Re: [PATCH v6 03/13] mm/demotion: Return error on write to numa_demotion sysfs

[Aneesh Kumar K V]

On 6/13/22 8:56 AM, Ying Huang wrote:
> On Fri, 2022-06-10 at 19:22 +0530, Aneesh Kumar K.V wrote:
> > With CONFIG_MIGRATION disabled return EINVAL on write.
> >
> > Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
> > ---
> >   mm/memory-tiers.c | 3 +++
> >   1 file changed, 3 insertions(+)
> >
> > diff --git a/mm/memory-tiers.c b/mm/memory-tiers.c
> > index 9c6b40d7e0bf..c3123a457d90 100644
> > --- a/mm/memory-tiers.c
> > +++ b/mm/memory-tiers.c
> > @@ -105,6 +105,9 @@ static ssize_t numa_demotion_enabled_store(struct kobject *kobj,
> >   {
> >   	ssize_t ret;
> >   
> >
> > +	if (!IS_ENABLED(CONFIG_MIGRATION))
> > +		return -EINVAL;
> > +
>
> How about enclose numa_demotion_enabled_xxx related code with CONFIG_MIGRATION?

IIUC there is a desire to use IS_ENABLED() in the kernel instead of 
#ifdef since that helps in more compile time checks. Because there are 
no dead codes during compile now with IS_ENABLED().

W.r.t leaving the sysfs file visible even when CONFIG_MIGRATION is 
disabled, I was thinking it gives better visibility into numa_demotion 
status. I could switch to hide numa_demotion file if that is desirable.

> >   	ret = kstrtobool(buf, &numa_demotion_enabled);
> >   	if (ret)
> >   		return ret;

-aneesh