Root/drivers/md/dm-raid1.c

1/*
2 * Copyright (C) 2003 Sistina Software Limited.
3 * Copyright (C) 2005-2008 Red Hat, Inc. All rights reserved.
4 *
5 * This file is released under the GPL.
6 */
7
8#include "dm-bio-record.h"
9
10#include <linux/init.h>
11#include <linux/mempool.h>
12#include <linux/module.h>
13#include <linux/pagemap.h>
14#include <linux/slab.h>
15#include <linux/workqueue.h>
16#include <linux/device-mapper.h>
17#include <linux/dm-io.h>
18#include <linux/dm-dirty-log.h>
19#include <linux/dm-kcopyd.h>
20#include <linux/dm-region-hash.h>
21
22#define DM_MSG_PREFIX "raid1"
23
24#define MAX_RECOVERY 1 /* Maximum number of regions recovered in parallel. */
25
26#define DM_RAID1_HANDLE_ERRORS 0x01
27#define errors_handled(p) ((p)->features & DM_RAID1_HANDLE_ERRORS)
28
29static DECLARE_WAIT_QUEUE_HEAD(_kmirrord_recovery_stopped);
30
31/*-----------------------------------------------------------------
32 * Mirror set structures.
33 *---------------------------------------------------------------*/
34enum dm_raid1_error {
35    DM_RAID1_WRITE_ERROR,
36    DM_RAID1_FLUSH_ERROR,
37    DM_RAID1_SYNC_ERROR,
38    DM_RAID1_READ_ERROR
39};
40
41struct mirror {
42    struct mirror_set *ms;
43    atomic_t error_count;
44    unsigned long error_type;
45    struct dm_dev *dev;
46    sector_t offset;
47};
48
49struct mirror_set {
50    struct dm_target *ti;
51    struct list_head list;
52
53    uint64_t features;
54
55    spinlock_t lock; /* protects the lists */
56    struct bio_list reads;
57    struct bio_list writes;
58    struct bio_list failures;
59    struct bio_list holds; /* bios are waiting until suspend */
60
61    struct dm_region_hash *rh;
62    struct dm_kcopyd_client *kcopyd_client;
63    struct dm_io_client *io_client;
64
65    /* recovery */
66    region_t nr_regions;
67    int in_sync;
68    int log_failure;
69    int leg_failure;
70    atomic_t suspend;
71
72    atomic_t default_mirror; /* Default mirror */
73
74    struct workqueue_struct *kmirrord_wq;
75    struct work_struct kmirrord_work;
76    struct timer_list timer;
77    unsigned long timer_pending;
78
79    struct work_struct trigger_event;
80
81    unsigned nr_mirrors;
82    struct mirror mirror[0];
83};
84
85DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(raid1_resync_throttle,
86        "A percentage of time allocated for raid resynchronization");
87
88static void wakeup_mirrord(void *context)
89{
90    struct mirror_set *ms = context;
91
92    queue_work(ms->kmirrord_wq, &ms->kmirrord_work);
93}
94
95static void delayed_wake_fn(unsigned long data)
96{
97    struct mirror_set *ms = (struct mirror_set *) data;
98
99    clear_bit(0, &ms->timer_pending);
100    wakeup_mirrord(ms);
101}
102
103static void delayed_wake(struct mirror_set *ms)
104{
105    if (test_and_set_bit(0, &ms->timer_pending))
106        return;
107
108    ms->timer.expires = jiffies + HZ / 5;
109    ms->timer.data = (unsigned long) ms;
110    ms->timer.function = delayed_wake_fn;
111    add_timer(&ms->timer);
112}
113
114static void wakeup_all_recovery_waiters(void *context)
115{
116    wake_up_all(&_kmirrord_recovery_stopped);
117}
118
119static void queue_bio(struct mirror_set *ms, struct bio *bio, int rw)
120{
121    unsigned long flags;
122    int should_wake = 0;
123    struct bio_list *bl;
124
125    bl = (rw == WRITE) ? &ms->writes : &ms->reads;
126    spin_lock_irqsave(&ms->lock, flags);
127    should_wake = !(bl->head);
128    bio_list_add(bl, bio);
129    spin_unlock_irqrestore(&ms->lock, flags);
130
131    if (should_wake)
132        wakeup_mirrord(ms);
133}
134
135static void dispatch_bios(void *context, struct bio_list *bio_list)
136{
137    struct mirror_set *ms = context;
138    struct bio *bio;
139
140    while ((bio = bio_list_pop(bio_list)))
141        queue_bio(ms, bio, WRITE);
142}
143
144struct dm_raid1_bio_record {
145    struct mirror *m;
146    /* if details->bi_bdev == NULL, details were not saved */
147    struct dm_bio_details details;
148    region_t write_region;
149};
150
151/*
152 * Every mirror should look like this one.
153 */
154#define DEFAULT_MIRROR 0
155
156/*
157 * This is yucky. We squirrel the mirror struct away inside
158 * bi_next for read/write buffers. This is safe since the bh
159 * doesn't get submitted to the lower levels of block layer.
160 */
161static struct mirror *bio_get_m(struct bio *bio)
162{
163    return (struct mirror *) bio->bi_next;
164}
165
166static void bio_set_m(struct bio *bio, struct mirror *m)
167{
168    bio->bi_next = (struct bio *) m;
169}
170
171static struct mirror *get_default_mirror(struct mirror_set *ms)
172{
173    return &ms->mirror[atomic_read(&ms->default_mirror)];
174}
175
176static void set_default_mirror(struct mirror *m)
177{
178    struct mirror_set *ms = m->ms;
179    struct mirror *m0 = &(ms->mirror[0]);
180
181    atomic_set(&ms->default_mirror, m - m0);
182}
183
184static struct mirror *get_valid_mirror(struct mirror_set *ms)
185{
186    struct mirror *m;
187
188    for (m = ms->mirror; m < ms->mirror + ms->nr_mirrors; m++)
189        if (!atomic_read(&m->error_count))
190            return m;
191
192    return NULL;
193}
194
195/* fail_mirror
196 * @m: mirror device to fail
197 * @error_type: one of the enum's, DM_RAID1_*_ERROR
198 *
199 * If errors are being handled, record the type of
200 * error encountered for this device. If this type
201 * of error has already been recorded, we can return;
202 * otherwise, we must signal userspace by triggering
203 * an event. Additionally, if the device is the
204 * primary device, we must choose a new primary, but
205 * only if the mirror is in-sync.
