From: Mike Snitzer <snitzer@redhat.com>
Date: Fri, 25 Jun 2021 15:18:59 -0400
Subject: [PATCH] dm writecache: add "cleaner" and "max_age" to Documentation
Git-commit: cd039afa0ad86e1f01921cc5abf7f80d2449543a
Patch-mainline: v5.14-rc1
References: git-fixes
Backfill missing Documentation.
Fixes: 93de44eb3fc8 ("dm writecache: implement the "cleaner" policy")
Fixes: 3923d4854e18 ("dm writecache: implement gradual cleanup")
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Hannes Reinecke <hare@suse.com>
---
.../admin-guide/device-mapper/writecache.rst | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/Documentation/admin-guide/device-mapper/writecache.rst b/Documentation/admin-guide/device-mapper/writecache.rst
index dce0184e07ca..c181f26af769 100644
--- a/Documentation/admin-guide/device-mapper/writecache.rst
+++ b/Documentation/admin-guide/device-mapper/writecache.rst
@@ -53,6 +53,21 @@ Constructor parameters:
- some underlying devices perform better with fua, some
with nofua. The user should test it
+ cleaner
+ when this option is activated (either in the constructor
+ arguments or by a message), the cache will not promote
+ new writes (however, writes to already cached blocks are
+ promoted, to avoid data corruption due to misordered
+ writes) and it will gradually writeback any cached
+ data. The userspace can then monitor the cleaning
+ process with "dmsetup status". When the number of cached
+ blocks drops to zero, userspace can unload the
+ dm-writecache target and replace it with dm-linear or
+ other targets.
+ max_age n
+ specifies the maximum age of a block in milliseconds. If
+ a block is stored in the cache for too long, it will be
+ written to the underlying device and cleaned up.
Status:
1. error indicator - 0 if there was no error, otherwise error number
@@ -77,3 +92,5 @@ Messages:
5. resume the device, so that it will use the linear
target
6. the cache device is now inactive and it can be deleted
+ cleaner
+ See above "cleaner" constructor documentation.
--
2.29.2