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    mempool_t *read_record_pool;
65
66    /* recovery */
67    region_t nr_regions;
68    int in_sync;
69    int log_failure;
70    int leg_failure;
71    atomic_t suspend;
72
73    atomic_t default_mirror; /* Default mirror */
74
75    struct workqueue_struct *kmirrord_wq;
76    struct work_struct kmirrord_work;
77    struct timer_list timer;
78    unsigned long timer_pending;
79
80    struct work_struct trigger_event;
81
82    unsigned nr_mirrors;
83    struct mirror mirror[0];
84};
85
86static void wakeup_mirrord(void *context)
87{
88    struct mirror_set *ms = context;
89
90    queue_work(ms->kmirrord_wq, &ms->kmirrord_work);
91}
92
93static void delayed_wake_fn(unsigned long data)
94{
95    struct mirror_set *ms = (struct mirror_set *) data;
96
97    clear_bit(0, &ms->timer_pending);
98    wakeup_mirrord(ms);
99}
100
101static void delayed_wake(struct mirror_set *ms)
102{
103    if (test_and_set_bit(0, &ms->timer_pending))
104        return;
105
106    ms->timer.expires = jiffies + HZ / 5;
107    ms->timer.data = (unsigned long) ms;
108    ms->timer.function = delayed_wake_fn;
109    add_timer(&ms->timer);
110}
111
112static void wakeup_all_recovery_waiters(void *context)
113{
114    wake_up_all(&_kmirrord_recovery_stopped);
115}
116
117static void queue_bio(struct mirror_set *ms, struct bio *bio, int rw)
118{
119    unsigned long flags;
120    int should_wake = 0;
121    struct bio_list *bl;
122
123    bl = (rw == WRITE) ? &ms->writes : &ms->reads;
124    spin_lock_irqsave(&ms->lock, flags);
125    should_wake = !(bl->head);
126    bio_list_add(bl, bio);
127    spin_unlock_irqrestore(&ms->lock, flags);
128
129    if (should_wake)
130        wakeup_mirrord(ms);
131}
132
133static void dispatch_bios(void *context, struct bio_list *bio_list)
134{
135    struct mirror_set *ms = context;
136    struct bio *bio;
137
138    while ((bio = bio_list_pop(bio_list)))
139        queue_bio(ms, bio, WRITE);
140}
141
142#define MIN_READ_RECORDS 20
143struct dm_raid1_read_record {
144    struct mirror *m;
145    struct dm_bio_details details;
146};
147
148static struct kmem_cache *_dm_raid1_read_record_cache;
149
150/*
151 * Every mirror should look like this one.
152 */
153#define DEFAULT_MIRROR 0
154
155/*
156 * This is yucky. We squirrel the mirror struct away inside
157 * bi_next for read/write buffers. This is safe since the bh
158 * doesn't get submitted to the lower levels of block layer.
159 */
160static struct mirror *bio_get_m(struct bio *bio)
161{
162    return (struct mirror *) bio->bi_next;
163}
164
165static void bio_set_m(struct bio *bio, struct mirror *m)
166{
167    bio->bi_next = (struct bio *) m;
168}
169
170static struct mirror *get_default_mirror(struct mirror_set *ms)
171{
172    return &ms->mirror[atomic_read(&ms->default_mirror)];
173}
174
175static void set_default_mirror(struct mirror *m)
176{
177    struct mirror_set *ms = m->ms;
178    struct mirror *m0 = &(ms->mirror[0]);
179
180    atomic_set(&ms->default_mirror, m - m0);
181}
182
183static struct mirror *get_valid_mirror(struct mirror_set *ms)
184{
185    struct mirror *m;
186
187    for (m = ms->mirror; m < ms->mirror + ms->nr_mirrors; m++)
188        if (!atomic_read(&m->error_count))
189            return m;
190
191    return NULL;
192}
193
194/* fail_mirror
195 * @m: mirror device to fail
196 * @error_type: one of the enum's, DM_RAID1_*_ERROR
197 *
198 * If errors are being handled, record the type of
199 * error encountered for this device. If this type
200 * of error has already been recorded, we can return;
201 * otherwise, we must signal userspace by triggering
202 * an event. Additionally, if the device is the
203 * primary device, we must choose a new primary, but
204 * only if the mirror is in-sync.
205 *
206 * This function must not block.
207 */
208static void fail_mirror(struct mirror *m, enum dm_raid1_error error_type)
209{
210    struct mirror_set *ms = m->ms;
211    struct mirror *new;
212
213    ms->leg_failure = 1;
214
215    /*
216     * error_count is used for nothing more than a
217     * simple way to tell if a device has encountered
218     * errors.
219     */
220    atomic_inc(&m->error_count);
221
222    if (test_and_set_bit(error_type, &m->error_type))
223        return;
224
225    if (!errors_handled(ms))
226        return;
227
228    if (m != get_default_mirror(ms))
229        goto out;
230
231    if (!ms->in_sync) {
232        /*
233         * Better to issue requests to same failing device
234         * than to risk returning corrupt data.
235         */
236        DMERR("Primary mirror (%s) failed while out-of-sync: "
237              "Reads may fail.", m->dev->name);
238        goto out;
239    }
240
241    new = get_valid_mirror(ms);
242    if (new)
243        set_default_mirror(new);
244    else
245        DMWARN("All sides of mirror have failed.");
246
247out:
248    schedule_work(&ms->trigger_event);
249}
250
251static int mirror_flush(struct dm_target *ti)
252{
253    struct mirror_set *ms = ti->private;
254    unsigned long error_bits;
255
256    unsigned int i;
257    struct dm_io_region io[ms->nr_mirrors];
258    struct mirror *m;
259    struct dm_io_request io_req = {
260        .bi_rw = WRITE_FLUSH,
261        .mem.type = DM_IO_KMEM,
262        .mem.ptr.addr = NULL,
263        .client = ms->io_client,
264    };
265
266    for (i = 0, m = ms->mirror; i < ms->nr_mirrors; i++, m++) {
267        io[i].bdev = m->dev->bdev;
268        io[i].sector = 0;
269        io[i].count = 0;
270    }
271
272    error_bits = -1;
273    dm_io(&io_req, ms->nr_mirrors, io, &error_bits);
274    if (unlikely(error_bits != 0)) {
275        for (i = 0; i < ms->nr_mirrors; i++)
276            if (test_bit(i, &error_bits))
277                fail_mirror(ms->mirror + i,
278                        DM_RAID1_FLUSH_ERROR);
279        return -EIO;
280    }
281
282    return 0;
283}
284
285/*-----------------------------------------------------------------
286 * Recovery.
