Re: [PATCH 1/2] iov_iter: iterate_folioq: fix handling of offset >= folio size

David Howells wrote on Tue, Aug 12, 2025 at 10:34:17AM +0100:

asmadeus@codewreck.org wrote:

...

There should be a `if (slot == folioq_nr_slots(folioq)) break` check somewhere as well? Or is the iov_iter guaranteed to always 1/ have some data and 2/ either be big enough or have remaining data in a step?

We should handle both cases. I think the other iteration functions will. iov_iter_extractg_folioq_pages(), for example, wraps it in a conditional:

if (offset < fsize) {
	part = umin(part, umin(maxsize - extracted, fsize - offset));
	i->count -= part;
	i->iov_offset += part;
	extracted += part;

	p[nr++] = folio_page(folio, offset / PAGE_SIZE);
}

That's not what I pointed out just now; it doesn't check either if there is no slot left For example, an iov_iter with nr_slots = 4, slot = 4, folioq->next = NULL will happily trod on folioq->vec.folios[4] (folioq_folio(folioq, slot)) which is invalid