1	// SPDX-License-Identifier: GPL-2.0-only
2	/*
3	* Copyright (C) 2003 Sistina Software Limited.
4	* Copyright (C) 2004-2005 Red Hat, Inc. All rights reserved.
5	*
6	* This file is released under the GPL.
7	*/
8
9	#include <linux/device-mapper.h>
10
11	#include "dm-rq.h"
12	#include "dm-bio-record.h"
13	#include "dm-path-selector.h"
14	#include "dm-uevent.h"
15
16	#include <linux/blkdev.h>
17	#include <linux/ctype.h>
18	#include <linux/init.h>
19	#include <linux/mempool.h>
20	#include <linux/module.h>
21	#include <linux/pagemap.h>
22	#include <linux/slab.h>
23	#include <linux/time.h>
24	#include <linux/timer.h>
25	#include <linux/workqueue.h>
26	#include <linux/delay.h>
27	#include <scsi/scsi_dh.h>
28	#include <linux/atomic.h>
29	#include <linux/blk-mq.h>
30
31	static struct workqueue_struct *dm_mpath_wq;
32
33	#define DM_MSG_PREFIX "multipath"
34	#define DM_PG_INIT_DELAY_MSECS 2000
35	#define DM_PG_INIT_DELAY_DEFAULT ((unsigned int) -1)
36	#define QUEUE_IF_NO_PATH_TIMEOUT_DEFAULT 0
37
38	static unsigned long queue_if_no_path_timeout_secs = QUEUE_IF_NO_PATH_TIMEOUT_DEFAULT;
39
40	/* Path properties */
41	struct pgpath {
42	struct list_head list;
43
44	struct priority_group *pg; /* Owning PG */
45	unsigned int fail_count; /* Cumulative failure count */
46
47	struct dm_path path;
48	struct delayed_work activate_path;
49
50	bool is_active:1; /* Path status */
51	};
52
53	#define path_to_pgpath(__pgp) container_of((__pgp), struct pgpath, path)
54
55	/*
56	* Paths are grouped into Priority Groups and numbered from 1 upwards.
57	* Each has a path selector which controls which path gets used.
58	*/
59	struct priority_group {
60	struct list_head list;
61
62	struct multipath *m; /* Owning multipath instance */
63	struct path_selector ps;
64
65	unsigned int pg_num; /* Reference number */
66	unsigned int nr_pgpaths; /* Number of paths in PG */
67	struct list_head pgpaths;
68
69	bool bypassed:1; /* Temporarily bypass this PG? */
70	};
71
72	/* Multipath context */
73	struct multipath {
74	unsigned long flags; /* Multipath state flags */
75
76	spinlock_t lock;
77	enum dm_queue_mode queue_mode;
78
79	struct pgpath *current_pgpath;
80	struct priority_group *current_pg;
81	struct priority_group *next_pg; /* Switch to this PG if set */
82	struct priority_group *last_probed_pg;
83
84	atomic_t nr_valid_paths; /* Total number of usable paths */
85	unsigned int nr_priority_groups;
86	struct list_head priority_groups;
87
88	const char *hw_handler_name;
89	char *hw_handler_params;
90	wait_queue_head_t pg_init_wait; /* Wait for pg_init completion */
91	wait_queue_head_t probe_wait; /* Wait for probing paths */
92	unsigned int pg_init_retries; /* Number of times to retry pg_init */
93	unsigned int pg_init_delay_msecs; /* Number of msecs before pg_init retry */
94	atomic_t pg_init_in_progress; /* Only one pg_init allowed at once */
95	atomic_t pg_init_count; /* Number of times pg_init called */
96
97	struct mutex work_mutex;
98	struct work_struct trigger_event;
99	struct dm_target *ti;
100
101	struct work_struct process_queued_bios;
102	struct bio_list queued_bios;
103
104	struct timer_list nopath_timer; /* Timeout for queue_if_no_path */
105	bool is_suspending;
106	};
107
108	/*
109	* Context information attached to each io we process.
110	*/
111	struct dm_mpath_io {
112	struct pgpath *pgpath;
113	size_t nr_bytes;
114	u64 start_time_ns;
115	};
116
117	typedef int (*action_fn) (struct pgpath *pgpath);
118
119	static struct workqueue_struct *kmultipathd, *kmpath_handlerd;
120	static void trigger_event(struct work_struct *work);
121	static void activate_or_offline_path(struct pgpath *pgpath);
122	static void activate_path_work(struct work_struct *work);
123	static void process_queued_bios(struct work_struct *work);
124	static void queue_if_no_path_timeout_work(struct timer_list *t);
125
126	/*
127	*-----------------------------------------------
128	* Multipath state flags.
129	*-----------------------------------------------
130	*/
131	#define MPATHF_QUEUE_IO 0 /* Must we queue all I/O? */
132	#define MPATHF_QUEUE_IF_NO_PATH 1 /* Queue I/O if last path fails? */
133	#define MPATHF_SAVED_QUEUE_IF_NO_PATH 2 /* Saved state during suspension */
134	/* MPATHF_RETAIN_ATTACHED_HW_HANDLER no longer has any effect */
135	#define MPATHF_PG_INIT_DISABLED 4 /* pg_init is not currently allowed */
136	#define MPATHF_PG_INIT_REQUIRED 5 /* pg_init needs calling? */
137	#define MPATHF_PG_INIT_DELAY_RETRY 6 /* Delay pg_init retry? */
138	#define MPATHF_DELAY_PG_SWITCH 7 /* Delay switching pg if it still has paths */
139	#define MPATHF_NEED_PG_SWITCH 8 /* Need to switch pgs after the delay has ended */
140
141	static bool mpath_double_check_test_bit(int MPATHF_bit, struct multipath *m)
142	{
143	bool r = test_bit(MPATHF_bit, &m->flags);
144
145	if (r) {
146	unsigned long flags;
147
148	spin_lock_irqsave(&m->lock, flags);
149	r = test_bit(MPATHF_bit, &m->flags);
150	spin_unlock_irqrestore(lock: &m->lock, flags);
151	}
152
153	return r;
154	}
155
156	/*
157	*-----------------------------------------------
158	* Allocation routines
159	*-----------------------------------------------
160	*/
161	static struct pgpath *alloc_pgpath(void)
162	{
163	struct pgpath *pgpath = kzalloc(sizeof(*pgpath), GFP_KERNEL);
164
165	if (!pgpath)
166	return NULL;
167
168	pgpath->is_active = true;
169
170	return pgpath;
171	}
172
173	static void free_pgpath(struct pgpath *pgpath)
174	{
175	kfree(objp: pgpath);
176	}
177
178	static struct priority_group *alloc_priority_group(void)
179	{
180	struct priority_group *pg;
181
182	pg = kzalloc(sizeof(*pg), GFP_KERNEL);
183
184	if (pg)
185	INIT_LIST_HEAD(list: &pg->pgpaths);
186
187	return pg;
188	}
189
190	static void free_pgpaths(struct list_head *pgpaths, struct dm_target *ti)
191	{
192	struct pgpath *pgpath, *tmp;
193
194	list_for_each_entry_safe(pgpath, tmp, pgpaths, list) {
195	list_del(entry: &pgpath->list);
196	dm_put_device(ti, d: pgpath->path.dev);
197	free_pgpath(pgpath);
198	}
199	}
200
201	static void free_priority_group(struct priority_group *pg,
202	struct dm_target *ti)
203	{
204	struct path_selector *ps = &pg->ps;
205
206	if (ps->type) {
207	ps->type->destroy(ps);
208	dm_put_path_selector(pst: ps->type);
209	}
210
211	free_pgpaths(pgpaths: &pg->pgpaths, ti);
212	kfree(objp: pg);
213	}
214
215	static struct multipath *alloc_multipath(struct dm_target *ti)
216	{
217	struct multipath *m;
218
219	m = kzalloc(sizeof(*m), GFP_KERNEL);
220	if (m) {
221	INIT_LIST_HEAD(list: &m->priority_groups);
222	spin_lock_init(&m->lock);
223	atomic_set(v: &m->nr_valid_paths, i: 0);
224	INIT_WORK(&m->trigger_event, trigger_event);
225	mutex_init(&m->work_mutex);
226
227	m->queue_mode = DM_TYPE_NONE;
228
229	m->ti = ti;
230	ti->private = m;
231
232	timer_setup(&m->nopath_timer, queue_if_no_path_timeout_work, 0);
233	}
234
235	return m;
236	}
237
238	static int alloc_multipath_stage2(struct dm_target *ti, struct multipath *m)
239	{
240	if (m->queue_mode == DM_TYPE_NONE)
241	m->queue_mode = DM_TYPE_REQUEST_BASED;
242	else if (m->queue_mode == DM_TYPE_BIO_BASED)
243	INIT_WORK(&m->process_queued_bios, process_queued_bios);
244
245	dm_table_set_type(t: ti->table, type: m->queue_mode);
246
247	/*
248	* Init fields that are only used when a scsi_dh is attached
249	* - must do this unconditionally (really doesn't hurt non-SCSI uses)
250	*/
251	set_bit(MPATHF_QUEUE_IO, addr: &m->flags);
252	atomic_set(v: &m->pg_init_in_progress, i: 0);
253	atomic_set(v: &m->pg_init_count, i: 0);
254	m->pg_init_delay_msecs = DM_PG_INIT_DELAY_DEFAULT;
255	init_waitqueue_head(&m->pg_init_wait);
256	init_waitqueue_head(&m->probe_wait);
257
258	return 0;
259	}
260
261	static void free_multipath(struct multipath *m)
262	{
263	struct priority_group *pg, *tmp;
264
265	list_for_each_entry_safe(pg, tmp, &m->priority_groups, list) {
266	list_del(entry: &pg->list);
267	free_priority_group(pg, ti: m->ti);
268	}
269
270	kfree(objp: m->hw_handler_name);
271	kfree(objp: m->hw_handler_params);
272	mutex_destroy(lock: &m->work_mutex);
273	kfree(objp: m);
274	}
275
276	static struct dm_mpath_io *get_mpio(union map_info *info)
277	{
278	return info->ptr;
279	}
280
281	static size_t multipath_per_bio_data_size(void)
282	{
283	return sizeof(struct dm_mpath_io) + sizeof(struct dm_bio_details);
284	}
285
286	static struct dm_mpath_io *get_mpio_from_bio(struct bio *bio)
287	{
288	return dm_per_bio_data(bio, data_size: multipath_per_bio_data_size());
289	}
290
291	static struct dm_bio_details *get_bio_details_from_mpio(struct dm_mpath_io *mpio)
292	{
293	/* dm_bio_details is immediately after the dm_mpath_io in bio's per-bio-data */
294	void *bio_details = mpio + 1;
295	return bio_details;
296	}
297
298	static void multipath_init_per_bio_data(struct bio *bio, struct dm_mpath_io **mpio_p)
299	{
300	struct dm_mpath_io *mpio = get_mpio_from_bio(bio);
301	struct dm_bio_details *bio_details = get_bio_details_from_mpio(mpio);
302
303	mpio->nr_bytes = bio->bi_iter.bi_size;
304	mpio->pgpath = NULL;
305	mpio->start_time_ns = 0;
306	*mpio_p = mpio;
307
308	dm_bio_record(bd: bio_details, bio);
309	}
310
311	/*
312	*-----------------------------------------------
313	* Path selection
314	*-----------------------------------------------
315	*/
316	static int __pg_init_all_paths(struct multipath *m)
317	{
318	struct pgpath *pgpath;
319	unsigned long pg_init_delay = 0;
320
321	lockdep_assert_held(&m->lock);
322
323	if (atomic_read(v: &m->pg_init_in_progress) || test_bit(MPATHF_PG_INIT_DISABLED, &m->flags))
324	return 0;
325
326	atomic_inc(v: &m->pg_init_count);
327	clear_bit(MPATHF_PG_INIT_REQUIRED, addr: &m->flags);
328
329	/* Check here to reset pg_init_required */
330	if (!m->current_pg)
331	return 0;
332
333	if (test_bit(MPATHF_PG_INIT_DELAY_RETRY, &m->flags))
334	pg_init_delay = msecs_to_jiffies(m: m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT ?
