LXR linux/block/blk-timeout.c

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * Functions related to generic timeout handling of requests.
   4 */
   5#include <linux/kernel.h>
   6#include <linux/module.h>
   7#include <linux/blkdev.h>
   8#include <linux/fault-inject.h>
   9
  10#include "blk.h"
  11#include "blk-mq.h"
  12
  13#ifdef CONFIG_FAIL_IO_TIMEOUT
  14
  15static DECLARE_FAULT_ATTR(fail_io_timeout);
  16
  17static int __init setup_fail_io_timeout(char *str)
  18{
  19        return setup_fault_attr(&fail_io_timeout, str);
  20}
  21__setup("fail_io_timeout=", setup_fail_io_timeout);
  22
  23bool __blk_should_fake_timeout(struct request_queue *q)
  24{
  25        return should_fail(&fail_io_timeout, 1);
  26}
  27EXPORT_SYMBOL_GPL(__blk_should_fake_timeout);
  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 PTR_ERR_OR_ZERO(dir);
  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                if (val)
  60                        blk_queue_flag_set(QUEUE_FLAG_FAIL_IO, q);
  61                else
  62                        blk_queue_flag_clear(QUEUE_FLAG_FAIL_IO, q);
  63        }
  64
  65        return count;
  66}
  67
  68#endif /* CONFIG_FAIL_IO_TIMEOUT */
  69
  70/**
  71 * blk_abort_request - Request recovery for the specified command
  72 * @req:        pointer to the request of interest
  73 *
  74 * This function requests that the block layer start recovery for the
  75 * request by deleting the timer and calling the q's timeout function.
  76 * LLDDs who implement their own error recovery MAY ignore the timeout
  77 * event if they generated blk_abort_request.
  78 */
  79void blk_abort_request(struct request *req)
  80{
  81        /*
  82         * All we need to ensure is that timeout scan takes place
  83         * immediately and that scan sees the new timeout value.
  84         * No need for fancy synchronizations.
  85         */
  86        WRITE_ONCE(req->deadline, jiffies);
  87        kblockd_schedule_work(&req->q->timeout_work);
  88}
  89EXPORT_SYMBOL_GPL(blk_abort_request);
  90
  91static unsigned long blk_timeout_mask __read_mostly;
  92
  93static int __init blk_timeout_init(void)
  94{
  95        blk_timeout_mask = roundup_pow_of_two(HZ) - 1;
  96        return 0;
  97}
  98
  99late_initcall(blk_timeout_init);
 100
 101/*
 102 * Just a rough estimate, we don't care about specific values for timeouts.
 103 */
 104static inline unsigned long blk_round_jiffies(unsigned long j)
 105{
 106        return (j + blk_timeout_mask) + 1;
 107}
 108
 109unsigned long blk_rq_timeout(unsigned long timeout)
 110{
 111        unsigned long maxt;
 112
 113        maxt = blk_round_jiffies(jiffies + BLK_MAX_TIMEOUT);
 114        if (time_after(timeout, maxt))
 115                timeout = maxt;
 116
 117        return timeout;
 118}
 119
 120/**
 121 * blk_add_timer - Start timeout timer for a single request
 122 * @req:        request that is about to start running.
 123 *
 124 * Notes:
 125 *    Each request has its own timer, and as it is added to the queue, we
 126 *    set up the timer. When the request completes, we cancel the timer.
 127 */
 128void blk_add_timer(struct request *req)
 129{
 130        struct request_queue *q = req->q;
 131        unsigned long expiry;
 132
 133        /*
 134         * Some LLDs, like scsi, peek at the timeout to prevent a
 135         * command from being retried forever.
 136         */
 137        if (!req->timeout)
 138                req->timeout = q->rq_timeout;
 139
 140        req->rq_flags &= ~RQF_TIMED_OUT;
 141
 142        expiry = jiffies + req->timeout;
 143        WRITE_ONCE(req->deadline, expiry);
 144
 145        /*
 146         * If the timer isn't already pending or this timeout is earlier
 147         * than an existing one, modify the timer. Round up to next nearest
 148         * second.
 149         */
 150        expiry = blk_rq_timeout(blk_round_jiffies(expiry));
 151
 152        if (!timer_pending(&q->timeout) ||
 153            time_before(expiry, q->timeout.expires)) {
 154                unsigned long diff = q->timeout.expires - expiry;
 155
 156                /*
 157                 * Due to added timer slack to group timers, the timer
 158                 * will often be a little in front of what we asked for.
 159                 * So apply some tolerance here too, otherwise we keep
 160                 * modifying the timer because expires for value X
 161                 * will be X + something.
 162                 */
 163                if (!timer_pending(&q->timeout) || (diff >= HZ / 2))
 164                        mod_timer(&q->timeout, expiry);
 165        }
 166
 167}
 168