(pte_bfop((pte).pte_low, PTE_FILE_SHIFT1, PTE_FILE_MASK1, 0)			+ \
+	 pte_bfop((pte).pte_low, PTE_FILE_SHIFT2, PTE_FILE_MASK2, PTE_FILE_LSHIFT2)	+ \
+	 pte_bfop((pte).pte_low, PTE_FILE_SHIFT3, PTE_FILE_NOMASK, PTE_FILE_LSHIFT3))
+
+#define pgoff_to_pte(off)							  \
+	((pte_t) { .pte_low =							  \
+	pte_bfop(off,                0, PTE_FILE_MASK1, PTE_FILE_SHIFT1)	+ \
+	pte_bfop(off, PTE_FILE_LSHIFT2, PTE_FILE_MASK2, PTE_FILE_SHIFT2)	+ \
+	pte_bfop(off, PTE_FILE_LSHIFT3, PTE_FILE_NOMASK, PTE_FILE_SHIFT3)	+ \
 	_PAGE_FILE })
 
 #endif /* CONFIG_MEM_SOFT_DIRTY */

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Re: [PATCH -mm] mm: Unify pte_to_pgoff and pgoff_to_pte helpers

[H. Peter Anvin]

On 08/14/2013 12:00 AM, Cyrill Gorcunov wrote:
> +#define pte_bfop(v,r,m,l)	((((v) >> (r)) & (m)) << (l))

"bfop"?

	-hpa


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Re: [PATCH -mm] mm: Unify pte_to_pgoff and pgoff_to_pte helpers

[Cyrill Gorcunov]

On Wed, Aug 14, 2013 at 12:22:37AM -0700, H. Peter Anvin wrote:
> On 08/14/2013 12:00 AM, Cyrill Gorcunov wrote:
> > +#define pte_bfop(v,r,m,l)	((((v) >> (r)) & (m)) << (l))
> 
> "bfop"?

B_it_F_ield_OP_eration, Peter I don't mind to use any other
name, this was just short enough to type.

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Re: [PATCH -mm] mm: Unify pte_to_pgoff and pgoff_to_pte helpers

[H. Peter Anvin]

On 08/14/2013 12:24 AM, Cyrill Gorcunov wrote:
> On Wed, Aug 14, 2013 at 12:22:37AM -0700, H. Peter Anvin wrote:
>> On 08/14/2013 12:00 AM, Cyrill Gorcunov wrote:
>>> +#define pte_bfop(v,r,m,l)	((((v) >> (r)) & (m)) << (l))
>>
>> "bfop"?
> 
> B_it_F_ield_OP_eration, Peter I don't mind to use any other
> name, this was just short enough to type.
> 

I think it would be useful to have a comment what it means and what
v,r,m,l represent.

Perhaps m should be mask width rather than the actual mask?

	-hpa

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Re: [PATCH -mm] mm: Unify pte_to_pgoff and pgoff_to_pte helpers

[Andrew Morton]

On Wed, 14 Aug 2013 00:31:12 -0700 "H. Peter Anvin" <hpa@zytor.com> wrote:

> On 08/14/2013 12:24 AM, Cyrill Gorcunov wrote:
> > On Wed, Aug 14, 2013 at 12:22:37AM -0700, H. Peter Anvin wrote:
> >> On 08/14/2013 12:00 AM, Cyrill Gorcunov wrote:
> >>> +#define pte_bfop(v,r,m,l)	((((v) >> (r)) & (m)) << (l))
> >>
> >> "bfop"?
> > 
> > B_it_F_ield_OP_eration, Peter I don't mind to use any other
> > name, this was just short enough to type.
> > 
> 
> I think it would be useful to have a comment what it means and what
> v,r,m,l represent.

Can it be written in C with types and proper variable names and such
radical stuff?

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Re: [PATCH -mm] mm: Unify pte_to_pgoff and pgoff_to_pte helpers

[Cyrill Gorcunov]

On Wed, Aug 14, 2013 at 12:33:36AM -0700, Andrew Morton wrote:
> > > B_it_F_ield_OP_eration, Peter I don't mind to use any other
> > > name, this was just short enough to type.
> > > 
> > 
> > I think it would be useful to have a comment what it means and what
> > v,r,m,l represent.

