dm: delay target

New device-mapper target that can delay I/O (for testing).  Reads can be
separated from writes, redirected to different underlying devices and delayed
by differing amounts of time.

Signed-off-by: Heinz Mauelshagen <mauelshagen@redhat.com>
Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index 4540ade6b6b5..7df934d69134 100644
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -262,6 +262,15 @@ config DM_MULTIPATH_EMC
         ---help---
           Multipath support for EMC CX/AX series hardware.
 
+config DM_DELAY
+        tristate "I/O delaying target (EXPERIMENTAL)"
+        depends on BLK_DEV_DM && EXPERIMENTAL
+        ---help---
+        A target that delays reads and/or writes and can send
+        them to different devices.  Useful for testing.
+
+        If unsure, say N.
+
 endmenu
 
 endif