[dm-devel] [mdadm PATCH] Create: tell udev md device is not ready when first created.

[Peter Rajnoha]

On 05/02/2017 03:42 PM, Jes Sorensen wrote:
> On 04/28/2017 01:05 AM, NeilBrown wrote:
>>
>> When an array is created the content is not initialized,
>> so it could have remnants of an old filesystem or md array
>> etc on it.
>> udev will see this and might try to activate it, which is almost
>> certainly not what is wanted.
>>
>> So create a mechanism for mdadm to communicate with udev to tell
>> it that the device isn't ready.  This mechanism is the existance
>> of a file /run/mdadm/created-mdXXX where mdXXX is the md device name.
>>
>> When creating an array, mdadm will create the file.
>> A new udev rule file, 01-md-raid-creating.rules, will detect the
>> precense of thst file and set ENV{SYSTEMD_READY}="0".
>> This is fairly uniformly used to suppress actions based on the
>> contents of the device.
>>
>> Signed-off-by: NeilBrown <neilb at suse.com>
>> ---
>>  Assemble.c                  |  2 +-
>>  Build.c                     |  2 +-
>>  Create.c                    |  9 +++++++-
>>  Incremental.c               |  4 ++--
>>  Makefile                    |  4 ++--
>>  lib.c                       | 29 +++++++++++++++++++++++++
>>  mdadm.h                     |  4 +++-
>>  mdopen.c                    | 52
>> ++++++++++++++++++++++++++++-----------------
>>  udev-md-raid-creating.rules |  7 ++++++
>>  9 files changed, 86 insertions(+), 27 deletions(-)
>>  create mode 100644 udev-md-raid-creating.rules
> 
> Applied!
> 

How is this solving the problem then? The patch is flagging a device as
not ready, then clearing the flag after some time. Where does the wiping
happen actually?

-- 
Peter