On Tue, Jun 20, 2017 at 06:51:34AM -0600, Jens Axboe wrote:

That sounds fragile... Is it really worth it to avoid stealing three
bits in the inode? Do we have buffer_heads attached everywhere, that
sounds surprising to me.

I'm not concerned about saving a few bits - we'll use those elsewhere
anyway.  I'm concerned about settings on one file descriptor having
an effect on other fds that doesn't look intended.  It's not the
end of the world, as multiple writers to the same file should
better be aware of each other, but the semantics of setting these
on a per-inode level still stink.