From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org (mail.linuxfoundation.org [140.211.169.12]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id EBF8A1A0202 for ; Fri, 8 Jan 2016 09:47:45 +1100 (AEDT) Date: Thu, 7 Jan 2016 14:47:43 -0800 From: Andrew Morton To: John Allen Cc: gregkh@linuxfoundation.org, Nathan Fontenot , Michael Ellerman , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, Dave Hansen Subject: Re: [PATCH v4] memory-hotplug: Fix kernel warning during memory hotplug on ppc64 Message-Id: <20160107144743.452a52299965027a27d7f66c@linux-foundation.org> In-Reply-To: <568D9568.1010808@linux.vnet.ibm.com> References: <568D9568.1010808@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, 6 Jan 2016 16:30:00 -0600 John Allen wrote: > This patch fixes a bug where a kernel warning is triggered when performing > a memory hotplug on ppc64. This warning may also occur on any architecture > that uses the memory_probe_store interface. (cc's added). Dave, could you please review this? Thanks. From: John Allen Subject: drivers/base/memory.c: fix kernel warning during memory hotplug on ppc64 Fix a bug where a kernel warning is triggered when performing a memory hotplug on ppc64. This warning may also occur on any architecture that uses the memory_probe_store interface. WARNING: at drivers/base/memory.c:200 CPU: 9 PID: 13042 Comm: systemd-udevd Not tainted 4.4.0-rc4-00113-g0bd0f1e-dirty #7 NIP [c00000000055e034] pages_correctly_reserved+0x134/0x1b0 LR [c00000000055e7f8] memory_subsys_online+0x68/0x140 Call Trace: [c0000000fa9e7b50] [c0000000fa9e7b90] 0xc0000000fa9e7b90 (unreliable) [c0000000fa9e7bb0] [c00000000055e7f8] memory_subsys_online+0x68/0x140 [c0000000fa9e7bf0] [c000000000540064] device_online+0xb4/0x120 [c0000000fa9e7c30] [c00000000055e6c0] store_mem_state+0xb0/0x180 [c0000000fa9e7c70] [c00000000053c5e4] dev_attr_store+0x34/0x60 [c0000000fa9e7c90] [c0000000002db0a4] sysfs_kf_write+0x64/0xa0 [c0000000fa9e7cb0] [c0000000002da0cc] kernfs_fop_write+0x17c/0x1e0 [c0000000fa9e7d00] [c0000000002481b0] __vfs_write+0x40/0x160 [c0000000fa9e7d90] [c000000000248ce8] vfs_write+0xb8/0x200 [c0000000fa9e7de0] [c000000000249b40] SyS_write+0x60/0x110 [c0000000fa9e7e30] [c000000000009260] system_call+0x38/0xd0 The warning is triggered because there is a udev rule that automatically tries to online memory after it has been added. The udev rule varies from distro to distro, but will generally look something like: SUBSYSTEM=="memory", ACTION=="add", ATTR{state}=="offline", ATTR{state}="online" On any architecture that uses memory_probe_store to reserve memory, the udev rule will be triggered after the first section of the block is reserved and will subsequently attempt to online the entire block, interrupting the memory reservation process and causing the warning. This patch modifies memory_probe_store to add a block of memory with a single call to add_memory as opposed to looping through and adding each section individually. A single call to add_memory is protected by the mem_hotplug mutex which will prevent the udev rule from onlining memory until the reservation of the entire block is complete. Signed-off-by: John Allen Cc: Nathan Fontenot Cc: Michael Ellerman Cc: Greg Kroah-Hartman Cc: Dave Hansen Signed-off-by: Andrew Morton --- drivers/base/memory.c | 16 ++++++---------- 1 file changed, 6 insertions(+), 10 deletions(-) diff -puN drivers/base/memory.c~memory-hotplug-fix-kernel-warning-during-memory-hotplug-on-ppc64 drivers/base/memory.c --- a/drivers/base/memory.c~memory-hotplug-fix-kernel-warning-during-memory-hotplug-on-ppc64 +++ a/drivers/base/memory.c @@ -450,8 +450,7 @@ memory_probe_store(struct device *dev, s const char *buf, size_t count) { u64 phys_addr; - int nid; - int i, ret; + int nid, ret; unsigned long pages_per_block = PAGES_PER_SECTION * sections_per_block; ret = kstrtoull(buf, 0, &phys_addr); @@ -461,15 +460,12 @@ memory_probe_store(struct device *dev, s if (phys_addr & ((pages_per_block << PAGE_SHIFT) - 1)) return -EINVAL; - for (i = 0; i < sections_per_block; i++) { - nid = memory_add_physaddr_to_nid(phys_addr); - ret = add_memory(nid, phys_addr, - PAGES_PER_SECTION << PAGE_SHIFT); - if (ret) - goto out; + nid = memory_add_physaddr_to_nid(phys_addr); + ret = add_memory(nid, phys_addr, + MIN_MEMORY_BLOCK_SIZE * sections_per_block); - phys_addr += MIN_MEMORY_BLOCK_SIZE; - } + if (ret) + goto out; ret = count; out: _