287 *
288 * When a mirror is first activated we may find that some regions
289 * are in the no-sync state. We have to recover these by
290 * recopying from the default mirror to all the others.
291 *---------------------------------------------------------------*/
292static void recovery_complete(int read_err, unsigned long write_err,
293                  void *context)
294{
295    struct dm_region *reg = context;
296    struct mirror_set *ms = dm_rh_region_context(reg);
297    int m, bit = 0;
298
299    if (read_err) {
300        /* Read error means the failure of default mirror. */
301        DMERR_LIMIT("Unable to read primary mirror during recovery");
302        fail_mirror(get_default_mirror(ms), DM_RAID1_SYNC_ERROR);
303    }
304
305    if (write_err) {
306        DMERR_LIMIT("Write error during recovery (error = 0x%lx)",
307                write_err);
308        /*
309         * Bits correspond to devices (excluding default mirror).
310         * The default mirror cannot change during recovery.
311         */
312        for (m = 0; m < ms->nr_mirrors; m++) {
313            if (&ms->mirror[m] == get_default_mirror(ms))
314                continue;
315            if (test_bit(bit, &write_err))
316                fail_mirror(ms->mirror + m,
317                        DM_RAID1_SYNC_ERROR);
318            bit++;
319        }
320    }
321
322    dm_rh_recovery_end(reg, !(read_err || write_err));
323}
324
325static int recover(struct mirror_set *ms, struct dm_region *reg)
326{
327    int r;
328    unsigned i;
329    struct dm_io_region from, to[DM_KCOPYD_MAX_REGIONS], *dest;
330    struct mirror *m;
331    unsigned long flags = 0;
332    region_t key = dm_rh_get_region_key(reg);
333    sector_t region_size = dm_rh_get_region_size(ms->rh);
334
335    /* fill in the source */
336    m = get_default_mirror(ms);
337    from.bdev = m->dev->bdev;
338    from.sector = m->offset + dm_rh_region_to_sector(ms->rh, key);
339    if (key == (ms->nr_regions - 1)) {
340        /*
341         * The final region may be smaller than
342         * region_size.
343         */
344        from.count = ms->ti->len & (region_size - 1);
345        if (!from.count)
346            from.count = region_size;
347    } else
348        from.count = region_size;
349
350    /* fill in the destinations */
351    for (i = 0, dest = to; i < ms->nr_mirrors; i++) {
352        if (&ms->mirror[i] == get_default_mirror(ms))
353            continue;
354
355        m = ms->mirror + i;
356        dest->bdev = m->dev->bdev;
357        dest->sector = m->offset + dm_rh_region_to_sector(ms->rh, key);
358        dest->count = from.count;
359        dest++;
360    }
361
362    /* hand to kcopyd */
363    if (!errors_handled(ms))
364        set_bit(DM_KCOPYD_IGNORE_ERROR, &flags);
365
366    r = dm_kcopyd_copy(ms->kcopyd_client, &from, ms->nr_mirrors - 1, to,
367               flags, recovery_complete, reg);
368
369    return r;
370}
371
372static void do_recovery(struct mirror_set *ms)
373{
374    struct dm_region *reg;
375    struct dm_dirty_log *log = dm_rh_dirty_log(ms->rh);
376    int r;
377
378    /*
379     * Start quiescing some regions.
380     */
381    dm_rh_recovery_prepare(ms->rh);
382
383    /*
384     * Copy any already quiesced regions.
385     */
386    while ((reg = dm_rh_recovery_start(ms->rh))) {
387        r = recover(ms, reg);
388        if (r)
389            dm_rh_recovery_end(reg, 0);
390    }
391
392    /*
393     * Update the in sync flag.
394     */
395    if (!ms->in_sync &&
396        (log->type->get_sync_count(log) == ms->nr_regions)) {
397        /* the sync is complete */
398        dm_table_event(ms->ti->table);
399        ms->in_sync = 1;
400    }
401}
402
403/*-----------------------------------------------------------------
404 * Reads
405 *---------------------------------------------------------------*/
406static struct mirror *choose_mirror(struct mirror_set *ms, sector_t sector)
407{
408    struct mirror *m = get_default_mirror(ms);
409
410    do {
411        if (likely(!atomic_read(&m->error_count)))
412            return m;
413
414        if (m-- == ms->mirror)
415            m += ms->nr_mirrors;
416    } while (m != get_default_mirror(ms));
417
418    return NULL;
419}
420
421static int default_ok(struct mirror *m)
422{
423    struct mirror *default_mirror = get_default_mirror(m->ms);
424
425    return !atomic_read(&default_mirror->error_count);
426}
427
428static int mirror_available(struct mirror_set *ms, struct bio *bio)
429{
430    struct dm_dirty_log *log = dm_rh_dirty_log(ms->rh);
431    region_t region = dm_rh_bio_to_region(ms->rh, bio);
432
433    if (log->type->in_sync(log, region, 0))
434        return choose_mirror(ms, bio->bi_sector) ? 1 : 0;
435
436    return 0;
437}
438
439/*
440 * remap a buffer to a particular mirror.