335	m->pg_init_delay_msecs : DM_PG_INIT_DELAY_MSECS);
336	list_for_each_entry(pgpath, &m->current_pg->pgpaths, list) {
337	/* Skip failed paths */
338	if (!pgpath->is_active)
339	continue;
340	if (queue_delayed_work(wq: kmpath_handlerd, dwork: &pgpath->activate_path,
341	delay: pg_init_delay))
342	atomic_inc(v: &m->pg_init_in_progress);
343	}
344	return atomic_read(v: &m->pg_init_in_progress);
345	}
346
347	static int pg_init_all_paths(struct multipath *m)
348	{
349	int ret;
350	unsigned long flags;
351
352	spin_lock_irqsave(&m->lock, flags);
353	ret = __pg_init_all_paths(m);
354	spin_unlock_irqrestore(lock: &m->lock, flags);
355
356	return ret;
357	}
358
359	static void __switch_pg(struct multipath *m, struct priority_group *pg)
360	{
361	lockdep_assert_held(&m->lock);
362
363	m->current_pg = pg;
364
365	/* Must we initialise the PG first, and queue I/O till it's ready? */
366	if (m->hw_handler_name) {
367	set_bit(MPATHF_PG_INIT_REQUIRED, addr: &m->flags);
368	set_bit(MPATHF_QUEUE_IO, addr: &m->flags);
369	} else {
370	clear_bit(MPATHF_PG_INIT_REQUIRED, addr: &m->flags);
371	clear_bit(MPATHF_QUEUE_IO, addr: &m->flags);
372	}
373
374	atomic_set(v: &m->pg_init_count, i: 0);
375	}
376
377	static struct pgpath *choose_path_in_pg(struct multipath *m,
378	struct priority_group *pg,
379	size_t nr_bytes)
380	{
381	unsigned long flags;
382	struct dm_path *path;
383	struct pgpath *pgpath;
384
385	path = pg->ps.type->select_path(&pg->ps, nr_bytes);
386	if (!path)
387	return ERR_PTR(error: -ENXIO);
388
389	pgpath = path_to_pgpath(path);
390
391	if (unlikely(READ_ONCE(m->current_pg) != pg)) {
392	/* Only update current_pgpath if pg changed */
393	spin_lock_irqsave(&m->lock, flags);
394	m->current_pgpath = pgpath;
395	__switch_pg(m, pg);
396	spin_unlock_irqrestore(lock: &m->lock, flags);
397	}
398
399	return pgpath;
400	}
401
402	static struct pgpath *choose_pgpath(struct multipath *m, size_t nr_bytes)
403	{
404	unsigned long flags;
405	struct priority_group *pg;
406	struct pgpath *pgpath;
407	unsigned int bypassed = 1;
408
409	if (!atomic_read(v: &m->nr_valid_paths)) {
410	spin_lock_irqsave(&m->lock, flags);
411	clear_bit(MPATHF_QUEUE_IO, addr: &m->flags);
412	spin_unlock_irqrestore(lock: &m->lock, flags);
413	goto failed;
414	}
415
416	/* Don't change PG until it has no remaining paths */
417	pg = READ_ONCE(m->current_pg);
418	if (pg) {
419	pgpath = choose_path_in_pg(m, pg, nr_bytes);
420	if (!IS_ERR_OR_NULL(ptr: pgpath))
421	return pgpath;
422	}
423
424	/* Were we instructed to switch PG? */
425	if (READ_ONCE(m->next_pg)) {
426	spin_lock_irqsave(&m->lock, flags);
427	pg = m->next_pg;
428	if (!pg) {
429	spin_unlock_irqrestore(lock: &m->lock, flags);
430	goto check_all_pgs;
431	}
432	m->next_pg = NULL;
433	spin_unlock_irqrestore(lock: &m->lock, flags);
434	pgpath = choose_path_in_pg(m, pg, nr_bytes);
435	if (!IS_ERR_OR_NULL(ptr: pgpath))
436	return pgpath;
437	}
438	check_all_pgs:
439	/*
440	* Loop through priority groups until we find a valid path.
441	* First time we skip PGs marked 'bypassed'.
442	* Second time we only try the ones we skipped, but set
443	* pg_init_delay_retry so we do not hammer controllers.
444	*/
445	do {
446	list_for_each_entry(pg, &m->priority_groups, list) {
447	if (pg->bypassed == !!bypassed)
448	continue;
449	pgpath = choose_path_in_pg(m, pg, nr_bytes);
450	if (!IS_ERR_OR_NULL(ptr: pgpath)) {
451	if (!bypassed) {
452	spin_lock_irqsave(&m->lock, flags);
453	set_bit(MPATHF_PG_INIT_DELAY_RETRY, addr: &m->flags);
454	spin_unlock_irqrestore(lock: &m->lock, flags);
455	}
456	return pgpath;
457	}
458	}
459	} while (bypassed--);
460
461	failed:
462	spin_lock_irqsave(&m->lock, flags);
463	m->current_pgpath = NULL;
464	m->current_pg = NULL;
465	spin_unlock_irqrestore(lock: &m->lock, flags);
466
467	return NULL;
468	}
469
470	/*
471	* dm_report_EIO() is a macro instead of a function to make pr_debug_ratelimited()
472	* report the function name and line number of the function from which
473	* it has been invoked.
474	*/
475	#define dm_report_EIO(m) \
476	DMDEBUG_LIMIT("%s: returning EIO; QIFNP = %d; SQIFNP = %d; DNFS = %d", \
477	dm_table_device_name((m)->ti->table), \
478	test_bit(MPATHF_QUEUE_IF_NO_PATH, &(m)->flags), \
479	test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &(m)->flags), \
480	dm_noflush_suspending((m)->ti))
481
482	/*
483	* Check whether bios must be queued in the device-mapper core rather
484	* than here in the target.
485	*/
486	static bool __must_push_back(struct multipath *m)
487	{
488	return dm_noflush_suspending(ti: m->ti);
489	}
490
491	static bool must_push_back_rq(struct multipath *m)
492	{
493	unsigned long flags;
494	bool ret;
495
496	spin_lock_irqsave(&m->lock, flags);
497	ret = (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) || __must_push_back(m));
498	spin_unlock_irqrestore(lock: &m->lock, flags);
499
500	return ret;
501	}
502
503	/*
504	* Map cloned requests (request-based multipath)
505	*/
506	static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
507	union map_info *map_context,
508	struct request **__clone)
509	{
510	struct multipath *m = ti->private;
511	size_t nr_bytes = blk_rq_bytes(rq);
512	struct pgpath *pgpath;
513	struct block_device *bdev;
514	struct dm_mpath_io *mpio = get_mpio(info: map_context);
515	struct request_queue *q;
516	struct request *clone;
517
518	/* Do we need to select a new pgpath? */
519	pgpath = READ_ONCE(m->current_pgpath);
520	if (!pgpath || !mpath_double_check_test_bit(MPATHF_QUEUE_IO, m))
521	pgpath = choose_pgpath(m, nr_bytes);
522
523	if (!pgpath) {
524	if (must_push_back_rq(m))
525	return DM_MAPIO_DELAY_REQUEUE;
526	dm_report_EIO(m); /* Failed */
527	return DM_MAPIO_KILL;
528	} else if (mpath_double_check_test_bit(MPATHF_QUEUE_IO, m) ||
529	mpath_double_check_test_bit(MPATHF_PG_INIT_REQUIRED, m)) {
530	pg_init_all_paths(m);
531	return DM_MAPIO_DELAY_REQUEUE;
532	}
533
534	mpio->pgpath = pgpath;
535	mpio->nr_bytes = nr_bytes;
536
537	bdev = pgpath->path.dev->bdev;
538	q = bdev_get_queue(bdev);
539	clone = blk_mq_alloc_request(q, opf: rq->cmd_flags | REQ_NOMERGE,
540	flags: BLK_MQ_REQ_NOWAIT);
541	if (IS_ERR(ptr: clone)) {
542	/* EBUSY, ENODEV or EWOULDBLOCK: requeue */
543	if (blk_queue_dying(q)) {
544	atomic_inc(v: &m->pg_init_in_progress);
545	activate_or_offline_path(pgpath);
546	return DM_MAPIO_DELAY_REQUEUE;
547	}
548
549	/*
550	* blk-mq's SCHED_RESTART can cover this requeue, so we
551	* needn't deal with it by DELAY_REQUEUE. More importantly,
552	* we have to return DM_MAPIO_REQUEUE so that blk-mq can
553	* get the queue busy feedback (via BLK_STS_RESOURCE),
554	* otherwise I/O merging can suffer.
