Subject: [PATCH v2 4/5] mm: memory_hotplug: Add memory hotremove probe device

From: [email-masked] (Andrea Reale)
Date: Mon, 4 Dec 2017 11:51:29 +0000

On Thu 30 Nov 2017, 15:49, Michal Hocko wrote:
> 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.
> 

This is actually still done in remove_memory() (patch 2/5) with
walk_memory_range. We just return an error rather than BUGing().

Or are you referring to something else?

> > Signed-off-by: Andrea Reale <[email-masked]>
> > Signed-off-by: Maciej Bielski <[email-masked]>
> > ---
> >  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

Thanks,
Andrea

> -- 
> Michal Hocko
> SUSE Labs