[Ksummit-discuss] [TECH TOPIC] Getting better/supplementary error info back to userspace

[David Howells]

Linus Torvalds <torvalds at linux-foundation.org> wrote:

> But every time it comes up people ignore this basic issue:
> 
>      [torvalds at i7 linux]$ git grep -e '-E[A-Z]\{4\}' | wc -l
>      182523
> 
> 
> Give it up. It's really is a horrible idea for so many reasons.

Are you okay with me making it possible to retrieve mount errors, warnings and
informational messages through fd-arbitrated-mount I'm working on?  For
example (and skipping some of the parameters for brevity):

	int fs_fd;

	static inline void e(int x)
	{
		char buf[1024];
		int i;
		if (x == -1)
			fprintf(stderr, "Mount error: %m\n");
		/* Read back any messages */
		while (i = read(fs_fd, buf), i != -1) {
			buf[i] = 0;
			fprintf(stderr, "%s\n", buf);
		}
		if (x == -1)
			exit(1);
	}

	fs_fd = fsopen("ext4");
	e(write(fs_fd, "d /dev/sda3"));
	e(write(fs_fd, "o user_xattr"));
	e(write(fs_fd, "o acl"));
	e(write(fs_fd, "o data=ordered"));
	e(write(fs_fd, "x create"));
	e(fsmount(fs_fd, AT_FDCWD, "/mnt", MS_NODEV));
	close(fs_fd);

David