206 *
207 * This function must not block.
208 */
209static void fail_mirror(struct mirror *m, enum dm_raid1_error error_type)
210{
211    struct mirror_set *ms = m->ms;
212    struct mirror *new;
213
214    ms->leg_failure = 1;
215
216    /*
217     * error_count is used for nothing more than a
218     * simple way to tell if a device has encountered
219     * errors.
220     */
221    atomic_inc(&m->error_count);
222
223    if (test_and_set_bit(error_type, &m->error_type))
224        return;
225
226    if (!errors_handled(ms))
227        return;
228
229    if (m != get_default_mirror(ms))
230        goto out;
231
232    if (!ms->in_sync) {
233        /*
234         * Better to issue requests to same failing device
235         * than to risk returning corrupt data.
236         */
237        DMERR("Primary mirror (%s) failed while out-of-sync: "
238              "Reads may fail.", m->dev->name);
239        goto out;
240    }
241
242    new = get_valid_mirror(ms);
243    if (new)
244        set_default_mirror(new);
245    else
246        DMWARN("All sides of mirror have failed.");
247
248out:
249    schedule_work(&ms->trigger_event);
250}
251
252static int mirror_flush(struct dm_target *ti)
253{
254    struct mirror_set *ms = ti->private;
255    unsigned long error_bits;
256
257    unsigned int i;
258    struct dm_io_region io[ms->nr_mirrors];
259    struct mirror *m;
260    struct dm_io_request io_req = {
261        .bi_rw = WRITE_FLUSH,
262        .mem.type = DM_IO_KMEM,
263        .mem.ptr.addr = NULL,
264        .client = ms->io_client,
265    };
266
267    for (i = 0, m = ms->mirror; i < ms->nr_mirrors; i++, m++) {
268        io[i].bdev = m->dev->bdev;
269        io[i].sector = 0;
270        io[i].count = 0;
271    }
272
273    error_bits = -1;
274    dm_io(&io_req, ms->nr_mirrors, io, &error_bits);
275    if (unlikely(error_bits != 0)) {
276        for (i = 0; i < ms->nr_mirrors; i++)
277            if (test_bit(i, &error_bits))
278                fail_mirror(ms->mirror + i,
279                        DM_RAID1_FLUSH_ERROR);
280        return -EIO;
281    }
282
283    return 0;
284}
285
286/*-----------------------------------------------------------------
287 * Recovery.
288 *
289 * When a mirror is first activated we may find that some regions
290 * are in the no-sync state. We have to recover these by
291 * recopying from the default mirror to all the others.
292 *---------------------------------------------------------------*/
293static void recovery_complete(int read_err, unsigned long write_err,
294                  void *context)
295{
296    struct dm_region *reg = context;
297    struct mirror_set *ms = dm_rh_region_context(reg);
298    int m, bit = 0;
299
300    if (read_err) {
301        /* Read error means the failure of default mirror. */
302        DMERR_LIMIT("Unable to read primary mirror during recovery");
303        fail_mirror(get_default_mirror(ms), DM_RAID1_SYNC_ERROR);
304    }
305
306    if (write_err) {
307        DMERR_LIMIT("Write error during recovery (error = 0x%lx)",
308                write_err);
309        /*
310         * Bits correspond to devices (excluding default mirror).
311         * The default mirror cannot change during recovery.
312         */
313        for (m = 0; m < ms->nr_mirrors; m++) {
314            if (&ms->mirror[m] == get_default_mirror(ms))
315                continue;
316            if (test_bit(bit, &write_err))
317                fail_mirror(ms->mirror + m,
318                        DM_RAID1_SYNC_ERROR);
319            bit++;
320        }
321    }
322
323    dm_rh_recovery_end(reg, !(read_err || write_err));
324}
325
326static int recover(struct mirror_set *ms, struct dm_region *reg)
327{
328    int r;
329    unsigned i;
330    struct dm_io_region from, to[DM_KCOPYD_MAX_REGIONS], *dest;
331    struct mirror *m;
332    unsigned long flags = 0;
333    region_t key = dm_rh_get_region_key(reg);
334    sector_t region_size = dm_rh_get_region_size(ms->rh);
335
336    /* fill in the source */
337    m = get_default_mirror(ms);
338    from.bdev = m->dev->bdev;
339    from.sector = m->offset + dm_rh_region_to_sector(ms->rh, key);
340    if (key == (ms->nr_regions - 1)) {
341        /*
342         * The final region may be smaller than
343         * region_size.
344         */
345        from.count = ms->ti->len & (region_size - 1);
346        if (!from.count)
347            from.count = region_size;
348    } else
349        from.count = region_size;
350
351    /* fill in the destinations */
352    for (i = 0, dest = to; i < ms->nr_mirrors; i++) {
353        if (&ms->mirror[i] == get_default_mirror(ms))
354            continue;
355
356        m = ms->mirror + i;
357        dest->bdev = m->dev->bdev;
358        dest->sector = m->offset + dm_rh_region_to_sector(ms->rh, key);
359        dest->count = from.count;
360        dest++;
361    }
362
363    /* hand to kcopyd */
364    if (!errors_handled(ms))
365        set_bit(DM_KCOPYD_IGNORE_ERROR, &flags);
366
367    r = dm_kcopyd_copy(ms->kcopyd_client, &from, ms->nr_mirrors - 1, to,
368               flags, recovery_complete, reg);
369
370    return r;
371}
372
373static void do_recovery(struct mirror_set *ms)
374{
375    struct dm_region *reg;
376    struct dm_dirty_log *log = dm_rh_dirty_log(ms->rh);
377    int r;
378
379    /*
380     * Start quiescing some regions.
