[dm-devel] [PATCH 4/7] libmultipath: force map reload if udev incomplete

[Benjamin Marzinski]

On Thu, Dec 17, 2020 at 12:00:15PM +0100, mwilck at suse.com wrote:
> From: Martin Wilck <mwilck at suse.com>
> 
> We've recently observed various cases of incompletely processed uevents
> during initrd processing. Typically, this would leave a dm device in
> the state it had after the initial "add" uevent, which is basically unusable,
> because udevd had been killed by systemd before processing the subsequent
> "change" event. After switching root, the coldplug event would re-read
> the db file, which would be in unusable state, and would not do anything.
> In such cases, a RELOAD action with force_udev_reload=1 is in order to
> make udev re-process the device completely (DM_UDEV_PRIMARY_SOURCE_FLAG=1 and
> DM_SUBSYSTEM_UDEV_FLAG0=0).
> 
> The previous commits
> 
> 2b25a9e libmultipath: select_action(): force udev reload for uninitialized maps
> cb10d38 multipathd: uev_trigger(): handle incomplete ADD events
> 
> addressed the same issue, but incompletely. They would miss cases where the
> map was configured correctly but none of the RELOAD criteria were met.
> This patch partially reverts 2b25a9e by converting select_reload_action() into
> a trivial helper. Instead, we now check for incompletely initialized udev now
> before checking any of the other reload criteria.
> 
Reviewed-by: Benjamin Marzinski <bmarzins at redhat.com>
> Signed-off-by: Martin Wilck <mwilck at suse.com>
> ---
>  libmultipath/configure.c | 45 ++++++++++++++++++++++++++--------------
>  1 file changed, 29 insertions(+), 16 deletions(-)
> 
> diff --git a/libmultipath/configure.c b/libmultipath/configure.c
> index 3dbc1f1..d64fe88 100644
> --- a/libmultipath/configure.c
> +++ b/libmultipath/configure.c
> @@ -695,12 +695,11 @@ sysfs_set_max_sectors_kb(struct multipath *mpp, int is_reload)
>  	return err;
>  }
>  
> -static void
> -select_reload_action(struct multipath *mpp, const struct multipath *cmpp,
> -		     const char *reason)
> +static bool is_udev_ready(struct multipath *cmpp)
>  {
>  	struct udev_device *mpp_ud;
>  	const char *env;
> +	bool rc;
>  
>  	/*
>  	 * MPATH_DEVICE_READY != 1 can mean two things:
> @@ -712,14 +711,20 @@ select_reload_action(struct multipath *mpp, const struct multipath *cmpp,
>  	 */
>  
>  	mpp_ud = get_udev_for_mpp(cmpp);
> +	if (!mpp_ud)
> +		return true;
>  	env = udev_device_get_property_value(mpp_ud, "MPATH_DEVICE_READY");
> -	if ((!env || strcmp(env, "1")) && count_active_paths(mpp) > 0)
> -		mpp->force_udev_reload = 1;
> +	rc = (env != NULL && !strcmp(env, "1"));
>  	udev_device_unref(mpp_ud);
> +	condlog(4, "%s: %s: \"%s\" -> %d\n", __func__, cmpp->alias, env, rc);
> +	return rc;
> +}
> +
> +static void
> +select_reload_action(struct multipath *mpp, const char *reason)
> +{
>  	mpp->action = ACT_RELOAD;
> -	condlog(3, "%s: set ACT_RELOAD (%s%s)", mpp->alias,
> -		mpp->force_udev_reload ? "forced, " : "",
> -		reason);
> +	condlog(3, "%s: set ACT_RELOAD (%s)", mpp->alias, reason);
>  }
>  
>  void select_action (struct multipath *mpp, const struct _vector *curmp,
> @@ -788,10 +793,18 @@ void select_action (struct multipath *mpp, const struct _vector *curmp,
>  		return;
>  	}
>  
> +	if (!is_udev_ready(cmpp) && count_active_paths(mpp) > 0) {
> +		mpp->force_udev_reload = 1;
> +		mpp->action = ACT_RELOAD;
> +		condlog(3, "%s: set ACT_RELOAD (udev incomplete)",
> +			mpp->alias);
> +		return;
> +	}
> +
>  	if (mpp->no_path_retry != NO_PATH_RETRY_UNDEF &&
>  	    !!strstr(mpp->features, "queue_if_no_path") !=
>  	    !!strstr(cmpp->features, "queue_if_no_path")) {
> -		select_reload_action(mpp, cmpp, "no_path_retry change");
> +		select_reload_action(mpp, "no_path_retry change");
>  		return;
>  	}
>  	if ((mpp->retain_hwhandler != RETAIN_HWHANDLER_ON ||
> @@ -799,7 +812,7 @@ void select_action (struct multipath *mpp, const struct _vector *curmp,
>  	    (strlen(cmpp->hwhandler) != strlen(mpp->hwhandler) ||
>  	     strncmp(cmpp->hwhandler, mpp->hwhandler,
>  		    strlen(mpp->hwhandler)))) {
> -		select_reload_action(mpp, cmpp, "hwhandler change");
> +		select_reload_action(mpp, "hwhandler change");
>  		return;
>  	}
>  
> @@ -807,7 +820,7 @@ void select_action (struct multipath *mpp, const struct _vector *curmp,
>  	    !!strstr(mpp->features, "retain_attached_hw_handler") !=
>  	    !!strstr(cmpp->features, "retain_attached_hw_handler") &&
>  	    get_linux_version_code() < KERNEL_VERSION(4, 3, 0)) {
> -		select_reload_action(mpp, cmpp, "retain_hwhandler change");
> +		select_reload_action(mpp, "retain_hwhandler change");
>  		return;
>  	}
>  
> @@ -819,7 +832,7 @@ void select_action (struct multipath *mpp, const struct _vector *curmp,
>  		remove_feature(&cmpp_feat, "queue_if_no_path");
>  		remove_feature(&cmpp_feat, "retain_attached_hw_handler");
>  		if (strncmp(mpp_feat, cmpp_feat, PARAMS_SIZE)) {
> -			select_reload_action(mpp, cmpp, "features change");
> +			select_reload_action(mpp, "features change");
>  			FREE(cmpp_feat);
>  			FREE(mpp_feat);
>  			return;
> @@ -830,19 +843,19 @@ void select_action (struct multipath *mpp, const struct _vector *curmp,
>  
>  	if (!cmpp->selector || strncmp(cmpp->selector, mpp->selector,
>  		    strlen(mpp->selector))) {
> -		select_reload_action(mpp, cmpp, "selector change");
> +		select_reload_action(mpp, "selector change");
>  		return;
>  	}
>  	if (cmpp->minio != mpp->minio) {
> -		select_reload_action(mpp, cmpp, "minio change");
> +		select_reload_action(mpp, "minio change");
>  		return;
>  	}
>  	if (!cmpp->pg || VECTOR_SIZE(cmpp->pg) != VECTOR_SIZE(mpp->pg)) {
> -		select_reload_action(mpp, cmpp, "path group number change");
> +		select_reload_action(mpp, "path group number change");
>  		return;
>  	}
>  	if (pgcmp(mpp, cmpp)) {
> -		select_reload_action(mpp, cmpp, "path group topology change");
> +		select_reload_action(mpp, "path group topology change");
>  		return;
>  	}
>  	if (cmpp->nextpg != mpp->bestpg) {
> -- 
> 2.29.0