Sure, maybe simply better names as value, rshift, mask, lshift would
look more understandable. I'll try to use width for mask as well
(which reminds me BFEXT helpers Andrew mentioned in this thread).

> Can it be written in C with types and proper variable names and such
> radical stuff?

Could you elaborate? You mean inline helper or macro with type checks?

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Re: [PATCH -mm] mm: Unify pte_to_pgoff and pgoff_to_pte helpers

[Andrew Morton]

On Wed, 14 Aug 2013 11:43:33 +0400 Cyrill Gorcunov <gorcunov@gmail.com> wrote:

> On Wed, Aug 14, 2013 at 12:33:36AM -0700, Andrew Morton wrote:
> > > > B_it_F_ield_OP_eration, Peter I don't mind to use any other
> > > > name, this was just short enough to type.
> > > > 
> > > 
> > > I think it would be useful to have a comment what it means and what
> > > v,r,m,l represent.
> 
> Sure, maybe simply better names as value, rshift, mask, lshift would
> look more understandable. I'll try to use width for mask as well
> (which reminds me BFEXT helpers Andrew mentioned in this thread).
> 
> > Can it be written in C with types and proper variable names and such
> > radical stuff?
> 
> Could you elaborate? You mean inline helper or macro with type checks?

/*
 * description goes here
 */
static inline pteval_t pte_bfop(pteval_t val, int rightshift, ...)
{
	...
}

So much better!  We really should only implement code in a macro if it
*has* to be done as a macro and I don't think that's the case here?

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Re: [PATCH -mm] mm: Unify pte_to_pgoff and pgoff_to_pte helpers

[Cyrill Gorcunov]

On Wed, Aug 14, 2013 at 01:08:56AM -0700, Andrew Morton wrote:
> > 
> > > Can it be written in C with types and proper variable names and such
> > > radical stuff?
> > 
> > Could you elaborate? You mean inline helper or macro with type checks?
> 
> /*
>  * description goes here
>  */
> static inline pteval_t pte_bfop(pteval_t val, int rightshift, ...)
> {
> 	...
> }
> 
> So much better!  We really should only implement code in a macro if it
> *has* to be done as a macro and I don't think that's the case here?

Well, I'll have to check if it really doesn't generate additional
instructions in generated code, since it's hotpath. I'll ping back
once things are done.

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Re: [PATCH -mm] mm: Unify pte_to_pgoff and pgoff_to_pte helpers

[Ingo Molnar]

* Cyrill Gorcunov <gorcunov@gmail.com> wrote:

> On Wed, Aug 14, 2013 at 01:08:56AM -0700, Andrew Morton wrote:
> > > 
> > > > Can it be written in C with types and proper variable names and such
> > > > radical stuff?
> > > 
> > > Could you elaborate? You mean inline helper or macro with type checks?
> > 
> > /*
> >  * description goes here
> >  */
> > static inline pteval_t pte_bfop(pteval_t val, int rightshift, ...)
> > {
> > 	...
> > }
> > 
> > So much better!  We really should only implement code in a macro if it
> > *has* to be done as a macro and I don't think that's the case here?
> 
> Well, I'll have to check if it really doesn't generate additional 
> instructions in generated code, since it's hotpath. I'll ping back once 
> things are done.

An __always_inline should never do that.

Thanks,

	Ingo

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Re: [PATCH -mm] mm: Unify pte_to_pgoff and pgoff_to_pte helpers

[Cyrill Gorcunov]

On Wed, Aug 14, 2013 at 11:50:14AM +0200, Ingo Molnar wrote:
> > 
> > Well, I'll have to check if it really doesn't generate additional 
> > instructions in generated code, since it's hotpath. I'll ping back once 
> > things are done.
> 
> An __always_inline should never do that.

Here is the final one, please ping me if something looks not as clean
as it wanted to be and i'll tune code up, thanks!

