block: optimizations in blk_rq_timed_out_timer()
[linux-2.6.git] / 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
11 #ifdef CONFIG_FAIL_IO_TIMEOUT
12
13 static DECLARE_FAULT_ATTR(fail_io_timeout);
14
15 static int __init setup_fail_io_timeout(char *str)
16 {
17         return setup_fault_attr(&fail_io_timeout, str);
18 }
19 __setup("fail_io_timeout=", setup_fail_io_timeout);
20
21 int blk_should_fake_timeout(struct request_queue *q)
22 {
23         if (!test_bit(QUEUE_FLAG_FAIL_IO, &q->queue_flags))
24                 return 0;
25
26         return should_fail(&fail_io_timeout, 1);
27 }
28
29 static int __init fail_io_timeout_debugfs(void)
30 {
31         return init_fault_attr_dentries(&fail_io_timeout, "fail_io_timeout");
32 }
33
34 late_initcall(fail_io_timeout_debugfs);
35
36 ssize_t part_timeout_show(struct device *dev, struct device_attribute *attr,
37                           char *buf)
38 {
39         struct gendisk *disk = dev_to_disk(dev);
40         int set = test_bit(QUEUE_FLAG_FAIL_IO, &disk->queue->queue_flags);
41
42         return sprintf(buf, "%d\n", set != 0);
43 }
44
45 ssize_t part_timeout_store(struct device *dev, struct device_attribute *attr,
46                            const char *buf, size_t count)
47 {
48         struct gendisk *disk = dev_to_disk(dev);
49         int val;
50
51         if (count) {
52                 struct request_queue *q = disk->queue;
53                 char *p = (char *) buf;
54
55                 val = simple_strtoul(p, &p, 10);
56                 spin_lock_irq(q->queue_lock);
57                 if (val)
58                         queue_flag_set(QUEUE_FLAG_FAIL_IO, q);
59                 else
60                         queue_flag_clear(QUEUE_FLAG_FAIL_IO, q);
61                 spin_unlock_irq(q->queue_lock);
62         }
63
64         return count;
65 }
66
67 #endif /* CONFIG_FAIL_IO_TIMEOUT */
68
69 /*
70  * blk_delete_timer - Delete/cancel timer for a given function.
71  * @req:        request that we are canceling timer for
72  *
73  */
74 void blk_delete_timer(struct request *req)
75 {
76         struct request_queue *q = req->q;
77
78         list_del_init(&req->timeout_list);
79         if (list_empty(&q->timeout_list))
80                 del_timer(&q->timeout);
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;
87
88         ret = q->rq_timed_out_fn(req);
89         switch (ret) {
90         case BLK_EH_HANDLED:
91                 __blk_complete_request(req);
92                 break;
93         case BLK_EH_RESET_TIMER:
94                 blk_clear_rq_complete(req);
95                 blk_add_timer(req);
96                 break;
97         case BLK_EH_NOT_HANDLED:
98                 /*
99                  * LLD handles this for now but in the future
100                  * we can send a request msg to abort the command
101                  * and we can move more of the generic scsi eh code to
102                  * the blk layer.
103                  */
104                 break;
105         default:
106                 printk(KERN_ERR "block: bad eh return: %d\n", ret);
107                 break;
108         }
109 }
110
111 void blk_rq_timed_out_timer(unsigned long data)
112 {
113         struct request_queue *q = (struct request_queue *) data;
114         unsigned long flags, next = 0;
115         struct request *rq, *tmp;
116
117         spin_lock_irqsave(q->queue_lock, flags);
118
119         list_for_each_entry_safe(rq, tmp, &q->timeout_list, timeout_list) {
120                 if (time_after_eq(jiffies, rq->deadline)) {
121                         list_del_init(&rq->timeout_list);
122
123                         /*
124                          * Check if we raced with end io completion
125                          */
126                         if (blk_mark_rq_complete(rq))
127                                 continue;
128                         blk_rq_timed_out(rq);
129                 } else {
130                         if (!next || time_after(next, rq->deadline))
131                                 next = rq->deadline;
132                 }
133         }
134
135         if (next_set && !list_empty(&q->timeout_list))
136                 mod_timer(&q->timeout, round_jiffies_up(next));
137
138         spin_unlock_irqrestore(q->queue_lock, flags);
139 }
140
141 /**
142  * blk_abort_request -- Request request recovery for the specified command
143  * @req:        pointer to the request of interest
144  *
145  * This function requests that the block layer start recovery for the
146  * request by deleting the timer and calling the q's timeout function.
147  * LLDDs who implement their own error recovery MAY ignore the timeout
148  * event if they generated blk_abort_req. Must hold queue lock.
149  */
150 void blk_abort_request(struct request *req)
151 {
152         if (blk_mark_rq_complete(req))
153                 return;
154         blk_delete_timer(req);
155         blk_rq_timed_out(req);
156 }
157 EXPORT_SYMBOL_GPL(blk_abort_request);
158
159 /**
160  * blk_add_timer - Start timeout timer for a single request
161  * @req:        request that is about to start running.
162  *
163  * Notes:
164  *    Each request has its own timer, and as it is added to the queue, we
165  *    set up the timer. When the request completes, we cancel the timer.
166  */
167 void blk_add_timer(struct request *req)
168 {
169         struct request_queue *q = req->q;
170         unsigned long expiry;
171
172         if (!q->rq_timed_out_fn)
173                 return;
174
175         BUG_ON(!list_empty(&req->timeout_list));
176         BUG_ON(test_bit(REQ_ATOM_COMPLETE, &req->atomic_flags));
177
178         if (req->timeout)
179                 req->deadline = jiffies + req->timeout;
180         else {
181                 req->deadline = jiffies + q->rq_timeout;
182                 /*
183                  * Some LLDs, like scsi, peek at the timeout to prevent
184                  * a command from being retried forever.
185                  */
186                 req->timeout = q->rq_timeout;
187         }
188         list_add_tail(&req->timeout_list, &q->timeout_list);
189
190         /*
191          * If the timer isn't already pending or this timeout is earlier
192          * than an existing one, modify the timer. Round up to next nearest
193          * second.
194          */
195         expiry = round_jiffies_up(req->deadline);
196
197         if (!timer_pending(&q->timeout) ||
198             time_before(expiry, q->timeout.expires))
199                 mod_timer(&q->timeout, expiry);
200 }
201
202 /**
203  * blk_abort_queue -- Abort all request on given queue
204  * @queue:      pointer to queue
205  *
206  */
207 void blk_abort_queue(struct request_queue *q)
208 {
209         unsigned long flags;
210         struct request *rq, *tmp;
211
212         spin_lock_irqsave(q->queue_lock, flags);
213
214         elv_abort_queue(q);
215
216         list_for_each_entry_safe(rq, tmp, &q->timeout_list, timeout_list)
217                 blk_abort_request(rq);
218
219         spin_unlock_irqrestore(q->queue_lock, flags);
220
221 }
222 EXPORT_SYMBOL_GPL(blk_abort_queue);