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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 char b[BDEVNAME_SIZE];
91 md_error (mp_bh->mddev, rdev);
92 pr_info("multipath: %s: rescheduling sector %llu\n",
93 bdevname(rdev->bdev,b),
94 (unsigned long long)bio->bi_iter.bi_sector);
95 multipath_reschedule_retry(mp_bh);
96 } else
97 multipath_end_bh_io(mp_bh, bio->bi_status);
98 rdev_dec_pending(rdev, conf->mddev);
99}
100
101static bool multipath_make_request(struct mddev *mddev, struct bio * bio)
102{
103 struct mpconf *conf = mddev->private;
104 struct multipath_bh * mp_bh;
105 struct multipath_info *multipath;
106
107 if (unlikely(bio->bi_opf & REQ_PREFLUSH)
108 && md_flush_request(mddev, bio))
109 return true;
110
111 mp_bh = mempool_alloc(&conf->pool, GFP_NOIO);
112
113 mp_bh->master_bio = bio;
114 mp_bh->mddev = mddev;
115
116 mp_bh->path = multipath_map(conf);
117 if (mp_bh->path < 0) {
118 bio_io_error(bio);
119 mempool_free(mp_bh, &conf->pool);
120 return true;
121 }
122 multipath = conf->multipaths + mp_bh->path;
123
124 bio_init(&mp_bh->bio, NULL, 0);
125 __bio_clone_fast(&mp_bh->bio, bio);
126
127 mp_bh->bio.bi_iter.bi_sector += multipath->rdev->data_offset;
128 bio_set_dev(&mp_bh->bio, multipath->rdev->bdev);
129 mp_bh->bio.bi_opf |= REQ_FAILFAST_TRANSPORT;
130 mp_bh->bio.bi_end_io = multipath_end_request;
131 mp_bh->bio.bi_private = mp_bh;
132 mddev_check_writesame(mddev, &mp_bh->bio);
133 mddev_check_write_zeroes(mddev, &mp_bh->bio);
134 submit_bio_noacct(&mp_bh->bio);
135 return true;
136}
137
138static void multipath_status(struct seq_file *seq, struct mddev *mddev)
139{
140 struct mpconf *conf = mddev->private;
141 int i;
142
143 seq_printf (seq, " [%d/%d] [", conf->raid_disks,
144 conf->raid_disks - mddev->degraded);
145 rcu_read_lock();
146 for (i = 0; i < conf->raid_disks; i++) {
147 struct md_rdev *rdev = rcu_dereference(conf->multipaths[i].rdev);
148 seq_printf (seq, "%s", rdev && test_bit(In_sync, &rdev->flags) ? "U" : "_");
149 }
150 rcu_read_unlock();
151 seq_putc(seq, ']');
152}
153
154/*
155 * Careful, this can execute in IRQ contexts as well!
156 */
157static void multipath_error (struct mddev *mddev, struct md_rdev *rdev)
158{
159 struct mpconf *conf = mddev->private;
160 char b[BDEVNAME_SIZE];
161
162 if (conf->raid_disks - mddev->degraded <= 1) {
163 /*
164 * Uh oh, we can do nothing if this is our last path, but
165 * first check if this is a queued request for a device
166 * which has just failed.
167 */
168 pr_warn("multipath: only one IO path left and IO error.\n");
169 /* leave it active... it's all we have */
170 return;
171 }
172 /*
173 * Mark disk as unusable
174 */
175 if (test_and_clear_bit(In_sync, &rdev->flags)) {
176 unsigned long flags;
177 spin_lock_irqsave(&conf->device_lock, flags);
178 mddev->degraded++;
179 spin_unlock_irqrestore(&conf->device_lock, flags);
180 }
181 set_bit(Faulty, &rdev->flags);
182 set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags);
183 pr_err("multipath: IO failure on %s, disabling IO path.\n"
184 "multipath: Operation continuing on %d IO paths.\n",
185 bdevname(rdev->bdev, b),
186 conf->raid_disks - mddev->degraded);
187}
188
189static void print_multipath_conf (struct mpconf *conf)
190{
191 int i;
192 struct multipath_info *tmp;
193
194 pr_debug("MULTIPATH conf printout:\n");
195 if (!conf) {
196 pr_debug("(conf==NULL)\n");
197 return;
198 }
199 pr_debug(" --- wd:%d rd:%d\n", conf->raid_disks - conf->mddev->degraded,
200 conf->raid_disks);
201
202 for (i = 0; i < conf->raid_disks; i++) {
203 char b[BDEVNAME_SIZE];
204 tmp = conf->multipaths + i;
205 if (tmp->rdev)
206 pr_debug(" disk%d, o:%d, dev:%s\n",
