Re: [PATCH 10/12] libmultipath: filter uevents before proccessing

["Benjamin Marzinski" <bmarzins@redhat.com>]

On Tue, Dec 27, 2016 at 04:03:27PM +0800, tang.junhui@zte.com.cn wrote:
> From: tang.junhui <tang.junhui@zte.com.cn>
> 
> Before merging uevents, these uevents are going to be filtered:
> Change or addition uevent of a removed path (it indicate by an
> deletion uevent occurred later).
> 

I think it's safe to remove add and change uevents if they are followed
by a remove event, regardless of whether or not they have a wwid, as
long as the kernel name is the same.  We only get the remove event when
the device is gone. Processing the add and change events will never get
us anything in these cases, because there is no device to act on.

-Ben

> Change-Id: If00c2c2e23ea466c1d4643c541ed2d8f9a0c8dea
> Signed-off-by: tang.junhui <tang.junhui@zte.com.cn>
> ---
>  libmultipath/uevent.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 55 insertions(+)
> 
> diff --git a/libmultipath/uevent.c b/libmultipath/uevent.c
> index 114068c..424f272 100644
> --- a/libmultipath/uevent.c
> +++ b/libmultipath/uevent.c
> @@ -140,6 +140,28 @@ uevent_can_discard(char *devpath, char *kernel)
>  }
>  
>  bool
> +uevent_can_filter(struct uevent *earlier, struct uevent *later)
> +{
> +
> +	/*
> +	 * filter earlier uvents if path has removed later, eg:
> +	 * "add path3 |chang path3 |add path2 |remove path3"
> +	 * can filter as:
> +	 * "add path2 |remove path3"
> +	 * uevent "add path3" and "chang path3" are filtered out
> +	 */
> +	if (earlier->wwid && later->wwid &&
> +		!strcmp(earlier->wwid, later->wwid) &&
> +		strncmp(later->kernel, "dm-", 3) &&
> +		!strcmp(later->action, "remove") &&
> +		!strcmp(earlier->kernel, later->kernel)) {
> +		return true;
> +	}
> +
> +	return false;
> +}
> +
> +bool
>  merge_need_stop(struct uevent *earlier, struct uevent *later)
>  {
>  	/*
> @@ -196,6 +218,38 @@ uevent_can_merge(struct uevent *earlier, struct uevent *later)
>  }
>  
>  void
> +uevent_filter(struct uevent *later, struct list_head *tmpq)
> +{
> +	struct uevent *earlier, *temp;
> +	/*
> +	 * compare the uevent with earlier uevents
> +	 */
> +	list_for_some_entry_reverse(earlier, &later->node, tmpq, node) {
> +next_earlier_node:
> +		/*
> +		 * filter unnessary earlier uevents by the later uevent
> +		 */
> +		if (uevent_can_filter(earlier, later)) {
> +			condlog(2, "uevent: %s-%s-%s has removed by uevent: %s-%s-%s, filtered",
> +				earlier->action, earlier->kernel, earlier->wwid,
> +				later->action, later->kernel, later->wwid);
> +
> +			temp = earlier;
> +			earlier = list_entry(earlier->node.prev, typeof(struct uevent), node);
> +			list_del_init(&temp->node);
> +			if (temp->udev)
> +				udev_device_unref(temp->udev);
> +			FREE(temp);
> +
> +			if (earlier ==  list_entry(tmpq, typeof(struct uevent), node))
> +				break;
> +			else
> +				goto next_earlier_node;
> +		}
> +	}
> +}
> +
> +void
>  uevent_merge(struct uevent *later, struct list_head *tmpq)
>  {
>  	struct uevent *earlier, *temp;
> @@ -232,6 +286,7 @@ merge_uevq(struct list_head *tmpq)
>  	struct uevent *later;
>  
>  	list_for_each_entry_reverse(later, tmpq, node) {
> +		uevent_filter(later, tmpq);
>  		uevent_merge(later, tmpq);
>  	}
>  }
> -- 
> 2.8.1.windows.1
>