Re: [PATCH v3 1/7] iov_iter: Introduce fault_in_iov_iter helper

[Andreas Grünbacher]

Am Sa., 24. Juli 2021 um 03:53 Uhr schrieb Al Viro <viro@xxxxxxxxxxxxxxxxxx>:
> On Fri, Jul 23, 2021 at 10:58:34PM +0200, Andreas Gruenbacher wrote:
> > Introduce a new fault_in_iov_iter helper for manually faulting in an iterator.
> > Other than fault_in_pages_writeable(), this function is non-destructive.
> >
> > We'll use fault_in_iov_iter in gfs2 once we've determined that the iterator
> > passed to .read_iter or .write_iter isn't in memory.
>
> Hmm...  I suspect that this is going to be much heavier for read access
> than the existing variant.  Do we ever want it for anything other than
> writes?

I don't know if it actually is slower when pages need to be faulted
in, but I'm fine turning it into a write-only function.

Thanks,
Andreas