dm snapshot: avoid allocating exceptions in merge

The snapshot-merge target should not allocate new exceptions because the
intent is to merge all of its exceptions as quickly and safely as
possible.

This patch introduces the snapshot-merge mapping function and updates
__origin_write() so that it doesn't allocate exceptions on any snapshots
that are being merged.

If a write request to a merging snapshot device is to be dispatched
directly to the origin (because the chunk is not remapped or was already
merged), snapshot_merge_map() must make exceptions in other snapshots so
calls do_origin().

Signed-off-by: Mikulas Patocka <[email protected]>
Signed-off-by: Mike Snitzer <[email protected]>
Signed-off-by: Alasdair G Kergon <[email protected]>

0 files changed, 0 insertions, 0 deletions