linux-kernel - Re: [PATCH v2 1/1] alloc_tag: mark pages reserved during CMA activation as not tagged

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Message-ID: <CAJuCfpExN+esSMgOSmSXivDEeiwSqkeOAr6_Pw-yL+-8ajtGYQ@mail.gmail.com>
Date: Tue, 13 Aug 2024 07:27:44 -0700
From: Suren Baghdasaryan <surenb@...gle.com>
To: David Hildenbrand <david@...hat.com>
Cc: akpm@...ux-foundation.org, kent.overstreet@...ux.dev, vbabka@...e.cz, 
	pasha.tatashin@...een.com, souravpanda@...gle.com, keescook@...omium.org, 
	linux-kernel@...r.kernel.org, linux-mm@...ck.org, stable@...r.kernel.org
Subject: Re: [PATCH v2 1/1] alloc_tag: mark pages reserved during CMA
 activation as not tagged

On Tue, Aug 13, 2024 at 2:25 AM David Hildenbrand <david@...hat.com> wrote:
>
> On 12.08.24 21:24, Suren Baghdasaryan wrote:
> > During CMA activation, pages in CMA area are prepared and then freed
> > without being allocated. This triggers warnings when memory allocation
> > debug config (CONFIG_MEM_ALLOC_PROFILING_DEBUG) is enabled. Fix this
> > by marking these pages not tagged before freeing them.
> >
> > Fixes: d224eb0287fb ("codetag: debug: mark codetags for reserved pages as empty")
> > Signed-off-by: Suren Baghdasaryan <surenb@...gle.com>
> > Cc: stable@...r.kernel.org # v6.10
> > ---
> > changes since v1 [1]
> > - Added Fixes tag
> > - CC'ed stable
> >
> > [1] https://lore.kernel.org/all/20240812184455.86580-1-surenb@google.com/
> >
> >   mm/mm_init.c | 10 ++++++++++
> >   1 file changed, 10 insertions(+)
> >
> > diff --git a/mm/mm_init.c b/mm/mm_init.c
> > index 75c3bd42799b..ec9324653ad9 100644
> > --- a/mm/mm_init.c
> > +++ b/mm/mm_init.c
> > @@ -2245,6 +2245,16 @@ void __init init_cma_reserved_pageblock(struct page *page)
> >
> >       set_pageblock_migratetype(page, MIGRATE_CMA);
> >       set_page_refcounted(page);
> > +
> > +     /* pages were reserved and not allocated */
> > +     if (mem_alloc_profiling_enabled()) {
> > +             union codetag_ref *ref = get_page_tag_ref(page);
> > +
> > +             if (ref) {
> > +                     set_codetag_empty(ref);
> > +                     put_page_tag_ref(ref);
> > +             }
> > +     }
>
> Should we have a helper like clear_page_tag_ref() that wraps this?

With this one we have 3 instances of this sequence, so it makes sense
to have a helper. I'm going to send a v3 with 2 patches - one
introducing clear_page_tag_ref() and the next one adding this
instance.
Thanks for the suggestion, David!

>
> --
> Cheers,
>
> David / dhildenb
>