0a7e99d62c69048d7000d3dc6bbcaa3320c742b5
[sfrench/cifs-2.6.git] / drivers / md / md-multipath.c
1 /*
2  * multipath.c : Multiple Devices driver for Linux
3  *
4  * Copyright (C) 1999, 2000, 2001 Ingo Molnar, Red Hat
5  *
6  * Copyright (C) 1996, 1997, 1998 Ingo Molnar, Miguel de Icaza, Gadi Oxman
7  *
8  * MULTIPATH management functions.
9  *
10  * derived from raid1.c.
11  *
12  * This program is free software; you can redistribute it and/or modify
13  * it under the terms of the GNU General Public License as published by
14  * the Free Software Foundation; either version 2, or (at your option)
15  * any later version.
16  *
17  * You should have received a copy of the GNU General Public License
18  * (for example /usr/src/linux/COPYING); if not, write to the Free
19  * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
20  */
21
22 #include <linux/blkdev.h>
23 #include <linux/module.h>
24 #include <linux/raid/md_u.h>
25 #include <linux/seq_file.h>
26 #include <linux/slab.h>
27 #include "md.h"
28 #include "md-multipath.h"
29
30 #define MAX_WORK_PER_DISK 128
31
32 #define NR_RESERVED_BUFS        32
33
34 static int multipath_map (struct mpconf *conf)
35 {
36         int i, disks = conf->raid_disks;
37
38         /*
39          * Later we do read balancing on the read side
40          * now we use the first available disk.
41          */
42
43         rcu_read_lock();
44         for (i = 0; i < disks; i++) {
45                 struct md_rdev *rdev = rcu_dereference(conf->multipaths[i].rdev);
46                 if (rdev && test_bit(In_sync, &rdev->flags) &&
47                     !test_bit(Faulty, &rdev->flags)) {
48                         atomic_inc(&rdev->nr_pending);
49                         rcu_read_unlock();
50                         return i;
51                 }
52         }
53         rcu_read_unlock();
54
55         pr_crit_ratelimited("multipath_map(): no more operational IO paths?\n");
56         return (-1);
57 }
58
59 static void multipath_reschedule_retry (struct multipath_bh *mp_bh)
60 {
61         unsigned long flags;
62         struct mddev *mddev = mp_bh->mddev;
63         struct mpconf *conf = mddev->private;
64
65         spin_lock_irqsave(&conf->device_lock, flags);
66         list_add(&mp_bh->retry_list, &conf->retry_list);
67         spin_unlock_irqrestore(&conf->device_lock, flags);
68         md_wakeup_thread(mddev->thread);
69 }
70
71 /*
72  * multipath_end_bh_io() is called when we have finished servicing a multipathed
73  * operation and are ready to return a success/failure code to the buffer
74  * cache layer.
75  */
76 static void multipath_end_bh_io(struct multipath_bh *mp_bh, blk_status_t status)
77 {
78         struct bio *bio = mp_bh->master_bio;
79         struct mpconf *conf = mp_bh->mddev->private;
80
81         bio->bi_status = status;
82         bio_endio(bio);
83         mempool_free(mp_bh, conf->pool);
84 }
85
86 static void multipath_end_request(struct bio *bio)
87 {
88         struct multipath_bh *mp_bh = bio->bi_private;
89         struct mpconf *conf = mp_bh->mddev->private;
90         struct md_rdev *rdev = conf->multipaths[mp_bh->path].rdev;
91
92         if (!bio->bi_status)
93                 multipath_end_bh_io(mp_bh, 0);
94         else if (!(bio->bi_opf & REQ_RAHEAD)) {
95                 /*
96                  * oops, IO error:
97                  */
98                 char b[BDEVNAME_SIZE];
99                 md_error (mp_bh->mddev, rdev);
100                 pr_info("multipath: %s: rescheduling sector %llu\n",
101                         bdevname(rdev->bdev,b),
102                         (unsigned long long)bio->bi_iter.bi_sector);
103                 multipath_reschedule_retry(mp_bh);
104         } else
105                 multipath_end_bh_io(mp_bh, bio->bi_status);
106         rdev_dec_pending(rdev, conf->mddev);
107 }
108
109 static bool multipath_make_request(struct mddev *mddev, struct bio * bio)
110 {
111         struct mpconf *conf = mddev->private;
112         struct multipath_bh * mp_bh;
113         struct multipath_info *multipath;
114
115         if (unlikely(bio->bi_opf & REQ_PREFLUSH)) {
116                 md_flush_request(mddev, bio);
117                 return true;
118         }
119
120         mp_bh = mempool_alloc(conf->pool, GFP_NOIO);
121
122         mp_bh->master_bio = bio;
123         mp_bh->mddev = mddev;
124
125         mp_bh->path = multipath_map(conf);
126         if (mp_bh->path < 0) {
127                 bio_io_error(bio);
128                 mempool_free(mp_bh, conf->pool);
129                 return true;
130         }
131         multipath = conf->multipaths + mp_bh->path;
132
133         bio_init(&mp_bh->bio, NULL, 0);
134         __bio_clone_fast(&mp_bh->bio, bio);
135
136         mp_bh->bio.bi_iter.bi_sector += multipath->rdev->data_offset;
