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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * Copyright (C) 2005-2007 Red Hat GmbH4 *5 * A target that delays reads and/or writes and can send6 * 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 22struct delay_class {23 struct dm_dev *dev;24 sector_t start;25 unsigned int delay;26 unsigned int ops;27};28 29struct delay_c {30 struct timer_list delay_timer;31 struct mutex process_bios_lock; /* hold while removing bios to be processed from list */32 spinlock_t delayed_bios_lock; /* hold on all accesses to delayed_bios list */33 struct workqueue_struct *kdelayd_wq;34 struct work_struct flush_expired_bios;35 struct list_head delayed_bios;36 struct task_struct *worker;37 bool may_delay;38 39 struct delay_class read;40 struct delay_class write;41 struct delay_class flush;42 43 int argc;44};45 46struct dm_delay_info {47 struct delay_c *context;48 struct delay_class *class;49 struct list_head list;50 unsigned long expires;51};52 53static void handle_delayed_timer(struct timer_list *t)54{55 struct delay_c *dc = from_timer(dc, t, delay_timer);56 57 queue_work(dc->kdelayd_wq, &dc->flush_expired_bios);58}59 60static void queue_timeout(struct delay_c *dc, unsigned long expires)61{62 timer_reduce(&dc->delay_timer, expires);63}64 65static inline bool delay_is_fast(struct delay_c *dc)66{67 return !!dc->worker;68}69 70static void flush_bios(struct bio *bio)71{72 struct bio *n;73 74 while (bio) {75 n = bio->bi_next;76 bio->bi_next = NULL;77 dm_submit_bio_remap(bio, NULL);78 bio = n;79 }80}81 82static void flush_delayed_bios(struct delay_c *dc, bool flush_all)83{84 struct dm_delay_info *delayed, *next;85 struct bio_list flush_bio_list;86 LIST_HEAD(local_list);87 unsigned long next_expires = 0;88 bool start_timer = false;89 bio_list_init(&flush_bio_list);90 91 mutex_lock(&dc->process_bios_lock);92 spin_lock(&dc->delayed_bios_lock);93 list_replace_init(&dc->delayed_bios, &local_list);94 spin_unlock(&dc->delayed_bios_lock);95 list_for_each_entry_safe(delayed, next, &local_list, list) {96 cond_resched();97 if (flush_all || time_after_eq(jiffies, delayed->expires)) {98 struct bio *bio = dm_bio_from_per_bio_data(delayed,99 sizeof(struct dm_delay_info));100 list_del(&delayed->list);101 bio_list_add(&flush_bio_list, bio);102 delayed->class->ops--;103 continue;104 }105 106 if (!delay_is_fast(dc)) {107 if (!start_timer) {108 start_timer = true;109 next_expires = delayed->expires;110 } else {111 next_expires = min(next_expires, delayed->expires);112 }113 }114 }115 spin_lock(&dc->delayed_bios_lock);116 list_splice(&local_list, &dc->delayed_bios);117 spin_unlock(&dc->delayed_bios_lock);118 mutex_unlock(&dc->process_bios_lock);119 120 if (start_timer)121 queue_timeout(dc, next_expires);122 123 flush_bios(bio_list_get(&flush_bio_list));124}125 126static int flush_worker_fn(void *data)127{128 struct delay_c *dc = data;129 130 while (!kthread_should_stop()) {131 flush_delayed_bios(dc, false);132 spin_lock(&dc->delayed_bios_lock);133 if (unlikely(list_empty(&dc->delayed_bios))) {134 set_current_state(TASK_INTERRUPTIBLE);135 spin_unlock(&dc->delayed_bios_lock);136 schedule();137 } else {138 spin_unlock(&dc->delayed_bios_lock);139 cond_resched();140 }141 }142 143 return 0;144}145 146static void flush_expired_bios(struct work_struct *work)147{148 struct delay_c *dc;149 150 dc = container_of(work, struct delay_c, flush_expired_bios);151 flush_delayed_bios(dc, false);152}153 154static void delay_dtr(struct