441 */
442static sector_t map_sector(struct mirror *m, struct bio *bio)
443{
444    if (unlikely(!bio->bi_size))
445        return 0;
446    return m->offset + dm_target_offset(m->ms->ti, bio->bi_sector);
447}
448
449static void map_bio(struct mirror *m, struct bio *bio)
450{
451    bio->bi_bdev = m->dev->bdev;
452    bio->bi_sector = map_sector(m, bio);
453}
454
455static void map_region(struct dm_io_region *io, struct mirror *m,
456               struct bio *bio)
457{
458    io->bdev = m->dev->bdev;
459    io->sector = map_sector(m, bio);
460    io->count = bio->bi_size >> 9;
461}
462
463static void hold_bio(struct mirror_set *ms, struct bio *bio)
464{
465    /*
466     * Lock is required to avoid race condition during suspend
467     * process.
468     */
469    spin_lock_irq(&ms->lock);
470
471    if (atomic_read(&ms->suspend)) {
472        spin_unlock_irq(&ms->lock);
473
474        /*
475         * If device is suspended, complete the bio.
476         */
477        if (dm_noflush_suspending(ms->ti))
478            bio_endio(bio, DM_ENDIO_REQUEUE);
479        else
480            bio_endio(bio, -EIO);
481        return;
482    }
483
484    /*
485     * Hold bio until the suspend is complete.
486     */
487    bio_list_add(&ms->holds, bio);
488    spin_unlock_irq(&ms->lock);
489}
490
491/*-----------------------------------------------------------------
492 * Reads
493 *---------------------------------------------------------------*/
494static void read_callback(unsigned long error, void *context)
495{
496    struct bio *bio = context;
497    struct mirror *m;
498
499    m = bio_get_m(bio);
500    bio_set_m(bio, NULL);
501
502    if (likely(!error)) {
503        bio_endio(bio, 0);
504        return;
505    }
506
507    fail_mirror(m, DM_RAID1_READ_ERROR);
508
509    if (likely(default_ok(m)) || mirror_available(m->ms, bio)) {
510        DMWARN_LIMIT("Read failure on mirror device %s. "
511                 "Trying alternative device.",
512                 m->dev->name);
513        queue_bio(m->ms, bio, bio_rw(bio));
514        return;
515    }
516
517    DMERR_LIMIT("Read failure on mirror device %s. Failing I/O.",
518            m->dev->name);
519    bio_endio(bio, -EIO);
520}
521
522/* Asynchronous read. */
523static void read_async_bio(struct mirror *m, struct bio *bio)
524{
525    struct dm_io_region io;
526    struct dm_io_request io_req = {
527        .bi_rw = READ,
528        .mem.type = DM_IO_BVEC,
529        .mem.ptr.bvec = bio->bi_io_vec + bio->bi_idx,
530        .notify.fn = read_callback,
531        .notify.context = bio,
532        .client = m->ms->io_client,
533    };
534
535    map_region(&io, m, bio);
536    bio_set_m(bio, m);
537    BUG_ON(dm_io(&io_req, 1, &io, NULL));
538}
539
540static inline int region_in_sync(struct mirror_set *ms, region_t region,
541                 int may_block)
542{
543    int state = dm_rh_get_state(ms->rh, region, may_block);
544    return state == DM_RH_CLEAN || state == DM_RH_DIRTY;
545}
546
547static void do_reads(struct mirror_set *ms, struct bio_list *reads)
548{
549    region_t region;
550    struct bio *bio;
551    struct mirror *m;
552
553    while ((bio = bio_list_pop(reads))) {
554        region = dm_rh_bio_to_region(ms->rh, bio);
555        m = get_default_mirror(ms);
556
557        /*
558         * We can only read balance if the region is in sync.
559         */
560        if (likely(region_in_sync(ms, region, 1)))
561            m = choose_mirror(ms, bio->bi_sector);
562        else if (m && atomic_read(&m->error_count))
563            m = NULL;
564
565        if (likely(m))
566            read_async_bio(m, bio);
567        else
568            bio_endio(bio, -EIO);
569    }
570}
571
572/*-----------------------------------------------------------------
573 * Writes.
574 *
575 * We do different things with the write io depending on the
576 * state of the region that it's in:
577 *
578 * SYNC: increment pending, use kcopyd to write to *all* mirrors
579 * RECOVERING: delay the io until recovery completes
580 * NOSYNC: increment pending, just write to the default mirror
581 *---------------------------------------------------------------*/
582
583
584static void write_callback(unsigned long error, void *context)
585{
586    unsigned i, ret = 0;
587    struct bio *bio = (struct bio *) context;
588    struct mirror_set *ms;
589    int should_wake = 0;
590    unsigned long flags;
591
592    ms = bio_get_m(bio)->ms;
593    bio_set_m(bio, NULL);
594
595    /*
596     * NOTE: We don't decrement the pending count here,
597     * instead it is done by the targets endio function.
598     * This way we handle both writes to SYNC and NOSYNC
599     * regions with the same code.
600     */
601    if (likely(!error)) {
602        bio_endio(bio, ret);
603        return;
604    }
605
606    for (i = 0; i < ms->nr_mirrors; i++)
607        if (test_bit(i, &error))
608            fail_mirror(ms->mirror + i, DM_RAID1_WRITE_ERROR);
609
610    /*
611     * Need to raise event. Since raising
612     * events can block, we need to do it in
613     * the main thread.
