2023-03-29 16:46:59

by Chris Hyser

Subject: [PATCH] sched/numa: Fix divide by zero for sysctl_numa_balancing_scan_size.

From: chris hyser <[email protected]>

Commit 6419265899d9 ("sched/fair: Fix division by zero
sysctl_numa_balancing_scan_size") prevented a divide by zero by using
sysctl mechanisms to return EINVAL for a sysctl_numa_balancing_scan_size
value of zero. When moved from a sysctl to a debugfs file, this checking
was lost.

This patch puts zero checking back in place.

Signed-off-by: Chris Hyser <[email protected]>
---
kernel/sched/debug.c | 50 +++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 49 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index 1637b65ba07a..dfd0fe6123ec 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -278,6 +278,54 @@ static const struct file_operations sched_dynamic_fops = {

#endif /* CONFIG_PREEMPT_DYNAMIC */

+#ifdef CONFIG_NUMA_BALANCING
+
+static ssize_t sched_numa_scan_write(struct file *filp, const char __user *ubuf,
+ size_t cnt, loff_t *ppos)
+{
+ char buf[16];
+ unsigned int scan_size;
+
+ if (cnt > 15)
+ cnt = 15;
+
+ if (copy_from_user(&buf, ubuf, cnt))
+ return -EFAULT;
+ buf[cnt] = '\0';
+
+ if (kstrtouint(buf, 10, &scan_size))
+ return -EINVAL;
+
+ if (!scan_size)
+ return -EINVAL;
+
+ sysctl_numa_balancing_scan_size = scan_size;
+
+ *ppos += cnt;
+ return cnt;
+}
+
+static int sched_numa_scan_show(struct seq_file *m, void *v)
+{
+ seq_printf(m, "%d\n", sysctl_numa_balancing_scan_size);
+ return 0;
+}
+
+static int sched_numa_scan_open(struct inode *inode, struct file *filp)
+{
+ return single_open(filp, sched_numa_scan_show, NULL);
+}
+
+static const struct file_operations sched_numa_scan_fops = {
+ .open = sched_numa_scan_open,
+ .write = sched_numa_scan_write,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = single_release,
+};
+
+#endif /* CONFIG_NUMA_BALANCING */
+
__read_mostly bool sched_debug_verbose;

static const struct seq_operations sched_debug_sops;
@@ -332,7 +380,7 @@ static __init int sched_init_debug(void)
debugfs_create_u32("scan_delay_ms", 0644, numa, &sysctl_numa_balancing_scan_delay);
debugfs_create_u32("scan_period_min_ms", 0644, numa, &sysctl_numa_balancing_scan_period_min);
debugfs_create_u32("scan_period_max_ms", 0644, numa, &sysctl_numa_balancing_scan_period_max);
- debugfs_create_u32("scan_size_mb", 0644, numa, &sysctl_numa_balancing_scan_size);
+ debugfs_create_file("scan_size_mb", 0644, numa, NULL, &sched_numa_scan_fops);
debugfs_create_u32("hot_threshold_ms", 0644, numa, &sysctl_numa_balancing_hot_threshold);
#endif

--
2.31.1

2023-03-29 18:29:51

by Chris Hyser

Subject: Re: [PATCH] sched/numa: Fix divide by zero for sysctl_numa_balancing_scan_size.

On 3/29/23 12:26, Chris Hyser wrote:
> From: chris hyser <[email protected]>

Apologies. Something in my email chain put this in, but I think I
figured it out and sent a version 1.

