From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta1.migadu.com (out-27.mta1.migadu.com [95.215.58.27]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B3BBC401A2E for ; Mon, 28 Sep 2026 08:32:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.27 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790584326; cv=none; b=p5/ySgqG2Eqcj43SQKmznhG7la7DVuTHMgYMCmq4h4rlCBa9fm84Dp62ZBqaO5PpytbEw07g2RzYEvgU/tsBMilMcP8aIIS+0Ox796k+g9J10alKGe73IQFdb/SzaRyIYmcgt8k4HXNjUlPwK95n/Niaegp2b4DffBOjlguvnSg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790584326; c=relaxed/simple; bh=0vsNUizkmzlbu8y8J+IZWSMNjN9v2l2Yufh8n4d8/RU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=RMzko2J9Qfo6B3BQzOIjsm0OVKl7Y++b2I8JglD75WBkM4vEQUKPvqTmlnLudkBqLhEHvYDyBw9rV7w6m4c1MqqEm87DSkm3vl0zj9VBcBkcMQyEUepHKnAnup2IxtlMvqqHzkS5oeF2ozlsDkLmI8ihCka1Sm/26enwWXUF3yk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=tyjF0o3c; arc=none smtp.client-ip=95.215.58.27 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="tyjF0o3c" X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=0vsNUizkmzlbu8y8J+IZWSMNjN9v2l2Yufh8n4d8/RU=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1790584322; v=1; x=1791189122; b=tyjF0o3cR9ljeFX4XK3gL8z3b7xqobt2exvjAkbD+PvnbxNfg2F1GudPKGeS+nnZnBWsZe8e AEK7Cwjwz0O91OKfGmf/5KNZvAVKzBK9uEzR8gkDGuKYdlvX3ue6Aq1wiZnpSoUClPeZEUe3bhA 4Klw25etPFVrQB63qCKJd9bo= X-Envelope-To: linux-kernel@vger.kernel.org Received: by mta11.migadu.com with ESMTPS id 42d1b3bbabd087ec; Mon, 28 Sep 2026 08:32:01 +0000 X-Mizu-Trace-ID: 42d1b3bbabd087ec X-Migadu-Flow: FLOW_OUT Date: Mon, 28 Sep 2026 16:31:51 +0800 From: Baoquan He To: "David Hildenbrand (Arm)" , k-hagio-ab@nec.com, ruirui.yang@linux.dev Cc: David Carlier , akpm@linux-foundation.org, axelrasmussen@google.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, brendan.jackman@linux.dev, dakr@kernel.org, driver-core@lists.linux.dev, gregkh@linuxfoundation.org, hannes@cmpxchg.org, jan.kiszka@siemens.com, kasong@tencent.com, kbingham@kernel.org, liam@infradead.org, linux-cxl@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, ljs@kernel.org, mhocko@suse.com, osalvador@suse.de, qi.zheng@linux.dev, rafael@kernel.org, rppt@kernel.org, shakeel.butt@linux.dev, surenb@google.com, vbabka@kernel.org, weixugc@google.com, yuanchu@google.com, ziy@nvidia.com, devel@lists.crash-utility.osci.io Subject: Re: [PATCH v2 10/13] mm/sparse: remove SECTION_MARKED_PRESENT Message-ID: References: <20260921-b4-sparsemem_cleanups-v2-10-54d81d65e125@kernel.org> <20260927192013.144672-1-devnexen@gmail.com> <655c509e-318f-48bc-8183-2b1274dd05ac@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <655c509e-318f-48bc-8183-2b1274dd05ac@kernel.org> On 09/28/26 at 09:28am, David Hildenbrand (Arm) wrote: > On 9/27/26 21:20, David Carlier wrote: > > On Mon, Sep 21, 2026 at 09:59:02PM +0200, David Hildenbrand (Arm) wrote: > >> enum { > >> - SECTION_MARKED_PRESENT_BIT, > >> SECTION_HAS_MEM_MAP_BIT, > >> SECTION_IS_ONLINE_BIT, > >> SECTION_IS_EARLY_BIT, > > > > Hi David, > > Hi! > > > > > It seems dropping SECTION_MARKED_PRESENT_BIT shifts the other section flags down > > one bit. crash hardcodes SECTION_HAS_MEM_MAP as (1UL << 1) in > > pfn_to_map(), so it now tests SECTION_IS_ONLINE: offline and > > ZONE_DEVICE sections no longer resolve to a struct page. makedumpfile > > only checks bit 0 and is fine. > > Thanks. To be expected when relying on kernel internals. > > Which makes me wonder why makedumpfile > (https://github.com/makedumpfile/makedumpfile) not require any such information. Makedumpfile requires it too, while it doesn't ask for HAS_MEM_MAP. So checking MARKED_PRESENT becomes checking HAS_MEM_MAP's value, it luckily works. # git grep MARKED_PRESENT makedumpfile.c: if (!(map_mask & SECTION_MARKED_PRESENT)) { makedumpfile.h:#define SECTION_MARKED_PRESENT (1UL<<0) Add makedumpfile maintainer Kazu here. And add Dave Young here since I heard he is taking over Crash maintenance as a volunteer. > > > > > Keep bit 0 reserved, or export the bits via vmcoreinfo? > We could export it, or crash can simply detect the change based on the kernel > version. I remember the latter was done in makedumpfile in the past (although we > export it). > > I can send a separate patch to export it. > > -- > Cheers, > > David