/*
 * Copyright (C) 2006 Jens Axboe <axboe@suse.de>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 */
#include <linux/kernel.h>
#include <linux/blkdev.h>
#include <linux/blktrace_api.h>
#include <linux/percpu.h>
#include <linux/init.h>
#include <linux/mutex.h>
#include <linux/debugfs.h>
#include <asm/uaccess.h>

static DEFINE_PER_CPU(unsigned long long, blk_trace_cpu_offset) = { 0, };
static unsigned int blktrace_seq __read_mostly = 1;

/*
 * Send out a notify for this process, if we haven't done so since a trace
 * started
 */
static void trace_note_tsk(struct blk_trace *bt, struct task_struct *tsk)
{
        struct blk_io_trace *t;

        t = relay_reserve(bt->rchan, sizeof(*t) + sizeof(tsk->comm));
        if (t) {
                t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;
                t->device = bt->dev;
                t->action = BLK_TC_ACT(BLK_TC_NOTIFY);
                t->pid = tsk->pid;
                t->cpu = smp_processor_id();
                t->pdu_len = sizeof(tsk->comm);
                memcpy((void *) t + sizeof(*t), tsk->comm, t->pdu_len);
                tsk->btrace_seq = blktrace_seq;
        }
}

static int act_log_check(struct blk_trace *bt, u32 what, sector_t sector,
                         pid_t pid)
{
        if (((bt->act_mask << BLK_TC_SHIFT) & what) == 0)
                return 1;
        if (sector < bt->start_lba || sector > bt->end_lba)
                return 1;
        if (bt->pid && pid != bt->pid)
                return 1;

        return 0;
}

/*
 * Data direction bit lookup
 */
static u32 ddir_act[2] __read_mostly = { BLK_TC_ACT(BLK_TC_READ), BLK_TC_ACT(BLK_TC_WRITE) };

/*
 * Bio action bits of interest
 */
static u32 bio_act[5] __read_mostly = { 0, BLK_TC_ACT(BLK_TC_BARRIER), BLK_TC_ACT(BLK_TC_SYNC), 0, BLK_TC_ACT(BLK_TC_AHEAD) };

/*
 * More could be added as needed, taking care to increment the decrementer
 * to get correct indexing
 */
#define trace_barrier_bit(rw)   \
        (((rw) & (1 << BIO_RW_BARRIER)) >> (BIO_RW_BARRIER - 0))
#define trace_sync_bit(rw)      \
        (((rw) & (1 << BIO_RW_SYNC)) >> (BIO_RW_SYNC - 1))
#define trace_ahead_bit(rw)     \
        (((rw) & (1 << BIO_RW_AHEAD)) << (2 - BIO_RW_AHEAD))

/*
 * The worker for the various blk_add_trace*() types. Fills out a
 * blk_io_trace structure and places it in a per-cpu subbuffer.
 */
void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
                     int rw, u32 what, int error, int pdu_len, void *pdu_data)
{
        struct task_struct *tsk = current;
        struct blk_io_trace *t;
        unsigned long flags;
        unsigned long *sequence;
        pid_t pid;
        int cpu;

        if (unlikely(bt->trace_state != Blktrace_running))
                return;

        what |= ddir_act[rw & WRITE];
        what |= bio_act[trace_barrier_bit(rw)];
        what |= bio_act[trace_sync_bit(rw)];
        what |= bio_act[trace_ahead_bit(rw)];

        pid = tsk->pid;
        if (unlikely(act_log_check(bt, what, sector, pid)))
                return;

        /*
         * A word about the locking here - we disable interrupts to reserve
         * some space in the relay per-cpu buffer, to prevent an irq
         * from coming in and stepping on our toes. Once reserved, it's
         * enough to get preemption disabled to prevent read of this data
         * before we are through filling it. get_cpu()/put_cpu() does this
         * for us
         */
        local_irq_save(flags);

        if (unlikely(tsk->btrace_seq != blktrace_seq))
                trace_note_tsk(bt, tsk);

        t = relay_reserve(bt->rchan, sizeof(*t) + pdu_len);
        if (t) {
                cpu = smp_processor_id();
                sequence = per_cpu_ptr(bt->sequence, cpu);

                t->magic = BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;
                t->sequence = ++(*sequence);
                t->time = sched_clock() - per_cpu(blk_trace_cpu_offset, cpu);
                t->sector = sector;
                t->bytes = bytes;
                t->action = what;
                t->pid = pid;
                t->device = bt->dev;
                t->cpu = cpu;
                t->error = error;
                t->pdu_len = pdu_len;

                if (pdu_len)
                        memcpy((void *) t + sizeof(*t), pdu_data, pdu_len);
        }

        local_irq_restore(flags);
}

EXPORT_SYMBOL_GPL(__blk_add_trace);

static struct dentry *blk_tree_root;
static struct mutex blk_tree_mutex;
static unsigned int root_users;

static inline void blk_remove_root(void)
{
        if (blk_tree_root) {
                debugfs_remove(blk_tree_root);
                blk_tree_root = NULL;
        }
}