614     */
615    spin_lock_irqsave(&ms->lock, flags);
616    if (!ms->failures.head)
617        should_wake = 1;
618    bio_list_add(&ms->failures, bio);
619    spin_unlock_irqrestore(&ms->lock, flags);
620    if (should_wake)
621        wakeup_mirrord(ms);
622}
623
624static void do_write(struct mirror_set *ms, struct bio *bio)
625{
626    unsigned int i;
627    struct dm_io_region io[ms->nr_mirrors], *dest = io;
628    struct mirror *m;
629    struct dm_io_request io_req = {
630        .bi_rw = WRITE | (bio->bi_rw & WRITE_FLUSH_FUA),
631        .mem.type = DM_IO_BVEC,
632        .mem.ptr.bvec = bio->bi_io_vec + bio->bi_idx,
633        .notify.fn = write_callback,
634        .notify.context = bio,
635        .client = ms->io_client,
636    };
637
638    if (bio->bi_rw & REQ_DISCARD) {
639        io_req.bi_rw |= REQ_DISCARD;
640        io_req.mem.type = DM_IO_KMEM;
641        io_req.mem.ptr.addr = NULL;
642    }
643
644    for (i = 0, m = ms->mirror; i < ms->nr_mirrors; i++, m++)
645        map_region(dest++, m, bio);
646
647    /*
648     * Use default mirror because we only need it to retrieve the reference
649     * to the mirror set in write_callback().
650     */
651    bio_set_m(bio, get_default_mirror(ms));
652
653    BUG_ON(dm_io(&io_req, ms->nr_mirrors, io, NULL));
654}
655
656static void do_writes(struct mirror_set *ms, struct bio_list *writes)
657{
658    int state;
659    struct bio *bio;
660    struct bio_list sync, nosync, recover, *this_list = NULL;
661    struct bio_list requeue;
662    struct dm_dirty_log *log = dm_rh_dirty_log(ms->rh);
663    region_t region;
664
665    if (!writes->head)
666        return;
667
668    /*
669     * Classify each write.
670     */
671    bio_list_init(&sync);
672    bio_list_init(&nosync);
673    bio_list_init(&recover);
674    bio_list_init(&requeue);
675
676    while ((bio = bio_list_pop(writes))) {
677        if ((bio->bi_rw & REQ_FLUSH) ||
678            (bio->bi_rw & REQ_DISCARD)) {
679            bio_list_add(&sync, bio);
680            continue;
681        }
682
683        region = dm_rh_bio_to_region(ms->rh, bio);
684
685        if (log->type->is_remote_recovering &&
686            log->type->is_remote_recovering(log, region)) {
687            bio_list_add(&requeue, bio);
688            continue;
689        }
690
691        state = dm_rh_get_state(ms->rh, region, 1);
692        switch (state) {
693        case DM_RH_CLEAN:
694        case DM_RH_DIRTY:
695            this_list = &sync;
696            break;
697
698        case DM_RH_NOSYNC:
699            this_list = &nosync;
700            break;
701
702        case DM_RH_RECOVERING:
703            this_list = &recover;
704            break;
705        }
706
707        bio_list_add(this_list, bio);
708    }
709
710    /*
711     * Add bios that are delayed due to remote recovery
712     * back on to the write queue
713     */
714    if (unlikely(requeue.head)) {
715        spin_lock_irq(&ms->lock);
716        bio_list_merge(&ms->writes, &requeue);
717        spin_unlock_irq(&ms->lock);
718        delayed_wake(ms);
719    }
720
721    /*
722     * Increment the pending counts for any regions that will
723     * be written to (writes to recover regions are going to
724     * be delayed).
725     */
726    dm_rh_inc_pending(ms->rh, &sync);
727    dm_rh_inc_pending(ms->rh, &nosync);
728
729    /*
730     * If the flush fails on a previous call and succeeds here,
731     * we must not reset the log_failure variable. We need
732     * userspace interaction to do that.
733     */
734    ms->log_failure = dm_rh_flush(ms->rh) ? 1 : ms->log_failure;
735
736    /*
737     * Dispatch io.
738     */
739    if (unlikely(ms->log_failure) && errors_handled(ms)) {
740        spin_lock_irq(&ms->lock);
741        bio_list_merge(&ms->failures, &sync);
742        spin_unlock_irq(&ms->lock);
743        wakeup_mirrord(ms);
744    } else
745        while ((bio = bio_list_pop(&sync)))
746            do_write(ms, bio);
747
748    while ((bio = bio_list_pop(&recover)))
749        dm_rh_delay(ms->rh, bio);
750
751    while ((bio = bio_list_pop(&nosync))) {
752        if (unlikely(ms->leg_failure) && errors_handled(ms)) {
753            spin_lock_irq(&ms->lock);
754            bio_list_add(&ms->failures, bio);
755            spin_unlock_irq(&ms->lock);
756            wakeup_mirrord(ms);
757        } else {
758            map_bio(get_default_mirror(ms), bio);
759            generic_make_request(bio);
760        }
761    }
762}
763
764static void do_failures(struct mirror_set *ms, struct bio_list *failures)
765{
766    struct bio *bio;
767
768    if (likely(!failures->head))
769        return;
770
771    /*
772     * If the log has failed, unattempted writes are being
773     * put on the holds list. We can't issue those writes
774     * until a log has been marked, so we must store them.
775     *
776     * If a 'noflush' suspend is in progress, we can requeue
777     * the I/O's to the core. This give userspace a chance
778     * to reconfigure the mirror, at which point the core
779     * will reissue the writes. If the 'noflush' flag is
780     * not set, we have no choice but to return errors.
781     *
782     * Some writes on the failures list may have been
783     * submitted before the log failure and represent a
784     * failure to write to one of the devices. It is ok
785     * for us to treat them the same and requeue them
786     * as well.
787     */
788    while ((bio = bio_list_pop(failures))) {
789        if (!ms->log_failure) {
790            ms->in_sync = 0;
791            dm_rh_mark_nosync(ms->rh, bio);
792        }
793
794        /*
795         * If all the legs are dead, fail the I/O.
796         * If we have been told to handle errors, hold the bio
797         * and wait for userspace to deal with the problem.
798         * Otherwise pretend that the I/O succeeded. (This would
799         * be wrong if the failed leg returned after reboot and
800         * got replicated back to the good legs.)
