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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * multipath.c : Multiple Devices driver for Linux
4 *
5 * Copyright (C) 1999, 2000, 2001 Ingo Molnar, Red Hat
6 *
7 * Copyright (C) 1996, 1997, 1998 Ingo Molnar, Miguel de Icaza, Gadi Oxman
8 *
9 * MULTIPATH management functions.
10 *
11 * derived from raid1.c.
12 */
13
14#include <linux/blkdev.h>
15#include <linux/module.h>
16#include <linux/raid/md_u.h>
17#include <linux/seq_file.h>
18#include <linux/slab.h>
19#include "md.h"
20#include "md-multipath.h"
21
22#define MAX_WORK_PER_DISK 128
23
24#define NR_RESERVED_BUFS 32
25
26static int multipath_map (struct mpconf *conf)
27{
28 int i, disks = conf->raid_disks;
29
30 /*
31 * Later we do read balancing on the read side
32 * now we use the first available disk.
33 */
34
35 rcu_read_lock();
36 for (i = 0; i < disks; i++) {
37 struct md_rdev *rdev = rcu_dereference(conf->multipaths[i].rdev);
38 if (rdev && test_bit(In_sync, &rdev->flags) &&
39 !test_bit(Faulty, &rdev->flags)) {
40 atomic_inc(&rdev->nr_pending);
41 rcu_read_unlock();
42 return i;
43 }
44 }
45 rcu_read_unlock();
46
47 pr_crit_ratelimited("multipath_map(): no more operational IO paths?\n");
48 return (-1);
49}
50
51static void multipath_reschedule_retry (struct multipath_bh *mp_bh)
52{
53 unsigned long flags;
54 struct mddev *mddev = mp_bh->mddev;
55 struct mpconf *conf = mddev->private;
56
57 spin_lock_irqsave(&conf->device_lock, flags);
58 list_add(&mp_bh->retry_list, &conf->retry_list);
59 spin_unlock_irqrestore(&conf->device_lock, flags);
60 md_wakeup_thread(mddev->thread);
61}
62
63/*
64 * multipath_end_bh_io() is called when we have finished servicing a multipathed
65 * operation and are ready to return a success/failure code to the buffer
66 * cache layer.
67 */
68static void multipath_end_bh_io(struct multipath_bh *mp_bh, blk_status_t status)
69{
70 struct bio *bio = mp_bh->master_bio;
71 struct mpconf *conf = mp_bh->mddev->private;
72
73 bio->bi_status = status;
74 bio_endio(bio);
75 mempool_free(mp_bh, &conf->pool);
76}
77
78static void multipath_end_request(struct bio *bio)
79{
80 struct multipath_bh *mp_bh = bio->bi_private;
81 struct mpconf *conf = mp_bh->mddev->private;
82 struct md_rdev *rdev = conf->multipaths[mp_bh->path].rdev;
83
84 if (!bio->bi_status)
85 multipath_end_bh_io(mp_bh, 0);
86 else if (!(bio->bi_opf & REQ_RAHEAD)) {
87 /*
88 * oops, IO error:
89 */
90 md_error (mp_bh->mddev, rdev);
91 pr_info("multipath: %pg: rescheduling sector %llu\n",
92 rdev->bdev,
93 (unsigned long long)bio->bi_iter.bi_sector);
94 multipath_reschedule_retry(mp_bh);
95 } else
96 multipath_end_bh_io(mp_bh, bio->bi_status);
97 rdev_dec_pending(rdev, conf->mddev);
98}
99
100static bool multipath_make_request(struct mddev *mddev, struct bio * bio)
101{
102 struct mpconf *conf = mddev->private;
103 struct multipath_bh * mp_bh;
104 struct multipath_info *multipath;
105
106 if (unlikely(bio->bi_opf & REQ_PREFLUSH)
107 && md_flush_request(mddev, bio))
108 return true;
109
110 mp_bh = mempool_alloc(&conf->pool, GFP_NOIO);
111
112 mp_bh->master_bio = bio;
113 mp_bh->mddev = mddev;
114
115 mp_bh->path = multipath_map(conf);
116 if (mp_bh->path < 0) {
117 bio_io_error(bio);
118 mempool_free(mp_bh, &conf->pool);
