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 = 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
 111 void 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  */
 151 void 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 }
 158 EXPORT_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  */
 168 void 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