381     */
382    dm_rh_recovery_prepare(ms->rh);
383
384    /*
385     * Copy any already quiesced regions.
386     */
387    while ((reg = dm_rh_recovery_start(ms->rh))) {
388        r = recover(ms, reg);
389        if (r)
390            dm_rh_recovery_end(reg, 0);
391    }
392
393    /*
394     * Update the in sync flag.
395     */
396    if (!ms->in_sync &&
397        (log->type->get_sync_count(log) == ms->nr_regions)) {
398        /* the sync is complete */
399        dm_table_event(ms->ti->table);
400        ms->in_sync = 1;
401    }
402}
403
404/*-----------------------------------------------------------------
405 * Reads
406 *---------------------------------------------------------------*/
407static struct mirror *choose_mirror(struct mirror_set *ms, sector_t sector)
408{
409    struct mirror *m = get_default_mirror(ms);
410
411    do {
412        if (likely(!atomic_read(&m->error_count)))
413            return m;
414
415        if (m-- == ms->mirror)
416            m += ms->nr_mirrors;
417    } while (m != get_default_mirror(ms));
418
419    return NULL;
420}
421
422static int default_ok(struct mirror *m)
423{
424    struct mirror *default_mirror = get_default_mirror(m->ms);
425
426    return !atomic_read(&default_mirror->error_count);
427}
428
429static int mirror_available(struct mirror_set *ms, struct bio *bio)
430{
431    struct dm_dirty_log *log = dm_rh_dirty_log(ms->rh);
432    region_t region = dm_rh_bio_to_region(ms->rh, bio);
433
434    if (log->type->in_sync(log, region, 0))
435        return choose_mirror(ms, bio->bi_sector) ? 1 : 0;
436
437    return 0;
438}
439
440/*
441 * remap a buffer to a particular mirror.
442 */
443static sector_t map_sector(struct mirror *m, struct bio *bio)
444{
445    if (unlikely(!bio->bi_size))
446        return 0;
447    return m->offset + dm_target_offset(m->ms->ti, bio->bi_sector);
448}
449
450static void map_bio(struct mirror *m, struct bio *bio)
451{
452    bio->bi_bdev = m->dev->bdev;
453    bio->bi_sector = map_sector(m, bio);
454}
455
456static void map_region(struct dm_io_region *io, struct mirror *m,
457               struct bio *bio)
458{
459    io->bdev = m->dev->bdev;
460    io->sector = map_sector(m, bio);
461    io->count = bio->bi_size >> 9;
462}
463
464static void hold_bio(struct mirror_set *ms, struct bio *bio)
465{
466    /*
467     * Lock is required to avoid race condition during suspend
468     * process.
469     */
470    spin_lock_irq(&ms->lock);
471
472    if (atomic_read(&ms->suspend)) {
473        spin_unlock_irq(&ms->lock);
474
475        /*
476         * If device is suspended, complete the bio.
477         */
478        if (dm_noflush_suspending(ms->ti))
479            bio_endio(bio, DM_ENDIO_REQUEUE);
480        else
481            bio_endio(bio, -EIO);
482        return;
483    }
484
485    /*
486     * Hold bio until the suspend is complete.
487     */
488    bio_list_add(&ms->holds, bio);
489    spin_unlock_irq(&ms->lock);
490}
491
492/*-----------------------------------------------------------------
493 * Reads
494 *---------------------------------------------------------------*/
495static void read_callback(unsigned long error, void *context)
496{
497    struct bio *bio = context;
498    struct mirror *m;
499
500    m = bio_get_m(bio);
501    bio_set_m(bio, NULL);
502
503    if (likely(!error)) {
504        bio_endio(bio, 0);
505        return;
506    }
507
508    fail_mirror(m, DM_RAID1_READ_ERROR);
509
510    if (likely(default_ok(m)) || mirror_available(m->ms, bio)) {
511        DMWARN_LIMIT("Read failure on mirror device %s. "
512                 "Trying alternative device.",
513                 m->dev->name);
514        queue_bio(m->ms, bio, bio_rw(bio));
515        return;
516    }
517
518    DMERR_LIMIT("Read failure on mirror device %s. Failing I/O.",
519            m->dev->name);
520    bio_endio(bio, -EIO);
521}
522
523/* Asynchronous read. */
524static void read_async_bio(struct mirror *m, struct bio *bio)
525{
526    struct dm_io_region io;
527    struct dm_io_request io_req = {
528        .bi_rw = READ,
529        .mem.type = DM_IO_BVEC,
530        .mem.ptr.bvec = bio->bi_io_vec + bio->bi_idx,
531        .notify.fn = read_callback,
532        .notify.context = bio,
533        .client = m->ms->io_client,
534    };
535
536    map_region(&io, m, bio);
537    bio_set_m(bio, m);
538    BUG_ON(dm_io(&io_req, 1, &io, NULL));
539}
540
541static inline int region_in_sync(struct mirror_set *ms, region_t region,
542                 int may_block)
543{
544    int state = dm_rh_get_state(ms->rh, region, may_block);
545    return state == DM_RH_CLEAN || state == DM_RH_DIRTY;
546}
547
548static void do_reads(struct mirror_set *ms, struct bio_list *reads)
549{
550    region_t region;
551    struct bio *bio;
552    struct mirror *m;
553
554    while ((bio = bio_list_pop(reads))) {
555        region = dm_rh_bio_to_region(ms->rh, bio);
556        m = get_default_mirror(ms);
557
558        /*
559         * We can only read balance if the region is in sync.
560         */
561        if (likely(region_in_sync(ms, region, 1)))
562            m = choose_mirror(ms, bio->bi_sector);
563        else if (m && atomic_read(&m->error_count))
564            m = NULL;
565
566        if (likely(m))
567            read_async_bio(m, bio);
568        else
569            bio_endio(bio, -EIO);
570    }
571}
572
573/*-----------------------------------------------------------------
574 * Writes.