119 return true;
120 }
121 multipath = conf->multipaths + mp_bh->path;
122
123 bio_init_clone(multipath->rdev->bdev, &mp_bh->bio, bio, GFP_NOIO);
124
125 mp_bh->bio.bi_iter.bi_sector += multipath->rdev->data_offset;
126 mp_bh->bio.bi_opf |= REQ_FAILFAST_TRANSPORT;
127 mp_bh->bio.bi_end_io = multipath_end_request;
128 mp_bh->bio.bi_private = mp_bh;
129 mddev_check_write_zeroes(mddev, &mp_bh->bio);
130 submit_bio_noacct(&mp_bh->bio);
131 return true;
132}
133
134static void multipath_status(struct seq_file *seq, struct mddev *mddev)
135{
136 struct mpconf *conf = mddev->private;
137 int i;
138
139 seq_printf (seq, " [%d/%d] [", conf->raid_disks,
140 conf->raid_disks - mddev->degraded);
141 rcu_read_lock();
142 for (i = 0; i < conf->raid_disks; i++) {
143 struct md_rdev *rdev = rcu_dereference(conf->multipaths[i].rdev);
144 seq_printf (seq, "%s", rdev && test_bit(In_sync, &rdev->flags) ? "U" : "_");
145 }
146 rcu_read_unlock();
147 seq_putc(seq, ']');
148}
149
150/*
151 * Careful, this can execute in IRQ contexts as well!
152 */
153static void multipath_error (struct mddev *mddev, struct md_rdev *rdev)
154{
155 struct mpconf *conf = mddev->private;
156
157 if (conf->raid_disks - mddev->degraded <= 1) {
158 /*
159 * Uh oh, we can do nothing if this is our last path, but
160 * first check if this is a queued request for a device
161 * which has just failed.
162 */
163 pr_warn("multipath: only one IO path left and IO error.\n");
164 /* leave it active... it's all we have */
165 return;
166 }
167 /*
168 * Mark disk as unusable
169 */
170 if (test_and_clear_bit(In_sync, &rdev->flags)) {
171 unsigned long flags;
172 spin_lock_irqsave(&conf->device_lock, flags);
173 mddev->degraded++;
174 spin_unlock_irqrestore(&conf->device_lock, flags);
175 }
176 set_bit(Faulty, &rdev->flags);
177 set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags);
178 pr_err("multipath: IO failure on %pg, disabling IO path.\n"
179 "multipath: Operation continuing on %d IO paths.\n",
180 rdev->bdev,
181 conf->raid_disks - mddev->degraded);
182}
183
184static void print_multipath_conf (struct mpconf *conf)
185{
186 int i;
187 struct multipath_info *tmp;
188
189 pr_debug("MULTIPATH conf printout:\n");
190 if (!conf) {
191 pr_debug("(conf==NULL)\n");
192 return;
193 }
194 pr_debug(" --- wd:%d rd:%d\n", conf->raid_disks - conf->mddev->degraded,
195 conf->raid_disks);
196
197 for (i = 0; i < conf->raid_disks; i++) {
198 tmp = conf->multipaths + i;
199 if (tmp->rdev)
200 pr_debug(" disk%d, o:%d, dev:%pg\n",
201 i,!test_bit(Faulty, &tmp->rdev->flags),
202 tmp->rdev->bdev);
203 }
204}
205
206static int multipath_add_disk(struct mddev *mddev, struct md_rdev *rdev)
207{
208 struct mpconf *conf = mddev->private;
209 int err = -EEXIST;
210 int path;
211 struct multipath_info *p;
212 int first = 0;
213 int last = mddev->raid_disks - 1;
214
215 if (rdev->raid_disk >= 0)
216 first = last = rdev->raid_disk;
217
218 print_multipath_conf(conf);
219
220 for (path = first; path <= last; path++)
221 if ((p=conf->multipaths+path)->rdev == NULL) {
222 disk_stack_limits(mddev->gendisk, rdev->bdev,
223 rdev->data_offset << 9);
224
225 err = md_integrity_add_rdev(rdev, mddev);
226 if (err)
227 break;
228 spin_lock_irq(&conf->device_lock);
229 mddev->degraded--;
230 rdev->raid_disk = path;