207 i,!test_bit(Faulty, &tmp->rdev->flags),
208 bdevname(tmp->rdev->bdev,b));
209 }
210}
211
212static int multipath_add_disk(struct mddev *mddev, struct md_rdev *rdev)
213{
214 struct mpconf *conf = mddev->private;
215 int err = -EEXIST;
216 int path;
217 struct multipath_info *p;
218 int first = 0;
219 int last = mddev->raid_disks - 1;
220
221 if (rdev->raid_disk >= 0)
222 first = last = rdev->raid_disk;
223
224 print_multipath_conf(conf);
225
226 for (path = first; path <= last; path++)
227 if ((p=conf->multipaths+path)->rdev == NULL) {
228 disk_stack_limits(mddev->gendisk, rdev->bdev,
229 rdev->data_offset << 9);
230
231 err = md_integrity_add_rdev(rdev, mddev);
232 if (err)
233 break;
234 spin_lock_irq(&conf->device_lock);
235 mddev->degraded--;
236 rdev->raid_disk = path;
237 set_bit(In_sync, &rdev->flags);
238 spin_unlock_irq(&conf->device_lock);
239 rcu_assign_pointer(p->rdev, rdev);
240 err = 0;
241 break;
242 }
243
244 print_multipath_conf(conf);
245
246 return err;
247}
248
249static int multipath_remove_disk(struct mddev *mddev, struct md_rdev *rdev)
250{
251 struct mpconf *conf = mddev->private;
252 int err = 0;
253 int number = rdev->raid_disk;
254 struct multipath_info *p = conf->multipaths + number;
255
256 print_multipath_conf(conf);
257
258 if (rdev == p->rdev) {
259 if (test_bit(In_sync, &rdev->flags) ||
260 atomic_read(&rdev->nr_pending)) {
261 pr_warn("hot-remove-disk, slot %d is identified but is still operational!\n", number);
262 err = -EBUSY;
263 goto abort;
264 }
265 p->rdev = NULL;
266 if (!test_bit(RemoveSynchronized, &rdev->flags)) {
267 synchronize_rcu();
268 if (atomic_read(&rdev->nr_pending)) {
269 /* lost the race, try later */
270 err = -EBUSY;
271 p->rdev = rdev;
272 goto abort;
273 }
274 }
275 err = md_integrity_register(mddev);
276 }
277abort:
278
279 print_multipath_conf(conf);
280 return err;
281}
282
283/*
284 * This is a kernel thread which:
285 *
286 * 1. Retries failed read operations on working multipaths.
287 * 2. Updates the raid superblock when problems encounter.
288 * 3. Performs writes following reads for array syncronising.
289 */
290
291static void multipathd(struct md_thread *thread)
292{
293 struct mddev *mddev = thread->mddev;
294 struct multipath_bh *mp_bh;
295 struct bio *bio;
296 unsigned long flags;
297 struct mpconf *conf = mddev->private;
298 struct list_head *head = &conf->retry_list;
299
300 md_check_recovery(mddev);
301 for (;;) {
302 char b[BDEVNAME_SIZE];
303 spin_lock_irqsave(&conf->device_lock, flags);
304 if (list_empty(head))
305 break;
306 mp_bh = list_entry(head->prev, struct multipath_bh, retry_list);
307 list_del(head->prev);
308 spin_unlock_irqrestore(&conf->device_lock, flags);
309
310 bio = &mp_bh->bio;
311 bio->bi_iter.bi_sector = mp_bh->master_bio->bi_iter.bi_sector;
312
313 if ((mp_bh->path = multipath_map (conf))<0) {
314 pr_err("multipath: %s: unrecoverable IO read error for block %llu\n",
315 bio_devname(bio, b),
316 (unsigned long long)bio->bi_iter.bi_sector);
317 multipath_end_bh_io(mp_bh, BLK_STS_IOERR);
318 } else {
319 pr_err("multipath: %s: redirecting sector %llu to another IO path\n",
320 bio_devname(bio, b),
321 (unsigned long long)bio->bi_iter.bi_sector);
322 *bio = *(mp_bh->master_bio);
323 bio->bi_iter.bi_sector +=
324 conf->multipaths[mp_bh->path].rdev->data_offset;
325 bio_set_dev(bio, conf->multipaths[mp_bh->path].rdev->bdev);
326 bio->bi_opf |= REQ_FAILFAST_TRANSPORT;
327 bio->bi_end_io = multipath_end_request;
328 bio->bi_private = mp_bh;
329 submit_bio_noacct(bio);
330 }
331 }
332 spin_unlock_irqrestore(&conf->device_lock, flags);
333}
334
335static sector_t multipath_size(struct mddev *mddev, sector_t sectors, int raid_disks)
