diff options
| author | Mike Snitzer <snitzer@redhat.com> | 2015-10-08 18:05:41 -0400 |
|---|---|---|
| committer | Mike Snitzer <snitzer@redhat.com> | 2015-10-09 16:57:03 -0400 |
| commit | b0d3cc011e532d8c9db76cf717bcafa53c135595 (patch) | |
| tree | d74330dcf71a599d637a7eecad8b56cdbd4487b9 /Documentation/device-mapper | |
| parent | 2bffa1503c5c06192eb1459180fac4416575a966 (diff) | |
dm snapshot: add new persistent store option to support overflow
Commit 76c44f6d80 introduced the possibly for "Overflow" to be reported
by the snapshot device's status. Older userspace (e.g. lvm2) does not
handle the "Overflow" status response.
Fix this incompatibility by requiring newer userspace code, that can
cope with "Overflow", request the persistent store with overflow support
by using "PO" (Persistent with Overflow) for the snapshot store type.
Reported-by: Zdenek Kabelac <zkabelac@redhat.com>
Fixes: 76c44f6d80 ("dm snapshot: don't invalidate on-disk image on snapshot write overflow")
Reviewed-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Diffstat (limited to 'Documentation/device-mapper')
| -rw-r--r-- | Documentation/device-mapper/snapshot.txt | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/Documentation/device-mapper/snapshot.txt b/Documentation/device-mapper/snapshot.txt index 0d5bc46dc167..ad6949bff2e3 100644 --- a/Documentation/device-mapper/snapshot.txt +++ b/Documentation/device-mapper/snapshot.txt @@ -41,9 +41,13 @@ useless and be disabled, returning errors. So it is important to monitor the amount of free space and expand the <COW device> before it fills up. <persistent?> is P (Persistent) or N (Not persistent - will not survive -after reboot). -The difference is that for transient snapshots less metadata must be -saved on disk - they can be kept in memory by the kernel. +after reboot). O (Overflow) can be added as a persistent store option +to allow userspace to advertise its support for seeing "Overflow" in the +snapshot status. So supported store types are "P", "PO" and "N". + +The difference between persistent and transient is with transient +snapshots less metadata must be saved on disk - they can be kept in +memory by the kernel. * snapshot-merge <origin> <COW device> <persistent> <chunksize> |