Re: [RFC][PATCHES] iov_iter.c rewrite

From: Al Viro
Date: Mon Dec 08 2014 - 14:28:41 EST

On Mon, Dec 08, 2014 at 10:57:31AM -0800, Linus Torvalds wrote:
> So the whole "get_page()" thing is broken. Iterating over pages in a
> KVEC is simply wrong, wrong, wrong. It needs to fail.

Well, _that_ is easy to do, of course... E.g. by replacing that thing in
iov_iter_get_pages()/iov_iter_get_pages_alloc() with ({ return -EFAULT; })
will do it.

> Iterating over a KVEC to *copy* data is ok. But no page lookup stuff
> or page reference things.
> The old code that apparently used "get_user_pages_fast()" was ok
> almost by mistake, because it fails on all kernel pages.

On x86 it does, but I don't see anything obvious in generic version in
mm/gup.c, so the old code might still have a problem on some architectures.
What am I missing here?
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at