[LTP] [PATCH v3] vfs: fix readahead(2) on block devices

[Cyril Hrubis]

Hi!
> I realise we could add new test cases _basically_ forever, but I'd like
> to see a little more coverage in test_invalid_fd().  It currently tests
> both pipes and sockets, but we have so many more fd types.  Maybe there
> are good abstractions inside LTP already for creating these?  I'd
> like to see tests that the following also return -EINVAL:
> 
>  - an io_uring fd
>  - /dev/zero
>  - /proc/self/maps (or something else in /proc we can get unprivileged
>    access to)
>  - a directory (debatable!  maybe we should allow prefetching a
>    directory!)

This sounds like a good idea. We do have an API to iterate over
filesystems but not API to iterate over file descriptors, I suppose that
we will need an enum with fd type passed along with the file descriptor
so that we can set the expectations right and then just define a
function that would take the structure and do the test, something as:

enum tst_fd_type {
	TST_FD_IO_URING,
	TST_FD_DEV_ZERO,
	TST_FD_PROC_MAPS,
	...
};

struct tst_fd {
	enum tst_fd_type type;
	int fd;
};

static void test_fd(struct tst_fd *fd)
{
	if (fd->type == TST_FD...)
		TST_EXP_PASS(...);
	else
		TST_EXP_FAIL(...);
}

I can add something like this once we are done with the September LTP
release.

-- 
Cyril Hrubis
chrubis@suse.cz