Re: [PATCH v3 32/35] codetag: debug: skip objext checking when it's for objext itself

Vlastimil Babka
2024-02-19T09:17:38Z

On 2/19/24 02:04, Suren Baghdasaryan wrote:
> On Fri, Feb 16, 2024 at 6:39 PM Vlastimil Babka <vbabka@suse.cz> wrote:
>>
>> On 2/12/24 22:39, Suren Baghdasaryan wrote:
>> > objext objects are created with __GFP_NO_OBJ_EXT flag and therefore have
>> > no corresponding objext themselves (otherwise we would get an infinite
>> > recursion). When freeing these objects their codetag will be empty and
>> > when CONFIG_MEM_ALLOC_PROFILING_DEBUG is enabled this will lead to false
>> > warnings. Introduce CODETAG_EMPTY special codetag value to mark
>> > allocations which intentionally lack codetag to avoid these warnings.
>> > Set objext codetags to CODETAG_EMPTY before freeing to indicate that
>> > the codetag is expected to be empty.
>> >
>> > Signed-off-by: Suren Baghdasaryan <surenb@google.com>
>> > ---
>> > include/linux/alloc_tag.h | 26 ++++++++++++++++++++++++++
>> > mm/slab.h | 25 +++++++++++++++++++++++++
>> > mm/slab_common.c | 1 +
>> > mm/slub.c | 8 ++++++++
>> > 4 files changed, 60 insertions(+)
>> >
>> > diff --git a/include/linux/alloc_tag.h b/include/linux/alloc_tag.h
>> > index 0a5973c4ad77..1f3207097b03 100644
>>
>> ...
>>
>> > index c4bd0d5348cb..cf332a839bf4 100644
>> > --- a/mm/slab.h
>> > +++ b/mm/slab.h
>> > @@ -567,6 +567,31 @@ static inline struct slabobj_ext *slab_obj_exts(struct slab *slab)
>> > int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,
>> > gfp_t gfp, bool new_slab);
>> >
>> > +
>> > +#ifdef CONFIG_MEM_ALLOC_PROFILING_DEBUG
>> > +
>> > +static inline void mark_objexts_empty(struct slabobj_ext *obj_exts)
>> > +{
>> > + struct slabobj_ext *slab_exts;
>> > + struct slab *obj_exts_slab;
>> > +
>> > + obj_exts_slab = virt_to_slab(obj_exts);
>> > + slab_exts = slab_obj_exts(obj_exts_slab);
>> > + if (slab_exts) {
>> > + unsigned int offs = obj_to_index(obj_exts_slab->slab_cache,
>> > + obj_exts_slab, obj_exts);
>> > + /* codetag should be NULL */
>> > + WARN_ON(slab_exts[offs].ref.ct);
>> > + set_codetag_empty(&slab_exts[offs].ref);
>> > + }
>> > +}
>> > +
>> > +#else /* CONFIG_MEM_ALLOC_PROFILING_DEBUG */
>> > +
>> > +static inline void mark_objexts_empty(struct slabobj_ext *obj_exts) {}
>> > +
>> > +#endif /* CONFIG_MEM_ALLOC_PROFILING_DEBUG */
>> > +
>>
>> I assume with alloc_slab_obj_exts() moved to slub.c, mark_objexts_empty()
>> could move there too.
>
> No, I think mark_objexts_empty() belongs here. This patch introduced
> the function and uses it. Makes sense to me to keep it all together.

Hi,

here I didn't mean moving between patches, but files. alloc_slab_obj_exts()
in slub.c means all callers of mark_objexts_empty() are in slub.c so it
doesn't need to be in slab.h

Also same thing with mark_failed_objexts_alloc() and
handle_failed_objexts_alloc() in patch 34/35.