* [PATCH v2] lib/bitmap: Make parameter len unsigned
@ 2022-07-08 7:52 Paul Menzel
2022-07-08 14:38 ` Yury Norov
0 siblings, 1 reply; 3+ messages in thread
From: Paul Menzel @ 2022-07-08 7:52 UTC (permalink / raw)
To: Yury Norov, Andy Shevchenko, Rasmus Villemoes; +Cc: Paul Menzel, linux-kernel
The length is non-negative, so make it unsigned.
Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
---
v2: Update signature in header file
include/linux/bitmap.h | 2 +-
lib/bitmap.c | 4 ++--
2 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index 2e6cd5681040..feaf84cbc487 100644
--- a/include/linux/bitmap.h
+++ b/include/linux/bitmap.h
@@ -164,7 +164,7 @@ bool __bitmap_intersects(const unsigned long *bitmap1,
bool __bitmap_subset(const unsigned long *bitmap1,
const unsigned long *bitmap2, unsigned int nbits);
int __bitmap_weight(const unsigned long *bitmap, unsigned int nbits);
-void __bitmap_set(unsigned long *map, unsigned int start, int len);
+void __bitmap_set(unsigned long *map, unsigned int start, unsigned int len);
void __bitmap_clear(unsigned long *map, unsigned int start, int len);
unsigned long bitmap_find_next_zero_area_off(unsigned long *map,
diff --git a/lib/bitmap.c b/lib/bitmap.c
index b18e31ea6e66..0746beb336df 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -348,14 +348,14 @@ int __bitmap_weight(const unsigned long *bitmap, unsigned int bits)
}
EXPORT_SYMBOL(__bitmap_weight);
-void __bitmap_set(unsigned long *map, unsigned int start, int len)
+void __bitmap_set(unsigned long *map, unsigned int start, unsigned int len)
{
unsigned long *p = map + BIT_WORD(start);
const unsigned int size = start + len;
int bits_to_set = BITS_PER_LONG - (start % BITS_PER_LONG);
unsigned long mask_to_set = BITMAP_FIRST_WORD_MASK(start);
- while (len - bits_to_set >= 0) {
+ while (len >= bits_to_set) {
*p |= mask_to_set;
len -= bits_to_set;
bits_to_set = BITS_PER_LONG;
--
2.36.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v2] lib/bitmap: Make parameter len unsigned
2022-07-08 7:52 [PATCH v2] lib/bitmap: Make parameter len unsigned Paul Menzel
@ 2022-07-08 14:38 ` Yury Norov
2022-07-09 12:27 ` Paul Menzel
0 siblings, 1 reply; 3+ messages in thread
From: Yury Norov @ 2022-07-08 14:38 UTC (permalink / raw)
To: Paul Menzel; +Cc: Andy Shevchenko, Rasmus Villemoes, linux-kernel
On Fri, Jul 08, 2022 at 09:52:40AM +0200, Paul Menzel wrote:
> The length is non-negative, so make it unsigned.
>
> Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
Hi Paul,
Can you please tell more about your motivation for fixing
__bitmap_set? The following __bitmap_clear has the same problem,
and bitmap_parse{,_user}, and bitmap_print_to_pagebuf, and
bitmap_parselist...
Is there a particular problem that is resolved after fixing
__bitmap_set()?
I'm OK if this is a single patch, but for a cleanup work it would
be more logical to clean everything in a single patch/series...
Thanks,
Yury
> ---
> v2: Update signature in header file
>
> include/linux/bitmap.h | 2 +-
> lib/bitmap.c | 4 ++--
> 2 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
> index 2e6cd5681040..feaf84cbc487 100644
> --- a/include/linux/bitmap.h
> +++ b/include/linux/bitmap.h
> @@ -164,7 +164,7 @@ bool __bitmap_intersects(const unsigned long *bitmap1,
> bool __bitmap_subset(const unsigned long *bitmap1,
> const unsigned long *bitmap2, unsigned int nbits);
> int __bitmap_weight(const unsigned long *bitmap, unsigned int nbits);
> -void __bitmap_set(unsigned long *map, unsigned int start, int len);
> +void __bitmap_set(unsigned long *map, unsigned int start, unsigned int len);
> void __bitmap_clear(unsigned long *map, unsigned int start, int len);
>
> unsigned long bitmap_find_next_zero_area_off(unsigned long *map,
> diff --git a/lib/bitmap.c b/lib/bitmap.c
> index b18e31ea6e66..0746beb336df 100644
> --- a/lib/bitmap.c
> +++ b/lib/bitmap.c
> @@ -348,14 +348,14 @@ int __bitmap_weight(const unsigned long *bitmap, unsigned int bits)
> }
> EXPORT_SYMBOL(__bitmap_weight);
>
> -void __bitmap_set(unsigned long *map, unsigned int start, int len)
> +void __bitmap_set(unsigned long *map, unsigned int start, unsigned int len)
> {
> unsigned long *p = map + BIT_WORD(start);
> const unsigned int size = start + len;
> int bits_to_set = BITS_PER_LONG - (start % BITS_PER_LONG);
> unsigned long mask_to_set = BITMAP_FIRST_WORD_MASK(start);
>
> - while (len - bits_to_set >= 0) {
> + while (len >= bits_to_set) {
> *p |= mask_to_set;
> len -= bits_to_set;
> bits_to_set = BITS_PER_LONG;
> --
> 2.36.1
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v2] lib/bitmap: Make parameter len unsigned
2022-07-08 14:38 ` Yury Norov
@ 2022-07-09 12:27 ` Paul Menzel
0 siblings, 0 replies; 3+ messages in thread
From: Paul Menzel @ 2022-07-09 12:27 UTC (permalink / raw)
To: Yury Norov; +Cc: Andy Shevchenko, Rasmus Villemoes, linux-kernel
Dear Yuri,
Thank you for your reply, and sorry for all the failure messages the
first version created.
