block/blk-timeout.c

   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 #include "blk-mq.h"
  11
  12 #ifdef CONFIG_FAIL_IO_TIMEOUT
  13
  14 static DECLARE_FAULT_ATTR(fail_io_timeout);
  15
  16 static int __init setup_fail_io_timeout(char *str)
  17 {
  18         return setup_fault_attr(&fail_io_timeout, str);
  19 }
  20 __setup("fail_io_timeout=", setup_fail_io_timeout);
  21
  22 int blk_should_fake_timeout(struct request_queue *q)
  23 {
  24         if (!test_bit(QUEUE_FLAG_FAIL_IO, &q->queue_flags))
  25                 return 0;
  26
  27         return should_fail(&fail_io_timeout, 1);
  28 }
  29
  30 static int __init fail_io_timeout_debugfs(void)
  31 {
  32         struct dentry *dir = fault_create_debugfs_attr("fail_io_timeout",
  33                                                 NULL, &fail_io_timeout);
  34
  35         return PTR_ERR_OR_ZERO(dir);
  36 }
  37
  38 late_initcall(fail_io_timeout_debugfs);
  39
  40 ssize_t part_timeout_show(struct device *dev, struct device_attribute *attr,
  41                           char *buf)
  42 {
  43         struct gendisk *disk = dev_to_disk(dev);
  44         int set = test_bit(QUEUE_FLAG_FAIL_IO, &disk->queue->queue_flags);
  45
  46         return sprintf(buf, "%d\n", set != 0);
  47 }
  48
  49 ssize_t part_timeout_store(struct device *dev, struct device_attribute *attr,
  50                            const char *buf, size_t count)
  51 {
  52         struct gendisk *disk = dev_to_disk(dev);
  53         int val;
  54
  55         if (count) {
  56                 struct request_queue *q = disk->queue;
  57                 char *p = (char *) buf;
  58
  59                 val = simple_strtoul(p, &p, 10);
  60                 spin_lock_irq(q->queue_lock);
  61                 if (val)
  62                         queue_flag_set(QUEUE_FLAG_FAIL_IO, q);
  63                 else
  64                         queue_flag_clear(QUEUE_FLAG_FAIL_IO, q);
  65                 spin_unlock_irq(q->queue_lock);
  66         }
  67
  68         return count;
  69 }
  70
  71 #endif /* CONFIG_FAIL_IO_TIMEOUT */
  72
  73 /*
  74  * blk_delete_timer - Delete/cancel timer for a given function.
  75  * @req:        request that we are canceling timer for
  76  *
  77  */
  78 void blk_delete_timer(struct request *req)
  79 {
  80         list_del_init(&req->timeout_list);
  81 }
  82
  83 static void blk_rq_timed_out(struct request *req)
  84 {
  85         struct request_queue *q = req->q;
  86         enum blk_eh_timer_return ret = BLK_EH_RESET_TIMER;
  87
  88         if (q->rq_timed_out_fn)
  89                 ret = q->rq_timed_out_fn(req);
  90         switch (ret) {
  91         case BLK_EH_HANDLED:
  92                 /* Can we use req->errors here? */
  93                 if (q->mq_ops)
  94                         __blk_mq_complete_request(req);
  95                 else
  96                         __blk_complete_request(req);
  97                 break;
  98         case BLK_EH_RESET_TIMER:
  99                 blk_add_timer(req);
 100                 blk_clear_rq_complete(req);
 101                 break;
 102         case BLK_EH_NOT_HANDLED:
 103                 /*
 104                  * LLD handles this for now but in the future
 105                  * we can send a request msg to abort the command
 106                  * and we can move more of the generic scsi eh code to
 107                  * the blk layer.
