Re: [PATCH 07/10] powerpc/mm/slice: Switch to 3-operand slice bitops helpers

[Nicholas Piggin]

On Tue, 6 Mar 2018 15:44:46 +0100
Christophe LEROY  wrote:

> Le 06/03/2018 à 14:25, Nicholas Piggin a écrit :
> > This converts the slice_mask bit operation helpers to be the usual
> > 3-operand kind, which is clearer to work with.  
> 
> What's the real benefit of doing that ?

One or two places where we want to combine 2 const input bitmaps
and can avoid the extra copy in the next patch.

E.g., slice_or_mask(_mask, maskp, compat_maskp);

> 
> It is helps for a subsequent patch, say it.

Fair point, I'll add to the changelog.

> > @@ -433,25 +433,33 @@ static unsigned long slice_find_area(struct mm_struct 
> > *mm, unsigned long len,
> > return slice_find_area_bottomup(mm, len, mask, psize, 
> > high_limit);
> >   }
> >   
> > -static inline void slice_or_mask(struct slice_mask *dst,
> > +static inline void slice_copy_mask(struct slice_mask *dst,
> > const struct slice_mask *src)  
> 
> This new function is not used, the compiler while probably not be happy.

I think it doesn't get so grumpy with inlines (otherwise we'd have a lot
of problems of headers). Usually I think the new function should go into
the patch where it's first used, but this being a self contained helper,
I thought it fit better to add here. Maybe I'm wrong, I can move it.

Re: [PATCH 07/10] powerpc/mm/slice: Switch to 3-operand slice bitops helpers

[Christophe LEROY]

Le 06/03/2018 à 14:25, Nicholas Piggin a écrit :

This converts the slice_mask bit operation helpers to be the usual
3-operand kind, which is clearer to work with.


What's the real benefit of doing that ?

It is helps for a subsequent patch, say it.
Otherwise, I really can't see the point.



Signed-off-by: Nicholas Piggin 
---
  arch/powerpc/mm/slice.c | 38 +++---
  1 file changed, 23 insertions(+), 15 deletions(-)

diff --git a/arch/powerpc/mm/slice.c b/arch/powerpc/mm/slice.c
index 3841fca75006..46daa1d1794f 100644
--- a/arch/powerpc/mm/slice.c
+++ b/arch/powerpc/mm/slice.c
@@ -433,25 +433,33 @@ static unsigned long slice_find_area(struct mm_struct 
*mm, unsigned long len,
return slice_find_area_bottomup(mm, len, mask, psize, 
high_limit);
  }
  
-static inline void slice_or_mask(struct slice_mask *dst,

+static inline void slice_copy_mask(struct slice_mask *dst,
const struct slice_mask *src)


This new function is not used, the compiler while probably not be happy.

Christophe


  {
-   dst->low_slices |= src->low_slices;
+   dst->low_slices = src->low_slices;
if (!SLICE_NUM_HIGH)
return;
-   bitmap_or(dst->high_slices, dst->high_slices, src->high_slices,
- SLICE_NUM_HIGH);
+   bitmap_copy(dst->high_slices, src->high_slices, SLICE_NUM_HIGH);
  }
  
-static inline void slice_andnot_mask(struct slice_mask *dst,

-   const struct slice_mask *src)
+static inline void slice_or_mask(struct slice_mask *dst,
+   const struct slice_mask *src1,
+   const struct slice_mask *src2)
  {
-   dst->low_slices &= ~src->low_slices;
+   dst->low_slices = src1->low_slices | src2->low_slices;
+   if (!SLICE_NUM_HIGH)
+   return;
+   bitmap_or(dst->high_slices, src1->high_slices, src2->high_slices, 
SLICE_NUM_HIGH);
+}
  
+static inline void slice_andnot_mask(struct slice_mask *dst,

+   const struct slice_mask *src1,
+   const struct slice_mask *src2)
+{
+   dst->low_slices = src1->low_slices & ~src2->low_slices;
if (!SLICE_NUM_HIGH)
return;
-   bitmap_andnot(dst->high_slices, dst->high_slices, src->high_slices,
- SLICE_NUM_HIGH);
+   bitmap_andnot(dst->high_slices, src1->high_slices, src2->high_slices, 
SLICE_NUM_HIGH);
  }
  
  #ifdef CONFIG_PPC_64K_PAGES

@@ -566,7 +574,7 @@ unsigned long slice_get_unmapped_area(unsigned long addr, 
unsigned long len,
if (psize == MMU_PAGE_64K) {
compat_mask = *slice_mask_for_size(mm, MMU_PAGE_4K);
if (fixed)
-   slice_or_mask(_mask, _mask);
+   slice_or_mask(_mask, _mask, _mask);
}
  #endif
  
@@ -598,7 +606,7 @@ unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len,

 * empty and thus can be converted
 */
slice_mask_for_free(mm, _mask, high_limit);
-   slice_or_mask(_mask, _mask);
+   slice_or_mask(_mask, _mask, _mask);
slice_print_mask(" potential", _mask);
  
  	if (addr || fixed) {

@@ -635,7 +643,7 @@ unsigned long slice_get_unmapped_area(unsigned long addr, 
unsigned long len,
  #ifdef CONFIG_PPC_64K_PAGES
if (addr == -ENOMEM && psize == MMU_PAGE_64K) {
/* retry the search with 4k-page slices included */
-   slice_or_mask(_mask, _mask);
+   slice_or_mask(_mask, _mask, _mask);
addr = slice_find_area(mm, len, _mask,
   psize, topdown, high_limit);
}
@@ -649,8 +657,8 @@ unsigned long slice_get_unmapped_area(unsigned long addr, 
unsigned long len,
slice_print_mask(" mask", );
  
   convert:

-   slice_andnot_mask(, _mask);
-   slice_andnot_mask(, _mask);
+   slice_andnot_mask(, , _mask);
+   slice_andnot_mask(, , _mask);
if (mask.low_slices ||
(SLICE_NUM_HIGH &&
 !bitmap_empty(mask.high_slices, SLICE_NUM_HIGH))) {
@@ -790,7 +798,7 @@ int is_hugepage_only_range(struct mm_struct *mm, unsigned 
long addr,
if (psize == MMU_PAGE_64K) {
struct slice_mask compat_mask;
compat_mask = *slice_mask_for_size(mm, MMU_PAGE_4K);
-   slice_or_mask(, _mask);
+   slice_or_mask(, , _mask);
}
  #endif