137         bio_set_dev(&mp_bh->bio, multipath->rdev->bdev);
138         mp_bh->bio.bi_opf |= REQ_FAILFAST_TRANSPORT;
139         mp_bh->bio.bi_end_io = multipath_end_request;
140         mp_bh->bio.bi_private = mp_bh;
141         mddev_check_writesame(mddev, &mp_bh->bio);
142         mddev_check_write_zeroes(mddev, &mp_bh->bio);
143         generic_make_request(&mp_bh->bio);
144         return true;
145 }
146
147 static void multipath_status(struct seq_file *seq, struct mddev *mddev)
148 {
149         struct mpconf *conf = mddev->private;
150         int i;
151
152         seq_printf (seq, " [%d/%d] [", conf->raid_disks,
153                     conf->raid_disks - mddev->degraded);
154         rcu_read_lock();
155         for (i = 0; i < conf->raid_disks; i++) {
156                 struct md_rdev *rdev = rcu_dereference(conf->multipaths[i].rdev);
157                 seq_printf (seq, "%s", rdev && test_bit(In_sync, &rdev->flags) ? "U" : "_");
158         }
159         rcu_read_unlock();
160         seq_putc(seq, ']');
161 }
162
163 static int multipath_congested(struct mddev *mddev, int bits)
164 {
165         struct mpconf *conf = mddev->private;
166         int i, ret = 0;
167
168         rcu_read_lock();
169         for (i = 0; i < mddev->raid_disks ; i++) {
170                 struct md_rdev *rdev = rcu_dereference(conf->multipaths[i].rdev);
171                 if (rdev && !test_bit(Faulty, &rdev->flags)) {
172                         struct request_queue *q = bdev_get_queue(rdev->bdev);
173
174                         ret |= bdi_congested(q->backing_dev_info, bits);
175                         /* Just like multipath_map, we just check the
176                          * first available device
177                          */
178                         break;
179                 }
180         }
181         rcu_read_unlock();
182         return ret;
183 }
184
185 /*
186  * Careful, this can execute in IRQ contexts as well!
187  */
188 static void multipath_error (struct mddev *mddev, struct md_rdev *rdev)
189 {
190         struct mpconf *conf = mddev->private;
191         char b[BDEVNAME_SIZE];
192
193         if (conf->raid_disks - mddev->degraded <= 1) {
194                 /*
195                  * Uh oh, we can do nothing if this is our last path, but
196                  * first check if this is a queued request for a device
197                  * which has just failed.
198                  */
199                 pr_warn("multipath: only one IO path left and IO error.\n");
200                 /* leave it active... it's all we have */
201                 return;
202         }
203         /*
204          * Mark disk as unusable
205          */
206         if (test_and_clear_bit(In_sync, &rdev->flags)) {
207                 unsigned long flags;
208                 spin_lock_irqsave(&conf->device_lock, flags);
209                 mddev->degraded++;
210                 spin_unlock_irqrestore(&conf->device_lock, flags);
211         }
212         set_bit(Faulty, &rdev->flags);
213         set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags);
214         pr_err("multipath: IO failure on %s, disabling IO path.\n"
215                "multipath: Operation continuing on %d IO paths.\n",
216                bdevname(rdev->bdev, b),
217                conf->raid_disks - mddev->degraded);
218 }
219
220 static void print_multipath_conf (struct mpconf *conf)
221 {
222         int i;
223         struct multipath_info *tmp;
224
225         pr_debug("MULTIPATH conf printout:\n");
226         if (!conf) {
227                 pr_debug("(conf==NULL)\n");
228                 return;
229         }
230         pr_debug(" --- wd:%d rd:%d\n", conf->raid_disks - conf->mddev->degraded,
231                  conf->raid_disks);
232
233         for (i = 0; i < conf->raid_disks; i++) {
234                 char b[BDEVNAME_SIZE];
235                 tmp = conf->multipaths + i;
236                 if (tmp->rdev)
237                         pr_debug(" disk%d, o:%d, dev:%s\n",
238                                  i,!test_bit(Faulty, &tmp->rdev->flags),
239                                  bdevname(tmp->rdev->bdev,b));
240         }
241 }
242
243 static int multipath_add_disk(struct mddev *mddev, struct md_rdev *rdev)
244 {
245         struct mpconf *conf = mddev->private;
246         int err = -EEXIST;
247         int path;
248         struct multipath_info *p;
249         int first = 0;
250         int last = mddev->raid_disks - 1;
251
252         if (rdev->raid_disk >= 0)
253                 first = last = rdev->raid_disk;
254
255         print_multipath_conf(conf);
256
257         for (path = first; path <= last; path++)
258                 if ((p=conf->multipaths+path)->rdev == NULL) {