static void blk_remove_tree(struct dentry *dir)
{
        mutex_lock(&blk_tree_mutex);
        debugfs_remove(dir);
        if (--root_users == 0)
                blk_remove_root();
        mutex_unlock(&blk_tree_mutex);
}

static struct dentry *blk_create_tree(const char *blk_name)
{
        struct dentry *dir = NULL;

        mutex_lock(&blk_tree_mutex);

        if (!blk_tree_root) {
                blk_tree_root = debugfs_create_dir("block", NULL);
                if (!blk_tree_root)
                        goto err;
        }

        dir = debugfs_create_dir(blk_name, blk_tree_root);
        if (dir)
                root_users++;
        else
                blk_remove_root();

err:
        mutex_unlock(&blk_tree_mutex);
        return dir;
}

static void blk_trace_cleanup(struct blk_trace *bt)
{
        relay_close(bt->rchan);
        debugfs_remove(bt->dropped_file);
        blk_remove_tree(bt->dir);
        free_percpu(bt->sequence);
        kfree(bt);
}

static int blk_trace_remove(request_queue_t *q)
{
        struct blk_trace *bt;

        bt = xchg(&q->blk_trace, NULL);
        if (!bt)
                return -EINVAL;

        if (bt->trace_state == Blktrace_setup ||
            bt->trace_state == Blktrace_stopped)
                blk_trace_cleanup(bt);

        return 0;
}

static int blk_dropped_open(struct inode *inode, struct file *filp)
{
        filp->private_data = inode->u.generic_ip;

        return 0;
}

static ssize_t blk_dropped_read(struct file *filp, char __user *buffer,
                                size_t count, loff_t *ppos)
{
        struct blk_trace *bt = filp->private_data;
        char buf[16];

        snprintf(buf, sizeof(buf), "%u\n", atomic_read(&bt->dropped));

        return simple_read_from_buffer(buffer, count, ppos, buf, strlen(buf));
}

static struct file_operations blk_dropped_fops = {
        .owner =        THIS_MODULE,
        .open =         blk_dropped_open,
        .read =         blk_dropped_read,
};

/*
 * Keep track of how many times we encountered a full subbuffer, to aid
 * the user space app in telling how many lost events there were.
 */
static int blk_subbuf_start_callback(struct rchan_buf *buf, void *subbuf,
                                     void *prev_subbuf, size_t prev_padding)
{
        struct blk_trace *bt;

        if (!relay_buf_full(buf))
                return 1;

        bt = buf->chan->private_data;
        atomic_inc(&bt->dropped);
        return 0;
}

static int blk_remove_buf_file_callback(struct dentry *dentry)
{
        debugfs_remove(dentry);
        return 0;
}

static struct dentry *blk_create_buf_file_callback(const char *filename,
                                                   struct dentry *parent,
                                                   int mode,
                                                   struct rchan_buf *buf,
                                                   int *is_global)
{
        return debugfs_create_file(filename, mode, parent, buf,
                                        &relay_file_operations);
}

static struct rchan_callbacks blk_relay_callbacks = {
        .subbuf_start           = blk_subbuf_start_callback,
        .create_buf_file        = blk_create_buf_file_callback,
        .remove_buf_file        = blk_remove_buf_file_callback,
};

/*
 * Setup everything required to start tracing
 */
static int blk_trace_setup(request_queue_t *q, struct block_device *bdev,
                           char __user *arg)
{
        struct blk_user_trace_setup buts;
        struct blk_trace *old_bt, *bt = NULL;
        struct dentry *dir = NULL;
        char b[BDEVNAME_SIZE];
        int ret, i;

        if (copy_from_user(&buts, arg, sizeof(buts)))
                return -EFAULT;

        if (!buts.buf_size || !buts.buf_nr)
                return -EINVAL;

        strcpy(buts.name, bdevname(bdev, b));

        /*
         * some device names have larger paths - convert the slashes
         * to underscores for this to work as expected
         */
        for (i = 0; i < strlen(buts.name); i++)
                if (buts.name[i] == '/')
                        buts.name[i] = '_';

        if (copy_to_user(arg, &buts, sizeof(buts)))
                return -EFAULT;

        ret = -ENOMEM;
        bt = kzalloc(sizeof(*bt), GFP_KERNEL);
        if (!bt)
                goto err;

        bt->sequence = alloc_percpu(unsigned long);
        if (!bt->sequence)
                goto err;

        ret = -ENOENT;
        dir = blk_create_tree(buts.name);
        if (!dir)
                goto err;

        bt->dir = dir;
        bt->dev = bdev->bd_dev;
        atomic_set(&bt->dropped, 0);

        ret = -EIO;
        bt->dropped_file = debugfs_create_file("dropped", 0444, dir, bt, &blk_dropped_fops);
        if (!bt->dropped_file)
                goto err;

        bt->rchan = relay_open("trace", dir, buts.buf_size, buts.buf_nr, &blk_relay_callbacks);
        if (!bt->rchan)
                goto err;
        bt->rchan->private_data = bt;

