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
  11 #ifdef CONFIG_FAIL_IO_TIMEOUT
  12
  13 static DECLARE_FAULT_ATTR(fail_io_timeout);
  14
  15 static 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
  21 int 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
  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 IS_ERR(dir) ? PTR_ERR(dir) : 0;
  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                 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  */
  77 void blk_delete_timer(struct request *req)
  78 {
  79         list_del_init(&req->timeout_list);
  80 }
  81
  82 static void blk_rq_timed_out(struct request *req)
  83 {
  84         struct request_queue *q = req->q;
  85         enum blk_eh_timer_return ret;
  86
  87         ret = q->rq_timed_out_fn(req);
  88         switch (ret) {
  89         case BLK_EH_HANDLED:
  90                 __blk_complete_request(req);
  91                 break;
  92         case BLK_EH_RESET_TIMER:
  93                 blk_add_timer(req);
  94                 blk_clear_rq_complete(req);
  95                 break;
  96         case BLK_EH_NOT_HANDLED:
  97                 /*
  98                  * LLD handles this for now but in the future
  99                  * we can send a request msg to abort the command
 100                  * and we can move more of the generic scsi eh code to
 101                  * the blk layer.
 102                  */
 103                 break;
 104         default:
 105                 printk(KERN_ERR "block: bad eh return: %d\n", ret);
 106                 break;
 107         }
 108 }
 109
 110 void blk_rq_timed_out_timer(unsigned long data)
 111 {
 112         struct request_queue *q = (struct request_queue *) data;
 113         unsigned long flags, next = 0;
 114         struct request *rq, *tmp;
 115         int next_set = 0;
 116
 117         spin_lock_irqsave(q->queue_lock, flags);
 118
 119         list_for_each_entry_safe(rq, tmp, &q->timeout_list, timeout_list) {
 120                 if (time_after_eq(jiffies, rq->deadline)) {
 121                         list_del_init(&rq->timeout_list);
 122
 123                         /*
 124                          * Check if we raced with end io completion
 125                          */
 126                         if (blk_mark_rq_complete(rq))
 127                                 continue;
 128                         blk_rq_timed_out(rq);
 129                 } else if (!next_set || time_after(next, rq->deadline)) {
 130                         next = rq->deadline;
 131                         next_set = 1;
 132                 }
 133         }
 134
 135         if (next_set)
 136                 mod_timer(&q->timeout, round_jiffies_up(next));
 137
 138         spin_unlock_irqrestore(q->queue_lock, flags);
 139 }
 140
 141 /**
 142  * blk_abort_request -- Request request recovery for the specified command
 143  * @req:        pointer to the request of interest
 144  *
 145  * This function requests that the block layer start recovery for the
 146  * request by deleting the timer and calling the q's timeout function.
 147  * LLDDs who implement their own error recovery MAY ignore the timeout
 148  * event if they generated blk_abort_req. Must hold queue lock.
 149  */
 150 void blk_abort_request(struct request *req)
 151 {
 152         if (blk_mark_rq_complete(req))
 153                 return;
 154         blk_delete_timer(req);
 155         blk_rq_timed_out(req);
 156 }
 157 EXPORT_SYMBOL_GPL(blk_abort_request);
 158
 159 /**
 160  * blk_add_timer - Start timeout timer for a single request
 161  * @req:        request that is about to start running.
 162  *
 163  * Notes:
 164  *    Each request has its own timer, and as it is added to the queue, we
 165  *    set up the timer. When the request completes, we cancel the timer.
 166  */
 167 void blk_add_timer(struct request *req)
 168 {
 169         struct request_queue *q = req->q;
 170         unsigned long expiry;
 171
 172         if (!q->rq_timed_out_fn)
 173                 return;
 174
 175         BUG_ON(!list_empty(&req->timeout_list));
 176
 177         /*
 178          * Some LLDs, like scsi, peek at the timeout to prevent a
 179          * command from being retried forever.
 180          */
 181         if (!req->timeout)
 182                 req->timeout = q->rq_timeout;
 183
 184         req->deadline = jiffies + req->timeout;
 185         list_add_tail(&req->timeout_list, &q->timeout_list);
 186
 187         /*
 188          * If the timer isn't already pending or this timeout is earlier
 189          * than an existing one, modify the timer. Round up to next nearest
 190          * second.
 191          */
 192         expiry = round_jiffies_up(req->deadline);
 193
 194         if (!timer_pending(&q->timeout) ||
 195             time_before(expiry, q->timeout.expires))
 196                 mod_timer(&q->timeout, expiry);
 197 }
 198