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authorMike Snitzer <snitzer@redhat.com>2019-02-25 11:07:10 -0500
committerMike Snitzer <snitzer@redhat.com>2019-03-05 14:53:52 -0500
commitde7180ff908b2bc0342e832dbdaa9a5f1ecaa33a (patch)
treedb7c3b6e894a7d5f96ab155500ff5a8275cfad66 /Documentation/device-mapper
parentf87e033b3b923d91194348c11221e1bbc92e51b2 (diff)
downloadlinux-de7180ff908b2bc0342e832dbdaa9a5f1ecaa33a.tar.bz2
dm cache: add support for discard passdown to the origin device
DM cache now defaults to passing discards down to the origin device. User may disable this using the "no_discard_passdown" feature when creating the cache device. If the cache's underlying origin device doesn't support discards then passdown is disabled (with warning). Similarly, if the underlying origin device's max_discard_sectors is less than a cache block discard passdown will be disabled (this is required because sizing of the cache internal discard bitset depends on it). Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Diffstat (limited to 'Documentation/device-mapper')
-rw-r--r--Documentation/device-mapper/cache.txt3
1 files changed, 3 insertions, 0 deletions
diff --git a/Documentation/device-mapper/cache.txt b/Documentation/device-mapper/cache.txt
index ff0841711fd5..8ae1cf8e94da 100644
--- a/Documentation/device-mapper/cache.txt
+++ b/Documentation/device-mapper/cache.txt
@@ -206,6 +206,9 @@ Optional feature arguments are:
in a separate btree, which improves speed of shutting
down the cache.
+ no_discard_passdown : disable passing down discards from the cache
+ to the origin's data device.
+
A policy called 'default' is always registered. This is an alias for
the policy we currently think is giving best all round performance.