555	*/
556	return DM_MAPIO_REQUEUE;
557	}
558	clone->bio = clone->biotail = NULL;
559	clone->cmd_flags |= REQ_FAILFAST_TRANSPORT;
560	*__clone = clone;
561
562	if (pgpath->pg->ps.type->start_io)
563	pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
564	&pgpath->path,
565	nr_bytes);
566	return DM_MAPIO_REMAPPED;
567	}
568
569	static void multipath_release_clone(struct request *clone,
570	union map_info *map_context)
571	{
572	if (unlikely(map_context)) {
573	/*
574	* non-NULL map_context means caller is still map
575	* method; must undo multipath_clone_and_map()
576	*/
577	struct dm_mpath_io *mpio = get_mpio(info: map_context);
578	struct pgpath *pgpath = mpio->pgpath;
579
580	if (pgpath && pgpath->pg->ps.type->end_io)
581	pgpath->pg->ps.type->end_io(&pgpath->pg->ps,
582	&pgpath->path,
583	mpio->nr_bytes,
584	clone->io_start_time_ns);
585	}
586
587	blk_mq_free_request(rq: clone);
588	}
589
590	/*
591	* Map cloned bios (bio-based multipath)
592	*/
593
594	static void __multipath_queue_bio(struct multipath *m, struct bio *bio)
595	{
596	/* Queue for the daemon to resubmit */
597	bio_list_add(bl: &m->queued_bios, bio);
598	if (!test_bit(MPATHF_QUEUE_IO, &m->flags))
599	queue_work(wq: kmultipathd, work: &m->process_queued_bios);
600	}
601
602	static void multipath_queue_bio(struct multipath *m, struct bio *bio)
603	{
604	unsigned long flags;
605
606	spin_lock_irqsave(&m->lock, flags);
607	__multipath_queue_bio(m, bio);
608	spin_unlock_irqrestore(lock: &m->lock, flags);
609	}
610
611	static struct pgpath *__map_bio(struct multipath *m, struct bio *bio)
612	{
613	struct pgpath *pgpath;
614
615	/* Do we need to select a new pgpath? */
616	pgpath = READ_ONCE(m->current_pgpath);
617	if (!pgpath || !mpath_double_check_test_bit(MPATHF_QUEUE_IO, m))
618	pgpath = choose_pgpath(m, nr_bytes: bio->bi_iter.bi_size);
619
620	if (!pgpath) {
621	spin_lock_irq(lock: &m->lock);
622	if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
623	__multipath_queue_bio(m, bio);
624	pgpath = ERR_PTR(error: -EAGAIN);
625	}
626	spin_unlock_irq(lock: &m->lock);
627
628	} else if (mpath_double_check_test_bit(MPATHF_QUEUE_IO, m) ||
629	mpath_double_check_test_bit(MPATHF_PG_INIT_REQUIRED, m)) {
630	multipath_queue_bio(m, bio);
631	pg_init_all_paths(m);
632	return ERR_PTR(error: -EAGAIN);
633	}
634
635	return pgpath;
636	}
637
638	static int __multipath_map_bio(struct multipath *m, struct bio *bio,
639	struct dm_mpath_io *mpio)
640	{
641	struct pgpath *pgpath = __map_bio(m, bio);
642
643	if (IS_ERR(ptr: pgpath))
644	return DM_MAPIO_SUBMITTED;
645
646	if (!pgpath) {
647	if (__must_push_back(m))
648	return DM_MAPIO_REQUEUE;
649	dm_report_EIO(m);
650	return DM_MAPIO_KILL;
651	}
652
653	mpio->pgpath = pgpath;
654
655	if (dm_ps_use_hr_timer(pgpath->pg->ps.type))
656	mpio->start_time_ns = ktime_get_ns();
657
658	bio->bi_status = 0;
659	bio_set_dev(bio, bdev: pgpath->path.dev->bdev);
660	bio->bi_opf |= REQ_FAILFAST_TRANSPORT;
661
662	if (pgpath->pg->ps.type->start_io)
663	pgpath->pg->ps.type->start_io(&pgpath->pg->ps,
664	&pgpath->path,
665	mpio->nr_bytes);
666	return DM_MAPIO_REMAPPED;
667	}
668
669	static int multipath_map_bio(struct dm_target *ti, struct bio *bio)
670	{
671	struct multipath *m = ti->private;
672	struct dm_mpath_io *mpio = NULL;
673
674	multipath_init_per_bio_data(bio, mpio_p: &mpio);
675	return __multipath_map_bio(m, bio, mpio);
676	}
677
678	static void process_queued_io_list(struct multipath *m)
679	{
680	if (m->queue_mode == DM_TYPE_REQUEST_BASED)
681	dm_mq_kick_requeue_list(md: dm_table_get_md(t: m->ti->table));
682	else if (m->queue_mode == DM_TYPE_BIO_BASED)
683	queue_work(wq: kmultipathd, work: &m->process_queued_bios);
684	}
685
686	static void process_queued_bios(struct work_struct *work)
687	{
688	int r;
689	struct bio *bio;
690	struct bio_list bios;
691	struct blk_plug plug;
692	struct multipath *m =
693	container_of(work, struct multipath, process_queued_bios);
694
695	bio_list_init(bl: &bios);
696
697	spin_lock_irq(lock: &m->lock);
698
699	if (bio_list_empty(bl: &m->queued_bios)) {
700	spin_unlock_irq(lock: &m->lock);
701	return;
702	}
703
704	bio_list_merge_init(bl: &bios, bl2: &m->queued_bios);
705
706	spin_unlock_irq(lock: &m->lock);
707
708	blk_start_plug(&plug);
709	while ((bio = bio_list_pop(bl: &bios))) {
710	struct dm_mpath_io *mpio = get_mpio_from_bio(bio);
711
712	dm_bio_restore(bd: get_bio_details_from_mpio(mpio), bio);
713	r = __multipath_map_bio(m, bio, mpio);
714	switch (r) {
715	case DM_MAPIO_KILL:
716	bio->bi_status = BLK_STS_IOERR;
717	bio_endio(bio);
718	break;
719	case DM_MAPIO_REQUEUE:
720	bio->bi_status = BLK_STS_DM_REQUEUE;
721	bio_endio(bio);
722	break;
723	case DM_MAPIO_REMAPPED:
724	submit_bio_noacct(bio);
725	break;
726	case DM_MAPIO_SUBMITTED:
727	break;
728	default:
729	WARN_ONCE(true, "__multipath_map_bio() returned %d\n", r);
730	}
731	}
732	blk_finish_plug(&plug);
733	}
734
735	/*
736	* If we run out of usable paths, should we queue I/O or error it?
737	*/
738	static int queue_if_no_path(struct multipath *m, bool f_queue_if_no_path,
739	bool save_old_value, const char *caller)
740	{
741	unsigned long flags;
742	bool queue_if_no_path_bit, saved_queue_if_no_path_bit;
743	const char *dm_dev_name = dm_table_device_name(t: m->ti->table);
744
745	DMDEBUG("%s: %s caller=%s f_queue_if_no_path=%d save_old_value=%d",
746	dm_dev_name, __func__, caller, f_queue_if_no_path, save_old_value);
747
748	spin_lock_irqsave(&m->lock, flags);
749
750	queue_if_no_path_bit = test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags);
751	saved_queue_if_no_path_bit = test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags);
752
753	if (save_old_value) {
754	if (unlikely(!queue_if_no_path_bit && saved_queue_if_no_path_bit)) {
755	DMERR("%s: QIFNP disabled but saved as enabled, saving again loses state, not saving!",
756	dm_dev_name);
757	} else
758	assign_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags, queue_if_no_path_bit);
759	} else if (!f_queue_if_no_path && saved_queue_if_no_path_bit) {
760	/* due to "fail_if_no_path" message, need to honor it. */
761	clear_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, addr: &m->flags);
762	}
763	assign_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags, f_queue_if_no_path);
764
765	DMDEBUG("%s: after %s changes; QIFNP = %d; SQIFNP = %d; DNFS = %d",
766	dm_dev_name, __func__,
767	test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags),
768	test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags),
769	dm_noflush_suspending(m->ti));
770
771	spin_unlock_irqrestore(lock: &m->lock, flags);
772
773	if (!f_queue_if_no_path) {
774	dm_table_run_md_queue_async(t: m->ti->table);
775	process_queued_io_list(m);
776	}
777
778	return 0;
779	}
780
781	/*
782	* If the queue_if_no_path timeout fires, turn off queue_if_no_path and
783	* process any queued I/O.
784	*/
785	static void queue_if_no_path_timeout_work(struct timer_list *t)
786	{
787	struct multipath *m = timer_container_of(m, t, nopath_timer);
788
789	DMWARN("queue_if_no_path timeout on %s, failing queued IO",
790	dm_table_device_name(m->ti->table));
791	queue_if_no_path(m, f_queue_if_no_path: false, save_old_value: false, caller: __func__);
792	}
793
794	/*
795	* Enable the queue_if_no_path timeout if necessary.
796	* Called with m->lock held.
797	*/
798	static void enable_nopath_timeout(struct multipath *m)
799	{
800	unsigned long queue_if_no_path_timeout =
801	READ_ONCE(queue_if_no_path_timeout_secs) * HZ;
802
803	lockdep_assert_held(&m->lock);
804
805	if (queue_if_no_path_timeout > 0 &&
806	atomic_read(v: &m->nr_valid_paths) == 0 &&
807	test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
808	mod_timer(timer: &m->nopath_timer,
809	expires: jiffies + queue_if_no_path_timeout);
810	}
811	}
812
813	static void disable_nopath_timeout(struct multipath *m)
814	{
815	timer_delete_sync(timer: &m->nopath_timer);
816	}
817
818	/*
819	* An event is triggered whenever a path is taken out of use.
820	* Includes path failure and PG bypass.
821	*/
822	static void trigger_event(struct work_struct *work)
823	{
824	struct multipath *m =
825	container_of(work, struct multipath, trigger_event);
826
827	dm_table_event(t: m->ti->table);
828	}
829
830	/*
831	*---------------------------------------------------------------
832	* Constructor/argument parsing:
833	* <#multipath feature args> [<arg>]*
834	* <#hw_handler args> [hw_handler [<arg>]*]
835	* <#priority groups>
836	* <initial priority group>
837	* [<selector> <#selector args> [<arg>]*
838	* <#paths> <#per-path selector args>
839	* [<path> [<arg>]* ]+ ]+
840	*---------------------------------------------------------------
841	*/
842	static int parse_path_selector(struct dm_arg_set *as, struct priority_group *pg,
843	struct dm_target *ti)
844	{
845	int r;
846	struct path_selector_type *pst;
847	unsigned int ps_argc;
848
849	static const struct dm_arg _args[] = {
850	{0, 1024, "invalid number of path selector args"},
851	};
852
853	pst = dm_get_path_selector(name: dm_shift_arg(as));
854	if (!pst) {
855	ti->error = "unknown path selector type";
856	return -EINVAL;
857	}
858
859	r = dm_read_arg_group(arg: _args, arg_set: as, num_args: &ps_argc, error: &ti->error);
860	if (r) {
861	dm_put_path_selector(pst);
862	return -EINVAL;
863	}
864
865	r = pst->create(&pg->ps, ps_argc, as->argv);
866	if (r) {
867	dm_put_path_selector(pst);
868	ti->error = "path selector constructor failed";
869	return r;
870	}
871
872	pg->ps.type = pst;
873	dm_consume_args(as, num_args: ps_argc);
874
875	return 0;
876	}
877
878	static int setup_scsi_dh(struct block_device *bdev, struct multipath *m,
879	const char **attached_handler_name, char **error)
880	{
881	struct request_queue *q = bdev_get_queue(bdev);
882	int r;
883
884	if (*attached_handler_name) {
885	/*
886	* Clear any hw_handler_params associated with a
887	* handler that isn't already attached.
888	*/
889	if (m->hw_handler_name && strcmp(*attached_handler_name,
890	m->hw_handler_name)) {
891	kfree(objp: m->hw_handler_params);
892	m->hw_handler_params = NULL;
893	}
894
895	/*
896	* Reset hw_handler_name to match the attached handler
897	*
898	* NB. This modifies the table line to show the actual
899	* handler instead of the original table passed in.
