[dm-devel] [PATCH 2 of 2] DM Snapshot: dont insert before existing chunk

[Jonathan Brassow]

Patch name: dm-snapshot-dont-insert-before-existing-chunk.patch

Don't insert into hash before an existing chunk.

Most inserts are after an existing extent anyway so this code is used
very rarely.

The snapshot merge code always pulls the chunk from the end of the
range.  Without introducing unnecessary complexity, snapshot merge can't
pull the exception from the middle of a range --- i.e. if you have range
1-10 and you merge chunk 5, you'd have to split the range into two.

Signed-off-by: Mikulas Patocka <mpatocka at redhat.com>
Reviewed-by: Jonathan Brassow <jbrassow at redhat.com>
Reviewed-by: Mike Snitzer <snitzer at redhat.com>

Index: linux-2.6/drivers/md/dm-snap.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-snap.c
+++ linux-2.6/drivers/md/dm-snap.c
@@ -478,16 +478,6 @@ static void insert_completed_exception(s
 			return;
 		}
 
-		/* Insert before an existing chunk? */
-		if (new_e->old_chunk == (e->old_chunk - 1) &&
-		    new_e->new_chunk == (dm_chunk_number(e->new_chunk) - 1)) {
-			dm_consecutive_chunk_count_inc(e);
-			e->old_chunk--;
-			e->new_chunk--;
-			free_exception(new_e);
-			return;
-		}
-
 		if (new_e->old_chunk > e->old_chunk)
 			break;
 	}