Multipath plugin compatibility
Files: 3.26.0 Duistribution: Debian/testing 2017-11-04
If libblockdev-mpath2 (2.12-3, Multipath plugin for libblockdev) is not installed, nautilus functions as expected for the first partition of my 2nd drive without any entry on /etc/fstab (/dev/sdb1) as expected. Clicking "+ Other locations" shows /dev/sdb1 with its partition label. Clicking it will mount it.
If libblockdev-mpath2 (2.12-3, Multipath plugin for libblockdev) is installed, nautilus functions a bit strange to the eyes of novice. Clicking "+ Other locations" shows /dev/sdb1 with its partition label and /dev/dm-0 with its device product name. Clicking icon on /dev/dm-0 will mount it. That's good. But since /dev/sdb1 is already used by device mapper, you can't mount /dev/sdb1 anymore. This is understandable situation if you know what is happening but not so nice to the general public. The error message given by Files program is correct but is vague and not explicitly enough on the situation.
In case of mount error, it should check the situation around multipath and provide nicer message is desirable.
If possible, icon for /dev/sdb1 should indicate it is already used by the device mapper as it is displayed. Then user will have fuller understanding of the situation and no false expectation to mount /dev/sdb1.
In my case, libblockdev-mpath2 was pulled in by the package dependency. It took me a while to identify what was going on. I coukldn't even mount /dev/sdb1 with the mount program. Proper GUI display of situation should make it easy for people.
Also, it may be good idea to allow GUI to free /dev/sdb1 etc.