[dm-devel] [PATCH 4/5] kpartx: default to running in sync mode

[Steffen Maier]

On 04/25/2017 12:39 AM, Benjamin Marzinski wrote:
> When users run kpartx, they would naturally assume that when it
> completes, the devices have been created. However, kpartx runs in async
> mode by default.  This seems like it is likely to trip up users.  So,
> switch the default to sync mode, add a -n option to enable async mode,
> and set async mode when kpartx is called by the udev rules.
>
> Signed-off-by: Benjamin Marzinski <bmarzins at redhat.com>
> ---
>  kpartx/kpartx.c     | 10 +++++++---
>  kpartx/kpartx.rules |  2 +-
>  2 files changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/kpartx/kpartx.c b/kpartx/kpartx.c
> index 58e60ff..d1edd5e 100644
> --- a/kpartx/kpartx.c
> +++ b/kpartx/kpartx.c

> -int udev_sync = 0;
> +int udev_sync = 1;

> -	printf("\t-s sync mode. Don't return until the partitions are created\n");
> +	printf("\t-n nosync mode. Return before the partitions are created\n");
> +	printf("\t-s sync mode. Don't return until the partitions are created. Default.\n");

> +		case 'n':
> +			udev_sync = 0;
> +			break;

> diff --git a/kpartx/kpartx.rules b/kpartx/kpartx.rules
> index 48a4d6c..a958791 100644
> --- a/kpartx/kpartx.rules
> +++ b/kpartx/kpartx.rules
> @@ -40,6 +40,6 @@ ENV{DM_NR_VALID_PATHS}=="0", GOTO="kpartx_end"
>  ENV{ENV{DM_UDEV_PRIMARY_SOURCE_FLAG}!="1", IMPORT{db}="DM_SUBSYSTEM_UDEV_FLAG1"
>  ENV{DM_SUBSYSTEM_UDEV_FLAG1}=="1", GOTO="kpartx_end"
>  ENV{DM_STATE}!="SUSPENDED", ENV{DM_UUID}=="mpath-*", \
> -	RUN+="/sbin/kpartx -u -p -part /dev/$name"
> +	RUN+="/sbin/kpartx -un -p -part /dev/$name"

I understand this was async before and is now still async after the 
default change in kpartx. However, I'm wondering in general how one 
would "wait" for kpartx mappings, since I suppose a "udevadm settle" 
would not suffice. Dracut probably does not care because it would loop 
until its required root-fs devices have appeared.

-- 
Mit freundlichen Grüßen / Kind regards
Steffen Maier

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