linux-kernel - Re: [PATCH v33 2/6] fs/proc/task_mmu: Implement IOCTL to get and optionally clear info about PTEs

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Message-ID: <31981423-9edd-46b6-b5f8-17aae07b8336@collabora.com>
Date:   Mon, 28 Aug 2023 11:57:44 +0500
From:   Muhammad Usama Anjum <usama.anjum@...labora.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Muhammad Usama Anjum <usama.anjum@...labora.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,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Mike Rapoport <rppt@...nel.org>, Nadav Amit <namit@...are.com>,
        David Hildenbrand <david@...hat.com>,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>,
        Michał Mirosław <emmir@...gle.com>,
        Andrei Vagin <avagin@...il.com>,
        Danylo Mocherniuk <mdanylo@...gle.com>,
        Paul Gofman <pgofman@...eweavers.com>,
        Peter Xu <peterx@...hat.com>
Subject: Re: [PATCH v33 2/6] fs/proc/task_mmu: Implement IOCTL to get and
 optionally clear info about PTEs

On 8/21/23 7:15 PM, Muhammad Usama Anjum wrote:
> The PAGEMAP_SCAN IOCTL on the pagemap file can be used to get or optionally
> clear the info about page table entries. The following operations are
> supported in this IOCTL:
> - Scan the address range and get the memory ranges matching the provided
>   criteria. This is performed when the output buffer is specified.
> - Write-protect the pages. The PM_SCAN_WP_MATCHING is used to write-protect
>   the pages of interest. The PM_SCAN_CHECK_WPASYNC aborts the operation if
>   non-Async Write Protected pages are found. The ``PM_SCAN_WP_MATCHING``
>   can be used with or without PM_SCAN_CHECK_WPASYNC.
> - Both of those operations can be combined into one atomic operation where
>   we can get and write protect the pages as well.
> 
> Following flags about pages are currently supported:
> - PAGE_IS_WPALLOWED - Page has async-write-protection enabled
> - PAGE_IS_WRITTEN - Page has been written to from the time it was write protected
> - PAGE_IS_FILE - Page is file backed
> - PAGE_IS_PRESENT - Page is present in the memory
> - PAGE_IS_SWAPPED - Page is in swapped
> - PAGE_IS_PFNZERO - Page has zero PFN
> - PAGE_IS_HUGE - Page is THP or Hugetlb backed
> 
> This IOCTL can be extended to get information about more PTE bits. The
> entire address range passed by user [start, end) is scanned until either
> the user provided buffer is full or max_pages have been found.
> 
> Reviewed-by: Andrei Vagin <avagin@...il.com>
> Reviewed-by: Michał Mirosław <mirq-linux@...e.qmqm.pl>
> Signed-off-by: Michał Mirosław <mirq-linux@...e.qmqm.pl>
> Signed-off-by: Muhammad Usama Anjum <usama.anjum@...labora.com>
Now we have the reviewed-by tags as well. The reviewers are happy with
current version. Can you please have a look and possibly pick these up?

-- 
BR,
Muhammad Usama Anjum