336{
337 WARN_ONCE(sectors || raid_disks,
338 "%s does not support generic reshape\n", __func__);
339
340 return mddev->dev_sectors;
341}
342
343static int multipath_run (struct mddev *mddev)
344{
345 struct mpconf *conf;
346 int disk_idx;
347 struct multipath_info *disk;
348 struct md_rdev *rdev;
349 int working_disks;
350 int ret;
351
352 if (md_check_no_bitmap(mddev))
353 return -EINVAL;
354
355 if (mddev->level != LEVEL_MULTIPATH) {
356 pr_warn("multipath: %s: raid level not set to multipath IO (%d)\n",
357 mdname(mddev), mddev->level);
358 goto out;
359 }
360 /*
361 * copy the already verified devices into our private MULTIPATH
362 * bookkeeping area. [whatever we allocate in multipath_run(),
363 * should be freed in multipath_free()]
364 */
365
366 conf = kzalloc(sizeof(struct mpconf), GFP_KERNEL);
367 mddev->private = conf;
368 if (!conf)
369 goto out;
370
371 conf->multipaths = kcalloc(mddev->raid_disks,
372 sizeof(struct multipath_info),
373 GFP_KERNEL);
374 if (!conf->multipaths)
375 goto out_free_conf;
376
377 working_disks = 0;
378 rdev_for_each(rdev, mddev) {
379 disk_idx = rdev->raid_disk;
380 if (disk_idx < 0 ||
381 disk_idx >= mddev->raid_disks)
382 continue;
383
384 disk = conf->multipaths + disk_idx;
385 disk->rdev = rdev;
386 disk_stack_limits(mddev->gendisk, rdev->bdev,
387 rdev->data_offset << 9);
388
389 if (!test_bit(Faulty, &rdev->flags))
390 working_disks++;
391 }
392
393 conf->raid_disks = mddev->raid_disks;
394 conf->mddev = mddev;
395 spin_lock_init(&conf->device_lock);
396 INIT_LIST_HEAD(&conf->retry_list);
397
398 if (!working_disks) {
399 pr_warn("multipath: no operational IO paths for %s\n",
400 mdname(mddev));
401 goto out_free_conf;
402 }
403 mddev->degraded = conf->raid_disks - working_disks;
404
405 ret = mempool_init_kmalloc_pool(&conf->pool, NR_RESERVED_BUFS,
406 sizeof(struct multipath_bh));
407 if (ret)
408 goto out_free_conf;
409
410 mddev->thread = md_register_thread(multipathd, mddev,
411 "multipath");
412 if (!mddev->thread)
413 goto out_free_conf;
414
415 pr_info("multipath: array %s active with %d out of %d IO paths\n",
416 mdname(mddev), conf->raid_disks - mddev->degraded,
417 mddev->raid_disks);
418 /*
419 * Ok, everything is just fine now
420 */
421 md_set_array_sectors(mddev, multipath_size(mddev, 0, 0));
422
423 if (md_integrity_register(mddev))
424 goto out_free_conf;
425
426 return 0;
427
428out_free_conf:
429 mempool_exit(&conf->pool);
430 kfree(conf->multipaths);
431 kfree(conf);
432 mddev->private = NULL;
433out:
434 return -EIO;
435}
436
437static void multipath_free(struct mddev *mddev, void *priv)
438{
439 struct mpconf *conf = priv;
440
441 mempool_exit(&conf->pool);
442 kfree(conf->multipaths);
443 kfree(conf);
444}
445
446static struct md_personality multipath_personality =
447{
448 .name = "multipath",
449 .level = LEVEL_MULTIPATH,
450 .owner = THIS_MODULE,
451 .make_request = multipath_make_request,
452 .run = multipath_run,
453 .free = multipath_free,
454 .status = multipath_status,
455 .error_handler = multipath_error,
456 .hot_add_disk = multipath_add_disk,
457 .hot_remove_disk= multipath_remove_disk,
458 .size = multipath_size,
459};
460
461static int __init multipath_init (void)
462{
463 return register_md_personality (&multipath_personality);
464}
465
466static void __exit multipath_exit (void)
467{
468 unregister_md_personality (&multipath_personality);
469}
470
471module_init(multipath_init);
472module_exit(multipath_exit);
473MODULE_LICENSE("GPL");
474MODULE_DESCRIPTION("simple multi-path personality for MD (deprecated)");
475MODULE_ALIAS("md-personality-7"); /* MULTIPATH */
476MODULE_ALIAS("md-multipath");
477MODULE_ALIAS("md-level--4");