libbpf-tools/mdflush.c

/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */

/*
 * mdflush	Trace md flush events.
 *
 * Copyright (c) 2021~2022 Hengqi Chen
 *
 * Based on mdflush(8) from BCC by Brendan Gregg.
 * 08-Nov-2021   Hengqi Chen   Created this.
 */
#include <argp.h>
#include <errno.h>
#include <signal.h>
#include <string.h>
#include <time.h>

#include <bpf/libbpf.h>
#include <bpf/bpf.h>
#include "mdflush.h"
#include "mdflush.skel.h"
#include "trace_helpers.h"

#define PERF_BUFFER_PAGES	16
#define PERF_POLL_TIMEOUT_MS	100
#define warn(...) fprintf(stderr, __VA_ARGS__)

static volatile sig_atomic_t exiting = 0;
static bool verbose = false;

const char *argp_program_version = "mdflush 0.1";
const char *argp_program_bug_address =
	"https://github.com/iovisor/bcc/tree/master/libbpf-tools";
const char argp_program_doc[] =
"Trace md flush events.\n"
"\n"
"USAGE: mdflush\n";

static const struct argp_option opts[] = {
	{ "verbose", 'v', NULL, 0, "Verbose debug output" },
	{ NULL, 'h', NULL, OPTION_HIDDEN, "Show the full help" },
	{},
};

static error_t parse_arg(int key, char *arg, struct argp_state *state)
{
	switch (key) {
	case 'h':
		argp_state_help(state, stderr, ARGP_HELP_STD_HELP);
		break;
	case 'v':
		verbose = true;
		break;
	default:
		return ARGP_ERR_UNKNOWN;
	}
	return 0;
}

static void sig_int(int signo)
{
	exiting = 1;
}

static int libbpf_print_fn(enum libbpf_print_level level, const char *format, va_list args)
{
	if (level == LIBBPF_DEBUG && !verbose)
		return 0;
	return vfprintf(stderr, format, args);
}

static void handle_event(void *ctx, int cpu, void *data, __u32 data_sz)
{
	struct event *e = data;
	time_t t;
	struct tm *tm;
	char ts[32];

	time(&t);
	tm = localtime(&t);
	strftime(ts, sizeof(ts), "%H:%M:%S", tm);
	printf("%-8s %-7d %-16s %-s\n",
	       ts, e->pid, e->comm, e->disk);
}

static void handle_lost_events(void *ctx, int cpu, __u64 lost_cnt)
{
	warn("lost %llu events on CPU #%d\n", lost_cnt, cpu);
}

int main(int argc, char **argv)
{
	static const struct argp argp = {
		.options = opts,
		.parser = parse_arg,
		.doc = argp_program_doc,
	};
	struct perf_buffer *pb = NULL;
	struct mdflush_bpf *obj;
	int err;

	err = argp_parse(&argp, argc, argv, 0, NULL, NULL);
	if (err)
		return err;

	libbpf_set_print(libbpf_print_fn);

	obj = mdflush_bpf__open();
	if (!obj) {
		warn("failed to open BPF object\n");
		return 1;
	}

	if (fentry_can_attach("md_flush_request", NULL))
		bpf_program__set_autoload(obj->progs.kprobe_md_flush_request, false);
	else
		bpf_program__set_autoload(obj->progs.md_flush_request, false);

	err = mdflush_bpf__load(obj);
	if (err) {
		warn("failed to load BPF object: %d\n", err);
		goto cleanup;
	}

	err = mdflush_bpf__attach(obj);
	if (err) {
		warn("failed to attach BPF programs: %d\n", err);
		goto cleanup;
	}

	pb = perf_buffer__new(bpf_map__fd(obj->maps.events), PERF_BUFFER_PAGES,
			      handle_event, handle_lost_events, NULL, NULL);
	if (!pb) {
		warn("failed to open perf buffer: %d\n", err);
		goto cleanup;
	}

	if (signal(SIGINT, sig_int) == SIG_ERR) {
		warn("can't set signal handler: %s\n", strerror(errno));
		err = 1;
		goto cleanup;
	}

	printf("Tracing md flush requests... Hit Ctrl-C to end.\n");
	printf("%-8s %-7s %-16s %-s\n",
	       "TIME", "PID", "COMM", "DEVICE");

	while (!exiting) {
		err = perf_buffer__poll(pb, PERF_POLL_TIMEOUT_MS);
		if (err < 0 && err != -EINTR) {
			warn("error polling perf buffer: %s\n", strerror(-err));
			goto cleanup;
		}
		/* reset err to return 0 if exiting */
		err = 0;
	}

cleanup:
	perf_buffer__free(pb);
	mdflush_bpf__destroy(obj);

	return err != 0;
}