Re: [PATCH v3 6/6] loop: increment sequence number

[Christoph Hellwig]

On Wed, Jun 23, 2021 at 12:58:58PM +0200, Matteo Croce wrote:
> From: Matteo Croce <mcroce@xxxxxxxxxxxxx>
> 
> On a very loaded system, if there are many events queued up from multiple
> attach/detach cycles, it's impossible to match them up with the
> LOOP_CONFIGURE or LOOP_SET_FD call, since we don't know where the position
> of our own association in the queue is[1].
> Not even an empty uevent queue is a reliable indication that we already
> received the uevent we were waiting for, since with multi-partition block
> devices each partition's event is queued asynchronously and might be
> delivered later.
> 
> Increment the disk sequence number when setting or changing the backing
> file, so the userspace knows which backing file generated the event:

Instead of manually incrementing the sequence here, can we make loop
generate the DISK_EVENT_MEDIA_CHANGE event on a backing device (aka
media) change?