575 *
576 * We do different things with the write io depending on the
577 * state of the region that it's in:
578 *
579 * SYNC: increment pending, use kcopyd to write to *all* mirrors
580 * RECOVERING: delay the io until recovery completes
581 * NOSYNC: increment pending, just write to the default mirror
582 *---------------------------------------------------------------*/
583
584
585static void write_callback(unsigned long error, void *context)
586{
587    unsigned i, ret = 0;
588    struct bio *bio = (struct bio *) context;
589    struct mirror_set *ms;
590    int should_wake = 0;
591    unsigned long flags;
592
593    ms = bio_get_m(bio)->ms;
594    bio_set_m(bio, NULL);
595
596    /*
597     * NOTE: We don't decrement the pending count here,
598     * instead it is done by the targets endio function.
599     * This way we handle both writes to SYNC and NOSYNC
600     * regions with the same code.
601     */
602    if (likely(!error)) {
603        bio_endio(bio, ret);
604        return;
605    }
606
607    for (i = 0; i < ms->nr_mirrors; i++)
608        if (test_bit(i, &error))
609            fail_mirror(ms->mirror + i, DM_RAID1_WRITE_ERROR);
610
611    /*
612     * Need to raise event. Since raising
613     * events can block, we need to do it in
614     * the main thread.
615     */
616    spin_lock_irqsave(&ms->lock, flags);
617    if (!ms->failures.head)
618        should_wake = 1;
619    bio_list_add(&ms->failures, bio);
620    spin_unlock_irqrestore(&ms->lock, flags);
621    if (should_wake)
622        wakeup_mirrord(ms);
623}
624
625static void do_write(struct mirror_set *ms, struct bio *bio)
626{
627    unsigned int i;
628    struct dm_io_region io[ms->nr_mirrors], *dest = io;
629    struct mirror *m;
630    struct dm_io_request io_req = {
631        .bi_rw = WRITE | (bio->bi_rw & WRITE_FLUSH_FUA),
632        .mem.type = DM_IO_BVEC,
633        .mem.ptr.bvec = bio->bi_io_vec + bio->bi_idx,
634        .notify.fn = write_callback,
635        .notify.context = bio,
636        .client = ms->io_client,
637    };
638
639    if (bio->bi_rw & REQ_DISCARD) {
640        io_req.bi_rw |= REQ_DISCARD;
641        io_req.mem.type = DM_IO_KMEM;
642        io_req.mem.ptr.addr = NULL;
643    }
644
645    for (i = 0, m = ms->mirror; i < ms->nr_mirrors; i++, m++)
646        map_region(dest++, m, bio);
647
648    /*
649     * Use default mirror because we only need it to retrieve the reference
650     * to the mirror set in write_callback().
651     */
652    bio_set_m(bio, get_default_mirror(ms));
653
654    BUG_ON(dm_io(&io_req, ms->nr_mirrors, io, NULL));
655}
656
657static void do_writes(struct mirror_set *ms, struct bio_list *writes)
658{
659    int state;
660    struct bio *bio;
661    struct bio_list sync, nosync, recover, *this_list = NULL;
662    struct bio_list requeue;
663    struct dm_dirty_log *log = dm_rh_dirty_log(ms->rh);
664    region_t region;
665
666    if (!writes->head)
667        return;
668
669    /*
670     * Classify each write.
671     */
672    bio_list_init(&sync);
673    bio_list_init(&nosync);
674    bio_list_init(&recover);
675    bio_list_init(&requeue);
676
677    while ((bio = bio_list_pop(writes))) {
678        if ((bio->bi_rw & REQ_FLUSH) ||
679            (bio->bi_rw & REQ_DISCARD)) {
680            bio_list_add(&sync, bio);
681            continue;
682        }
683
684        region = dm_rh_bio_to_region(ms->rh, bio);
685
686        if (log->type->is_remote_recovering &&
687            log->type->is_remote_recovering(log, region)) {
688            bio_list_add(&requeue, bio);
689            continue;
690        }
691
692        state = dm_rh_get_state(ms->rh, region, 1);
693        switch (state) {
694        case DM_RH_CLEAN:
695        case DM_RH_DIRTY:
696            this_list = &sync;
697            break;
698
699        case DM_RH_NOSYNC:
700            this_list = &nosync;
701            break;
702
703        case DM_RH_RECOVERING:
704            this_list = &recover;
705            break;
706        }
707
708        bio_list_add(this_list, bio);
709    }
710
711    /*
712     * Add bios that are delayed due to remote recovery
713     * back on to the write queue
714     */
715    if (unlikely(requeue.head)) {
716        spin_lock_irq(&ms->lock);
717        bio_list_merge(&ms->writes, &requeue);
718        spin_unlock_irq(&ms->lock);
719        delayed_wake(ms);
720    }
721
722    /*
723     * Increment the pending counts for any regions that will
724     * be written to (writes to recover regions are going to
725     * be delayed).
726     */
727    dm_rh_inc_pending(ms->rh, &sync);
728    dm_rh_inc_pending(ms->rh, &nosync);
729
730    /*
731     * If the flush fails on a previous call and succeeds here,
732     * we must not reset the log_failure variable. We need
733     * userspace interaction to do that.
734     */
735    ms->log_failure = dm_rh_flush(ms->rh) ? 1 : ms->log_failure;
736
737    /*
738     * Dispatch io.
739     */
740    if (unlikely(ms->log_failure) && errors_handled(ms)) {
741        spin_lock_irq(&ms->lock);
742        bio_list_merge(&ms->failures, &sync);
743        spin_unlock_irq(&ms->lock);
744        wakeup_mirrord(ms);
745    } else
746        while ((bio = bio_list_pop(&sync)))
747            do_write(ms, bio);
748
749    while ((bio = bio_list_pop(&recover)))
750        dm_rh_delay(ms->rh, bio);
751
752    while ((bio = bio_list_pop(&nosync))) {
753        if (unlikely(ms->leg_failure) && errors_handled(ms)) {
754            spin_lock_irq(&ms->lock);
755            bio_list_add(&ms->failures, bio);
756            spin_unlock_irq(&ms->lock);
757            wakeup_mirrord(ms);
758        } else {
759            map_bio(get_default_mirror(ms), bio);
760            generic_make_request(bio);
761        }
762    }
763}
764
765static void do_failures(struct mirror_set *ms, struct bio_list *failures)
766{
767    struct bio *bio;
768
769    if (likely(!failures->head))
770        return;
771
772    /*
773     * If the log has failed, unattempted writes are being
774     * put on the holds list. We can't issue those writes
775     * until a log has been marked, so we must store them.
