xref: /openbmc/linux/block/blk-timeout.c (revision b830f94f)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Functions related to generic timeout handling of requests.
4  */
5 #include <linux/kernel.h>
6 #include <linux/module.h>
7 #include <linux/blkdev.h>
8 #include <linux/fault-inject.h>
9 
10 #include "blk.h"
11 #include "blk-mq.h"
12 
13 #ifdef CONFIG_FAIL_IO_TIMEOUT
14 
15 static DECLARE_FAULT_ATTR(fail_io_timeout);
16 
17 static int __init setup_fail_io_timeout(char *str)
18 {
19 	return setup_fault_attr(&fail_io_timeout, str);
20 }
21 __setup("fail_io_timeout=", setup_fail_io_timeout);
22 
23 int blk_should_fake_timeout(struct request_queue *q)
24 {
25 	if (!test_bit(QUEUE_FLAG_FAIL_IO, &q->queue_flags))
26 		return 0;
27 
28 	return should_fail(&fail_io_timeout, 1);
29 }
30 
31 static int __init fail_io_timeout_debugfs(void)
32 {
33 	struct dentry *dir = fault_create_debugfs_attr("fail_io_timeout",
34 						NULL, &fail_io_timeout);
35 
36 	return PTR_ERR_OR_ZERO(dir);
37 }
38 
39 late_initcall(fail_io_timeout_debugfs);
40 
41 ssize_t part_timeout_show(struct device *dev, struct device_attribute *attr,
42 			  char *buf)
43 {
44 	struct gendisk *disk = dev_to_disk(dev);
45 	int set = test_bit(QUEUE_FLAG_FAIL_IO, &disk->queue->queue_flags);
46 
47 	return sprintf(buf, "%d\n", set != 0);
48 }
49 
50 ssize_t part_timeout_store(struct device *dev, struct device_attribute *attr,
51 			   const char *buf, size_t count)
52 {
53 	struct gendisk *disk = dev_to_disk(dev);
54 	int val;
55 
56 	if (count) {
57 		struct request_queue *q = disk->queue;
58 		char *p = (char *) buf;
59 
60 		val = simple_strtoul(p, &p, 10);
61 		if (val)
62 			blk_queue_flag_set(QUEUE_FLAG_FAIL_IO, q);
63 		else
64 			blk_queue_flag_clear(QUEUE_FLAG_FAIL_IO, q);
65 	}
66 
67 	return count;
68 }
69 
70 #endif /* CONFIG_FAIL_IO_TIMEOUT */
71 
72 /**
73  * blk_abort_request -- Request request recovery for the specified command
74  * @req:	pointer to the request of interest
75  *
76  * This function requests that the block layer start recovery for the
77  * request by deleting the timer and calling the q's timeout function.
78  * LLDDs who implement their own error recovery MAY ignore the timeout
79  * event if they generated blk_abort_request.
80  */
81 void blk_abort_request(struct request *req)
82 {
83 	/*
84 	 * All we need to ensure is that timeout scan takes place
85 	 * immediately and that scan sees the new timeout value.
86 	 * No need for fancy synchronizations.
87 	 */
88 	WRITE_ONCE(req->deadline, jiffies);
89 	kblockd_schedule_work(&req->q->timeout_work);
90 }
91 EXPORT_SYMBOL_GPL(blk_abort_request);
92 
93 unsigned long blk_rq_timeout(unsigned long timeout)
94 {
95 	unsigned long maxt;
96 
97 	maxt = round_jiffies_up(jiffies + BLK_MAX_TIMEOUT);
98 	if (time_after(timeout, maxt))
99 		timeout = maxt;
100 
101 	return timeout;
102 }
103 
104 /**
105  * blk_add_timer - Start timeout timer for a single request
106  * @req:	request that is about to start running.
107  *
108  * Notes:
109  *    Each request has its own timer, and as it is added to the queue, we
110  *    set up the timer. When the request completes, we cancel the timer.
111  */
112 void blk_add_timer(struct request *req)
113 {
114 	struct request_queue *q = req->q;
115 	unsigned long expiry;
116 
117 	/*
118 	 * Some LLDs, like scsi, peek at the timeout to prevent a
119 	 * command from being retried forever.
120 	 */
121 	if (!req->timeout)
122 		req->timeout = q->rq_timeout;
123 
124 	req->rq_flags &= ~RQF_TIMED_OUT;
125 
126 	expiry = jiffies + req->timeout;
127 	WRITE_ONCE(req->deadline, expiry);
128 
129 	/*
130 	 * If the timer isn't already pending or this timeout is earlier
131 	 * than an existing one, modify the timer. Round up to next nearest
132 	 * second.
133 	 */
134 	expiry = blk_rq_timeout(round_jiffies_up(expiry));
135 
136 	if (!timer_pending(&q->timeout) ||
137 	    time_before(expiry, q->timeout.expires)) {
138 		unsigned long diff = q->timeout.expires - expiry;
139 
140 		/*
141 		 * Due to added timer slack to group timers, the timer
142 		 * will often be a little in front of what we asked for.
143 		 * So apply some tolerance here too, otherwise we keep
144 		 * modifying the timer because expires for value X
145 		 * will be X + something.
146 		 */
147 		if (!timer_pending(&q->timeout) || (diff >= HZ / 2))
148 			mod_timer(&q->timeout, expiry);
149 	}
150 
151 }
152