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
14static DECLARE_FAULT_ATTR(fail_io_timeout);
15
16static 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
22int 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
30static 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
38late_initcall(fail_io_timeout_debugfs);
39
40ssize_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
49ssize_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 */
78void blk_delete_timer(struct request *req)
79{
80	list_del_init(&req->timeout_list);
81}
82
83static 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
113static 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
130void 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 */
157void 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}
167EXPORT_SYMBOL_GPL(blk_abort_request);
168
169unsigned 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 */
188void 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