776     *
777     * If a 'noflush' suspend is in progress, we can requeue
778     * the I/O's to the core. This give userspace a chance
779     * to reconfigure the mirror, at which point the core
780     * will reissue the writes. If the 'noflush' flag is
781     * not set, we have no choice but to return errors.
782     *
783     * Some writes on the failures list may have been
784     * submitted before the log failure and represent a
785     * failure to write to one of the devices. It is ok
786     * for us to treat them the same and requeue them
787     * as well.
788     */
789    while ((bio = bio_list_pop(failures))) {
790        if (!ms->log_failure) {
791            ms->in_sync = 0;
792            dm_rh_mark_nosync(ms->rh, bio);
793        }
794
795        /*
796         * If all the legs are dead, fail the I/O.
797         * If we have been told to handle errors, hold the bio
798         * and wait for userspace to deal with the problem.
799         * Otherwise pretend that the I/O succeeded. (This would
800         * be wrong if the failed leg returned after reboot and
801         * got replicated back to the good legs.)
802         */
803        if (!get_valid_mirror(ms))
804            bio_endio(bio, -EIO);
805        else if (errors_handled(ms))
806            hold_bio(ms, bio);
807        else
808            bio_endio(bio, 0);
809    }
810}
811
812static void trigger_event(struct work_struct *work)
813{
814    struct mirror_set *ms =
815        container_of(work, struct mirror_set, trigger_event);
816
817    dm_table_event(ms->ti->table);
818}
819
820/*-----------------------------------------------------------------
821 * kmirrord
822 *---------------------------------------------------------------*/
823static void do_mirror(struct work_struct *work)
824{
825    struct mirror_set *ms = container_of(work, struct mirror_set,
826                         kmirrord_work);
827    struct bio_list reads, writes, failures;
828    unsigned long flags;
829
830    spin_lock_irqsave(&ms->lock, flags);
831    reads = ms->reads;
832    writes = ms->writes;
833    failures = ms->failures;
834    bio_list_init(&ms->reads);
835    bio_list_init(&ms->writes);
836    bio_list_init(&ms->failures);
837    spin_unlock_irqrestore(&ms->lock, flags);
838
839    dm_rh_update_states(ms->rh, errors_handled(ms));
840    do_recovery(ms);
841    do_reads(ms, &reads);
842    do_writes(ms, &writes);
843    do_failures(ms, &failures);
844}
845
846/*-----------------------------------------------------------------
847 * Target functions
848 *---------------------------------------------------------------*/
849static struct mirror_set *alloc_context(unsigned int nr_mirrors,
850                    uint32_t region_size,
851                    struct dm_target *ti,
852                    struct dm_dirty_log *dl)
853{
854    size_t len;
855    struct mirror_set *ms = NULL;
856
857    len = sizeof(*ms) + (sizeof(ms->mirror[0]) * nr_mirrors);
858
859    ms = kzalloc(len, GFP_KERNEL);
860    if (!ms) {
861        ti->error = "Cannot allocate mirror context";
862        return NULL;
863    }
864
865    spin_lock_init(&ms->lock);
866    bio_list_init(&ms->reads);
867    bio_list_init(&ms->writes);
868    bio_list_init(&ms->failures);
869    bio_list_init(&ms->holds);
870
871    ms->ti = ti;
872    ms->nr_mirrors = nr_mirrors;
873    ms->nr_regions = dm_sector_div_up(ti->len, region_size);
874    ms->in_sync = 0;
875    ms->log_failure = 0;
876    ms->leg_failure = 0;
877    atomic_set(&ms->suspend, 0);
878    atomic_set(&ms->default_mirror, DEFAULT_MIRROR);
879
880    ms->io_client = dm_io_client_create();
881    if (IS_ERR(ms->io_client)) {
882        ti->error = "Error creating dm_io client";
883        kfree(ms);
884         return NULL;
885    }
886
887    ms->rh = dm_region_hash_create(ms, dispatch_bios, wakeup_mirrord,
888                       wakeup_all_recovery_waiters,
889                       ms->ti->begin, MAX_RECOVERY,
890                       dl, region_size, ms->nr_regions);
891    if (IS_ERR(ms->rh)) {
892        ti->error = "Error creating dirty region hash";
893        dm_io_client_destroy(ms->io_client);
894        kfree(ms);
895        return NULL;
896    }
897
898    return ms;
899}
900
901static void free_context(struct mirror_set *ms, struct dm_target *ti,
902             unsigned int m)
903{
904    while (m--)
905        dm_put_device(ti, ms->mirror[m].dev);
906
907    dm_io_client_destroy(ms->io_client);
908    dm_region_hash_destroy(ms->rh);
909    kfree(ms);
910}
911
912static int get_mirror(struct mirror_set *ms, struct dm_target *ti,
913              unsigned int mirror, char **argv)
914{
915    unsigned long long offset;
916    char dummy;
917
918    if (sscanf(argv[1], "%llu%c", &offset, &dummy) != 1) {
919        ti->error = "Invalid offset";
920        return -EINVAL;
921    }
922
923    if (dm_get_device(ti, argv[0], dm_table_get_mode(ti->table),
924              &ms->mirror[mirror].dev)) {
925        ti->error = "Device lookup failure";
926        return -ENXIO;
927    }
928
929    ms->mirror[mirror].ms = ms;