900	*/
901	kfree(objp: m->hw_handler_name);
902	m->hw_handler_name = *attached_handler_name;
903	*attached_handler_name = NULL;
904	}
905
906	if (m->hw_handler_name) {
907	r = scsi_dh_attach(q, m->hw_handler_name);
908	if (r < 0) {
909	*error = "error attaching hardware handler";
910	return r;
911	}
912
913	if (m->hw_handler_params) {
914	r = scsi_dh_set_params(q, m->hw_handler_params);
915	if (r < 0) {
916	*error = "unable to set hardware handler parameters";
917	return r;
918	}
919	}
920	}
921
922	return 0;
923	}
924
925	static struct pgpath *parse_path(struct dm_arg_set *as, struct path_selector *ps,
926	struct dm_target *ti)
927	{
928	int r;
929	struct pgpath *p;
930	struct multipath *m = ti->private;
931	struct request_queue *q;
932	const char *attached_handler_name = NULL;
933
934	/* we need at least a path arg */
935	if (as->argc < 1) {
936	ti->error = "no device given";
937	return ERR_PTR(error: -EINVAL);
938	}
939
940	p = alloc_pgpath();
941	if (!p)
942	return ERR_PTR(error: -ENOMEM);
943
944	r = dm_get_device(ti, path: dm_shift_arg(as), mode: dm_table_get_mode(t: ti->table),
945	result: &p->path.dev);
946	if (r) {
947	ti->error = "error getting device";
948	goto bad;
949	}
950
951	q = bdev_get_queue(bdev: p->path.dev->bdev);
952	attached_handler_name = scsi_dh_attached_handler_name(q, GFP_KERNEL);
953	if (IS_ERR(ptr: attached_handler_name)) {
954	if (PTR_ERR(ptr: attached_handler_name) == -ENODEV) {
955	if (m->hw_handler_name) {
956	DMERR("hardware handlers are only allowed for SCSI devices");
957	kfree(objp: m->hw_handler_name);
958	m->hw_handler_name = NULL;
959	}
960	attached_handler_name = NULL;
961	} else {
962	r = PTR_ERR(ptr: attached_handler_name);
963	goto bad;
964	}
965	}
966	if (attached_handler_name || m->hw_handler_name) {
967	INIT_DELAYED_WORK(&p->activate_path, activate_path_work);
968	r = setup_scsi_dh(bdev: p->path.dev->bdev, m, attached_handler_name: &attached_handler_name, error: &ti->error);
969	kfree(objp: attached_handler_name);
970	if (r) {
971	dm_put_device(ti, d: p->path.dev);
972	goto bad;
973	}
974	}
975
976	r = ps->type->add_path(ps, &p->path, as->argc, as->argv, &ti->error);
977	if (r) {
978	dm_put_device(ti, d: p->path.dev);
979	goto bad;
980	}
981
982	return p;
983	bad:
984	free_pgpath(pgpath: p);
985	return ERR_PTR(error: r);
986	}
987
988	static struct priority_group *parse_priority_group(struct dm_arg_set *as,
989	struct multipath *m)
990	{
991	static const struct dm_arg _args[] = {
992	{1, 1024, "invalid number of paths"},
993	{0, 1024, "invalid number of selector args"}
994	};
995
996	int r;
997	unsigned int i, nr_selector_args, nr_args;
998	struct priority_group *pg;
999	struct dm_target *ti = m->ti;
1000
1001	if (as->argc < 2) {
1002	as->argc = 0;
1003	ti->error = "not enough priority group arguments";
1004	return ERR_PTR(error: -EINVAL);
1005	}
1006
1007	pg = alloc_priority_group();
1008	if (!pg) {
1009	ti->error = "couldn't allocate priority group";
1010	return ERR_PTR(error: -ENOMEM);
1011	}
1012	pg->m = m;
1013
1014	r = parse_path_selector(as, pg, ti);
1015	if (r)
1016	goto bad;
1017
1018	/*
1019	* read the paths
1020	*/
1021	r = dm_read_arg(arg: _args, arg_set: as, value: &pg->nr_pgpaths, error: &ti->error);
1022	if (r)
1023	goto bad;
1024
1025	r = dm_read_arg(arg: _args + 1, arg_set: as, value: &nr_selector_args, error: &ti->error);
1026	if (r)
1027	goto bad;
1028
1029	nr_args = 1 + nr_selector_args;
1030	for (i = 0; i < pg->nr_pgpaths; i++) {
1031	struct pgpath *pgpath;
1032	struct dm_arg_set path_args;
1033
1034	if (as->argc < nr_args) {
1035	ti->error = "not enough path parameters";
1036	r = -EINVAL;
1037	goto bad;
1038	}
1039
1040	path_args.argc = nr_args;
1041	path_args.argv = as->argv;
1042
1043	pgpath = parse_path(as: &path_args, ps: &pg->ps, ti);
1044	if (IS_ERR(ptr: pgpath)) {
1045	r = PTR_ERR(ptr: pgpath);
1046	goto bad;
1047	}
1048
1049	pgpath->pg = pg;
1050	list_add_tail(new: &pgpath->list, head: &pg->pgpaths);
1051	dm_consume_args(as, num_args: nr_args);
1052	}
1053
1054	return pg;
1055
1056	bad:
1057	free_priority_group(pg, ti);
1058	return ERR_PTR(error: r);
1059	}
1060
1061	static int parse_hw_handler(struct dm_arg_set *as, struct multipath *m)
1062	{
1063	unsigned int hw_argc;
1064	int ret;
1065	struct dm_target *ti = m->ti;
1066
1067	static const struct dm_arg _args[] = {
1068	{0, 1024, "invalid number of hardware handler args"},
1069	};
1070
1071	if (dm_read_arg_group(arg: _args, arg_set: as, num_args: &hw_argc, error: &ti->error))
1072	return -EINVAL;
1073
1074	if (!hw_argc)
1075	return 0;
1076
1077	if (m->queue_mode == DM_TYPE_BIO_BASED) {
1078	dm_consume_args(as, num_args: hw_argc);
1079	DMERR("bio-based multipath doesn't allow hardware handler args");
1080	return 0;
1081	}
1082
1083	m->hw_handler_name = kstrdup(s: dm_shift_arg(as), GFP_KERNEL);
1084	if (!m->hw_handler_name)
1085	return -EINVAL;
1086
1087	if (hw_argc > 1) {
1088	char *p;
1089	int i, j, len = 4;
1090
1091	for (i = 0; i <= hw_argc - 2; i++)
1092	len += strlen(as->argv[i]) + 1;
1093	p = m->hw_handler_params = kzalloc(len, GFP_KERNEL);
1094	if (!p) {
1095	ti->error = "memory allocation failed";
1096	ret = -ENOMEM;
1097	goto fail;
1098	}
1099	j = sprintf(buf: p, fmt: "%d", hw_argc - 1);
1100	for (i = 0, p += j + 1; i <= hw_argc - 2; i++, p += j + 1)
1101	j = sprintf(buf: p, fmt: "%s", as->argv[i]);
1102	}
1103	dm_consume_args(as, num_args: hw_argc - 1);
1104
1105	return 0;
1106	fail:
1107	kfree(objp: m->hw_handler_name);
1108	m->hw_handler_name = NULL;
1109	return ret;
1110	}
1111
1112	static int parse_features(struct dm_arg_set *as, struct multipath *m)
1113	{
1114	int r;
1115	unsigned int argc;
1116	struct dm_target *ti = m->ti;
1117	const char *arg_name;
1118
1119	static const struct dm_arg _args[] = {
1120	{0, 8, "invalid number of feature args"},
1121	{1, 50, "pg_init_retries must be between 1 and 50"},
1122	{0, 60000, "pg_init_delay_msecs must be between 0 and 60000"},
1123	};
1124
1125	r = dm_read_arg_group(arg: _args, arg_set: as, num_args: &argc, error: &ti->error);
1126	if (r)
1127	return -EINVAL;
1128
1129	if (!argc)
1130	return 0;
1131
1132	do {
1133	arg_name = dm_shift_arg(as);
1134	argc--;
1135
1136	if (!strcasecmp(s1: arg_name, s2: "queue_if_no_path")) {
1137	r = queue_if_no_path(m, f_queue_if_no_path: true, save_old_value: false, caller: __func__);
1138	continue;
1139	}
1140
1141	if (!strcasecmp(s1: arg_name, s2: "retain_attached_hw_handler")) {
1142	/* no longer has any effect */
1143	continue;
1144	}
1145
1146	if (!strcasecmp(s1: arg_name, s2: "pg_init_retries") &&
1147	(argc >= 1)) {
1148	r = dm_read_arg(arg: _args + 1, arg_set: as, value: &m->pg_init_retries, error: &ti->error);
1149	argc--;
1150	continue;
1151	}
1152
1153	if (!strcasecmp(s1: arg_name, s2: "pg_init_delay_msecs") &&
1154	(argc >= 1)) {
1155	r = dm_read_arg(arg: _args + 2, arg_set: as, value: &m->pg_init_delay_msecs, error: &ti->error);
1156	argc--;
1157	continue;
1158	}
1159
1160	if (!strcasecmp(s1: arg_name, s2: "queue_mode") &&
1161	(argc >= 1)) {
1162	const char *queue_mode_name = dm_shift_arg(as);
1163
1164	if (!strcasecmp(s1: queue_mode_name, s2: "bio"))
1165	m->queue_mode = DM_TYPE_BIO_BASED;
1166	else if (!strcasecmp(s1: queue_mode_name, s2: "rq") ||
1167	!strcasecmp(s1: queue_mode_name, s2: "mq"))
1168	m->queue_mode = DM_TYPE_REQUEST_BASED;
1169	else {
1170	ti->error = "Unknown 'queue_mode' requested";
1171	r = -EINVAL;
1172	}
1173	argc--;
1174	continue;
1175	}
1176
1177	ti->error = "Unrecognised multipath feature request";
1178	r = -EINVAL;
1179	} while (argc && !r);
1180
1181	return r;
1182	}
1183
1184	static int multipath_ctr(struct dm_target *ti, unsigned int argc, char **argv)
1185	{
1186	/* target arguments */
1187	static const struct dm_arg _args[] = {
1188	{0, 1024, "invalid number of priority groups"},
1189	{0, 1024, "invalid initial priority group number"},
1190	};
1191
1192	int r;
1193	struct multipath *m;
1194	struct dm_arg_set as;
1195	unsigned int pg_count = 0;
1196	unsigned int next_pg_num;
1197
1198	as.argc = argc;
1199	as.argv = argv;
1200
1201	m = alloc_multipath(ti);
1202	if (!m) {
1203	ti->error = "can't allocate multipath";
1204	return -EINVAL;
1205	}
1206
1207	r = parse_features(as: &as, m);
1208	if (r)
1209	goto bad;
1210
1211	r = alloc_multipath_stage2(ti, m);