231 set_bit(In_sync, &rdev->flags);
232 spin_unlock_irq(&conf->device_lock);
233 rcu_assign_pointer(p->rdev, rdev);
234 err = 0;
235 break;
236 }
237
238 print_multipath_conf(conf);
239
240 return err;
241}
242
243static int multipath_remove_disk(struct mddev *mddev, struct md_rdev *rdev)
244{
245 struct mpconf *conf = mddev->private;
246 int err = 0;
247 int number = rdev->raid_disk;
248 struct multipath_info *p = conf->multipaths + number;
249
250 print_multipath_conf(conf);
251
252 if (rdev == p->rdev) {
253 if (test_bit(In_sync, &rdev->flags) ||
254 atomic_read(&rdev->nr_pending)) {
255 pr_warn("hot-remove-disk, slot %d is identified but is still operational!\n", number);
256 err = -EBUSY;
257 goto abort;
258 }
259 p->rdev = NULL;
260 if (!test_bit(RemoveSynchronized, &rdev->flags)) {
261 synchronize_rcu();
262 if (atomic_read(&rdev->nr_pending)) {
263 /* lost the race, try later */
264 err = -EBUSY;
265 p->rdev = rdev;
266 goto abort;
267 }
268 }
269 err = md_integrity_register(mddev);
270 }
271abort:
272
273 print_multipath_conf(conf);
274 return err;
275}
276
277/*
278 * This is a kernel thread which:
279 *
280 * 1. Retries failed read operations on working multipaths.
281 * 2. Updates the raid superblock when problems encounter.
282 * 3. Performs writes following reads for array syncronising.
283 */
284
285static void multipathd(struct md_thread *thread)
286{
287 struct mddev *mddev = thread->mddev;
288 struct multipath_bh *mp_bh;
289 struct bio *bio;
290 unsigned long flags;
291 struct mpconf *conf = mddev->private;
292 struct list_head *head = &conf->retry_list;
293
294 md_check_recovery(mddev);
295 for (;;) {
296 spin_lock_irqsave(&conf->device_lock, flags);
297 if (list_empty(head))
298 break;
299 mp_bh = list_entry(head->prev, struct multipath_bh, retry_list);
300 list_del(head->prev);
301 spin_unlock_irqrestore(&conf->device_lock, flags);
302
303 bio = &mp_bh->bio;
304 bio->bi_iter.bi_sector = mp_bh->master_bio->bi_iter.bi_sector;
305
306 if ((mp_bh->path = multipath_map (conf))<0) {
307 pr_err("multipath: %pg: unrecoverable IO read error for block %llu\n",
308 bio->bi_bdev,
309 (unsigned long long)bio->bi_iter.bi_sector);
310 multipath_end_bh_io(mp_bh, BLK_STS_IOERR);
311 } else {
312 pr_err("multipath: %pg: redirecting sector %llu to another IO path\n",
313 bio->bi_bdev,
314 (unsigned long long)bio->bi_iter.bi_sector);
315 *bio = *(mp_bh->master_bio);
316 bio->bi_iter.bi_sector +=
317 conf->multipaths[mp_bh->path].rdev->data_offset;
318 bio_set_dev(bio, conf->multipaths[mp_bh->path].rdev->bdev);
319 bio->bi_opf |= REQ_FAILFAST_TRANSPORT;
320 bio->bi_end_io = multipath_end_request;
321 bio->bi_private = mp_bh;
322 submit_bio_noacct(bio);
323 }
324 }
325 spin_unlock_irqrestore(&conf->device_lock, flags);
326}
327
328static sector_t multipath_size(struct mddev *mddev, sector_t sectors, int raid_disks)
329{
330 WARN_ONCE(sectors || raid_disks,
331 "%s does not support generic reshape\n", __func__);
332
333 return mddev->dev_sectors;
334}
335
336static int multipath_run (struct mddev *mddev)
337{
338 struct mpconf *conf;
339 int disk_idx;
340 struct multipath_info *disk;
341 struct md_rdev *rdev;
342 int working_disks;
343 int ret;
344
345 if (md_check_no_bitmap(mddev))
346 return -EINVAL;
347
