[PATCH v2 4/5] mm: memory_hotplug: Add memory hotremove probe device
From: robin.murphy@arm.com (Robin Murphy)
Date: 2017-11-27 15:33:06
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linux-mm, lkml
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?
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Signed-off-by: Andrea Reale <redacted> Signed-off-by: Maciej Bielski <redacted> --- 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.
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+ 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