1212	if (r)
1213	goto bad;
1214
1215	r = parse_hw_handler(as: &as, m);
1216	if (r)
1217	goto bad;
1218
1219	r = dm_read_arg(arg: _args, arg_set: &as, value: &m->nr_priority_groups, error: &ti->error);
1220	if (r)
1221	goto bad;
1222
1223	r = dm_read_arg(arg: _args + 1, arg_set: &as, value: &next_pg_num, error: &ti->error);
1224	if (r)
1225	goto bad;
1226
1227	if ((!m->nr_priority_groups && next_pg_num) ||
1228	(m->nr_priority_groups && !next_pg_num)) {
1229	ti->error = "invalid initial priority group";
1230	r = -EINVAL;
1231	goto bad;
1232	}
1233
1234	/* parse the priority groups */
1235	while (as.argc) {
1236	struct priority_group *pg;
1237	unsigned int nr_valid_paths = atomic_read(v: &m->nr_valid_paths);
1238
1239	pg = parse_priority_group(as: &as, m);
1240	if (IS_ERR(ptr: pg)) {
1241	r = PTR_ERR(ptr: pg);
1242	goto bad;
1243	}
1244
1245	nr_valid_paths += pg->nr_pgpaths;
1246	atomic_set(v: &m->nr_valid_paths, i: nr_valid_paths);
1247
1248	list_add_tail(new: &pg->list, head: &m->priority_groups);
1249	pg_count++;
1250	pg->pg_num = pg_count;
1251	if (!--next_pg_num)
1252	m->next_pg = pg;
1253	}
1254
1255	if (pg_count != m->nr_priority_groups) {
1256	ti->error = "priority group count mismatch";
1257	r = -EINVAL;
1258	goto bad;
1259	}
1260
1261	spin_lock_irq(lock: &m->lock);
1262	enable_nopath_timeout(m);
1263	spin_unlock_irq(lock: &m->lock);
1264
1265	ti->num_flush_bios = 1;
1266	ti->num_discard_bios = 1;
1267	ti->num_write_zeroes_bios = 1;
1268	if (m->queue_mode == DM_TYPE_BIO_BASED)
1269	ti->per_io_data_size = multipath_per_bio_data_size();
1270	else
1271	ti->per_io_data_size = sizeof(struct dm_mpath_io);
1272
1273	return 0;
1274
1275	bad:
1276	free_multipath(m);
1277	return r;
1278	}
1279
1280	static void multipath_wait_for_pg_init_completion(struct multipath *m)
1281	{
1282	DEFINE_WAIT(wait);
1283
1284	while (1) {
1285	prepare_to_wait(wq_head: &m->pg_init_wait, wq_entry: &wait, TASK_UNINTERRUPTIBLE);
1286
1287	if (!atomic_read(v: &m->pg_init_in_progress))
1288	break;
1289
1290	io_schedule();
1291	}
1292	finish_wait(wq_head: &m->pg_init_wait, wq_entry: &wait);
1293	}
1294
1295	static void flush_multipath_work(struct multipath *m)
1296	{
1297	if (m->hw_handler_name) {
1298	if (!atomic_read(v: &m->pg_init_in_progress))
1299	goto skip;
1300
1301	spin_lock_irq(lock: &m->lock);
1302	if (atomic_read(v: &m->pg_init_in_progress) &&
1303	!test_and_set_bit(MPATHF_PG_INIT_DISABLED, addr: &m->flags)) {
1304	spin_unlock_irq(lock: &m->lock);
1305
1306	flush_workqueue(kmpath_handlerd);
1307	multipath_wait_for_pg_init_completion(m);
1308
1309	spin_lock_irq(lock: &m->lock);
1310	clear_bit(MPATHF_PG_INIT_DISABLED, addr: &m->flags);
1311	}
1312	spin_unlock_irq(lock: &m->lock);
1313	}
1314	skip:
1315	if (m->queue_mode == DM_TYPE_BIO_BASED)
1316	flush_work(work: &m->process_queued_bios);
1317	flush_work(work: &m->trigger_event);
1318	}
1319
1320	static void multipath_dtr(struct dm_target *ti)
1321	{
1322	struct multipath *m = ti->private;
1323
1324	disable_nopath_timeout(m);
1325	flush_multipath_work(m);
1326	free_multipath(m);
1327	}
1328
1329	/*
1330	* Take a path out of use.
1331	*/
1332	static int fail_path(struct pgpath *pgpath)
1333	{
1334	unsigned long flags;
1335	struct multipath *m = pgpath->pg->m;
1336
1337	spin_lock_irqsave(&m->lock, flags);
1338
1339	if (!pgpath->is_active)
1340	goto out;
1341
1342	DMWARN("%s: Failing path %s.",
1343	dm_table_device_name(m->ti->table),
1344	pgpath->path.dev->name);
1345
1346	pgpath->pg->ps.type->fail_path(&pgpath->pg->ps, &pgpath->path);
1347	pgpath->is_active = false;
1348	pgpath->fail_count++;
1349
1350	atomic_dec(v: &m->nr_valid_paths);
1351
1352	if (pgpath == m->current_pgpath)
1353	m->current_pgpath = NULL;
1354
1355	dm_path_uevent(event_type: DM_UEVENT_PATH_FAILED, ti: m->ti,
1356	path: pgpath->path.dev->name, nr_valid_paths: atomic_read(v: &m->nr_valid_paths));
1357
1358	queue_work(wq: dm_mpath_wq, work: &m->trigger_event);
1359
1360	enable_nopath_timeout(m);
1361
1362	out:
1363	spin_unlock_irqrestore(lock: &m->lock, flags);
1364
1365	return 0;
1366	}
1367
1368	/*
1369	* Reinstate a previously-failed path
1370	*/
1371	static int reinstate_path(struct pgpath *pgpath)
1372	{
1373	int r = 0, run_queue = 0;
1374	struct multipath *m = pgpath->pg->m;
1375	unsigned int nr_valid_paths;
1376
1377	spin_lock_irq(lock: &m->lock);
1378
1379	if (pgpath->is_active)
1380	goto out;
1381
1382	DMWARN("%s: Reinstating path %s.",
1383	dm_table_device_name(m->ti->table),
1384	pgpath->path.dev->name);
1385
1386	r = pgpath->pg->ps.type->reinstate_path(&pgpath->pg->ps, &pgpath->path);
1387	if (r)
1388	goto out;
1389
1390	pgpath->is_active = true;
1391
1392	nr_valid_paths = atomic_inc_return(v: &m->nr_valid_paths);
1393	if (nr_valid_paths == 1) {
1394	m->current_pgpath = NULL;
1395	run_queue = 1;
1396	} else if (m->hw_handler_name && (m->current_pg == pgpath->pg)) {
1397	if (queue_work(wq: kmpath_handlerd, work: &pgpath->activate_path.work))
1398	atomic_inc(v: &m->pg_init_in_progress);
1399	}
1400
1401	dm_path_uevent(event_type: DM_UEVENT_PATH_REINSTATED, ti: m->ti,
1402	path: pgpath->path.dev->name, nr_valid_paths);
1403
1404	schedule_work(work: &m->trigger_event);
1405
1406	out:
1407	spin_unlock_irq(lock: &m->lock);
1408	if (run_queue) {
1409	dm_table_run_md_queue_async(t: m->ti->table);
1410	process_queued_io_list(m);
1411	}
1412
1413	if (pgpath->is_active)
1414	disable_nopath_timeout(m);
1415
1416	return r;
1417	}
1418
1419	/*
1420	* Fail or reinstate all paths that match the provided struct dm_dev.
1421	*/
1422	static int action_dev(struct multipath *m, dev_t dev, action_fn action)
1423	{
1424	int r = -EINVAL;
1425	struct pgpath *pgpath;
1426	struct priority_group *pg;
1427
1428	list_for_each_entry(pg, &m->priority_groups, list) {
1429	list_for_each_entry(pgpath, &pg->pgpaths, list) {
1430	if (pgpath->path.dev->bdev->bd_dev == dev)
1431	r = action(pgpath);
1432	}
1433	}
1434
1435	return r;
1436	}
1437
1438	/*
1439	* Temporarily try to avoid having to use the specified PG
1440	*/
1441	static void bypass_pg(struct multipath *m, struct priority_group *pg,
1442	bool bypassed, bool can_be_delayed)
1443	{
1444	unsigned long flags;
1445
1446	spin_lock_irqsave(&m->lock, flags);
1447
1448	pg->bypassed = bypassed;
1449	if (can_be_delayed && test_bit(MPATHF_DELAY_PG_SWITCH, &m->flags))
1450	set_bit(MPATHF_NEED_PG_SWITCH, addr: &m->flags);
1451	else {
1452	m->current_pgpath = NULL;
1453	m->current_pg = NULL;
1454	}
1455
1456	spin_unlock_irqrestore(lock: &m->lock, flags);
1457
1458	schedule_work(work: &m->trigger_event);
1459	}
1460
1461	/*
1462	* Switch to using the specified PG from the next I/O that gets mapped
1463	*/
1464	static int switch_pg_num(struct multipath *m, const char *pgstr)
1465	{
1466	struct priority_group *pg;
1467	unsigned int pgnum;
1468	char dummy;
1469
1470	if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1471	!m->nr_priority_groups || (pgnum > m->nr_priority_groups)) {
1472	DMWARN("invalid PG number supplied to %s", __func__);
1473	return -EINVAL;
1474	}
1475
1476	spin_lock_irq(lock: &m->lock);
1477	list_for_each_entry(pg, &m->priority_groups, list) {
1478	pg->bypassed = false;
1479	if (--pgnum)
1480	continue;
1481
1482	if (test_bit(MPATHF_DELAY_PG_SWITCH, &m->flags))
1483	set_bit(MPATHF_NEED_PG_SWITCH, addr: &m->flags);
1484	else {
1485	m->current_pgpath = NULL;
1486	m->current_pg = NULL;
1487	}
1488	m->next_pg = pg;
1489	}
1490	spin_unlock_irq(lock: &m->lock);
1491
1492	schedule_work(work: &m->trigger_event);
1493	return 0;
1494	}
1495
1496	/*
1497	* Set/clear bypassed status of a PG.
1498	* PGs are numbered upwards from 1 in the order they were declared.
1499	*/
1500	static int bypass_pg_num(struct multipath *m, const char *pgstr, bool bypassed)
1501	{
1502	struct priority_group *pg;
1503	unsigned int pgnum;
1504	char dummy;
1505
1506	if (!pgstr || (sscanf(pgstr, "%u%c", &pgnum, &dummy) != 1) || !pgnum ||
1507	!m->nr_priority_groups || (pgnum > m->nr_priority_groups)) {
1508	DMWARN("invalid PG number supplied to bypass_pg");
1509	return -EINVAL;
1510	}
1511
1512	list_for_each_entry(pg, &m->priority_groups, list) {
1513	if (!--pgnum)
1514	break;
1515	}
1516
1517	bypass_pg(m, pg, bypassed, can_be_delayed: true);
1518	return 0;
1519	}
1520
1521	/*
1522	* Should we retry pg_init immediately?
