/*
 * Functions related to generic timeout handling of requests.
 */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/blkdev.h>
#include <linux/fault-inject.h>

#include "blk.h"
#include "blk-mq.h"

#ifdef CONFIG_FAIL_IO_TIMEOUT

static DECLARE_FAULT_ATTR(fail_io_timeout);

static int __init setup_fail_io_timeout(char *str)
{
        return setup_fault_attr(&fail_io_timeout, str);
}
__setup("fail_io_timeout=", setup_fail_io_timeout);

int blk_should_fake_timeout(struct request_queue *q)
{
        if (!test_bit(QUEUE_FLAG_FAIL_IO, &q->queue_flags))
                return 0;

        return should_fail(&fail_io_timeout, 1);
}

static int __init fail_io_timeout_debugfs(void)
{
        struct dentry *dir = fault_create_debugfs_attr("fail_io_timeout",
                                                NULL, &fail_io_timeout);

        return PTR_ERR_OR_ZERO(dir);
}

late_initcall(fail_io_timeout_debugfs);

ssize_t part_timeout_show(struct device *dev, struct device_attribute *attr,
                          char *buf)
{
        struct gendisk *disk = dev_to_disk(dev);
        int set = test_bit(QUEUE_FLAG_FAIL_IO, &disk->queue->queue_flags);

        return sprintf(buf, "%d\n", set != 0);
}

ssize_t part_timeout_store(struct device *dev, struct device_attribute *attr,
                           const char *buf, size_t count)
{
        struct gendisk *disk = dev_to_disk(dev);
        int val;

        if (count) {
                struct request_queue *q = disk->queue;
                char *p = (char *) buf;

                val = simple_strtoul(p, &p, 10);
                if (val)
                        blk_queue_flag_set(QUEUE_FLAG_FAIL_IO, q);
                else
                        blk_queue_flag_clear(QUEUE_FLAG_FAIL_IO, q);
        }

        return count;
}

#endif /* CONFIG_FAIL_IO_TIMEOUT */

/*
 * blk_delete_timer - Delete/cancel timer for a given function.
 * @req:        request that we are canceling timer for
 *
 */
void blk_delete_timer(struct request *req)
{
        list_del_init(&req->timeout_list);
}

static void blk_rq_timed_out(struct request *req)
{
        struct request_queue *q = req->q;
        enum blk_eh_timer_return ret = BLK_EH_RESET_TIMER;

        if (q->rq_timed_out_fn)
                ret = q->rq_timed_out_fn(req);
        switch (ret) {
        case BLK_EH_HANDLED:
                __blk_complete_request(req);
                break;
        case BLK_EH_RESET_TIMER:
                blk_add_timer(req);
                blk_clear_rq_complete(req);
                break;
        case BLK_EH_NOT_HANDLED:
                /*
                 * LLD handles this for now but in the future
                 * we can send a request msg to abort the command
                 * and we can move more of the generic scsi eh code to
                 * the blk layer.
                 */
                break;
        default:
                printk(KERN_ERR "block: bad eh return: %d\n", ret);
                break;
        }
}

static void blk_rq_check_expired(struct request *rq, unsigned long *next_timeout,
                          unsigned int *next_set)
{
        const unsigned long deadline = blk_rq_deadline(rq);

        if (time_after_eq(jiffies, deadline)) {
                list_del_init(&rq->timeout_list);

                /*
                 * Check if we raced with end io completion
                 */
                if (!blk_mark_rq_complete(rq))
                        blk_rq_timed_out(rq);
        } else if (!*next_set || time_after(*next_timeout, deadline)) {
                *next_timeout = deadline;
                *next_set = 1;
        }
}

void blk_timeout_work(struct work_struct *work)
{
        struct request_queue *q =
                container_of(work, struct request_queue, timeout_work);
        unsigned long flags, next = 0;
        struct request *rq, *tmp;
        int next_set = 0;

        spin_lock_irqsave(q->queue_lock, flags);

        list_for_each_entry_safe(rq, tmp, &q->timeout_list, timeout_list)
                blk_rq_check_expired(rq, &next, &next_set);

        if (next_set)
                mod_timer(&q->timeout, round_jiffies_up(next));

        spin_unlock_irqrestore(q->queue_lock, flags);
}

/**
 * blk_abort_request -- Request request recovery for the specified command
 * @req:        pointer to the request of interest
 *
 * This function requests that the block layer start recovery for the
 * request by deleting the timer and calling the q's timeout function.
 * LLDDs who implement their own error recovery MAY ignore the timeout
 * event if they generated blk_abort_req. Must hold queue lock.
 */
void blk_abort_request(struct request *req)
{
        if (req->q->mq_ops) {
                /*
                 * All we need to ensure is that timeout scan takes place
                 * immediately and that scan sees the new timeout value.
                 * No need for fancy synchronizations.
                 */
                blk_rq_set_deadline(req, jiffies);
                kblockd_schedule_work(&req->q->timeout_work);
        } else {
                if (blk_mark_rq_complete(req))
                        return;
                blk_delete_timer(req);
                blk_rq_timed_out(req);
        }
}
EXPORT_SYMBOL_GPL(blk_abort_request);

unsigned long blk_rq_timeout(unsigned long timeout)
{
        unsigned long maxt;

        maxt = round_jiffies_up(jiffies + BLK_MAX_TIMEOUT);
        if (time_after(timeout, maxt))
                timeout = maxt;

        return timeout;
}

/**
 * blk_add_timer - Start timeout timer for a single request
 * @req:        request that is about to start running.
 *
 * Notes:
 *    Each request has its own timer, and as it is added to the queue, we
 *    set up the timer. When the request completes, we cancel the timer.
 */
void blk_add_timer(struct request *req)
{
        struct request_queue *q = req->q;
        unsigned long expiry;

        if (!q->mq_ops)
                lockdep_assert_held(q->queue_lock);

        /* blk-mq has its own handler, so we don't need ->rq_timed_out_fn */
        if (!q->mq_ops && !q->rq_timed_out_fn)
                return;

        BUG_ON(!list_empty(&req->timeout_list));

        /*
         * Some LLDs, like scsi, peek at the timeout to prevent a
         * command from being retried forever.
         */
        if (!req->timeout)
                req->timeout = q->rq_timeout;

        blk_rq_set_deadline(req, jiffies + req->timeout);
        req->rq_flags &= ~RQF_MQ_TIMEOUT_EXPIRED;

        /*
         * Only the non-mq case needs to add the request to a protected list.
         * For the mq case we simply scan the tag map.
         */
        if (!q->mq_ops)
                list_add_tail(&req->timeout_list, &req->q->timeout_list);

        /*
         * If the timer isn't already pending or this timeout is earlier
         * than an existing one, modify the timer. Round up to next nearest
         * second.
         */
        expiry = blk_rq_timeout(round_jiffies_up(blk_rq_deadline(req)));

        if (!timer_pending(&q->timeout) ||
            time_before(expiry, q->timeout.expires)) {
                unsigned long diff = q->timeout.expires - expiry;

                /*
                 * Due to added timer slack to group timers, the timer
                 * will often be a little in front of what we asked for.
                 * So apply some tolerance here too, otherwise we keep
                 * modifying the timer because expires for value X
                 * will be X + something.
                 */
                if (!timer_pending(&q->timeout) || (diff >= HZ / 2))
                        mod_timer(&q->timeout, expiry);
        }

}