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