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    return init_fault_attr_dentries(&fail_io_timeout, "fail_io_timeout");
32}
33
34late_initcall(fail_io_timeout_debugfs);
35
36ssize_t part_timeout_show(struct device *dev, struct device_attribute *attr,
37              char *buf)
38{
39    struct gendisk *disk = dev_to_disk(dev);
40    int set = test_bit(QUEUE_FLAG_FAIL_IO, &disk->queue->queue_flags);
41
42    return sprintf(buf, "%d\n", set != 0);
43}
44
45ssize_t part_timeout_store(struct device *dev, struct device_attribute *attr,
46               const char *buf, size_t count)
47{
48    struct gendisk *disk = dev_to_disk(dev);
49    int val;
50
51    if (count) {
52        struct request_queue *q = disk->queue;
53        char *p = (char *) buf;
54
55        val = simple_strtoul(p, &p, 10);
56        spin_lock_irq(q->queue_lock);
57        if (val)
58            queue_flag_set(QUEUE_FLAG_FAIL_IO, q);
59        else
60            queue_flag_clear(QUEUE_FLAG_FAIL_IO, q);
61        spin_unlock_irq(q->queue_lock);
62    }
63
64    return count;
65}
66
67#endif /* CONFIG_FAIL_IO_TIMEOUT */
68
69/*
70 * blk_delete_timer - Delete/cancel timer for a given function.
71 * @req: request that we are canceling timer for
72 *
73 */
74void blk_delete_timer(struct request *req)
75{
76    list_del_init(&req->timeout_list);
77}
78
79static void blk_rq_timed_out(struct request *req)
80{
81    struct request_queue *q = req->q;
82    enum blk_eh_timer_return ret;
83
84    ret = q->rq_timed_out_fn(req);
85    switch (ret) {
86    case BLK_EH_HANDLED:
87        __blk_complete_request(req);
88        break;
89    case BLK_EH_RESET_TIMER:
90        blk_clear_rq_complete(req);
91        blk_add_timer(req);
92        break;
93    case BLK_EH_NOT_HANDLED:
94        /*
95         * LLD handles this for now but in the future
96         * we can send a request msg to abort the command
97         * and we can move more of the generic scsi eh code to
98         * the blk layer.
99         */
100        break;
101    default:
102        printk(KERN_ERR "block: bad eh return: %d\n", ret);
103        break;
104    }
105}
106
107void blk_rq_timed_out_timer(unsigned long data)
108{
109    struct request_queue *q = (struct request_queue *) data;
110    unsigned long flags, next = 0;
111    struct request *rq, *tmp;
112
113    spin_lock_irqsave(q->queue_lock, flags);
114
115    list_for_each_entry_safe(rq, tmp, &q->timeout_list, timeout_list) {
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                continue;
124            blk_rq_timed_out(rq);
125        } else if (!next || time_after(next, rq->deadline))
126            next = rq->deadline;
127    }
128
129    /*
130     * next can never be 0 here with the list non-empty, since we always
131     * bump ->deadline to 1 so we can detect if the timer was ever added
132     * or not. See comment in blk_add_timer()
133     */
134    if (next)
135        mod_timer(&q->timeout, round_jiffies_up(next));
136
137    spin_unlock_irqrestore(q->queue_lock, flags);
138}
139
140/**
141 * blk_abort_request -- Request request recovery for the specified command
142 * @req: pointer to the request of interest
143 *
144 * This function requests that the block layer start recovery for the
145 * request by deleting the timer and calling the q's timeout function.
146 * LLDDs who implement their own error recovery MAY ignore the timeout
147 * event if they generated blk_abort_req. Must hold queue lock.
148 */
149void blk_abort_request(struct request *req)
150{
151    if (blk_mark_rq_complete(req))
152        return;
153    blk_delete_timer(req);
154    blk_rq_timed_out(req);
155}
156EXPORT_SYMBOL_GPL(blk_abort_request);
157
158/**
159 * blk_add_timer - Start timeout timer for a single request
160 * @req: request that is about to start running.
161 *
162 * Notes:
163 * Each request has its own timer, and as it is added to the queue, we
164 * set up the timer. When the request completes, we cancel the timer.
165 */
166void blk_add_timer(struct request *req)
167{
168    struct request_queue *q = req->q;
169    unsigned long expiry;
170
171    if (!q->rq_timed_out_fn)
172        return;
173
174    BUG_ON(!list_empty(&req->timeout_list));
175    BUG_ON(test_bit(REQ_ATOM_COMPLETE, &req->atomic_flags));
176
177    /*
178     * Some LLDs, like scsi, peek at the timeout to prevent a
179     * command from being retried forever.
180     */
181    if (!req->timeout)
182        req->timeout = q->rq_timeout;
183
184    req->deadline = jiffies + req->timeout;
185    list_add_tail(&req->timeout_list, &q->timeout_list);
186
187    /*
188     * If the timer isn't already pending or this timeout is earlier
189     * than an existing one, modify the timer. Round up to next nearest
190     * second.
191     */
192    expiry = round_jiffies_up(req->deadline);
193
194    if (!timer_pending(&q->timeout) ||
195        time_before(expiry, q->timeout.expires))
196        mod_timer(&q->timeout, expiry);
197}
198
199/**
200 * blk_abort_queue -- Abort all request on given queue
201 * @queue: pointer to queue
202 *
203 */
204void blk_abort_queue(struct request_queue *q)
205{
206    unsigned long flags;
207    struct request *rq, *tmp;
208    LIST_HEAD(list);
209
210    /*
211     * Not a request based block device, nothing to abort
212     */
213    if (!q->request_fn)
214        return;
215
216    spin_lock_irqsave(q->queue_lock, flags);
217
218    elv_abort_queue(q);
219
220    /*
221     * Splice entries to local list, to avoid deadlocking if entries
222     * get readded to the timeout list by error handling
223     */
224    list_splice_init(&q->timeout_list, &list);
225
226    list_for_each_entry_safe(rq, tmp, &list, timeout_list)
227        blk_abort_request(rq);
228
229    /*
230     * Occasionally, blk_abort_request() will return without
231     * deleting the element from the list. Make sure we add those back
232     * instead of leaving them on the local stack list.
233     */
234    list_splice(&list, &q->timeout_list);
235
236    spin_unlock_irqrestore(q->queue_lock, flags);
237
238}
239EXPORT_SYMBOL_GPL(blk_abort_queue);
240

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