1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (C) 2005-2007 Red Hat GmbH
4 *
5 * A target that delays reads and/or writes and can send
6 * them to different devices.
7 *
8 * This file is released under the GPL.
9 */
10
11#include <linux/module.h>
12#include <linux/init.h>
13#include <linux/blkdev.h>
14#include <linux/bio.h>
15#include <linux/slab.h>
16#include <linux/kthread.h>
17#include <linux/delay.h>
18
19#include <linux/device-mapper.h>
20
21#define DM_MSG_PREFIX "delay"
22
23#define SLEEP_SHIFT 3
24
25struct delay_class {
26 struct dm_dev *dev;
27 sector_t start;
28 unsigned int delay;
29 unsigned int ops;
30};
31
32struct delay_c {
33 struct timer_list delay_timer;
34 struct mutex process_bios_lock; /* hold while removing bios to be processed from list */
35 spinlock_t delayed_bios_lock; /* hold on all accesses to delayed_bios list */
36 struct workqueue_struct *kdelayd_wq;
37 struct work_struct flush_expired_bios;
38 struct list_head delayed_bios;
39 struct task_struct *worker;
40 unsigned int worker_sleep_us;
41 bool may_delay;
42
43 struct delay_class read;
44 struct delay_class write;
45 struct delay_class flush;
46
47 int argc;
48};
49
50struct dm_delay_info {
51 struct delay_c *context;
52 struct delay_class *class;
53 struct list_head list;
54 unsigned long expires;
55};
56
57static void handle_delayed_timer(struct timer_list *t)
58{
59 struct delay_c *dc = timer_container_of(dc, t, delay_timer);
60
61 queue_work(wq: dc->kdelayd_wq, work: &dc->flush_expired_bios);
62}
63
64static void queue_timeout(struct delay_c *dc, unsigned long expires)
65{
66 timer_reduce(timer: &dc->delay_timer, expires);
67}
68
69static inline bool delay_is_fast(struct delay_c *dc)
70{
71 return !!dc->worker;
72}
73
74static void flush_bios(struct bio *bio)
75{
76 struct bio *n;
77
78 while (bio) {
79 n = bio->bi_next;
80 bio->bi_next = NULL;
81 dm_submit_bio_remap(clone: bio, NULL);
82 bio = n;
83 }
84}
85
86static void flush_delayed_bios(struct delay_c *dc, bool flush_all)
87{
88 struct dm_delay_info *delayed, *next;
89 struct bio_list flush_bio_list;
90 LIST_HEAD(local_list);
91 unsigned long next_expires = 0;
92 bool start_timer = false;
93 bio_list_init(bl: &flush_bio_list);
94
95 mutex_lock(&dc->process_bios_lock);
96 spin_lock(lock: &dc->delayed_bios_lock);
97 list_replace_init(old: &dc->delayed_bios, new: &local_list);
98 spin_unlock(lock: &dc->delayed_bios_lock);
99 list_for_each_entry_safe(delayed, next, &local_list, list) {
100 cond_resched();
101 if (flush_all || time_after_eq(jiffies, delayed->expires)) {
102 struct bio *bio = dm_bio_from_per_bio_data(data: delayed,
103 data_size: sizeof(struct dm_delay_info));
104 list_del(entry: &delayed->list);
105 bio_list_add(bl: &flush_bio_list, bio);
106 delayed->class->ops--;
107 continue;
