[PATCH] Cygwin: Add /dev/disk/by-id symlinks
Corinna Vinschen
corinna-cygwin@cygwin.com
Tue Nov 7 13:29:45 GMT 2023
On Nov 7 11:10, Christian Franke wrote:
> Corinna Vinschen wrote:
> > Hi Christian,
> >
> > On Nov 5 16:45, Christian Franke wrote:
> > > ...
> > > Old IOCTL dropped and code simplified.
> > Great. I pushed your patch.
>
> Thanks.
>
>
> > ...
> > > > Last, but not least, do you see a chance to add any other /dev/disk
> > > > subdir? by-partuuid, perhaps?
> > > Possibly, but not very soon. I'm not yet sure which API functions could be
> > > used.
> > > Some early draft ideas:
> > >
> > > /dev/disk/by-partuid (Partition UUID -> device)
> > > GPT_PART_UUID -> ../../sdXN (GPT partition UUID)
> > > MBR_SERIAL-partN -> ../../sdYM (Fake UUID for MBR)
> > That should only require IOCTL_DISK_GET_PARTITION_INFO_EX, I think.
>
> Easier than expected: DRIVE_LAYOUT_INFORMATION_EX already contains
> PARTITION_INFORMATION_EX so existing scanning function could be enhanced.
> Patch attached.
Nice, pushed!
> > > /dev/disk/by-uuid (Windows Volume UUID -> device)
> > > Vol_UUID1 -> ../../sdXN (disk volume)
> > > Vol_UUID2 -> ../../scd0 (CD/DVD drive volume)
> > > Vol_UUID3 -> /proc/sys/GLOBAL??/Volume{UUID} (others, e.g. VeraCrypt
> > > volume)
> > Yeah, tricky. These are not the partition GUIDs but the filesystem
> > GUIDs or serial numbers. AFAICS, Windows filesystems (FAT*, NTFS)
> > don't maintain a filesystem GUID, as, e. g., ext4 or xfs, but only
> > serial numbers you can fetch via NtQueryVolumeInformationFile.
> > A Linux example of that is the serial number from a FAT32 filesytem
> > as the EFI boot partition in by-uuid:
> >
> > lrwxrwxrwx 1 root root 10 Oct 30 10:20 DC38-0407 -> ../../sda1
> >
> > On second thought, maybe that's sufficient for our by-uuid emulation.
> >
> > > /dev/disk/by-drive (Cygwin specific: drive letter -> volume)
> > > c -> ../by-uuid/UUID (if UUID available)
> > > x -> /proc/sys/DosDevices/X: (others, e.g. Network, "mounted" Volume
> > > Shadow Copy)
> > Ah, good idea. That's what my extension in /proc/partition already
> > provides, but a /dev/disk/by-drive sounds like a great idea.
>
> Left for later :-)
Looking forward to it. We'll just need an entry for the release text
in winsup/cygwin/release/3.5.0 and doc/new-features.xml in the end :)
Thanks,
Corinna
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