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[mv-sheeva.git] / drivers / md / dm-delay.c
1 /*
2  * Copyright (C) 2005-2007 Red Hat GmbH
3  *
4  * A target that delays reads and/or writes and can send
5  * them to different devices.
6  *
7  * This file is released under the GPL.
8  */
9
10 #include <linux/module.h>
11 #include <linux/init.h>
12 #include <linux/blkdev.h>
13 #include <linux/bio.h>
14 #include <linux/slab.h>
15
16 #include <linux/device-mapper.h>
17
18 #define DM_MSG_PREFIX "delay"
19
20 struct delay_c {
21         struct timer_list delay_timer;
22         struct mutex timer_lock;
23         struct work_struct flush_expired_bios;
24         struct list_head delayed_bios;
25         atomic_t may_delay;
26         mempool_t *delayed_pool;
27
28         struct dm_dev *dev_read;
29         sector_t start_read;
30         unsigned read_delay;
31         unsigned reads;
32
33         struct dm_dev *dev_write;
34         sector_t start_write;
35         unsigned write_delay;
36         unsigned writes;
37 };
38
39 struct dm_delay_info {
40         struct delay_c *context;
41         struct list_head list;
42         struct bio *bio;
43         unsigned long expires;
44 };
45
46 static DEFINE_MUTEX(delayed_bios_lock);
47
48 static struct workqueue_struct *kdelayd_wq;
49 static struct kmem_cache *delayed_cache;
50
51 static void handle_delayed_timer(unsigned long data)
52 {
53         struct delay_c *dc = (struct delay_c *)data;
54
55         queue_work(kdelayd_wq, &dc->flush_expired_bios);
56 }
57
58 static void queue_timeout(struct delay_c *dc, unsigned long expires)
59 {
60         mutex_lock(&dc->timer_lock);
61
62         if (!timer_pending(&dc->delay_timer) || expires < dc->delay_timer.expires)
63                 mod_timer(&dc->delay_timer, expires);
64
65         mutex_unlock(&dc->timer_lock);
66 }
67
68 static void flush_bios(struct bio *bio)
69 {
70         struct bio *n;
71
72         while (bio) {
73                 n = bio->bi_next;
74                 bio->bi_next = NULL;
75                 generic_make_request(bio);
76                 bio = n;
77         }
78 }
79
80 static struct bio *flush_delayed_bios(struct delay_c *dc, int flush_all)
81 {
82         struct dm_delay_info *delayed, *next;
83         unsigned long next_expires = 0;
84         int start_timer = 0;
85         struct bio_list flush_bios = { };
86
87         mutex_lock(&delayed_bios_lock);
88         list_for_each_entry_safe(delayed, next, &dc->delayed_bios, list) {
89                 if (flush_all || time_after_eq(jiffies, delayed->expires)) {
90                         list_del(&delayed->list);
91                         bio_list_add(&flush_bios, delayed->bio);
92                         if ((bio_data_dir(delayed->bio) == WRITE))
93                                 delayed->context->writes--;
94                         else
95                                 delayed->context->reads--;
96                         mempool_free(delayed, dc->delayed_pool);
97                         continue;
98                 }
99
100                 if (!start_timer) {
101                         start_timer = 1;
102                         next_expires = delayed->expires;
103                 } else
104                         next_expires = min(next_expires, delayed->expires);
105         }
106
107         mutex_unlock(&delayed_bios_lock);
108
109         if (start_timer)
110                 queue_timeout(dc, next_expires);
111
112         return bio_list_get(&flush_bios);
113 }
114
115 static void flush_expired_bios(struct work_struct *work)
116 {
117         struct delay_c *dc;
118
119         dc = container_of(work, struct delay_c, flush_expired_bios);
120         flush_bios(flush_delayed_bios(dc, 0));
121 }
122
123 /*
124  * Mapping parameters:
125  *    <device> <offset> <delay> [<write_device> <write_offset> <write_delay>]
126  *
127  * With separate write parameters, the first set is only used for reads.
128  * Delays are specified in milliseconds.
