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]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id BC8C0C56205 for ; Thu, 6 Aug 2026 17:19:11 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9FFBD6B008A; Thu, 6 Aug 2026 13:19:10 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9D7306B0093; Thu, 6 Aug 2026 13:19:10 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8ECA86B0096; Thu, 6 Aug 2026 13:19:10 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 5DDD76B008A for ; Thu, 6 Aug 2026 13:19:10 -0400 (EDT) Received: from smtpin04.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay08.hostedemail.com (Postfix) with ESMTP id BEDF0140160 for ; Thu, 6 Aug 2026 17:19:09 +0000 (UTC) X-FDA: 85071505218.04.46E6D20 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf14.hostedemail.com (Postfix) with ESMTP id 8875F100011 for ; Thu, 6 Aug 2026 17:19:07 +0000 (UTC) Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=NOHtkX6M; spf=pass (imf14.hostedemail.com: domain of willy@infradead.org designates 90.155.50.34 as permitted sender) smtp.mailfrom=willy@infradead.org; dmarc=pass (policy=none) header.from=infradead.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1786036747; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=6oRZ7bVSXyuafN/Una/b4mH0BdxkEb9tpDXSUb5X6ns=; b=y32ycqLJLGp9U8vHm3IDEwf0hDxcsnT41obrBBMCqrS5yp7J7aNbK2Q+Vq9ipfXLKqsXuV EAm6O6yqiIuCyM+IVmQclDougNhx05XplK6W4OMQ9w/FoaEMQ5H4O+tu3qXLnb8n+l0pdA te9Ij5nvnqCqg4gSo5jJ7R37/LH0SJU= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1786036747; b=D/S+JcTdeZCo20yEVXLg4PllFrPxfne3GzBWHv2a5h/EqqtHG66krD9VczuVz1SXygQQSr 6EW/pXfLxhMS4BSVFSvm5XDWR4Hc61jSncaz7dSureXYwOm2tHlozeU3yn3qCtghRztIgu 8v8iQhLA9ybh7B+9nEoFKqqURjqyvuI= ARC-Authentication-Results: i=1; imf14.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=NOHtkX6M; spf=pass (imf14.hostedemail.com: domain of willy@infradead.org designates 90.155.50.34 as permitted sender) smtp.mailfrom=willy@infradead.org; dmarc=pass (policy=none) header.from=infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=6oRZ7bVSXyuafN/Una/b4mH0BdxkEb9tpDXSUb5X6ns=; b=NOHtkX6MmsJFk0WyudbePHVb+Z ifpcELU49/bxvCXnPyti3zMDsf3vrEU1uxAk5TYIm/D1FmsoElU2FUYaQQhQ4LoovHo3rp7Vne63J YaH62vM9cItZaSIxWJvPMTb1bbL31lHBb0Cf1CDgA8fCz7g0C5l3D9Iv+z7K/HEZOk3iw5NNU2Q5w XWkjd05TJgdOjBOzSepKpZBB9dAo9D9Tq9Btj3KmOmB3/bcy+aFEvpv1v4RfKmy2Y8w71xUI4dBbm aLBAQDqgpuzc2KJRh2DXEL8L92qWHYySh/ECP6u6w7N7KhG1J+RoXQcK8AMm7hkIB1Cn6XNWew/k9 8Zw2AsQg==; Received: from willy by casper.infradead.org with local (Exim 4.99.1 #2 (Red Hat Linux)) id 1ws1Mg-0000000CA8T-02wp; Thu, 06 Aug 2026 16:54:42 +0000 Date: Thu, 6 Aug 2026 17:54:41 +0100 From: Matthew Wilcox To: "Lorenzo Stoakes (ARM)" Cc: Gregory Price , "David Hildenbrand (Arm)" , Andrew Morton , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Pedro Falcato , Jan Kara , Miaohe Lin , Naoya Horiguchi , Rik van Riel , Harry Yoo , Lance Yang , Kees Cook , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Usama Arif , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Ying Huang , Alistair Popple , Peter Xu , Xu Xin , Chengming Zhou , Arnd Bergmann , Greg Kroah-Hartman , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH v3 04/15] mm: update print_bad_page_map() to show anonymous page index Message-ID: References: <20260729-b4-scalable-cow-virt-pgoff-v3-0-e8ecfefea812@kernel.org> <20260729-b4-scalable-cow-virt-pgoff-v3-4-e8ecfefea812@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 8875F100011 X-Rspamd-Server: rspam10 X-Rspam-User: X-Stat-Signature: zmuhhyxg1bh18yidj6ozfhxfnh6oxsjw X-HE-Tag: 1786036747-657854 X-HE-Meta: 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 hSYZZR5w 87KXIpkrvuWhjB+IimbL5y5Nya6ROXZiMKOX0MCPr8e77frQdjOc3z5kZ+f6i/xMUc8L6diBS7WGs81EqDSZMjPN5veqED6rdMVnRTcQg+kSxwcJZ9a3wUI6t+TMYG0SUwRYJNmbVHUPeC9DvzqYt+zeuCN4NVrQPF94QdpCCvt2YZSIst9ruCDSCdYJBslvn5V8AjRxEOWoZS2eJgPMJ58XMfJp5/seHSHux6iB1wtjtdN61BK8ZrA5CYSf9gE781hxnD3XHEz2h54kXlPmUTa4/U5Gg1/GI7b5K50Ab7tyWSBf8GwBrmOkojVLxaUebrACQPopxLgMFmMx6Px2uluLi51ijQ7GnkOVX0FGMqgUnTIH0yf7KrVBo14WXS9ppCS06XWna+dTLilQ= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Aug 05, 2026 at 10:01:43AM +0100, Lorenzo Stoakes (ARM) wrote: > On Wed, Aug 05, 2026 at 04:30:18AM -0400, Gregory Price wrote: > > Yeah just an F/A in the print I suppose. Sorry if that was unclear. > > > > If it saves someone the head-scratch of whether some bug is because it's > > "file" or "true anon", given the ambiguity here, seems like maybe useful > > debug information. > > Yeah will do on respin I think actually! > > I do think not providing that could result in some confusion like 'hm I > thought this was file-backed'. not sure it would. Look at the whole thing: pr_alert("BUG: Bad page map in process %s %s:%08llx", current->comm, pgtable_level_to_str(level), entry); __print_bad_page_map_pgtable(vma->vm_mm, addr); if (page) dump_page(page, "bad page map"); pr_alert("addr:%px vm_flags:%08lx anon_vma:%px mapping:%px index:%lx\n", (void *)addr, vma->vm_flags, vma->anon_vma, mapping, index); pr_alert("file:%pD fault:%ps mmap:%ps mmap_prepare: %ps read_folio:%ps\n", vma->vm_file, vma->vm_ops ? vma->vm_ops->fault : NULL, vma->vm_file ? vma->vm_file->f_op->mmap : NULL, vma->vm_file ? vma->vm_file->f_op->mmap_prepare : NULL, mapping ? mapping->a_ops->read_folio : NULL); even if we don't have 'page' and thus dump_page() won't tell us anything, we look at mapping (NULL means true-anon, non-NULL means file, possibly COW). > (We've made our lives hard with varying definitions of 'anon' > also... [shmem being 'anon in page cache' is especially lol] so it's > already confusing but there we go :) Woah, woah, woah. Do *not* think of shmem as being anon-in-page-cache. shmem is a filesystem that happens to use swap to store its backing file. I dislike a number of things about how it's implemented, but describing it as anon-in-page-cache is furthering the confusion.