linux-kernel - Re: [PATCH v24 2/5] fs/proc/task_mmu: Implement IOCTL to get and optionally clear info about PTEs

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Message-ID: <2a4e523a-9d8d-5370-b6f0-f24505f0acea@collabora.com>
Date:   Wed, 12 Jul 2023 08:16:34 +0500
From:   Muhammad Usama Anjum <usama.anjum@...labora.com>
To:     Andrei Vagin <avagin@...il.com>
Cc:     Muhammad Usama Anjum <usama.anjum@...labora.com>,
        Peter Xu <peterx@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michał Mirosław 
        <emmir@...gle.com>, Danylo Mocherniuk <mdanylo@...gle.com>,
        Paul Gofman <pgofman@...eweavers.com>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Mike Rapoport <rppt@...nel.org>, Nadav Amit <namit@...are.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Shuah Khan <shuah@...nel.org>,
        Christian Brauner <brauner@...nel.org>,
        Yang Shi <shy828301@...il.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Liam R . Howlett" <Liam.Howlett@...cle.com>,
        Yun Zhou <yun.zhou@...driver.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Alex Sierra <alex.sierra@....com>,
        Matthew Wilcox <willy@...radead.org>,
        Pasha Tatashin <pasha.tatashin@...een.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        "Gustavo A . R . Silva" <gustavoars@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, linux-kselftest@...r.kernel.org,
        Greg KH <gregkh@...uxfoundation.org>, kernel@...labora.com
Subject: Re: [PATCH v24 2/5] fs/proc/task_mmu: Implement IOCTL to get and
 optionally clear info about PTEs

On 7/12/23 12:42 AM, Andrei Vagin wrote:
> On Tue, Jul 11, 2023 at 5:53 AM Muhammad Usama Anjum
> <usama.anjum@...labora.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 = (end - addr)/PAGE_SIZE;
>> +       struct pagemap_scan_private *p = walk->private;
>> +       struct vm_area_struct *vma = walk->vma;
>> +       int ret = 0;
>> +
>> +       if (!vma)
>> +               return 0;
>> +
>> +       if (IS_PM_SCAN_GET(p->flags)) {
>> +               if (n_pages > p->max_pages - p->found_pages)
>> +                       n_pages = p->max_pages - p->found_pages;
>> +
>> +               ret = pagemap_scan_output(PM_SCAN_FLAGS(false, false, false,
>> +                                         false, false), p, addr, n_pages);
> 
> Why do we report holes unconditionally?
It seems I've missed the filtering part for holes. It got missed and no
test/reviewer caught it earlier. I'll add it pretty quickly.

Are you satisfied with the remaining patch and can you sent reviewed/acked
by tag?

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

-- 
BR,
Muhammad Usama Anjum