Re: [PATCH v5 03/12] Turn fault_in_pages_{readable,writeable} into fault_in_{readable,writeable}

[Al Viro]

On Tue, Aug 03, 2021 at 09:18:09PM +0200, Andreas Gruenbacher wrote:
> Turn fault_in_pages_{readable,writeable} into versions that return the number
> of bytes faulted in instead of returning a non-zero value when any of the
> requested pages couldn't be faulted in.  This supports the existing users that
> require all pages to be faulted in, but also new users that are happy if any
> pages can be faulted in.
> 
> Neither of these functions is entirely trivial and it doesn't seem useful to
> inline them, so move them to mm/gup.c.
> 
> Rename the functions to fault_in_{readable,writeable} to make sure that code
> that uses them can be fixed instead of breaking silently.

Sigh...  We'd already discussed that; it's bloody pointless.  Making short
fault-in return success - absolutely.  Reporting exact number of bytes is
not going to be of any use to callers.

Please, don't.