129  */
130 static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv)
131 {
132         struct delay_c *dc;
133         unsigned long long tmpll;
134
135         if (argc != 3 && argc != 6) {
136                 ti->error = "requires exactly 3 or 6 arguments";
137                 return -EINVAL;
138         }
139
140         dc = kmalloc(sizeof(*dc), GFP_KERNEL);
141         if (!dc) {
142                 ti->error = "Cannot allocate context";
143                 return -ENOMEM;
144         }
145
146         dc->reads = dc->writes = 0;
147
148         if (sscanf(argv[1], "%llu", &tmpll) != 1) {
149                 ti->error = "Invalid device sector";
150                 goto bad;
151         }
152         dc->start_read = tmpll;
153
154         if (sscanf(argv[2], "%u", &dc->read_delay) != 1) {
155                 ti->error = "Invalid delay";
156                 goto bad;
157         }
158
159         if (dm_get_device(ti, argv[0], dm_table_get_mode(ti->table),
160                           &dc->dev_read)) {
161                 ti->error = "Device lookup failed";
162                 goto bad;
163         }
164
165         dc->dev_write = NULL;
166         if (argc == 3)
167                 goto out;
168
169         if (sscanf(argv[4], "%llu", &tmpll) != 1) {
170                 ti->error = "Invalid write device sector";
171                 goto bad_dev_read;
172         }
173         dc->start_write = tmpll;
174
175         if (sscanf(argv[5], "%u", &dc->write_delay) != 1) {
176                 ti->error = "Invalid write delay";
177                 goto bad_dev_read;
178         }
179
180         if (dm_get_device(ti, argv[3], dm_table_get_mode(ti->table),
181                           &dc->dev_write)) {
182                 ti->error = "Write device lookup failed";
183                 goto bad_dev_read;
184         }
185
186 out:
187         dc->delayed_pool = mempool_create_slab_pool(128, delayed_cache);
188         if (!dc->delayed_pool) {
189                 DMERR("Couldn't create delayed bio pool.");
190                 goto bad_dev_write;
191         }
192
193         setup_timer(&dc->delay_timer, handle_delayed_timer, (unsigned long)dc);
194
195         INIT_WORK(&dc->flush_expired_bios, flush_expired_bios);
196         INIT_LIST_HEAD(&dc->delayed_bios);
197         mutex_init(&dc->timer_lock);
198         atomic_set(&dc->may_delay, 1);
199
200         ti->num_flush_requests = 1;
201         ti->num_discard_requests = 1;
202         ti->private = dc;
203         return 0;
204
205 bad_dev_write:
206         if (dc->dev_write)
207                 dm_put_device(ti, dc->dev_write);
208 bad_dev_read:
209         dm_put_device(ti, dc->dev_read);
210 bad:
211         kfree(dc);
212         return -EINVAL;
213 }
214
215 static void delay_dtr(struct dm_target *ti)
216 {
217         struct delay_c *dc = ti->private;
218
219         flush_workqueue(kdelayd_wq);
220
221         dm_put_device(ti, dc->dev_read);
222
223         if (dc->dev_write)
224                 dm_put_device(ti, dc->dev_write);
225
226         mempool_destroy(dc->delayed_pool);
227         kfree(dc);
228 }
229
230 static int delay_bio(struct delay_c *dc, int delay, struct bio *bio)
231 {
232         struct dm_delay_info *delayed;
233         unsigned long expires = 0;
234
235         if (!delay || !atomic_read(&dc->may_delay))
236                 return 1;
237
238         delayed = mempool_alloc(dc->delayed_pool, GFP_NOIO);
239
240         delayed->context = dc;
241         delayed->bio = bio;
242         delayed->expires = expires = jiffies + (delay * HZ / 1000);
243
244         mutex_lock(&delayed_bios_lock);
245
246         if (bio_data_dir(bio) == WRITE)
247                 dc->writes++;
248         else
249                 dc->reads++;
250
251         list_add_tail(&delayed->list, &dc->delayed_bios);
252
253         mutex_unlock(&delayed_bios_lock);
254
255         queue_timeout(dc, expires);
256
257         return 0;
258 }
259
260 static void delay_presuspend(struct dm_target *ti)
261 {
262         struct delay_c *dc = ti->private;
263
264         atomic_set(&dc->may_delay, 0);
265         del_timer_sync(&dc->delay_timer);
