Re: [PATCH bpf-next v2 1/7] samples: bpf: refactor hbm program with libbpf

[Martin KaFai Lau <kafai@fb.com>]

On Fri, Nov 20, 2020 at 06:34:05PM -0800, Martin KaFai Lau wrote:
> On Thu, Nov 19, 2020 at 03:06:11PM +0000, Daniel T. Lee wrote:
> [ ... ]
> 
> >  static int run_bpf_prog(char *prog, int cg_id)
> >  {
> > -	int map_fd;
> > -	int rc = 0;
> > +	struct hbm_queue_stats qstats = {0};
> > +	char cg_dir[100], cg_pin_path[100];
> > +	struct bpf_link *link = NULL;
> >  	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");
> > @@ -190,16 +183,25 @@ 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);
> > +	if (libbpf_get_error(link)) {
> > +		fprintf(stderr, "ERROR: bpf_program__attach_cgroup failed\n");
> > +		link = NULL;
> Again, this is not needed.  bpf_link__destroy() can
> handle both NULL and error pointer.  Please take a look
> at the bpf_link__destroy() in libbpf.c
> 
> > +		goto err;
> > +	}
> > +
> > +	sprintf(cg_pin_path, "/sys/fs/bpf/hbm%d", cg_id);
> > +	rc = bpf_link__pin(link, cg_pin_path);
> > +	if (rc < 0) {
> > +		printf("ERROR: bpf_link__pin failed: %d\n", rc);
> >  		goto err;
> >  	}
> >  
> > @@ -213,7 +215,7 @@ 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;
> > @@ -242,7 +244,7 @@ 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;
> > @@ -289,14 +291,14 @@ 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;
> >  
> > @@ -398,10 +400,10 @@ static int run_bpf_prog(char *prog, int cg_id)
> >  err:
> >  	rc = 1;
> >  
> > -	if (cg1)
> > -		close(cg1);
> > +	bpf_link__destroy(link);
> > +	close(cg1);
> >  	cleanup_cgroup_environment();
> > -
> > +	bpf_object__close(obj);
> The bpf_* cleanup condition still looks wrong.
> 
> I can understand why it does not want to cleanup_cgroup_environment()
> on the success case because the sh script may want to run test under this
> cgroup.
> 
> However, the bpf_link__destroy(), bpf_object__close(), and
> even close(cg1) should be done in both success and error
> cases.
> 
> The cg1 test still looks wrong also.  The cg1 should
> be init to -1 and then test for "if (cg1 == -1)".
oops.  I meant cg1 != -1 .