From: Matthew Wilcox > From: Matthew Wilcox > > Heh, I was thinking about that too. The radix tree supports "exceptional > > entries" which have the bottom bit set. On a 64-bit machine, we could use > 62 > > of the bits in the radix tree root to store the ID bitmap. I'm a little > > wary of > the > > potential complexity, but we should try it out. > > Test patch here: http://git.infradead.org/users/willy/linux- > dax.git/shortlog/refs/heads/idr-2016-12-16 > It passes the test suite ... which I actually had to adjust because it now > succeeds > in cases where it hadn't (allocating ID 0 without preallocating), and it will > now > fail in cases where it hadn't previously (assuming a single preallocation > would > be enough). There shouldn't be any examples of that in the kernel proper; it > was simply me being lazy when I wrote the test suite.
Found a bug, committed a fix (and another test case). It now no longer returns -EAGAIN in situations where it wouldn't have, so I've reverted that bit of the test suite change. Still succeeds when it wouldn't have before, but I feel no pressure to change that ;-)
