// SPDX-License-Identifier: GPL-2.0
// Copyright (c) 2020 Wenbo Zhang
#include "vmlinux.h"
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_core_read.h>
#include <bpf/bpf_tracing.h>
#include "biostacks.h"
#include "bits.bpf.h"
#include "maps.bpf.h"

#define MAX_ENTRIES	10240
#define NULL		0

const volatile bool targ_ms = false;
const volatile dev_t targ_dev = -1;

struct internal_rqinfo {
	u64 start_ts;
	struct rqinfo rqinfo;
};

struct {
	__uint(type, BPF_MAP_TYPE_HASH);
	__uint(max_entries, MAX_ENTRIES);
	__type(key, struct request *);
	__type(value, struct internal_rqinfo);
	__uint(map_flags, BPF_F_NO_PREALLOC);
} rqinfos SEC(".maps");

struct {
	__uint(type, BPF_MAP_TYPE_HASH);
	__uint(max_entries, MAX_ENTRIES);
	__type(key, struct rqinfo);
	__type(value, struct hist);
	__uint(map_flags, BPF_F_NO_PREALLOC);
} hists SEC(".maps");

static struct hist zero;

static __always_inline
int trace_start(void *ctx, struct request *rq, bool merge_bio)
{
	struct internal_rqinfo *i_rqinfop = NULL, i_rqinfo = {};
	struct gendisk *disk = BPF_CORE_READ(rq, rq_disk);
	dev_t dev;

	dev = disk ? MKDEV(BPF_CORE_READ(disk, major),
			BPF_CORE_READ(disk, first_minor)) : 0;
	if (targ_dev != -1 && targ_dev != dev)
		return 0;

	if (merge_bio)
		i_rqinfop = bpf_map_lookup_elem(&rqinfos, &rq);
	if (!i_rqinfop)
		i_rqinfop = &i_rqinfo;

	i_rqinfop->start_ts = bpf_ktime_get_ns();
	i_rqinfop->rqinfo.pid = bpf_get_current_pid_tgid();
	i_rqinfop->rqinfo.kern_stack_size =
		bpf_get_stack(ctx, i_rqinfop->rqinfo.kern_stack,
			sizeof(i_rqinfop->rqinfo.kern_stack), 0);
	bpf_get_current_comm(&i_rqinfop->rqinfo.comm,
			sizeof(&i_rqinfop->rqinfo.comm));
	i_rqinfop->rqinfo.dev = dev;

	if (i_rqinfop == &i_rqinfo)
		bpf_map_update_elem(&rqinfos, &rq, i_rqinfop, 0);
	return 0;
}

SEC("fentry/blk_account_io_start")
int BPF_PROG(blk_account_io_start, struct request *rq)
{
	return trace_start(ctx, rq, false);
}

SEC("kprobe/blk_account_io_merge_bio")
int BPF_KPROBE(blk_account_io_merge_bio, struct request *rq)
{
	return trace_start(ctx, rq, true);
}

SEC("fentry/blk_account_io_done")
int BPF_PROG(blk_account_io_done, struct request *rq)
{
	u64 slot, ts = bpf_ktime_get_ns();
	struct internal_rqinfo *i_rqinfop;
	struct rqinfo *rqinfop;
	struct hist *histp;
	s64 delta;

	i_rqinfop = bpf_map_lookup_elem(&rqinfos, &rq);
	if (!i_rqinfop)
		return 0;
	delta = (s64)(ts - i_rqinfop->start_ts);
	if (delta < 0)
		goto cleanup;
	histp = bpf_map_lookup_or_try_init(&hists, &i_rqinfop->rqinfo, &zero);
	if (!histp)
		goto cleanup;
	if (targ_ms)
		delta /= 1000000U;
	else
		delta /= 1000U;
	slot = log2l(delta);
	if (slot >= MAX_SLOTS)
		slot = MAX_SLOTS - 1;
	__sync_fetch_and_add(&histp->slots[slot], 1);

cleanup:
	bpf_map_delete_elem(&rqinfos, &rq);
	return 0;
}

char LICENSE[] SEC("license") = "GPL";
