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Subject: Re: [PATCH] mm, soft-offline: convert parameter to pfn
To:     Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc:     Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        Michal Hocko <mhocko@kernel.org>,
        Oscar Salvador <osalvador@suse.de>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>
References: <20191016070924.GA10178@hori.linux.bs1.fc.nec.co.jp>
 <e931b14b-da27-2720-5344-b5c0b08b38ad@redhat.com>
 <20191016082735.GB13770@hori.linux.bs1.fc.nec.co.jp>
 <c78962ba-ffa1-90e2-0116-6c94d082de2f@redhat.com>
 <20191016085359.GD13770@hori.linux.bs1.fc.nec.co.jp>
 <997b5b51-db71-3e27-1f84-cbaa24fa66c7@redhat.com>
 <20191016234706.GA5493@www9186uo.sakura.ne.jp>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat GmbH
Message-ID: <ac4c1ab9-1df6-6a30-30ed-a015622ef591@redhat.com>
Date:   Thu, 17 Oct 2019 09:16:42 +0200
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On 17.10.19 01:47, Naoya Horiguchi wrote:
> On Wed, Oct 16, 2019 at 10:57:57AM +0200, David Hildenbrand wrote:
>> On 16.10.19 10:54, Naoya Horiguchi wrote:
>>> On Wed, Oct 16, 2019 at 10:34:52AM +0200, David Hildenbrand wrote:
>>>> On 16.10.19 10:27, Naoya Horiguchi wrote:
>>>>> 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?
>>>>
>>>> At least I can't am the patch to current next/master (due to
>>>> pfn_to_online_page()).
>>
>> Could also be that my "git am" skills failed as the mail was not a
>> proper patch itself :)
> 
> Sorry for the inconvenience, my company email system breaks original
> message by introducing quoted-printable format ('=20' or '=3D').
> Most mail client usually handles it but git-am doesn't.
> I give up using it and send via smtp.gmail.com.
> 
>>> @@ -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). */
>>> +	page = pfn_to_online_page(pfn);
>>> +	if (!page)
>>> +		return -EIO;
>>>   	if (is_zone_device_page(page)) {
>>
>> -> this is now no longer possible! So you can drop the whole if
>> (is_zone_device....) case
> 
> OK, thanks. I updated it.
> 
> Thanks,
> Naoya Horiguchi
> ---
>  From 5faf227839b578726fe7f5ff414a153abb3b3a31 Mon Sep 17 00:00:00 2001
> From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
> Date: Thu, 17 Oct 2019 08:40:53 +0900
> Subject: [PATCH] mm, soft-offline: convert parameter to pfn
> 
> Currently soft_offline_page() receives struct page, and its sibling
> memory_failure() receives pfn. This discrepancy looks weird and makes
> precheck on pfn validity tricky. So let's align them.
> 
> Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
> ---
>   drivers/base/memory.c |  7 +------
>   include/linux/mm.h    |  2 +-
>   mm/madvise.c          |  2 +-
>   mm/memory-failure.c   | 19 +++++++++----------
>   4 files changed, 12 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/base/memory.c b/drivers/base/memory.c
> index 55907c27075b..a757d9ed88a7 100644
> --- a/drivers/base/memory.c
> +++ b/drivers/base/memory.c
> @@ -538,12 +538,7 @@ static ssize_t soft_offline_page_store(struct device *dev,
>   	if (kstrtoull(buf, 0, &pfn) < 0)
>   		return -EINVAL;
>   	pfn >>= PAGE_SHIFT;
> -	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;
> -	ret = soft_offline_page(pfn_to_page(pfn), 0);
> +	ret = soft_offline_page(pfn, 0);
>   	return ret == 0 ? count : ret;
>   }
>   
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 44d058723db9..fd360d208346 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -2794,7 +2794,7 @@ extern int sysctl_memory_failure_early_kill;
>   extern int sysctl_memory_failure_recovery;
>   extern void shake_page(struct page *p, int access);
>   extern atomic_long_t num_poisoned_pages __read_mostly;
> -extern int soft_offline_page(struct page *page, int flags);
> +extern int soft_offline_page(unsigned long pfn, int flags);
>   
>   
>   /*
> diff --git a/mm/madvise.c b/mm/madvise.c
> index 2be9f3fdb05e..99dd06fecfa9 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -887,7 +887,7 @@ static int madvise_inject_error(int behavior,
>   			pr_info("Soft offlining pfn %#lx at process virtual address %#lx\n",
>   					pfn, start);
>   
> -			ret = soft_offline_page(page, MF_COUNT_INCREASED);
> +			ret = soft_offline_page(pfn, MF_COUNT_INCREASED);
>   			if (ret)
>   				return ret;
>   			continue;
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 05c8c6df25e6..af2712004a4d 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1476,7 +1476,7 @@ static void memory_failure_work_func(struct work_struct *work)
>   		if (!gotten)
>   			break;
>   		if (entry.flags & MF_SOFT_OFFLINE)
> -			soft_offline_page(pfn_to_page(entry.pfn), entry.flags);
> +			soft_offline_page(entry.pfn, entry.flags);
>   		else
>   			memory_failure(entry.pfn, entry.flags);
>   	}
> @@ -1857,7 +1857,7 @@ static int soft_offline_free_page(struct page *page)
>   
>   /**
>    * soft_offline_page - Soft offline a page.
> - * @page: page to offline
> + * @pfn: pfn to soft-offline
>    * @flags: flags. Same as memory_failure().
>    *
>    * Returns 0 on success, otherwise negated errno.
> @@ -1877,18 +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 (is_zone_device_page(page)) {
> -		pr_debug_ratelimited("soft_offline: %#lx page is device page\n",
> -				pfn);
> -		if (flags & MF_COUNT_INCREASED)
> -			put_page(page);
> +	if (!pfn_valid(pfn))
> +		return -ENXIO;
> +	/* Only online pages can be soft-offlined (esp., not ZONE_DEVICE). */
> +	page = pfn_to_online_page(pfn);
> +	if (!page)

If you pass in a PFN with MF_COUNT_INCREASED via mm/madvise.c, you would  
now no longer do a put_page(page) in case of ZONE_DEVICE (!page =  
pfn_to_online_page(pfn);)

something like this

page = pfn_to_online_page(pfn);
if (!page) {
	/*
	 * With MF_COUNT_INCREASED, we can use pfn_to_page() directly
	 * (esp., ZONE_DEVICE).
	 */
	if (flags & MF_COUNT_INCREASED)
		put_page(pfn_to_page(page));
	return -EIO;
}

For !pfn_valid(pfn), this is not relevant.

>   		return -EIO;
> -	}
>   
>   	if (PageHWPoison(page)) {
>   		pr_info("soft offline: %#lx page already poisoned\n", pfn);
> 


-- 

Thanks,

David / dhildenb