801         */
802        if (!get_valid_mirror(ms))
803            bio_endio(bio, -EIO);
804        else if (errors_handled(ms))
805            hold_bio(ms, bio);
806        else
807            bio_endio(bio, 0);
808    }
809}
810
811static void trigger_event(struct work_struct *work)
812{
813    struct mirror_set *ms =
814        container_of(work, struct mirror_set, trigger_event);
815
816    dm_table_event(ms->ti->table);
817}
818
819/*-----------------------------------------------------------------
820 * kmirrord
821 *---------------------------------------------------------------*/
822static void do_mirror(struct work_struct *work)
823{
824    struct mirror_set *ms = container_of(work, struct mirror_set,
825                         kmirrord_work);
826    struct bio_list reads, writes, failures;
827    unsigned long flags;
828
829    spin_lock_irqsave(&ms->lock, flags);
830    reads = ms->reads;
831    writes = ms->writes;
832    failures = ms->failures;
833    bio_list_init(&ms->reads);
834    bio_list_init(&ms->writes);
835    bio_list_init(&ms->failures);
836    spin_unlock_irqrestore(&ms->lock, flags);
837
838    dm_rh_update_states(ms->rh, errors_handled(ms));
839    do_recovery(ms);
840    do_reads(ms, &reads);
841    do_writes(ms, &writes);
842    do_failures(ms, &failures);
843}
844
845/*-----------------------------------------------------------------
846 * Target functions
847 *---------------------------------------------------------------*/
848static struct mirror_set *alloc_context(unsigned int nr_mirrors,
849                    uint32_t region_size,
850                    struct dm_target *ti,
851                    struct dm_dirty_log *dl)
852{
853    size_t len;
854    struct mirror_set *ms = NULL;
855
856    len = sizeof(*ms) + (sizeof(ms->mirror[0]) * nr_mirrors);
857
858    ms = kzalloc(len, GFP_KERNEL);
859    if (!ms) {
860        ti->error = "Cannot allocate mirror context";
861        return NULL;
862    }
863
864    spin_lock_init(&ms->lock);
865    bio_list_init(&ms->reads);
866    bio_list_init(&ms->writes);
867    bio_list_init(&ms->failures);
868    bio_list_init(&ms->holds);
869
870    ms->ti = ti;
871    ms->nr_mirrors = nr_mirrors;
872    ms->nr_regions = dm_sector_div_up(ti->len, region_size);
873    ms->in_sync = 0;
874    ms->log_failure = 0;
875    ms->leg_failure = 0;
876    atomic_set(&ms->suspend, 0);
877    atomic_set(&ms->default_mirror, DEFAULT_MIRROR);
878
879    ms->read_record_pool = mempool_create_slab_pool(MIN_READ_RECORDS,
880                        _dm_raid1_read_record_cache);
881
882    if (!ms->read_record_pool) {
883        ti->error = "Error creating mirror read_record_pool";
884        kfree(ms);
885        return NULL;
886    }
887
888    ms->io_client = dm_io_client_create();
889    if (IS_ERR(ms->io_client)) {
890        ti->error = "Error creating dm_io client";
891        mempool_destroy(ms->read_record_pool);
892        kfree(ms);
893         return NULL;
894    }
895
896    ms->rh = dm_region_hash_create(ms, dispatch_bios, wakeup_mirrord,
897                       wakeup_all_recovery_waiters,
898                       ms->ti->begin, MAX_RECOVERY,
899                       dl, region_size, ms->nr_regions);
900    if (IS_ERR(ms->rh)) {
901        ti->error = "Error creating dirty region hash";
902        dm_io_client_destroy(ms->io_client);
903        mempool_destroy(ms->read_record_pool);
904        kfree(ms);
905        return NULL;
906    }
907
908    return ms;
909}
910
911static void free_context(struct mirror_set *ms, struct dm_target *ti,
912             unsigned int m)
913{
914    while (m--)
915        dm_put_device(ti, ms->mirror[m].dev);
916
917    dm_io_client_destroy(ms->io_client);
918    dm_region_hash_destroy(ms->rh);
919    mempool_destroy(ms->read_record_pool);
920    kfree(ms);
921}
922
923static int get_mirror(struct mirror_set *ms, struct dm_target *ti,
924              unsigned int mirror, char **argv)
925{
926    unsigned long long offset;
927    char dummy;
928
929    if (sscanf(argv[1], "%llu%c", &offset, &dummy) != 1) {
930        ti->error = "Invalid offset";
931        return -EINVAL;
932    }
933
934    if (dm_get_device(ti, argv[0], dm_table_get_mode(ti->table),
935              &ms->mirror[mirror].dev)) {
936        ti->error = "Device lookup failure";
937        return -ENXIO;
938    }
939
940    ms->mirror[mirror].ms = ms;
941    atomic_set(&(ms->mirror[mirror].error_count), 0);
942    ms->mirror[mirror].error_type = 0;
943    ms->mirror[mirror].offset = offset;
944
945    return 0;
946}
947
948/*
949 * Create dirty log: log_type #log_params <log_params>
950 */
951static struct dm_dirty_log *create_dirty_log(struct dm_target *ti,
952                         unsigned argc, char **argv,
953                         unsigned *args_used)
954{
955    unsigned param_count;
956    struct dm_dirty_log *dl;
957    char dummy;
958
959    if (argc < 2) {
960        ti->error = "Insufficient mirror log arguments";
961        return NULL;
962    }
963
964    if (sscanf(argv[1], "%u%c", &param_count, &dummy) != 1) {
965        ti->error = "Invalid mirror log argument count";
966        return NULL;
967    }
968
969    *args_used = 2 + param_count;
970
971    if (argc < *args_used) {
972        ti->error = "Insufficient mirror log arguments";
973        return NULL;
974    }
975
976    dl = dm_dirty_log_create(argv[0], ti, mirror_flush, param_count,
977                 argv + 2);
978    if (!dl) {
979        ti->error = "Error creating mirror dirty log";
980        return NULL;
981    }
982
983    return dl;
984}
985
986static int parse_features(struct mirror_set *ms, unsigned argc, char **argv,
987              unsigned *args_used)
988{
989    unsigned num_features;
990    struct dm_target *ti = ms->ti;
991    char dummy;
992
993    *args_used = 0;
994
995    if (!argc)
996        return 0;
997
998    if (sscanf(argv[0], "%u%c", &num_features, &dummy) != 1) {
999        ti->error = "Invalid number of features";
1000        return -EINVAL;
1001    }
1002
1003    argc--;
1004    argv++;
1005    (*args_used)++;
1006
1007    if (num_features > argc) {
1008        ti->error = "Not enough arguments to support feature count";
1009        return -EINVAL;
1010    }
1011
1012    if (!strcmp("handle_errors", argv[0]))
1013        ms->features |= DM_RAID1_HANDLE_ERRORS;
1014    else {
1015        ti->error = "Unrecognised feature requested";
1016        return -EINVAL;
1017    }
1018
1019    (*args_used)++;
1020
1021    return 0;
1022}
1023
1024/*
1025 * Construct a mirror mapping:
1026 *
1027 * log_type #log_params <log_params>
1028 * #mirrors [mirror_path offset]{2,}
1029 * [#features <features>]
1030 *
1031 * log_type is "core" or "disk"
1032 * #log_params is between 1 and 3
1033 *
1034 * If present, features must be "handle_errors".
