Re: [PATCH v9 2/8] iov_iter: Add a function to extract a page list from an iterator

[David Howells]

John Hubbard <jhubbard@xxxxxxxxxx> wrote:

> > +	for (;;) {
> > +		if (i->nr_segs == 0)
> > +			return 0;
> > +		maxsize = min(maxsize, i->bvec->bv_len - skip);
> > +		if (maxsize)
> > +			break;
> > +		i->iov_offset = 0;
> > +		i->nr_segs--;
> > +		i->kvec++;
> > +		skip = 0;
> > +	}
> > +
> > +	skip += i->bvec->bv_offset;
> > +	page = i->bvec->bv_page + skip / PAGE_SIZE;
> > +	offset = skip % PAGE_SIZE;
> > +	*offset0 = offset;
> > +
> > +	maxpages = want_pages_array(pages, maxsize, offset, maxpages);
> > +	if (!maxpages)
> > +		return -ENOMEM;
> 
> Is it OK that the iov_iter position has been advanced, and left that way,
> in the case of an early -ENOMEM return here?

I think it should be okay.  The for-loop at the top just skips over empty
segments, so it doesn't really advance things.  There is an error there,
though: it should be i->bvec++, not i->kvec++ in the loop.

David