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 X-Spam-Level: X-Spam-Status: No, score=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 59A17C28CC0 for ; Thu, 30 May 2019 10:37:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2E4F925778 for ; Thu, 30 May 2019 10:37:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726757AbfE3KhQ (ORCPT ); Thu, 30 May 2019 06:37:16 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:33994 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726450AbfE3KhP (ORCPT ); Thu, 30 May 2019 06:37:15 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 56E97374; Thu, 30 May 2019 03:37:15 -0700 (PDT) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 3E7C93F5AF; Thu, 30 May 2019 03:37:12 -0700 (PDT) Date: Thu, 30 May 2019 11:37:09 +0100 From: Mark Rutland To: Anshuman Khandual Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, akpm@linux-foundation.org, catalin.marinas@arm.com, will.deacon@arm.com, mhocko@suse.com, ira.weiny@intel.com, david@redhat.com, cai@lca.pw, logang@deltatee.com, james.morse@arm.com, cpandya@codeaurora.org, arunks@codeaurora.org, dan.j.williams@intel.com, mgorman@techsingularity.net, osalvador@suse.de, ard.biesheuvel@arm.com Subject: Re: [PATCH V5 1/3] mm/hotplug: Reorder arch_remove_memory() call in __remove_memory() Message-ID: <20190530103709.GB56046@lakrids.cambridge.arm.com> References: <1559121387-674-1-git-send-email-anshuman.khandual@arm.com> <1559121387-674-2-git-send-email-anshuman.khandual@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1559121387-674-2-git-send-email-anshuman.khandual@arm.com> User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 29, 2019 at 02:46:25PM +0530, Anshuman Khandual wrote: > Memory hot remove uses get_nid_for_pfn() while tearing down linked sysfs > entries between memory block and node. It first checks pfn validity with > pfn_valid_within() before fetching nid. With CONFIG_HOLES_IN_ZONE config > (arm64 has this enabled) pfn_valid_within() calls pfn_valid(). > > pfn_valid() is an arch implementation on arm64 (CONFIG_HAVE_ARCH_PFN_VALID) > which scans all mapped memblock regions with memblock_is_map_memory(). This > creates a problem in memory hot remove path which has already removed given > memory range from memory block with memblock_[remove|free] before arriving > at unregister_mem_sect_under_nodes(). Hence get_nid_for_pfn() returns -1 > skipping subsequent sysfs_remove_link() calls leaving node <-> memory block > sysfs entries as is. Subsequent memory add operation hits BUG_ON() because > of existing sysfs entries. > > [ 62.007176] NUMA: Unknown node for memory at 0x680000000, assuming node 0 > [ 62.052517] ------------[ cut here ]------------ > [ 62.053211] kernel BUG at mm/memory_hotplug.c:1143! > [ 62.053868] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP > [ 62.054589] Modules linked in: > [ 62.054999] CPU: 19 PID: 3275 Comm: bash Not tainted 5.1.0-rc2-00004-g28cea40b2683 #41 > [ 62.056274] Hardware name: linux,dummy-virt (DT) > [ 62.057166] pstate: 40400005 (nZcv daif +PAN -UAO) > [ 62.058083] pc : add_memory_resource+0x1cc/0x1d8 > [ 62.058961] lr : add_memory_resource+0x10c/0x1d8 > [ 62.059842] sp : ffff0000168b3ce0 > [ 62.060477] x29: ffff0000168b3ce0 x28: ffff8005db546c00 > [ 62.061501] x27: 0000000000000000 x26: 0000000000000000 > [ 62.062509] x25: ffff0000111ef000 x24: ffff0000111ef5d0 > [ 62.063520] x23: 0000000000000000 x22: 00000006bfffffff > [ 62.064540] x21: 00000000ffffffef x20: 00000000006c0000 > [ 62.065558] x19: 0000000000680000 x18: 0000000000000024 > [ 62.066566] x17: 0000000000000000 x16: 0000000000000000 > [ 62.067579] x15: ffffffffffffffff x14: ffff8005e412e890 > [ 62.068588] x13: ffff8005d6b105d8 x12: 0000000000000000 > [ 62.069610] x11: ffff8005d6b10490 x10: 0000000000000040 > [ 62.070615] x9 : ffff8005e412e898 x8 : ffff8005e412e890 > [ 62.071631] x7 : ffff8005d6b105d8 x6 : ffff8005db546c00 > [ 62.072640] x5 : 0000000000000001 x4 : 0000000000000002 > [ 62.073654] x3 : ffff8005d7049480 x2 : 0000000000000002 > [ 62.074666] x1 : 0000000000000003 x0 : 00000000ffffffef > [ 62.075685] Process bash (pid: 3275, stack limit = 0x00000000d754280f) > [ 62.076930] Call trace: > [ 62.077411] add_memory_resource+0x1cc/0x1d8 > [ 62.078227] __add_memory+0x70/0xa8 > [ 62.078901] probe_store+0xa4/0xc8 > [ 62.079561] dev_attr_store+0x18/0x28 > [ 62.080270] sysfs_kf_write+0x40/0x58 > [ 62.080992] kernfs_fop_write+0xcc/0x1d8 > [ 62.081744] __vfs_write+0x18/0x40 > [ 62.082400] vfs_write+0xa4/0x1b0 > [ 62.083037] ksys_write+0x5c/0xc0 > [ 62.083681] __arm64_sys_write+0x18/0x20 > [ 62.084432] el0_svc_handler+0x88/0x100 > [ 62.085177] el0_svc+0x8/0xc > > Re-ordering arch_remove_memory() with memblock_[free|remove] solves the > problem on arm64 as pfn_valid() behaves correctly and returns positive > as memblock for the address range still exists. arch_remove_memory() > removes applicable memory sections from zone with __remove_pages() and > tears down kernel linear mapping. Removing memblock regions afterwards > is safe because there is no other memblock (bootmem) allocator user that > late. So nobody is going to allocate from the removed range just to blow > up later. Also nobody should be using the bootmem allocated range else > we wouldn't allow to remove it. So reordering is indeed safe. > > Acked-by: Michal Hocko > Reviewed-by: David Hildenbrand > Reviewed-by: Oscar Salvador > Signed-off-by: Anshuman Khandual Acked-by: Mark Rutland Mark. > --- > mm/memory_hotplug.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index e096c98..67dfdb8 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1851,10 +1851,10 @@ void __ref __remove_memory(int nid, u64 start, u64 size) > > /* remove memmap entry */ > firmware_map_remove(start, start + size, "System RAM"); > + arch_remove_memory(nid, start, size, NULL); > memblock_free(start, size); > memblock_remove(start, size); > > - arch_remove_memory(nid, start, size, NULL); > __release_memory_resource(start, size); > > try_offline_node(nid); > -- > 2.7.4 >