From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f69.google.com (mail-oi0-f69.google.com [209.85.218.69]) by kanga.kvack.org (Postfix) with ESMTP id 490316B0253 for ; Mon, 27 Nov 2017 10:33:06 -0500 (EST) Received: by mail-oi0-f69.google.com with SMTP id l138so12792289oib.0 for ; Mon, 27 Nov 2017 07:33:06 -0800 (PST) Received: from foss.arm.com (usa-sjc-mx-foss1.foss.arm.com. [217.140.101.70]) by mx.google.com with ESMTP id q32si12089157ota.214.2017.11.27.07.33.04 for ; Mon, 27 Nov 2017 07:33:05 -0800 (PST) Subject: Re: [PATCH v2 4/5] mm: memory_hotplug: Add memory hotremove probe device References: <22d34fe30df0fbacbfceeb47e20cb1184af73585.1511433386.git.ar@linux.vnet.ibm.com> From: Robin Murphy Message-ID: <198063b0-fcc9-7beb-7476-86ed5f04734c@arm.com> Date: Mon, 27 Nov 2017 15:33:01 +0000 MIME-Version: 1.0 In-Reply-To: <22d34fe30df0fbacbfceeb47e20cb1184af73585.1511433386.git.ar@linux.vnet.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrea Reale , linux-arm-kernel@lists.infradead.org Cc: mark.rutland@arm.com, realean2@ie.ibm.com, mhocko@suse.com, m.bielski@virtualopensystems.com, scott.branden@broadcom.com, catalin.marinas@arm.com, will.deacon@arm.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, arunks@qti.qualcomm.com, qiuxishi@huawei.com On 23/11/17 11:14, Andrea Reale wrote: > Adding a "remove" sysfs handle that can be used to trigger > memory hotremove manually, exactly simmetrically with > what happens with the "probe" device for hot-add. > > This is usueful for architecture that do not rely on > ACPI for memory hot-remove. Is there a real-world use-case for this, or is it mostly just a handy development feature? > Signed-off-by: Andrea Reale > Signed-off-by: Maciej Bielski > --- > drivers/base/memory.c | 34 +++++++++++++++++++++++++++++++++- > 1 file changed, 33 insertions(+), 1 deletion(-) > > diff --git a/drivers/base/memory.c b/drivers/base/memory.c > index 1d60b58..8ccb67c 100644 > --- a/drivers/base/memory.c > +++ b/drivers/base/memory.c > @@ -530,7 +530,36 @@ memory_probe_store(struct device *dev, struct device_attribute *attr, > } > > static DEVICE_ATTR(probe, S_IWUSR, NULL, memory_probe_store); > -#endif > + > +#ifdef CONFIG_MEMORY_HOTREMOVE > +static ssize_t > +memory_remove_store(struct device *dev, > + struct device_attribute *attr, const char *buf, size_t count) > +{ > + u64 phys_addr; > + int nid, ret; > + unsigned long pages_per_block = PAGES_PER_SECTION * sections_per_block; > + > + ret = kstrtoull(buf, 0, &phys_addr); > + if (ret) > + return ret; > + > + if (phys_addr & ((pages_per_block << PAGE_SHIFT) - 1)) > + return -EINVAL; > + > + nid = memory_add_physaddr_to_nid(phys_addr); This call looks a bit odd, since you're not doing a memory add. In fact, any memory being removed should already be fully known-about, so AFAICS it should be simple to get everything you need to know (including potentially the online status as mentioned earlier), through 'normal' methods, e.g. page_to_nid() or similar. Robin. > + ret = lock_device_hotplug_sysfs(); > + if (ret) > + return ret; > + > + remove_memory(nid, phys_addr, > + MIN_MEMORY_BLOCK_SIZE * sections_per_block); > + unlock_device_hotplug(); > + return count; > +} > +static DEVICE_ATTR(remove, S_IWUSR, NULL, memory_remove_store); > +#endif /* CONFIG_MEMORY_HOTREMOVE */ > +#endif /* CONFIG_ARCH_MEMORY_PROBE */ > > #ifdef CONFIG_MEMORY_FAILURE > /* > @@ -790,6 +819,9 @@ bool is_memblock_offlined(struct memory_block *mem) > static struct attribute *memory_root_attrs[] = { > #ifdef CONFIG_ARCH_MEMORY_PROBE > &dev_attr_probe.attr, > +#ifdef CONFIG_MEMORY_HOTREMOVE > + &dev_attr_remove.attr, > +#endif > #endif > > #ifdef CONFIG_MEMORY_FAILURE > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org