Streams support in Linux

[Al Viro]

On Sat, Aug 25, 2018 at 01:57:16PM -0700, Matthew Wilcox wrote:

> > > Right, but that code also assumes it's dealing with files.
> > 
> > I'm looking forward to your analysis of all code related to dentry tree,
> > with an eye towards the places where such asserts are quietly made...
> 
> I really was hoping not to change the dentry tree at all.

Umhm...  Just what, pray tell, would be used to hold the stream name when
you are creating/removing/renaming it?  And why are we talking about the
use of existing syscalls for that thing?  In effect, you are multiplexing
entirely new syscalls, with different pathname resolution, etc. upon the
existing ones, using that new AT_... flag to select them.

Better yet, you need some new objects to represent those things, since
you don't want any informative dentries.  And not fs-private ones, at
that, since those new syscalls of yours would have to operate on them
(after all, renaming something opened would probably be expected to
have the opened descriptor to keep accessing the same object, wouldn't
it?)