linux-kernel - Re: [PATCH v2 4/5] mm: memory_hotplug: Add memory hotremove probe device

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Message-ID: <20171130144905.ntpovhy66gekj6e6@dhcp22.suse.cz>
Date:   Thu, 30 Nov 2017 15:49:05 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Andrea Reale <ar@...ux.vnet.ibm.com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, m.bielski@...tualopensystems.com,
        arunks@....qualcomm.com, mark.rutland@....com,
        scott.branden@...adcom.com, will.deacon@....com,
        qiuxishi@...wei.com, catalin.marinas@....com, realean2@...ibm.com
Subject: Re: [PATCH v2 4/5] mm: memory_hotplug: Add memory hotremove probe
 device

On Thu 23-11-17 11:14:52, 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.

As already said elsewhere, this really has to check the online status of
the range and fail some is still online.

> Signed-off-by: Andrea Reale <ar@...ux.vnet.ibm.com>
> Signed-off-by: Maciej Bielski <m.bielski@...tualopensystems.com>
> ---
>  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);
> +	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
> -- 
> 2.7.4

-- 
Michal Hocko
SUSE Labs