Re: [PATCH v2 1/2] mm: huge_memory: disallow hugepages if the system-wide THP sysfs settings are disabled

[Baolin Wang]

On 2025/6/7 02:47, Dev Jain wrote:
> On 06/06/25 10:19 pm, Dev Jain wrote:
> > On 05/06/25 1:30 pm, Baolin Wang wrote:
> > > The MADV_COLLAPSE will ignore the system-wide Anon THP sysfs 
> > > settings, which
> > > means that even though we have disabled the Anon THP configuration, 
> > > MADV_COLLAPSE
> > > will still attempt to collapse into a Anon THP. This violates the 
> > > rule we have
> > > agreed upon: never means never.
> > >
> > > Another rule for madvise, referring to David's suggestion: “allowing 
> > > for collapsing
> > > in a VM without VM_HUGEPAGE in the "madvise" mode would be fine".
> > >
> > > To address this issue, should check whether the Anon THP 
> > > configuration is disabled
> > > in thp_vma_allowable_orders(), even when the TVA_ENFORCE_SYSFS flag 
> > > is set.
> >
> > Did you mean to say "even when the TVA_ENFORCE_SYSFS flag is *not* 
> > set"? Because if
> > is set, then we have to check the anon THP sysfs config.

Sorry for the confusion. What I mean is that we should also check 
whether the Anon THP is disabled when the TVA_ENFORCE_SYSFS flag is set. 
Will update the commit message.

> Otherwise the patch itself looks good to me, so:
>
> Reviewed-by: Dev Jain <dev.jain@xxxxxxx>

Thanks for reviewing.