[PATCH] device-mapper snapshots: Handle origin extension

Handle writes to a snapshot-origin device that has been extended since the
snapshot was taken.
Signed-off-by: NAlasdair G Kergon <agk@redhat.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

drivers/md/dm-snap.c

@@ -931,6 +931,10 @@ static int __origin_write(struct list_head *snapshots, struct bio *bio)
 		if (!snap->valid)
 			continue;
 
+		/* Nothing to do if writing beyond end of snapshot */
+		if (bio->bi_sector >= dm_table_get_size(snap->table))
+			continue;
+
 		down_write(&snap->lock);
 
 		/*

drivers/md/dm-table.c

@@ -943,6 +943,7 @@ EXPORT_SYMBOL(dm_vcalloc);
 EXPORT_SYMBOL(dm_get_device);
 EXPORT_SYMBOL(dm_put_device);
 EXPORT_SYMBOL(dm_table_event);
+EXPORT_SYMBOL(dm_table_get_size);
 EXPORT_SYMBOL(dm_table_get_mode);
 EXPORT_SYMBOL(dm_table_put);
 EXPORT_SYMBOL(dm_table_get);