linux-kernel - Re: [PATCH v2 5/7] mm,memory_hotplug: Enforce pageblock alignment when memmap_on

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Date:   Fri, 26 Feb 2021 13:06:21 +0100
From:   Oscar Salvador <osalvador@...e.de>
To:     David Hildenbrand <david@...hat.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...nel.org>, VlastimilBabkavbabka@...e.cz,
        pasha.tatashin@...een.com, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, Anshuman Khandual <anshuman.khandual@....com>
Subject: Re: [PATCH v2 5/7] mm,memory_hotplug: Enforce pageblock alignment
 when memmap_on_memory

On Thu, Feb 25, 2021 at 07:27:33PM +0100, David Hildenbrand wrote:
> > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> > index d3fb036d33fd..1a4d5dd1a2c8 100644
> > --- a/mm/memory_hotplug.c
> > +++ b/mm/memory_hotplug.c
> > @@ -56,12 +56,16 @@ static int memmap_on_memory_show(char *buffer, const struct kernel_param *kp)
> >   static __meminit int memmap_on_memory_store(const char *val,
> >   					    const struct kernel_param *kp)
> >   {
> > +	unsigned long pageblock_size = PFN_PHYS(pageblock_nr_pages);
> > +
> >   	/*
> >   	 * Fail silently in case we cannot enable it due to system constraints.
> >   	 * User can always check whether it is enabled or not via /sys/module.
> >   	 */
> >   	if (!IS_ENABLED(CONFIG_ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE) ||
> > -	    (PMD_SIZE % sizeof(struct page)))
> > +	    (PMD_SIZE % sizeof(struct page)) ||
> > +	    !(MIN_MEMORY_BLOCK_SIZE - PMD_SIZE) ||
> > +	    !(MIN_MEMORY_BLOCK_SIZE - PMD_SIZE) % pageblock_size)
> >   		return 0;
> >   	return param_set_bool(val, kp);
> > 
> 
> Dito, rather squash in #1 and add a comment explaining what's happening
> there.

I was not sure about putting this and the PMD aligned patch as a
standalone patch, but I thought it might ease the review.
But I have no problem in placing them in patch#1 and put some more
detail into the changelog.

-- 
Oscar Salvador
SUSE L3