Re: [PATCH 1/2] mm/memunmap: Use the correct start and end pfn when removing pages from zone

From: David Hildenbrand <david@redhat.com>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
	dan.j.williams@intel.com, akpm@linux-foundation.org
Cc: linux-mm@kvack.org, linux-nvdimm@lists.01.org
Subject: Re: [PATCH 1/2] mm/memunmap: Use the correct start and end pfn when removing pages from zone
Date: Thu, 26 Sep 2019 14:43:07 +0200	[thread overview]
Message-ID: <a9aaf327-2e36-618b-9ded-9800f3e6b73f@redhat.com> (raw)
In-Reply-To: <20190926122552.17905-1-aneesh.kumar@linux.ibm.com>

On 26.09.19 14:25, Aneesh Kumar K.V wrote:
> With altmap, all the resource pfns are not initialized. While initializing
> pfn, altmap reserve space is skipped. Hence when removing pfn from zone skip
> pfns that were never initialized.
> 
> Update memunmap_pages to calculate start and end pfn based on altmap
> values. This fixes a kernel crash that is observed when destroying namespace.
> 
> [   74.745056] BUG: Unable to handle kernel data access at 0xc00c000001400000
> [   74.745256] Faulting instruction address: 0xc0000000000b58b0
> cpu 0x2: Vector: 300 (Data Access) at [c00000026ea93580]
>     pc: c0000000000b58b0: memset+0x68/0x104
>     lr: c0000000003eb008: page_init_poison+0x38/0x50
>     ...
>   current = 0xc000000271c67d80
>   paca    = 0xc00000003fffd680   irqmask: 0x03   irq_happened: 0x01
>     pid   = 3665, comm = ndctl
> [link register   ] c0000000003eb008 page_init_poison+0x38/0x50
> [c00000026ea93830] c0000000004754d4 remove_pfn_range_from_zone+0x64/0x3e0
> [c00000026ea938a0] c0000000004b8a60 memunmap_pages+0x300/0x400
> [c00000026ea93930] c0000000009e32a0 devm_action_release+0x30/0x50
> ...
> 
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
> ---
>  mm/memremap.c | 15 ++++++++++-----
>  1 file changed, 10 insertions(+), 5 deletions(-)
> 
> diff --git a/mm/memremap.c b/mm/memremap.c
> index 390bb3544589..76b98110031e 100644
> --- a/mm/memremap.c
> +++ b/mm/memremap.c
> @@ -113,7 +113,8 @@ static void dev_pagemap_cleanup(struct dev_pagemap *pgmap)
>  void memunmap_pages(struct dev_pagemap *pgmap)
>  {
>  	struct resource *res = &pgmap->res;
> -	unsigned long pfn = PHYS_PFN(res->start);
> +	unsigned long start_pfn, end_pfn;
> +	unsigned long pfn, nr_pages;
>  	int nid;
>  
>  	dev_pagemap_kill(pgmap);
> @@ -121,14 +122,18 @@ void memunmap_pages(struct dev_pagemap *pgmap)
>  		put_page(pfn_to_page(pfn));
>  	dev_pagemap_cleanup(pgmap);
>  
> +	start_pfn = pfn_first(pgmap);
> +	end_pfn = pfn_end(pgmap);
> +	nr_pages = end_pfn - start_pfn;
> +
>  	/* pages are dead and unused, undo the arch mapping */
> -	nid = page_to_nid(pfn_to_page(pfn));
> +	nid = page_to_nid(pfn_to_page(start_pfn));
>  
>  	mem_hotplug_begin();
> -	remove_pfn_range_from_zone(page_zone(pfn_to_page(pfn)), pfn,
> -				   PHYS_PFN(resource_size(res)));
> +	remove_pfn_range_from_zone(page_zone(pfn_to_page(start_pfn)),
> +				   start_pfn, nr_pages);
>  	if (pgmap->type == MEMORY_DEVICE_PRIVATE) {
> -		__remove_pages(pfn, PHYS_PFN(resource_size(res)), NULL);
> +		__remove_pages(start_pfn, nr_pages, NULL);
>  	} else {
>  		arch_remove_memory(nid, res->start, resource_size(res),
>  				pgmap_altmap(pgmap));
> 

Just to make sure, my patches did not break that, right (IOW, broken
upstream)?

-- 

Thanks,

David / dhildenb
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