linux-kernel - Re: [PATCH] mm, soft-offline: convert parameter to pfn

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Date:   Wed, 16 Oct 2019 08:27:36 +0000
From:   Naoya Horiguchi <n-horiguchi@...jp.nec.com>
To:     David Hildenbrand <david@...hat.com>
CC:     "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Michal Hocko <mhocko@...nel.org>,
        Oscar Salvador <osalvador@...e.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] mm, soft-offline: convert parameter to pfn

On Wed, Oct 16, 2019 at 09:56:19AM +0200, David Hildenbrand wrote:
> On 16.10.19 09:09, Naoya Horiguchi wrote:
> > Hi,
> > 
> > I wrote a simple cleanup for parameter of soft_offline_page(),
> > based on thread https://lkml.org/lkml/2019/10/11/57.
> > 
> > I know that we need more cleanup on hwpoison-inject, but I think
> > that will be mentioned in re-write patchset Oscar is preparing now.
> > So let me shared only this part as a separate one now.
...
> 
> I think you should rebase that patch on linux-next (where the
> pfn_to_online_page() check is in place). I assume you'll want to move the
> pfn_to_online_page() check into soft_offline_page() then as well?

I rebased to next-20191016. And yes, we will move pfn_to_online_page()
into soft offline code.  It seems that we can also move pfn_valid(),
but is simply moving like below good enough for you?

  @@ -1877,11 +1877,17 @@ static int soft_offline_free_page(struct page *page)
    * This is not a 100% solution for all memory, but tries to be
    * ``good enough'' for the majority of memory.
    */
  -int soft_offline_page(struct page *page, int flags)
  +int soft_offline_page(unsigned long pfn, int flags)
   {
   	int ret;
  -	unsigned long pfn = page_to_pfn(page);
  +	struct page *page;
   
  +	if (!pfn_valid(pfn))
  +		return -ENXIO;
  +	/* Only online pages can be soft-offlined (esp., not ZONE_DEVICE). */
  +	if (!pfn_to_online_page(pfn))
  +		return -EIO;
  +	page = pfn_to_page(pfn);
   	if (is_zone_device_page(page)) {
   		pr_debug_ratelimited("soft_offline: %#lx page is device page\n",
   				pfn);
  -- 

Or we might have an option to do as memory_failure() does like below:

  int memory_failure(unsigned long pfn, int flags)
  {
          ....
          p = pfn_to_online_page(pfn);
          if (!p) {
                  if (pfn_valid(pfn)) {
                          pgmap = get_dev_pagemap(pfn, NULL);
                          if (pgmap)
                                  return memory_failure_dev_pagemap(pfn, flags,
                                                                    pgmap);
                  }
                  pr_err("Memory failure: %#lx: memory outside kernel control\n",
                          pfn);
                  return -ENXIO;
          }

Thanks,
Naoya Horiguchi