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    int next_set = 0;
113
114    spin_lock_irqsave(q->queue_lock, flags);
115
116    list_for_each_entry_safe(rq, tmp, &q->timeout_list, timeout_list) {
117        if (time_after_eq(jiffies, rq->deadline)) {
118            list_del_init(&rq->timeout_list);
119
120            /*
121             * Check if we raced with end io completion
122             */
123            if (blk_mark_rq_complete(rq))
124                continue;
125            blk_rq_timed_out(rq);
126        } else if (!next_set || time_after(next, rq->deadline)) {
127            next = rq->deadline;
128            next_set = 1;
129        }
130    }
131
132    if (next_set)
133        mod_timer(&q->timeout, round_jiffies_up(next));
134
135    spin_unlock_irqrestore(q->queue_lock, flags);
136}
137
138/**
139 * blk_abort_request -- Request request recovery for the specified command
140 * @req: pointer to the request of interest
141 *
142 * This function requests that the block layer start recovery for the
143 * request by deleting the timer and calling the q's timeout function.
144 * LLDDs who implement their own error recovery MAY ignore the timeout
145 * event if they generated blk_abort_req. Must hold queue lock.
146 */
147void blk_abort_request(struct request *req)
148{
149    if (blk_mark_rq_complete(req))
150        return;
151    blk_delete_timer(req);
152    blk_rq_timed_out(req);
153}
154EXPORT_SYMBOL_GPL(blk_abort_request);
155
156/**
157 * blk_add_timer - Start timeout timer for a single request
158 * @req: request that is about to start running.
159 *
160 * Notes:
161 * Each request has its own timer, and as it is added to the queue, we
162 * set up the timer. When the request completes, we cancel the timer.
163 */
164void blk_add_timer(struct request *req)
165{
166    struct request_queue *q = req->q;
167    unsigned long expiry;
168
169    if (!q->rq_timed_out_fn)
170        return;
171
172    BUG_ON(!list_empty(&req->timeout_list));
173    BUG_ON(test_bit(REQ_ATOM_COMPLETE, &req->atomic_flags));
174
175    /*
176     * Some LLDs, like scsi, peek at the timeout to prevent a
177     * command from being retried forever.
178     */
179    if (!req->timeout)
180        req->timeout = q->rq_timeout;
181
182    req->deadline = jiffies + req->timeout;
183    list_add_tail(&req->timeout_list, &q->timeout_list);
184
185    /*
186     * If the timer isn't already pending or this timeout is earlier
187     * than an existing one, modify the timer. Round up to next nearest
188     * second.
189     */
190    expiry = round_jiffies_up(req->deadline);
191
192    if (!timer_pending(&q->timeout) ||
193        time_before(expiry, q->timeout.expires))
194        mod_timer(&q->timeout, expiry);
195}
196
197/**
198 * blk_abort_queue -- Abort all request on given queue
199 * @queue: pointer to queue
200 *
201 */
202void blk_abort_queue(struct request_queue *q)
203{
204    unsigned long flags;
205    struct request *rq, *tmp;
206    LIST_HEAD(list);
207
208    /*
209     * Not a request based block device, nothing to abort
210     */
211    if (!q->request_fn)
212        return;
213
214    spin_lock_irqsave(q->queue_lock, flags);
215
216    elv_abort_queue(q);
217
218    /*
219     * Splice entries to local list, to avoid deadlocking if entries
220     * get readded to the timeout list by error handling
221     */
222    list_splice_init(&q->timeout_list, &list);
223
224    list_for_each_entry_safe(rq, tmp, &list, timeout_list)
225        blk_abort_request(rq);
226
227    /*
228     * Occasionally, blk_abort_request() will return without
229     * deleting the element from the list. Make sure we add those back
230     * instead of leaving them on the local stack list.
231     */
232    list_splice(&list, &q->timeout_list);
233
234    spin_unlock_irqrestore(q->queue_lock, flags);
235
236}
237EXPORT_SYMBOL_GPL(blk_abort_queue);
238

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