930    atomic_set(&(ms->mirror[mirror].error_count), 0);
931    ms->mirror[mirror].error_type = 0;
932    ms->mirror[mirror].offset = offset;
933
934    return 0;
935}
936
937/*
938 * Create dirty log: log_type #log_params <log_params>
939 */
940static struct dm_dirty_log *create_dirty_log(struct dm_target *ti,
941                         unsigned argc, char **argv,
942                         unsigned *args_used)
943{
944    unsigned param_count;
945    struct dm_dirty_log *dl;
946    char dummy;
947
948    if (argc < 2) {
949        ti->error = "Insufficient mirror log arguments";
950        return NULL;
951    }
952
953    if (sscanf(argv[1], "%u%c", &param_count, &dummy) != 1) {
954        ti->error = "Invalid mirror log argument count";
955        return NULL;
956    }
957
958    *args_used = 2 + param_count;
959
960    if (argc < *args_used) {
961        ti->error = "Insufficient mirror log arguments";
962        return NULL;
963    }
964
965    dl = dm_dirty_log_create(argv[0], ti, mirror_flush, param_count,
966                 argv + 2);
967    if (!dl) {
968        ti->error = "Error creating mirror dirty log";
969        return NULL;
970    }
971
972    return dl;
973}
974
975static int parse_features(struct mirror_set *ms, unsigned argc, char **argv,
976              unsigned *args_used)
977{
978    unsigned num_features;
979    struct dm_target *ti = ms->ti;
980    char dummy;
981
982    *args_used = 0;
983
984    if (!argc)
985        return 0;
986
987    if (sscanf(argv[0], "%u%c", &num_features, &dummy) != 1) {
988        ti->error = "Invalid number of features";
989        return -EINVAL;
990    }
991
992    argc--;
993    argv++;
994    (*args_used)++;
995
996    if (num_features > argc) {
997        ti->error = "Not enough arguments to support feature count";
998        return -EINVAL;
999    }
1000
1001    if (!strcmp("handle_errors", argv[0]))
1002        ms->features |= DM_RAID1_HANDLE_ERRORS;
1003    else {
1004        ti->error = "Unrecognised feature requested";
1005        return -EINVAL;
1006    }
1007
1008    (*args_used)++;
1009
1010    return 0;
1011}
1012
1013/*
1014 * Construct a mirror mapping:
1015 *
1016 * log_type #log_params <log_params>
1017 * #mirrors [mirror_path offset]{2,}
1018 * [#features <features>]
1019 *
1020 * log_type is "core" or "disk"
1021 * #log_params is between 1 and 3
1022 *
1023 * If present, features must be "handle_errors".
1024 */
1025static int mirror_ctr(struct dm_target *ti, unsigned int argc, char **argv)
1026{
1027    int r;
1028    unsigned int nr_mirrors, m, args_used;
1029    struct mirror_set *ms;
1030    struct dm_dirty_log *dl;
1031    char dummy;
1032
1033    dl = create_dirty_log(ti, argc, argv, &args_used);
1034    if (!dl)
1035        return -EINVAL;
1036
1037    argv += args_used;
1038    argc -= args_used;
1039
1040    if (!argc || sscanf(argv[0], "%u%c", &nr_mirrors, &dummy) != 1 ||
1041        nr_mirrors < 2 || nr_mirrors > DM_KCOPYD_MAX_REGIONS + 1) {
1042        ti->error = "Invalid number of mirrors";
1043        dm_dirty_log_destroy(dl);
1044        return -EINVAL;
1045    }
1046
1047    argv++, argc--;
1048
1049    if (argc < nr_mirrors * 2) {
1050        ti->error = "Too few mirror arguments";
1051        dm_dirty_log_destroy(dl);
1052        return -EINVAL;
1053    }
1054
1055    ms = alloc_context(nr_mirrors, dl->type->get_region_size(dl), ti, dl);
1056    if (!ms) {
1057        dm_dirty_log_destroy(dl);
1058        return -ENOMEM;
1059    }
1060
1061    /* Get the mirror parameter sets */
1062    for (m = 0; m < nr_mirrors; m++) {
1063        r = get_mirror(ms, ti, m, argv);
1064        if (r) {
1065            free_context(ms, ti, m);
1066            return r;
1067        }
1068        argv += 2;
1069        argc -= 2;
1070    }
1071
1072    ti->private = ms;
1073
1074    r = dm_set_target_max_io_len(ti, dm_rh_get_region_size(ms->rh));
1075    if (r)
1076        goto err_free_context;
1077
1078    ti->num_flush_bios = 1;
1079    ti->num_discard_bios = 1;
1080    ti->per_bio_data_size = sizeof(struct dm_raid1_bio_record);
1081    ti->discard_zeroes_data_unsupported = true;
1082
1083    ms->kmirrord_wq = alloc_workqueue("kmirrord",
1084                      WQ_NON_REENTRANT | WQ_MEM_RECLAIM, 0);
1085    if (!ms->kmirrord_wq) {
1086        DMERR("couldn't start kmirrord");
1087        r = -ENOMEM;
1088        goto err_free_context;
1089    }
1090    INIT_WORK(&ms->kmirrord_work, do_mirror);
1091    init_timer(&ms->timer);
1092    ms->timer_pending = 0;
1093    INIT_WORK(&ms->trigger_event, trigger_event);
1094
1095    r = parse_features(ms, argc, argv, &args_used);
1096    if (r)
1097        goto err_destroy_wq;
1098
1099    argv += args_used;
1100    argc -= args_used;
1101
1102    /*
1103     * Any read-balancing addition depends on the
1104     * DM_RAID1_HANDLE_ERRORS flag being present.
1105     * This is because the decision to balance depends
1106     * on the sync state of a region. If the above
1107     * flag is not present, we ignore errors; and
1108     * the sync state may be inaccurate.
