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SubjectRe: [PATCH net-next] bonding: Use do_div to divide 64 bit numbers
On 01/23/2014 09:44 PM, Nikolay Aleksandrov wrote:
> On 01/23/2014 07:47 PM, Zoltan Kiss wrote:
>> Nikolay Aleksandrov's recent bonding option API changes (25a9b54a and e4994612)
>> introduced u64 as the type of downdelay and updelay. On 32 bit the division and
>> modulo operations cause compile errors:
>>
>> ERROR: "__udivdi3" [drivers/net/bonding/bonding.ko] undefined!
>> ERROR: "__umoddi3" [drivers/net/bonding/bonding.ko] undefined!
>>
>> This patch use the do_div macro, which guaranteed to do the right thing.
>>
>> Signed-off-by: Zoltan Kiss <zoltan.kiss@citrix.com>
>> ---
>> drivers/net/bonding/bond_options.c | 19 +++++++++++--------
>> 1 file changed, 11 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/net/bonding/bond_options.c b/drivers/net/bonding/bond_options.c
>> index 4cee04a..4f94907 100644
>> --- a/drivers/net/bonding/bond_options.c
>> +++ b/drivers/net/bonding/bond_options.c
>> @@ -18,6 +18,7 @@
>> #include <linux/rcupdate.h>
>> #include <linux/ctype.h>
>> #include <linux/inet.h>
>> +#include <asm/div64.h>
>> #include "bonding.h"
>>
>> static struct bond_opt_value bond_mode_tbl[] = {
>> @@ -727,19 +728,20 @@ int bond_option_miimon_set(struct bonding *bond, struct bond_opt_value *newval)
>>
>> int bond_option_updelay_set(struct bonding *bond, struct bond_opt_value *newval)
>> {
>> + u64 quotient = newval->value;
>> + u64 remainder = do_div(quotient, bond->params.miimon);
> Hi Zoltan,
> Thanks for fixing this, a few comments though:
> bond->params.miimon can be 0 here that's why there's a check afterwards,
> also please separate the local variable definitions from the body with a
> new line.
> The same applies for downdelay.
>
> Nik
In fact since we don't need the u64 and newval->value is limited to
INT_MAX, can't we simply cast it to (int) and avoid the do_div entirely ?

>> if (!bond->params.miimon) {
>> pr_err("%s: Unable to set up delay as MII monitoring is disabled\n",
>> bond->dev->name);
>> return -EPERM;
>> }
>> - if ((newval->value % bond->params.miimon) != 0) {
>> + if (remainder != 0) {
>> pr_warn("%s: Warning: up delay (%llu) is not a multiple of miimon (%d), updelay rounded to %llu ms\n",
>> bond->dev->name, newval->value,
>> bond->params.miimon,
>> - (newval->value / bond->params.miimon) *
>> - bond->params.miimon);
>> + quotient * bond->params.miimon);
>> }
>> - bond->params.updelay = newval->value / bond->params.miimon;
>> + bond->params.updelay = quotient;
>> pr_info("%s: Setting up delay to %d.\n",
>> bond->dev->name,
>> bond->params.updelay * bond->params.miimon);
>> @@ -750,19 +752,20 @@ int bond_option_updelay_set(struct bonding *bond, struct bond_opt_value *newval)
>> int bond_option_downdelay_set(struct bonding *bond,
>> struct bond_opt_value *newval)
>> {
>> + u64 quotient = newval->value;
>> + u64 remainder = do_div(quotient, bond->params.miimon);
>> if (!bond->params.miimon) {
>> pr_err("%s: Unable to set down delay as MII monitoring is disabled\n",
>> bond->dev->name);
>> return -EPERM;
>> }
>> - if ((newval->value % bond->params.miimon) != 0) {
>> + if (remainder != 0) {
>> pr_warn("%s: Warning: down delay (%llu) is not a multiple of miimon (%d), delay rounded to %llu ms\n",
>> bond->dev->name, newval->value,
>> bond->params.miimon,
>> - (newval->value / bond->params.miimon) *
>> - bond->params.miimon);
>> + quotient * bond->params.miimon);
>> }
>> - bond->params.downdelay = newval->value / bond->params.miimon;
>> + bond->params.downdelay = quotient;
>> pr_info("%s: Setting down delay to %d.\n",
>> bond->dev->name,
>> bond->params.downdelay * bond->params.miimon);
>>
>
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