xref: /openbmc/linux/block/blk-timeout.c (revision d958e343)
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 
setup_fail_io_timeout(char * str)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 
__blk_should_fake_timeout(struct request_queue * q)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 
fail_io_timeout_debugfs(void)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 
part_timeout_show(struct device * dev,struct device_attribute * attr,char * buf)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 
part_timeout_store(struct device * dev,struct device_attribute * attr,const char * buf,size_t count)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  */
blk_abort_request(struct request * req)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 
blk_timeout_init(void)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  */
blk_round_jiffies(unsigned long j)104 static inline unsigned long blk_round_jiffies(unsigned long j)
105 {
106 	return (j + blk_timeout_mask) + 1;
107 }
108 
blk_rq_timeout(unsigned long timeout)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  */
blk_add_timer(struct request * req)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