Re: [PATCH v3 2/2] iov_iter: Don't deal with iter->copy_mc in memcpy_from_iter_mc()

[David Howells]

David Laight <David.Laight@xxxxxxxxxx> wrote:

> 
> Couldn't the relevant code directly call __copy_from_iter_mc() ?
> Or a version then checked iov_is_copy_mc() and then fell
> back to the standard function.

No, because the marked iterator is handed by the coredump code to
__kernel_write_iter() and thence on to who-knows-what driver - which will call
copy_from_iter() or some such.  $DRIVER shouldn't need to know about
->copy_mc.

One thing I do wonder about, though, is what should happen if they call, say,
csum_and_copy_from_iter()?  That doesn't have an _mc variant.  Or what if they
extract the pages and operate directly on those?

David