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dm raid1: handle resync failures

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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>
This commit is contained in:
Jonathan Brassow 2007-07-12 17:29:04 +01:00 committed by Linus Torvalds
parent d0d444c7d4
commit f44db678ed
1 changed files with 41 additions and 3 deletions
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44
drivers/md/dm-raid1.c
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@ -24,6 +24,7 @@
#define DM_IO_PAGES 64
#define DM_RAID1_HANDLE_ERRORS 0x01
#define errors_handled(p) ((p)->features & DM_RAID1_HANDLE_ERRORS)
static DECLARE_WAIT_QUEUE_HEAD(_kmirrord_recovery_stopped);
@ -85,6 +86,7 @@ struct region_hash {
struct list_head clean_regions;
struct list_head quiesced_regions;
struct list_head recovered_regions;
struct list_head failed_recovered_regions;
};
enum {
@ -204,6 +206,7 @@ static int rh_init(struct region_hash *rh, struct mirror_set *ms,
INIT_LIST_HEAD(&rh->clean_regions);
INIT_LIST_HEAD(&rh->quiesced_regions);
INIT_LIST_HEAD(&rh->recovered_regions);
INIT_LIST_HEAD(&rh->failed_recovered_regions);
rh->region_pool = mempool_create_kmalloc_pool(MIN_REGIONS,
sizeof(struct region));
@ -368,6 +371,7 @@ static void rh_update_states(struct region_hash *rh)
LIST_HEAD(clean);
LIST_HEAD(recovered);
LIST_HEAD(failed_recovered);
/*
* Quickly grab the lists.
@ -389,6 +393,15 @@ static void rh_update_states(struct region_hash *rh)
list_for_each_entry (reg, &recovered, list)
list_del(&reg->hash_list);
}
if (!list_empty(&rh->failed_recovered_regions)) {
list_splice(&rh->failed_recovered_regions, &failed_recovered);
INIT_LIST_HEAD(&rh->failed_recovered_regions);
list_for_each_entry(reg, &failed_recovered, list)
list_del(&reg->hash_list);
}
spin_unlock(&rh->region_lock);
write_unlock_irq(&rh->hash_lock);
@ -403,6 +416,11 @@ static void rh_update_states(struct region_hash *rh)
mempool_free(reg, rh->region_pool);
}
list_for_each_entry_safe(reg, next, &failed_recovered, list) {
complete_resync_work(reg, errors_handled(rh->ms) ? 0 : 1);
mempool_free(reg, rh->region_pool);
}
list_for_each_entry_safe(reg, next, &clean, list) {
rh->log->type->clear_region(rh->log, reg->key);
mempool_free(reg, rh->region_pool);
@ -555,13 +573,17 @@ static struct region *rh_recovery_start(struct region_hash *rh)
return reg;
}
/* FIXME: success ignored for now */
static void rh_recovery_end(struct region *reg, int success)
{
struct region_hash *rh = reg->rh;
spin_lock_irq(&rh->region_lock);
list_add(&reg->list, &reg->rh->recovered_regions);
if (success)
list_add(&reg->list, &reg->rh->recovered_regions);
else {
reg->state = RH_NOSYNC;
list_add(&reg->list, &reg->rh->failed_recovered_regions);
}
spin_unlock_irq(&rh->region_lock);
wake(rh->ms);
@ -633,7 +655,14 @@ static void recovery_complete(int read_err, unsigned int write_err,
{
struct region *reg = (struct region *) context;
/* FIXME: better error handling */
if (read_err)
/* Read error means the failure of default mirror. */
DMERR_LIMIT("Unable to read primary mirror during recovery");
if (write_err)
DMERR_LIMIT("Write error during recovery (error = 0x%x)",
write_err);
rh_recovery_end(reg, !(read_err || write_err));
}
@ -1145,6 +1174,15 @@ static int mirror_ctr(struct dm_target *ti, unsigned int argc, char **argv)
argv += args_used;
argc -= args_used;
/*
* Any read-balancing addition depends on the
* DM_RAID1_HANDLE_ERRORS flag being present.
* This is because the decision to balance depends
* on the sync state of a region. If the above
* flag is not present, we ignore errors; and
* the sync state may be inaccurate.
*/
if (argc) {
ti->error = "Too many mirror arguments";
free_context(ms, ti, ms->nr_mirrors);