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 bool __blk_should_fake_timeout(struct request_queue *q)
24 {
25 return should_fail(&fail_io_timeout, 1);
26 }
27 EXPORT_SYMBOL_GPL(__blk_should_fake_timeout);
28
29 static int __init fail_io_timeout_debugfs(void)
30 {
31 struct dentry *dir = fault_create_debugfs_attr("fail_io_timeout",
32 NULL, &fail_io_timeout);
33
34 return PTR_ERR_OR_ZERO(dir);
35 }
36
37 late_initcall(fail_io_timeout_debugfs);
38
39 ssize_t part_timeout_show(struct device *dev, struct device_attribute *attr,
40 char *buf)
41 {
42 struct gendisk *disk = dev_to_disk(dev);
43 int set = test_bit(QUEUE_FLAG_FAIL_IO, &disk->queue->queue_flags);
44
45 return sprintf(buf, "%d\n", set != 0);
46 }
47
48 ssize_t part_timeout_store(struct device *dev, struct device_attribute *attr,
49 const char *buf, size_t count)
50 {
51 struct gendisk *disk = dev_to_disk(dev);
52 int val;
53
54 if (count) {
55 struct request_queue *q = disk->queue;
56 char *p = (char *) buf;
57
58 val = simple_strtoul(p, &p, 10);
59 if (val)
60 blk_queue_flag_set(QUEUE_FLAG_FAIL_IO, q);
61 else
62 blk_queue_flag_clear(QUEUE_FLAG_FAIL_IO, q);
63 }
64
65 return count;
66 }
67
68 #endif /* CONFIG_FAIL_IO_TIMEOUT */
69
70 /**
71 * blk_abort_request - Request recovery for the specified command
72 * @req: pointer to the request of interest
73 *
74 * This function requests that the block layer start recovery for the
75 * request by deleting the timer and calling the q's timeout function.
76 * LLDDs who implement their own error recovery MAY ignore the timeout
77 * event if they generated blk_abort_request.
78 */
79 void blk_abort_request(struct request *req)
80 {
81 /*
82 * All we need to ensure is that timeout scan takes place
83 * immediately and that scan sees the new timeout value.
84 * No need for fancy synchronizations.
85 */
86 WRITE_ONCE(req->deadline, jiffies);
87 kblockd_schedule_work(&req->q->timeout_work);
88 }
89 EXPORT_SYMBOL_GPL(blk_abort_request);
90
91 static unsigned long blk_timeout_mask __read_mostly;
92
93 static int __init blk_timeout_init(void)
94 {
95 blk_timeout_mask = roundup_pow_of_two(HZ) - 1;
96 return 0;
97 }
98
99 late_initcall(blk_timeout_init);
100
101 /*
102 * Just a rough estimate, we don't care about specific values for timeouts.
103 */
104 static inline unsigned long blk_round_jiffies(unsigned long j)
105 {
106 return (j + blk_timeout_mask) + 1;
107 }
108
109 unsigned long blk_rq_timeout(unsigned long timeout)
110 {
111 unsigned long maxt;
112
113 maxt = blk_round_jiffies(jiffies + BLK_MAX_TIMEOUT);
114 if (time_after(timeout, maxt))
115 timeout = maxt;
116
117 return timeout;
118 }
119
120 /**
121 * blk_add_timer - Start timeout timer for a single request
122 * @req: request that is about to start running.
123 *
124 * Notes:
125 * Each request has its own timer, and as it is added to the queue, we
126 * set up the timer. When the request completes, we cancel the timer.
127 */
128 void blk_add_timer(struct request *req)
129 {
130 struct request_queue *q = req->q;
131 unsigned long expiry;
132
133 /*
134 * Some LLDs, like scsi, peek at the timeout to prevent a
135 * command from being retried forever.
136 */
137 if (!req->timeout)
138 req->timeout = q->rq_timeout;
139
140 req->rq_flags &= ~RQF_TIMED_OUT;
141
142 expiry = jiffies + req->timeout;
143 WRITE_ONCE(req->deadline, expiry);
144
145 /*
146 * If the timer isn't already pending or this timeout is earlier
147 * than an existing one, modify the timer. Round up to next nearest
148 * second.
149 */
150 expiry = blk_rq_timeout(blk_round_jiffies(expiry));
151
152 if (!timer_pending(&q->timeout) ||
153 time_before(expiry, q->timeout.expires)) {
154 unsigned long diff = q->timeout.expires - expiry;
155
156 /*
157 * Due to added timer slack to group timers, the timer
158 * will often be a little in front of what we asked for.
159 * So apply some tolerance here too, otherwise we keep
160 * modifying the timer because expires for value X
161 * will be X + something.
162 */
163 if (!timer_pending(&q->timeout) || (diff >= HZ / 2))
164 mod_timer(&q->timeout, expiry);
165 }
166
167 }
168
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.