-chrish

>
> Commit 6419265899d9 ("sched/fair: Fix division by zero
> sysctl_numa_balancing_scan_size") prevented a divide by zero by using
> sysctl mechanisms to return EINVAL for a sysctl_numa_balancing_scan_size
> value of zero. When moved from a sysctl to a debugfs file, this checking
> was lost.
>
> This patch puts zero checking back in place.
>
> Signed-off-by: Chris Hyser <[email protected]>
> ---
> kernel/sched/debug.c | 50 +++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 49 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
> index 1637b65ba07a..dfd0fe6123ec 100644
> --- a/kernel/sched/debug.c
> +++ b/kernel/sched/debug.c
> @@ -278,6 +278,54 @@ static const struct file_operations sched_dynamic_fops = {
>
> #endif /* CONFIG_PREEMPT_DYNAMIC */
>
> +#ifdef CONFIG_NUMA_BALANCING
> +
> +static ssize_t sched_numa_scan_write(struct file *filp, const char __user *ubuf,
> + size_t cnt, loff_t *ppos)
> +{
> + char buf[16];
> + unsigned int scan_size;
> +
> + if (cnt > 15)
> + cnt = 15;
> +
> + if (copy_from_user(&buf, ubuf, cnt))
> + return -EFAULT;
> + buf[cnt] = '\0';
> +
> + if (kstrtouint(buf, 10, &scan_size))
> + return -EINVAL;
> +
> + if (!scan_size)
> + return -EINVAL;
> +
> + sysctl_numa_balancing_scan_size = scan_size;
> +
> + *ppos += cnt;
> + return cnt;
> +}
> +
> +static int sched_numa_scan_show(struct seq_file *m, void *v)
> +{
> + seq_printf(m, "%d\n", sysctl_numa_balancing_scan_size);
> + return 0;
> +}
> +
> +static int sched_numa_scan_open(struct inode *inode, struct file *filp)
> +{
> + return single_open(filp, sched_numa_scan_show, NULL);
> +}
> +
> +static const struct file_operations sched_numa_scan_fops = {
> + .open = sched_numa_scan_open,
> + .write = sched_numa_scan_write,
> + .read = seq_read,
> + .llseek = seq_lseek,
> + .release = single_release,
> +};
> +
> +#endif /* CONFIG_NUMA_BALANCING */
> +
> __read_mostly bool sched_debug_verbose;
>
> static const struct seq_operations sched_debug_sops;
> @@ -332,7 +380,7 @@ static __init int sched_init_debug(void)
> debugfs_create_u32("scan_delay_ms", 0644, numa, &sysctl_numa_balancing_scan_delay);
> debugfs_create_u32("scan_period_min_ms", 0644, numa, &sysctl_numa_balancing_scan_period_min);
> debugfs_create_u32("scan_period_max_ms", 0644, numa, &sysctl_numa_balancing_scan_period_max);
> - debugfs_create_u32("scan_size_mb", 0644, numa, &sysctl_numa_balancing_scan_size);
> + debugfs_create_file("scan_size_mb", 0644, numa, NULL, &sched_numa_scan_fops);
> debugfs_create_u32("hot_threshold_ms", 0644, numa, &sysctl_numa_balancing_hot_threshold);
> #endif
>

2023-03-30 01:57:10

by Chen Yu

Subject: Re: [PATCH] sched/numa: Fix divide by zero for sysctl_numa_balancing_scan_size.

On 2023-03-29 at 12:26:10 -0400, Chris Hyser wrote:
> From: chris hyser <[email protected]>
>
> Commit 6419265899d9 ("sched/fair: Fix division by zero
> sysctl_numa_balancing_scan_size") prevented a divide by zero by using
> sysctl mechanisms to return EINVAL for a sysctl_numa_balancing_scan_size
> value of zero. When moved from a sysctl to a debugfs file, this checking
> was lost.
>
> This patch puts zero checking back in place.
>
> Signed-off-by: Chris Hyser <[email protected]>
> ---
> kernel/sched/debug.c | 50 +++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 49 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
> index 1637b65ba07a..dfd0fe6123ec 100644
> --- a/kernel/sched/debug.c
> +++ b/kernel/sched/debug.c
> @@ -278,6 +278,54 @@ static const struct file_operations sched_dynamic_fops = {
>
> #endif /* CONFIG_PREEMPT_DYNAMIC */
>
> +#ifdef CONFIG_NUMA_BALANCING
> +
> +static ssize_t sched_numa_scan_write(struct file *filp, const char __user *ubuf,
> + size_t cnt, loff_t *ppos)
> +{
> + char buf[16];
> + unsigned int scan_size;
> +
> + if (cnt > 15)
> + cnt = 15;
> +
> + if (copy_from_user(&buf, ubuf, cnt))
> + return -EFAULT;
> + buf[cnt] = '\0';
> +
> + if (kstrtouint(buf, 10, &scan_size))
> + return -EINVAL;
error code of kstrtouint() includes -ERANGE other than -EINVAL, how
about return the error code directly?

