Re: [PATCH] block: add bio_iov_iter_nvecs for figuring out nr_vecs

On Tue, Dec 01, 2020 at 12:52:51PM +0000, Matthew Wilcox wrote:

But the only reason we want to know 'nr_vecs' is so we can allocate a
BIO which has that many vecs, right?  But we then don't actually use the
vecs in the bio because we use the ones already present in the iter.
That was why I had it return 1, not nr_vecs.

Did I miss something?

Right now __bio_iov_bvec_add_pages does not reuse the bvecs in the
iter.  That being said while we are optmizing this path we might a well
look into reusing them..