On Tue, Oct 22, 2019 at 9:08 AM Toke Høiland-Jørgensen <toke@xxxxxxxxxx> wrote:
>
> From: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
>
> While the current map pinning functions will check whether the pin path is
> contained on a BPF filesystem, it does not offer any options to mount the
> file system if it doesn't exist. Since we now have pinning options, add a
> new one to automount a BPF filesystem at the pinning path if that is not
Next thing we'll be adding extra options to mount BPF FS... Can we
leave the task of auto-mounting BPF FS to tools/applications?
> already pointing at a bpffs.
>
> The mounting logic itself is copied from the iproute2 BPF helper functions.
>
> Signed-off-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
> ---
> tools/lib/bpf/libbpf.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++
> tools/lib/bpf/libbpf.h | 5 ++++-
> 2 files changed, 51 insertions(+), 1 deletion(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index aea3916de341..f527224bb211 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -37,6 +37,7 @@
> #include <sys/epoll.h>
> #include <sys/ioctl.h>
> #include <sys/mman.h>
> +#include <sys/mount.h>
> #include <sys/stat.h>
> #include <sys/types.h>
> #include <sys/vfs.h>
> @@ -4072,6 +4073,35 @@ int bpf_map__unpin(struct bpf_map *map, const char *path)
> return 0;
> }
>
> +static int mount_bpf_fs(const char *target)
> +{
> + bool bind_done = false;
> +
> + while (mount("", target, "none", MS_PRIVATE | MS_REC, NULL)) {
what does this loop do? we need some comments explaining what's going
on here (or better yet just drop this entirely and let
bpftool/iproute2 do the mounting).
> + if (errno != EINVAL || bind_done) {
> + pr_warning("mount --make-private %s failed: %s\n",
> + target, strerror(errno));
> + return -1;
> + }
> +
> + if (mount(target, target, "none", MS_BIND, NULL)) {
> + pr_warning("mount --bind %s %s failed: %s\n",
> + target, target, strerror(errno));
> + return -1;
> + }
> +
> + bind_done = true;
> + }
> +
> + if (mount("bpf", target, "bpf", 0, "mode=0700")) {
> + fprintf(stderr, "mount -t bpf bpf %s failed: %s\n",
> + target, strerror(errno));
> + return -1;
> + }
> +
> + return 0;
> +}
> +
> static int get_pin_path(char *buf, size_t buf_len,
> struct bpf_map *map, struct bpf_object_pin_opts *opts,
> bool mkdir)
> @@ -4102,6 +4132,23 @@ static int get_pin_path(char *buf, size_t buf_len,
Nothing in `get_pin_path` indicates that it's going to do an entire FS
mount, please split this out of get_pin_path.
> err = make_dir(path);
> if (err)
> return err;
> +
> + if (OPTS_GET(opts, mount_bpf_fs, false)) {
> + struct statfs st_fs;
> + char *cp;
> +
> + if (statfs(path, &st_fs)) {
> + char errmsg[STRERR_BUFSIZE];
> +
> + cp = libbpf_strerror_r(errno, errmsg, sizeof(errmsg));
> + pr_warning("failed to statfs %s: %s\n", path, cp);
> + return -errno;
> + }
> + if (st_fs.f_type != BPF_FS_MAGIC &&
> + mount_bpf_fs(path)) {
> + return -EINVAL;
> + }
> + }
> }
>
> len = snprintf(buf, buf_len, "%s/%s", path, bpf_map__name(map));
> diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> index 2131eeafb18d..76b9a6cc7063 100644
> --- a/tools/lib/bpf/libbpf.h
> +++ b/tools/lib/bpf/libbpf.h
> @@ -143,8 +143,11 @@ struct bpf_object_pin_opts {
> * and this type used for all maps instead.
> */
> enum libbpf_pin_type override_type;
> +
> + /* Whether to attempt to mount a BPF FS if it's not already mounted */
> + bool mount_bpf_fs;
> };
> -#define bpf_object_pin_opts__last_field override_type
> +#define bpf_object_pin_opts__last_field mount_bpf_fs
>
> LIBBPF_API int bpf_object__pin_maps(struct bpf_object *obj, const char *path);
> LIBBPF_API int bpf_object__unpin_maps(struct bpf_object *obj,
>
