linux-kernel - Re: [PATCH v26 2/5] fs/proc/task_mmu: Implement IOCTL to get and optionally clear info about PTEs

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Message-ID: <82de29db-85fc-0d44-ef41-3ccfe0d3d2c1@collabora.com>
Date:   Thu, 27 Jul 2023 16:49:36 +0500
From:   Muhammad Usama Anjum <usama.anjum@...labora.com>
To:     Michał Mirosław <emmir@...gle.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>,
        Andrei Vagin <avagin@...il.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,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>
Subject: Re: [PATCH v26 2/5] fs/proc/task_mmu: Implement IOCTL to get and
 optionally clear info about PTEs

On 7/27/23 4:46 PM, Michał Mirosław wrote:
> On Thu, 27 Jul 2023 at 11:37, Muhammad Usama Anjum
> <usama.anjum@...labora.com> wrote:
> [...]
>> --- a/include/uapi/linux/fs.h
>> +++ b/include/uapi/linux/fs.h
> [...]
>> +/*
>> + * struct pm_scan_arg - Pagemap ioctl argument
>> + * @size:              Size of the structure
>> + * @flags:             Flags for the IOCTL
>> + * @start:             Starting address of the region
>> + * @end:               Ending address of the region
>> + * @walk_end:          Ending address of the visited memory is returned
>> + *                     (This helps if entire range hasn't been visited)
> 
> "Address where the scan stopped (written by kernel). walk_end == end
> informs that the scan completed."
I'll update comment.

> 
> (To make the userspace life easier, we can copy `end` (only) in case
> of full scan completion, so that the tag is retained.)
Lets be consist and not copy tag from end to walk_end as we'll now know
about tag every time. It should be the responsibility of the user to deal
with it.

> 
>> + * @vec:               Address of page_region struct array for output
>> + * @vec_len:           Length of the page_region struct array
>> + * @max_pages:         Optional limit for number of returned pages (0 = disabled)
>> + * @category_inverted: PAGE_IS_* categories which values match if 0 instead of 1
>> + * @category_mask:     Skip pages for which any category doesn't match
>> + * @category_anyof_mask: Skip pages for which no category matches
>> + * @return_mask:       PAGE_IS_* categories that are to be reported in `page_region`s returned
>> + */

-- 
BR,
Muhammad Usama Anjum