2 * Copyright (C) 2005-2007 Red Hat GmbH
4 * A target that delays reads and/or writes and can send
5 * them to different devices.
7 * This file is released under the GPL.
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>
16 #include <linux/device-mapper.h>
18 #define DM_MSG_PREFIX "delay"
21 struct timer_list delay_timer;
22 struct mutex timer_lock;
23 struct workqueue_struct *kdelayd_wq;
24 struct work_struct flush_expired_bios;
25 struct list_head delayed_bios;
27 mempool_t *delayed_pool;
29 struct dm_dev *dev_read;
34 struct dm_dev *dev_write;
40 struct dm_delay_info {
41 struct delay_c *context;
42 struct list_head list;
44 unsigned long expires;
47 static DEFINE_MUTEX(delayed_bios_lock);
49 static struct kmem_cache *delayed_cache;
51 static void handle_delayed_timer(unsigned long data)
53 struct delay_c *dc = (struct delay_c *)data;
55 queue_work(dc->kdelayd_wq, &dc->flush_expired_bios);
58 static void queue_timeout(struct delay_c *dc, unsigned long expires)
60 mutex_lock(&dc->timer_lock);
62 if (!timer_pending(&dc->delay_timer) || expires < dc->delay_timer.expires)
63 mod_timer(&dc->delay_timer, expires);
65 mutex_unlock(&dc->timer_lock);
68 static void flush_bios(struct bio *bio)
75 generic_make_request(bio);
80 static struct bio *flush_delayed_bios(struct delay_c *dc, int flush_all)
82 struct dm_delay_info *delayed, *next;
83 unsigned long next_expires = 0;
85 struct bio_list flush_bios = { };
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--;
95 delayed->context->reads--;
96 mempool_free(delayed, dc->delayed_pool);
102 next_expires = delayed->expires;
104 next_expires = min(next_expires, delayed->expires);
107 mutex_unlock(&delayed_bios_lock);
110 queue_timeout(dc, next_expires);
112 return bio_list_get(&flush_bios);
115 static void flush_expired_bios(struct work_struct *work)
119 dc = container_of(work, struct delay_c, flush_expired_bios);
120 flush_bios(flush_delayed_bios(dc, 0));
124 * Mapping parameters:
125 * <device> <offset> <delay> [<write_device> <write_offset> <write_delay>]
127 * With separate write parameters, the first set is only used for reads.
128 * Delays are specified in milliseconds.
130 static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv)
133 unsigned long long tmpll;
135 if (argc != 3 && argc != 6) {
136 ti->error = "requires exactly 3 or 6 arguments";
140 dc = kmalloc(sizeof(*dc), GFP_KERNEL);
142 ti->error = "Cannot allocate context";
146 dc->reads = dc->writes = 0;
148 if (sscanf(argv[1], "%llu", &tmpll) != 1) {
149 ti->error = "Invalid device sector";
152 dc->start_read = tmpll;
154 if (sscanf(argv[2], "%u", &dc->read_delay) != 1) {
155 ti->error = "Invalid delay";
159 if (dm_get_device(ti, argv[0], dm_table_get_mode(ti->table),
161 ti->error = "Device lookup failed";
165 dc->dev_write = NULL;
169 if (sscanf(argv[4], "%llu", &tmpll) != 1) {
170 ti->error = "Invalid write device sector";
173 dc->start_write = tmpll;
175 if (sscanf(argv[5], "%u", &dc->write_delay) != 1) {
176 ti->error = "Invalid write delay";
180 if (dm_get_device(ti, argv[3], dm_table_get_mode(ti->table),
182 ti->error = "Write device lookup failed";
187 dc->delayed_pool = mempool_create_slab_pool(128, delayed_cache);
188 if (!dc->delayed_pool) {
189 DMERR("Couldn't create delayed bio pool.");
193 dc->kdelayd_wq = alloc_workqueue("kdelayd", WQ_MEM_RECLAIM, 0);
194 if (!dc->kdelayd_wq) {
195 DMERR("Couldn't start kdelayd");
199 setup_timer(&dc->delay_timer, handle_delayed_timer, (unsigned long)dc);
