Re: [PATCH 2/3] alloc_tag: prevent enabling memory profiling if it was shut down

[Suren Baghdasaryan <surenb@google.com>]

On Wed, Sep 10, 2025 at 1:52 PM Usama Arif <usamaarif642@gmail.com> wrote:
>
>
>
> On 10/09/2025 00:34, Suren Baghdasaryan wrote:
> > Memory profiling can be shut down due to reasons like a failure during
> > initialization. When this happens, the user should not be able to
> > re-enable it. Current sysctrl interface does not handle this properly
> > and will allow re-enabling memory profiling. Fix this by checking for
> > this condition during sysctrl write operation.
> >
> > Signed-off-by: Suren Baghdasaryan <surenb@google.com>
> > ---
> >  lib/alloc_tag.c | 12 +++++++++++-
> >  1 file changed, 11 insertions(+), 1 deletion(-)
> >
>
> Acked-by: Usama Arif <usamaarif642@gmail.com>
>
>
>
> > diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
> > index 95688c4cba7a..79891528e7b6 100644
> > --- a/lib/alloc_tag.c
> > +++ b/lib/alloc_tag.c
> > @@ -767,6 +767,16 @@ struct page_ext_operations page_alloc_tagging_ops = {
> >  EXPORT_SYMBOL(page_alloc_tagging_ops);
> >
> >  #ifdef CONFIG_SYSCTL
>
> nit: might be good to add a comment here that we are not using default as we dont want to enable
> it back if it fails once. But not worth a respin as someone can always check git log if curious.

Ok, if I respin the series will add it. Thanks!

>
> > +static int proc_mem_profiling_handler(const struct ctl_table *table, int write,
> > +                                   void *buffer, size_t *lenp, loff_t *ppos)
> > +{
> > +     if (!mem_profiling_support && write)
> > +             return -EINVAL;
> > +
> > +     return proc_do_static_key(table, write, buffer, lenp, ppos);
> > +}
> > +
> > +
> >  static struct ctl_table memory_allocation_profiling_sysctls[] = {
> >       {
> >               .procname       = "mem_profiling",
> > @@ -776,7 +786,7 @@ static struct ctl_table memory_allocation_profiling_sysctls[] = {
> >  #else
> >               .mode           = 0644,
> >  #endif
> > -             .proc_handler   = proc_do_static_key,
> > +             .proc_handler   = proc_mem_profiling_handler,
> >       },
> >  };
> >
>