linux-kernel - Re: [PATCH 2/2] perf tools: Remove bpf_map__set_priv/bpf_map_

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Date:   Tue, 1 Mar 2022 09:49:30 +0100
From:   Jiri Olsa <olsajiri@...il.com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     Jiri Olsa <jolsa@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Andrii Nakryiko <andrii@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Ingo Molnar <mingo@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Ian Rogers <irogers@...gle.com>,
        "linux-perf-use." <linux-perf-users@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH 2/2] perf tools: Remove bpf_map__set_priv/bpf_map__priv
 usage

On Mon, Feb 28, 2022 at 05:49:32PM -0800, Andrii Nakryiko wrote:
> On Thu, Feb 24, 2022 at 7:53 AM Jiri Olsa <jolsa@...nel.org> wrote:
> >
> > Both bpf_map__set_priv/bpf_map__priv are deprecated
> > and will be eventually removed.
> >
> > Using hashmap to replace that functionality.
> >
> > Suggested-by: Andrii Nakryiko <andrii@...nel.org>
> > Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> > ---
> >  tools/perf/util/bpf-loader.c | 66 ++++++++++++++++++++++++++++++++----
> >  1 file changed, 59 insertions(+), 7 deletions(-)
> >
> > diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
> > index b9d4278895ec..4f6173756a9d 100644
> > --- a/tools/perf/util/bpf-loader.c
> > +++ b/tools/perf/util/bpf-loader.c
> > @@ -27,6 +27,7 @@
> >  #include "llvm-utils.h"
> >  #include "c++/clang-c.h"
> >  #include "hashmap.h"
> > +#include "asm/bug.h"
> >
> >  #include <internal/xyarray.h>
> >
> > @@ -57,6 +58,7 @@ struct bpf_perf_object {
> >
> >  static LIST_HEAD(bpf_objects_list);
> >  static struct hashmap *bpf_program_hash;
> > +static struct hashmap *bpf_map_hash;
> >
> >  static struct bpf_perf_object *
> >  bpf_perf_object__next(struct bpf_perf_object *prev)
> > @@ -204,6 +206,8 @@ static void bpf_program_hash_free(void)
> >         bpf_program_hash = NULL;
> >  }
> >
> > +static void bpf_map_hash_free(void);
> > +
> >  void bpf__clear(void)
> >  {
> >         struct bpf_perf_object *perf_obj, *tmp;
> > @@ -214,6 +218,7 @@ void bpf__clear(void)
> >         }
> >
> >         bpf_program_hash_free();
> > +       bpf_map_hash_free();
> >  }
> >
> >  static size_t ptr_hash(const void *__key, void *ctx __maybe_unused)
> > @@ -976,7 +981,7 @@ bpf_map_priv__purge(struct bpf_map_priv *priv)
> >  }
> >
> >  static void
> > -bpf_map_priv__clear(struct bpf_map *map __maybe_unused,
> > +bpf_map_priv__clear(const struct bpf_map *map __maybe_unused,
> >                     void *_priv)
> >  {
> >         struct bpf_map_priv *priv = _priv;
> > @@ -985,6 +990,53 @@ bpf_map_priv__clear(struct bpf_map *map __maybe_unused,
> >         free(priv);
> >  }
> >
> > +static void *map_priv(const struct bpf_map *map)
> > +{
> > +       void *priv;
> > +
> > +       if (IS_ERR_OR_NULL(bpf_map_hash))
> > +               return NULL;
> > +       if (!hashmap__find(bpf_map_hash, map, &priv))
> > +               return NULL;
> > +       return priv;
> > +}
> > +
> > +static void bpf_map_hash_free(void)
> > +{
> > +       struct hashmap_entry *cur;
> > +       size_t bkt;
> > +
> > +       if (IS_ERR_OR_NULL(bpf_map_hash))
> > +               return;
> > +
> > +       hashmap__for_each_entry(bpf_map_hash, cur, bkt)
> > +               bpf_map_priv__clear(cur->key, cur->value);
> > +
> > +       hashmap__free(bpf_map_hash);
> > +       bpf_map_hash = NULL;
> > +}
> > +
> > +static int map_set_priv(struct bpf_map *map, void *priv)
> > +{
> > +       void *old_priv;
> > +
> > +       if (WARN_ON_ONCE(IS_ERR(bpf_map_hash)))
> > +               return PTR_ERR(bpf_program_hash);
> > +
> 
> you didn't warn for this in the previous patch. I have no preference,
> just pointing out assymetry.

there's already message from the caller when program_set_priv fails,
so I don't think we need another one

jirka

> 
> > +       if (!bpf_map_hash) {
> > +               bpf_map_hash = hashmap__new(ptr_hash, ptr_equal, NULL);
> > +               if (IS_ERR(bpf_map_hash))
> > +                       return PTR_ERR(bpf_map_hash);
> > +       }
> > +
> > +       old_priv = map_priv(map);
> > +       if (old_priv) {
> > +               bpf_map_priv__clear(map, old_priv);
> > +               return hashmap__set(bpf_map_hash, map, priv, NULL, NULL);
> > +       }
> > +       return hashmap__add(bpf_map_hash, map, priv);
> > +}
> > +
> 
> [...]