linux-kernel - Re: [PATCH v2 1/3] mm/gup_benchmark: handle gup failures

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Message-ID: <CA+55aFywfktB83dERzYaC1NCYxD+Lg+NRft5ypjmbbcM_qdxpQ@mail.gmail.com>
Date:   Sat, 7 Apr 2018 13:08:43 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Huang Ying <ying.huang@...el.com>,
        Jonathan Corbet <corbet@....net>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Thorsten Leemhuis <regressions@...mhuis.info>,
        stable <stable@...r.kernel.org>, linux-mm <linux-mm@...ck.org>
Subject: Re: [PATCH v2 1/3] mm/gup_benchmark: handle gup failures

On Thu, Apr 5, 2018 at 2:03 PM, Michael S. Tsirkin <mst@...hat.com> wrote:
>
>                 nr = get_user_pages_fast(addr, nr, gup->flags & 1, pages + i);
> -               i += nr;
> +               if (nr > 0)
> +                       i += nr;

Can we just make this robust while at it, and just make it

        if (nr <= 0)
                break;

instead? Then it doesn't care about zero vs negative error, and
wouldn't get stuck in an endless loop if it got zero.

             Linus