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
  15 static DECLARE_FAULT_ATTR(fail_io_timeout);
  16
  17 static 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
  23 bool __blk_should_fake_timeout(struct request_queue *q)
  24 {
  25         return should_fail(&fail_io_timeout, 1);
  26 }
  27 EXPORT_SYMBOL_GPL(__blk_should_fake_timeout);
  28
  29 static 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
  37 late_initcall(fail_io_timeout_debugfs);
  38
  39 ssize_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
  48 ssize_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  */
  79 void 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 }
  89 EXPORT_SYMBOL_GPL(blk_abort_request);
  90
  91 static unsigned long blk_timeout_mask __read_mostly;
  92
  93 static int __init blk_timeout_init(void)
  94 {
  95         blk_timeout_mask = roundup_pow_of_two(HZ) - 1;
  96         return 0;
  97 }
  98
  99 late_initcall(blk_timeout_init);
 100
 101 /*
 102  * Just a rough estimate, we don't care about specific values for timeouts.
 103  */
 104 static inline unsigned long blk_round_jiffies(unsigned long j)
 105 {
 106         return (j + blk_timeout_mask) + 1;
 107 }
 108
 109 unsigned 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  */
 128 void 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 }