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authorJonathan Brassow <jbrassow@redhat.com>2008-02-07 21:11:29 -0500
committerAlasdair G Kergon <agk@redhat.com>2008-02-07 21:11:29 -0500
commit72f4b314100bae85c75d8e4c6fec621ab44e777d (patch)
tree6dc5e860e8a4acab2e047f31391d0c8fdf366ff7 /drivers/md
parentd74f81f8adc504a23be3babf347b9f69e9389924 (diff)
dm raid1: handle write failures
This patch gives mirror the ability to handle device failures during normal write operations. The 'write_callback' function is called when a write completes. If all the writes failed or succeeded, we report failure or success respectively. If some of the writes failed, we call fail_mirror; which increments the error count for the device, notes the type of error encountered (DM_RAID1_WRITE_ERROR), and selects a new primary (if necessary). Note that the primary device can never change while the mirror is not in-sync (IOW, while recovery is happening.) This means that the scenario where a failed write changes the primary and gives recovery_complete a chance to misread the primary never happens. The fact that the primary can change has necessitated the change to the default_mirror field. We need to protect against reading garbage while the primary changes. We then add the bio to a new list in the mirror set, 'failures'. For every bio in the 'failures' list, we call a new function, '__bio_mark_nosync', where we mark the region 'not-in-sync' in the log and properly set the region state as, RH_NOSYNC. Userspace must also be notified of the failure. This is done by 'raising an event' (dm_table_event()). If fail_mirror is called in process context the event can be raised right away. If in interrupt context, the event is deferred to the kmirrord thread - which raises the event if 'event_waiting' is set. Backwards compatibility is maintained by ignoring errors if the DM_FEATURES_HANDLE_ERRORS flag is not present. Signed-off-by: Jonathan Brassow <jbrassow@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Diffstat (limited to 'drivers/md')
-rw-r--r--drivers/md/dm-raid1.c250
1 files changed, 224 insertions, 26 deletions
diff --git a/drivers/md/dm-raid1.c b/drivers/md/dm-raid1.c
index 31123d4a6b9c..4e1e04dbc4ab 100644
--- a/drivers/md/dm-raid1.c
+++ b/drivers/md/dm-raid1.c
@@ -20,6 +20,7 @@
20#include <linux/vmalloc.h> 20#include <linux/vmalloc.h>
21#include <linux/workqueue.h> 21#include <linux/workqueue.h>
22#include <linux/log2.h> 22#include <linux/log2.h>
23#include <linux/hardirq.h>
23 24
24#define DM_MSG_PREFIX "raid1" 25#define DM_MSG_PREFIX "raid1"
25#define DM_IO_PAGES 64 26#define DM_IO_PAGES 64
@@ -113,9 +114,16 @@ struct region {
113/*----------------------------------------------------------------- 114/*-----------------------------------------------------------------
114 * Mirror set structures. 115 * Mirror set structures.
115 *---------------------------------------------------------------*/ 116 *---------------------------------------------------------------*/
117enum dm_raid1_error {
118 DM_RAID1_WRITE_ERROR,
119 DM_RAID1_SYNC_ERROR,
120 DM_RAID1_READ_ERROR
121};
122
116struct mirror { 123struct mirror {
117 struct mirror_set *ms; 124 struct mirror_set *ms;
118 atomic_t error_count; 125 atomic_t error_count;
126 uint32_t error_type;
119 struct dm_dev *dev; 127 struct dm_dev *dev;
120 sector_t offset; 128 sector_t offset;
