On Tue, Apr 16, 2024 at 04:23:43PM +0200, Lennart Poettering wrote: > On Di, 09.04.24 16:15, Christoph Hellwig (hch@xxxxxx) wrote: > 11;rgb:1717/1414/2121 > > On Tue, Apr 09, 2024 at 10:19:09AM +0200, Lennart Poettering wrote: > > > All I am looking for is a very simple test that returns me a boolean: > > > is there kernel-level partition scanning enabled on this device or > > > not. > > > > And we can add a trivial sysfs attribute for that. > > > > > At this point it's not clear to me if I can write this at all in > > > a way that works reasonably correctly on any kernel since let's say > > > 4.15 (which is systemd's "recommended baseline" right now). > > > > > > I am really not sure how to salvage this mess at all. AFAICS there's > > > currently no way to write such a test correctly. > > > > You can't. Maybe that's a lesson to not depend on undocumented internal > > flags exposed by accident by a weirdo interface. Just talk to > > people. > > Undocumented? Internal? > > It's was actually one of the *best* documented kernel *public* APIs I > ever came across: > > https://www.kernel.org/doc/html/v5.16/block/capability.html > > So much detail, I love it! > > I mean, you did good work here, documented it, with all flags in all > details. I think that's great work! You should take pride in this, not > try to deny its existance! The patch that introduced this was submitted not because the API was stable; it was committed to encourage developers to update it as it changed because it is *not* stable. That's not the kind of interface you want exported for users to rely on, but no one should have to search commit logs to understand why the doc exists, so I think exporting it was just a mistake on the kernel side. To say this doc is "good" misunderstands what it was trying to accomplish, and what it ultimately created instead: technical debt. The block interfaces documented in Documetation/ABI/stable/ are reliably stable, though.