108 }
109
110 if (!delay_is_fast(dc)) {
111 if (!start_timer) {
112 start_timer = true;
113 next_expires = delayed->expires;
114 } else {
115 next_expires = min(next_expires, delayed->expires);
116 }
117 }
118 }
119 spin_lock(lock: &dc->delayed_bios_lock);
120 list_splice(list: &local_list, head: &dc->delayed_bios);
121 spin_unlock(lock: &dc->delayed_bios_lock);
122 mutex_unlock(lock: &dc->process_bios_lock);
123
124 if (start_timer)
125 queue_timeout(dc, expires: next_expires);
126
127 flush_bios(bio: bio_list_get(bl: &flush_bio_list));
128}
129
130static int flush_worker_fn(void *data)
131{
132 struct delay_c *dc = data;
133
134 while (!kthread_should_stop()) {
135 flush_delayed_bios(dc, flush_all: false);
136 spin_lock(lock: &dc->delayed_bios_lock);
137 if (unlikely(list_empty(&dc->delayed_bios))) {
138 set_current_state(TASK_INTERRUPTIBLE);
139 spin_unlock(lock: &dc->delayed_bios_lock);
140 schedule();
141 } else {
142 spin_unlock(lock: &dc->delayed_bios_lock);
143 fsleep(usecs: dc->worker_sleep_us);
144 cond_resched();
145 }
146 }
147
148 return 0;
149}
150
151static void flush_expired_bios(struct work_struct *work)
152{
153 struct delay_c *dc;
154
155 dc = container_of(work, struct delay_c, flush_expired_bios);
156 flush_delayed_bios(dc, flush_all: false);
157}
158
159static void delay_dtr(struct dm_target *ti)
160{
161 struct delay_c *dc = ti->private;
162
163 if (dc->kdelayd_wq) {
164 timer_shutdown_sync(timer: &dc->delay_timer);
165 destroy_workqueue(wq: dc->kdelayd_wq);
166 }
167
168 if (dc->read.dev)
169 dm_put_device(ti, d: dc->read.dev);
170 if (dc->write.dev)
171 dm_put_device(ti, d: dc->write.dev);
172 if (dc->flush.dev)
173 dm_put_device(ti, d: dc->flush.dev);
174 if (dc->worker)
175 kthread_stop(k: dc->worker);
176
177 mutex_destroy(lock: &dc->process_bios_lock);
178
179 kfree(objp: dc);
180}
181
182static int delay_class_ctr(struct dm_target *ti, struct delay_class *c, char **argv)
183{
184 int ret;
185 unsigned long long tmpll;
186 char dummy;
187
188 if (sscanf(argv[1], "%llu%c", &tmpll, &dummy) != 1 || tmpll != (sector_t)tmpll) {
189 ti->error = "Invalid device sector";
190 return -EINVAL;
191 }
192 c->start = tmpll;
193
194 if (sscanf(argv[2], "%u%c", &c->delay, &dummy) != 1) {
195 ti->error = "Invalid delay";
196 return -EINVAL;
197 }
198
199 ret = dm_get_device(ti, path: argv[0], mode: dm_table_get_mode(t: ti->table), result: &c->dev);
200 if (ret) {
201 ti->error = "Device lookup failed";
202 return ret;
203 }
204
205 return 0;
206}
207
208/*
209 * Mapping parameters:
210 * <device> <offset> <delay> [<write_device> <write_offset> <write_delay>]
211 *
212 * With separate write parameters, the first set is only used for reads.
213 * Offsets are specified in sectors.
214 * Delays are specified in milliseconds.
