Re: [PATCH 0/3} Change ->mkdir() and vfs_mkdir() to return a dentry

[Al Viro]

On Fri, Feb 14, 2025 at 06:00:39AM +0000, Al Viro wrote:

> 3) I'm pretty sure that NFS is *not* the only filesystem that returns
> unhashed negative in some success cases; will need to go over the instances
> to verify that, though.

Definitely so: in cifs_mkdir() we have
        if ((server->ops->posix_mkdir) && (tcon->posix_extensions)) {
                rc = server->ops->posix_mkdir(xid, inode, mode, tcon, full_path,
                                              cifs_sb);
                d_drop(direntry); /* for time being always refresh inode info */
                goto mkdir_out;
        }
There might be other cases.  hostfs is definitely like that, I'm pretty
sure that kernfs is as well...