201 INIT_WORK(&dc->flush_expired_bios, flush_expired_bios);
202 INIT_LIST_HEAD(&dc->delayed_bios);
203 mutex_init(&dc->timer_lock);
204 atomic_set(&dc->may_delay, 1);
206 ti->num_flush_requests = 1;
207 ti->num_discard_requests = 1;
212 mempool_destroy(dc->delayed_pool);
215 dm_put_device(ti, dc->dev_write);
217 dm_put_device(ti, dc->dev_read);
223 static void delay_dtr(struct dm_target *ti)
225 struct delay_c *dc = ti->private;
227 destroy_workqueue(dc->kdelayd_wq);
229 dm_put_device(ti, dc->dev_read);
232 dm_put_device(ti, dc->dev_write);
234 mempool_destroy(dc->delayed_pool);
238 static int delay_bio(struct delay_c *dc, int delay, struct bio *bio)
240 struct dm_delay_info *delayed;
241 unsigned long expires = 0;
243 if (!delay || !atomic_read(&dc->may_delay))
246 delayed = mempool_alloc(dc->delayed_pool, GFP_NOIO);
248 delayed->context = dc;
250 delayed->expires = expires = jiffies + (delay * HZ / 1000);
252 mutex_lock(&delayed_bios_lock);
254 if (bio_data_dir(bio) == WRITE)
259 list_add_tail(&delayed->list, &dc->delayed_bios);
261 mutex_unlock(&delayed_bios_lock);
263 queue_timeout(dc, expires);
268 static void delay_presuspend(struct dm_target *ti)
270 struct delay_c *dc = ti->private;
272 atomic_set(&dc->may_delay, 0);
273 del_timer_sync(&dc->delay_timer);
274 flush_bios(flush_delayed_bios(dc, 1));
277 static void delay_resume(struct dm_target *ti)
279 struct delay_c *dc = ti->private;
281 atomic_set(&dc->may_delay, 1);
284 static int delay_map(struct dm_target *ti, struct bio *bio,
285 union map_info *map_context)
287 struct delay_c *dc = ti->private;
289 if ((bio_data_dir(bio) == WRITE) && (dc->dev_write)) {
290 bio->bi_bdev = dc->dev_write->bdev;
291 if (bio_sectors(bio))
292 bio->bi_sector = dc->start_write +
293 dm_target_offset(ti, bio->bi_sector);
295 return delay_bio(dc, dc->write_delay, bio);
298 bio->bi_bdev = dc->dev_read->bdev;
299 bio->bi_sector = dc->start_read + dm_target_offset(ti, bio->bi_sector);
301 return delay_bio(dc, dc->read_delay, bio);
304 static void delay_status(struct dm_target *ti, status_type_t type,
305 char *result, unsigned maxlen)
307 struct delay_c *dc = ti->private;
311 case STATUSTYPE_INFO:
312 DMEMIT("%u %u", dc->reads, dc->writes);
315 case STATUSTYPE_TABLE:
316 DMEMIT("%s %llu %u", dc->dev_read->name,
317 (unsigned long long) dc->start_read,
320 DMEMIT(" %s %llu %u", dc->dev_write->name,
321 (unsigned long long) dc->start_write,
327 static int delay_iterate_devices(struct dm_target *ti,
328 iterate_devices_callout_fn fn, void *data)
330 struct delay_c *dc = ti->private;
333 ret = fn(ti, dc->dev_read, dc->start_read, ti->len, data);
338 ret = fn(ti, dc->dev_write, dc->start_write, ti->len, data);
344 static struct target_type delay_target = {
346 .version = {1, 1, 1},
347 .module = THIS_MODULE,
351 .presuspend = delay_presuspend,
352 .resume = delay_resume,
353 .status = delay_status,
354 .iterate_devices = delay_iterate_devices,
357 static int __init dm_delay_init(void)
361 delayed_cache = KMEM_CACHE(dm_delay_info, 0);
362 if (!delayed_cache) {
363 DMERR("Couldn't create delayed bio cache.");
367 r = dm_register_target(&delay_target);
369 DMERR("register failed %d", r);
376 kmem_cache_destroy(delayed_cache);
381 static void __exit dm_delay_exit(void)
383 dm_unregister_target(&delay_target);
384 kmem_cache_destroy(delayed_cache);
388 module_init(dm_delay_init);
389 module_exit(dm_delay_exit);
391 MODULE_DESCRIPTION(DM_NAME " delay target");
392 MODULE_AUTHOR("Heinz Mauelshagen <mauelshagen@redhat.com>");
393 MODULE_LICENSE("GPL");