dm: add thin provisioning target

Initial EXPERIMENTAL implementation of device-mapper thin provisioning
with snapshot support.  The 'thin' target is used to create instances of
the virtual devices that are hosted in the 'thin-pool' target.  The
thin-pool target provides data sharing among devices.  This sharing is
made possible using the persistent-data library in the previous patch.

The main highlight of this implementation, compared to the previous
implementation of snapshots, is that it allows many virtual devices to
be stored on the same data volume, simplifying administration and
allowing sharing of data between volumes (thus reducing disk usage).

Another big feature is support for arbitrary depth of recursive
snapshots (snapshots of snapshots of snapshots ...).  The previous
implementation of snapshots did this by chaining together lookup tables,
and so performance was O(depth).  This new implementation uses a single
data structure so we don't get this degradation with depth.

For further information and examples of how to use this, please read
Documentation/device-mapper/thin-provisioning.txt

Signed-off-by: Joe Thornber <thornber@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

1 files changed, 28 insertions, 0 deletions

diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index b1a92149704..faa4741df6d 100644
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -216,6 +216,8 @@ config DM_BUFIO
 	 as a cache, holding recently-read blocks in memory and performing
 	 delayed writes.
 
+source "drivers/md/persistent-data/Kconfig"
+
 config DM_CRYPT
 	tristate "Crypt target support"
 	depends on BLK_DEV_DM
@@ -241,6 +243,32 @@ config DM_SNAPSHOT
        ---help---
          Allow volume managers to take writable snapshots of a device.
 
+config DM_THIN_PROVISIONING
+       tristate "Thin provisioning target (EXPERIMENTAL)"
+       depends on BLK_DEV_DM && EXPERIMENTAL
+       select DM_PERSISTENT_DATA
+       ---help---
+         Provides thin provisioning and snapshots that share a data store.
+
+config DM_DEBUG_BLOCK_STACK_TRACING
+	boolean "Keep stack trace of thin provisioning block lock holders"
+	depends on STACKTRACE_SUPPORT && DM_THIN_PROVISIONING
+	select STACKTRACE
+	---help---
+	  Enable this for messages that may help debug problems with the
+	  block manager locking used by thin provisioning.
+
+	  If unsure, say N.
+
+config DM_DEBUG_SPACE_MAPS
+	boolean "Extra validation for thin provisioning space maps"
+	depends on DM_THIN_PROVISIONING
+	---help---
+	  Enable this for messages that may help debug problems with the
+	  space maps used by thin provisioning.
+
+          If unsure, say N.
+
 config DM_MIRROR
        tristate "Mirror target"
        depends on BLK_DEV_DM