Re: [PATCH/RFC] VFS: don't keep disconnected dentries on d_anon

From: Linus Torvalds
Date: Wed Dec 20 2017 - 19:57:37 EST

On Wed, Dec 20, 2017 at 2:45 PM, NeilBrown <neilb@xxxxxxxx> wrote:
> We could just leave the code unchanged, but apart from that being
> potentially confusing, the (unfair) bit-spin-lock which protects
> s_anon can become a bottle neck when lots of disconnected dentries are
> being created.
> So this patch renames s_anon to s_roots, and stops storing
> disconnected dentries on the list. Only dentries obtained with
> d_obtain_root() are now stored on this list. There are many fewer of
> these (only NFS and NILFS2 use the call, and only during filesystem
> mount) so contention on the bit-lock will not be a problem.

Thanks, Neil. This is much nicer than the magical special case patch
for s_anon bitlock.

Al, I'm going to assume I'll get this through your vfs tree (with
whatever edits from the comments people made).