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Violators will be prosecuted for from ; Mon, 27 Nov 2017 17:14:50 -0000 Date: Mon, 27 Nov 2017 17:14:43 +0000 From: Andrea Reale Subject: Re: [PATCH v2 4/5] mm: memory_hotplug: Add memory hotremove probe device References: <22d34fe30df0fbacbfceeb47e20cb1184af73585.1511433386.git.ar@linux.vnet.ibm.com> <198063b0-fcc9-7beb-7476-86ed5f04734c@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <198063b0-fcc9-7beb-7476-86ed5f04734c@arm.com> Message-Id: <20171127171441.GB12687@samekh> Sender: owner-linux-mm@kvack.org List-ID: To: Robin Murphy Cc: linux-arm-kernel@lists.infradead.org, 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 Hi Robin, On Mon 27 Nov 2017, 15:33, Robin Murphy wrote: > 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? > as I was saying in a response to your previous message, in our use case remove events are triggered by software. Besides our use case, yes, it is mostly just a handy develeopment feature AFAICT. > >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. Makes sense. Suggestion noted, thanks. > 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