Bug#773734: lvm2: dmcache created in writeback mode rather than writethrough when the latter has been specified

[Marc Lehmann]

Package: lvm2
Version: 2.02.111-2
Severity: normal

Dear Maintainer,

according to the documentation, the dmcache mode can be specified in
lvconvert using the --cachemode option, but it has no effect.

e.g. after:

   lvconvert --cachepool vg_cerebro/wd_cache --poolmetadata vg_cerebro/wd_cachemeta --cachemode writethrough

dmsetup table shows:

0 38654705664 cache 8 1305/16384 128 141258/655360 130226 121715 20 2 0 0 132365 1 writeback ...
                                                                                   ^^^^^^^^^

I didn't flag this bug report specially, but this bug could be quite
critical, as using an origin device with writeback mode when the user
assumes it was in writehtrough mode can very quickly kill all metadata on
the origin device.


-- System Information:
Debian Release: 7.5
  APT prefers stable
  APT policy: (990, 'stable'), (500, 'unstable'), (500, 'testing'), (500, 'oldstable'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 3.18.1-031801-generic (SMP w/12 CPU cores)
Locale: LANG=C, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/bash

Versions of packages lvm2 depends on:
ii  dmeventd                  2:1.02.90-2
ii  dmsetup                   2:1.02.90-2
ii  init-system-helpers       1.19
ii  initscripts               2.88dsf-41+deb7u1
ii  libc6                     2.19-1
ii  libdevmapper-event1.02.1  2:1.02.74-8
ii  libdevmapper1.02.1        2:1.02.90-2
ii  libreadline5              5.2+dfsg-2~deb7u1
ii  libudev1                  215-4
ii  lsb-base                  4.1+Debian12

lvm2 recommends no packages.

Versions of packages lvm2 suggests:
ii  thin-provisioning-tools  0.3.2-1

-- debconf information excluded