On Wed, Jun 23, 2021 at 12:58:58PM +0200, Matteo Croce wrote:

From: Matteo Croce <redacted>

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?