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

[Matthew Wilcox]

On Sun, Sep 24, 2023 at 02:47:42PM +0300, Amir Goldstein wrote:
> Since you joined the discussion, you have the opportunity to agree or
> disagree with our decision to change readahead() to ESPIPE.
> Judging  by your citing of lseek and posix_fadvise standard,
> I assume that you will be on board?

I'm fine with returning ESPIPE (it's like ENOTTY in a sense).  but
that's not what kbuild reported:

readahead01.c:62: TFAIL: readahead(fd[0], 0, getpagesize()) succeeded

61:	fd[0] = SAFE_SOCKET(AF_INET, SOCK_STREAM, 0);
62:	TST_EXP_FAIL(readahead(fd[0], 0, getpagesize()), EINVAL);

I think LTP would report 'wrong error code' rather than 'succeeded'
if it were returning ESPIPE.

I'm not OK with readahead() succeeding on a socket.  I think that should
also return ESPIPE.  I think posix_fadvise() should return ESPIPE on a
socket too, but reporting bugs to the Austin Group seems quite painful.
Perhaps somebody has been through this process and can do that for us?