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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B9894C001B0 for ; Tue, 8 Aug 2023 20:25:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234725AbjHHUZJ (ORCPT ); Tue, 8 Aug 2023 16:25:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46966 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234298AbjHHUYx (ORCPT ); Tue, 8 Aug 2023 16:24:53 -0400 Received: from madras.collabora.co.uk (madras.collabora.co.uk [IPv6:2a00:1098:0:82:1000:25:2eeb:e5ab]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C8844A273; Tue, 8 Aug 2023 12:35:13 -0700 (PDT) Received: from [192.168.100.7] (unknown [59.103.218.230]) (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 34A2F66071EF; Tue, 8 Aug 2023 20:35:06 +0100 (BST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1691523311; bh=1+Z3o6x/w64sAUDuV9BLbfjMD1tjNE9ITcvlYGSrFCA=; h=Date:Cc:Subject:To:References:From:In-Reply-To:From; b=GVGRPRGg5bp00TFStvcTgcHZrdGu8CbEKIX5GK/131gbeAjlAmTXBtZcbhXbokZea t0Xv5kj5mdk7PGNoj3x0Kxg3g8rYoeQd0mHjbIrMA/rgo7jn9LxTJDOCzZrH8tjtbH 1CIrJrH9949atBbLsdw+B3zQx6SvGIsy3uF0oxuJvZ6mZXUbpO9qTuXMeqL6gUzzEI t9AiryugpvDYuOGgz2irZV5t3lJPd9gLxleRhsbhrT0hdBiFQBoZ/ipQksYAn/8LQB QCZtrHXClSEdpc2wOVjNtgiUXupXIbxcKiMPNLalFZeJc043XSF9VemqVmryFnzlve UyVJfg11YPk3w== Message-ID: <624cfa26-5650-ee0d-8e0a-1d844175bcaf@collabora.com> Date: Wed, 9 Aug 2023 00:35:01 +0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.13.1 Cc: Muhammad Usama Anjum , Peter Xu , David Hildenbrand , Andrew Morton , =?UTF-8?B?TWljaGHFgiBNaXJvc8WC?= =?UTF-8?Q?aw?= , Danylo Mocherniuk , Paul Gofman , Cyrill Gorcunov , Mike Rapoport , Nadav Amit , Alexander Viro , Shuah Khan , Christian Brauner , Yang Shi , Vlastimil Babka , "Liam R . Howlett" , Yun Zhou , Suren Baghdasaryan , Alex Sierra , Matthew Wilcox , Pasha Tatashin , 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, =?UTF-8?B?TWljaGHFgiBNaXJvc8WCYXc=?= Subject: Re: [PATCH v27 2/6] fs/proc/task_mmu: Implement IOCTL to get and optionally clear info about PTEs To: Andrei Vagin References: <20230808104309.357852-1-usama.anjum@collabora.com> <20230808104309.357852-3-usama.anjum@collabora.com> Content-Language: en-US From: Muhammad Usama Anjum In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/9/23 12:21 AM, Andrei Vagin wrote: > On Tue, Aug 8, 2023 at 3:43 AM Muhammad Usama Anjum > wrote: > > .... > >> +static int pagemap_scan_output(unsigned long categories, >> + struct pagemap_scan_private *p, >> + unsigned long addr, unsigned long *end) >> +{ >> + unsigned long n_pages, total_pages; >> + int ret = 0; >> + >> + if (!p->vec_buf) >> + return 0; >> + >> + categories &= p->arg.return_mask; >> + >> + n_pages = (*end - addr) / PAGE_SIZE; >> + if (check_add_overflow(p->found_pages, n_pages, &total_pages) || //TODO > > Need to fix this TODO. Sorry, I forgot to remove the "//TODO". As far as I've understood, the last discussion ended in keeping the check_add_overflow(). [1] I'll just remove the TODO. https://lore.kernel.org/all/CABb0KFEfmRz+Z_-7GygTL12E5Y254dvoUfWe4uSv9-wOx+Cs8w@mail.gmail.com > >> + total_pages > p->arg.max_pages) { >> + size_t n_too_much = total_pages - p->arg.max_pages; >> + *end -= n_too_much * PAGE_SIZE; >> + n_pages -= n_too_much; >> + ret = -ENOSPC; >> + } >> + >> + if (!pagemap_scan_push_range(categories, p, addr, *end)) { >> + *end = addr; >> + n_pages = 0; >> + ret = -ENOSPC; >> + } >> + >> + p->found_pages += n_pages; >> + if (ret) >> + p->walk_end_addr = *end; >> + >> + return ret; >> +} >> + > > ... > >> +static long do_pagemap_scan(struct mm_struct *mm, unsigned long uarg) >> +{ >> + struct mmu_notifier_range range; >> + struct pagemap_scan_private p; >> + unsigned long walk_start; >> + size_t n_ranges_out = 0; >> + int ret; >> + >> + memset(&p, 0, sizeof(p)); >> + ret = pagemap_scan_get_args(&p.arg, uarg); >> + if (ret) >> + return ret; >> + >> + p.masks_of_interest = MASKS_OF_INTEREST(p.arg); >> + ret = pagemap_scan_init_bounce_buffer(&p); >> + if (ret) >> + return ret; >> + >> + /* Protection change for the range is going to happen. */ >> + if (p.arg.flags & PM_SCAN_WP_MATCHING) { >> + mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_VMA, 0, >> + mm, p.arg.start, p.arg.end); >> + mmu_notifier_invalidate_range_start(&range); >> + } >> + >> + walk_start = p.arg.start; >> + for (; walk_start < p.arg.end; walk_start = p.arg.walk_end) { >> + int n_out; >> + >> + if (fatal_signal_pending(current)) { >> + ret = -EINTR; >> + break; >> + } >> + >> + ret = mmap_read_lock_killable(mm); >> + if (ret) >> + break; >> + ret = walk_page_range(mm, walk_start, p.arg.end, >> + &pagemap_scan_ops, &p); >> + mmap_read_unlock(mm); >> + >> + n_out = pagemap_scan_flush_buffer(&p); >> + if (n_out < 0) >> + ret = n_out; >> + else >> + n_ranges_out += n_out; >> + >> + if (ret != -ENOSPC || p.arg.vec_len - 1 == 0 || >> + p.found_pages == p.arg.max_pages) { >> + p.walk_end_addr = p.arg.end; > > You should not change p.walk_end_addr If ret is ENOSPC. Pls add a test > case to check this. Yeah, I'm not setting walk_end_addr if ret is ENOSPC. I'm setting walk_end_addr only when ret = 0. I'd added this as a result of a test case in my local test application. I can look at adding some tests in pagemap_ioctl.c kselftest as well. > >> + break; >> + } >> + } >> + >> + if (p.cur_buf.start != p.cur_buf.end) { >> + if (copy_to_user(p.vec_out, &p.cur_buf, sizeof(p.cur_buf))) >> + ret = -EFAULT; >> + else >> + ++n_ranges_out; >> + } >> + >> + /* ENOSPC signifies early stop (buffer full) from the walk. */ >> + if (!ret || ret == -ENOSPC) >> + ret = n_ranges_out; >> + >> + p.arg.walk_end = p.walk_end_addr ? p.walk_end_addr : walk_start; >> + if (pagemap_scan_writeback_args(&p.arg, uarg)) >> + ret = -EFAULT; >> + >> + if (p.arg.flags & PM_SCAN_WP_MATCHING) >> + mmu_notifier_invalidate_range_end(&range); >> + >> + kfree(p.vec_buf); >> + return ret; >> +} > > Thanks, > Andrei -- BR, Muhammad Usama Anjum