121}; 129};
@@ -127,9 +135,10 @@ struct mirror_set {
127 struct kcopyd_client *kcopyd_client; 135 struct kcopyd_client *kcopyd_client;
128 uint64_t features; 136 uint64_t features;
129 137
130 spinlock_t lock; /* protects the next two lists */ 138 spinlock_t lock; /* protects the lists */
131 struct bio_list reads; 139 struct bio_list reads;
132 struct bio_list writes; 140 struct bio_list writes;
141 struct bio_list failures;
133 142
134 struct dm_io_client *io_client; 143 struct dm_io_client *io_client;
135 144
@@ -138,10 +147,11 @@ struct mirror_set {
138 int in_sync; 147 int in_sync;
139 int log_failure; 148 int log_failure;
140 149
141 struct mirror *default_mirror; /* Default mirror */ 150 atomic_t default_mirror; /* Default mirror */
142 151
143 struct workqueue_struct *kmirrord_wq; 152 struct workqueue_struct *kmirrord_wq;
144 struct work_struct kmirrord_work; 153 struct work_struct kmirrord_work;
154 struct work_struct trigger_event;
145 155
146 unsigned int nr_mirrors; 156 unsigned int nr_mirrors;
147 struct mirror mirror[0]; 157 struct mirror mirror[0];
@@ -646,6 +656,77 @@ static void bio_set_ms(struct bio *bio, struct mirror_set *ms)
646 bio->bi_next = (struct bio *) ms; 656 bio->bi_next = (struct bio *) ms;
647} 657}
648 658
659static struct mirror *get_default_mirror(struct mirror_set *ms)
660{
661 return &ms->mirror[atomic_read(&ms->default_mirror)];
662}
663
664static void set_default_mirror(struct mirror *m)
665{
666 struct mirror_set *ms = m->ms;
667 struct mirror *m0 = &(ms->mirror[0]);
668
669 atomic_set(&ms->default_mirror, m - m0);
670}
671
672/* fail_mirror
673 * @m: mirror device to fail
674 * @error_type: one of the enum's, DM_RAID1_*_ERROR
675 *
676 * If errors are being handled, record the type of
677 * error encountered for this device. If this type
678 * of error has already been recorded, we can return;
679 * otherwise, we must signal userspace by triggering
680 * an event. Additionally, if the device is the
681 * primary device, we must choose a new primary, but
682 * only if the mirror is in-sync.
683 *
684 * This function must not block.
685 */
686static void fail_mirror(struct mirror *m, enum dm_raid1_error error_type)
687{
688 struct mirror_set *ms = m->ms;
689 struct mirror *new;
690
691 if (!errors_handled(ms))
692 return;
693
694 /*
695 * error_count is used for nothing more than a
696 * simple way to tell if a device has encountered
697 * errors.
698 */
699 atomic_inc(&m->error_count);
700
701 if (test_and_set_bit(error_type, &m->error_type))
702 return;
703
704 if (m != get_default_mirror(ms))
705 goto out;
706
707 if (!ms->in_sync) {
708 /*
709 * Better to issue requests to same failing device
710 * than to risk returning corrupt data.
711 */
712 DMERR("Primary mirror (%s) failed while out-of-sync: "
713 "Reads may fail.", m->dev->name);
714 goto out;
715 }
716
717 for (new = ms->mirror; new < ms->mirror + ms->nr_mirrors; new++)
718 if (!atomic_read(&new->error_count)) {
719 set_default_mirror(new);
720 break;
721 }
722
723 if (unlikely(new == ms->mirror + ms->nr_mirrors))
724 DMWARN("All sides of mirror have failed.");
725
726out:
727 schedule_work(&ms->trigger_event);
728}
729
649/*----------------------------------------------------------------- 730/*-----------------------------------------------------------------
650 * Recovery. 731 * Recovery.