1035 */
1036static int mirror_ctr(struct dm_target *ti, unsigned int argc, char **argv)
1037{
1038    int r;
1039    unsigned int nr_mirrors, m, args_used;
1040    struct mirror_set *ms;
1041    struct dm_dirty_log *dl;
1042    char dummy;
1043
1044    dl = create_dirty_log(ti, argc, argv, &args_used);
1045    if (!dl)
1046        return -EINVAL;
1047
1048    argv += args_used;
1049    argc -= args_used;
1050
1051    if (!argc || sscanf(argv[0], "%u%c", &nr_mirrors, &dummy) != 1 ||
1052        nr_mirrors < 2 || nr_mirrors > DM_KCOPYD_MAX_REGIONS + 1) {
1053        ti->error = "Invalid number of mirrors";
1054        dm_dirty_log_destroy(dl);
1055        return -EINVAL;
1056    }
1057
1058    argv++, argc--;
1059
1060    if (argc < nr_mirrors * 2) {
1061        ti->error = "Too few mirror arguments";
1062        dm_dirty_log_destroy(dl);
1063        return -EINVAL;
1064    }
1065
1066    ms = alloc_context(nr_mirrors, dl->type->get_region_size(dl), ti, dl);
1067    if (!ms) {
1068        dm_dirty_log_destroy(dl);
1069        return -ENOMEM;
1070    }
1071
1072    /* Get the mirror parameter sets */
1073    for (m = 0; m < nr_mirrors; m++) {
1074        r = get_mirror(ms, ti, m, argv);
1075        if (r) {
1076            free_context(ms, ti, m);
1077            return r;
1078        }
1079        argv += 2;
1080        argc -= 2;
1081    }
1082
1083    ti->private = ms;
1084
1085    r = dm_set_target_max_io_len(ti, dm_rh_get_region_size(ms->rh));
1086    if (r)
1087        goto err_free_context;
1088
1089    ti->num_flush_requests = 1;
1090    ti->num_discard_requests = 1;
1091    ti->discard_zeroes_data_unsupported = true;
1092
1093    ms->kmirrord_wq = alloc_workqueue("kmirrord",
1094                      WQ_NON_REENTRANT | WQ_MEM_RECLAIM, 0);
1095    if (!ms->kmirrord_wq) {
1096        DMERR("couldn't start kmirrord");
1097        r = -ENOMEM;
1098        goto err_free_context;
1099    }
1100    INIT_WORK(&ms->kmirrord_work, do_mirror);
1101    init_timer(&ms->timer);
1102    ms->timer_pending = 0;
1103    INIT_WORK(&ms->trigger_event, trigger_event);
1104
1105    r = parse_features(ms, argc, argv, &args_used);
1106    if (r)
1107        goto err_destroy_wq;
1108
1109    argv += args_used;
1110    argc -= args_used;
1111
1112    /*
1113     * Any read-balancing addition depends on the
1114     * DM_RAID1_HANDLE_ERRORS flag being present.
1115     * This is because the decision to balance depends
1116     * on the sync state of a region. If the above
1117     * flag is not present, we ignore errors; and
1118     * the sync state may be inaccurate.
1119     */
1120
1121    if (argc) {
1122        ti->error = "Too many mirror arguments";
1123        r = -EINVAL;
1124        goto err_destroy_wq;
1125    }
1126
1127    ms->kcopyd_client = dm_kcopyd_client_create();
1128    if (IS_ERR(ms->kcopyd_client)) {
1129        r = PTR_ERR(ms->kcopyd_client);
1130        goto err_destroy_wq;
1131    }
1132
1133    wakeup_mirrord(ms);
1134    return 0;
1135
1136err_destroy_wq:
1137    destroy_workqueue(ms->kmirrord_wq);
1138err_free_context:
1139    free_context(ms, ti, ms->nr_mirrors);
1140    return r;
1141}
1142
1143static void mirror_dtr(struct dm_target *ti)
1144{
1145    struct mirror_set *ms = (struct mirror_set *) ti->private;
1146
1147    del_timer_sync(&ms->timer);
1148    flush_workqueue(ms->kmirrord_wq);
1149    flush_work_sync(&ms->trigger_event);
1150    dm_kcopyd_client_destroy(ms->kcopyd_client);
1151    destroy_workqueue(ms->kmirrord_wq);
1152    free_context(ms, ti, ms->nr_mirrors);
1153}
1154
1155/*
1156 * Mirror mapping function
1157 */
1158static int mirror_map(struct dm_target *ti, struct bio *bio,
1159              union map_info *map_context)
1160{
1161    int r, rw = bio_rw(bio);
1162    struct mirror *m;
1163    struct mirror_set *ms = ti->private;
1164    struct dm_raid1_read_record *read_record = NULL;
1165    struct dm_dirty_log *log = dm_rh_dirty_log(ms->rh);
1166
1167    if (rw == WRITE) {
1168        /* Save region for mirror_end_io() handler */
1169        map_context->ll = dm_rh_bio_to_region(ms->rh, bio);
1170        queue_bio(ms, bio, rw);
1171        return DM_MAPIO_SUBMITTED;
1172    }
1173
1174    r = log->type->in_sync(log, dm_rh_bio_to_region(ms->rh, bio), 0);
1175    if (r < 0 && r != -EWOULDBLOCK)
1176        return r;
1177
1178    /*
1179     * If region is not in-sync queue the bio.
