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 <r...@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(+)
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;
--
2.17.1
