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 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                 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                 /* Can we use req->errors here? */
  92                 __blk_complete_request(req);
  93                 break;
  94         case BLK_EH_RESET_TIMER:
  95                 blk_add_timer(req);
  96                 blk_clear_rq_complete(req);
  97                 break;
  98         case BLK_EH_NOT_HANDLED:
  99                 /*
 100                  * LLD handles this for now but in the future
 101                  * we can send a request msg to abort the command
 102                  * and we can move more of the generic scsi eh code to
 103                  * the blk layer.
 104                  */
 105                 break;
 106         default:
 107                 printk(KERN_ERR "block: bad eh return: %d\n", ret);
 108                 break;
 109         }
 110 }
 111
 112 static void blk_rq_check_expired(struct request *rq, unsigned long *next_timeout,
 113                           unsigned int *next_set)
 114 {
 115         if (time_after_eq(jiffies, rq->deadline)) {
 116                 list_del_init(&rq->timeout_list);
 117
 118                 /*
 119                  * Check if we raced with end io completion
 120                  */
 121                 if (!blk_mark_rq_complete(rq))
 122                         blk_rq_timed_out(rq);
 123         } else if (!*next_set || time_after(*next_timeout, rq->deadline)) {
 124                 *next_timeout = rq->deadline;
 125                 *next_set = 1;
 126         }
 127 }
 128
 129 void blk_rq_timed_out_timer(unsigned long data)
 130 {
 131         struct request_queue *q = (struct request_queue *) data;
 132         unsigned long flags, next = 0;
 133         struct request *rq, *tmp;
 134         int next_set = 0;
 135
 136         spin_lock_irqsave(q->queue_lock, flags);
 137
 138         list_for_each_entry_safe(rq, tmp, &q->timeout_list, timeout_list)
 139                 blk_rq_check_expired(rq, &next, &next_set);
 140
 141         if (next_set)
 142                 mod_timer(&q->timeout, round_jiffies_up(next));
 143
 144         spin_unlock_irqrestore(q->queue_lock, flags);
 145 }
 146
 147 /**
 148  * blk_abort_request -- Request request recovery for the specified command
 149  * @req:        pointer to the request of interest
 150  *
 151  * This function requests that the block layer start recovery for the
 152  * request by deleting the timer and calling the q's timeout function.
 153  * LLDDs who implement their own error recovery MAY ignore the timeout
 154  * event if they generated blk_abort_req. Must hold queue lock.
 155  */
 156 void blk_abort_request(struct request *req)
 157 {
 158         if (blk_mark_rq_complete(req))
 159                 return;
 160         blk_delete_timer(req);
 161         blk_rq_timed_out(req);
 162 }
 163 EXPORT_SYMBOL_GPL(blk_abort_request);
 164
 165 unsigned long blk_rq_timeout(unsigned long timeout)
 166 {
 167         unsigned long maxt;
 168
 169         maxt = round_jiffies_up(jiffies + BLK_MAX_TIMEOUT);
 170         if (time_after(timeout, maxt))
 171                 timeout = maxt;
 172
 173         return timeout;
 174 }
 175
 176 /**
 177  * blk_add_timer - Start timeout timer for a single request
 178  * @req:        request that is about to start running.
 179  *
 180  * Notes:
 181  *    Each request has its own timer, and as it is added to the queue, we
 182  *    set up the timer. When the request completes, we cancel the timer.
 183  */
 184 void blk_add_timer(struct request *req)
 185 {
 186         struct request_queue *q = req->q;
 187         unsigned long expiry;
 188
 189         /* blk-mq has its own handler, so we don't need ->rq_timed_out_fn */
 190         if (!q->mq_ops && !q->rq_timed_out_fn)
 191                 return;
 192
 193         BUG_ON(!list_empty(&req->timeout_list));
 194
 195         /*
 196          * Some LLDs, like scsi, peek at the timeout to prevent a
 197          * command from being retried forever.
 198          */
 199         if (!req->timeout)
 200                 req->timeout = q->rq_timeout;
 201
 202         req->deadline = jiffies + req->timeout;
 203         if (!q->mq_ops)
 204                 list_add_tail(&req->timeout_list, &req->q->timeout_list);
 205
 206         /*
 207          * If the timer isn't already pending or this timeout is earlier
 208          * than an existing one, modify the timer. Round up to next nearest
 209          * second.
 210          */
 211         expiry = blk_rq_timeout(round_jiffies_up(req->deadline));
 212
 213         if (!timer_pending(&q->timeout) ||
 214             time_before(expiry, q->timeout.expires)) {
 215                 unsigned long diff = q->timeout.expires - expiry;
 216
 217                 /*
 218                  * Due to added timer slack to group timers, the timer
 219                  * will often be a little in front of what we asked for.
 220                  * So apply some tolerance here too, otherwise we keep
 221                  * modifying the timer because expires for value X
 222                  * will be X + something.
 223                  */
 224                 if (!timer_pending(&q->timeout) || (diff >= HZ / 2))
 225                         mod_timer(&q->timeout, expiry);
 226         }
 227
 228 }