1523	*/
1524	static bool pg_init_limit_reached(struct multipath *m, struct pgpath *pgpath)
1525	{
1526	unsigned long flags;
1527	bool limit_reached = false;
1528
1529	spin_lock_irqsave(&m->lock, flags);
1530
1531	if (atomic_read(v: &m->pg_init_count) <= m->pg_init_retries &&
1532	!test_bit(MPATHF_PG_INIT_DISABLED, &m->flags))
1533	set_bit(MPATHF_PG_INIT_REQUIRED, addr: &m->flags);
1534	else
1535	limit_reached = true;
1536
1537	spin_unlock_irqrestore(lock: &m->lock, flags);
1538
1539	return limit_reached;
1540	}
1541
1542	static void pg_init_done(void *data, int errors)
1543	{
1544	struct pgpath *pgpath = data;
1545	struct priority_group *pg = pgpath->pg;
1546	struct multipath *m = pg->m;
1547	unsigned long flags;
1548	bool delay_retry = false;
1549
1550	/* device or driver problems */
1551	switch (errors) {
1552	case SCSI_DH_OK:
1553	break;
1554	case SCSI_DH_NOSYS:
1555	if (!m->hw_handler_name) {
1556	errors = 0;
1557	break;
1558	}
1559	DMERR("Could not failover the device: Handler scsi_dh_%s "
1560	"Error %d.", m->hw_handler_name, errors);
1561	/*
1562	* Fail path for now, so we do not ping pong
1563	*/
1564	fail_path(pgpath);
1565	break;
1566	case SCSI_DH_DEV_TEMP_BUSY:
1567	/*
1568	* Probably doing something like FW upgrade on the
1569	* controller so try the other pg.
1570	*/
1571	bypass_pg(m, pg, bypassed: true, can_be_delayed: false);
1572	break;
1573	case SCSI_DH_RETRY:
1574	/* Wait before retrying. */
1575	delay_retry = true;
1576	fallthrough;
1577	case SCSI_DH_IMM_RETRY:
1578	case SCSI_DH_RES_TEMP_UNAVAIL:
1579	if (pg_init_limit_reached(m, pgpath))
1580	fail_path(pgpath);
1581	errors = 0;
1582	break;
1583	case SCSI_DH_DEV_OFFLINED:
1584	default:
1585	/*
1586	* We probably do not want to fail the path for a device
1587	* error, but this is what the old dm did. In future
1588	* patches we can do more advanced handling.
1589	*/
1590	fail_path(pgpath);
1591	}
1592
1593	spin_lock_irqsave(&m->lock, flags);
1594	if (errors) {
1595	if (pgpath == m->current_pgpath) {
1596	DMERR("Could not failover device. Error %d.", errors);
1597	m->current_pgpath = NULL;
1598	m->current_pg = NULL;
1599	}
1600	} else if (!test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
1601	pg->bypassed = false;
1602
1603	if (atomic_dec_return(v: &m->pg_init_in_progress) > 0)
1604	/* Activations of other paths are still on going */
1605	goto out;
1606
1607	if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
1608	if (delay_retry)
1609	set_bit(MPATHF_PG_INIT_DELAY_RETRY, addr: &m->flags);
1610	else
1611	clear_bit(MPATHF_PG_INIT_DELAY_RETRY, addr: &m->flags);
1612
1613	if (__pg_init_all_paths(m))
1614	goto out;
1615	}
1616	clear_bit(MPATHF_QUEUE_IO, addr: &m->flags);
1617
1618	process_queued_io_list(m);
1619
1620	/*
1621	* Wake up any thread waiting to suspend.
1622	*/
1623	wake_up(&m->pg_init_wait);
1624
1625	out:
1626	spin_unlock_irqrestore(lock: &m->lock, flags);
1627	}
1628
1629	static void activate_or_offline_path(struct pgpath *pgpath)
1630	{
1631	struct request_queue *q = bdev_get_queue(bdev: pgpath->path.dev->bdev);
1632
1633	if (pgpath->is_active && !blk_queue_dying(q))
1634	scsi_dh_activate(q, pg_init_done, pgpath);
1635	else
1636	pg_init_done(data: pgpath, errors: SCSI_DH_DEV_OFFLINED);
1637	}
1638
1639	static void activate_path_work(struct work_struct *work)
1640	{
1641	struct pgpath *pgpath =
1642	container_of(work, struct pgpath, activate_path.work);
1643
1644	activate_or_offline_path(pgpath);
1645	}
1646
1647	static int multipath_end_io(struct dm_target *ti, struct request *clone,
1648	blk_status_t error, union map_info *map_context)
1649	{
1650	struct dm_mpath_io *mpio = get_mpio(info: map_context);
1651	struct pgpath *pgpath = mpio->pgpath;
1652	int r = DM_ENDIO_DONE;
1653
1654	/*
1655	* We don't queue any clone request inside the multipath target
1656	* during end I/O handling, since those clone requests don't have
1657	* bio clones. If we queue them inside the multipath target,
1658	* we need to make bio clones, that requires memory allocation.
1659	* (See drivers/md/dm-rq.c:end_clone_bio() about why the clone requests
1660	* don't have bio clones.)
1661	* Instead of queueing the clone request here, we queue the original
1662	* request into dm core, which will remake a clone request and
1663	* clone bios for it and resubmit it later.
1664	*/
1665	if (error && blk_path_error(error)) {
1666	struct multipath *m = ti->private;
1667
1668	if (error == BLK_STS_RESOURCE)
1669	r = DM_ENDIO_DELAY_REQUEUE;
1670	else
1671	r = DM_ENDIO_REQUEUE;
1672
1673	if (pgpath)
1674	fail_path(pgpath);
1675
1676	if (!atomic_read(v: &m->nr_valid_paths) &&
1677	!must_push_back_rq(m)) {
1678	if (error == BLK_STS_IOERR)
1679	dm_report_EIO(m);
1680	/* complete with the original error */
1681	r = DM_ENDIO_DONE;
1682	}
1683	}
1684
1685	if (pgpath) {
1686	struct path_selector *ps = &pgpath->pg->ps;
1687
1688	if (ps->type->end_io)
1689	ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes,
1690	clone->io_start_time_ns);
1691	}
1692
1693	return r;
1694	}
1695
1696	static int multipath_end_io_bio(struct dm_target *ti, struct bio *clone,
1697	blk_status_t *error)
1698	{
1699	struct multipath *m = ti->private;
1700	struct dm_mpath_io *mpio = get_mpio_from_bio(bio: clone);
1701	struct pgpath *pgpath = mpio->pgpath;
1702	unsigned long flags;
1703	int r = DM_ENDIO_DONE;
1704
1705	if (!*error || !blk_path_error(error: *error))
1706	goto done;
1707
1708	if (pgpath)
1709	fail_path(pgpath);
1710
1711	if (!atomic_read(v: &m->nr_valid_paths)) {
1712	spin_lock_irqsave(&m->lock, flags);
1713	if (!test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
1714	if (__must_push_back(m)) {
1715	r = DM_ENDIO_REQUEUE;
1716	} else {
1717	dm_report_EIO(m);
1718	*error = BLK_STS_IOERR;
1719	}
1720	spin_unlock_irqrestore(lock: &m->lock, flags);
1721	goto done;
1722	}
1723	spin_unlock_irqrestore(lock: &m->lock, flags);
1724	}
1725
1726	multipath_queue_bio(m, bio: clone);
1727	r = DM_ENDIO_INCOMPLETE;
1728	done:
1729	if (pgpath) {
1730	struct path_selector *ps = &pgpath->pg->ps;
1731
1732	if (ps->type->end_io)
1733	ps->type->end_io(ps, &pgpath->path, mpio->nr_bytes,
1734	(mpio->start_time_ns ?:
1735	dm_start_time_ns_from_clone(bio: clone)));
1736	}
1737
1738	return r;
1739	}
1740
1741	/*
1742	* Suspend with flush can't complete until all the I/O is processed
1743	* so if the last path fails we must error any remaining I/O.
1744	* - Note that if the freeze_bdev fails while suspending, the
1745	* queue_if_no_path state is lost - userspace should reset it.
1746	* Otherwise, during noflush suspend, queue_if_no_path will not change.
1747	*/
1748	static void multipath_presuspend(struct dm_target *ti)
1749	{
1750	struct multipath *m = ti->private;
1751
1752	spin_lock_irq(lock: &m->lock);
1753	m->is_suspending = true;
1754	spin_unlock_irq(lock: &m->lock);
1755	/* FIXME: bio-based shouldn't need to always disable queue_if_no_path */
1756	if (m->queue_mode == DM_TYPE_BIO_BASED || !dm_noflush_suspending(ti: m->ti))
1757	queue_if_no_path(m, f_queue_if_no_path: false, save_old_value: true, caller: __func__);
1758	}
1759
1760	static void multipath_postsuspend(struct dm_target *ti)
1761	{
1762	struct multipath *m = ti->private;
1763
1764	mutex_lock(&m->work_mutex);
1765	flush_multipath_work(m);
1766	mutex_unlock(lock: &m->work_mutex);
1767	}
1768
1769	/*
1770	* Restore the queue_if_no_path setting.
