On Thu, Jun 08, 2023 at 12:08:55PM +0200, Roger Pau Monné wrote: > On Tue, May 30, 2023 at 04:31:16PM -0400, Demi Marie Obenour wrote: > > Set "opened" to "0" before the hotplug script is called. Once the > > device node has been opened, set "opened" to "1". > > > > "opened" is used exclusively by userspace. It serves two purposes: > > > > 1. It tells userspace that the diskseq Xenstore entry is supported. > > > > 2. It tells userspace that it can wait for "opened" to be set to 1. > > Once "opened" is 1, blkback has a reference to the device, so > > userspace doesn't need to keep one. > > > > Together, these changes allow userspace to use block devices with > > delete-on-close behavior, such as loop devices with the autoclear flag > > set or device-mapper devices with the deferred-remove flag set. > > Now that I think a bit more about this, how are you planning to handle > reboot with such devices? It's fine for loop (because those get > instantiated by the block script), but likely not with other block > devices, as on reboot the toolstack will find the block device is > gone. > > I guess the delete-on-close is only intended to be used for loop > devices? (or in general block devices that are instantiated by the > block script itself) You understand correctly. -- Sincerely, Demi Marie Obenour (she/her/hers) Invisible Things Lab
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