        bt->act_mask = buts.act_mask;
        if (!bt->act_mask)
                bt->act_mask = (u16) -1;

        bt->start_lba = buts.start_lba;
        bt->end_lba = buts.end_lba;
        if (!bt->end_lba)
                bt->end_lba = -1ULL;

        bt->pid = buts.pid;
        bt->trace_state = Blktrace_setup;

        ret = -EBUSY;
        old_bt = xchg(&q->blk_trace, bt);
        if (old_bt) {
                (void) xchg(&q->blk_trace, old_bt);
                goto err;
        }

        return 0;
err:
        if (dir)
                blk_remove_tree(dir);
        if (bt) {
                if (bt->dropped_file)
                        debugfs_remove(bt->dropped_file);
                if (bt->sequence)
                        free_percpu(bt->sequence);
                if (bt->rchan)
                        relay_close(bt->rchan);
                kfree(bt);
        }
        return ret;
}

static int blk_trace_startstop(request_queue_t *q, int start)
{
        struct blk_trace *bt;
        int ret;

        if ((bt = q->blk_trace) == NULL)
                return -EINVAL;

        /*
         * For starting a trace, we can transition from a setup or stopped
         * trace. For stopping a trace, the state must be running
         */
        ret = -EINVAL;
        if (start) {
                if (bt->trace_state == Blktrace_setup ||
                    bt->trace_state == Blktrace_stopped) {
                        blktrace_seq++;
                        smp_mb();
                        bt->trace_state = Blktrace_running;
                        ret = 0;
                }
        } else {
                if (bt->trace_state == Blktrace_running) {
                        bt->trace_state = Blktrace_stopped;
                        relay_flush(bt->rchan);
                        ret = 0;
                }
        }

        return ret;
}

/**
 * blk_trace_ioctl: - handle the ioctls associated with tracing
 * @bdev:       the block device
 * @cmd:        the ioctl cmd
 * @arg:        the argument data, if any
 *
 **/
int blk_trace_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg)
{
        request_queue_t *q;
        int ret, start = 0;

        q = bdev_get_queue(bdev);
        if (!q)
                return -ENXIO;

        mutex_lock(&bdev->bd_mutex);

        switch (cmd) {
        case BLKTRACESETUP:
                ret = blk_trace_setup(q, bdev, arg);
                break;
        case BLKTRACESTART:
                start = 1;
        case BLKTRACESTOP:
                ret = blk_trace_startstop(q, start);
                break;
        case BLKTRACETEARDOWN:
                ret = blk_trace_remove(q);
                break;
        default:
                ret = -ENOTTY;
                break;
        }

        mutex_unlock(&bdev->bd_mutex);
        return ret;
}

/**
 * blk_trace_shutdown: - stop and cleanup trace structures
 * @q:    the request queue associated with the device
 *
 **/
void blk_trace_shutdown(request_queue_t *q)
{
        blk_trace_startstop(q, 0);
        blk_trace_remove(q);
}

/*
 * Average offset over two calls to sched_clock() with a gettimeofday()
 * in the middle
 */
static void blk_check_time(unsigned long long *t)
{
        unsigned long long a, b;
        struct timeval tv;

        a = sched_clock();
        do_gettimeofday(&tv);
        b = sched_clock();

        *t = tv.tv_sec * 1000000000 + tv.tv_usec * 1000;
        *t -= (a + b) / 2;
}

static void blk_trace_check_cpu_time(void *data)
{
        unsigned long long *t;
        int cpu = get_cpu();

        t = &per_cpu(blk_trace_cpu_offset, cpu);

        /*
         * Just call it twice, hopefully the second call will be cache hot
         * and a little more precise
         */
        blk_check_time(t);
        blk_check_time(t);

        put_cpu();
}

/*
 * Call blk_trace_check_cpu_time() on each CPU to calibrate our inter-CPU
 * timings
 */
static void blk_trace_calibrate_offsets(void)
{
        unsigned long flags;

        smp_call_function(blk_trace_check_cpu_time, NULL, 1, 1);
        local_irq_save(flags);
        blk_trace_check_cpu_time(NULL);
        local_irq_restore(flags);
}

static void blk_trace_set_ht_offsets(void)
{
#if defined(CONFIG_SCHED_SMT)
        int cpu, i;

        /*
         * now make sure HT siblings have the same time offset
         */
        preempt_disable();
        for_each_online_cpu(cpu) {
                unsigned long long *cpu_off, *sibling_off;

                for_each_cpu_mask(i, cpu_sibling_map[cpu]) {
                        if (i == cpu)
                                continue;

                        cpu_off = &per_cpu(blk_trace_cpu_offset, cpu);
                        sibling_off = &per_cpu(blk_trace_cpu_offset, i);
                        *sibling_off = *cpu_off;
                }
        }
        preempt_enable();
#endif
}

static __init int blk_trace_init(void)
{
        mutex_init(&blk_tree_mutex);
        blk_trace_calibrate_offsets();
        blk_trace_set_ht_offsets();

        return 0;
}

module_init(blk_trace_init);