dm_target *ti)155{156 struct delay_c *dc = ti->private;157 158 if (dc->kdelayd_wq) {159 timer_shutdown_sync(&dc->delay_timer);160 destroy_workqueue(dc->kdelayd_wq);161 }162 163 if (dc->read.dev)164 dm_put_device(ti, dc->read.dev);165 if (dc->write.dev)166 dm_put_device(ti, dc->write.dev);167 if (dc->flush.dev)168 dm_put_device(ti, dc->flush.dev);169 if (dc->worker)170 kthread_stop(dc->worker);171 172 mutex_destroy(&dc->process_bios_lock);173 174 kfree(dc);175}176 177static int delay_class_ctr(struct dm_target *ti, struct delay_class *c, char **argv)178{179 int ret;180 unsigned long long tmpll;181 char dummy;182 183 if (sscanf(argv[1], "%llu%c", &tmpll, &dummy) != 1 || tmpll != (sector_t)tmpll) {184 ti->error = "Invalid device sector";185 return -EINVAL;186 }187 c->start = tmpll;188 189 if (sscanf(argv[2], "%u%c", &c->delay, &dummy) != 1) {190 ti->error = "Invalid delay";191 return -EINVAL;192 }193 194 ret = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &c->dev);195 if (ret) {196 ti->error = "Device lookup failed";197 return ret;198 }199 200 return 0;201}202 203/*204 * Mapping parameters:205 * <device> <offset> <delay> [<write_device> <write_offset> <write_delay>]206 *207 * With separate write parameters, the first set is only used for reads.208 * Offsets are specified in sectors.209 * Delays are specified in milliseconds.210 */211static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv)212{213 struct delay_c *dc;214 int ret;215 unsigned int max_delay;216 217 if (argc != 3 && argc != 6 && argc != 9) {218 ti->error = "Requires exactly 3, 6 or 9 arguments";219 return -EINVAL;220 }221 222 dc = kzalloc(sizeof(*dc), GFP_KERNEL);223 if (!dc) {224 ti->error = "Cannot allocate context";225 return -ENOMEM;226 }227 228 ti->private = dc;229 INIT_LIST_HEAD(&dc->delayed_bios);230 mutex_init(&dc->process_bios_lock);231 spin_lock_init(&dc->delayed_bios_lock);232 dc->may_delay = true;233 dc->argc = argc;234 235 ret = delay_class_ctr(ti, &dc->read, argv);236 if (ret)237 goto bad;238 max_delay = dc->read.delay;239 240 if (argc == 3) {241 ret = delay_class_ctr(ti, &dc->write, argv);242 if (ret)243 goto bad;244 ret = delay_class_ctr(ti, &dc->flush, argv);245 if (ret)246 goto bad;247 goto out;248 }249 250 ret = delay_class_ctr(ti, &dc->write, argv + 3);251 if (ret)252 goto bad;253 max_delay = max(max_delay, dc->write.delay);254 255 if (argc == 6) {256 ret = delay_class_ctr(ti, &dc->flush, argv + 3);257 if (ret)258 goto bad;259 goto out;260 }261 262 ret = delay_class_ctr(ti, &dc->flush, argv + 6);263 if (ret)264 goto bad;265 max_delay = max(max_delay, dc->flush.delay);266 267out:268 if (max_delay < 50) {269 /*270 * In case of small requested delays, use kthread instead of271 * timers and workqueue to achieve better latency.272 */273 dc->worker = kthread_run(&flush_worker_fn, dc, "dm-delay-flush-worker");274 if (IS_ERR(dc->worker)) {275 ret = PTR_ERR(dc->worker);276 dc->worker = NULL;277 goto bad;278 }279 } else {280 timer_setup(&dc->delay_timer, handle_delayed_timer, 0);281 INIT_WORK(&dc->flush_expired_bios, flush_expired_bios);282 dc->kdelayd_wq = alloc_workqueue("kdelayd", WQ_MEM_RECLAIM, 0);283 if (!dc->kdelayd_wq) {284 ret = -EINVAL;285 DMERR("Couldn't start kdelayd");286 goto bad;287 }288 }289 290 ti->num_flush_bios = 1;291 ti->num_discard_bios = 1;292 ti->accounts_remapped_io = true;293 ti->per_io_data_size = sizeof(struct dm_delay_info);294 return 0;295 296bad:297 delay_dtr(ti);298 return ret;299}300 301static int