348 if (mddev->level != LEVEL_MULTIPATH) {
349 pr_warn("multipath: %s: raid level not set to multipath IO (%d)\n",
350 mdname(mddev), mddev->level);
351 goto out;
352 }
353 /*
354 * copy the already verified devices into our private MULTIPATH
355 * bookkeeping area. [whatever we allocate in multipath_run(),
356 * should be freed in multipath_free()]
357 */
358
359 conf = kzalloc(sizeof(struct mpconf), GFP_KERNEL);
360 mddev->private = conf;
361 if (!conf)
362 goto out;
363
364 conf->multipaths = kcalloc(mddev->raid_disks,
365 sizeof(struct multipath_info),
366 GFP_KERNEL);
367 if (!conf->multipaths)
368 goto out_free_conf;
369
370 working_disks = 0;
371 rdev_for_each(rdev, mddev) {
372 disk_idx = rdev->raid_disk;
373 if (disk_idx < 0 ||
374 disk_idx >= mddev->raid_disks)
375 continue;
376
377 disk = conf->multipaths + disk_idx;
378 disk->rdev = rdev;
379 disk_stack_limits(mddev->gendisk, rdev->bdev,
380 rdev->data_offset << 9);
381
382 if (!test_bit(Faulty, &rdev->flags))
383 working_disks++;
384 }
385
386 conf->raid_disks = mddev->raid_disks;
387 conf->mddev = mddev;
388 spin_lock_init(&conf->device_lock);
389 INIT_LIST_HEAD(&conf->retry_list);
390
391 if (!working_disks) {
392 pr_warn("multipath: no operational IO paths for %s\n",
393 mdname(mddev));
394 goto out_free_conf;
395 }
396 mddev->degraded = conf->raid_disks - working_disks;
397
398 ret = mempool_init_kmalloc_pool(&conf->pool, NR_RESERVED_BUFS,
399 sizeof(struct multipath_bh));
400 if (ret)
401 goto out_free_conf;
402
403 mddev->thread = md_register_thread(multipathd, mddev,
404 "multipath");
405 if (!mddev->thread)
406 goto out_free_conf;
407
408 pr_info("multipath: array %s active with %d out of %d IO paths\n",
409 mdname(mddev), conf->raid_disks - mddev->degraded,
410 mddev->raid_disks);
411 /*
412 * Ok, everything is just fine now
413 */
414 md_set_array_sectors(mddev, multipath_size(mddev, 0, 0));
415
416 if (md_integrity_register(mddev))
417 goto out_free_conf;
418
419 return 0;
420
421out_free_conf:
422 mempool_exit(&conf->pool);
423 kfree(conf->multipaths);
424 kfree(conf);
425 mddev->private = NULL;
426out:
427 return -EIO;
428}
429
430static void multipath_free(struct mddev *mddev, void *priv)
431{
432 struct mpconf *conf = priv;
433
434 mempool_exit(&conf->pool);
435 kfree(conf->multipaths);
436 kfree(conf);
437}
438
439static struct md_personality multipath_personality =
440{
441 .name = "multipath",
442 .level = LEVEL_MULTIPATH,
443 .owner = THIS_MODULE,
444 .make_request = multipath_make_request,
445 .run = multipath_run,
446 .free = multipath_free,
447 .status = multipath_status,
448 .error_handler = multipath_error,
449 .hot_add_disk = multipath_add_disk,
450 .hot_remove_disk= multipath_remove_disk,
451 .size = multipath_size,
452};
453
454static int __init multipath_init (void)
455{
456 return register_md_personality (&multipath_personality);
457}
458
459static void __exit multipath_exit (void)
460{
461 unregister_md_personality (&multipath_personality);
462}
463
464module_init(multipath_init);
465module_exit(multipath_exit);
466MODULE_LICENSE("GPL");
467MODULE_DESCRIPTION("simple multi-path personality for MD (deprecated)");
468MODULE_ALIAS("md-personality-7"); /* MULTIPATH */
469MODULE_ALIAS("md-multipath");
470MODULE_ALIAS("md-level--4");