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Subject: Re: [PATCH] mm, soft-offline: convert parameter to pfn
To:     Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc:     Naoya Horiguchi <nao.horiguchi@gmail.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>
 <ac4c1ab9-1df6-6a30-30ed-a015622ef591@redhat.com>
 <20191017075018.GA10225@hori.linux.bs1.fc.nec.co.jp>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat GmbH
Message-ID: <108c55df-ac3f-c014-d79e-146cda1e80f6@redhat.com>
Date:   Thu, 17 Oct 2019 10:02:55 +0200
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On 17.10.19 09:50, Naoya Horiguchi wrote:
> On Thu, Oct 17, 2019 at 09:16:42AM +0200, David Hildenbrand wrote:
>> 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);)
> 
> Yes, right.
> 
>>
>> 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.
> 
> Actually I guess that !pfn_valid() never happens when called from
> madvise_inject_error(), because madvise_inject_error() gets pfn via
> get_user_pages_fast() which only returns valid page for valid pfn.
> 
> And we plan to remove MF_COUNT_INCREASED by Oscar's re-design work,
> so I start feeling that this patch should come on top of his tree.

I agree, let's clean that up first.

-- 

Thanks,

David / dhildenb