Re: [PATCH][RFC] open_tree(2) (was Re: [PATCH 30/32] vfs: Allow cloning of a mount tree with open(O_PATH|O_CLONE_MOUNT) [ver #8])
From: Matthew Wilcox
Date: Mon Jun 04 2018 - 13:16:37 EST
On Sun, Jun 03, 2018 at 01:55:37AM +0100, Al Viro wrote:
> +SYSCALL_DEFINE3(open_tree, int, dfd, const char *, filename, unsigned, flags)
> +{
> + struct file *file;
> + struct path path;
> + int lookup_flags = LOOKUP_AUTOMOUNT | LOOKUP_FOLLOW;
> + bool detached = flags & OPEN_TREE_CLONE;
> + int error;
> + int fd;
> +
> + BUILD_BUG_ON(OPEN_TREE_CLOEXEC != O_CLOEXEC);
Why do we need OPEN_TREE_CLOEXEC? Wouldn't we be better off just making
the fd returned by open_tree implicitly close-on-exec? I can think of
no good reason for these file descriptors to be inherited across exec()
and if someone comes up with such a reason, fcntl(F_SETFD) is not an
expensive call to make.