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dm writecache: add "cleaner" and "max_age" to Documentation

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Backfill missing Documentation.

Fixes: 93de44eb3f ("dm writecache: implement the "cleaner" policy")
Fixes: 3923d4854e ("dm writecache: implement gradual cleanup")
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Mike Snitzer 2021-06-25 15:18:59 -04:00
parent 867de40c4c
commit cd039afa0a
1 changed files with 17 additions and 0 deletions
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17
Documentation/admin-guide/device-mapper/writecache.rst
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@ -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.