| Message ID | 36151c3c82144ee3f68780e98ccb29a8c6ac3f75.1550185216.git.rdna@fb.com |
|---|---|
| State | Accepted |
| Delegated to: | BPF Maintainers |
| Headers | show |
| Series | libbpf: Add new interfaces | expand |
On 2/14/19 3:01 PM, Andrey Ignatov wrote: > Add bpf_map__resize() to change max_entries for a map. > > Quite often necessary map size is unknown at compile time and can be > calculated only at run time. > > Currently the following approach is used to do so: > * bpf_object__open_buffer() to open Elf file from a buffer; > * bpf_object__find_map_by_name() to find relevant map; > * bpf_map__def() to get map attributes and create struct > bpf_create_map_attr from them; > * update max_entries in bpf_create_map_attr; > * bpf_create_map_xattr() to create new map with updated max_entries; > * bpf_map__reuse_fd() to replace the map in bpf_object with newly > created one. > > And after all this bpf_object can finally be loaded. The map will have > new size. > > It 1) is quite a lot of steps; 2) doesn't take BTF into account. > > For "2)" even more steps should be made and some of them require changes > to libbpf (e.g. to get struct btf * from bpf_object). > > Instead the whole problem can be solved by introducing simple > bpf_map__resize() API that checks the map and sets new max_entries if > the map is not loaded yet. > > So the new steps are: > * bpf_object__open_buffer() to open Elf file from a buffer; > * bpf_object__find_map_by_name() to find relevant map; > * bpf_map__resize() to update max_entries. > > That's much simpler and works with BTF. > > Signed-off-by: Andrey Ignatov <rdna@fb.com> Acked-by: Yonghong Song <yhs@fb.com>
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index e3c39edfb9d3..690e7b079202 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -1114,6 +1114,20 @@ int bpf_map__reuse_fd(struct bpf_map *map, int fd) return -errno; } +int bpf_map__resize(struct bpf_map *map, __u32 max_entries) +{ + if (!map || !max_entries) + return -EINVAL; + + /* If map already created, its attributes can't be changed. */ + if (map->fd >= 0) + return -EBUSY; + + map->def.max_entries = max_entries; + + return 0; +} + static int bpf_object__probe_name(struct bpf_object *obj) { diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h index 69a7c25eaccc..987fd92661d6 100644 --- a/tools/lib/bpf/libbpf.h +++ b/tools/lib/bpf/libbpf.h @@ -294,6 +294,7 @@ LIBBPF_API int bpf_map__set_priv(struct bpf_map *map, void *priv, bpf_map_clear_priv_t clear_priv); LIBBPF_API void *bpf_map__priv(struct bpf_map *map); LIBBPF_API int bpf_map__reuse_fd(struct bpf_map *map, int fd); +LIBBPF_API int bpf_map__resize(struct bpf_map *map, __u32 max_entries); LIBBPF_API bool bpf_map__is_offload_neutral(struct bpf_map *map); LIBBPF_API void bpf_map__set_ifindex(struct bpf_map *map, __u32 ifindex); LIBBPF_API int bpf_map__pin(struct bpf_map *map, const char *path); diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map index 5fc8222209f8..16f342c3d4bc 100644 --- a/tools/lib/bpf/libbpf.map +++ b/tools/lib/bpf/libbpf.map @@ -130,6 +130,7 @@ LIBBPF_0.0.2 { bpf_probe_helper; bpf_probe_map_type; bpf_probe_prog_type; + bpf_map__resize; bpf_map_lookup_elem_flags; bpf_object__find_map_fd_by_name; bpf_get_link_xdp_id;
Add bpf_map__resize() to change max_entries for a map. Quite often necessary map size is unknown at compile time and can be calculated only at run time. Currently the following approach is used to do so: * bpf_object__open_buffer() to open Elf file from a buffer; * bpf_object__find_map_by_name() to find relevant map; * bpf_map__def() to get map attributes and create struct bpf_create_map_attr from them; * update max_entries in bpf_create_map_attr; * bpf_create_map_xattr() to create new map with updated max_entries; * bpf_map__reuse_fd() to replace the map in bpf_object with newly created one. And after all this bpf_object can finally be loaded. The map will have new size. It 1) is quite a lot of steps; 2) doesn't take BTF into account. For "2)" even more steps should be made and some of them require changes to libbpf (e.g. to get struct btf * from bpf_object). Instead the whole problem can be solved by introducing simple bpf_map__resize() API that checks the map and sets new max_entries if the map is not loaded yet. So the new steps are: * bpf_object__open_buffer() to open Elf file from a buffer; * bpf_object__find_map_by_name() to find relevant map; * bpf_map__resize() to update max_entries. That's much simpler and works with BTF. Signed-off-by: Andrey Ignatov <rdna@fb.com> --- tools/lib/bpf/libbpf.c | 14 ++++++++++++++ tools/lib/bpf/libbpf.h | 1 + tools/lib/bpf/libbpf.map | 1 + 3 files changed, 16 insertions(+)