Re: btrfs_direct_IO oops

[Al Viro]

On Sat, Oct 08, 2016 at 02:08:06PM -0400, Dave Jones wrote:
> That code: matches this dissembly:
> 
>                 for (i = seg + 1; i < iter->nr_segs; i++) {

*whoa*

OK, that loop in check_direct_IO() should be done *ONLY* for
iovec iter - even for a bvec one it's completely bogus, and
for pipe ones it blows up immediately.

Sorry, I'd missed that bogosity - replace
        if (iov_iter_rw(iter) == WRITE)
		return 0;
with
	if (iov_iter_rw(iter) != READ || !iter_is_iovec(iter))
		return 0;
in there; that should fix the damn thing.