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References: <20230711125241.1587820-1-usama.anjum@collabora.com> <20230711125241.1587820-3-usama.anjum@collabora.com>
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From:   Andrei Vagin <avagin@gmail.com>
Date:   Tue, 11 Jul 2023 12:42:44 -0700
Message-ID: <CANaxB-zvYpKw-aeF8nd_spARdkV29H7ZJDDhusnmqOPZX1xXtw@mail.gmail.com>
Subject: Re: [PATCH v24 2/5] fs/proc/task_mmu: Implement IOCTL to get and
 optionally clear info about PTEs
To:     Muhammad Usama Anjum <usama.anjum@collabora.com>
Cc:     Peter Xu <peterx@redhat.com>, David Hildenbrand <david@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        =?UTF-8?B?TWljaGHFgiBNaXJvc8WCYXc=?= <emmir@google.com>,
        Danylo Mocherniuk <mdanylo@google.com>,
        Paul Gofman <pgofman@codeweavers.com>,
        Cyrill Gorcunov <gorcunov@gmail.com>,
        Mike Rapoport <rppt@kernel.org>, Nadav Amit <namit@vmware.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Shuah Khan <shuah@kernel.org>,
        Christian Brauner <brauner@kernel.org>,
        Yang Shi <shy828301@gmail.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        "Liam R . Howlett" <Liam.Howlett@oracle.com>,
        Yun Zhou <yun.zhou@windriver.com>,
        Suren Baghdasaryan <surenb@google.com>,
        Alex Sierra <alex.sierra@amd.com>,
        Matthew Wilcox <willy@infradead.org>,
        Pasha Tatashin <pasha.tatashin@soleen.com>,
        Axel Rasmussen <axelrasmussen@google.com>,
        "Gustavo A . R . Silva" <gustavoars@kernel.org>,
        Dan Williams <dan.j.williams@intel.com>,
        linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-mm@kvack.org, linux-kselftest@vger.kernel.org,
        Greg KH <gregkh@linuxfoundation.org>, kernel@collabora.com
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On Tue, Jul 11, 2023 at 5:53=E2=80=AFAM Muhammad Usama Anjum
<usama.anjum@collabora.com> wrote:

<snip>

> +static int pagemap_scan_pte_hole(unsigned long addr, unsigned long end,
> +                                int depth, struct mm_walk *walk)
> +{
> +       unsigned long n_pages =3D (end - addr)/PAGE_SIZE;
> +       struct pagemap_scan_private *p =3D walk->private;
> +       struct vm_area_struct *vma =3D walk->vma;
> +       int ret =3D 0;
> +
> +       if (!vma)
> +               return 0;
> +
> +       if (IS_PM_SCAN_GET(p->flags)) {
> +               if (n_pages > p->max_pages - p->found_pages)
> +                       n_pages =3D p->max_pages - p->found_pages;
> +
> +               ret =3D pagemap_scan_output(PM_SCAN_FLAGS(false, false, f=
alse,
> +                                         false, false), p, addr, n_pages=
);

Why do we report holes unconditionally?

> +       }
> +
> +       if (IS_PM_SCAN_WP(p->flags) &&
> +           uffd_wp_range(vma, addr, end - addr, true) < 0)
> +               ret =3D -EINVAL;
> +
> +       return ret;
> +}

Thanks,
Andrei