diff options
| author | Joe Thornber <ejt@redhat.com> | 2015-04-22 16:42:35 -0400 |
|---|---|---|
| committer | Mike Snitzer <snitzer@redhat.com> | 2015-06-11 17:13:00 -0400 |
| commit | 028ae9f76f2935e8cf9974bff9a4587e3a995ff3 (patch) | |
| tree | 1bd3984690e112d03cf1e56d43b32c000e420ab4 /Documentation/device-mapper | |
| parent | 88bf5184fa5861e766e39fd34fc6d21557ac7be8 (diff) | |
dm cache: add fail io mode and needs_check flag
If a cache metadata operation fails (e.g. transaction commit) the
cache's metadata device will abort the current transaction, set a new
needs_check flag, and the cache will transition to "read-only" mode. If
aborting the transaction or setting the needs_check flag fails the cache
will transition to "fail-io" mode.
Once needs_check is set the cache device will not be allowed to
activate. Activation requires write access to metadata. Future work is
needed to add proper support for running the cache in read-only mode.
Once in fail-io mode the cache will report a status of "Fail".
Also, add commit() wrapper that will disallow commits if in read_only or
fail mode.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Diffstat (limited to 'Documentation/device-mapper')
| -rw-r--r-- | Documentation/device-mapper/cache.txt | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/Documentation/device-mapper/cache.txt b/Documentation/device-mapper/cache.txt index 68c0f517c60e..82960cffbad3 100644 --- a/Documentation/device-mapper/cache.txt +++ b/Documentation/device-mapper/cache.txt @@ -221,6 +221,7 @@ Status <#read hits> <#read misses> <#write hits> <#write misses> <#demotions> <#promotions> <#dirty> <#features> <features>* <#core args> <core args>* <policy name> <#policy args> <policy args>* +<cache metadata mode> metadata block size : Fixed block size for each metadata block in sectors @@ -251,8 +252,12 @@ core args : Key/value pairs for tuning the core e.g. migration_threshold policy name : Name of the policy #policy args : Number of policy arguments to follow (must be even) -policy args : Key/value pairs - e.g. sequential_threshold +policy args : Key/value pairs e.g. sequential_threshold +cache metadata mode : ro if read-only, rw if read-write + 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. Messages -------- |