1180     */
1181    if (!r || (r == -EWOULDBLOCK)) {
1182        if (rw == READA)
1183            return -EWOULDBLOCK;
1184
1185        queue_bio(ms, bio, rw);
1186        return DM_MAPIO_SUBMITTED;
1187    }
1188
1189    /*
1190     * The region is in-sync and we can perform reads directly.
1191     * Store enough information so we can retry if it fails.
1192     */
1193    m = choose_mirror(ms, bio->bi_sector);
1194    if (unlikely(!m))
1195        return -EIO;
1196
1197    read_record = mempool_alloc(ms->read_record_pool, GFP_NOIO);
1198    if (likely(read_record)) {
1199        dm_bio_record(&read_record->details, bio);
1200        map_context->ptr = read_record;
1201        read_record->m = m;
1202    }
1203
1204    map_bio(m, bio);
1205
1206    return DM_MAPIO_REMAPPED;
1207}
1208
1209static int mirror_end_io(struct dm_target *ti, struct bio *bio,
1210             int error, union map_info *map_context)
1211{
1212    int rw = bio_rw(bio);
1213    struct mirror_set *ms = (struct mirror_set *) ti->private;
1214    struct mirror *m = NULL;
1215    struct dm_bio_details *bd = NULL;
1216    struct dm_raid1_read_record *read_record = map_context->ptr;
1217
1218    /*
1219     * We need to dec pending if this was a write.
1220     */
1221    if (rw == WRITE) {
1222        if (!(bio->bi_rw & (REQ_FLUSH | REQ_DISCARD)))
1223            dm_rh_dec(ms->rh, map_context->ll);
1224        return error;
1225    }
1226
1227    if (error == -EOPNOTSUPP)
1228        goto out;
1229
1230    if ((error == -EWOULDBLOCK) && (bio->bi_rw & REQ_RAHEAD))
1231        goto out;
1232
1233    if (unlikely(error)) {
1234        if (!read_record) {
1235            /*
1236             * There wasn't enough memory to record necessary
1237             * information for a retry or there was no other
1238             * mirror in-sync.
1239             */
1240            DMERR_LIMIT("Mirror read failed.");
1241            return -EIO;
1242        }
1243
1244        m = read_record->m;
1245
1246        DMERR("Mirror read failed from %s. Trying alternative device.",
1247              m->dev->name);
1248
1249        fail_mirror(m, DM_RAID1_READ_ERROR);
1250
1251        /*
1252         * A failed read is requeued for another attempt using an intact
1253         * mirror.
1254         */
1255        if (default_ok(m) || mirror_available(ms, bio)) {
1256            bd = &read_record->details;
1257
1258            dm_bio_restore(bd, bio);
1259            mempool_free(read_record, ms->read_record_pool);
1260            map_context->ptr = NULL;
1261            queue_bio(ms, bio, rw);
1262            return 1;
1263        }
1264        DMERR("All replicated volumes dead, failing I/O");
1265    }
1266
1267out:
1268    if (read_record) {
1269        mempool_free(read_record, ms->read_record_pool);
1270        map_context->ptr = NULL;
1271    }
1272
1273    return error;
1274}
1275
1276static void mirror_presuspend(struct dm_target *ti)
1277{
1278    struct mirror_set *ms = (struct mirror_set *) ti->private;
1279    struct dm_dirty_log *log = dm_rh_dirty_log(ms->rh);
1280
1281    struct bio_list holds;
1282    struct bio *bio;
1283
1284    atomic_set(&ms->suspend, 1);
1285
1286    /*
1287     * Process bios in the hold list to start recovery waiting
1288     * for bios in the hold list. After the process, no bio has
1289     * a chance to be added in the hold list because ms->suspend
1290     * is set.
1291     */
1292    spin_lock_irq(&ms->lock);
1293    holds = ms->holds;
1294    bio_list_init(&ms->holds);
1295    spin_unlock_irq(&ms->lock);
1296
1297    while ((bio = bio_list_pop(&holds)))
1298        hold_bio(ms, bio);
1299
1300    /*
1301     * We must finish up all the work that we've
1302     * generated (i.e. recovery work).
1303     */
1304    dm_rh_stop_recovery(ms->rh);
1305
1306    wait_event(_kmirrord_recovery_stopped,
1307           !dm_rh_recovery_in_flight(ms->rh));
1308
1309    if (log->type->presuspend && log->type->presuspend(log))
1310        /* FIXME: need better error handling */
1311        DMWARN("log presuspend failed");
1312
1313    /*
1314     * Now that recovery is complete/stopped and the
1315     * delayed bios are queued, we need to wait for
1316     * the worker thread to complete. This way,
1317     * we know that all of our I/O has been pushed.