Am 08.07.22 um 16:38 schrieb Yury Norov:
> On Fri, Jul 08, 2022 at 09:52:40AM +0200, Paul Menzel wrote:
>> The length is non-negative, so make it unsigned.
>>
>> Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
> Can you please tell more about your motivation for fixing
> __bitmap_set?
It’s just about semantics(?) that a count can’t be negative, and only
seems to generate tiny smaller code (less instructions):
```
__bitmap_set:
__bitmap_set:
movl %esi, %eax
movl %esi, %eax
movq %rdi, %r8 <
movl %esi, %ecx
movl %esi, %ecx
movl %edx, %edi |
movl %esi, %r8d
>
movl $64, %esi
>
andl $63, %ecx
shrl $6, %eax
shrl $6, %eax
andl $63, %esi |
movl %edx, %r9d
movq $-1, %rdx |
leaq (%rdi,%rax,8), %rax
leaq (%r8,%rax,8), %rax |
subl %ecx, %esi
leal -64(%rsi,%rdi), %r8d |
movq $-1, %rdi
salq %cl, %rdx |
salq %cl, %rdi
testl %r8d, %r8d |
cmpl %edx, %esi
js .L88 |
ja .L85
movl %r8d, %r9d <
shrl $6, %r9d <
leal 1(%r9), %esi <
leaq (%rax,%rsi,8), %rsi <
.L86: .L86:
orq %rdx, (%rax) |
subl %esi, %edx
>
orq %rdi, (%rax)
>
movl $64, %esi
addq $8, %rax
addq $8, %rax
movq $-1, %rdx |
movq $-1, %rdi
cmpq %rsi, %rax |
cmpl $63, %edx
jne .L86 |
ja .L86
sall $6, %r9d <
subl %r9d, %r8d <
.L85: .L85:
testl %r8d, %r8d |
testl %edx, %edx
je .L84
je .L84
addl %edi, %ecx |
leal (%r8,%r9), %ecx
movq $-1, %rax |
movq $-1, %rdx
negl %ecx
negl %ecx
shrq %cl, %rax |
shrq %cl, %rdx
andq %rax, %rdx |
andq %rdx, %rdi
orq %rdx, (%rsi) |
orq %rdi, (%rax)
.L84: .L84:
ret ret
.L88: <
movq %rax, %rsi <
movl %edi, %r8d <
jmp .L85 <
.size __bitmap_set, .-__bitmap_set
.size __bitmap_set, .-__bitmap_set
.p2align 4
.p2align 4
.globl __bitmap_clear
.globl __bitmap_clear
.type __bitmap_clear, @function
.type __bitmap_clear, @function
```
$ diff lib/bitmap.1.S lib/bitmap.2.S | diffstat
unknown | 55 ++++++++++++++++++++++++-------------------------------
1 file changed, 24 insertions(+), 31 deletions(-)
> The following __bitmap_clear has the same problem, and
> bitmap_parse{,_user}, and bitmap_print_to_pagebuf, and
> bitmap_parselist...
Indeed.
> Is there a particular problem that is resolved after fixing
> __bitmap_set()?
>
> I'm OK if this is a single patch, but for a cleanup work it would be
> more logical to clean everything in a single patch/series...
If you agree, I can change the other places too.
Kind regards,
Paul
^ permalink raw reply [flat|nested] 3+ messages in thread
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2022-07-08 7:52 [PATCH v2] lib/bitmap: Make parameter len unsigned Paul Menzel
2022-07-08 14:38 ` Yury Norov
2022-07-09 12:27 ` Paul Menzel
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