xref: /openbmc/linux/drivers/md/md-multipath.c (revision bdf2b521)
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 
multipath_map(struct mpconf * conf)26 static 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 
multipath_reschedule_retry(struct multipath_bh * mp_bh)51 static 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  */
multipath_end_bh_io(struct multipath_bh * mp_bh,blk_status_t status)68 static 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 
multipath_end_request(struct bio * bio)78 static 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 
multipath_make_request(struct mddev * mddev,struct bio * bio)100 static 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 	md_account_bio(mddev, &bio);
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_clone(multipath->rdev->bdev, &mp_bh->bio, bio, GFP_NOIO);
125 
126 	mp_bh->bio.bi_iter.bi_sector += multipath->rdev->data_offset;
127 	mp_bh->bio.bi_opf |= REQ_FAILFAST_TRANSPORT;
128 	mp_bh->bio.bi_end_io = multipath_end_request;
129 	mp_bh->bio.bi_private = mp_bh;
130 	mddev_check_write_zeroes(mddev, &mp_bh->bio);
131 	submit_bio_noacct(&mp_bh->bio);
132 	return true;
133 }
134 
multipath_status(struct seq_file * seq,struct mddev * mddev)135 static void multipath_status(struct seq_file *seq, struct mddev *mddev)
136 {
137 	struct mpconf *conf = mddev->private;
138 	int i;
139 
140 	seq_printf (seq, " [%d/%d] [", conf->raid_disks,
141 		    conf->raid_disks - mddev->degraded);
142 	rcu_read_lock();
143 	for (i = 0; i < conf->raid_disks; i++) {
144 		struct md_rdev *rdev = rcu_dereference(conf->multipaths[i].rdev);
145 		seq_printf (seq, "%s", rdev && test_bit(In_sync, &rdev->flags) ? "U" : "_");
146 	}
147 	rcu_read_unlock();
148 	seq_putc(seq, ']');
149 }
150 
151 /*
152  * Careful, this can execute in IRQ contexts as well!
153  */
multipath_error(struct mddev * mddev,struct md_rdev * rdev)154 static void multipath_error (struct mddev *mddev, struct md_rdev *rdev)
155 {
156 	struct mpconf *conf = mddev->private;
157 
158 	if (conf->raid_disks - mddev->degraded <= 1) {
159 		/*
160 		 * Uh oh, we can do nothing if this is our last path, but
161 		 * first check if this is a queued request for a device
162 		 * which has just failed.
163 		 */
164 		pr_warn("multipath: only one IO path left and IO error.\n");
165 		/* leave it active... it's all we have */
166 		return;
167 	}
168 	/*
169 	 * Mark disk as unusable
170 	 */
171 	if (test_and_clear_bit(In_sync, &rdev->flags)) {
172 		unsigned long flags;
173 		spin_lock_irqsave(&conf->device_lock, flags);
174 		mddev->degraded++;
175 		spin_unlock_irqrestore(&conf->device_lock, flags);
176 	}
177 	set_bit(Faulty, &rdev->flags);
178 	set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags);
179 	pr_err("multipath: IO failure on %pg, disabling IO path.\n"
180 	       "multipath: Operation continuing on %d IO paths.\n",
181 	       rdev->bdev,
182 	       conf->raid_disks - mddev->degraded);
183 }
184 
print_multipath_conf(struct mpconf * conf)185 static void print_multipath_conf (struct mpconf *conf)
186 {
187 	int i;
188 	struct multipath_info *tmp;
189 
190 	pr_debug("MULTIPATH conf printout:\n");
191 	if (!conf) {
192 		pr_debug("(conf==NULL)\n");
193 		return;
194 	}
195 	pr_debug(" --- wd:%d rd:%d\n", conf->raid_disks - conf->mddev->degraded,
196 		 conf->raid_disks);
197 
198 	for (i = 0; i < conf->raid_disks; i++) {
199 		tmp = conf->multipaths + i;
200 		if (tmp->rdev)
201 			pr_debug(" disk%d, o:%d, dev:%pg\n",
202 				 i,!test_bit(Faulty, &tmp->rdev->flags),
203 				 tmp->rdev->bdev);
204 	}
205 }
206 
multipath_add_disk(struct mddev * mddev,struct md_rdev * rdev)207 static int multipath_add_disk(struct mddev *mddev, struct md_rdev *rdev)
208 {
209 	struct mpconf *conf = mddev->private;
210 	int err = -EEXIST;
211 	int path;
212 	struct multipath_info *p;
213 	int first = 0;
