* [PATCH] block: Use div64_ul instead of do_div
@ 2021-11-17 1:03 cgel.zte
2021-11-18 3:40 ` [PATCH v2] " cgel.zte
0 siblings, 1 reply; 4+ messages in thread
From: cgel.zte @ 2021-11-17 1:03 UTC (permalink / raw)
To: tj; +Cc: axboe, cgroups, linux-block, linux-kernel, Changcheng Deng, Zeal Robot
From: Changcheng Deng <deng.changcheng@zte.com.cn>
do_div() does a 64-by-32 division. If the divisor is unsigned long, using
div64_ul can avoid truncation to 32-bit.
Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Changcheng Deng <deng.changcheng@zte.com.cn>
---
block/blk-throttle.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 39bb6e68a9a2..2db635d66617 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -1903,7 +1903,7 @@ static void throtl_downgrade_check(struct throtl_grp *tg)
if (tg->bps[READ][LIMIT_LOW]) {
bps = tg->last_bytes_disp[READ] * HZ;
- do_div(bps, elapsed_time);
+ div64_ul(bps, elapsed_time);
if (bps >= tg->bps[READ][LIMIT_LOW])
tg->last_low_overflow_time[READ] = now;
}
--
2.25.1
^ permalink raw reply [flat|nested] 4+ messages in thread* [PATCH v2] block: Use div64_ul instead of do_div
2021-11-17 1:03 [PATCH] block: Use div64_ul instead of do_div cgel.zte
@ 2021-11-18 3:40 ` cgel.zte
2021-11-29 18:19 ` Tejun Heo
2021-12-02 16:50 ` Michal Koutný
0 siblings, 2 replies; 4+ messages in thread
From: cgel.zte @ 2021-11-18 3:40 UTC (permalink / raw)
To: tj
Cc: axboe, cgroups, linux-block, linux-kernel, zealci, cgel.zte,
deng.changcheng
From: Changcheng Deng <deng.changcheng@zte.com.cn>
do_div() does a 64-by-32 division. Here the divisor is an unsigned long
which on some platforms is 64 bit wide. So use div64_ul instead of do_div
to avoid a possible truncation.
Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Changcheng Deng <deng.changcheng@zte.com.cn>
---
block/blk-throttle.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 39bb6e68a9a2..2db635d66617 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -1903,7 +1903,7 @@ static void throtl_downgrade_check(struct throtl_grp *tg)
if (tg->bps[READ][LIMIT_LOW]) {
bps = tg->last_bytes_disp[READ] * HZ;
- do_div(bps, elapsed_time);
+ bps = div64_ul(bps, elapsed_time);
if (bps >= tg->bps[READ][LIMIT_LOW])
tg->last_low_overflow_time[READ] = now;
}
--
2.25.1
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH v2] block: Use div64_ul instead of do_div
2021-11-18 3:40 ` [PATCH v2] " cgel.zte
@ 2021-11-29 18:19 ` Tejun Heo
2021-12-02 16:50 ` Michal Koutný
1 sibling, 0 replies; 4+ messages in thread
From: Tejun Heo @ 2021-11-29 18:19 UTC (permalink / raw)
To: cgel.zte
Cc: axboe, cgroups, linux-block, linux-kernel, zealci, deng.changcheng
On Thu, Nov 18, 2021 at 03:40:33AM +0000, cgel.zte@gmail.com wrote:
> From: Changcheng Deng <deng.changcheng@zte.com.cn>
>
> do_div() does a 64-by-32 division. Here the divisor is an unsigned long
> which on some platforms is 64 bit wide. So use div64_ul instead of do_div
> to avoid a possible truncation.
>
> Reported-by: Zeal Robot <zealci@zte.com.cn>
> Signed-off-by: Changcheng Deng <deng.changcheng@zte.com.cn>
> ---
> block/blk-throttle.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/block/blk-throttle.c b/block/blk-throttle.c
> index 39bb6e68a9a2..2db635d66617 100644
> --- a/block/blk-throttle.c
> +++ b/block/blk-throttle.c
> @@ -1903,7 +1903,7 @@ static void throtl_downgrade_check(struct throtl_grp *tg)
>
> if (tg->bps[READ][LIMIT_LOW]) {
> bps = tg->last_bytes_disp[READ] * HZ;
> - do_div(bps, elapsed_time);
> + bps = div64_ul(bps, elapsed_time);
Yeah, the divisor is ulong for whatever reason but the thing is in jiffies.
I have a hard time imagining it overflowing 32bit. I'm not sure how useful
this patch is.
--
tejun
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH v2] block: Use div64_ul instead of do_div
2021-11-18 3:40 ` [PATCH v2] " cgel.zte
2021-11-29 18:19 ` Tejun Heo
@ 2021-12-02 16:50 ` Michal Koutný
1 sibling, 0 replies; 4+ messages in thread
From: Michal Koutný @ 2021-12-02 16:50 UTC (permalink / raw)
To: cgel.zte
Cc: tj, axboe, cgroups, linux-block, linux-kernel, zealci, deng.changcheng
[-- Attachment #1: Type: text/plain, Size: 352 bytes --]
Hello.
On Thu, Nov 18, 2021 at 03:40:33AM +0000, cgel.zte@gmail.com wrote:
> Reported-by: Zeal Robot <zealci@zte.com.cn>
> Signed-off-by: Changcheng Deng <deng.changcheng@zte.com.cn>
Just feedback to the bot or to you -- the same do_div() is in the same
function for writes too. I think the processing shouldn't stop at the
first occurence.
Michal
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^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2021-12-02 16:50 UTC | newest]
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2021-11-17 1:03 [PATCH] block: Use div64_ul instead of do_div cgel.zte
2021-11-18 3:40 ` [PATCH v2] " cgel.zte
2021-11-29 18:19 ` Tejun Heo
2021-12-02 16:50 ` Michal Koutný
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