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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 6A87CC4CEC9 for ; Wed, 18 Sep 2019 09:28:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 42C2821907 for ; Wed, 18 Sep 2019 09:28:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728963AbfIRJ2f (ORCPT ); Wed, 18 Sep 2019 05:28:35 -0400 Received: from foss.arm.com ([217.140.110.172]:38130 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725989AbfIRJ2f (ORCPT ); Wed, 18 Sep 2019 05:28:35 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 23566337; Wed, 18 Sep 2019 02:28:34 -0700 (PDT) Received: from [10.162.40.136] (p8cg001049571a15.blr.arm.com [10.162.40.136]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A134F3F59C; Wed, 18 Sep 2019 02:28:26 -0700 (PDT) Subject: Re: [PATCH V7 1/3] mm/hotplug: Reorder memblock_[free|remove]() calls in try_remove_memory() To: Balbir Singh , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, akpm@linux-foundation.org, catalin.marinas@arm.com, will@kernel.org Cc: mark.rutland@arm.com, mhocko@suse.com, ira.weiny@intel.com, david@redhat.com, cai@lca.pw, logang@deltatee.com, cpandya@codeaurora.org, arunks@codeaurora.org, dan.j.williams@intel.com, mgorman@techsingularity.net, osalvador@suse.de, ard.biesheuvel@arm.com, steve.capper@arm.com, broonie@kernel.org, valentin.schneider@arm.com, Robin.Murphy@arm.com, steven.price@arm.com, suzuki.poulose@arm.com References: <1567503958-25831-1-git-send-email-anshuman.khandual@arm.com> <1567503958-25831-2-git-send-email-anshuman.khandual@arm.com> <74bcbd36-3bec-be67-917d-60cd74cbcef0@gmail.com> From: Anshuman Khandual Message-ID: <91efada2-23e3-1982-47bc-82fb93ce944a@arm.com> Date: Wed, 18 Sep 2019 14:58:40 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <74bcbd36-3bec-be67-917d-60cd74cbcef0@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/16/2019 07:14 AM, Balbir Singh wrote: > > > On 3/9/19 7:45 pm, Anshuman Khandual wrote: >> Memory hot remove uses get_nid_for_pfn() while tearing down linked sysfs > > I could not find this path in the code, the only called for get_nid_for_pfn() > was register_mem_sect_under_node() when the system is under boot. > >> 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 ]------------ > > This seems like arm64 is not ready for probe_store() via drivers/base/memory.c/ode.c > >> [ 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 memblock_[free|remove]() with arch_remove_memory() 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. >> >> Reviewed-by: David Hildenbrand >> Reviewed-by: Oscar Salvador >> Acked-by: Mark Rutland >> Acked-by: Michal Hocko >> Signed-off-by: Anshuman Khandual >> --- > > Honestly, the issue is not clear from the changelog, largely > because I can't find the use of get_nid_for_pfn() being used > in memory hotunplug. I can see why using pfn_valid() after > memblock_free/remove is bad on the architecture. > > I think the checks to pfn_valid() can be avoided from the > remove paths if we did the following > > memblock_isolate_regions() > for each isolate_region { > memblock_free > memblock_remove > arch_memory_remove > > # ensure that __remove_memory can avoid calling pfn_valid > } > > Having said that, your patch is easier and if your assumption > about not using the memblocks is valid (after arch_memory_remove()) > then might be the least resistant way forward The context for this patch has changed a bit which now reflects in it's current posting (https://patchwork.kernel.org/patch/11146361/)