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_RESET_TIMER:
  90                 blk_add_timer(req);
  91                 blk_clear_rq_complete(req);
  92                 break;
  93         case BLK_EH_DONE:
  94                 /*
  95                  * LLD handles this for now but in the future
  96                  * we can send a request msg to abort the command
  97                  * and we can move more of the generic scsi eh code to
  98                  * the blk layer.
  99                  */
 100                 break;
 101         default:
 102                 printk(KERN_ERR "block: bad eh return: %d\n", ret);
 103                 break;
 104         }
 105 }
 106
 107 static void blk_rq_check_expired(struct request *rq, unsigned long *next_timeout,
 108                           unsigned int *next_set)
 109 {
 110         const unsigned long deadline = blk_rq_deadline(rq);
 111
 112         if (time_after_eq(jiffies, deadline)) {
 113                 list_del_init(&rq->timeout_list);
 114
 115                 /*
 116                  * Check if we raced with end io completion
 117                  */
 118                 if (!blk_mark_rq_complete(rq))
 119                         blk_rq_timed_out(rq);
 120         } else if (!*next_set || time_after(*next_timeout, deadline)) {
 121                 *next_timeout = deadline;
 122                 *next_set = 1;
 123         }
 124 }
 125
 126 void blk_timeout_work(struct work_struct *work)
 127 {
 128         struct request_queue *q =
 129                 container_of(work, struct request_queue, timeout_work);
 130         unsigned long flags, next = 0;
 131         struct request *rq, *tmp;
 132         int next_set = 0;
 133
 134         spin_lock_irqsave(q->queue_lock, flags);
 135
 136         list_for_each_entry_safe(rq, tmp, &q->timeout_list, timeout_list)
 137                 blk_rq_check_expired(rq, &next, &next_set);
 138
 139         if (next_set)
 140                 mod_timer(&q->timeout, round_jiffies_up(next));
 141
 142         spin_unlock_irqrestore(q->queue_lock, flags);
 143 }
 144
 145 /**
 146  * blk_abort_request -- Request request recovery for the specified command
 147  * @req:        pointer to the request of interest
 148  *
 149  * This function requests that the block layer start recovery for the
 150  * request by deleting the timer and calling the q's timeout function.
 151  * LLDDs who implement their own error recovery MAY ignore the timeout
 152  * event if they generated blk_abort_req. Must hold queue lock.
 153  */
 154 void blk_abort_request(struct request *req)
 155 {
 156         if (req->q->mq_ops) {
 157                 /*
 158                  * All we need to ensure is that timeout scan takes place
 159                  * immediately and that scan sees the new timeout value.
 160                  * No need for fancy synchronizations.
 161                  */
 162                 blk_rq_set_deadline(req, jiffies);
 163                 kblockd_schedule_work(&req->q->timeout_work);
 164         } else {
 165                 if (blk_mark_rq_complete(req))
 166                         return;
 167                 blk_delete_timer(req);
 168                 blk_rq_timed_out(req);
 169         }
 170 }
 171 EXPORT_SYMBOL_GPL(blk_abort_request);
 172
 173 unsigned long blk_rq_timeout(unsigned long timeout)
 174 {
 175         unsigned long maxt;
 176
 177         maxt = round_jiffies_up(jiffies + BLK_MAX_TIMEOUT);
 178         if (time_after(timeout, maxt))
 179                 timeout = maxt;
 180
 181         return timeout;
 182 }
 183
 184 /**
 185  * blk_add_timer - Start timeout timer for a single request
 186  * @req:        request that is about to start running.
 187  *
 188  * Notes:
 189  *    Each request has its own timer, and as it is added to the queue, we
 190  *    set up the timer. When the request completes, we cancel the timer.
 191  */
 192 void blk_add_timer(struct request *req)
 193 {
 194         struct request_queue *q = req->q;
 195         unsigned long expiry;
 196
 197         if (!q->mq_ops)
 198                 lockdep_assert_held(q->queue_lock);
 199
 200         /* blk-mq has its own handler, so we don't need ->rq_timed_out_fn */
 201         if (!q->mq_ops && !q->rq_timed_out_fn)
 202                 return;
 203
 204         BUG_ON(!list_empty(&req->timeout_list));
 205
 206         /*
 207          * Some LLDs, like scsi, peek at the timeout to prevent a
 208          * command from being retried forever.
 209          */
 210         if (!req->timeout)
 211                 req->timeout = q->rq_timeout;
 212
 213         req->rq_flags &= ~RQF_TIMED_OUT;
 214         blk_rq_set_deadline(req, jiffies + req->timeout);
 215
 216         /*
 217          * Only the non-mq case needs to add the request to a protected list.
 218          * For the mq case we simply scan the tag map.
 219          */
 220         if (!q->mq_ops)
 221                 list_add_tail(&req->timeout_list, &req->q->timeout_list);
 222
 223         /*
 224          * If the timer isn't already pending or this timeout is earlier
 225          * than an existing one, modify the timer. Round up to next nearest
 226          * second.
 227          */
 228         expiry = blk_rq_timeout(round_jiffies_up(blk_rq_deadline(req)));
 229
 230         if (!timer_pending(&q->timeout) ||
 231             time_before(expiry, q->timeout.expires)) {
 232                 unsigned long diff = q->timeout.expires - expiry;
 233
 234                 /*
 235                  * Due to added timer slack to group timers, the timer
 236                  * will often be a little in front of what we asked for.
 237                  * So apply some tolerance here too, otherwise we keep
 238                  * modifying the timer because expires for value X
 239                  * will be X + something.
 240                  */
 241                 if (!timer_pending(&q->timeout) || (diff >= HZ / 2))
 242                         mod_timer(&q->timeout, expiry);
 243         }
 244
 245 }