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Linux/block/blk-timeout.c

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  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                 /* Can we use req->errors here? */
 93                 __blk_complete_request(req);
 94                 break;
 95         case BLK_EH_RESET_TIMER:
 96                 blk_add_timer(req);
 97                 blk_clear_rq_complete(req);
 98                 break;
 99         case BLK_EH_NOT_HANDLED:
100                 /*
101                  * LLD handles this for now but in the future
102                  * we can send a request msg to abort the command
103                  * and we can move more of the generic scsi eh code to
104                  * the blk layer.
105                  */
106                 break;
107         default:
108                 printk(KERN_ERR "block: bad eh return: %d\n", ret);
109                 break;
110         }
111 }
112 
113 static void blk_rq_check_expired(struct request *rq, unsigned long *next_timeout,
114                           unsigned int *next_set)
115 {
116         if (time_after_eq(jiffies, rq->deadline)) {
117                 list_del_init(&rq->timeout_list);
118 
119                 /*
120                  * Check if we raced with end io completion
121                  */
122                 if (!blk_mark_rq_complete(rq))
123                         blk_rq_timed_out(rq);
124         } else if (!*next_set || time_after(*next_timeout, rq->deadline)) {
125                 *next_timeout = rq->deadline;
126                 *next_set = 1;
127         }
128 }
129 
130 void blk_rq_timed_out_timer(unsigned long data)
131 {
132         struct request_queue *q = (struct request_queue *) data;
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 (blk_mark_rq_complete(req))
160                 return;
161         blk_delete_timer(req);
162         if (req->q->mq_ops)
163                 blk_mq_rq_timed_out(req, false);
164         else
165                 blk_rq_timed_out(req);
166 }
167 EXPORT_SYMBOL_GPL(blk_abort_request);
168 
169 unsigned long blk_rq_timeout(unsigned long timeout)
170 {
171         unsigned long maxt;
172 
173         maxt = round_jiffies_up(jiffies + BLK_MAX_TIMEOUT);
174         if (time_after(timeout, maxt))
175                 timeout = maxt;
176 
177         return timeout;
178 }
179 
180 /**
181  * blk_add_timer - Start timeout timer for a single request
182  * @req:        request that is about to start running.
183  *
184  * Notes:
185  *    Each request has its own timer, and as it is added to the queue, we
186  *    set up the timer. When the request completes, we cancel the timer.
187  */
188 void blk_add_timer(struct request *req)
189 {
190         struct request_queue *q = req->q;
191         unsigned long expiry;
192 
193         if (req->cmd_flags & REQ_NO_TIMEOUT)
194                 return;
195 
196         /* blk-mq has its own handler, so we don't need ->rq_timed_out_fn */
197         if (!q->mq_ops && !q->rq_timed_out_fn)
198                 return;
199 
200         BUG_ON(!list_empty(&req->timeout_list));
201 
202         /*
203          * Some LLDs, like scsi, peek at the timeout to prevent a
204          * command from being retried forever.
205          */
206         if (!req->timeout)
207                 req->timeout = q->rq_timeout;
208 
209         req->deadline = jiffies + req->timeout;
210         if (!q->mq_ops)
211                 list_add_tail(&req->timeout_list, &req->q->timeout_list);
212 
213         /*
214          * If the timer isn't already pending or this timeout is earlier
215          * than an existing one, modify the timer. Round up to next nearest
216          * second.
217          */
218         expiry = blk_rq_timeout(round_jiffies_up(req->deadline));
219 
220         if (!timer_pending(&q->timeout) ||
221             time_before(expiry, q->timeout.expires)) {
222                 unsigned long diff = q->timeout.expires - expiry;
223 
224                 /*
225                  * Due to added timer slack to group timers, the timer
226                  * will often be a little in front of what we asked for.
227                  * So apply some tolerance here too, otherwise we keep
228                  * modifying the timer because expires for value X
229                  * will be X + something.
230                  */
231                 if (!timer_pending(&q->timeout) || (diff >= HZ / 2))
232                         mod_timer(&q->timeout, expiry);
233         }
234 
235 }
236 

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