On Tue, Dec 15, 2020 at 11:14:20AM +0000, Pavel Begunkov wrote: > On 15/12/2020 01:41, Ming Lei wrote: > > On Tue, Dec 15, 2020 at 12:20:19AM +0000, Pavel Begunkov wrote: > >> Instead of creating a full copy of iter->bvec into bio in direct I/O, > >> the patchset makes use of the one provided. It changes semantics and > >> obliges users of asynchronous kiocb to track bvec lifetime, and [1/6] > >> converts the only place that doesn't. > > > > Just think of one corner case: iov_iter(BVEC) may pass bvec table with zero > > length bvec, which may not be supported by block layer or driver, so > > this patchset has to address this case first. > > The easiest for me would be to fallback to copy if there are zero bvecs, > e.g. finding such during iov_iter_alignment(), but do we know from where > zero bvecs can came? As it's internals we may want to forbid them if > there is not too much hassle. You may find clue from the following link: https://www.mail-archive.com/linux-kernel@xxxxxxxxxxxxxxx/msg2262077.html Thanks, Ming
