Re: [PATCH] Cygwin: Add /dev/disk/by-id symlinks

[Corinna Vinschen <corinna-cygwin@cygwin.com>]

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