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                 __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         const unsigned long deadline = blk_rq_deadline(rq);
 116
 117         if (time_after_eq(jiffies, deadline)) {
 118                 list_del_init(&rq->timeout_list);
 119
 120                 /*
 121                  * Check if we raced with end io completion
 122                  */
 123                 if (!blk_mark_rq_complete(rq))
 124                         blk_rq_timed_out(rq);
 125         } else if (!*next_set || time_after(*next_timeout, deadline)) {
 126                 *next_timeout = deadline;
 127                 *next_set = 1;
 128         }
 129 }
 130
 131 void blk_timeout_work(struct work_struct *work)
 132 {
 133         struct request_queue *q =
 134                 container_of(work, struct request_queue, timeout_work);
 135         unsigned long flags, next = 0;
 136         struct request *rq, *tmp;
 137         int next_set = 0;
 138
 139         spin_lock_irqsave(q->queue_lock, flags);
 140
 141         list_for_each_entry_safe(rq, tmp, &q->timeout_list, timeout_list)
 142                 blk_rq_check_expired(rq, &next, &next_set);
 143
 144         if (next_set)
 145                 mod_timer(&q->timeout, round_jiffies_up(next));
 146
 147         spin_unlock_irqrestore(q->queue_lock, flags);
 148 }
 149
 150 /**
 151  * blk_abort_request -- Request request recovery for the specified command
 152  * @req:        pointer to the request of interest
 153  *
 154  * This function requests that the block layer start recovery for the
 155  * request by deleting the timer and calling the q's timeout function.
 156  * LLDDs who implement their own error recovery MAY ignore the timeout
 157  * event if they generated blk_abort_req. Must hold queue lock.
 158  */
 159 void blk_abort_request(struct request *req)
 160 {
 161         if (req->q->mq_ops) {
 162                 /*
 163                  * All we need to ensure is that timeout scan takes place
 164                  * immediately and that scan sees the new timeout value.
 165                  * No need for fancy synchronizations.
 166                  */
 167                 blk_rq_set_deadline(req, jiffies);
 168                 mod_timer(&req->q->timeout, 0);
 169         } else {
 170                 if (blk_mark_rq_complete(req))
 171                         return;
 172                 blk_delete_timer(req);
 173                 blk_rq_timed_out(req);
 174         }
 175 }
 176 EXPORT_SYMBOL_GPL(blk_abort_request);
 177
 178 unsigned long blk_rq_timeout(unsigned long timeout)
 179 {
 180         unsigned long maxt;
 181
 182         maxt = round_jiffies_up(jiffies + BLK_MAX_TIMEOUT);
 183         if (time_after(timeout, maxt))
 184                 timeout = maxt;
 185
 186         return timeout;
 187 }
 188
 189 /**
 190  * blk_add_timer - Start timeout timer for a single request
 191  * @req:        request that is about to start running.
 192  *
 193  * Notes:
 194  *    Each request has its own timer, and as it is added to the queue, we
 195  *    set up the timer. When the request completes, we cancel the timer.
 196  */
 197 void blk_add_timer(struct request *req)
 198 {
 199         struct request_queue *q = req->q;
 200         unsigned long expiry;
 201
 202         if (!q->mq_ops)
 203                 lockdep_assert_held(q->queue_lock);
 204
 205         /* blk-mq has its own handler, so we don't need ->rq_timed_out_fn */
 206         if (!q->mq_ops && !q->rq_timed_out_fn)
 207                 return;
 208
 209         BUG_ON(!list_empty(&req->timeout_list));
 210
 211         /*
 212          * Some LLDs, like scsi, peek at the timeout to prevent a
 213          * command from being retried forever.
 214          */
 215         if (!req->timeout)
 216                 req->timeout = q->rq_timeout;
 217
 218         blk_rq_set_deadline(req, jiffies + req->timeout);
 219         req->rq_flags &= ~RQF_MQ_TIMEOUT_EXPIRED;
 220
 221         /*
 222          * Only the non-mq case needs to add the request to a protected list.
 223          * For the mq case we simply scan the tag map.
 224          */
 225         if (!q->mq_ops)
 226                 list_add_tail(&req->timeout_list, &req->q->timeout_list);
 227
 228         /*
 229          * If the timer isn't already pending or this timeout is earlier
 230          * than an existing one, modify the timer. Round up to next nearest
 231          * second.
 232          */
 233         expiry = blk_rq_timeout(round_jiffies_up(blk_rq_deadline(req)));
 234
 235         if (!timer_pending(&q->timeout) ||
 236             time_before(expiry, q->timeout.expires)) {
 237                 unsigned long diff = q->timeout.expires - expiry;
 238
 239                 /*
 240                  * Due to added timer slack to group timers, the timer
 241                  * will often be a little in front of what we asked for.
 242                  * So apply some tolerance here too, otherwise we keep
 243                  * modifying the timer because expires for value X
 244                  * will be X + something.
 245                  */
 246                 if (!timer_pending(&q->timeout) || (diff >= HZ / 2))
 247                         mod_timer(&q->timeout, expiry);
 248         }
 249
 250 }