On Wed, Sep 06, 2023 at 09:06:21AM +1000, Dave Chinner wrote: > > Part 2: unmaintained file systems > > > > A lot of our file system drivers are either de facto or formally > > unmaintained. If we want to move the kernel forward by finishing > > API transitions (new mount API, buffer_head removal for the I/O path, > > ->writepage removal, etc) these file systems need to change as well > > and need some kind of testing. The easiest way forward would be > > to remove everything that is not fully maintained, but that would > > remove a lot of useful features. > > Linus has explicitly NACKed that approach. > > https://lore.kernel.org/linux-fsdevel/CAHk-=wg7DSNsHY6tWc=WLeqDBYtXges_12fFk1c+-No+fZ0xYQ@xxxxxxxxxxxxxx/ > > Which is a problem, because historically we've taken code into > the kernel without requiring a maintainer, or the people who > maintained the code have moved on, yet we don't have a policy for > removing code that is slowly bit-rotting to uselessness. > > > E.g. the hfsplus driver is unmaintained despite collecting odd fixes. > > It collects odd fixes because it is really useful for interoperating > > with MacOS and it would be a pity to remove it. At the same time > > it is impossible to test changes to hfsplus sanely as there is no > > mkfs.hfsplus or fsck.hfsplus available for Linux. We used to have > > one that was ported from the open source Darwin code drops, and > > I managed to get xfstests to run on hfsplus with them, but this > > old version doesn't compile on any modern Linux distribution and > > new versions of the code aren't trivially portable to Linux. > > > > Do we have volunteers with old enough distros that we can list as > > testers for this code? Do we have any other way to proceed? > > > > If we don't, are we just going to untested API changes to these > > code bases, or keep the old APIs around forever? > > We do slowly remove device drivers and platforms as the hardware, > developers and users disappear. We do also just change driver APIs > in device drivers for hardware that no-one is actually able to test. > The assumption is that if it gets broken during API changes, > someone who needs it to work will fix it and send patches. > > That seems to be the historical model for removing unused/obsolete > code from the kernel, so why should we treat unmaintained/obsolete > filesystems any differently? i.e. Just change the API, mark it > CONFIG_BROKEN until someone comes along and starts fixing it... Umm. If I change ->write_begin and ->write_end to take a folio, convert only the filesystems I can test via Luis' kdevops and mark the rest as CONFIG_BROKEN, I can guarantee you that Linus will reject that pull request. I really feel we're between a rock and a hard place with our unmaintained filesystems. They have users who care passionately, but not the ability to maintain them.