651 * 732 *
@@ -678,7 +759,7 @@ static int recover(struct mirror_set *ms, struct region *reg)
678 unsigned long flags = 0; 759 unsigned long flags = 0;
679 760
680 /* fill in the source */ 761 /* fill in the source */
681 m = ms->default_mirror; 762 m = get_default_mirror(ms);
682 from.bdev = m->dev->bdev; 763 from.bdev = m->dev->bdev;
683 from.sector = m->offset + region_to_sector(reg->rh, reg->key); 764 from.sector = m->offset + region_to_sector(reg->rh, reg->key);
684 if (reg->key == (ms->nr_regions - 1)) { 765 if (reg->key == (ms->nr_regions - 1)) {
@@ -694,7 +775,7 @@ static int recover(struct mirror_set *ms, struct region *reg)
694 775
695 /* fill in the destinations */ 776 /* fill in the destinations */
696 for (i = 0, dest = to; i < ms->nr_mirrors; i++) { 777 for (i = 0, dest = to; i < ms->nr_mirrors; i++) {
697 if (&ms->mirror[i] == ms->default_mirror) 778 if (&ms->mirror[i] == get_default_mirror(ms))
698 continue; 779 continue;
699 780
700 m = ms->mirror + i; 781 m = ms->mirror + i;
@@ -749,7 +830,7 @@ static void do_recovery(struct mirror_set *ms)
749static struct mirror *choose_mirror(struct mirror_set *ms, sector_t sector) 830static struct mirror *choose_mirror(struct mirror_set *ms, sector_t sector)
750{ 831{
751 /* FIXME: add read balancing */ 832 /* FIXME: add read balancing */
752 return ms->default_mirror; 833 return get_default_mirror(ms);
753} 834}
754 835
755/* 836/*
@@ -776,7 +857,7 @@ static void do_reads(struct mirror_set *ms, struct bio_list *reads)
776 if (rh_in_sync(&ms->rh, region, 1)) 857 if (rh_in_sync(&ms->rh, region, 1))
777 m = choose_mirror(ms, bio->bi_sector); 858 m = choose_mirror(ms, bio->bi_sector);
778 else 859 else
779 m = ms->default_mirror; 860 m = get_default_mirror(ms);
780 861
781 map_bio(ms, m, bio); 862 map_bio(ms, m, bio);
782 generic_make_request(bio); 863 generic_make_request(bio);
@@ -793,12 +874,67 @@ static void do_reads(struct mirror_set *ms, struct bio_list *reads)
793 * RECOVERING: delay the io until recovery completes 874 * RECOVERING: delay the io until recovery completes
794 * NOSYNC: increment pending, just write to the default mirror 875 * NOSYNC: increment pending, just write to the default mirror
795 *---------------------------------------------------------------*/ 876 *---------------------------------------------------------------*/
877
878/* __bio_mark_nosync
879 * @ms
880 * @bio
881 * @done
882 * @error
883 *
884 * The bio was written on some mirror(s) but failed on other mirror(s).
885 * We can successfully endio the bio but should avoid the region being
886 * marked clean by setting the state RH_NOSYNC.
887 *
888 * This function is _not_ safe in interrupt context!
889 */
890static void __bio_mark_nosync(struct mirror_set *ms,
891 struct bio *bio, unsigned done, int error)
892{
893 unsigned long flags;
894 struct region_hash *rh = &ms->rh;
895 struct dirty_log *log = ms->rh.log;
896 struct region *reg;
897 region_t region = bio_to_region(rh, bio);
898 int recovering = 0;
899
900 /* We must inform the log that the sync count has changed. */
901 log->type->set_region_sync(log, region, 0);
902 ms->in_sync = 0;
903
904 read_lock(&rh->hash_lock);
905 reg = __rh_find(rh, region);
906 read_unlock(&rh->hash_lock);
907
908 /* region hash entry should exist because write was in-flight */
909 BUG_ON(!reg);
910 BUG_ON(!list_empty(&reg->list));
911
912 spin_lock_irqsave(&rh->region_lock, flags);
913 /*
914 * Possible cases:
915 * 1) RH_DIRTY
916 * 2) RH_NOSYNC: was dirty, other preceeding writes failed
917 * 3) RH_RECOVERING: flushing pending writes
918 * Either case, the region should have not been connected to list.
919 */
920 recovering = (reg->state == RH_RECOVERING);
921 reg->state = RH_NOSYNC;
922 BUG_ON(!list_empty(&reg->list));
923 spin_unlock_irqrestore(&rh->region_lock, flags);
924
925 bio_endio(bio, error);
926 if (recovering)
927 complete_resync_work(reg, 0);
928}
929
796static void write_callback(unsigned long error, void *context) 930static void write_callback(unsigned long error, void *context)
797{ 931{
798 unsigned int i; 932 unsigned i, ret = 0;
799 int uptodate = 1;
800 struct bio *bio = (struct bio *) context; 933 struct bio *bio = (struct bio *) context;
801 struct mirror_set *ms; 934 struct mirror_set *ms;
935 int uptodate = 0;
936 int should_wake = 0;
937 unsigned long flags;
802 938
803 ms = bio_get_ms(bio); 939 ms = bio_get_ms(bio);
804 bio_set_ms(bio, NULL); 940 bio_set_ms(bio, NULL);
@@ -809,20 +945,36 @@ static void write_callback(unsigned long error, void *context)
809 * This way we handle both writes to SYNC and NOSYNC 945 * This way we handle both writes to SYNC and NOSYNC
810 * regions with the same code. 946 * regions with the same code.
