Re: [PATCH v6 mm-new 02/10] mm: thp: add a new kfunc bpf_mm_get_mem_cgroup()

[Yafang Shao <laoar.shao@gmail.com>]

On Wed, Aug 27, 2025 at 11:34 PM Lorenzo Stoakes
<lorenzo.stoakes@oracle.com> wrote:
>
> +cc cgroup people, please do include them on this stuff.

sure.

>
> BTW I see there is a BPF [STORAGE & CGROUPS] section in MAINTAINERS and
> kernel/bpf/cgroup.c etc. anything useful there for us?

BPF local storage can assist in implementing this feature. However, we
still need to introduce a new helper, bpf_mm_get_mem_cgroup(), to
retrieve the mem_cgroup from an mm_struct.

>
> On Tue, Aug 26, 2025 at 03:19:40PM +0800, Yafang Shao wrote:
> > We will utilize this new kfunc bpf_mm_get_mem_cgroup() to retrieve the
> > associated mem_cgroup from the given @mm. The obtained mem_cgroup must
> > be released by calling bpf_put_mem_cgroup() as a paired operation.
>
> What locking guarantees do we have that this is all fine?

As explained by Shakeel,  no locking is needed for this stuff.

>
> >
> > Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
> > ---
> >  mm/bpf_thp.c | 51 ++++++++++++++++++++++++++++++++++++++++++++++++++-
>
> Also not to be nitty (but I'm going to be anyway :P) but I'm not in love with
> the filename here.
>
> So now we have
>
> - khugepaged.c
> - huge_memory.c
> - bpf_thp.c
>
> Let's maybe call it huge_memory_bpf.c for consistency?

makes sense.

> And obv as mentioned
> before, add it to the MAINTAINERS in the THP section plz.

will do it.


-- 
Regards
Yafang