29 static const char dm_snapshot_merge_target_name[] = "snapshot-merge";
66 	 * You can't use a snapshot if this is 0 (e.g. if full).
67 	 * A snapshot-merge target never clears this.
72 	 * The snapshot overflowed because of a write to the snapshot device.
73 	 * We don't have to invalidate the snapshot in this case, but we need
133 	 *	=> use the origin; forget about the snapshot.
214 	/* Pointer back to snapshot context */
438  * snap_src - a snapshot suitable for use as a source of exception handover
439  * snap_dest - a snapshot capable of receiving exception handover.
440  * snap_merge - an existing snapshot-merge target linked to the same origin.
441  *   There can be at most one snapshot-merge target. The parameter is optional.
444  *   0: NULL, NULL  - first new snapshot
445  *   1: snap_src, NULL - normal snapshot
488  * On success, returns 1 if this snapshot is a handover destination,
496 	/* Does snapshot need exceptions handed over to it? */  in __validate_exception_handover()
500 		snap->ti->error = "Snapshot cow pairing for exception table handover failed";  in __validate_exception_handover()
512 	 * Non-snapshot-merge handover?  in __validate_exception_handover()
518 	 * Do not allow more than one merging snapshot.  in __validate_exception_handover()
521 		snap->ti->error = "A snapshot is already merging.";  in __validate_exception_handover()
527 		snap->ti->error = "Snapshot exception store does not support snapshot-merge.";  in __validate_exception_handover()
546  * Make a note of the snapshot and its origin so we can look it
549  * Also validate snapshot exception store handovers.
594  * Move snapshot to correct place in list according to chunk size.
1049 		DMERR("Snapshot is invalid: can't merge");  in snapshot_merge_next_chunks()
1227  * Construct a snapshot mapping:
1253 		ti->error = "Cannot allocate private snapshot structure";  in snapshot_ctr()
1351 	/* Add snapshot to the list of snapshots for this origin */  in snapshot_ctr()
1355 		ti->error = "Snapshot origin struct allocation failed";  in snapshot_ctr()
1376 		ti->error = "Failed to read snapshot metadata";  in snapshot_ctr()
1380 		DMWARN("Snapshot is marked invalid.");  in snapshot_ctr()
1435 	 * Swap all snapshot context information between the two instances.  in __handover_exceptions()
1474 		DMERR("Cancelling snapshot handover.");  in snapshot_dtr()
1481 	/* Prevent further origin writes from using this snapshot. */  in snapshot_dtr()
1615 		DMERR("Invalidating snapshot: Error reading/writing.");  in __invalidate_snapshot()
1617 		DMERR("Invalidating snapshot: Unable to allocate exception.");  in __invalidate_snapshot()
1648 		/* Read/write error - snapshot is unusable */  in pending_complete()
1678 	 * subsequent snapshot reads to this chunk will be redirected to the  in pending_complete()
1680 	 * as the pending exception exists, neither origin writes nor snapshot  in pending_complete()
1876  * Looks to see if this snapshot already has a pending exception
1981 			 * snapshot exceptions via do_origin; doing so would  in snapshot_map()
1989 		/* discard to snapshot (target_bio_nr == 0) zeroes exceptions */  in snapshot_map()
2018 	 * Write to snapshot - higher level takes care of RW/RO  in snapshot_map()
2046 						DMERR("Snapshot overflowed: Unable to allocate exception.");  in snapshot_map()
2096  * A snapshot-merge target behaves like a combination of a snapshot
2097  * target and a snapshot-origin target.  It only generates new
2202 			DMERR("Unable to resume snapshot source until handover completes.");  in snapshot_preresume()
2205 			DMERR("Unable to perform snapshot handover until source is suspended.");  in snapshot_preresume()
2294 	 * Handover exceptions from existing snapshot.  in snapshot_merge_resume()
2299 	 * snapshot-merge acts as an origin, so set ti->max_io_len  in snapshot_merge_resume()
2440 		 * Don't make new exceptions in a merging snapshot  in __origin_write()
2446 		/* Nothing to do if writing beyond end of snapshot */  in __origin_write()
2468 			 * remapped in this snapshot and trigger an exception  in __origin_write()
2574  * The chunk size of the merging snapshot may be larger than the chunk
2575  * size of some other snapshot so we may need to reallocate multiple
2733 	.name    = "snapshot-origin",
2746 	.name    = "snapshot",
2853 MODULE_DESCRIPTION(DM_NAME " snapshot target");
2856 MODULE_ALIAS("dm-snapshot-origin");
2857 MODULE_ALIAS("dm-snapshot-merge");