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

[Peter Rajnoha]

On 04/28/2017 07:05 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.
> 

...

> diff --git a/udev-md-raid-creating.rules b/udev-md-raid-creating.rules
> new file mode 100644
> index 000000000000..2be466bcefd2
> --- /dev/null
> +++ b/udev-md-raid-creating.rules
> @@ -0,0 +1,7 @@
> +# do not edit this file, it will be overwritten on update
> +# While mdadm is creating an array, it creates a file
> +# /run/mdadm/creating-mdXXX.  If that file exists, then
> +# the array is not "ready" and we should make sure the
> +# content is ignored.
> +
> +KERNEL=="md*", TEST="/run/mdadm/creating-$kernel", ENV{SYSTEMD_READY}="0"
> 

This should be TEST=="/run/mdadm/creating-$kernel" (double equals sign,
otherwise it's ignored by udev as incorrect rule).

-- 
Peter