From: Arnd Bergmann <[email protected]>
do_div() is only well-behaved for positive numbers, and now warns
when the first argument is a an s64:
net/netfilter/ipvs/ip_vs_est.c: In function 'ip_vs_est_calc_limits':
include/asm-generic/div64.h:222:35: error: comparison of distinct pointer types lacks a cast [-Werror]
222 | (void)(((typeof((n)) *)0) == ((uint64_t *)0)); \
| ^~
net/netfilter/ipvs/ip_vs_est.c:694:17: note: in expansion of macro 'do_div'
694 | do_div(val, loops);
Convert to using the more appropriate div_s64(), which also
simplifies the code a bit.
Fixes: 705dd3444081 ("ipvs: use kthreads for stats estimation")
Signed-off-by: Arnd Bergmann <[email protected]>
---
net/netfilter/ipvs/ip_vs_est.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/net/netfilter/ipvs/ip_vs_est.c b/net/netfilter/ipvs/ip_vs_est.c
index ce2a1549b304..dbc32f8cf1f9 100644
--- a/net/netfilter/ipvs/ip_vs_est.c
+++ b/net/netfilter/ipvs/ip_vs_est.c
@@ -691,15 +691,13 @@ static int ip_vs_est_calc_limits(struct netns_ipvs *ipvs, int *chain_max)
}
if (diff >= NSEC_PER_SEC)
continue;
- val = diff;
- do_div(val, loops);
+ val = div_s64(diff, loops);
if (!min_est || val < min_est) {
min_est = val;
/* goal: 95usec per chain */
val = 95 * NSEC_PER_USEC;
if (val >= min_est) {
- do_div(val, min_est);
- max = (int)val;
+ max = div_s64(val, min_est);
} else {
max = 1;
}
--
2.35.1
Hello,
On Thu, 15 Dec 2022, Arnd Bergmann wrote:
> From: Arnd Bergmann <[email protected]>
>
> do_div() is only well-behaved for positive numbers, and now warns
> when the first argument is a an s64:
>
> net/netfilter/ipvs/ip_vs_est.c: In function 'ip_vs_est_calc_limits':
> include/asm-generic/div64.h:222:35: error: comparison of distinct pointer types lacks a cast [-Werror]
> 222 | (void)(((typeof((n)) *)0) == ((uint64_t *)0)); \
> | ^~
> net/netfilter/ipvs/ip_vs_est.c:694:17: note: in expansion of macro 'do_div'
> 694 | do_div(val, loops);
net-next already contains fix for this warning
and changes val to u64.
> Convert to using the more appropriate div_s64(), which also
> simplifies the code a bit.
>
> Fixes: 705dd3444081 ("ipvs: use kthreads for stats estimation")
> Signed-off-by: Arnd Bergmann <[email protected]>
> ---
> net/netfilter/ipvs/ip_vs_est.c | 6 ++----
> 1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/net/netfilter/ipvs/ip_vs_est.c b/net/netfilter/ipvs/ip_vs_est.c
> index ce2a1549b304..dbc32f8cf1f9 100644
> --- a/net/netfilter/ipvs/ip_vs_est.c
> +++ b/net/netfilter/ipvs/ip_vs_est.c
> @@ -691,15 +691,13 @@ static int ip_vs_est_calc_limits(struct netns_ipvs *ipvs, int *chain_max)
> }
> if (diff >= NSEC_PER_SEC)
> continue;
> - val = diff;
> - do_div(val, loops);
> + val = div_s64(diff, loops);
On CONFIG_X86_32 both versions execute single divl
for our case but div_s64 is not inlined. I'm not expert in
this area but if you think div_u64 is more appropriate then
post another patch. Note that now val is u64 and
min_est is still s32 (can be u32).
