Andy Lutomirski <l...@amacapital.net> wrote:
> Unless I'm rather confused, you have two or possibly three ways to
> pass in an open fd. Can you clarify what the difference is and/or
> remove all but one of them?
No, they're not equivalent.
> > (*) fsconfig_set_path: A non-empty path is specified. The parameter must
> > be expecting a path object. value points to a NUL-terminated string
> > that is the path and aux is a file descriptor at which to start a
> > relative lookup or AT_FDCWD.
So, an example:
fsconfig(fd, fsconfig_set_path, "source", "/dev/sda1", AT_FDCWD);
I don't want to require that the caller open /dev/sda1 and pass in an fd as
that might prevent the filesystem from "holding" it exclusively.
> > (*) fsconfig_set_path_empty: As fsconfig_set_path, but with AT_EMPTY_PATH
> > implied.
You can't do:
fsconfig(fd, fsconfig_set_path, "source", "", dir_fd);
because AT_EMPTY_PATH cannot be specified directly[*]. What you do instead is:
fsconfig(fd, fsconfig_set_path_empty, "source", "", dir_fd);
[*] Not without a 6-arg syscall or some other way of passing it.
I *could* require that the caller must call open(O_PATH) or openat(O_PATH)
before calling fsconfig() - so you don't pass a string, but only a path-fd.
> > (*) fsconfig_set_fd: An open file descriptor is specified. value must
> > be NULL and aux indicates the file descriptor.
See fd=%u on fuse. I think it's cleaner to do:
fsconfig(fd, fsconfig_set_fd, "source", NULL, control_fd);
saying explicitly that there's an open file to be passed rather than:
fsconfig(fd, fsconfig_set_path, "source", NULL, control_fd);
which indicates that you are actually providing a path.
David
