dm: add log writes target

Introduce a new target that is meant for file system developers to test file
system integrity at particular points in the life of a file system.  We capture
all write requests and associated data and log them to a separate device
for later replay.  There is a userspace utility to do this replay.  The
idea behind this is to give file system developers a tool to verify that
the file system is always consistent.

Signed-off-by: Josef Bacik <jbacik@fb.com>
Reviewed-by: Zach Brown <zab@zabbo.net>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index 109f9dc..6ddc9834 100644
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -443,4 +443,20 @@ config DM_SWITCH
 
 	  If unsure, say N.
 
+config DM_LOG_WRITES
+	tristate "Log writes target support"
+	depends on BLK_DEV_DM
+	---help---
+	  This device-mapper target takes two devices, one device to use
+	  normally, one to log all write operations done to the first device.
+	  This is for use by file system developers wishing to verify that
+	  their fs is writing a consitent file system at all times by allowing
+	  them to replay the log in a variety of ways and to check the
+	  contents.
+
+	  To compile this code as a module, choose M here: the module will
+	  be called dm-log-writes.
+
+	  If unsure, say N.
+
 endif # MD