Diffstat (limited to 'Documentation/device-mapper/thin-provisioning.txt')
1 files changed, 23 insertions, 1 deletions
diff --git a/Documentation/device-mapper/thin-provisioning.txt b/Documentation/device-mapper/thin-provisioning.txt
index f5cfc62..30b8b83 100644
@@ -231,6 +231,9 @@ i) Constructor
no_discard_passdown: Don't pass discards down to the underlying
data device, but just remove the mapping.
+ read_only: Don't allow any changes to be made to the pool
Data block size must be between 64KB (128 sectors) and 1GB
(2097152 sectors) inclusive.
@@ -239,7 +242,7 @@ ii) Status
<transaction id> <used metadata blocks>/<total metadata blocks>
<used data blocks>/<total data blocks> <held metadata root>
+ [no_]discard_passdown ro|rw
A 64-bit number used by userspace to help synchronise with metadata
@@ -257,6 +260,21 @@ ii) Status
held root. This feature is not yet implemented so '-' is
+ Whether or not discards are actually being passed down to the
+ underlying device. When this is enabled when loading the table,
+ it can get disabled if the underlying device doesn't support it.
+ If the pool encounters certain types of device failures it will
+ drop into a read-only metadata mode in which no changes to
+ the pool metadata (like allocating new blocks) are permitted.
+ In serious cases where even a read-only mode is deemed unsafe
+ no further I/O will be permitted and the status will just
+ contain the string 'Fail'. The userspace recovery tools
+ should then be used.
create_thin <dev id>
@@ -329,3 +347,7 @@ regain some space then send the 'trim' message to the pool.
<nr mapped sectors> <highest mapped sector>
+ If the pool has encountered device errors and failed, the status
+ will just contain the string 'Fail'. The userspace recovery
+ tools should then be used.