1109     */
1110
1111    if (argc) {
1112        ti->error = "Too many mirror arguments";
1113        r = -EINVAL;
1114        goto err_destroy_wq;
1115    }
1116
1117    ms->kcopyd_client = dm_kcopyd_client_create(&dm_kcopyd_throttle);
1118    if (IS_ERR(ms->kcopyd_client)) {
1119        r = PTR_ERR(ms->kcopyd_client);
1120        goto err_destroy_wq;
1121    }
1122
1123    wakeup_mirrord(ms);
1124    return 0;
1125
1126err_destroy_wq:
1127    destroy_workqueue(ms->kmirrord_wq);
1128err_free_context:
1129    free_context(ms, ti, ms->nr_mirrors);
1130    return r;
1131}
1132
1133static void mirror_dtr(struct dm_target *ti)
1134{
1135    struct mirror_set *ms = (struct mirror_set *) ti->private;
1136
1137    del_timer_sync(&ms->timer);
1138    flush_workqueue(ms->kmirrord_wq);
1139    flush_work(&ms->trigger_event);
1140    dm_kcopyd_client_destroy(ms->kcopyd_client);
1141    destroy_workqueue(ms->kmirrord_wq);
1142    free_context(ms, ti, ms->nr_mirrors);
1143}
1144
1145/*
1146 * Mirror mapping function
1147 */
1148static int mirror_map(struct dm_target *ti, struct bio *bio)
1149{
1150    int r, rw = bio_rw(bio);
1151    struct mirror *m;
1152    struct mirror_set *ms = ti->private;
1153    struct dm_dirty_log *log = dm_rh_dirty_log(ms->rh);
1154    struct dm_raid1_bio_record *bio_record =
1155      dm_per_bio_data(bio, sizeof(struct dm_raid1_bio_record));
1156
1157    bio_record->details.bi_bdev = NULL;
1158
1159    if (rw == WRITE) {
1160        /* Save region for mirror_end_io() handler */
1161        bio_record->write_region = dm_rh_bio_to_region(ms->rh, bio);
1162        queue_bio(ms, bio, rw);
1163        return DM_MAPIO_SUBMITTED;
1164    }
1165
1166    r = log->type->in_sync(log, dm_rh_bio_to_region(ms->rh, bio), 0);
1167    if (r < 0 && r != -EWOULDBLOCK)
1168        return r;
1169
1170    /*
1171     * If region is not in-sync queue the bio.
1172     */
1173    if (!r || (r == -EWOULDBLOCK)) {
1174        if (rw == READA)
1175            return -EWOULDBLOCK;
1176
1177        queue_bio(ms, bio, rw);
1178        return DM_MAPIO_SUBMITTED;
1179    }
1180
1181    /*
1182     * The region is in-sync and we can perform reads directly.
1183     * Store enough information so we can retry if it fails.
1184     */
1185    m = choose_mirror(ms, bio->bi_sector);
1186    if (unlikely(!m))
1187        return -EIO;
1188
1189    dm_bio_record(&bio_record->details, bio);
1190    bio_record->m = m;
1191
1192    map_bio(m, bio);
1193
1194    return DM_MAPIO_REMAPPED;
1195}
1196
1197static int mirror_end_io(struct dm_target *ti, struct bio *bio, int error)
1198{
1199    int rw = bio_rw(bio);
1200    struct mirror_set *ms = (struct mirror_set *) ti->private;
1201    struct mirror *m = NULL;
1202    struct dm_bio_details *bd = NULL;
1203    struct dm_raid1_bio_record *bio_record =
1204      dm_per_bio_data(bio, sizeof(struct dm_raid1_bio_record));
1205
1206    /*
1207     * We need to dec pending if this was a write.
1208     */
1209    if (rw == WRITE) {
1210        if (!(bio->bi_rw & (REQ_FLUSH | REQ_DISCARD)))
1211            dm_rh_dec(ms->rh, bio_record->write_region);
1212        return error;
1213    }
1214
1215    if (error == -EOPNOTSUPP)
1216        goto out;
1217
1218    if ((error == -EWOULDBLOCK) && (bio->bi_rw & REQ_RAHEAD))
1219        goto out;
1220
1221    if (unlikely(error)) {
1222        if (!bio_record->details.bi_bdev) {
1223            /*
1224             * There wasn't enough memory to record necessary
1225             * information for a retry or there was no other
1226             * mirror in-sync.
1227             */
1228            DMERR_LIMIT("Mirror read failed.");
1229            return -EIO;
1230        }
1231
1232        m = bio_record->m;
1233
1234        DMERR("Mirror read failed from %s. Trying alternative device.",
1235              m->dev->name);
1236
1237        fail_mirror(m, DM_RAID1_READ_ERROR);
1238
1239        /*
1240         * A failed read is requeued for another attempt using an intact
1241         * mirror.
1242         */
1243        if (default_ok(m) || mirror_available(ms, bio)) {
1244            bd = &bio_record->details;
1245
1246            dm_bio_restore(bd, bio);
1247            bio_record->details.bi_bdev = NULL;
1248            queue_bio(ms, bio, rw);
1249            return DM_ENDIO_INCOMPLETE;
1250        }
1251        DMERR("All replicated volumes dead, failing I/O");
1252    }
1253
1254out:
1255    bio_record->details.bi_bdev = NULL;
1256
1257    return error;
1258}
1259
1260static void mirror_presuspend(struct dm_target *ti)
1261{
1262    struct mirror_set *ms = (struct mirror_set *) ti->private;
1263    struct dm_dirty_log *log = dm_rh_dirty_log(ms->rh);
1264
1265    struct bio_list holds;
1266    struct bio *bio;
1267
1268    atomic_set(&ms->suspend, 1);
1269
1270    /*
1271     * Process bios in the hold list to start recovery waiting
1272     * for bios in the hold list. After the process, no bio has
1273     * a chance to be added in the hold list because ms->suspend
1274     * is set.
1275     */
1276    spin_lock_irq(&ms->lock);
1277    holds = ms->holds;
1278    bio_list_init(&ms->holds);
1279    spin_unlock_irq(&ms->lock);
1280
1281    while ((bio = bio_list_pop(&holds)))
1282        hold_bio(ms, bio);
1283
1284    /*
1285     * We must finish up all the work that we've
1286     * generated (i.e. recovery work).
