Root/block/blk-timeout.c

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
11#ifdef CONFIG_FAIL_IO_TIMEOUT
12
13static DECLARE_FAULT_ATTR(fail_io_timeout);
14
15static int __init setup_fail_io_timeout(char *str)
16{
17    return setup_fault_attr(&fail_io_timeout, str);
18}
19__setup("fail_io_timeout=", setup_fail_io_timeout);
20
21int blk_should_fake_timeout(struct request_queue *q)
22{
23    if (!test_bit(QUEUE_FLAG_FAIL_IO, &q->queue_flags))
24        return 0;
25
26    return should_fail(&fail_io_timeout, 1);
27}
28
29static 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 IS_ERR(dir) ? PTR_ERR(dir) : 0;
35}
36
37late_initcall(fail_io_timeout_debugfs);
38
39ssize_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
48ssize_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        spin_lock_irq(q->queue_lock);
60        if (val)
61            queue_flag_set(QUEUE_FLAG_FAIL_IO, q);
62        else
63            queue_flag_clear(QUEUE_FLAG_FAIL_IO, q);
64        spin_unlock_irq(q->queue_lock);
65    }
66
67    return count;
68}
69
70#endif /* CONFIG_FAIL_IO_TIMEOUT */
71
72/*
73 * blk_delete_timer - Delete/cancel timer for a given function.
74 * @req: request that we are canceling timer for
75 *
76 */
77void blk_delete_timer(struct request *req)
78{
79    list_del_init(&req->timeout_list);
80}
81
82static void blk_rq_timed_out(struct request *req)
83{
84    struct request_queue *q = req->q;
85    enum blk_eh_timer_return ret = BLK_EH_RESET_TIMER;
86
87    if (q->rq_timed_out_fn)
88        ret = q->rq_timed_out_fn(req);
89    switch (ret) {
90    case BLK_EH_HANDLED:
91        __blk_complete_request(req);
92        break;
93    case BLK_EH_RESET_TIMER:
94        blk_clear_rq_complete(req);
95        blk_add_timer(req);
96        break;
97    case BLK_EH_NOT_HANDLED:
98        /*
99         * LLD handles this for now but in the future
100         * we can send a request msg to abort the command
101         * and we can move more of the generic scsi eh code to
102         * the blk layer.
103         */
104        break;
105    default:
106        printk(KERN_ERR "block: bad eh return: %d\n", ret);
107        break;
108    }
109}
110
111void blk_rq_timed_out_timer(unsigned long data)
112{
113    struct request_queue *q = (struct request_queue *) data;
114    unsigned long flags, next = 0;
115    struct request *rq, *tmp;
116    int next_set = 0;
117
118    spin_lock_irqsave(q->queue_lock, flags);
119
120    list_for_each_entry_safe(rq, tmp, &q->timeout_list, timeout_list) {
121        if (time_after_eq(jiffies, rq->deadline)) {
122            list_del_init(&rq->timeout_list);
123
124            /*
125             * Check if we raced with end io completion
126             */
127            if (blk_mark_rq_complete(rq))
128                continue;
129            blk_rq_timed_out(rq);
130        } else if (!next_set || time_after(next, rq->deadline)) {
131            next = rq->deadline;
132            next_set = 1;
133        }
134    }
135
136    if (next_set)
137        mod_timer(&q->timeout, round_jiffies_up(next));
138
139    spin_unlock_irqrestore(q->queue_lock, flags);
140}
141
142/**
143 * blk_abort_request -- Request request recovery for the specified command
144 * @req: pointer to the request of interest
145 *
146 * This function requests that the block layer start recovery for the
147 * request by deleting the timer and calling the q's timeout function.
148 * LLDDs who implement their own error recovery MAY ignore the timeout
149 * event if they generated blk_abort_req. Must hold queue lock.
150 */
151void blk_abort_request(struct request *req)
152{
153    if (blk_mark_rq_complete(req))
154        return;
155    blk_delete_timer(req);
156    blk_rq_timed_out(req);
157}
158EXPORT_SYMBOL_GPL(blk_abort_request);
159
160/**
161 * blk_add_timer - Start timeout timer for a single request
162 * @req: request that is about to start running.
163 *
164 * Notes:
165 * Each request has its own timer, and as it is added to the queue, we
166 * set up the timer. When the request completes, we cancel the timer.
167 */
168void blk_add_timer(struct request *req)
169{
170    struct request_queue *q = req->q;
171    unsigned long expiry;
172
173    if (!q->rq_timed_out_fn)
174        return;
175
176    BUG_ON(!list_empty(&req->timeout_list));
177    BUG_ON(test_bit(REQ_ATOM_COMPLETE, &req->atomic_flags));
178
179    /*
180     * Some LLDs, like scsi, peek at the timeout to prevent a
181     * command from being retried forever.
182     */
183    if (!req->timeout)
184        req->timeout = q->rq_timeout;
185
186    req->deadline = jiffies + req->timeout;
187    list_add_tail(&req->timeout_list, &q->timeout_list);
188
189    /*
190     * If the timer isn't already pending or this timeout is earlier
191     * than an existing one, modify the timer. Round up to next nearest
192     * second.
193     */
194    expiry = round_jiffies_up(req->deadline);
195
196    if (!timer_pending(&q->timeout) ||
197        time_before(expiry, q->timeout.expires))
198        mod_timer(&q->timeout, expiry);
199}
200
201

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