From: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Merge target shouldn't allocate new exceptions:
- make new method snapshot_merge_map that don't allocate exceptions.
- modify __origin_write so that it doesn't allocate exceptions in merging
snapshots.
- disallow creating merging snapshots with exception store that doesn't
provide .prepare_merge (e.g. transient)
Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
---
drivers/md/dm-snap.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++++-
1 files changed, 52 insertions(+), 1 deletions(-)
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index 27b2f22..31040f9 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -127,6 +127,11 @@ static int bdev_equal(struct block_device *lhs, struct block_device *rhs)
return lhs == rhs;
}
+static int snapshot_merge_map(struct dm_target *ti, struct bio *bio,
+ union map_info *map_context);
+
+#define is_merge(ti) ((ti)->type->map == snapshot_merge_map)
+
struct dm_snap_pending_exception {
struct dm_snap_exception e;
@@ -655,6 +660,12 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
argv += args_used;
argc -= args_used;
+ if (is_merge(ti) && !s->store->type->prepare_merge) {
+ ti->error = "Merging snapshot must support snapshot-merge";
+ r = -EINVAL;
+ goto bad_merge_store;
+ }
+
r = dm_get_device(ti, origin_path, 0, ti->len, FMODE_READ, &s->origin);
if (r) {
ti->error = "Cannot get origin device";
@@ -756,6 +767,7 @@ bad_hash_tables:
dm_put_device(ti, s->origin);
bad_origin:
+bad_merge_store:
dm_exception_store_destroy(s->store);
bad_store:
@@ -1198,6 +1210,40 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio,
return r;
}
+static int snapshot_merge_map(struct dm_target *ti, struct bio *bio,
+ union map_info *map_context)
+{
+ struct dm_snap_exception *e;
+ struct dm_snapshot *s = ti->private;
+ int r = DM_MAPIO_REMAPPED;
+ chunk_t chunk;
+
+ chunk = sector_to_chunk(s->store, bio->bi_sector);
+
+ down_read(&s->lock);
+
+ /* Full snapshots are not usable */
+ if (!s->valid) {
+ r = -EIO;
+ goto out_unlock;
+ }
+
+ /* If the block is already remapped - use that */
+ e = lookup_exception(&s->complete, chunk);
+ if (e) {
+ remap_exception(s, e, bio, chunk);
+ goto out_unlock;
+ }
+
+ bio->bi_bdev = s->origin->bdev;
+
+ out_unlock:
+ up_read(&s->lock);
+
+ return r;
+}
+
+
static int snapshot_end_io(struct dm_target *ti, struct bio *bio,
int error, union map_info *map_context)
{
@@ -1305,6 +1351,11 @@ static int __origin_write(struct list_head *snapshots,
/* Do all the snapshots on this origin */
list_for_each_entry (snap, snapshots, list) {
+ /* If the snapshot is merging, don't make new exceptions in it
+ - but in this case no one should be writing to the origin */
+ if (is_merge(snap->ti))
+ continue;
+
down_write(&snap->lock);
/* Only deal with valid and active snapshots */
@@ -1531,7 +1582,7 @@ static struct target_type snapshot_merge_target = {
.module = THIS_MODULE,
.ctr = snapshot_ctr,
.dtr = snapshot_dtr,
- .map = snapshot_map,
+ .map = snapshot_merge_map,
.end_io = snapshot_end_io,
.resume = snapshot_resume,
.status = snapshot_status,
--
1.6.2.5
--
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