Re: [PATCH] imsm: retry load_and_parse_mpb if we suspect mdmon has made modifications

[NeilBrown <neilb@suse.de>]

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On Fri, 30 May 2014 15:18:33 +0200 Artur Paszkiewicz
<artur.paszkiewicz@intel.com> wrote:

> If the checksum verification fails in mdadm and mdmon is running, retry
> the load to get a consistent snapshot of the mpb.
> 
> Based on db575f3b
> 
> Signed-off-by: Artur Paszkiewicz <artur.paszkiewicz@intel.com>
> Reviewed-by: Pawel Baldysiak <pawel.baldysiak@intel.com>
> ---
>  super-intel.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/super-intel.c b/super-intel.c
> index f0a7ab5..037c018 100644
> --- a/super-intel.c
> +++ b/super-intel.c
> @@ -4422,6 +4422,7 @@ static int load_super_imsm(struct supertype *st, int fd, char *devname)
>  {
>  	struct intel_super *super;
>  	int rv;
> +	int retry;
>  
>  	if (test_partition(fd))
>  		/* IMSM not allowed on partitions */
> @@ -4444,6 +4445,22 @@ static int load_super_imsm(struct supertype *st, int fd, char *devname)
>  	}
>  	rv = load_and_parse_mpb(fd, super, devname, 0);
>  
> +	/* retry the load if we might have raced against mdmon */
> +	if (rv == 3) {
> +		struct mdstat_ent *mdstat = mdstat_by_component(fd2devnm(fd));
> +
> +		if (mdmon_running(mdstat->devnm) && getpid() != mdmon_pid(mdstat->devnm)) {
> +			for (retry = 0; retry < 3; retry++) {
> +				usleep(3000);
> +				rv = load_and_parse_mpb(fd, super, devname, 0);
> +				if (rv != 3)
> +					break;
> +			}
> +		}

The only thing you use from mdstat is devnm, and that is the thing you passed
to mdstat_by_component to get mdstat....

Can you just do
   char *devnm = fd2devnm(fd);
   if (mdmon_running(devnm) && ......)

??

NeilBrown


> +
> +		free_mdstat(mdstat);
> +	}
> +
>  	if (rv) {
>  		if (devname)
>  			pr_err("Failed to load all information "


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