Re: [PATCH bpf-next 2/9] samples: bpf: refactor hbm program with libbpf

On Tue, Nov 17, 2020 at 02:56:37PM +0000, Daniel T. Lee wrote:
[ ... ]

> diff --git a/samples/bpf/hbm.c b/samples/bpf/hbm.c
> index b9f9f771dd81..008bc635ad9b 100644
> --- a/samples/bpf/hbm.c
> +++ b/samples/bpf/hbm.c
> @@ -46,7 +46,6 @@
>  #include <bpf/bpf.h>
>  #include <getopt.h>
>  
> -#include "bpf_load.h"
>  #include "bpf_rlimit.h"
>  #include "trace_helpers.h"
>  #include "cgroup_helpers.h"
> @@ -68,9 +67,10 @@ bool edt_flag;
>  static void Usage(void);
>  static void do_error(char *msg, bool errno_flag);
>  
> +struct bpf_program *bpf_prog;
>  struct bpf_object *obj;
> -int bpfprog_fd;
>  int cgroup_storage_fd;
> +int queue_stats_fd;
>  
>  static void do_error(char *msg, bool errno_flag)
>  {
> @@ -83,56 +83,54 @@ static void do_error(char *msg, bool errno_flag)
>  
>  static int prog_load(char *prog)
>  {
> -	struct bpf_prog_load_attr prog_load_attr = {
> -		.prog_type = BPF_PROG_TYPE_CGROUP_SKB,
> -		.file = prog,
> -		.expected_attach_type = BPF_CGROUP_INET_EGRESS,
> -	};
> -	int map_fd;
> -	struct bpf_map *map;
> +	int rc = 1;
>  
> -	int ret = 0;
> +	obj = bpf_object__open_file(prog, NULL);
> +	if (libbpf_get_error(obj)) {
> +		printf("ERROR: opening BPF object file failed\n");
> +		return rc;
> +	}
>  
> -	if (access(prog, O_RDONLY) < 0) {
> -		printf("Error accessing file %s: %s\n", prog, strerror(errno));
> -		return 1;
> +	/* load BPF program */
> +	if (bpf_object__load(obj)) {
> +		printf("ERROR: loading BPF object file failed\n");
> +		goto cleanup;
>  	}
> -	if (bpf_prog_load_xattr(&prog_load_attr, &obj, &bpfprog_fd))
> -		ret = 1;
> -	if (!ret) {
> -		map = bpf_object__find_map_by_name(obj, "queue_stats");
> -		map_fd = bpf_map__fd(map);
> -		if (map_fd < 0) {
> -			printf("Map not found: %s\n", strerror(map_fd));
> -			ret = 1;
> -		}
> +
> +	bpf_prog = bpf_object__find_program_by_title(obj, "cgroup_skb/egress");
> +	if (!bpf_prog) {
> +		printf("ERROR: finding a prog in obj file failed\n");
> +		goto cleanup;
>  	}
>  
> -	if (ret) {
> -		printf("ERROR: bpf_prog_load_xattr failed for: %s\n", prog);
> -		printf("  Output from verifier:\n%s\n------\n", bpf_log_buf);
> -		ret = -1;
> -	} else {
> -		ret = map_fd;
> +	queue_stats_fd = bpf_object__find_map_fd_by_name(obj, "queue_stats");
> +	if (queue_stats_fd < 0) {
> +		printf("ERROR: finding a map in obj file failed\n");
> +		goto cleanup;
>  	}
>  
> -	return ret;
> +	rc = 0;
Just return 0.

> +
> +cleanup:
> +	if (rc != 0)
so this test can be avoided.