259                         disk_stack_limits(mddev->gendisk, rdev->bdev,
260                                           rdev->data_offset << 9);
261
262                         err = md_integrity_add_rdev(rdev, mddev);
263                         if (err)
264                                 break;
265                         spin_lock_irq(&conf->device_lock);
266                         mddev->degraded--;
267                         rdev->raid_disk = path;
268                         set_bit(In_sync, &rdev->flags);
269                         spin_unlock_irq(&conf->device_lock);
270                         rcu_assign_pointer(p->rdev, rdev);
271                         err = 0;
272                         break;
273                 }
274
275         print_multipath_conf(conf);
276
277         return err;
278 }
279
280 static int multipath_remove_disk(struct mddev *mddev, struct md_rdev *rdev)
281 {
282         struct mpconf *conf = mddev->private;
283         int err = 0;
284         int number = rdev->raid_disk;
285         struct multipath_info *p = conf->multipaths + number;
286
287         print_multipath_conf(conf);
288
289         if (rdev == p->rdev) {
290                 if (test_bit(In_sync, &rdev->flags) ||
291                     atomic_read(&rdev->nr_pending)) {
292                         pr_warn("hot-remove-disk, slot %d is identified but is still operational!\n", number);
293                         err = -EBUSY;
294                         goto abort;
295                 }
296                 p->rdev = NULL;
297                 if (!test_bit(RemoveSynchronized, &rdev->flags)) {
298                         synchronize_rcu();
299                         if (atomic_read(&rdev->nr_pending)) {
300                                 /* lost the race, try later */
301                                 err = -EBUSY;
302                                 p->rdev = rdev;
303                                 goto abort;
304                         }
305                 }
306                 err = md_integrity_register(mddev);
307         }
308 abort:
309
310         print_multipath_conf(conf);
311         return err;
312 }
313
314 /*
315  * This is a kernel thread which:
316  *
317  *      1.      Retries failed read operations on working multipaths.
318  *      2.      Updates the raid superblock when problems encounter.
319  *      3.      Performs writes following reads for array syncronising.
320  */
321
322 static void multipathd(struct md_thread *thread)
323 {
324         struct mddev *mddev = thread->mddev;
325         struct multipath_bh *mp_bh;
326         struct bio *bio;
327         unsigned long flags;
328         struct mpconf *conf = mddev->private;
329         struct list_head *head = &conf->retry_list;
330
331         md_check_recovery(mddev);
332         for (;;) {
333                 char b[BDEVNAME_SIZE];
334                 spin_lock_irqsave(&conf->device_lock, flags);
335                 if (list_empty(head))
336                         break;
337                 mp_bh = list_entry(head->prev, struct multipath_bh, retry_list);
338                 list_del(head->prev);
339                 spin_unlock_irqrestore(&conf->device_lock, flags);
340
341                 bio = &mp_bh->bio;
342                 bio->bi_iter.bi_sector = mp_bh->master_bio->bi_iter.bi_sector;
343
344                 if ((mp_bh->path = multipath_map (conf))<0) {
345                         pr_err("multipath: %s: unrecoverable IO read error for block %llu\n",
346                                bio_devname(bio, b),
347                                (unsigned long long)bio->bi_iter.bi_sector);
348                         multipath_end_bh_io(mp_bh, BLK_STS_IOERR);
349                 } else {
350                         pr_err("multipath: %s: redirecting sector %llu to another IO path\n",
351                                bio_devname(bio, b),
352                                (unsigned long long)bio->bi_iter.bi_sector);
353                         *bio = *(mp_bh->master_bio);
354                         bio->bi_iter.bi_sector +=
355                                 conf->multipaths[mp_bh->path].rdev->data_offset;
356                         bio_set_dev(bio, conf->multipaths[mp_bh->path].rdev->bdev);
357                         bio->bi_opf |= REQ_FAILFAST_TRANSPORT;
358                         bio->bi_end_io = multipath_end_request;
359                         bio->bi_private = mp_bh;
360                         generic_make_request(bio);
361                 }
362         }
363         spin_unlock_irqrestore(&conf->device_lock, flags);
364 }
365
366 static sector_t multipath_size(struct mddev *mddev, sector_t sectors, int raid_disks)
367 {
368         WARN_ONCE(sectors || raid_disks,
369                   "%s does not support generic reshape\n", __func__);
