dm raid1: handle resync failures
Device-mapper mirroring currently takes a best effort approach to recovery - failures during mirror synchronization are completely ignored. This means that regions are marked 'in-sync' and 'clean' and removed from the hash list. Future reads and writes that query the region will incorrectly interpret the region as in-sync. This patch handles failures during the recovery process. If a failure occurs, the region is marked as 'not-in-sync' (aka RH_NOSYNC) and added to a new list 'failed_recovered_regions'. Regions on the 'failed_recovered_regions' list are not marked as 'clean' upon removal from the list. Furthermore, if the DM_RAID1_HANDLE_ERRORS flag is set, the region is marked as 'not-in-sync'. This action prevents any future read-balancing from choosing an invalid device because of the 'not-in-sync' status. If "handle_errors" is not specified when creating a mirror (leaving the DM_RAID1_HANDLE_ERRORS flag unset), failures will be ignored exactly as they would be without this patch. This is to preserve backwards compatibility with user-space tools, such as 'pvmove'. However, since future read-balancing policies will rely on the correct sync status of a region, a user must choose "handle_errors" when using read-balancing. Signed-off-by: Jonathan Brassow <jbrassow@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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1 changed files with 41 additions and 3 deletions
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@ -24,6 +24,7 @@
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#define DM_IO_PAGES 64
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#define DM_RAID1_HANDLE_ERRORS 0x01
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#define errors_handled(p) ((p)->features & DM_RAID1_HANDLE_ERRORS)
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static DECLARE_WAIT_QUEUE_HEAD(_kmirrord_recovery_stopped);
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@ -85,6 +86,7 @@ struct region_hash {
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struct list_head clean_regions;
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struct list_head quiesced_regions;
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struct list_head recovered_regions;
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struct list_head failed_recovered_regions;
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};
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enum {
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@ -204,6 +206,7 @@ static int rh_init(struct region_hash *rh, struct mirror_set *ms,
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INIT_LIST_HEAD(&rh->clean_regions);
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INIT_LIST_HEAD(&rh->quiesced_regions);
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INIT_LIST_HEAD(&rh->recovered_regions);
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INIT_LIST_HEAD(&rh->failed_recovered_regions);
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rh->region_pool = mempool_create_kmalloc_pool(MIN_REGIONS,
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sizeof(struct region));
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@ -368,6 +371,7 @@ static void rh_update_states(struct region_hash *rh)
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LIST_HEAD(clean);
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LIST_HEAD(recovered);
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LIST_HEAD(failed_recovered);
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/*
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* Quickly grab the lists.
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@ -389,6 +393,15 @@ static void rh_update_states(struct region_hash *rh)
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list_for_each_entry (reg, &recovered, list)
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list_del(®->hash_list);
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}
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if (!list_empty(&rh->failed_recovered_regions)) {
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list_splice(&rh->failed_recovered_regions, &failed_recovered);
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INIT_LIST_HEAD(&rh->failed_recovered_regions);
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list_for_each_entry(reg, &failed_recovered, list)
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list_del(®->hash_list);
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}
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spin_unlock(&rh->region_lock);
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write_unlock_irq(&rh->hash_lock);
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@ -403,6 +416,11 @@ static void rh_update_states(struct region_hash *rh)
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mempool_free(reg, rh->region_pool);
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}
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list_for_each_entry_safe(reg, next, &failed_recovered, list) {
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complete_resync_work(reg, errors_handled(rh->ms) ? 0 : 1);
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mempool_free(reg, rh->region_pool);
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}
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list_for_each_entry_safe(reg, next, &clean, list) {
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rh->log->type->clear_region(rh->log, reg->key);
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mempool_free(reg, rh->region_pool);
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@ -555,13 +573,17 @@ static struct region *rh_recovery_start(struct region_hash *rh)
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return reg;
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}
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/* FIXME: success ignored for now */
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static void rh_recovery_end(struct region *reg, int success)
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{
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struct region_hash *rh = reg->rh;
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spin_lock_irq(&rh->region_lock);
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list_add(®->list, ®->rh->recovered_regions);
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if (success)
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list_add(®->list, ®->rh->recovered_regions);
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else {
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reg->state = RH_NOSYNC;
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list_add(®->list, ®->rh->failed_recovered_regions);
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}
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spin_unlock_irq(&rh->region_lock);
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wake(rh->ms);
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@ -633,7 +655,14 @@ static void recovery_complete(int read_err, unsigned int write_err,
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{
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struct region *reg = (struct region *) context;
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/* FIXME: better error handling */
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if (read_err)
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/* Read error means the failure of default mirror. */
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DMERR_LIMIT("Unable to read primary mirror during recovery");
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if (write_err)
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DMERR_LIMIT("Write error during recovery (error = 0x%x)",
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write_err);
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rh_recovery_end(reg, !(read_err || write_err));
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}
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@ -1145,6 +1174,15 @@ static int mirror_ctr(struct dm_target *ti, unsigned int argc, char **argv)
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argv += args_used;
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argc -= args_used;
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/*
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* Any read-balancing addition depends on the
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* DM_RAID1_HANDLE_ERRORS flag being present.
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* This is because the decision to balance depends
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* on the sync state of a region. If the above
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* flag is not present, we ignore errors; and
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* the sync state may be inaccurate.
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*/
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if (argc) {
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ti->error = "Too many mirror arguments";
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free_context(ms, ti, ms->nr_mirrors);
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