1287     */
1288    dm_rh_stop_recovery(ms->rh);
1289
1290    wait_event(_kmirrord_recovery_stopped,
1291           !dm_rh_recovery_in_flight(ms->rh));
1292
1293    if (log->type->presuspend && log->type->presuspend(log))
1294        /* FIXME: need better error handling */
1295        DMWARN("log presuspend failed");
1296
1297    /*
1298     * Now that recovery is complete/stopped and the
1299     * delayed bios are queued, we need to wait for
1300     * the worker thread to complete. This way,
1301     * we know that all of our I/O has been pushed.
1302     */
1303    flush_workqueue(ms->kmirrord_wq);
1304}
1305
1306static void mirror_postsuspend(struct dm_target *ti)
1307{
1308    struct mirror_set *ms = ti->private;
1309    struct dm_dirty_log *log = dm_rh_dirty_log(ms->rh);
1310
1311    if (log->type->postsuspend && log->type->postsuspend(log))
1312        /* FIXME: need better error handling */
1313        DMWARN("log postsuspend failed");
1314}
1315
1316static void mirror_resume(struct dm_target *ti)
1317{
1318    struct mirror_set *ms = ti->private;
1319    struct dm_dirty_log *log = dm_rh_dirty_log(ms->rh);
1320
1321    atomic_set(&ms->suspend, 0);
1322    if (log->type->resume && log->type->resume(log))
1323        /* FIXME: need better error handling */
1324        DMWARN("log resume failed");
1325    dm_rh_start_recovery(ms->rh);
1326}
1327
1328/*
1329 * device_status_char
1330 * @m: mirror device/leg we want the status of
1331 *
1332 * We return one character representing the most severe error
1333 * we have encountered.
1334 * A => Alive - No failures
1335 * D => Dead - A write failure occurred leaving mirror out-of-sync
1336 * S => Sync - A sychronization failure occurred, mirror out-of-sync
1337 * R => Read - A read failure occurred, mirror data unaffected
1338 *
1339 * Returns: <char>
1340 */
1341static char device_status_char(struct mirror *m)
1342{
1343    if (!atomic_read(&(m->error_count)))
1344        return 'A';
1345
1346    return (test_bit(DM_RAID1_FLUSH_ERROR, &(m->error_type))) ? 'F' :
1347        (test_bit(DM_RAID1_WRITE_ERROR, &(m->error_type))) ? 'D' :
1348        (test_bit(DM_RAID1_SYNC_ERROR, &(m->error_type))) ? 'S' :
1349        (test_bit(DM_RAID1_READ_ERROR, &(m->error_type))) ? 'R' : 'U';
1350}
1351
1352
1353static void mirror_status(struct dm_target *ti, status_type_t type,
1354              unsigned status_flags, char *result, unsigned maxlen)
1355{
1356    unsigned int m, sz = 0;
1357    struct mirror_set *ms = (struct mirror_set *) ti->private;
1358    struct dm_dirty_log *log = dm_rh_dirty_log(ms->rh);
1359    char buffer[ms->nr_mirrors + 1];
1360
1361    switch (type) {
1362    case STATUSTYPE_INFO:
1363        DMEMIT("%d ", ms->nr_mirrors);
1364        for (m = 0; m < ms->nr_mirrors; m++) {
1365            DMEMIT("%s ", ms->mirror[m].dev->name);
1366            buffer[m] = device_status_char(&(ms->mirror[m]));
1367        }
1368        buffer[m] = '\0';
1369
1370        DMEMIT("%llu/%llu 1 %s ",
1371              (unsigned long long)log->type->get_sync_count(log),
1372              (unsigned long long)ms->nr_regions, buffer);
1373
1374        sz += log->type->status(log, type, result+sz, maxlen-sz);
1375
1376        break;
1377
1378    case STATUSTYPE_TABLE:
1379        sz = log->type->status(log, type, result, maxlen);
1380
1381        DMEMIT("%d", ms->nr_mirrors);
1382        for (m = 0; m < ms->nr_mirrors; m++)
1383            DMEMIT(" %s %llu", ms->mirror[m].dev->name,
1384                   (unsigned long long)ms->mirror[m].offset);
1385
1386        if (ms->features & DM_RAID1_HANDLE_ERRORS)
1387            DMEMIT(" 1 handle_errors");
1388    }
1389}
1390
1391static int mirror_iterate_devices(struct dm_target *ti,
1392                  iterate_devices_callout_fn fn, void *data)
1393{
1394    struct mirror_set *ms = ti->private;
1395    int ret = 0;
1396    unsigned i;
1397
1398    for (i = 0; !ret && i < ms->nr_mirrors; i++)
1399        ret = fn(ti, ms->mirror[i].dev,
1400             ms->mirror[i].offset, ti->len, data);
1401
1402    return ret;
1403}
1404
1405static struct target_type mirror_target = {
1406    .name = "mirror",
1407    .version = {1, 13, 2},
1408    .module = THIS_MODULE,
1409    .ctr = mirror_ctr,
1410    .dtr = mirror_dtr,
1411    .map = mirror_map,
1412    .end_io = mirror_end_io,
1413    .presuspend = mirror_presuspend,
1414    .postsuspend = mirror_postsuspend,
1415    .resume = mirror_resume,
1416    .status = mirror_status,
1417    .iterate_devices = mirror_iterate_devices,
1418};
1419
1420static int __init dm_mirror_init(void)
1421{
1422    int r;
1423
1424    r = dm_register_target(&mirror_target);
1425    if (r < 0) {
1426        DMERR("Failed to register mirror target");
1427        goto bad_target;
1428    }
1429
1430    return 0;
1431
1432bad_target:
1433    return r;
1434}
1435
1436static void __exit dm_mirror_exit(void)
1437{
1438    dm_unregister_target(&mirror_target);
1439}
1440
1441/* Module hooks */
1442module_init(dm_mirror_init);
1443module_exit(dm_mirror_exit);
1444
1445MODULE_DESCRIPTION(DM_NAME " mirror target");
1446MODULE_AUTHOR("Joe Thornber");
1447MODULE_LICENSE("GPL");
1448

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