215 */
216static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv)
217{
218 struct delay_c *dc;
219 int ret;
220 unsigned int max_delay, min_delay;
221
222 if (argc != 3 && argc != 6 && argc != 9) {
223 ti->error = "Requires exactly 3, 6 or 9 arguments";
224 return -EINVAL;
225 }
226
227 dc = kzalloc(sizeof(*dc), GFP_KERNEL);
228 if (!dc) {
229 ti->error = "Cannot allocate context";
230 return -ENOMEM;
231 }
232
233 ti->private = dc;
234 INIT_LIST_HEAD(list: &dc->delayed_bios);
235 mutex_init(&dc->process_bios_lock);
236 spin_lock_init(&dc->delayed_bios_lock);
237 dc->may_delay = true;
238 dc->argc = argc;
239
240 ret = delay_class_ctr(ti, c: &dc->read, argv);
241 if (ret)
242 goto bad;
243 min_delay = max_delay = dc->read.delay;
244
245 if (argc == 3) {
246 ret = delay_class_ctr(ti, c: &dc->write, argv);
247 if (ret)
248 goto bad;
249 ret = delay_class_ctr(ti, c: &dc->flush, argv);
250 if (ret)
251 goto bad;
252 goto out;
253 }
254
255 ret = delay_class_ctr(ti, c: &dc->write, argv: argv + 3);
256 if (ret)
257 goto bad;
258 max_delay = max(max_delay, dc->write.delay);
259 min_delay = min_not_zero(min_delay, dc->write.delay);
260
261 if (argc == 6) {
262 ret = delay_class_ctr(ti, c: &dc->flush, argv: argv + 3);
263 if (ret)
264 goto bad;
265 goto out;
266 }
267
268 ret = delay_class_ctr(ti, c: &dc->flush, argv: argv + 6);
269 if (ret)
270 goto bad;
271 max_delay = max(max_delay, dc->flush.delay);
272 min_delay = min_not_zero(min_delay, dc->flush.delay);
273
274out:
275 if (max_delay < 50) {
276 if (min_delay >> SLEEP_SHIFT)
277 dc->worker_sleep_us = 1000;
278 else
279 dc->worker_sleep_us = (min_delay * 1000) >> SLEEP_SHIFT;
280 /*
281 * In case of small requested delays, use kthread instead of
282 * timers and workqueue to achieve better latency.
283 */
284 dc->worker = kthread_run(&flush_worker_fn, dc, "dm-delay-flush-worker");
285 if (IS_ERR(ptr: dc->worker)) {
286 ret = PTR_ERR(ptr: dc->worker);
287 dc->worker = NULL;
288 goto bad;
289 }
290 } else {
291 timer_setup(&dc->delay_timer, handle_delayed_timer, 0);
292 INIT_WORK(&dc->flush_expired_bios, flush_expired_bios);
293 dc->kdelayd_wq = alloc_workqueue("kdelayd", WQ_MEM_RECLAIM, 0);
294 if (!dc->kdelayd_wq) {
295 ret = -EINVAL;
296 DMERR("Couldn't start kdelayd");
297 goto bad;
298 }
299 }
300
301 ti->num_flush_bios = 1;
302 ti->num_discard_bios = 1;
303 ti->accounts_remapped_io = true;
304 ti->per_io_data_size = sizeof(struct dm_delay_info);
305 return 0;
306
307bad:
308 delay_dtr(ti);
309 return ret;
310}
311
312static int delay_bio(struct delay_c *dc, struct delay_class *c, struct bio *bio)
313{
314 struct dm_delay_info *delayed;
315 unsigned long expires = 0;
316
317 if (!c->delay)
318 return DM_MAPIO_REMAPPED;
319
320 delayed = dm_per_bio_data(bio, data_size: sizeof(struct dm_delay_info));
321
322 delayed->context = dc;
323 delayed->expires = expires = jiffies + msecs_to_jiffies(m: c->delay);
324
325 spin_lock(lock: &dc->delayed_bios_lock);
326 if (unlikely(!dc->may_delay)) {
327 spin_unlock(lock: &dc->delayed_bios_lock);
328 return DM_MAPIO_REMAPPED;
329 }
330 c->ops++;
331 list_add_tail(new: &delayed->list, head: &dc->delayed_bios);
332 spin_unlock(lock: &dc->delayed_bios_lock);
333
334 if (delay_is_fast(dc))
335 wake_up_process(tsk: dc->worker);
336 else
337 queue_timeout(dc, expires);
338
339 return DM_MAPIO_SUBMITTED;
340}
341
342static void delay_presuspend(struct dm_target *ti)
