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Date: Thu, 31 Oct 2019 10:22:20 -0700
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Toke Høiland-Jørgensen <toke@...hat.com>
Cc: Daniel Borkmann <daniel@...earbox.net>,
Alexei Starovoitov <ast@...nel.org>,
Martin KaFai Lau <kafai@...com>,
Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
Jesper Dangaard Brouer <brouer@...hat.com>,
David Miller <davem@...emloft.net>,
Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH bpf-next v4 2/5] libbpf: Store map pin path and status in
struct bpf_map
On Tue, Oct 29, 2019 at 12:39 PM Toke Høiland-Jørgensen <toke@...hat.com> wrote:
>
> From: Toke Høiland-Jørgensen <toke@...hat.com>
>
> Support storing and setting a pin path in struct bpf_map, which can be used
> for automatic pinning. Also store the pin status so we can avoid attempts
> to re-pin a map that has already been pinned (or reused from a previous
> pinning).
>
> The behaviour of bpf_object__{un,}pin_maps() is changed so that if it is
> called with a NULL path argument (which was previously illegal), it will
> (un)pin only those maps that have a pin_path set.
>
> Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>
> ---
Looks good, thanks! Just some minor things to fix up below.
Acked-by: Andrii Nakryiko <andriin@...com>
> tools/lib/bpf/libbpf.c | 164 +++++++++++++++++++++++++++++++++++-----------
> tools/lib/bpf/libbpf.h | 8 ++
> tools/lib/bpf/libbpf.map | 3 +
> 3 files changed, 134 insertions(+), 41 deletions(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index ce5ef3ddd263..fd11f6aeb32c 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -226,6 +226,8 @@ struct bpf_map {
> void *priv;
> bpf_map_clear_priv_t clear_priv;
> enum libbpf_map_type libbpf_type;
> + char *pin_path;
> + bool pinned;
> };
>
> struct bpf_secdata {
> @@ -4025,47 +4027,119 @@ int bpf_map__pin(struct bpf_map *map, const char *path)
> char *cp, errmsg[STRERR_BUFSIZE];
> int err;
>
> - err = check_path(path);
> - if (err)
> - return err;
> -
> if (map == NULL) {
> pr_warn("invalid map pointer\n");
> return -EINVAL;
> }
>
> - if (bpf_obj_pin(map->fd, path)) {
> - cp = libbpf_strerror_r(errno, errmsg, sizeof(errmsg));
> - pr_warn("failed to pin map: %s\n", cp);
> - return -errno;
> + if (map->pin_path) {
> + if (path && strcmp(path, map->pin_path)) {
> + pr_warn("map '%s' already has pin path '%s' different from '%s'\n",
> + bpf_map__name(map), map->pin_path, path);
> + return -EINVAL;
> + } else if (map->pinned) {
> + pr_debug("map '%s' already pinned at '%s'; not re-pinning\n",
> + bpf_map__name(map), map->pin_path);
> + return 0;
> + }
`if (map->pinned)` check is the same in both branches, so I'd do it
first, before this map->pin_path if/else.
> + } else {
> + if (!path) {
> + pr_warn("missing a path to pin map '%s' at\n",
> + bpf_map__name(map));
> + return -EINVAL;
> + } else if (map->pinned) {
> + pr_warn("map '%s' already pinned\n", bpf_map__name(map));
> + return -EEXIST;
> + }
> +
> + map->pin_path = strdup(path);
> + if (!map->pin_path) {
> + err = -errno;
> + goto out_err;
> + }
> }
>
[...]
> +
> + err = check_path(path);
> + if (err)
> + return err;
> +
> err = unlink(path);
> if (err != 0)
> return -errno;
> - pr_debug("unpinned map '%s'\n", path);
> +
> + map->pinned = false;
> + pr_debug("unpinned map from '%s' from '%s'\n", bpf_map__name(map), path);
typo: extra from before map name?
>
> return 0;
> }
>
[...]
>
> return err;
> @@ -4131,17 +4205,24 @@ int bpf_object__unpin_maps(struct bpf_object *obj, const char *path)
> return -ENOENT;
>
> bpf_object__for_each_map(map, obj) {
> + char *pin_path = NULL;
> char buf[PATH_MAX];
you can call buf as pin_path and get rid of extra pointer?
> - int len;
>
> - len = snprintf(buf, PATH_MAX, "%s/%s", path,
> - bpf_map__name(map));
> - if (len < 0)
> - return -EINVAL;
> - else if (len >= PATH_MAX)
> - return -ENAMETOOLONG;
> + if (path) {
> + int len;
> +
> + len = snprintf(buf, PATH_MAX, "%s/%s", path,
> + bpf_map__name(map));
> + if (len < 0)
> + return -EINVAL;
> + else if (len >= PATH_MAX)
> + return -ENAMETOOLONG;
> + pin_path = buf;
> + } else if (!map->pin_path) {
> + continue;
> + }
>
> - err = bpf_map__unpin(map, buf);
> + err = bpf_map__unpin(map, pin_path);
> if (err)
> return err;
> }
[...]
> diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> index d1473ea4d7a5..c24d4c01591d 100644
> --- a/tools/lib/bpf/libbpf.map
> +++ b/tools/lib/bpf/libbpf.map
> @@ -197,4 +197,7 @@ LIBBPF_0.0.6 {
> bpf_object__open_mem;
> bpf_program__get_expected_attach_type;
> bpf_program__get_type;
> + bpf_map__get_pin_path;
> + bpf_map__set_pin_path;
> + bpf_map__is_pinned;
we try to keep this list alphabetically sorted
> } LIBBPF_0.0.5;
>
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