dm cache metadata: add "metadata2" feature
If "metadata2" is provided as a table argument when creating/loading a
cache target a more compact metadata format, with separate dirty bits,
is used. "metadata2" improves speed of shutting down a cache target.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
diff --git a/Documentation/device-mapper/cache.txt b/Documentation/device-mapper/cache.txt
index 785eab8..f228604 100644
--- a/Documentation/device-mapper/cache.txt
+++ b/Documentation/device-mapper/cache.txt
@@ -207,6 +207,10 @@
block, then the cache block is invalidated.
To enable passthrough mode the cache must be clean.
+ metadata2 : use version 2 of the metadata. This stores the dirty bits
+ in a separate btree, which improves speed of shutting
+ down the cache.
+
A policy called 'default' is always registered. This is an alias for
the policy we currently think is giving best all round performance.