> +		bpf_object__close(obj);
> +
> +	return rc;
>  }
>  
>  static int run_bpf_prog(char *prog, int cg_id)
>  {
> -	int map_fd;
> -	int rc = 0;
> +	struct hbm_queue_stats qstats = {0};
> +	struct bpf_link *link = NULL;
> +	char cg_dir[100];
>  	int key = 0;
>  	int cg1 = 0;
> -	int type = BPF_CGROUP_INET_EGRESS;
> -	char cg_dir[100];
> -	struct hbm_queue_stats qstats = {0};
> +	int rc = 0;
>  
>  	sprintf(cg_dir, "/hbm%d", cg_id);
> -	map_fd = prog_load(prog);
> -	if (map_fd  == -1)
> -		return 1;
> +	rc = prog_load(prog);
> +	if (rc != 0)
> +		return rc;
>  
>  	if (setup_cgroup_environment()) {
>  		printf("ERROR: setting cgroup environment\n");
> @@ -152,16 +150,18 @@ static int run_bpf_prog(char *prog, int cg_id)
>  	qstats.stats = stats_flag ? 1 : 0;
>  	qstats.loopback = loopback_flag ? 1 : 0;
>  	qstats.no_cn = no_cn_flag ? 1 : 0;
> -	if (bpf_map_update_elem(map_fd, &key, &qstats, BPF_ANY)) {
> +	if (bpf_map_update_elem(queue_stats_fd, &key, &qstats, BPF_ANY)) {
>  		printf("ERROR: Could not update map element\n");
>  		goto err;
>  	}
>  
>  	if (!outFlag)
> -		type = BPF_CGROUP_INET_INGRESS;
> -	if (bpf_prog_attach(bpfprog_fd, cg1, type, 0)) {
> -		printf("ERROR: bpf_prog_attach fails!\n");
> -		log_err("Attaching prog");
> +		bpf_program__set_expected_attach_type(bpf_prog, BPF_CGROUP_INET_INGRESS);
> +
> +	link = bpf_program__attach_cgroup(bpf_prog, cg1);
There is a difference here.
I think the bpf_prog will be detached when link is gone (e.g. process exit)
I am not sure it is what hbm is expected considering
cg is not clean-up on the success case.

> +	if (libbpf_get_error(link)) {
> +		fprintf(stderr, "ERROR: bpf_program__attach_cgroup failed\n");
> +		link = NULL;
not needed.  bpf_link__destroy() can handle err ptr.

>  		goto err;
>  	}
>  
> @@ -175,7 +175,7 @@ static int run_bpf_prog(char *prog, int cg_id)
>  #define DELTA_RATE_CHECK 10000		/* in us */
>  #define RATE_THRESHOLD 9500000000	/* 9.5 Gbps */
>  
> -		bpf_map_lookup_elem(map_fd, &key, &qstats);
> +		bpf_map_lookup_elem(queue_stats_fd, &key, &qstats);
>  		if (gettimeofday(&t0, NULL) < 0)
>  			do_error("gettimeofday failed", true);
>  		t_last = t0;
> @@ -204,7 +204,7 @@ static int run_bpf_prog(char *prog, int cg_id)
>  			fclose(fin);
>  			printf("  new_eth_tx_bytes:%llu\n",
>  			       new_eth_tx_bytes);
> -			bpf_map_lookup_elem(map_fd, &key, &qstats);
> +			bpf_map_lookup_elem(queue_stats_fd, &key, &qstats);
>  			new_cg_tx_bytes = qstats.bytes_total;
>  			delta_bytes = new_eth_tx_bytes - last_eth_tx_bytes;
>  			last_eth_tx_bytes = new_eth_tx_bytes;
> @@ -251,14 +251,14 @@ static int run_bpf_prog(char *prog, int cg_id)
>  					rate = minRate;
>  				qstats.rate = rate;
>  			}
> -			if (bpf_map_update_elem(map_fd, &key, &qstats, BPF_ANY))
> +			if (bpf_map_update_elem(queue_stats_fd, &key, &qstats, BPF_ANY))
>  				do_error("update map element fails", false);
>  		}
>  	} else {
>  		sleep(dur);
>  	}
>  	// Get stats!
> -	if (stats_flag && bpf_map_lookup_elem(map_fd, &key, &qstats)) {
> +	if (stats_flag && bpf_map_lookup_elem(queue_stats_fd, &key, &qstats)) {
>  		char fname[100];
>  		FILE *fout;
>  
> @@ -367,10 +367,12 @@ static int run_bpf_prog(char *prog, int cg_id)
>  err:
>  	rc = 1;
>  
> +	bpf_link__destroy(link);
> +
>  	if (cg1)
This test looks wrong since cg1 is a fd.

>  		close(cg1);
>  	cleanup_cgroup_environment();
> -
> +	bpf_object__close(obj);
>  	return rc;
>  }
>