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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 18:20:36 -0400
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 18:20:36 -0400
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /drivers/block/noop-iosched.c
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
Diffstat (limited to 'drivers/block/noop-iosched.c')
-rw-r--r--drivers/block/noop-iosched.c104
1 files changed, 104 insertions, 0 deletions
diff --git a/drivers/block/noop-iosched.c b/drivers/block/noop-iosched.c
new file mode 100644
index 000000000000..888c477e02b3
--- /dev/null
+++ b/drivers/block/noop-iosched.c
@@ -0,0 +1,104 @@
1/*
2 * elevator noop
3 */
4#include <linux/blkdev.h>
5#include <linux/elevator.h>
6#include <linux/bio.h>
7#include <linux/module.h>
8#include <linux/init.h>
9
10/*
11 * See if we can find a request that this buffer can be coalesced with.
12 */
13static int elevator_noop_merge(request_queue_t *q, struct request **req,
14 struct bio *bio)
15{
16 struct list_head *entry = &q->queue_head;
17 struct request *__rq;
18 int ret;
19
20 if ((ret = elv_try_last_merge(q, bio))) {
21 *req = q->last_merge;
22 return ret;
23 }
24
25 while ((entry = entry->prev) != &q->queue_head) {
26 __rq = list_entry_rq(entry);
27
28 if (__rq->flags & (REQ_SOFTBARRIER | REQ_HARDBARRIER))
29 break;
30 else if (__rq->flags & REQ_STARTED)
31 break;
32
33 if (!blk_fs_request(__rq))
34 continue;
35
36 if ((ret = elv_try_merge(__rq, bio))) {
37 *req = __rq;
38 q->last_merge = __rq;
39 return ret;
40 }
41 }
42
43 return ELEVATOR_NO_MERGE;
44}
45
46static void elevator_noop_merge_requests(request_queue_t *q, struct request *req,
47 struct request *next)
48{
49 list_del_init(&next->queuelist);
50}
51
52static void elevator_noop_add_request(request_queue_t *q, struct request *rq,
53 int where)
54{
55 if (where == ELEVATOR_INSERT_FRONT)
56 list_add(&rq->queuelist, &q->queue_head);
57 else
58 list_add_tail(&rq->queuelist, &q->queue_head);
59
60 /*
61 * new merges must not precede this barrier
62 */
63 if (rq->flags & REQ_HARDBARRIER)
64 q->last_merge = NULL;
65 else if (!q->last_merge)
66 q->last_merge = rq;
67}
68
69static struct request *elevator_noop_next_request(request_queue_t *q)
70{
71 if (!list_empty(&q->queue_head))
72 return list_entry_rq(q->queue_head.next);
73
74 return NULL;
75}
76
77static struct elevator_type elevator_noop = {
78 .ops = {
79 .elevator_merge_fn = elevator_noop_merge,
80 .elevator_merge_req_fn = elevator_noop_merge_requests,
81 .elevator_next_req_fn = elevator_noop_next_request,
82 .elevator_add_req_fn = elevator_noop_add_request,
83 },
84 .elevator_name = "noop",
85 .elevator_owner = THIS_MODULE,
86};
87
88static int __init noop_init(void)
89{
90 return elv_register(&elevator_noop);
91}
92
93static void __exit noop_exit(void)
94{
95 elv_unregister(&elevator_noop);
96}
97
98module_init(noop_init);
99module_exit(noop_exit);
100
101
102MODULE_AUTHOR("Jens Axboe");
103MODULE_LICENSE("GPL");
104MODULE_DESCRIPTION("No-op IO scheduler");