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authorJens Axboe2008-09-14 07:55:09 -0500
committerJens Axboe2008-10-09 01:56:13 -0500
commit242f9dcb8ba6f68fcd217a119a7648a4f69290e9 (patch)
tree1bfe245ffbc50d204d76665cd8f90d85100f86a1 /block/blk-timeout.c
parent608aeef17a91747d6303de4df5e2c2e6899a95e8 (diff)
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block: unify request timeout handling
Right now SCSI and others do their own command timeout handling. Move those bits to the block layer. Instead of having a timer per command, we try to be a bit more clever and simply have one per-queue. This avoids the overhead of having to tear down and setup a timer for each command, so it will result in a lot less timer fiddling. Signed-off-by: Mike Anderson <andmike@linux.vnet.ibm.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Diffstat (limited to 'block/blk-timeout.c')
-rw-r--r--block/blk-timeout.c155
1 files changed, 155 insertions, 0 deletions
diff --git a/block/blk-timeout.c b/block/blk-timeout.c
new file mode 100644
index 00000000000..b36d07bf0af
--- /dev/null
+++ b/block/blk-timeout.c
@@ -0,0 +1,155 @@
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
8#include "blk.h"
9
10/*
11 * blk_delete_timer - Delete/cancel timer for a given function.
12 * @req: request that we are canceling timer for
13 *
14 */
15void blk_delete_timer(struct request *req)
16{
17 struct request_queue *q = req->q;
18
19 /*
20 * Nothing to detach
21 */
22 if (!q->rq_timed_out_fn || !req->deadline)
23 return;
24
25 list_del_init(&req->timeout_list);
26
27 if (list_empty(&q->timeout_list))
28 del_timer(&q->timeout);
29}
30
31static void blk_rq_timed_out(struct request *req)
32{
33 struct request_queue *q = req->q;
34 enum blk_eh_timer_return ret;
35
36 ret = q->rq_timed_out_fn(req);
37 switch (ret) {
38 case BLK_EH_HANDLED:
39 __blk_complete_request(req);
40 break;
41 case BLK_EH_RESET_TIMER:
42 blk_clear_rq_complete(req);
43 blk_add_timer(req);
44 break;
45 case BLK_EH_NOT_HANDLED:
46 /*
47 * LLD handles this for now but in the future
48 * we can send a request msg to abort the command
49 * and we can move more of the generic scsi eh code to
50 * the blk layer.
51 */
52 break;
53 default:
54 printk(KERN_ERR "block: bad eh return: %d\n", ret);
55 break;
56 }
57}
58
59void blk_rq_timed_out_timer(unsigned long data)
60{
61 struct request_queue *q = (struct request_queue *) data;
62 unsigned long flags, uninitialized_var(next), next_set = 0;
63 struct request *rq, *tmp;
64
65 spin_lock_irqsave(q->queue_lock, flags);
66
67 list_for_each_entry_safe(rq, tmp, &q->timeout_list, timeout_list) {
68 if (time_after_eq(jiffies, rq->deadline)) {
69 list_del_init(&rq->timeout_list);
70
71 /*
72 * Check if we raced with end io completion
73 */
74 if (blk_mark_rq_complete(rq))
75 continue;
76 blk_rq_timed_out(rq);
77 }
78 if (!next_set) {
79 next = rq->deadline;
80 next_set = 1;
81 } else if (time_after(next, rq->deadline))
82 next = rq->deadline;
83 }
84
85 if (next_set && !list_empty(&q->timeout_list))
86 mod_timer(&q->timeout, round_jiffies(next));
87
88 spin_unlock_irqrestore(q->queue_lock, flags);
89}
90
91/**
92 * blk_abort_request -- Request request recovery for the specified command
93 * @req: pointer to the request of interest
94 *
95 * This function requests that the block layer start recovery for the
96 * request by deleting the timer and calling the q's timeout function.
97 * LLDDs who implement their own error recovery MAY ignore the timeout
98 * event if they generated blk_abort_req. Must hold queue lock.
99 */
100void blk_abort_request(struct request *req)
101{
102 blk_delete_timer(req);
103 blk_rq_timed_out(req);
104}
105EXPORT_SYMBOL_GPL(blk_abort_request);
106
107/**
108 * blk_add_timer - Start timeout timer for a single request
109 * @req: request that is about to start running.
110 *
111 * Notes:
112 * Each request has its own timer, and as it is added to the queue, we
113 * set up the timer. When the request completes, we cancel the timer.
114 */
115void blk_add_timer(struct request *req)
116{
117 struct request_queue *q = req->q;
118 unsigned long expiry;
119
120 if (!q->rq_timed_out_fn)
121 return;
122
123 BUG_ON(!list_empty(&req->timeout_list));
124 BUG_ON(test_bit(REQ_ATOM_COMPLETE, &req->atomic_flags));
125
126 if (req->timeout)
127 req->deadline = jiffies + req->timeout;
128 else {
129 req->deadline = jiffies + q->rq_timeout;
130 /*
131 * Some LLDs, like scsi, peek at the timeout to prevent
132 * a command from being retried forever.
133 */
134 req->timeout = q->rq_timeout;
135 }
136 list_add_tail(&req->timeout_list, &q->timeout_list);
137
138 /*
139 * If the timer isn't already pending or this timeout is earlier
140 * than an existing one, modify the timer. Round to next nearest
141 * second.
142 */
143 expiry = round_jiffies(req->deadline);
144
145 /*
146 * We use ->deadline == 0 to detect whether a timer was added or
147 * not, so just increase to next jiffy for that specific case
148 */
149 if (unlikely(!req->deadline))
150 req->deadline = 1;
151
152 if (!timer_pending(&q->timeout) ||
153 time_before(expiry, q->timeout.expires))
154 mod_timer(&q->timeout, expiry);
155}