On Thu, Mar 30, 2017 at 9:33 AM, Christoph Hellwig <hch@xxxxxx> wrote: This really harms > when adding new flags, because applications can't just probe for the > flag to actually work. Side note: this whole argument is also incredibly idiotic from the very beginning, regardless of the backwards compatibility issue. But probing for flags is why we *could* add things like O_NOATIME etc - exactly because it "just worked" with old kernels, and people could just use the new flags knowing that it was a no-op on old kernels. The whole concept of "probing for supported features" is very suspect. It's a bad bad idea. Don't do it. What kind of new flag did you even have in mind that would have such broken semantics that it would completely change the other flags? Becuase now I'm starting to think that the whole series has an even deeper bug: stupid new features that were badly thought out and not even described. Linus -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html