(Re-sending, as the first one got blocked by the list for having an HTML part). On Sun, Aug 21, 2022 at 7:47 AM Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > > On Sun, Aug 21, 2022 at 12:17:30PM +0100, James Dutton wrote: > > I know my suggested behaviour might be detrimental for some users, in > > case one modifies the usb disk in another computer and then comes > > back, but I would like an option that assumes it has not been plugged > > into anything else. In the “old days” (that is, my original design for use-storage) it used to do exactly what you are looking for - based on VID, DID, and SerialNumber it would “remember” devices. The SCSI host would never be destroyed, and when a device re-appeared it would be re-connected to the existing host. That caused all sorts of problems. The SCSI and block layers just couldn’t handle it well. A clean umount / mount cycle worked fine, but if you unexpectedly disconnected the device all hell broke loose and there was no way to recover. I did it this way because, way back when, there were issues dynamically destroying SCSI hosts. The people who worked on those other layers found it much, much easier to fix that problem than try to make it possible to recover from an unexpected disconnect. Honestly, I’m not even sure where you would need to begin to make this work. It would require pretty radical changes is the block I/O layers to differentiate different failure modes, keep a lot more data around after certain types of failures, allow for specifying which devices this new policy (which is assuming reconnected devices really haven’t been altered) applies to, etc — it’s a big lift. Matt aka “the guy who originally designed how this works” -- Matthew Dharm Former Maintainer, USB Mass Storage driver for Linux