266         flush_bios(flush_delayed_bios(dc, 1));
267 }
268
269 static void delay_resume(struct dm_target *ti)
270 {
271         struct delay_c *dc = ti->private;
272
273         atomic_set(&dc->may_delay, 1);
274 }
275
276 static int delay_map(struct dm_target *ti, struct bio *bio,
277                      union map_info *map_context)
278 {
279         struct delay_c *dc = ti->private;
280
281         if ((bio_data_dir(bio) == WRITE) && (dc->dev_write)) {
282                 bio->bi_bdev = dc->dev_write->bdev;
283                 if (bio_sectors(bio))
284                         bio->bi_sector = dc->start_write +
285                                          dm_target_offset(ti, bio->bi_sector);
286
287                 return delay_bio(dc, dc->write_delay, bio);
288         }
289
290         bio->bi_bdev = dc->dev_read->bdev;
291         bio->bi_sector = dc->start_read + dm_target_offset(ti, bio->bi_sector);
292
293         return delay_bio(dc, dc->read_delay, bio);
294 }
295
296 static int delay_status(struct dm_target *ti, status_type_t type,
297                         char *result, unsigned maxlen)
298 {
299         struct delay_c *dc = ti->private;
300         int sz = 0;
301
302         switch (type) {
303         case STATUSTYPE_INFO:
304                 DMEMIT("%u %u", dc->reads, dc->writes);
305                 break;
306
307         case STATUSTYPE_TABLE:
308                 DMEMIT("%s %llu %u", dc->dev_read->name,
309                        (unsigned long long) dc->start_read,
310                        dc->read_delay);
311                 if (dc->dev_write)
312                         DMEMIT(" %s %llu %u", dc->dev_write->name,
313                                (unsigned long long) dc->start_write,
314                                dc->write_delay);
315                 break;
316         }
317
318         return 0;
319 }
320
321 static int delay_iterate_devices(struct dm_target *ti,
322                                  iterate_devices_callout_fn fn, void *data)
323 {
324         struct delay_c *dc = ti->private;
325         int ret = 0;
326
327         ret = fn(ti, dc->dev_read, dc->start_read, ti->len, data);
328         if (ret)
329                 goto out;
330
331         if (dc->dev_write)
332                 ret = fn(ti, dc->dev_write, dc->start_write, ti->len, data);
333
334 out:
335         return ret;
336 }
337
338 static struct target_type delay_target = {
339         .name        = "delay",
340         .version     = {1, 1, 0},
341         .module      = THIS_MODULE,
342         .ctr         = delay_ctr,
343         .dtr         = delay_dtr,
344         .map         = delay_map,
345         .presuspend  = delay_presuspend,
346         .resume      = delay_resume,
347         .status      = delay_status,
348         .iterate_devices = delay_iterate_devices,
349 };
350
351 static int __init dm_delay_init(void)
352 {
353         int r = -ENOMEM;
354
355         kdelayd_wq = alloc_workqueue("kdelayd", WQ_MEM_RECLAIM, 0);
356         if (!kdelayd_wq) {
357                 DMERR("Couldn't start kdelayd");
358                 goto bad_queue;
359         }
360
361         delayed_cache = KMEM_CACHE(dm_delay_info, 0);
362         if (!delayed_cache) {
363                 DMERR("Couldn't create delayed bio cache.");
364                 goto bad_memcache;
365         }
366
367         r = dm_register_target(&delay_target);
368         if (r < 0) {
369                 DMERR("register failed %d", r);
370                 goto bad_register;
371         }
372
373         return 0;
374
375 bad_register:
376         kmem_cache_destroy(delayed_cache);
377 bad_memcache:
378         destroy_workqueue(kdelayd_wq);
379 bad_queue:
380         return r;
381 }
382
383 static void __exit dm_delay_exit(void)
384 {
385         dm_unregister_target(&delay_target);
386         kmem_cache_destroy(delayed_cache);
387         destroy_workqueue(kdelayd_wq);
388 }
389
390 /* Module hooks */
391 module_init(dm_delay_init);
392 module_exit(dm_delay_exit);
393
394 MODULE_DESCRIPTION(DM_NAME " delay target");
395 MODULE_AUTHOR("Heinz Mauelshagen <mauelshagen@redhat.com>");
396 MODULE_LICENSE("GPL");