To hpa@: I had to use explicit @mask because it allows to pass -1ul
mask which is optimized off then by a compiler.
---
From: Cyrill Gorcunov <gorcunov@gmail.com>
Subject: [PATCH -mm] mm: Unify pte_to_pgoff and pgoff_to_pte helpers

Use unified pte_bfop helper to manipulate bits in pte/pgoff bitfield,
and convert pte_to_pgoff/pgoff_to_pte to inlines.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Matt Mackall <mpm@selenic.com>
Cc: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
---
 arch/x86/include/asm/pgtable-2level.h |   70 +++++++++++++++++++++-------------
 1 file changed, 44 insertions(+), 26 deletions(-)

Index: linux-2.6.git/arch/x86/include/asm/pgtable-2level.h
===================================================================
--- linux-2.6.git.orig/arch/x86/include/asm/pgtable-2level.h
+++ linux-2.6.git/arch/x86/include/asm/pgtable-2level.h
@@ -55,8 +55,12 @@ 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))
+/* Bit manipulation helper on pte/pgoff entry */
+static inline unsigned long pte_bfop(unsigned long value, unsigned int rightshift,
+				     unsigned long mask, unsigned int leftshift)
+{
+	return ((value >> rightshift) & mask) << leftshift;
+}
 
 #ifdef CONFIG_MEM_SOFT_DIRTY
 
@@ -82,19 +86,26 @@ static inline pmd_t native_pmdp_get_and_
 #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 })
+static __always_inline pgoff_t pte_to_pgoff(pte_t pte)
+{
+	return (pgoff_t)
+		(pte_bfop(pte.pte_low, PTE_FILE_SHIFT1, PTE_FILE_MASK1,  0)		   +
+		 pte_bfop(pte.pte_low, PTE_FILE_SHIFT2, PTE_FILE_MASK2,  PTE_FILE_LSHIFT2) +
+		 pte_bfop(pte.pte_low, PTE_FILE_SHIFT3, PTE_FILE_MASK3,  PTE_FILE_LSHIFT3) +
+		 pte_bfop(pte.pte_low, PTE_FILE_SHIFT4,           -1UL,  PTE_FILE_LSHIFT4));
+}
+
+static __always_inline pte_t pgoff_to_pte(pgoff_t off)
+{
+	return (pte_t){
+		.pte_low =
+			pte_bfop(off,                0, PTE_FILE_MASK1,  PTE_FILE_SHIFT1) +
+			pte_bfop(off, PTE_FILE_LSHIFT2, PTE_FILE_MASK2,  PTE_FILE_SHIFT2) +
+			pte_bfop(off, PTE_FILE_LSHIFT3, PTE_FILE_MASK3,  PTE_FILE_SHIFT3) +
+			pte_bfop(off, PTE_FILE_LSHIFT4,           -1UL,  PTE_FILE_SHIFT4) +
+			_PAGE_FILE,
+	};
+}
 
 #else /* CONFIG_MEM_SOFT_DIRTY */
 
@@ -120,17 +131,24 @@ static inline pmd_t native_pmdp_get_and_
 #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 })
+static __always_inline pgoff_t pte_to_pgoff(pte_t pte)
+{
+	return (pgoff_t)
+		(pte_bfop(pte.pte_low, PTE_FILE_SHIFT1, PTE_FILE_MASK1,  0)		   +
+		 pte_bfop(pte.pte_low, PTE_FILE_SHIFT2, PTE_FILE_MASK2,  PTE_FILE_LSHIFT2) +
+		 pte_bfop(pte.pte_low, PTE_FILE_SHIFT3,           -1UL,  PTE_FILE_LSHIFT3));
+}
+
+static __always_inline pte_t pgoff_to_pte(pgoff_t off)
+{
+	return (pte_t){
+		.pte_low =
+			pte_bfop(off,                0, PTE_FILE_MASK1,  PTE_FILE_SHIFT1) +
+			pte_bfop(off, PTE_FILE_LSHIFT2, PTE_FILE_MASK2,  PTE_FILE_SHIFT2) +
+			pte_bfop(off, PTE_FILE_LSHIFT3,           -1UL,  PTE_FILE_SHIFT3) +
+			_PAGE_FILE,
+	};
+}
 
 #endif /* CONFIG_MEM_SOFT_DIRTY */
 

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