370
371         return mddev->dev_sectors;
372 }
373
374 static int multipath_run (struct mddev *mddev)
375 {
376         struct mpconf *conf;
377         int disk_idx;
378         struct multipath_info *disk;
379         struct md_rdev *rdev;
380         int working_disks;
381
382         if (md_check_no_bitmap(mddev))
383                 return -EINVAL;
384
385         if (mddev->level != LEVEL_MULTIPATH) {
386                 pr_warn("multipath: %s: raid level not set to multipath IO (%d)\n",
387                         mdname(mddev), mddev->level);
388                 goto out;
389         }
390         /*
391          * copy the already verified devices into our private MULTIPATH
392          * bookkeeping area. [whatever we allocate in multipath_run(),
393          * should be freed in multipath_free()]
394          */
395
396         conf = kzalloc(sizeof(struct mpconf), GFP_KERNEL);
397         mddev->private = conf;
398         if (!conf)
399                 goto out;
400
401         conf->multipaths = kzalloc(sizeof(struct multipath_info)*mddev->raid_disks,
402                                    GFP_KERNEL);
403         if (!conf->multipaths)
404                 goto out_free_conf;
405
406         working_disks = 0;
407         rdev_for_each(rdev, mddev) {
408                 disk_idx = rdev->raid_disk;
409                 if (disk_idx < 0 ||
410                     disk_idx >= mddev->raid_disks)
411                         continue;
412
413                 disk = conf->multipaths + disk_idx;
414                 disk->rdev = rdev;
415                 disk_stack_limits(mddev->gendisk, rdev->bdev,
416                                   rdev->data_offset << 9);
417
418                 if (!test_bit(Faulty, &rdev->flags))
419                         working_disks++;
420         }
421
422         conf->raid_disks = mddev->raid_disks;
423         conf->mddev = mddev;
424         spin_lock_init(&conf->device_lock);
425         INIT_LIST_HEAD(&conf->retry_list);
426
427         if (!working_disks) {
428                 pr_warn("multipath: no operational IO paths for %s\n",
429                         mdname(mddev));
430                 goto out_free_conf;
431         }
432         mddev->degraded = conf->raid_disks - working_disks;
433
434         conf->pool = mempool_create_kmalloc_pool(NR_RESERVED_BUFS,
435                                                  sizeof(struct multipath_bh));
436         if (conf->pool == NULL)
437                 goto out_free_conf;
438
439         mddev->thread = md_register_thread(multipathd, mddev,
440                                            "multipath");
441         if (!mddev->thread)
442                 goto out_free_conf;
443
444         pr_info("multipath: array %s active with %d out of %d IO paths\n",
445                 mdname(mddev), conf->raid_disks - mddev->degraded,
446                 mddev->raid_disks);
447         /*
448          * Ok, everything is just fine now
449          */
450         md_set_array_sectors(mddev, multipath_size(mddev, 0, 0));
451
452         if (md_integrity_register(mddev))
453                 goto out_free_conf;
454
455         return 0;
456
457 out_free_conf:
458         mempool_destroy(conf->pool);
459         kfree(conf->multipaths);
460         kfree(conf);
461         mddev->private = NULL;
462 out:
463         return -EIO;
464 }
465
466 static void multipath_free(struct mddev *mddev, void *priv)
467 {
468         struct mpconf *conf = priv;
469
470         mempool_destroy(conf->pool);
471         kfree(conf->multipaths);
472         kfree(conf);
473 }
474
475 static struct md_personality multipath_personality =
476 {
477         .name           = "multipath",
478         .level          = LEVEL_MULTIPATH,
479         .owner          = THIS_MODULE,
480         .make_request   = multipath_make_request,
481         .run            = multipath_run,
482         .free           = multipath_free,
483         .status         = multipath_status,
484         .error_handler  = multipath_error,
485         .hot_add_disk   = multipath_add_disk,
486         .hot_remove_disk= multipath_remove_disk,
487         .size           = multipath_size,
488         .congested      = multipath_congested,
489 };
490
491 static int __init multipath_init (void)
492 {
493         return register_md_personality (&multipath_personality);
494 }
495
496 static void __exit multipath_exit (void)
497 {
498         unregister_md_personality (&multipath_personality);
499 }
500
501 module_init(multipath_init);
502 module_exit(multipath_exit);
503 MODULE_LICENSE("GPL");
504 MODULE_DESCRIPTION("simple multi-path personality for MD");
505 MODULE_ALIAS("md-personality-7"); /* MULTIPATH */
506 MODULE_ALIAS("md-multipath");
507 MODULE_ALIAS("md-level--4");