1771	*/
1772	static void multipath_resume(struct dm_target *ti)
1773	{
1774	struct multipath *m = ti->private;
1775
1776	spin_lock_irq(lock: &m->lock);
1777	m->is_suspending = false;
1778	if (test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags)) {
1779	set_bit(MPATHF_QUEUE_IF_NO_PATH, addr: &m->flags);
1780	clear_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, addr: &m->flags);
1781	}
1782
1783	DMDEBUG("%s: %s finished; QIFNP = %d; SQIFNP = %d",
1784	dm_table_device_name(m->ti->table), __func__,
1785	test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags),
1786	test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags));
1787
1788	spin_unlock_irq(lock: &m->lock);
1789	}
1790
1791	/*
1792	* Info output has the following format:
1793	* num_multipath_feature_args [multipath_feature_args]*
1794	* num_handler_status_args [handler_status_args]*
1795	* num_groups init_group_number
1796	* [A|D|E num_ps_status_args [ps_status_args]*
1797	* num_paths num_selector_args
1798	* [path_dev A|F fail_count [selector_args]* ]+ ]+
1799	*
1800	* Table output has the following format (identical to the constructor string):
1801	* num_feature_args [features_args]*
1802	* num_handler_args hw_handler [hw_handler_args]*
1803	* num_groups init_group_number
1804	* [priority selector-name num_ps_args [ps_args]*
1805	* num_paths num_selector_args [path_dev [selector_args]* ]+ ]+
1806	*/
1807	static void multipath_status(struct dm_target *ti, status_type_t type,
1808	unsigned int status_flags, char *result, unsigned int maxlen)
1809	{
1810	int sz = 0, pg_counter, pgpath_counter;
1811	struct multipath *m = ti->private;
1812	struct priority_group *pg;
1813	struct pgpath *p;
1814	unsigned int pg_num;
1815	char state;
1816
1817	spin_lock_irq(lock: &m->lock);
1818
1819	/* Features */
1820	if (type == STATUSTYPE_INFO)
1821	DMEMIT("2 %u %u ", test_bit(MPATHF_QUEUE_IO, &m->flags),
1822	atomic_read(&m->pg_init_count));
1823	else {
1824	DMEMIT("%u ", test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags) +
1825	(m->pg_init_retries > 0) * 2 +
1826	(m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT) * 2 +
1827	(m->queue_mode != DM_TYPE_REQUEST_BASED) * 2);
1828
1829	if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
1830	DMEMIT("queue_if_no_path ");
1831	if (m->pg_init_retries)
1832	DMEMIT("pg_init_retries %u ", m->pg_init_retries);
1833	if (m->pg_init_delay_msecs != DM_PG_INIT_DELAY_DEFAULT)
1834	DMEMIT("pg_init_delay_msecs %u ", m->pg_init_delay_msecs);
1835	if (m->queue_mode != DM_TYPE_REQUEST_BASED) {
1836	switch (m->queue_mode) {
1837	case DM_TYPE_BIO_BASED:
1838	DMEMIT("queue_mode bio ");
1839	break;
1840	default:
1841	WARN_ON_ONCE(true);
1842	break;
1843	}
1844	}
1845	}
1846
1847	if (!m->hw_handler_name || type == STATUSTYPE_INFO)
1848	DMEMIT("0 ");
1849	else
1850	DMEMIT("1 %s ", m->hw_handler_name);
1851
1852	DMEMIT("%u ", m->nr_priority_groups);
1853
1854	if (m->current_pg)
1855	pg_num = m->current_pg->pg_num;
1856	else if (m->next_pg)
1857	pg_num = m->next_pg->pg_num;
1858	else
1859	pg_num = (m->nr_priority_groups ? 1 : 0);
1860
1861	DMEMIT("%u ", pg_num);
1862
1863	switch (type) {
1864	case STATUSTYPE_INFO:
1865	list_for_each_entry(pg, &m->priority_groups, list) {
1866	if (pg->bypassed)
1867	state = 'D'; /* Disabled */
1868	else if (pg == m->current_pg)
1869	state = 'A'; /* Currently Active */
1870	else
1871	state = 'E'; /* Enabled */
1872
1873	DMEMIT("%c ", state);
1874
1875	if (pg->ps.type->status)
1876	sz += pg->ps.type->status(&pg->ps, NULL, type,
1877	result + sz,
1878	maxlen - sz);
1879	else
1880	DMEMIT("0 ");
1881
1882	DMEMIT("%u %u ", pg->nr_pgpaths,
1883	pg->ps.type->info_args);
1884
1885	list_for_each_entry(p, &pg->pgpaths, list) {
1886	DMEMIT("%s %s %u ", p->path.dev->name,
1887	p->is_active ? "A" : "F",
1888	p->fail_count);
1889	if (pg->ps.type->status)
1890	sz += pg->ps.type->status(&pg->ps,
1891	&p->path, type, result + sz,
1892	maxlen - sz);
1893	}
1894	}
1895	break;
1896
1897	case STATUSTYPE_TABLE:
1898	list_for_each_entry(pg, &m->priority_groups, list) {
1899	DMEMIT("%s ", pg->ps.type->name);
1900
1901	if (pg->ps.type->status)
1902	sz += pg->ps.type->status(&pg->ps, NULL, type,
1903	result + sz,
1904	maxlen - sz);
1905	else
1906	DMEMIT("0 ");
1907
1908	DMEMIT("%u %u ", pg->nr_pgpaths,
1909	pg->ps.type->table_args);
1910
1911	list_for_each_entry(p, &pg->pgpaths, list) {
1912	DMEMIT("%s ", p->path.dev->name);
1913	if (pg->ps.type->status)
1914	sz += pg->ps.type->status(&pg->ps,
1915	&p->path, type, result + sz,
1916	maxlen - sz);
1917	}
1918	}
1919	break;
1920
1921	case STATUSTYPE_IMA:
1922	sz = 0; /*reset the result pointer*/
1923
1924	DMEMIT_TARGET_NAME_VERSION(ti->type);
1925	DMEMIT(",nr_priority_groups=%u", m->nr_priority_groups);
1926
1927	pg_counter = 0;
1928	list_for_each_entry(pg, &m->priority_groups, list) {
1929	if (pg->bypassed)
1930	state = 'D'; /* Disabled */
1931	else if (pg == m->current_pg)
1932	state = 'A'; /* Currently Active */
1933	else
1934	state = 'E'; /* Enabled */
1935	DMEMIT(",pg_state_%d=%c", pg_counter, state);
1936	DMEMIT(",nr_pgpaths_%d=%u", pg_counter, pg->nr_pgpaths);
1937	DMEMIT(",path_selector_name_%d=%s", pg_counter, pg->ps.type->name);
1938
1939	pgpath_counter = 0;
1940	list_for_each_entry(p, &pg->pgpaths, list) {
1941	DMEMIT(",path_name_%d_%d=%s,is_active_%d_%d=%c,fail_count_%d_%d=%u",
1942	pg_counter, pgpath_counter, p->path.dev->name,
1943	pg_counter, pgpath_counter, p->is_active ? 'A' : 'F',
1944	pg_counter, pgpath_counter, p->fail_count);
1945	if (pg->ps.type->status) {
1946	DMEMIT(",path_selector_status_%d_%d=",
1947	pg_counter, pgpath_counter);
1948	sz += pg->ps.type->status(&pg->ps, &p->path,
1949	type, result + sz,
1950	maxlen - sz);
1951	}
1952	pgpath_counter++;
1953	}
1954	pg_counter++;
1955	}
1956	DMEMIT(";");
1957	break;
1958	}
1959
1960	spin_unlock_irq(lock: &m->lock);
1961	}
1962
1963	static int multipath_message(struct dm_target *ti, unsigned int argc, char **argv,
1964	char *result, unsigned int maxlen)
1965	{
1966	int r = -EINVAL;
1967	dev_t dev;
1968	struct multipath *m = ti->private;
1969	action_fn action;
1970
1971	mutex_lock(&m->work_mutex);
1972
1973	if (dm_suspended(ti)) {
1974	r = -EBUSY;
1975	goto out;
1976	}
1977
1978	if (argc == 1) {
1979	if (!strcasecmp(s1: argv[0], s2: "queue_if_no_path")) {
1980	r = queue_if_no_path(m, f_queue_if_no_path: true, save_old_value: false, caller: __func__);
1981	spin_lock_irq(lock: &m->lock);
1982	enable_nopath_timeout(m);
1983	spin_unlock_irq(lock: &m->lock);
1984	goto out;
1985	} else if (!strcasecmp(s1: argv[0], s2: "fail_if_no_path")) {
1986	r = queue_if_no_path(m, f_queue_if_no_path: false, save_old_value: false, caller: __func__);
1987	disable_nopath_timeout(m);
1988	goto out;
1989	}
1990	}
1991
1992	if (argc != 2) {
1993	DMWARN("Invalid multipath message arguments. Expected 2 arguments, got %d.", argc);
1994	goto out;
1995	}
1996
1997	if (!strcasecmp(s1: argv[0], s2: "disable_group")) {
1998	r = bypass_pg_num(m, pgstr: argv[1], bypassed: true);
1999	goto out;
2000	} else if (!strcasecmp(s1: argv[0], s2: "enable_group")) {
2001	r = bypass_pg_num(m, pgstr: argv[1], bypassed: false);
2002	goto out;
2003	} else if (!strcasecmp(s1: argv[0], s2: "switch_group")) {
2004	r = switch_pg_num(m, pgstr: argv[1]);
2005	goto out;
2006	} else if (!strcasecmp(s1: argv[0], s2: "reinstate_path"))
2007	action = reinstate_path;
2008	else if (!strcasecmp(s1: argv[0], s2: "fail_path"))
2009	action = fail_path;
2010	else {
2011	DMWARN("Unrecognised multipath message received: %s", argv[0]);
2012	goto out;
2013	}
2014
2015	r = dm_devt_from_path(path: argv[1], dev_p: &dev);
2016	if (r) {
2017	DMWARN("message: error getting device %s",
2018	argv[1]);
2019	goto out;
2020	}
2021
2022	r = action_dev(m, dev, action);
2023
2024	out:
2025	mutex_unlock(lock: &m->work_mutex);
2026	return r;
2027	}
2028
2029	/*
2030	* Perform a minimal read from the given path to find out whether the
2031	* path still works. If a path error occurs, fail it.
2032	*/
2033	static int probe_path(struct pgpath *pgpath)
2034	{
2035	struct block_device *bdev = pgpath->path.dev->bdev;
2036	unsigned int read_size = bdev_logical_block_size(bdev);
2037	struct page *page;
2038	struct bio *bio;
2039	blk_status_t status;
2040	int r = 0;
2041
2042	if (WARN_ON_ONCE(read_size > PAGE_SIZE))
2043	return -EINVAL;
2044
2045	page = alloc_page(GFP_KERNEL);
2046	if (!page)
2047	return -ENOMEM;
2048
2049	/* Perform a minimal read: Sector 0, length read_size */
2050	bio = bio_alloc(bdev, nr_vecs: 1, opf: REQ_OP_READ, GFP_KERNEL);
2051	if (!bio) {
2052	r = -ENOMEM;
2053	goto out;
2054	}
2055
2056	bio->bi_iter.bi_sector = 0;
2057	__bio_add_page(bio, page, len: read_size, off: 0);
2058	submit_bio_wait(bio);
2059	status = bio->bi_status;
2060	bio_put(bio);
2061
2062	if (status && blk_path_error(error: status))
2063	fail_path(pgpath);
2064
2065	out:
2066	__free_page(page);
2067	return r;
2068	}
2069
2070	/*
2071	* Probe all active paths in current_pg to find out whether they still work.
2072	* Fail all paths that do not work.
2073	*
2074	* Return -ENOTCONN if no valid path is left (even outside of current_pg). We
2075	* cannot probe paths in other pgs without switching current_pg, so if valid
2076	* paths are only in different pgs, they may or may not work. Additionally
2077	* we should not probe paths in a pathgroup that is in the process of
2078	* Initializing. Userspace can submit a request and we'll switch and wait
2079	* for the pathgroup to be initialized. If the request fails, it may need to
2080	* probe again.
