On Tue, Oct 27, 2020 at 01:53:31AM +0100, Edward Shishkin wrote: > > > reiser4progs 1.1.x Software Framework Release Number (SFRN) 4.0.1 file > > > system utilities should not be used to check/fix media formatted 'a > > > priori' in SFRN 4.0.2 and vice-versa. > > > > Honestly, this is the first time I've heard about a Linux FS having > > versioning other than a major one > > This is because, unlike other Linux file systems, reiser4 is a > framework. > > In vanilla kernel having a filesystem-as-framework is discouraged for > ideological reasons. As they explained: "nobody's interested in > plugins". A huge monolithic mess without any internal structure - > welcome :) I wouldn't call it an ideological problem, but more about wanting to assure interoperability issues and wanting to reduce confusion on the part of users, especially if images get moved between systems. There is also plenty of way of introducing internal structure and code cleanliness without going completely undisciplined with respect to on-disk format extensions. :-) Finally, I'll note that ext 2/3/4 does have a rather fine-grained set of feature flags, with specific rules about what the kernel --- and e2fsck --- should do if it finds a feature bit it doesn't understand in the incompat, ro_compat, and compat feature flags set. This is especially helpful since we have multiple implementations of ext 2/3/4 out there (in FreeBSD, the GRUB bootloader, GNU HURD, Fuchsia, etc.) and so using feature bits allow for safe and reliable interoperability with the user being warned if they can safely only mount the file system read-only, or not at all, if the file system has some new feature that their current OS version does not support. We can also give appropriate warnings if they are using an insufficiently recent version of the userspace tools. Cheers, - Ted