214 	int last = mddev->raid_disks - 1;
215 
216 	if (rdev->raid_disk >= 0)
217 		first = last = rdev->raid_disk;
218 
219 	print_multipath_conf(conf);
220 
221 	for (path = first; path <= last; path++)
222 		if ((p=conf->multipaths+path)->rdev == NULL) {
223 			disk_stack_limits(mddev->gendisk, rdev->bdev,
224 					  rdev->data_offset << 9);
225 
226 			err = md_integrity_add_rdev(rdev, mddev);
227 			if (err)
228 				break;
229 			spin_lock_irq(&conf->device_lock);
230 			mddev->degraded--;
231 			rdev->raid_disk = path;
232 			set_bit(In_sync, &rdev->flags);
233 			spin_unlock_irq(&conf->device_lock);
234 			rcu_assign_pointer(p->rdev, rdev);
235 			err = 0;
236 			break;
237 		}
238 
239 	print_multipath_conf(conf);
240 
241 	return err;
242 }
243 
multipath_remove_disk(struct mddev * mddev,struct md_rdev * rdev)244 static int multipath_remove_disk(struct mddev *mddev, struct md_rdev *rdev)
245 {
246 	struct mpconf *conf = mddev->private;
247 	int err = 0;
248 	int number = rdev->raid_disk;
249 	struct multipath_info *p = conf->multipaths + number;
250 
251 	print_multipath_conf(conf);
252 
253 	if (rdev == p->rdev) {
254 		if (test_bit(In_sync, &rdev->flags) ||
255 		    atomic_read(&rdev->nr_pending)) {
256 			pr_warn("hot-remove-disk, slot %d is identified but is still operational!\n", number);
257 			err = -EBUSY;
258 			goto abort;
259 		}
260 		p->rdev = NULL;
261 		if (!test_bit(RemoveSynchronized, &rdev->flags)) {
262 			synchronize_rcu();
263 			if (atomic_read(&rdev->nr_pending)) {
264 				/* lost the race, try later */
265 				err = -EBUSY;
266 				p->rdev = rdev;
267 				goto abort;
268 			}
269 		}
270 		err = md_integrity_register(mddev);
271 	}
272 abort:
273 
274 	print_multipath_conf(conf);
275 	return err;
276 }
277 
278 /*
279  * This is a kernel thread which:
280  *
281  *	1.	Retries failed read operations on working multipaths.
282  *	2.	Updates the raid superblock when problems encounter.
283  *	3.	Performs writes following reads for array syncronising.
284  */
285 
multipathd(struct md_thread * thread)286 static void multipathd(struct md_thread *thread)
287 {
288 	struct mddev *mddev = thread->mddev;
289 	struct multipath_bh *mp_bh;
290 	struct bio *bio;
291 	unsigned long flags;
292 	struct mpconf *conf = mddev->private;
293 	struct list_head *head = &conf->retry_list;
294 
295 	md_check_recovery(mddev);
296 	for (;;) {
297 		spin_lock_irqsave(&conf->device_lock, flags);
298 		if (list_empty(head))
299 			break;
300 		mp_bh = list_entry(head->prev, struct multipath_bh, retry_list);
301 		list_del(head->prev);
302 		spin_unlock_irqrestore(&conf->device_lock, flags);
303 
304 		bio = &mp_bh->bio;
305 		bio->bi_iter.bi_sector = mp_bh->master_bio->bi_iter.bi_sector;
306 
307 		if ((mp_bh->path = multipath_map (conf))<0) {
308 			pr_err("multipath: %pg: unrecoverable IO read error for block %llu\n",
309 			       bio->bi_bdev,
310 			       (unsigned long long)bio->bi_iter.bi_sector);
311 			multipath_end_bh_io(mp_bh, BLK_STS_IOERR);
312 		} else {
313 			pr_err("multipath: %pg: redirecting sector %llu to another IO path\n",
314 			       bio->bi_bdev,
315 			       (unsigned long long)bio->bi_iter.bi_sector);
316 			*bio = *(mp_bh->master_bio);
317 			bio->bi_iter.bi_sector +=
318 				conf->multipaths[mp_bh->path].rdev->data_offset;
319 			bio_set_dev(bio, conf->multipaths[mp_bh->path].rdev->bdev);
320 			bio->bi_opf |= REQ_FAILFAST_TRANSPORT;
321 			bio->bi_end_io = multipath_end_request;
322 			bio->bi_private = mp_bh;
323 			submit_bio_noacct(bio);
324 		}
325 	}
326 	spin_unlock_irqrestore(&conf->device_lock, flags);
327 }
328 
multipath_size(struct mddev * mddev,sector_t sectors,int raid_disks)329 static sector_t multipath_size(struct mddev *mddev, sector_t sectors, int raid_disks)
330 {
331 	WARN_ONCE(sectors || raid_disks,
332 		  "%s does not support generic reshape\n", __func__);
333 
334 	return mddev->dev_sectors;
