linux/block/blk-timeout.c
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   1/*
   2 * Functions related to generic timeout handling of requests.
   3 */
   4#include <linux/kernel.h>
   5#include <linux/module.h>
   6#include <linux/blkdev.h>
   7#include <linux/fault-inject.h>
   8
   9#include "blk.h"
  10
  11#ifdef CONFIG_FAIL_IO_TIMEOUT
  12
  13static DECLARE_FAULT_ATTR(fail_io_timeout);
  14
  15static int __init setup_fail_io_timeout(char *str)
  16{
  17        return setup_fault_attr(&fail_io_timeout, str);
  18}
  19__setup("fail_io_timeout=", setup_fail_io_timeout);
  20
  21int blk_should_fake_timeout(struct request_queue *q)
  22{
  23        if (!test_bit(QUEUE_FLAG_FAIL_IO, &q->queue_flags))
  24                return 0;
  25
  26        return should_fail(&fail_io_timeout, 1);
  27}
  28
  29static int __init fail_io_timeout_debugfs(void)
  30{
  31        struct dentry *dir = fault_create_debugfs_attr("fail_io_timeout",
  32                                                NULL, &fail_io_timeout);
  33
  34        return IS_ERR(dir) ? PTR_ERR(dir) : 0;
  35}
  36
  37late_initcall(fail_io_timeout_debugfs);
  38
  39ssize_t part_timeout_show(struct device *dev, struct device_attribute *attr,
  40                          char *buf)
  41{
  42        struct gendisk *disk = dev_to_disk(dev);
  43        int set = test_bit(QUEUE_FLAG_FAIL_IO, &disk->queue->queue_flags);
  44
  45        return sprintf(buf, "%d\n", set != 0);
  46}
  47
  48ssize_t part_timeout_store(struct device *dev, struct device_attribute *attr,
  49                           const char *buf, size_t count)
  50{
  51        struct gendisk *disk = dev_to_disk(dev);
  52        int val;
  53
  54        if (count) {
  55                struct request_queue *q = disk->queue;
  56                char *p = (char *) buf;
  57
  58                val = simple_strtoul(p, &p, 10);
  59                spin_lock_irq(q->queue_lock);
  60                if (val)
  61                        queue_flag_set(QUEUE_FLAG_FAIL_IO, q);
  62                else
  63                        queue_flag_clear(QUEUE_FLAG_FAIL_IO, q);
  64                spin_unlock_irq(q->queue_lock);
  65        }
  66
  67        return count;
  68}
  69
  70#endif /* CONFIG_FAIL_IO_TIMEOUT */
  71
  72/*
  73 * blk_delete_timer - Delete/cancel timer for a given function.
  74 * @req:        request that we are canceling timer for
  75 *
  76 */
  77void blk_delete_timer(struct request *req)
  78{
  79        list_del_init(&req->timeout_list);
  80}
  81
  82static void blk_rq_timed_out(struct request *req)
  83{
  84        struct request_queue *q = req->q;
  85        enum blk_eh_timer_return ret = BLK_EH_RESET_TIMER;
  86
  87        if (q->rq_timed_out_fn)
  88                ret = q->rq_timed_out_fn(req);
  89        switch (ret) {
  90        case BLK_EH_HANDLED:
  91                __blk_complete_request(req);
  92                break;
  93        case BLK_EH_RESET_TIMER:
  94                blk_clear_rq_complete(req);
  95                blk_add_timer(req);
  96                break;
  97        case BLK_EH_NOT_HANDLED:
  98                /*
  99                 * LLD handles this for now but in the future
 100                 * we can send a request msg to abort the command
 101                 * and we can move more of the generic scsi eh code to
 102                 * the blk layer.
 103                 */
 104                break;
 105        default:
 106                printk(KERN_ERR "block: bad eh return: %d\n", ret);
 107                break;
 108        }
 109}
 110
 111void blk_rq_timed_out_timer(unsigned long data)
 112{
 113        struct request_queue *q = (struct request_queue *) data;
 114        unsigned long flags, next = 0;
 115        struct request *rq, *tmp;
 116        int next_set = 0;
 117
 118        spin_lock_irqsave(q->queue_lock, flags);
 119
 120        list_for_each_entry_safe(rq, tmp, &q->timeout_list, timeout_list) {
 121                if (time_after_eq(jiffies, rq->deadline)) {
 122                        list_del_init(&rq->timeout_list);
 123
 124                        /*
 125                         * Check if we raced with end io completion
 126                         */
 127                        if (blk_mark_rq_complete(rq))
 128                                continue;
 129                        blk_rq_timed_out(rq);
 130                } else if (!next_set || time_after(next, rq->deadline)) {
 131                        next = rq->deadline;
 132                        next_set = 1;
 133                }
 134        }
 135
 136        if (next_set)
 137                mod_timer(&q->timeout, round_jiffies_up(next));
 138
 139        spin_unlock_irqrestore(q->queue_lock, flags);
 140}
 141
 142/**
 143 * blk_abort_request -- Request request recovery for the specified command
 144 * @req:        pointer to the request of interest
 145 *
 146 * This function requests that the block layer start recovery for the
 147 * request by deleting the timer and calling the q's timeout function.
 148 * LLDDs who implement their own error recovery MAY ignore the timeout
 149 * event if they generated blk_abort_req. Must hold queue lock.
 150 */
 151void blk_abort_request(struct request *req)
 152{
 153        if (blk_mark_rq_complete(req))
 154                return;
 155        blk_delete_timer(req);
 156        blk_rq_timed_out(req);
 157}
 158EXPORT_SYMBOL_GPL(blk_abort_request);
 159
 160/**
 161 * blk_add_timer - Start timeout timer for a single request
 162 * @req:        request that is about to start running.
 163 *
 164 * Notes:
 165 *    Each request has its own timer, and as it is added to the queue, we
 166 *    set up the timer. When the request completes, we cancel the timer.
 167 */
 168void blk_add_timer(struct request *req)
 169{
 170        struct request_queue *q = req->q;
 171        unsigned long expiry;
 172
 173        if (!q->rq_timed_out_fn)
 174                return;
 175
 176        BUG_ON(!list_empty(&req->timeout_list));
 177        BUG_ON(test_bit(REQ_ATOM_COMPLETE, &req->atomic_flags));
 178
 179        /*
 180         * Some LLDs, like scsi, peek at the timeout to prevent a
 181         * command from being retried forever.
 182         */
 183        if (!req->timeout)
 184                req->timeout = q->rq_timeout;
 185
 186        req->deadline = jiffies + req->timeout;
 187        list_add_tail(&req->timeout_list, &q->timeout_list);
 188
 189        /*
 190         * If the timer isn't already pending or this timeout is earlier
 191         * than an existing one, modify the timer. Round up to next nearest
 192         * second.
 193         */
 194        expiry = round_jiffies_up(req->deadline);
 195
 196        if (!timer_pending(&q->timeout) ||
 197            time_before(expiry, q->timeout.expires))
 198                mod_timer(&q->timeout, expiry);
 199}
 200
 201
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