[PATCH] mdmon@.service: Change type of process start-up to 'forking'.

[PATCH] mdmon@.service: Change type of process start-up to 'forking'.

[Pawel Baldysiak]

Mdadm does not wait enough time when mdmon is started by systemd.
It causes various problems with behaviour of a RAID volume with external metadata.
For example: mdmon does not update a value of checkpoint during migration
and second RAID5 volume is read-only after reboot done during
container reshape (both problems occur with IMSM matadata).
If a type of process start-up is changed to 'forking', systemctl will
wait until mdmon (parent) process exits after calling fork.
This way mdmon will always be fully initialized after start_mdmon
and these problems will not occur.
In this case it is recommended to add a path to PIDFile, so that systemd
does not have to guess a PID of the mdmon process.

Signed-off-by: Pawel Baldysiak <pawel.baldysiak@intel.com>
Reviewed-by: Artur Paszkiewicz <artur.paszkiewicz@intel.com>
Reviewed-by: Lukasz Dorau <lukasz.dorau@intel.com>
---
 systemd/mdmon@.service |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/systemd/mdmon@.service b/systemd/mdmon@.service
index 5520cd0..304b26e 100644
--- a/systemd/mdmon@.service
+++ b/systemd/mdmon@.service
@@ -14,5 +14,7 @@ Before=initrd-switch-root.target
 # mdmon should never complain due to lack of a platform,
 # that is mdadm's job if at all.
 Environment=IMSM_NO_PLATFORM=1
-ExecStart=/sbin/mdmon --foreground %I
+ExecStart=/sbin/mdmon %I
+Type=forking
+PIDFile=/run/mdadm/%I.pid
 KillMode=none

Re: [PATCH] mdmon@.service: Change type of process start-up to 'forking'.

[NeilBrown]

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On Thu, 06 Mar 2014 15:51:44 +0100 Pawel Baldysiak
<pawel.baldysiak@intel.com> wrote:

> Mdadm does not wait enough time when mdmon is started by systemd.
> It causes various problems with behaviour of a RAID volume with external metadata.
> For example: mdmon does not update a value of checkpoint during migration
> and second RAID5 volume is read-only after reboot done during
> container reshape (both problems occur with IMSM matadata).
> If a type of process start-up is changed to 'forking', systemctl will
> wait until mdmon (parent) process exits after calling fork.
> This way mdmon will always be fully initialized after start_mdmon
> and these problems will not occur.
> In this case it is recommended to add a path to PIDFile, so that systemd
> does not have to guess a PID of the mdmon process.
> 
> Signed-off-by: Pawel Baldysiak <pawel.baldysiak@intel.com>
> Reviewed-by: Artur Paszkiewicz <artur.paszkiewicz@intel.com>
> Reviewed-by: Lukasz Dorau <lukasz.dorau@intel.com>
> ---
>  systemd/mdmon@.service |    4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/systemd/mdmon@.service b/systemd/mdmon@.service
> index 5520cd0..304b26e 100644
> --- a/systemd/mdmon@.service
> +++ b/systemd/mdmon@.service
> @@ -14,5 +14,7 @@ Before=initrd-switch-root.target
>  # mdmon should never complain due to lack of a platform,
>  # that is mdadm's job if at all.
>  Environment=IMSM_NO_PLATFORM=1
> -ExecStart=/sbin/mdmon --foreground %I
> +ExecStart=/sbin/mdmon %I
> +Type=forking
> +PIDFile=/run/mdadm/%I.pid
>  KillMode=none
> 

applied, thanks.

I wonder if we should try to make it use MDMON_DIR instead of /run/mdadm ...
though anyone who uses systemd almost certainly uses /run so it probably
doesn't matter.

Thanks,
NeilBrown

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