 108                  */
 109                 break;
 110         default:
 111                 printk(KERN_ERR "block: bad eh return: %d\n", ret);
 112                 break;
 113         }
 114 }
 115
 116 void blk_rq_check_expired(struct request *rq, unsigned long *next_timeout,
 117                           unsigned int *next_set)
 118 {
 119         if (time_after_eq(jiffies, rq->deadline)) {
 120                 list_del_init(&rq->timeout_list);
 121
 122                 /*
 123                  * Check if we raced with end io completion
 124                  */
 125                 if (!blk_mark_rq_complete(rq))
 126                         blk_rq_timed_out(rq);
 127         } else if (!*next_set || time_after(*next_timeout, rq->deadline)) {
 128                 *next_timeout = rq->deadline;
 129                 *next_set = 1;
 130         }
 131 }
 132
 133 void blk_rq_timed_out_timer(unsigned long data)
 134 {
 135         struct request_queue *q = (struct request_queue *) data;
 136         unsigned long flags, next = 0;
 137         struct request *rq, *tmp;
 138         int next_set = 0;
 139
 140         spin_lock_irqsave(q->queue_lock, flags);
 141
 142         list_for_each_entry_safe(rq, tmp, &q->timeout_list, timeout_list)
 143                 blk_rq_check_expired(rq, &next, &next_set);
 144
 145         if (next_set)
 146                 mod_timer(&q->timeout, round_jiffies_up(next));
 147
 148         spin_unlock_irqrestore(q->queue_lock, flags);
 149 }
 150
 151 /**
 152  * blk_abort_request -- Request request recovery for the specified command
 153  * @req:        pointer to the request of interest
 154  *
 155  * This function requests that the block layer start recovery for the
 156  * request by deleting the timer and calling the q's timeout function.
 157  * LLDDs who implement their own error recovery MAY ignore the timeout
 158  * event if they generated blk_abort_req. Must hold queue lock.
 159  */
 160 void blk_abort_request(struct request *req)
 161 {
 162         if (blk_mark_rq_complete(req))
 163                 return;
 164         blk_delete_timer(req);
 165         blk_rq_timed_out(req);
 166 }
 167 EXPORT_SYMBOL_GPL(blk_abort_request);
 168
 169 unsigned long blk_rq_timeout(unsigned long timeout)
 170 {
 171         unsigned long maxt;
 172
 173         maxt = round_jiffies_up(jiffies + BLK_MAX_TIMEOUT);
 174         if (time_after(timeout, maxt))
 175                 timeout = maxt;
 176
 177         return timeout;
 178 }
 179
 180 /**
 181  * blk_add_timer - Start timeout timer for a single request
 182  * @req:        request that is about to start running.
 183  *
 184  * Notes:
 185  *    Each request has its own timer, and as it is added to the queue, we
 186  *    set up the timer. When the request completes, we cancel the timer.
 187  */
 188 void blk_add_timer(struct request *req)
 189 {
 190         struct request_queue *q = req->q;
 191         unsigned long expiry;
 192
 193         if (!q->rq_timed_out_fn)
 194                 return;
 195
 196         BUG_ON(!list_empty(&req->timeout_list));
 197
 198         /*
 199          * Some LLDs, like scsi, peek at the timeout to prevent a
 200          * command from being retried forever.
 201          */
 202         if (!req->timeout)
 203                 req->timeout = q->rq_timeout;
 204
 205         req->deadline = jiffies + req->timeout;
 206         if (!q->mq_ops)
 207                 list_add_tail(&req->timeout_list, &req->q->timeout_list);
 208
 209         /*
 210          * If the timer isn't already pending or this timeout is earlier
 211          * than an existing one, modify the timer. Round up to next nearest
 212          * second.
 213          */
 214         expiry = blk_rq_timeout(round_jiffies_up(req->deadline));
 215
 216         if (!timer_pending(&q->timeout) ||
 217             time_before(expiry, q->timeout.expires)) {
 218                 unsigned long diff = q->timeout.expires - expiry;
 219
 220                 /*
 221                  * Due to added timer slack to group timers, the timer
 222                  * will often be a little in front of what we asked for.
 223                  * So apply some tolerance here too, otherwise we keep
 224                  * modifying the timer because expires for value X
 225                  * will be X + something.
 226                  */
 227                 if (!timer_pending(&q->timeout) || (diff >= HZ / 2))
 228                         mod_timer(&q->timeout, expiry);
 229         }
 230
 231 }