1318     */
1319    flush_workqueue(ms->kmirrord_wq);
1320}
1321
1322static void mirror_postsuspend(struct dm_target *ti)
1323{
1324    struct mirror_set *ms = ti->private;
1325    struct dm_dirty_log *log = dm_rh_dirty_log(ms->rh);
1326
1327    if (log->type->postsuspend && log->type->postsuspend(log))
1328        /* FIXME: need better error handling */
1329        DMWARN("log postsuspend failed");
1330}
1331
1332static void mirror_resume(struct dm_target *ti)
1333{
1334    struct mirror_set *ms = ti->private;
1335    struct dm_dirty_log *log = dm_rh_dirty_log(ms->rh);
1336
1337    atomic_set(&ms->suspend, 0);
1338    if (log->type->resume && log->type->resume(log))
1339        /* FIXME: need better error handling */
1340        DMWARN("log resume failed");
1341    dm_rh_start_recovery(ms->rh);
1342}
1343
1344/*
1345 * device_status_char
1346 * @m: mirror device/leg we want the status of
1347 *
1348 * We return one character representing the most severe error
1349 * we have encountered.
1350 * A => Alive - No failures
1351 * D => Dead - A write failure occurred leaving mirror out-of-sync
1352 * S => Sync - A sychronization failure occurred, mirror out-of-sync
1353 * R => Read - A read failure occurred, mirror data unaffected
1354 *
1355 * Returns: <char>
1356 */
1357static char device_status_char(struct mirror *m)
1358{
1359    if (!atomic_read(&(m->error_count)))
1360        return 'A';
1361
1362    return (test_bit(DM_RAID1_FLUSH_ERROR, &(m->error_type))) ? 'F' :
1363        (test_bit(DM_RAID1_WRITE_ERROR, &(m->error_type))) ? 'D' :
1364        (test_bit(DM_RAID1_SYNC_ERROR, &(m->error_type))) ? 'S' :
1365        (test_bit(DM_RAID1_READ_ERROR, &(m->error_type))) ? 'R' : 'U';
1366}
1367
1368
1369static int mirror_status(struct dm_target *ti, status_type_t type,
1370             unsigned status_flags, char *result, unsigned maxlen)
1371{
1372    unsigned int m, sz = 0;
1373    struct mirror_set *ms = (struct mirror_set *) ti->private;
1374    struct dm_dirty_log *log = dm_rh_dirty_log(ms->rh);
1375    char buffer[ms->nr_mirrors + 1];
1376
1377    switch (type) {
1378    case STATUSTYPE_INFO:
1379        DMEMIT("%d ", ms->nr_mirrors);
1380        for (m = 0; m < ms->nr_mirrors; m++) {
1381            DMEMIT("%s ", ms->mirror[m].dev->name);
1382            buffer[m] = device_status_char(&(ms->mirror[m]));
1383        }
1384        buffer[m] = '\0';
1385
1386        DMEMIT("%llu/%llu 1 %s ",
1387              (unsigned long long)log->type->get_sync_count(log),
1388              (unsigned long long)ms->nr_regions, buffer);
1389
1390        sz += log->type->status(log, type, result+sz, maxlen-sz);
1391
1392        break;
1393
1394    case STATUSTYPE_TABLE:
1395        sz = log->type->status(log, type, result, maxlen);
1396
1397        DMEMIT("%d", ms->nr_mirrors);
1398        for (m = 0; m < ms->nr_mirrors; m++)
1399            DMEMIT(" %s %llu", ms->mirror[m].dev->name,
1400                   (unsigned long long)ms->mirror[m].offset);
1401
1402        if (ms->features & DM_RAID1_HANDLE_ERRORS)
1403            DMEMIT(" 1 handle_errors");
1404    }
1405
1406    return 0;
1407}
1408
1409static int mirror_iterate_devices(struct dm_target *ti,
1410                  iterate_devices_callout_fn fn, void *data)
1411{
1412    struct mirror_set *ms = ti->private;
1413    int ret = 0;
1414    unsigned i;
1415
1416    for (i = 0; !ret && i < ms->nr_mirrors; i++)
1417        ret = fn(ti, ms->mirror[i].dev,
1418             ms->mirror[i].offset, ti->len, data);
1419
1420    return ret;
1421}
1422
1423static struct target_type mirror_target = {
1424    .name = "mirror",
1425    .version = {1, 12, 1},
1426    .module = THIS_MODULE,
1427    .ctr = mirror_ctr,
1428    .dtr = mirror_dtr,
1429    .map = mirror_map,
1430    .end_io = mirror_end_io,
1431    .presuspend = mirror_presuspend,
1432    .postsuspend = mirror_postsuspend,
1433    .resume = mirror_resume,
1434    .status = mirror_status,
1435    .iterate_devices = mirror_iterate_devices,
1436};
1437
1438static int __init dm_mirror_init(void)
1439{
1440    int r;
1441
1442    _dm_raid1_read_record_cache = KMEM_CACHE(dm_raid1_read_record, 0);
1443    if (!_dm_raid1_read_record_cache) {
1444        DMERR("Can't allocate dm_raid1_read_record cache");
1445        r = -ENOMEM;
1446        goto bad_cache;
1447    }
1448
1449    r = dm_register_target(&mirror_target);
1450    if (r < 0) {
1451        DMERR("Failed to register mirror target");
1452        goto bad_target;
1453    }
1454
1455    return 0;
1456
1457bad_target:
1458    kmem_cache_destroy(_dm_raid1_read_record_cache);
1459bad_cache:
1460    return r;
1461}
1462
1463static void __exit dm_mirror_exit(void)
1464{
1465    dm_unregister_target(&mirror_target);
1466    kmem_cache_destroy(_dm_raid1_read_record_cache);
1467}
1468
1469/* Module hooks */
1470module_init(dm_mirror_init);
1471module_exit(dm_mirror_exit);
1472
1473MODULE_DESCRIPTION(DM_NAME " mirror target");
1474MODULE_AUTHOR("Joe Thornber");
1475MODULE_LICENSE("GPL");
1476

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