811 */ 947 */
948 if (likely(!error))
949 goto out;
812 950
813 if (error) { 951 for (i = 0; i < ms->nr_mirrors; i++)
952 if (test_bit(i, &error))
953 fail_mirror(ms->mirror + i, DM_RAID1_WRITE_ERROR);
954 else
955 uptodate = 1;
956
957 if (unlikely(!uptodate)) {
958 DMERR("All replicated volumes dead, failing I/O");
959 /* None of the writes succeeded, fail the I/O. */
960 ret = -EIO;
961 } else if (errors_handled(ms)) {
814 /* 962 /*
815 * only error the io if all mirrors failed. 963 * Need to raise event. Since raising
816 * FIXME: bogus 964 * events can block, we need to do it in
965 * the main thread.
817 */ 966 */
818 uptodate = 0; 967 spin_lock_irqsave(&ms->lock, flags);
819 for (i = 0; i < ms->nr_mirrors; i++) 968 if (!ms->failures.head)
820 if (!test_bit(i, &error)) { 969 should_wake = 1;
821 uptodate = 1; 970 bio_list_add(&ms->failures, bio);
822 break; 971 spin_unlock_irqrestore(&ms->lock, flags);
823 } 972 if (should_wake)
973 wake(ms);
974 return;
824 } 975 }
825 bio_endio(bio, 0); 976out:
977 bio_endio(bio, ret);
826} 978}
827 979
828static void do_write(struct mirror_set *ms, struct bio *bio) 980static void do_write(struct mirror_set *ms, struct bio *bio)
@@ -910,33 +1062,75 @@ static void do_writes(struct mirror_set *ms, struct bio_list *writes)
910 rh_delay(&ms->rh, bio); 1062 rh_delay(&ms->rh, bio);
911 1063
912 while ((bio = bio_list_pop(&nosync))) { 1064 while ((bio = bio_list_pop(&nosync))) {
913 map_bio(ms, ms->default_mirror, bio); 1065 map_bio(ms, get_default_mirror(ms), bio);
914 generic_make_request(bio); 1066 generic_make_request(bio);
915 } 1067 }
916} 1068}
917 1069
1070static void do_failures(struct mirror_set *ms, struct bio_list *failures)
1071{
1072 struct bio *bio;
1073
1074 if (!failures->head)
1075 return;
1076
1077 while ((bio = bio_list_pop(failures)))
1078 __bio_mark_nosync(ms, bio, bio->bi_size, 0);
1079}
1080
1081static void trigger_event(struct work_struct *work)
1082{
1083 struct mirror_set *ms =
1084 container_of(work, struct mirror_set, trigger_event);
1085
1086 dm_table_event(ms->ti->table);
1087}
1088
918/*----------------------------------------------------------------- 1089/*-----------------------------------------------------------------
919 * kmirrord 1090 * kmirrord
920 *---------------------------------------------------------------*/ 1091 *---------------------------------------------------------------*/
921static void do_mirror(struct work_struct *work) 1092static int _do_mirror(struct work_struct *work)
922{ 1093{
923 struct mirror_set *ms =container_of(work, struct mirror_set, 1094 struct mirror_set *ms =container_of(work, struct mirror_set,
924 kmirrord_work); 1095 kmirrord_work);
925 struct bio_list reads, writes; 1096 struct bio_list reads, writes, failures;
1097 unsigned long flags;
926 1098
927 spin_lock(&ms->lock); 1099 spin_lock_irqsave(&ms->lock, flags);
928 reads = ms->reads; 1100 reads = ms->reads;
929 writes = ms->writes; 1101 writes = ms->writes;
1102 failures = ms->failures;
930 bio_list_init(&ms->reads); 1103 bio_list_init(&ms->reads);
931 bio_list_init(&ms->writes); 1104 bio_list_init(&ms->writes);
932 spin_unlock(&ms->lock); 1105 bio_list_init(&ms->failures);
1106 spin_unlock_irqrestore(&ms->lock, flags);
933 1107
934 rh_update_states(&ms->rh); 1108 rh_update_states(&ms->rh);
935 do_recovery(ms); 1109 do_recovery(ms);
936 do_reads(ms, &reads); 1110 do_reads(ms, &reads);
937 do_writes(ms, &writes); 1111 do_writes(ms, &writes);
1112 do_failures(ms, &failures);
1113
1114 return (ms->failures.head) ? 1 : 0;
1115}
1116
1117static void do_mirror(struct work_struct *work)
1118{
1119 /*
1120 * If _do_mirror returns 1, we give it
1121 * another shot. This helps for cases like
1122 * 'suspend' where we call flush_workqueue
1123 * and expect all work to be finished. If
1124 * a failure happens during a suspend, we
1125 * couldn't issue a 'wake' because it would
1126 * not be honored. Therefore, we return '1'
1127 * from _do_mirror, and retry here.
