On Wed, Jan 25 2023 at 10:33P -0500,
Demi Marie Obenour [off-list ref] wrote:

This work aims to allow userspace to create and destroy block devices
in a race-free and leak-free way,

"race-free and leak-free way" implies there both races and leaks in
existing code. You're making claims that are likely very specific to
your Xen use-case.  Please explain more carefully.

and to allow them to be exposed to
other Xen VMs via blkback without leaks or races.  It’s marked as RFC
for a few reasons:

- The code has been only lightly tested.  It might be unstable or
  insecure.

- The DM_DEV_CREATE ioctl gains a new flag.  Unknown flags were
  previously ignored, so this could theoretically break buggy userspace
  tools.

Not seeing a reason that type of DM change is needed. If you feel
strongly about it send a separate patch and we can discuss it.

- I have no idea if I got the block device reference counting and
  locking correct.

Your headers and justifcation for this line of work are really way too
terse. Please take the time to clearly make the case for your changes
in both the patch headers and code.

Mike