Flag/colour for directory which is a btrfs subvolume

[daviessm]

Would it be possible to flag a directory which is a subvolume in the btrfs filesystem? These directories have an inode type of 2 or 256 when the filesystem type is btrfs: https://stackoverflow.com/a/32865333/5293556

I wouldn't mind whether a character other than d or a different colour was used for these, it would just be nice to see them.

[daviessm]

Upon further investigation, it's the inode number which signifies a subvolume, so I can see them by using -i and looking for 2 or 256. It would still be nice to highlight those without having to look through inode numbers though.

[daviessm]

I have started work on this in https://github.com/daviessm/exa/tree/issue_434_subvolumes - it correctly detects subvolumes by ino as described above, but needs to also check that the filesystem type is btrfs.

This can be done with getmntent() from libc as described here: https://stackoverflow.com/questions/40659638/how-can-i-determine-the-mount-path-of-a-given-file-on-linux-in-c but that will need to be cached as there could be thousands of calls per run of exa.

[ogham]

Hi there, and sorry for not leaving a reply until now.

I've looked at your code, and it all looks good. If detecting a subvolume really is as easy as checking the inode, then I'll be happy to merge it in.

[daviessm]

No worries, yes it is that simple - but obviously this will only apply if the volume the directory is on is actually btrfs - otherwise there's a remote possibility of false positives (where the inode number of a directory just happens to be 2 or 256). I haven't figured out yet how to check that.

[ogham]

Aaah, you’re right, I missed that bit. Running find / -type d -inum 2 on my machine actually did produce results in /dev, /run, and /net. One option would be to ignore those three directories, but that feels like a hack.

What about if it checked the inode first, and then only ran getmntent if the inode matches?

[daviessm]

I think that's what I'd do, yeah. However it's beyond my Rust skills at the moment so I'll do it when I get around to it later unless you want to pick it up first.

I was also thinking about caching all the getmntents somewhere once they've been looked up, because there might be lots of directories within directories, all of which are subvolumes, and that would result in a lot of lookups. Could they be used for anything else (like highlighting mount points themselves...)?

[daviessm]

New PR: #941