Re: [PATCHv2 00/12] iov_iter: replace import_single_range with ubuf

[Jens Axboe <axboe@kernel.dk>]

On 1/5/23 12:07 PM, Keith Busch wrote:
> From: Keith Busch <kbusch@kernel.org>
> 
> ITER_UBUF is a more efficient representation when using single vector
> buffers, providing small optimizations over ITER_IOVEC. This series
> introduces a helper to set these up, and replaces all applicable users
> of import_single_range with the new helper. And since there are no
> single range users left after this change, the helper is no longer
> needed.
> 
> As noted in v1(*), there are some fundamental differences to how io_uring
> compares to read/write/readv/writev. There are only the two affected
> file_operations, and they already do not work with io_uring due to their
> diverging semantics for vectored vs non-vectored read/write. Therefore,
> this series having io_uring prefer ubuf iov_iter isn't introducing new
> breakage.

Pondering how to stage this, both for later upstream but also for
testing. Would probably make the best sense to stage 1-5 separately,
and then just punt the remaining ones to the appropriate subsystems.
And then 12/12 can go in when they have all been applied.

-- 
Jens Axboe