2081	*/
2082	static int probe_active_paths(struct multipath *m)
2083	{
2084	struct pgpath *pgpath;
2085	struct priority_group *pg = NULL;
2086	int r = 0;
2087
2088	spin_lock_irq(lock: &m->lock);
2089	if (test_bit(MPATHF_DELAY_PG_SWITCH, &m->flags)) {
2090	wait_event_lock_irq(m->probe_wait,
2091	!test_bit(MPATHF_DELAY_PG_SWITCH, &m->flags),
2092	m->lock);
2093	/*
2094	* if we waited because a probe was already in progress,
2095	* and it probed the current active pathgroup, don't
2096	* reprobe. Just return the number of valid paths
2097	*/
2098	if (m->current_pg == m->last_probed_pg)
2099	goto skip_probe;
2100	}
2101	if (!m->current_pg || m->is_suspending ||
2102	test_bit(MPATHF_QUEUE_IO, &m->flags))
2103	goto skip_probe;
2104	set_bit(MPATHF_DELAY_PG_SWITCH, addr: &m->flags);
2105	pg = m->last_probed_pg = m->current_pg;
2106	spin_unlock_irq(lock: &m->lock);
2107
2108	list_for_each_entry(pgpath, &pg->pgpaths, list) {
2109	if (pg != READ_ONCE(m->current_pg) ||
2110	READ_ONCE(m->is_suspending))
2111	goto out;
2112	if (!pgpath->is_active)
2113	continue;
2114
2115	r = probe_path(pgpath);
2116	if (r < 0)
2117	goto out;
2118	}
2119
2120	out:
2121	spin_lock_irq(lock: &m->lock);
2122	clear_bit(MPATHF_DELAY_PG_SWITCH, addr: &m->flags);
2123	if (test_and_clear_bit(MPATHF_NEED_PG_SWITCH, addr: &m->flags)) {
2124	m->current_pgpath = NULL;
2125	m->current_pg = NULL;
2126	}
2127	skip_probe:
2128	if (r == 0 && !atomic_read(v: &m->nr_valid_paths))
2129	r = -ENOTCONN;
2130	spin_unlock_irq(lock: &m->lock);
2131	if (pg)
2132	wake_up(&m->probe_wait);
2133	return r;
2134	}
2135
2136	static int multipath_prepare_ioctl(struct dm_target *ti,
2137	struct block_device **bdev,
2138	unsigned int cmd, unsigned long arg,
2139	bool *forward)
2140	{
2141	struct multipath *m = ti->private;
2142	struct pgpath *pgpath;
2143	int r;
2144
2145	if (_IOC_TYPE(cmd) == DM_IOCTL) {
2146	*forward = false;
2147	switch (cmd) {
2148	case DM_MPATH_PROBE_PATHS:
2149	return probe_active_paths(m);
2150	default:
2151	return -ENOTTY;
2152	}
2153	}
2154
2155	pgpath = READ_ONCE(m->current_pgpath);
2156	if (!pgpath || !mpath_double_check_test_bit(MPATHF_QUEUE_IO, m))
2157	pgpath = choose_pgpath(m, nr_bytes: 0);
2158
2159	if (pgpath) {
2160	if (!mpath_double_check_test_bit(MPATHF_QUEUE_IO, m)) {
2161	*bdev = pgpath->path.dev->bdev;
2162	r = 0;
2163	} else {
2164	/* pg_init has not started or completed */
2165	r = -ENOTCONN;
2166	}
2167	} else {
2168	/* No path is available */
2169	r = -EIO;
2170	spin_lock_irq(lock: &m->lock);
2171	if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags))
2172	r = -ENOTCONN;
2173	spin_unlock_irq(lock: &m->lock);
2174	}
2175
2176	if (r == -ENOTCONN) {
2177	if (!READ_ONCE(m->current_pg)) {
2178	/* Path status changed, redo selection */
2179	(void) choose_pgpath(m, nr_bytes: 0);
2180	}
2181	spin_lock_irq(lock: &m->lock);
2182	if (test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags))
2183	(void) __pg_init_all_paths(m);
2184	spin_unlock_irq(lock: &m->lock);
2185	dm_table_run_md_queue_async(t: m->ti->table);
2186	process_queued_io_list(m);
2187	}
2188
2189	/*
2190	* Only pass ioctls through if the device sizes match exactly.
2191	*/
2192	if (!r && ti->len != bdev_nr_sectors(bdev: (*bdev)))
2193	return 1;
2194	return r;
2195	}
2196
2197	static int multipath_iterate_devices(struct dm_target *ti,
2198	iterate_devices_callout_fn fn, void *data)
2199	{
2200	struct multipath *m = ti->private;
2201	struct priority_group *pg;
2202	struct pgpath *p;
2203	int ret = 0;
2204
2205	list_for_each_entry(pg, &m->priority_groups, list) {
2206	list_for_each_entry(p, &pg->pgpaths, list) {
2207	ret = fn(ti, p->path.dev, ti->begin, ti->len, data);
2208	if (ret)
2209	goto out;
2210	}
2211	}
2212
2213	out:
2214	return ret;
2215	}
2216
2217	static int pgpath_busy(struct pgpath *pgpath)
2218	{
2219	struct request_queue *q = bdev_get_queue(bdev: pgpath->path.dev->bdev);
2220
2221	return blk_lld_busy(q);
2222	}
2223
2224	/*
2225	* We return "busy", only when we can map I/Os but underlying devices
2226	* are busy (so even if we map I/Os now, the I/Os will wait on
2227	* the underlying queue).
2228	* In other words, if we want to kill I/Os or queue them inside us
2229	* due to map unavailability, we don't return "busy". Otherwise,
2230	* dm core won't give us the I/Os and we can't do what we want.
2231	*/
2232	static int multipath_busy(struct dm_target *ti)
2233	{
2234	bool busy = false, has_active = false;
2235	struct multipath *m = ti->private;
2236	struct priority_group *pg, *next_pg;
2237	struct pgpath *pgpath;
2238
2239	/* pg_init in progress */
2240	if (atomic_read(v: &m->pg_init_in_progress))
2241	return true;
2242
2243	/* no paths available, for blk-mq: rely on IO mapping to delay requeue */
2244	if (!atomic_read(v: &m->nr_valid_paths)) {
2245	unsigned long flags;
2246
2247	spin_lock_irqsave(&m->lock, flags);
2248	if (test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) {
2249	spin_unlock_irqrestore(lock: &m->lock, flags);
2250	return (m->queue_mode != DM_TYPE_REQUEST_BASED);
2251	}
2252	spin_unlock_irqrestore(lock: &m->lock, flags);
2253	}
2254
2255	/* Guess which priority_group will be used at next mapping time */
2256	pg = READ_ONCE(m->current_pg);
2257	next_pg = READ_ONCE(m->next_pg);
2258	if (unlikely(!READ_ONCE(m->current_pgpath) && next_pg))
2259	pg = next_pg;
2260
2261	if (!pg) {
2262	/*
2263	* We don't know which pg will be used at next mapping time.
2264	* We don't call choose_pgpath() here to avoid to trigger
2265	* pg_init just by busy checking.
2266	* So we don't know whether underlying devices we will be using
2267	* at next mapping time are busy or not. Just try mapping.
2268	*/
2269	return busy;
2270	}
2271
2272	/*
2273	* If there is one non-busy active path at least, the path selector
2274	* will be able to select it. So we consider such a pg as not busy.
2275	*/
2276	busy = true;
2277	list_for_each_entry(pgpath, &pg->pgpaths, list) {
2278	if (pgpath->is_active) {
2279	has_active = true;
2280	if (!pgpath_busy(pgpath)) {
2281	busy = false;
2282	break;
2283	}
2284	}
2285	}
2286
2287	if (!has_active) {
2288	/*
2289	* No active path in this pg, so this pg won't be used and
2290	* the current_pg will be changed at next mapping time.
2291	* We need to try mapping to determine it.
2292	*/
2293	busy = false;
2294	}
2295
2296	return busy;
2297	}
2298
2299	/*
2300	*---------------------------------------------------------------
2301	* Module setup
2302	*---------------------------------------------------------------
2303	*/
2304	static struct target_type multipath_target = {
2305	.name = "multipath",
2306	.version = {1, 15, 0},
2307	.features = DM_TARGET_SINGLETON | DM_TARGET_IMMUTABLE |
2308	DM_TARGET_PASSES_INTEGRITY | DM_TARGET_ATOMIC_WRITES,
2309	.module = THIS_MODULE,
2310	.ctr = multipath_ctr,
2311	.dtr = multipath_dtr,
2312	.clone_and_map_rq = multipath_clone_and_map,
2313	.release_clone_rq = multipath_release_clone,
2314	.rq_end_io = multipath_end_io,
2315	.map = multipath_map_bio,
2316	.end_io = multipath_end_io_bio,
2317	.presuspend = multipath_presuspend,
2318	.postsuspend = multipath_postsuspend,
2319	.resume = multipath_resume,
2320	.status = multipath_status,
2321	.message = multipath_message,
2322	.prepare_ioctl = multipath_prepare_ioctl,
2323	.iterate_devices = multipath_iterate_devices,
2324	.busy = multipath_busy,
2325	};
2326
2327	static int __init dm_multipath_init(void)
2328	{
2329	int r = -ENOMEM;
2330
2331	kmultipathd = alloc_workqueue("kmpathd", WQ_MEM_RECLAIM, 0);
2332	if (!kmultipathd) {
2333	DMERR("failed to create workqueue kmpathd");
2334	goto bad_alloc_kmultipathd;
2335	}
2336
2337	/*
2338	* A separate workqueue is used to handle the device handlers
2339	* to avoid overloading existing workqueue. Overloading the
2340	* old workqueue would also create a bottleneck in the
2341	* path of the storage hardware device activation.
2342	*/
2343	kmpath_handlerd = alloc_ordered_workqueue("kmpath_handlerd",
2344	WQ_MEM_RECLAIM);
2345	if (!kmpath_handlerd) {
2346	DMERR("failed to create workqueue kmpath_handlerd");
2347	goto bad_alloc_kmpath_handlerd;
2348	}
2349
2350	dm_mpath_wq = alloc_workqueue("dm_mpath_wq", 0, 0);
2351	if (!dm_mpath_wq) {
2352	DMERR("failed to create workqueue dm_mpath_wq");
2353	goto bad_alloc_dm_mpath_wq;
2354	}
2355
2356	r = dm_register_target(t: &multipath_target);
2357	if (r < 0)
2358	goto bad_register_target;
2359
2360	return 0;
2361
2362	bad_register_target:
2363	destroy_workqueue(wq: dm_mpath_wq);
2364	bad_alloc_dm_mpath_wq:
2365	destroy_workqueue(wq: kmpath_handlerd);
2366	bad_alloc_kmpath_handlerd:
2367	destroy_workqueue(wq: kmultipathd);
2368	bad_alloc_kmultipathd:
2369	return r;
2370	}
2371
2372	static void __exit dm_multipath_exit(void)
2373	{
2374	destroy_workqueue(wq: dm_mpath_wq);
2375	destroy_workqueue(wq: kmpath_handlerd);
2376	destroy_workqueue(wq: kmultipathd);
2377
2378	dm_unregister_target(t: &multipath_target);
2379	}
2380
2381	module_init(dm_multipath_init);
2382	module_exit(dm_multipath_exit);
2383
2384	module_param_named(queue_if_no_path_timeout_secs, queue_if_no_path_timeout_secs, ulong, 0644);
2385	MODULE_PARM_DESC(queue_if_no_path_timeout_secs, "No available paths queue IO timeout in seconds");
2386
2387	MODULE_DESCRIPTION(DM_NAME " multipath target");
2388	MODULE_AUTHOR("Sistina Software <dm-devel@lists.linux.dev>");
2389	MODULE_LICENSE("GPL");
2390