From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 69AC1C636CC for ; Mon, 13 Feb 2023 10:45:04 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id CF5566B0073; Mon, 13 Feb 2023 05:45:03 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id CA5426B0074; Mon, 13 Feb 2023 05:45:03 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B46B66B0075; Mon, 13 Feb 2023 05:45:03 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id A53CF6B0073 for ; Mon, 13 Feb 2023 05:45:03 -0500 (EST) Received: from smtpin16.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 764D2140434 for ; Mon, 13 Feb 2023 10:45:03 +0000 (UTC) X-FDA: 80461936086.16.4EE5BB9 Received: from madras.collabora.co.uk (madras.collabora.co.uk [46.235.227.172]) by imf08.hostedemail.com (Postfix) with ESMTP id A0035160018 for ; Mon, 13 Feb 2023 10:45:01 +0000 (UTC) Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=collabora.com header.s=mail header.b=DkbzWwYh; dmarc=pass (policy=reject) header.from=collabora.com; spf=pass (imf08.hostedemail.com: domain of usama.anjum@collabora.com designates 46.235.227.172 as permitted sender) smtp.mailfrom=usama.anjum@collabora.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1676285101; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=UxUCVP2kaoQ8QhfqbxQlS0pwCsPWvayFz3uKXUMUrRc=; b=mMh3c60x2g5DRDRfvFIV46a6t1/hU4kqpMtsYgpidVighqMYJLljC9BpG2Yd4LfPewf91b 3096sV4VdNxHzIMExxw+/JzTvQvP6c1TKw6BzGNWWdNSbbecD8Mpsfv5/0maf/4qGgC6zZ b+mptj5cDDieB+0LCwddxT3rhinJucQ= ARC-Authentication-Results: i=1; imf08.hostedemail.com; dkim=pass header.d=collabora.com header.s=mail header.b=DkbzWwYh; dmarc=pass (policy=reject) header.from=collabora.com; spf=pass (imf08.hostedemail.com: domain of usama.anjum@collabora.com designates 46.235.227.172 as permitted sender) smtp.mailfrom=usama.anjum@collabora.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1676285101; a=rsa-sha256; cv=none; b=Yp5wt/D/mv72vx1h6QSmbPXg+PbxzCZcpqdpZVTVexrjet1T/DC4+FuhXg50/gD564zb3K d680Oz6bsgBkjtnr9ep6zClohowasMI+dHRnEqxQO3cF4wMEg4N3FgHQD7/KjKJDgZ3wF2 s8i/mbeCcmrKP/G2mipGd03lp+Zgk4U= Received: from [192.168.10.12] (unknown [39.45.179.179]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: usama.anjum) by madras.collabora.co.uk (Postfix) with ESMTPSA id 52B43660210A; Mon, 13 Feb 2023 10:44:53 +0000 (GMT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1676285100; bh=rFkR6He2/D7jQAmT+MR3vtWZDzSsN2bw42gGtGr6rVg=; h=Date:Cc:Subject:To:References:From:In-Reply-To:From; b=DkbzWwYhAeY8Fk994zFJ9wdOCf6fh4VbSbfaGFd+KnglkqtWyNTpCG3nUy4+Wwzxf ql7ZNTdPN6jsOIFVpIqvT0KD/diMMHPupvPM7y3WBaiJje7xAO03ZBmidGzFOrA18s 7fgmPgLtrQAkfjthYcyWCMRkHCw3k1SoBytBa/fz+wdAHs6o6iJbLPwaaIKdDmW3VL oFM943VJWOS0IpZDvwLbHaJhbrceTDF0dQu1lGm4Pq2dljtZOY8KcmJKFgN6gq58mb 1HQMRZ4rPbyUHn6ragP+qxa/Dycyu9MuvHCK0zJQn9r3oBE4tzojh0ki07JY+7g+JX 61rJmBeKnE+wg== Message-ID: <83382901-6d0b-b38f-27cd-3a45259eee85@collabora.com> Date: Mon, 13 Feb 2023 15:44:48 +0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.7.1 Cc: Muhammad Usama Anjum , David Hildenbrand , Andrew Morton , =?UTF-8?B?TWljaGHFgiBNaXJvc8WC?= =?UTF-8?Q?aw?