dm snapshot: report merge failure in status
Set 'merge_failed' flag if a snapshot fails to merge. Update
snapshot_status() to report "Merge failed" if 'merge_failed' is set.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index bb4b733..4c80e82 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -71,7 +71,10 @@
/* List of snapshots per Origin */
struct list_head list;
- /* You can't use a snapshot if this is 0 (e.g. if full) */
+ /*
+ * You can't use a snapshot if this is 0 (e.g. if full).
+ * A snapshot-merge target never clears this.
+ */
int valid;
/* Origin writes don't trigger exceptions until this is set */
@@ -107,6 +110,21 @@
spinlock_t tracked_chunk_lock;
struct hlist_head tracked_chunk_hash[DM_TRACKED_CHUNK_HASH_SIZE];
+ /*
+ * The merge operation failed if this flag is set.
+ * Failure modes are handled as follows:
+ * - I/O error reading the header
+ * => don't load the target; abort.
+ * - Header does not have "valid" flag set
+ * => use the origin; forget about the snapshot.
+ * - I/O error when reading exceptions
+ * => don't load the target; abort.
+ * (We can't use the intermediate origin state.)
+ * - I/O error while merging
+ * => stop merging; set merge_failed; process I/O normally.
+ */
+ int merge_failed;
+
/* Wait for events based on state_bits */
unsigned long state_bits;
@@ -900,9 +918,13 @@
linear_chunks = s->store->type->prepare_merge(s->store, &old_chunk,
&new_chunk);
if (linear_chunks <= 0) {
- if (linear_chunks < 0)
+ if (linear_chunks < 0) {
DMERR("Read error in exception store: "
"shutting down merge");
+ down_write(&s->lock);
+ s->merge_failed = 1;
+ up_write(&s->lock);
+ }
goto shut;
}
@@ -988,6 +1010,7 @@
shut:
down_write(&s->lock);
+ s->merge_failed = 1;
b = __release_queued_bios_after_merge(s);
up_write(&s->lock);
error_bios(b);
@@ -1090,6 +1113,7 @@
INIT_LIST_HEAD(&s->list);
spin_lock_init(&s->pe_lock);
s->state_bits = 0;
+ s->merge_failed = 0;
s->first_merging_chunk = 0;
s->num_merging_chunks = 0;
bio_list_init(&s->bios_queued_during_merge);
@@ -1835,6 +1859,8 @@
if (!snap->valid)
DMEMIT("Invalid");
+ else if (snap->merge_failed)
+ DMEMIT("Merge failed");
else {
if (snap->store->type->usage) {
sector_t total_sectors, sectors_allocated,