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 D28AFC47089 for ; Sun, 4 Dec 2022 01:32:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229723AbiLDBcI (ORCPT ); Sat, 3 Dec 2022 20:32:08 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35518 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229579AbiLDBcE (ORCPT ); Sat, 3 Dec 2022 20:32:04 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A48E01A20C for ; Sat, 3 Dec 2022 17:31:05 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1670117464; h=from:from: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; bh=bvoEFYsGTw5jklQZGQN0bnmfJGNpXCO+XUUFb1arslE=; b=YJm+NuGvGa9pIzdBSA1WWDWfOBlnNUzUdVNNvKjTBbqr3hbG8fwHeV8TSrLGS1Tv1PKyVP DXDPXVSu75Io93awsQzYkzXuJKuWd3HhXu/1XVjiNhWbSCRPRSBker8ISU0arrS5XwUsfF h/ulbqrP6C38I5ixBtbJ0w0tqaHwzsg= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-638-2BcEdNdLMgKGiHcibllmVQ-1; Sat, 03 Dec 2022 20:31:00 -0500 X-MC-Unique: 2BcEdNdLMgKGiHcibllmVQ-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 340F085A59D; Sun, 4 Dec 2022 01:31:00 +0000 (UTC) Received: from MiWiFi-R3L-srv.redhat.com (ovpn-12-31.pek2.redhat.com [10.72.12.31]) by smtp.corp.redhat.com (Postfix) with ESMTP id 328AB141511E; Sun, 4 Dec 2022 01:30:55 +0000 (UTC) From: Baoquan He To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, stephen.s.brennan@oracle.com, urezki@gmail.com, willy@infradead.org, akpm@linux-foundation.org, hch@infradead.org, Baoquan He Subject: [PATCH v1 0/7] mm/vmalloc.c: allow vread() to read out vm_map_ram areas Date: Sun, 4 Dec 2022 09:30:39 +0800 Message-Id: <20221204013046.154960-1-bhe@redhat.com> MIME-Version: 1.0 Content-type: text/plain Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.1 on 10.11.54.7 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Problem: *** Stephen reported vread() will skip vm_map_ram areas when reading out /proc/kcore with drgn utility. Please see below link to get more about it: /proc/kcore reads 0's for vmap_block https://lore.kernel.org/all/87ilk6gos2.fsf@oracle.com/T/#u Root cause: *** The normal vmalloc API uses struct vmap_area to manage the virtual kernel area allocated and associate a vm_struct to store more information and passed out. However, area reserved through vm_map_ram() interface doesn't allocate vm_struct to bind with. So the current code in vread() will skip the vm_map_ram area through 'if (!va->vm)' conditional checking. Solution: *** There are two types of vm_map_ram area. One is the whole vmap_area being reserved and mapped at one time; the other is the whole vmap_area with VMAP_BLOCK_SIZE size being reserved at one time, while mapped into split regions with smaller size several times via vb_alloc(). I will call the 2nd type vb region. In patch 1 and 2, add flags into struct vmap_area to mark these two types of vm_map_ram area, meanwhile add bitmap field used_map into struct vmap_block to mark those vb regions being used to differentiate with dirty and free regions in vmap_block. With the help of above vmap_area->flags and vmap_block->used_map, we can recognize them in vread() and handle them respectively in patch 3. Now since we can identify vm_map_ram area explicitly, change the ambiguous checking 'if (!va->vm) with clear "if (!va->vm && (va->flags & VMAP_RAM))" in s_show() to pick out vm_map_ram area clearly. This avoids the normal vmalloc area being unmapped to be recognized as vm_map_ram area. This is done in pach 4. Besides, *** In patch 5, let's ignore vmap area with VM_UNINITIALIZED set in vm->flags, because this kind of area is created by calling __vmalloc_node_range(), VM_UNINITIALIZED set indicating it has vm_struct associated with, but is still during the page allocating and mapping process. In patch 6 and 7, change area flag from VM_ALLOC to VM_IOREMAP in two places. This will show them as 'ioremap' in /proc/vmallocinfo, and exclude them from /proc/kcore. Testing *** Stephen helped test RFC and the draft fix patch. Now I only put this v1 patchset on a bare metal to compile and run for basic functionality testing. It still needs Stephen to help test the vm_map_ram issue. Changelog *** RFC->v1: - Add a new field flags in vmap_area to mark vm_map_ram area. It cold be risky reusing the vm union in vmap_area in RFC. I will consider reusing the union in vmap_area to save memory later. Now just take the simpler way to let's focus on resolving the main problem. - Add patch 4~7 for optimization. Baoquan He (7): mm/vmalloc.c: add used_map into vmap_block to track space of vmap_block mm/vmalloc.c: add flags to mark vm_map_ram area mm/vmalloc.c: allow vread() to read out vm_map_ram areas mm/vmalloc: explicitly identify vm_map_ram area when shown in /proc/vmcoreinfo mm/vmalloc: skip the uninitilized vmalloc areas powerpc: mm: add VM_IOREMAP flag to the vmalloc area sh: mm: set VM_IOREMAP flag to the vmalloc area arch/powerpc/kernel/pci_64.c | 2 +- arch/sh/kernel/cpu/sh4/sq.c | 2 +- include/linux/vmalloc.h | 1 + mm/vmalloc.c | 97 +++++++++++++++++++++++++++++++----- 4 files changed, 87 insertions(+), 15 deletions(-) -- 2.34.1