delay_bio(struct delay_c *dc, struct delay_class *c, struct bio *bio)302{303 struct dm_delay_info *delayed;304 unsigned long expires = 0;305 306 if (!c->delay)307 return DM_MAPIO_REMAPPED;308 309 delayed = dm_per_bio_data(bio, sizeof(struct dm_delay_info));310 311 delayed->context = dc;312 delayed->expires = expires = jiffies + msecs_to_jiffies(c->delay);313 314 spin_lock(&dc->delayed_bios_lock);315 if (unlikely(!dc->may_delay)) {316 spin_unlock(&dc->delayed_bios_lock);317 return DM_MAPIO_REMAPPED;318 }319 c->ops++;320 list_add_tail(&delayed->list, &dc->delayed_bios);321 spin_unlock(&dc->delayed_bios_lock);322 323 if (delay_is_fast(dc))324 wake_up_process(dc->worker);325 else326 queue_timeout(dc, expires);327 328 return DM_MAPIO_SUBMITTED;329}330 331static void delay_presuspend(struct dm_target *ti)332{333 struct delay_c *dc = ti->private;334 335 spin_lock(&dc->delayed_bios_lock);336 dc->may_delay = false;337 spin_unlock(&dc->delayed_bios_lock);338 339 if (!delay_is_fast(dc))340 timer_delete(&dc->delay_timer);341 flush_delayed_bios(dc, true);342}343 344static void delay_resume(struct dm_target *ti)345{346 struct delay_c *dc = ti->private;347 348 dc->may_delay = true;349}350 351static int delay_map(struct dm_target *ti, struct bio *bio)352{353 struct delay_c *dc = ti->private;354 struct delay_class *c;355 struct dm_delay_info *delayed = dm_per_bio_data(bio, sizeof(struct dm_delay_info));356 357 if (bio_data_dir(bio) == WRITE) {358 if (unlikely(bio->bi_opf & REQ_PREFLUSH))359 c = &dc->flush;360 else361 c = &dc->write;362 } else {363 c = &dc->read;364 }365 delayed->class = c;366 bio_set_dev(bio, c->dev->bdev);367 bio->bi_iter.bi_sector = c->start + dm_target_offset(ti, bio->bi_iter.bi_sector);368 369 return delay_bio(dc, c, bio);370}371 372#define DMEMIT_DELAY_CLASS(c) \373 DMEMIT("%s %llu %u", (c)->dev->name, (unsigned long long)(c)->start, (c)->delay)374 375static void delay_status(struct dm_target *ti, status_type_t type,376 unsigned int status_flags, char *result, unsigned int maxlen)377{378 struct delay_c *dc = ti->private;379 int sz = 0;380 381 switch (type) {382 case STATUSTYPE_INFO:383 DMEMIT("%u %u %u", dc->read.ops, dc->write.ops, dc->flush.ops);384 break;385 386 case STATUSTYPE_TABLE:387 DMEMIT_DELAY_CLASS(&dc->read);388 if (dc->argc >= 6) {389 DMEMIT(" ");390 DMEMIT_DELAY_CLASS(&dc->write);391 }392 if (dc->argc >= 9) {393 DMEMIT(" ");394 DMEMIT_DELAY_CLASS(&dc->flush);395 }396 break;397 398 case STATUSTYPE_IMA:399 *result = '\0';400 break;401 }402}403 404static int delay_iterate_devices(struct dm_target *ti,405 iterate_devices_callout_fn fn, void *data)406{407 struct delay_c *dc = ti->private;408 int ret = 0;409 410 ret = fn(ti, dc->read.dev, dc->read.start, ti->len, data);411 if (ret)412 goto out;413 ret = fn(ti, dc->write.dev, dc->write.start, ti->len, data);414 if (ret)415 goto out;416 ret = fn(ti, dc->flush.dev, dc->flush.start, ti->len, data);417 if (ret)418 goto out;419 420out:421 return ret;422}423 424static struct target_type delay_target = {425 .name = "delay",426 .version = {1, 4, 0},427 .features = DM_TARGET_PASSES_INTEGRITY,428 .module = THIS_MODULE,429 .ctr = delay_ctr,430 .dtr = delay_dtr,431 .map = delay_map,432 .presuspend = delay_presuspend,433 .resume = delay_resume,434 .status = delay_status,435 .iterate_devices = delay_iterate_devices,436};437module_dm(delay);438 439MODULE_DESCRIPTION(DM_NAME " delay target");440MODULE_AUTHOR("Heinz Mauelshagen <mauelshagen@redhat.com>");441MODULE_LICENSE("GPL");442