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                 if (val)
  61                         blk_queue_flag_set(QUEUE_FLAG_FAIL_IO, q);
  62                 else
  63                         blk_queue_flag_clear(QUEUE_FLAG_FAIL_IO, q);
  64         }
  65
  66         return count;
  67 }
  68
  69 #endif /* CONFIG_FAIL_IO_TIMEOUT */
  70
  71 /*
  72  * blk_delete_timer - Delete/cancel timer for a given function.
  73  * @req:        request that we are canceling timer for
  74  *
  75  */
  76 void blk_delete_timer(struct request *req)
  77 {
  78         list_del_init(&req->timeout_list);
  79 }
  80
  81 static void blk_rq_timed_out(struct request *req)
  82 {
  83         struct request_queue *q = req->q;
  84         enum blk_eh_timer_return ret = BLK_EH_RESET_TIMER;
  85
  86         if (q->rq_timed_out_fn)
  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 static void blk_rq_check_expired(struct request *rq, unsigned long *next_timeout,
 111                           unsigned int *next_set)
 112 {
 113         const unsigned long deadline = blk_rq_deadline(rq);
 114
 115         if (time_after_eq(jiffies, 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, deadline)) {
 124                 *next_timeout = deadline;
 125                 *next_set = 1;
 126         }
 127 }
 128
 129 void blk_timeout_work(struct work_struct *work)
 130 {
 131         struct request_queue *q =
 132                 container_of(work, struct request_queue, timeout_work);
 133         unsigned long flags, next = 0;
 134         struct request *rq, *tmp;
 135         int next_set = 0;
 136
 137         spin_lock_irqsave(q->queue_lock, flags);
 138
 139         list_for_each_entry_safe(rq, tmp, &q->timeout_list, timeout_list)
 140                 blk_rq_check_expired(rq, &next, &next_set);
 141
 142         if (next_set)
 143                 mod_timer(&q->timeout, round_jiffies_up(next));
 144
 145         spin_unlock_irqrestore(q->queue_lock, flags);
 146 }
 147
 148 /**
 149  * blk_abort_request -- Request request recovery for the specified command
 150  * @req:        pointer to the request of interest
 151  *
 152  * This function requests that the block layer start recovery for the
 153  * request by deleting the timer and calling the q's timeout function.
 154  * LLDDs who implement their own error recovery MAY ignore the timeout
 155  * event if they generated blk_abort_req. Must hold queue lock.
 156  */
 157 void blk_abort_request(struct request *req)
 158 {
 159         if (req->q->mq_ops) {
 160                 /*
 161                  * All we need to ensure is that timeout scan takes place
 162                  * immediately and that scan sees the new timeout value.
 163                  * No need for fancy synchronizations.
 164                  */
 165                 blk_rq_set_deadline(req, jiffies);
 166                 kblockd_schedule_work(&req->q->timeout_work);
 167         } else {
 168                 if (blk_mark_rq_complete(req))
 169                         return;
 170                 blk_delete_timer(req);
 171                 blk_rq_timed_out(req);
 172         }
 173 }
 174 EXPORT_SYMBOL_GPL(blk_abort_request);
 175
 176 unsigned long blk_rq_timeout(unsigned long timeout)
 177 {
 178         unsigned long maxt;
 179
 180         maxt = round_jiffies_up(jiffies + BLK_MAX_TIMEOUT);
 181         if (time_after(timeout, maxt))
 182                 timeout = maxt;
 183
 184         return timeout;
 185 }
 186
 187 /**
 188  * blk_add_timer - Start timeout timer for a single request
 189  * @req:        request that is about to start running.
 190  *
 191  * Notes:
 192  *    Each request has its own timer, and as it is added to the queue, we
 193  *    set up the timer. When the request completes, we cancel the timer.
 194  */
 195 void blk_add_timer(struct request *req)
 196 {
 197         struct request_queue *q = req->q;
 198         unsigned long expiry;
 199
 200         if (!q->mq_ops)
 201                 lockdep_assert_held(q->queue_lock);
 202
 203         /* blk-mq has its own handler, so we don't need ->rq_timed_out_fn */
 204         if (!q->mq_ops && !q->rq_timed_out_fn)
 205                 return;
 206
 207         BUG_ON(!list_empty(&req->timeout_list));
 208
 209         /*
 210          * Some LLDs, like scsi, peek at the timeout to prevent a
 211          * command from being retried forever.
 212          */
 213         if (!req->timeout)
 214                 req->timeout = q->rq_timeout;
 215
 216         blk_rq_set_deadline(req, jiffies + req->timeout);
 217         req->rq_flags &= ~RQF_MQ_TIMEOUT_EXPIRED;
 218
 219         /*
 220          * Only the non-mq case needs to add the request to a protected list.
 221          * For the mq case we simply scan the tag map.
 222          */
 223         if (!q->mq_ops)
 224                 list_add_tail(&req->timeout_list, &req->q->timeout_list);
 225
 226         /*
 227          * If the timer isn't already pending or this timeout is earlier
 228          * than an existing one, modify the timer. Round up to next nearest
 229          * second.
 230          */
 231         expiry = blk_rq_timeout(round_jiffies_up(blk_rq_deadline(req)));
 232
 233         if (!timer_pending(&q->timeout) ||
 234             time_before(expiry, q->timeout.expires)) {
 235                 unsigned long diff = q->timeout.expires - expiry;
 236
 237                 /*
 238                  * Due to added timer slack to group timers, the timer
 239                  * will often be a little in front of what we asked for.
 240                  * So apply some tolerance here too, otherwise we keep
 241                  * modifying the timer because expires for value X
 242                  * will be X + something.
 243                  */
 244                 if (!timer_pending(&q->timeout) || (diff >= HZ / 2))
 245                         mod_timer(&q->timeout, expiry);
 246         }
 247
 248 }