Re: [PATCH bpf-next v1 2/5] cgroup: bpf: add cgroup_rstat_updated() and cgroup_rstat_flush() kfuncs

[Yonghong Song]

On 5/20/22 9:08 AM, Yosry Ahmed wrote:
> On Fri, May 20, 2022 at 8:15 AM Yonghong Song <yhs@xxxxxx> wrote:
> > On 5/19/22 6:21 PM, Yosry Ahmed wrote:
> > > Add cgroup_rstat_updated() and cgroup_rstat_flush() kfuncs to bpf
> > > tracing programs. bpf programs that make use of rstat can use these
> > > functions to inform rstat when they update stats for a cgroup, and when
> > > they need to flush the stats.
> > >
> > > Signed-off-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
> > > ---
> > >    kernel/cgroup/rstat.c | 35 ++++++++++++++++++++++++++++++++++-
> > >    1 file changed, 34 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c
> > > index e7a88d2600bd..a16a851bc0a1 100644
> > > --- a/kernel/cgroup/rstat.c
> > > +++ b/kernel/cgroup/rstat.c
> > > @@ -3,6 +3,11 @@
> > >
> > >    #include <linux/sched/cputime.h>
> > >
> > > +#include <linux/bpf.h>
> > > +#include <linux/btf.h>
> > > +#include <linux/btf_ids.h>
> > > +
> > > +
> > >    static DEFINE_SPINLOCK(cgroup_rstat_lock);
> > >    static DEFINE_PER_CPU(raw_spinlock_t, cgroup_rstat_cpu_lock);
> > >
> > > @@ -141,7 +146,12 @@ static struct cgroup *cgroup_rstat_cpu_pop_updated(struct cgroup *pos,
> > >        return pos;
> > >    }
> > >
> > > -/* A hook for bpf stat collectors to attach to and flush their stats */
> > > +/*
> > > + * A hook for bpf stat collectors to attach to and flush their stats.
> > > + * Together with providing bpf kfuncs for cgroup_rstat_updated() and
> > > + * cgroup_rstat_flush(), this enables a complete workflow where bpf progs that
> > > + * collect cgroup stats can integrate with rstat for efficient flushing.
> > > + */
> > >    __weak noinline void bpf_rstat_flush(struct cgroup *cgrp,
> > >                                     struct cgroup *parent, int cpu)
> > >    {
> > > @@ -476,3 +486,26 @@ void cgroup_base_stat_cputime_show(struct seq_file *seq)
> > >                   "system_usec %llu\n",
> > >                   usage, utime, stime);
> > >    }
> > > +
> > > +/* Add bpf kfuncs for cgroup_rstat_updated() and cgroup_rstat_flush() */
> > > +BTF_SET_START(bpf_rstat_check_kfunc_ids)
> > > +BTF_ID(func, cgroup_rstat_updated)
> > > +BTF_ID(func, cgroup_rstat_flush)
> > > +BTF_SET_END(bpf_rstat_check_kfunc_ids)
> > > +
> > > +BTF_SET_START(bpf_rstat_sleepable_kfunc_ids)
> > > +BTF_ID(func, cgroup_rstat_flush)
> > > +BTF_SET_END(bpf_rstat_sleepable_kfunc_ids)
> > > +
> > > +static const struct btf_kfunc_id_set bpf_rstat_kfunc_set = {
> > > +     .owner          = THIS_MODULE,
> > > +     .check_set      = &bpf_rstat_check_kfunc_ids,
> > > +     .sleepable_set  = &bpf_rstat_sleepable_kfunc_ids,
> >
> > There is a compilation error here:
> >
> > kernel/cgroup/rstat.c:503:3: error: ‘const struct btf_kfunc_id_set’ has
> > no member named ‘sleepable_set’; did you mean ‘release_set’?
> >       503 |  .sleepable_set = &bpf_rstat_sleepable_kfunc_ids,
> >           |   ^~~~~~~~~~~~~
> >           |   release_set
> >     kernel/cgroup/rstat.c:503:19: warning: excess elements in struct
> > initializer
> >       503 |  .sleepable_set = &bpf_rstat_sleepable_kfunc_ids,
> >           |                   ^
> >     kernel/cgroup/rstat.c:503:19: note: (near initialization for
> > ‘bpf_rstat_kfunc_set’)
> >     make[3]: *** [scripts/Makefile.build:288: kernel/cgroup/rstat.o] Error 1
> >
> > Please fix.
>
> This patch series is rebased on top of 2 patches in the mailing list:
> - bpf/btf: also allow kfunc in tracing and syscall programs
> - btf: Add a new kfunc set which allows to mark a function to be
>    sleepable
>
> I specified this in the cover letter, do I need to do something else
> in this situation? Re-send the patches as part of my series?

At least put a link in the cover letter for the above two patches?
This way, people can easily find them to double check.

> > > +};
> > > +
> > > +static int __init bpf_rstat_kfunc_init(void)
> > > +{
> > > +     return register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING,
> > > +                                      &bpf_rstat_kfunc_set);
> > > +}
> > > +late_initcall(bpf_rstat_kfunc_init);