1128 */
1129 while (_do_mirror(work))
1130 schedule();
938} 1131}
939 1132
1133
940/*----------------------------------------------------------------- 1134/*-----------------------------------------------------------------
941 * Target functions 1135 * Target functions
942 *---------------------------------------------------------------*/ 1136 *---------------------------------------------------------------*/
@@ -965,7 +1159,7 @@ static struct mirror_set *alloc_context(unsigned int nr_mirrors,
965 ms->nr_mirrors = nr_mirrors; 1159 ms->nr_mirrors = nr_mirrors;
966 ms->nr_regions = dm_sector_div_up(ti->len, region_size); 1160 ms->nr_regions = dm_sector_div_up(ti->len, region_size);
967 ms->in_sync = 0; 1161 ms->in_sync = 0;
968 ms->default_mirror = &ms->mirror[DEFAULT_MIRROR]; 1162 atomic_set(&ms->default_mirror, DEFAULT_MIRROR);
969 1163
970 ms->io_client = dm_io_client_create(DM_IO_PAGES); 1164 ms->io_client = dm_io_client_create(DM_IO_PAGES);
971 if (IS_ERR(ms->io_client)) { 1165 if (IS_ERR(ms->io_client)) {
@@ -1019,6 +1213,8 @@ static int get_mirror(struct mirror_set *ms, struct dm_target *ti,
1019 } 1213 }
1020 1214
1021 ms->mirror[mirror].ms = ms; 1215 ms->mirror[mirror].ms = ms;
1216 atomic_set(&(ms->mirror[mirror].error_count), 0);
1217 ms->mirror[mirror].error_type = 0;
1022 ms->mirror[mirror].offset = offset; 1218 ms->mirror[mirror].offset = offset;
1023 1219
1024 return 0; 1220 return 0;
@@ -1171,6 +1367,7 @@ static int mirror_ctr(struct dm_target *ti, unsigned int argc, char **argv)
1171 goto err_free_context; 1367 goto err_free_context;
1172 } 1368 }
1173 INIT_WORK(&ms->kmirrord_work, do_mirror); 1369 INIT_WORK(&ms->kmirrord_work, do_mirror);
1370 INIT_WORK(&ms->trigger_event, trigger_event);
1174 1371
1175 r = parse_features(ms, argc, argv, &args_used); 1372 r = parse_features(ms, argc, argv, &args_used);
1176 if (r) 1373 if (r)
@@ -1220,14 +1417,15 @@ static void mirror_dtr(struct dm_target *ti)
1220 1417
1221static void queue_bio(struct mirror_set *ms, struct bio *bio, int rw) 1418static void queue_bio(struct mirror_set *ms, struct bio *bio, int rw)
1222{ 1419{
1420 unsigned long flags;
1223 int should_wake = 0; 1421 int should_wake = 0;
1224 struct bio_list *bl; 1422 struct bio_list *bl;
1225 1423
1226 bl = (rw == WRITE) ? &ms->writes : &ms->reads; 1424 bl = (rw == WRITE) ? &ms->writes : &ms->reads;
1227 spin_lock(&ms->lock); 1425 spin_lock_irqsave(&ms->lock, flags);
1228 should_wake = !(bl->head); 1426 should_wake = !(bl->head);
1229 bio_list_add(bl, bio); 1427 bio_list_add(bl, bio);
1230 spin_unlock(&ms->lock); 1428 spin_unlock_irqrestore(&ms->lock, flags);
1231 1429
1232 if (should_wake) 1430 if (should_wake)
1233 wake(ms); 1431 wake(ms);