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Linux/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                 /* 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_timeout_work(struct work_struct *work)
131 {
132         struct request_queue *q =
133                 container_of(work, struct request_queue, timeout_work);
134         unsigned long flags, next = 0;
135         struct request *rq, *tmp;
136         int next_set = 0;
137 
138         if (blk_queue_enter(q, true))
139                 return;
140         spin_lock_irqsave(q->queue_lock, flags);
141 
142         list_for_each_entry_safe(rq, tmp, &q->timeout_list, timeout_list)
143                 blk_rq_check_expired(rq, &next, &next_set);
144 
145         if (next_set)
146                 mod_timer(&q->timeout, round_jiffies_up(next));
147 
148         spin_unlock_irqrestore(q->queue_lock, flags);
149         blk_queue_exit(q);
150 }
151 
152 /**
153  * blk_abort_request -- Request request recovery for the specified command
154  * @req:        pointer to the request of interest
155  *
156  * This function requests that the block layer start recovery for the
157  * request by deleting the timer and calling the q's timeout function.
158  * LLDDs who implement their own error recovery MAY ignore the timeout
159  * event if they generated blk_abort_req. Must hold queue lock.
160  */
161 void blk_abort_request(struct request *req)
162 {
163         if (blk_mark_rq_complete(req))
164                 return;
165 
166         if (req->q->mq_ops) {
167                 blk_mq_rq_timed_out(req, false);
168         } else {
169                 blk_delete_timer(req);
170                 blk_rq_timed_out(req);
171         }
172 }
173 EXPORT_SYMBOL_GPL(blk_abort_request);
174 
175 unsigned long blk_rq_timeout(unsigned long timeout)
176 {
177         unsigned long maxt;
178 
179         maxt = round_jiffies_up(jiffies + BLK_MAX_TIMEOUT);
180         if (time_after(timeout, maxt))
181                 timeout = maxt;
182 
183         return timeout;
184 }
185 
186 /**
187  * blk_add_timer - Start timeout timer for a single request
188  * @req:        request that is about to start running.
189  *
190  * Notes:
191  *    Each request has its own timer, and as it is added to the queue, we
192  *    set up the timer. When the request completes, we cancel the timer.
193  *    Queue lock must be held for the non-mq case, mq case doesn't care.
194  */
195 void blk_add_timer(struct request *req)
196 {
197         struct request_queue *q = req->q;
198         unsigned long expiry;
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->deadline = jiffies + req->timeout;
214 
215         /*
216          * Only the non-mq case needs to add the request to a protected list.
217          * For the mq case we simply scan the tag map.
218          */
219         if (!q->mq_ops)
220                 list_add_tail(&req->timeout_list, &req->q->timeout_list);
221 
222         /*
223          * If the timer isn't already pending or this timeout is earlier
224          * than an existing one, modify the timer. Round up to next nearest
225          * second.
226          */
227         expiry = blk_rq_timeout(round_jiffies_up(req->deadline));
228 
229         if (!timer_pending(&q->timeout) ||
230             time_before(expiry, q->timeout.expires)) {
231                 unsigned long diff = q->timeout.expires - expiry;
232 
233                 /*
234                  * Due to added timer slack to group timers, the timer
235                  * will often be a little in front of what we asked for.
236                  * So apply some tolerance here too, otherwise we keep
237                  * modifying the timer because expires for value X
238                  * will be X + something.
239                  */
240                 if (!timer_pending(&q->timeout) || (diff >= HZ / 2))
241                         mod_timer(&q->timeout, expiry);
242         }
243 
244 }
245 

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