335 }
336 
multipath_run(struct mddev * mddev)337 static int multipath_run (struct mddev *mddev)
338 {
339 	struct mpconf *conf;
340 	int disk_idx;
341 	struct multipath_info *disk;
342 	struct md_rdev *rdev;
343 	int working_disks;
344 	int ret;
345 
346 	if (md_check_no_bitmap(mddev))
347 		return -EINVAL;
348 
349 	if (mddev->level != LEVEL_MULTIPATH) {
350 		pr_warn("multipath: %s: raid level not set to multipath IO (%d)\n",
351 			mdname(mddev), mddev->level);
352 		goto out;
353 	}
354 	/*
355 	 * copy the already verified devices into our private MULTIPATH
356 	 * bookkeeping area. [whatever we allocate in multipath_run(),
357 	 * should be freed in multipath_free()]
358 	 */
359 
360 	conf = kzalloc(sizeof(struct mpconf), GFP_KERNEL);
361 	mddev->private = conf;
362 	if (!conf)
363 		goto out;
364 
365 	conf->multipaths = kcalloc(mddev->raid_disks,
366 				   sizeof(struct multipath_info),
367 				   GFP_KERNEL);
368 	if (!conf->multipaths)
369 		goto out_free_conf;
370 
371 	working_disks = 0;
372 	rdev_for_each(rdev, mddev) {
373 		disk_idx = rdev->raid_disk;
374 		if (disk_idx < 0 ||
375 		    disk_idx >= mddev->raid_disks)
376 			continue;
377 
378 		disk = conf->multipaths + disk_idx;
379 		disk->rdev = rdev;
380 		disk_stack_limits(mddev->gendisk, rdev->bdev,
381 				  rdev->data_offset << 9);
382 
383 		if (!test_bit(Faulty, &rdev->flags))
384 			working_disks++;
385 	}
386 
387 	conf->raid_disks = mddev->raid_disks;
388 	conf->mddev = mddev;
389 	spin_lock_init(&conf->device_lock);
390 	INIT_LIST_HEAD(&conf->retry_list);
391 
392 	if (!working_disks) {
393 		pr_warn("multipath: no operational IO paths for %s\n",
394 			mdname(mddev));
395 		goto out_free_conf;
396 	}
397 	mddev->degraded = conf->raid_disks - working_disks;
398 
399 	ret = mempool_init_kmalloc_pool(&conf->pool, NR_RESERVED_BUFS,
400 					sizeof(struct multipath_bh));
401 	if (ret)
402 		goto out_free_conf;
403 
404 	rcu_assign_pointer(mddev->thread,
405 			   md_register_thread(multipathd, mddev, "multipath"));
406 	if (!mddev->thread)
407 		goto out_free_conf;
408 
409 	pr_info("multipath: array %s active with %d out of %d IO paths\n",
410 		mdname(mddev), conf->raid_disks - mddev->degraded,
411 		mddev->raid_disks);
412 	/*
413 	 * Ok, everything is just fine now
414 	 */
415 	md_set_array_sectors(mddev, multipath_size(mddev, 0, 0));
416 
417 	if (md_integrity_register(mddev))
418 		goto out_free_conf;
419 
420 	return 0;
421 
422 out_free_conf:
423 	mempool_exit(&conf->pool);
424 	kfree(conf->multipaths);
425 	kfree(conf);
426 	mddev->private = NULL;
427 out:
428 	return -EIO;
429 }
430 
multipath_free(struct mddev * mddev,void * priv)431 static void multipath_free(struct mddev *mddev, void *priv)
432 {
433 	struct mpconf *conf = priv;
434 
435 	mempool_exit(&conf->pool);
436 	kfree(conf->multipaths);
437 	kfree(conf);
438 }
439 
440 static struct md_personality multipath_personality =
441 {
442 	.name		= "multipath",
443 	.level		= LEVEL_MULTIPATH,
444 	.owner		= THIS_MODULE,
445 	.make_request	= multipath_make_request,
446 	.run		= multipath_run,
447 	.free		= multipath_free,
448 	.status		= multipath_status,
449 	.error_handler	= multipath_error,
450 	.hot_add_disk	= multipath_add_disk,
451 	.hot_remove_disk= multipath_remove_disk,
452 	.size		= multipath_size,
453 };
454 
multipath_init(void)455 static int __init multipath_init (void)
456 {
457 	return register_md_personality (&multipath_personality);
458 }
459 
multipath_exit(void)460 static void __exit multipath_exit (void)
461 {
462 	unregister_md_personality (&multipath_personality);
463 }
464 
465 module_init(multipath_init);
466 module_exit(multipath_exit);
467 MODULE_LICENSE("GPL");
468 MODULE_DESCRIPTION("simple multi-path personality for MD (deprecated)");
469 MODULE_ALIAS("md-personality-7"); /* MULTIPATH */
470 MODULE_ALIAS("md-multipath");
471 MODULE_ALIAS("md-level--4");
472