Re: [RFC PATCH v2 1/2] vfs: syscalls: add mkdirat2() that returns an O_DIRECTORY fd

[Jeff Layton]

On Tue, 2026-04-28 at 07:39 +0100, Jeff Layton wrote:
> On Mon, 2026-04-27 at 17:48 +0200, Christian Brauner wrote:
> > 
> > 
> > And side-question: @Jeff, can nfs atomic open deal with O_CREAT |
> > O_DIRECTORY?
> > 
> 
> No, it can't. OPEN calls only work on regular files. This is why
> O_DIRECTORY works on NFS. If we end up issuing an OPEN against a
> directory, it'll fail, which is what we want in that situation.

To be clear, we could make that work by sending a second RPC:

    PUTFH+OPEN+....   (OPEN fails with NFS4ERR_ISDIR)

...and then send:

    PUTFH+CREATE...

...for a directory (which is how mkdir works in v4). If the calls race
with something else being created in its place, we could just open it
if it's a directory, or fail.
-- 
Jeff Layton <jlayton@xxxxxxxxxx>