Re: [PATCH 1/2] FIX: mdmon doesn't start

[NeilBrown <neilb@suse.de>]

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On Thu, 03 Nov 2011 17:55:33 +0100 Adam Kwolek <adam.kwolek@intel.com> wrote:

> When array is not clean dismounted directory /dev/.mdadm is not cleaned up.
> On array re-assembly read pid is not valid and it is not possible
> to connect to monitor. This causes mdmon to exit and array remains
> not monitored.
> Problem is introduced by fix:
>    mdmon(): Error out if failing to connect to victim monitor
>    819c158866f466075a1c719f0dc496deb2fb3814
> 
> This is critical for container reshape when mdmon is should finish reshape.
> when reshape is not finished, array is reshaped again by mdadm.
> 
> Signed-off-by: Adam Kwolek <adam.kwolek@intel.com>
> ---
> 
>  mdmon.c |   15 ++++++++++-----
>  1 files changed, 10 insertions(+), 5 deletions(-)
> 
> diff --git a/mdmon.c b/mdmon.c
> index bdcda0e..5ac7cd6 100644
> --- a/mdmon.c
> +++ b/mdmon.c
> @@ -458,11 +458,16 @@ static int mdmon(char *devname, int devnum, int must_fork, int takeover)
>  
>  	victim = mdmon_pid(container->devnum);
>  	if (victim >= 0) {
> -		victim_sock = connect_monitor(container->devname);
> -		if (victim_sock < 0) {
> -			fprintf(stderr, "mdmon: %s unable to connect monitor\n",
> -				container->devname);
> -			exit(3);
> +		/* It is possible that mdmon that wrote pid file was killed.
> +		 * check if read pid is valid/mdmon is running
> +		 */
> +		if (mdmon_running(victim)) {
> +			victim_sock = connect_monitor(container->devname);
> +			if (victim_sock < 0) {
> +				fprintf(stderr, "mdmon: %s unable to connect "
> +					"monitor\n", container->devname);
> +				exit(3);
> +			}
>  		}
>  	}
>  

Thanks for the patch.
I decided to revert the patch that originally caused the problem instead - it
really isn't needed.
I then added a patch to make sure we never use victim_sock when it is -1.
The places were we might have used it we not dangerous at all, but it is
cleaner to check.

Thanks,
NeilBrown

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