Re: [PATCH] mm/gup.c: Handle error at earliest for incorrect nr_pages value

[Andrew Morton]

On Fri,  1 May 2020 01:41:58 +0530 Souptick Joarder <jrdr.linux@xxxxxxxxx> wrote:

> As per documentation, pin_user_pages_fast() & get_user_pages_fast()
> will return 0, if nr_pages <= 0. But this can be figure out only after
> going inside the internal_get_user_pages_fast().
> 
> This can be handled early. Adding a check for the same.

Calling get_user_pages() for (nrpages <= 0) is a nonsensical thing to
do so it isn't a thing we should care to optimize.  Adding new checks
will actually slow down the use cases which we *do* care about.  And it
adds more code.