On 2023/12/22 22:45, Jiri Olsa wrote:
On Fri, Dec 22, 2023 at 08:21:45PM +0800, Philo Lu wrote:
map_update_elem is used to create relay files and bind them with the
relay channel, which is created with BPF_MAP_CREATE. This allows users
to set a custom directory name. It must be used with key=NULL and
flag=0.
Here is an example:
```
struct {
__uint(type, BPF_MAP_TYPE_RELAY);
__uint(max_entries, 4096);
} my_relay SEC(".maps");
...
char dir_name[] = "relay_test";
bpf_map_update_elem(map_fd, NULL, dir_name, 0);
```
Then, directory `/sys/kerenl/debug/relay_test` will be created, which
includes files of my_relay0...my_relay[#cpu]. Each represents a per-cpu
buffer with size 8 * 4096 B (there are 8 subbufs by default, each with
size 4096B).
Signed-off-by: Philo Lu <lulie@xxxxxxxxxxxxxxxxx>
---
kernel/bpf/relaymap.c | 32 +++++++++++++++++++++++++++++++-
1 file changed, 31 insertions(+), 1 deletion(-)
diff --git a/kernel/bpf/relaymap.c b/kernel/bpf/relaymap.c
index d0adc7f67758..588c8de0a4bd 100644
--- a/kernel/bpf/relaymap.c
+++ b/kernel/bpf/relaymap.c
@@ -117,7 +117,37 @@ static void *relay_map_lookup_elem(struct bpf_map *map, void *key)
static long relay_map_update_elem(struct bpf_map *map, void *key, void *value,
u64 flags)
{
- return -EOPNOTSUPP;
+ struct bpf_relay_map *rmap;
+ struct dentry *parent;
+ int err;
+
+ if (unlikely(flags))
+ return -EINVAL;
+
+ if (unlikely(key))
+ return -EINVAL;
+
+ rmap = container_of(map, struct bpf_relay_map, map);
+
+ /* The directory already exists */
+ if (rmap->relay_chan->has_base_filename)
+ return -EEXIST;
+
+ /* Setup relay files. Note that the directory name passed as value should
+ * not be longer than map->value_size, including the '\0' at the end.
+ */
+ ((char *)value)[map->value_size - 1] = '\0';
+ parent = debugfs_create_dir(value, NULL);
+ if (IS_ERR_OR_NULL(parent))
+ return PTR_ERR(parent);
+
+ err = relay_late_setup_files(rmap->relay_chan, map->name, parent);
+ if (err) {
+ debugfs_remove_recursive(parent);
+ return err;
+ }
looks like this patch could be moved to the previous one?
OK, will do it.
jirka
+
+ return 0;
}
static long relay_map_delete_elem(struct bpf_map *map, void *key)
--
2.32.0.3.g01195cf9f
