path: root/block/blk-timeout.c (plain)
blob: 220661a50f58557df475a550058d68ee48bf1497

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	spin_lock_irqsave(q->queue_lock, flags);
139
140	list_for_each_entry_safe(rq, tmp, &q->timeout_list, timeout_list)
141	blk_rq_check_expired(rq, &next, &next_set);
142
143	if (next_set)
144	mod_timer(&q->timeout, round_jiffies_up(next));
145
146	spin_unlock_irqrestore(q->queue_lock, flags);
147	}
148
149	/**
150	* blk_abort_request -- Request request recovery for the specified command
151	* @req: pointer to the request of interest
152	*
153	* This function requests that the block layer start recovery for the
154	* request by deleting the timer and calling the q's timeout function.
155	* LLDDs who implement their own error recovery MAY ignore the timeout
156	* event if they generated blk_abort_req. Must hold queue lock.
157	*/
158	void blk_abort_request(struct request *req)
159	{
160	if (blk_mark_rq_complete(req))
161	return;
162
163	if (req->q->mq_ops) {
164	blk_mq_rq_timed_out(req, false);
165	} else {
166	blk_delete_timer(req);
167	blk_rq_timed_out(req);
168	}
169	}
170	EXPORT_SYMBOL_GPL(blk_abort_request);
171
172	unsigned long blk_rq_timeout(unsigned long timeout)
173	{
174	unsigned long maxt;
175
176	maxt = round_jiffies_up(jiffies + BLK_MAX_TIMEOUT);
177	if (time_after(timeout, maxt))
178	timeout = maxt;
179
180	return timeout;
181	}
182
183	/**
184	* blk_add_timer - Start timeout timer for a single request
185	* @req: request that is about to start running.
186	*
187	* Notes:
188	* Each request has its own timer, and as it is added to the queue, we
189	* set up the timer. When the request completes, we cancel the timer.
190	* Queue lock must be held for the non-mq case, mq case doesn't care.
191	*/
192	void blk_add_timer(struct request *req)
193	{
194	struct request_queue *q = req->q;
195	unsigned long expiry;
196
197	/* blk-mq has its own handler, so we don't need ->rq_timed_out_fn */
198	if (!q->mq_ops && !q->rq_timed_out_fn)
199	return;
200
201	BUG_ON(!list_empty(&req->timeout_list));
202
203	/*
204	* Some LLDs, like scsi, peek at the timeout to prevent a
205	* command from being retried forever.
206	*/
207	if (!req->timeout)
208	req->timeout = q->rq_timeout;
209
210	req->deadline = jiffies + req->timeout;
211
212	/*
213	* Only the non-mq case needs to add the request to a protected list.
214	* For the mq case we simply scan the tag map.
215	*/
216	if (!q->mq_ops)
217	list_add_tail(&req->timeout_list, &req->q->timeout_list);
218
219	/*
220	* If the timer isn't already pending or this timeout is earlier
221	* than an existing one, modify the timer. Round up to next nearest
222	* second.
223	*/
224	expiry = blk_rq_timeout(round_jiffies_up(req->deadline));
225
226	if (!timer_pending(&q->timeout) ||
227	time_before(expiry, q->timeout.expires)) {
228	unsigned long diff = q->timeout.expires - expiry;
229
230	/*
231	* Due to added timer slack to group timers, the timer
232	* will often be a little in front of what we asked for.
233	* So apply some tolerance here too, otherwise we keep
234	* modifying the timer because expires for value X
235	* will be X + something.
236	*/
237	if (!timer_pending(&q->timeout) || (diff >= HZ / 2))
238	mod_timer(&q->timeout, expiry);
239	}
240
241	}
242