blk-timeout.c

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/*
 * 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"

#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 IS_ERR(dir) ? PTR_ERR(dir) : 0;
}

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);
        spin_lock_irq(q->queue_lock);
        if (val)
            queue_flag_set(QUEUE_FLAG_FAIL_IO, q);
        else
            queue_flag_clear(QUEUE_FLAG_FAIL_IO, q);
        spin_unlock_irq(q->queue_lock);
    }

    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;

    ret = q->rq_timed_out_fn(req);
    switch (ret) {
    case BLK_EH_HANDLED:
        __blk_complete_request(req);
        break;
    case BLK_EH_RESET_TIMER:
        blk_clear_rq_complete(req);
        blk_add_timer(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;
    }
}

void blk_rq_timed_out_timer(unsigned long data)
{
    struct request_queue *q = (struct request_queue *) data;
    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) {
        if (time_after_eq(jiffies, rq->deadline)) {
            list_del_init(&rq->timeout_list);

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

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

    spin_unlock_irqrestore(q->queue_lock, flags);
}

void blk_abort_request(struct request *req)
{
    if (blk_mark_rq_complete(req))
        return;
    blk_delete_timer(req);
    blk_rq_timed_out(req);
}
EXPORT_SYMBOL_GPL(blk_abort_request);

void blk_add_timer(struct request *req)
{
    struct request_queue *q = req->q;
    unsigned long expiry;

    if (!q->rq_timed_out_fn)
        return;

    BUG_ON(!list_empty(&req->timeout_list));
    BUG_ON(test_bit(REQ_ATOM_COMPLETE, &req->atomic_flags));

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

    req->deadline = jiffies + req->timeout;
    list_add_tail(&req->timeout_list, &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 = round_jiffies_up(req->deadline);

    if (!timer_pending(&q->timeout) ||
        time_before(expiry, q->timeout.expires))
        mod_timer(&q->timeout, expiry);
}