Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> writes:
> On Tue, Oct 22, 2019 at 9:08 AM Toke Høiland-Jørgensen <toke@xxxxxxxxxx> wrote:
>>
>> From: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
>>
>> When pinning a map, store the pin path in struct bpf_map so it can be
>> re-used later for un-pinning. This simplifies the later addition of per-map
>> pin paths.
>>
>> Signed-off-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
>> ---
>> tools/lib/bpf/libbpf.c | 19 ++++++++++---------
>> 1 file changed, 10 insertions(+), 9 deletions(-)
>>
>> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
>> index cccfd9355134..b4fdd8ee3bbd 100644
>> --- a/tools/lib/bpf/libbpf.c
>> +++ b/tools/lib/bpf/libbpf.c
>> @@ -226,6 +226,7 @@ struct bpf_map {
>> void *priv;
>> bpf_map_clear_priv_t clear_priv;
>> enum libbpf_map_type libbpf_type;
>> + char *pin_path;
>> };
>>
>> struct bpf_secdata {
>> @@ -1929,6 +1930,7 @@ int bpf_map__reuse_fd(struct bpf_map *map, int fd)
>> if (err)
>> goto err_close_new_fd;
>> free(map->name);
>> + zfree(&map->pin_path);
>>
>
> While you are touching this function, can you please also fix error
> handling in it? We should store -errno locally on error, before we
> call close() which might change errno.
Didn't actually look much at the surrounding function, TBH. I do expect
that I will need to go poke into this for the follow-on "automatic reuse
of pinned maps" series anyway. But sure, I can do a bit of cleanup in a
standalone patch first :)
>> map->fd = new_fd;
>> map->name = new_name;
>> @@ -4022,6 +4024,7 @@ int bpf_map__pin(struct bpf_map *map, const char *path)
>> return -errno;
>> }
>>
>> + map->pin_path = strdup(path);
>
> if (!map->pin_path) {
> err = -errno;
> goto err_close_new_fd;
> }
Right.
>> pr_debug("pinned map '%s'\n", path);
>>
>> return 0;
>> @@ -4031,6 +4034,9 @@ int bpf_map__unpin(struct bpf_map *map, const char *path)
>> {
>> int err;
>>
>> + if (!path)
>> + path = map->pin_path;
>
> This semantics is kind of weird. Given we now remember pin_path,
> should we instead check that user-provided path is actually correct
> and matches what we stored? Alternatively, bpf_map__unpin() w/o path
> argument looks like a cleaner API.
Yeah, I guess the function without a path argument would make the most
sense. However, we can't really change the API of bpf_map__unpin()
(unless you're proposing a symbol-versioned new version?). Dunno if it's
worth it to include a new, somewhat oddly-named, function to achieve
this? For the internal libbpf uses at least it's easy enough for the
caller to just go bpf_map__unpin(map, map->pin_path), so I could also
just drop this change? WDYT?
-Toke