343{
344 struct delay_c *dc = ti->private;
345
346 spin_lock(lock: &dc->delayed_bios_lock);
347 dc->may_delay = false;
348 spin_unlock(lock: &dc->delayed_bios_lock);
349
350 if (!delay_is_fast(dc))
351 timer_delete(timer: &dc->delay_timer);
352 flush_delayed_bios(dc, flush_all: true);
353}
354
355static void delay_resume(struct dm_target *ti)
356{
357 struct delay_c *dc = ti->private;
358
359 dc->may_delay = true;
360}
361
362static int delay_map(struct dm_target *ti, struct bio *bio)
363{
364 struct delay_c *dc = ti->private;
365 struct delay_class *c;
366 struct dm_delay_info *delayed = dm_per_bio_data(bio, data_size: sizeof(struct dm_delay_info));
367
368 if (bio_data_dir(bio) == WRITE) {
369 if (unlikely(bio->bi_opf & REQ_PREFLUSH))
370 c = &dc->flush;
371 else
372 c = &dc->write;
373 } else {
374 c = &dc->read;
375 }
376 delayed->class = c;
377 bio_set_dev(bio, bdev: c->dev->bdev);
378 bio->bi_iter.bi_sector = c->start + dm_target_offset(ti, bio->bi_iter.bi_sector);
379
380 return delay_bio(dc, c, bio);
381}
382
383#ifdef CONFIG_BLK_DEV_ZONED
384static int delay_report_zones(struct dm_target *ti,
385 struct dm_report_zones_args *args, unsigned int nr_zones)
386{
387 struct delay_c *dc = ti->private;
388 struct delay_class *c = &dc->read;
389
390 return dm_report_zones(bdev: c->dev->bdev, start: c->start,
391 sector: c->start + dm_target_offset(ti, args->next_sector),
392 args, nr_zones);
393}
394#else
395#define delay_report_zones NULL
396#endif
397
398#define DMEMIT_DELAY_CLASS(c) \
399 DMEMIT("%s %llu %u", (c)->dev->name, (unsigned long long)(c)->start, (c)->delay)
400
401static void delay_status(struct dm_target *ti, status_type_t type,
402 unsigned int status_flags, char *result, unsigned int maxlen)
403{
404 struct delay_c *dc = ti->private;
405 int sz = 0;
406
407 switch (type) {
408 case STATUSTYPE_INFO:
409 DMEMIT("%u %u %u", dc->read.ops, dc->write.ops, dc->flush.ops);
410 break;
411
412 case STATUSTYPE_TABLE:
413 DMEMIT_DELAY_CLASS(&dc->read);
414 if (dc->argc >= 6) {
415 DMEMIT(" ");
416 DMEMIT_DELAY_CLASS(&dc->write);
417 }
418 if (dc->argc >= 9) {
419 DMEMIT(" ");
420 DMEMIT_DELAY_CLASS(&dc->flush);
421 }
422 break;
423
424 case STATUSTYPE_IMA:
425 *result = '\0';
426 break;
427 }
428}
429
430static int delay_iterate_devices(struct dm_target *ti,
431 iterate_devices_callout_fn fn, void *data)
432{
433 struct delay_c *dc = ti->private;
434 int ret = 0;
435
436 ret = fn(ti, dc->read.dev, dc->read.start, ti->len, data);
437 if (ret)
438 goto out;
439 ret = fn(ti, dc->write.dev, dc->write.start, ti->len, data);
440 if (ret)
441 goto out;
442 ret = fn(ti, dc->flush.dev, dc->flush.start, ti->len, data);
443 if (ret)
444 goto out;
445
446out:
447 return ret;
448}
449
450static struct target_type delay_target = {
451 .name = "delay",
452 .version = {1, 5, 0},
453 .features = DM_TARGET_PASSES_INTEGRITY | DM_TARGET_ZONED_HM,
454 .module = THIS_MODULE,
455 .ctr = delay_ctr,
456 .dtr = delay_dtr,
457 .map = delay_map,
458 .report_zones = delay_report_zones,
459 .presuspend = delay_presuspend,
460 .resume = delay_resume,
461 .status = delay_status,
462 .iterate_devices = delay_iterate_devices,
463};
464module_dm(delay);
465
466MODULE_DESCRIPTION(DM_NAME " delay target");
467MODULE_AUTHOR("Heinz Mauelshagen <mauelshagen@redhat.com>");
468MODULE_LICENSE("GPL");
469

source code of linux/drivers/md/dm-delay.c