= , Andrei Vagin , Danylo Mocherniuk , Paul Gofman , Cyrill Gorcunov , Alexander Viro , Shuah Khan , Christian Brauner , Yang Shi , Vlastimil Babka , "Liam R . Howlett" , Yun Zhou , Suren Baghdasaryan , Alex Sierra , Matthew Wilcox , Pasha Tatashin , Mike Rapoport , Nadav Amit , Axel Rasmussen , "Gustavo A . R . Silva" , Dan Williams , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, Greg KH , kernel@collabora.com Subject: Re: [PATCH v10 5/6] mm/pagemap: add documentation of PAGEMAP_SCAN IOCTL Content-Language: en-US To: Peter Xu References: <20230202112915.867409-1-usama.anjum@collabora.com> <20230202112915.867409-6-usama.anjum@collabora.com> From: Muhammad Usama Anjum In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: A0035160018 X-Rspamd-Server: rspam09 X-Rspam-User: X-Stat-Signature: xs9b3tmxc45seqhz5pfaqrb8h81k8weo X-HE-Tag: 1676285101-743780 X-HE-Meta: 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 G102Y/r7 4W5yENMEzKRJtR872TWp35mEbpxWk3bNY6WqX1IBa92BBLtyWOHt144Ikthr7RSiYJEzR9w51PZI0xEpA4o2IcvtH2gJKu4kyNtMyDxkv31zOiFa+4NQcV5dU3Pj/GqOi0sZatZPKgQxGUgC/E4JfL4yJbaed67qxdas/IA02PjT5jIawu9arfOsrM4Mxm/Kzo6D3lROGsUC19TCQzEK5roJ+sEd1kRnhKrT9CZ+FolDEZ5/TaBnP6MOA8Z2VYDUsofTmT8mReGy926I4zJyodBsDzDUTospHOC5ARPvJG4P+tynp4P9nioQPW8wclh+azR7a X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2/10/23 12:26 AM, Peter Xu wrote: > On Thu, Feb 02, 2023 at 04:29:14PM +0500, Muhammad Usama Anjum wrote: >> Add some explanation and method to use write-protection and written-to >> on memory range. >> >> Signed-off-by: Muhammad Usama Anjum >> --- >> Documentation/admin-guide/mm/pagemap.rst | 24 ++++++++++++++++++++++++ >> 1 file changed, 24 insertions(+) >> >> diff --git a/Documentation/admin-guide/mm/pagemap.rst b/Documentation/admin-guide/mm/pagemap.rst >> index 6e2e416af783..1cb2189e9a0d 100644 >> --- a/Documentation/admin-guide/mm/pagemap.rst >> +++ b/Documentation/admin-guide/mm/pagemap.rst >> @@ -230,3 +230,27 @@ Before Linux 3.11 pagemap bits 55-60 were used for "page-shift" (which is >> always 12 at most architectures). Since Linux 3.11 their meaning changes >> after first clear of soft-dirty bits. Since Linux 4.2 they are used for >> flags unconditionally. >> + >> +Pagemap Scan IOCTL >> +================== >> + >> +The ``PAGEMAP_SCAN`` IOCTL on the pagemap file can be used to get and/or clear >> +the info about page table entries. The following operations are supported in >> +this IOCTL: >> +- Get the information if the pages have been written-to (``PAGE_IS_WRITTEN``), >> + file mapped (``PAGE_IS_FILE``), present (``PAGE_IS_PRESENT``) or swapped >> + (``PAGE_IS_SWAPPED``). >> +- Write-protect the pages (``PAGEMAP_WP_ENGAGE``) to start finding which >> + pages have been written-to. >> +- Find pages which have been written-to and write protect the pages >> + (atomic ``PAGE_IS_WRITTEN + PAGEMAP_WP_ENGAGE``) > > Could we extend this section a bit more? Some points for reference: > > - The new struct you introduced, definitions of each of the fields, and > generic use cases for each of the field/ops. > > - It'll be nice to list the OPs the new interface supports (GET, > WP_ENGAGE, GET+WP_ENGAGE). > > - When should people use this rather than the old pagemap interface? > What's the major problems to solve / what's the major difference? > (Maybe nice to reference the Windows API too here) I'll update the documentation. > >> + >> +To get information about which pages have been written-to and/or write protect >> +the pages, following must be performed first in order: >> + 1. The userfaultfd file descriptor is created with ``userfaultfd`` syscall. >> + 2. The ``UFFD_FEATURE_WP_ASYNC`` feature is set by ``UFFDIO_API`` IOCTL. >> + 3. The memory range is registered with ``UFFDIO_REGISTER_MODE_WP`` mode >> + through ``UFFDIO_REGISTER`` IOCTL. >> +Then the any part of the registered memory or the whole memory region can be >> +write protected using the ``UFFDIO_WRITEPROTECT`` IOCTL or ``PAGEMAP_SCAN`` >> +IOCTL. > > This part looks good. > > Thanks, > -- BR, Muhammad Usama Anjum