> if (!min_est || val < min_est) {
> min_est = val;
> /* goal: 95usec per chain */
> val = 95 * NSEC_PER_USEC;
> if (val >= min_est) {
> - do_div(val, min_est);
> - max = (int)val;
> + max = div_s64(val, min_est);
> } else {
> max = 1;
> }
> --
> 2.35.1
Regards
--
Julian Anastasov <[email protected]>
Hi Julian,
On Thu, Dec 15, 2022 at 09:01:59PM +0200, Julian Anastasov wrote:
>
> Hello,
>
> On Thu, 15 Dec 2022, Arnd Bergmann wrote:
>
> > From: Arnd Bergmann <[email protected]>
> >
> > do_div() is only well-behaved for positive numbers, and now warns
> > when the first argument is a an s64:
> >
> > net/netfilter/ipvs/ip_vs_est.c: In function 'ip_vs_est_calc_limits':
> > include/asm-generic/div64.h:222:35: error: comparison of distinct pointer types lacks a cast [-Werror]
> > 222 | (void)(((typeof((n)) *)0) == ((uint64_t *)0)); \
> > | ^~
> > net/netfilter/ipvs/ip_vs_est.c:694:17: note: in expansion of macro 'do_div'
> > 694 | do_div(val, loops);
>
> net-next already contains fix for this warning
> and changes val to u64.
Arnd's patch applies fine on top of net-next, maybe he is addressing
something else?
> > Convert to using the more appropriate div_s64(), which also
> > simplifies the code a bit.
> >
> > Fixes: 705dd3444081 ("ipvs: use kthreads for stats estimation")
> > Signed-off-by: Arnd Bergmann <[email protected]>
> > ---
> > net/netfilter/ipvs/ip_vs_est.c | 6 ++----
> > 1 file changed, 2 insertions(+), 4 deletions(-)
> >
> > diff --git a/net/netfilter/ipvs/ip_vs_est.c b/net/netfilter/ipvs/ip_vs_est.c
> > index ce2a1549b304..dbc32f8cf1f9 100644
> > --- a/net/netfilter/ipvs/ip_vs_est.c
> > +++ b/net/netfilter/ipvs/ip_vs_est.c
> > @@ -691,15 +691,13 @@ static int ip_vs_est_calc_limits(struct netns_ipvs *ipvs, int *chain_max)
> > }
> > if (diff >= NSEC_PER_SEC)
> > continue;
> > - val = diff;
> > - do_div(val, loops);
> > + val = div_s64(diff, loops);
>
> On CONFIG_X86_32 both versions execute single divl
> for our case but div_s64 is not inlined. I'm not expert in
> this area but if you think div_u64 is more appropriate then
> post another patch. Note that now val is u64 and
> min_est is still s32 (can be u32).
>
> > if (!min_est || val < min_est) {
> > min_est = val;
> > /* goal: 95usec per chain */
> > val = 95 * NSEC_PER_USEC;
> > if (val >= min_est) {
> > - do_div(val, min_est);
> > - max = (int)val;
> > + max = div_s64(val, min_est);
> > } else {
> > max = 1;
> > }
> > --
> > 2.35.1
>
> Regards
>
> --
> Julian Anastasov <[email protected]>
>
On Fri, Dec 16, 2022, at 11:10, Pablo Neira Ayuso wrote:
> Hi Julian,
>
> On Thu, Dec 15, 2022 at 09:01:59PM +0200, Julian Anastasov wrote:
>>
>> Hello,
>>
>> On Thu, 15 Dec 2022, Arnd Bergmann wrote:
>>
>> > From: Arnd Bergmann <[email protected]>
>> >
>> > do_div() is only well-behaved for positive numbers, and now warns
>> > when the first argument is a an s64:
>> >
>> > net/netfilter/ipvs/ip_vs_est.c: In function 'ip_vs_est_calc_limits':
>> > include/asm-generic/div64.h:222:35: error: comparison of distinct pointer types lacks a cast [-Werror]
>> > 222 | (void)(((typeof((n)) *)0) == ((uint64_t *)0)); \
>> > | ^~
>> > net/netfilter/ipvs/ip_vs_est.c:694:17: note: in expansion of macro 'do_div'
>> > 694 | do_div(val, loops);
>>
>> net-next already contains fix for this warning
>> and changes val to u64.
>
> Arnd's patch applies fine on top of net-next, maybe he is addressing
> something else?
No, it's the same bug. I had prepared my patch before the other fix
went in, and only one of the two is needed.
FWIW, I find my version slightly more readable, but Jakub's fix
is probably more efficient, because the unsigned 64-bit division
is better optimized on 32-bit, while div_s64() goes through an
extern function.
Arnd