thanks,
Chenyu

2023-03-30 13:47:47

by Peter Zijlstra

Subject: Re: [PATCH] sched/numa: Fix divide by zero for sysctl_numa_balancing_scan_size.

On Wed, Mar 29, 2023 at 02:28:25PM -0400, chris hyser wrote:
> On 3/29/23 12:26, Chris Hyser wrote:
> > From: chris hyser <[email protected]>
>
> Apologies. Something in my email chain put this in, but I think I figured it
> out and sent a version 1.

Not actually a problem -- all patch processing tools can deal with this
since it's a common pattern when forwarding patches written by others.

2023-03-30 15:15:26

by Chris Hyser

Subject: Re: [PATCH] sched/numa: Fix divide by zero for sysctl_numa_balancing_scan_size.

On 3/29/23 21:51, Chen Yu wrote:
> On 2023-03-29 at 12:26:10 -0400, Chris Hyser wrote:
>> From: chris hyser <[email protected]>
>>
>> Commit 6419265899d9 ("sched/fair: Fix division by zero
>> sysctl_numa_balancing_scan_size") prevented a divide by zero by using
>> sysctl mechanisms to return EINVAL for a sysctl_numa_balancing_scan_size
>> value of zero. When moved from a sysctl to a debugfs file, this checking
>> was lost.
>>
>> This patch puts zero checking back in place.
>>
>> Signed-off-by: Chris Hyser <[email protected]>
>> ---
>> kernel/sched/debug.c | 50 +++++++++++++++++++++++++++++++++++++++++++-
>> 1 file changed, 49 insertions(+), 1 deletion(-)
>>
>> diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
>> index 1637b65ba07a..dfd0fe6123ec 100644
>> --- a/kernel/sched/debug.c
>> +++ b/kernel/sched/debug.c
>> @@ -278,6 +278,54 @@ static const struct file_operations sched_dynamic_fops = {
>>
>> #endif /* CONFIG_PREEMPT_DYNAMIC */
>>
>> +#ifdef CONFIG_NUMA_BALANCING
>> +
>> +static ssize_t sched_numa_scan_write(struct file *filp, const char __user *ubuf,
>> + size_t cnt, loff_t *ppos)
>> +{
>> + char buf[16];
>> + unsigned int scan_size;
>> +
>> + if (cnt > 15)
>> + cnt = 15;
>> +
>> + if (copy_from_user(&buf, ubuf, cnt))
>> + return -EFAULT;
>> + buf[cnt] = '\0';
>> +
>> + if (kstrtouint(buf, 10, &scan_size))
>> + return -EINVAL;
> error code of kstrtouint() includes -ERANGE other than -EINVAL, how
> about return the error code directly?

Sure. I just sent out a v2.

-chrish

> thanks,
> Chenyu

2023-03-30 16:39:51

by Chris Hyser

Subject: Re: [PATCH] sched/numa: Fix divide by zero for sysctl_numa_balancing_scan_size.

On 3/30/23 09:45, Peter Zijlstra wrote:
> On Wed, Mar 29, 2023 at 02:28:25PM -0400, chris hyser wrote:
>> On 3/29/23 12:26, Chris Hyser wrote:
>>> From: chris hyser <[email protected]>
>>
>> Apologies. Something in my email chain put this in, but I think I figured it
>> out and sent a version 1.
>
> Not actually a problem -- all patch processing tools can deal with this
> since it's a common pattern when forwarding patches written by others.

Makes sense. Thanks.