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From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
To: Oscar Salvador <osalvador@suse.de>
Cc: "mhocko@kernel.org" <mhocko@kernel.org>,
	"mike.kravetz@oracle.com" <mike.kravetz@oracle.com>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH v2 10/16] mm,hwpoison: Rework soft offline for free pages
Date: Mon, 21 Oct 2019 07:45:33 +0000
Message-ID: <20191021074533.GA10507@hori.linux.bs1.fc.nec.co.jp> (raw)
In-Reply-To: <20191017142123.24245-11-osalvador@suse.de>

On Thu, Oct 17, 2019 at 04:21:17PM +0200, Oscar Salvador wrote:
> When trying to soft-offline a free page, we need to first take it off
> the buddy allocator.
> Once we know is out of reach, we can safely flag it as poisoned.
> 
> take_page_off_buddy will be used to take a page meant to be poisoned
> off the buddy allocator.
> take_page_off_buddy calls break_down_buddy_pages, which splits a
> higher-order page in case our page belongs to one.
> 
> Once the page is under our control, we call page_set_poison to set it

I guess you mean page_handle_poison here.

> as poisoned and grab a refcount on it.
> 
> Signed-off-by: Oscar Salvador <osalvador@suse.de>
> ---
>  mm/memory-failure.c | 20 +++++++++++-----
>  mm/page_alloc.c     | 68 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 82 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 37b230b8cfe7..1d986580522d 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -78,6 +78,15 @@ EXPORT_SYMBOL_GPL(hwpoison_filter_dev_minor);
>  EXPORT_SYMBOL_GPL(hwpoison_filter_flags_mask);
>  EXPORT_SYMBOL_GPL(hwpoison_filter_flags_value);
>  
> +extern bool take_page_off_buddy(struct page *page);
> +
> +static void page_handle_poison(struct page *page)

hwpoison is a separate idea from page poisoning, so maybe I think
it's better to be named like page_handle_hwpoison().

> +{
> +	SetPageHWPoison(page);
> +	page_ref_inc(page);
> +	num_poisoned_pages_inc();
> +}
> +
>  static int hwpoison_filter_dev(struct page *p)
>  {
>  	struct address_space *mapping;
> @@ -1830,14 +1839,13 @@ static int soft_offline_in_use_page(struct page *page)
>  
>  static int soft_offline_free_page(struct page *page)
>  {
> -	int rc = dissolve_free_huge_page(page);
> +	int rc = -EBUSY;
>  
> -	if (!rc) {
> -		if (set_hwpoison_free_buddy_page(page))
> -			num_poisoned_pages_inc();
> -		else
> -			rc = -EBUSY;
> +	if (!dissolve_free_huge_page(page) && take_page_off_buddy(page)) {
> +		page_handle_poison(page);
> +		rc = 0;
>  	}
> +
>  	return rc;
>  }
>  
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index cd1dd0712624..255df0c76a40 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -8632,6 +8632,74 @@ bool is_free_buddy_page(struct page *page)
>  
>  #ifdef CONFIG_MEMORY_FAILURE
>  /*
> + * Break down a higher-order page in sub-pages, and keep our target out of
> + * buddy allocator.
> + */
> +static void break_down_buddy_pages(struct zone *zone, struct page *page,
> +				   struct page *target, int low, int high,
> +				   struct free_area *area, int migratetype)
> +{
> +	unsigned long size = 1 << high;
> +	struct page *current_buddy, *next_page;
> +
> +	while (high > low) {
> +		area--;
> +		high--;
> +		size >>= 1;
> +
> +		if (target >= &page[size]) {
> +			next_page = page + size;
> +			current_buddy = page;
> +		} else {
> +			next_page = page;
> +			current_buddy = page + size;
> +		}
> +
> +		if (set_page_guard(zone, current_buddy, high, migratetype))
> +			continue;
> +
> +		if (current_buddy != target) {
> +			add_to_free_area(current_buddy, area, migratetype);
> +			set_page_order(current_buddy, high);
> +			page = next_page;
> +		}
> +	}
> +}
> +
> +/*
> + * Take a page that will be marked as poisoned off the buddy allocator.
> + */
> +bool take_page_off_buddy(struct page *page)
> + {
> +	struct zone *zone = page_zone(page);
> +	unsigned long pfn = page_to_pfn(page);
> +	unsigned long flags;
> +	unsigned int order;
> +	bool ret = false;
> +
> +	spin_lock_irqsave(&zone->lock, flags);
> +	for (order = 0; order < MAX_ORDER; order++) {
> +		struct page *page_head = page - (pfn & ((1 << order) - 1));
> +		int buddy_order = page_order(page_head);
> +		struct free_area *area = &(zone->free_area[buddy_order]);
> +
> +		if (PageBuddy(page_head) && buddy_order >= order) {
> +			unsigned long pfn_head = page_to_pfn(page_head);
> +			int migratetype = get_pfnblock_migratetype(page_head,
> +		                                                   pfn_head);
> +
> +			del_page_from_free_area(page_head, area);
> +			break_down_buddy_pages(zone, page_head, page, 0,
> +		                               buddy_order, area, migratetype);
> +			ret = true;
> +		        break;

indent with whitespace?
And you can find a few more coding style warning with checkpatch.pl.

BTW, if we consider to make unpoison mechanism to keep up with the
new semantics, we will need the reverse operation of take_page_off_buddy().
Do you think that that part will come with a separate work?

Thanks,
Naoya Horiguchi

> +		 }
> +	}
> +	spin_unlock_irqrestore(&zone->lock, flags);
> +	return ret;
> + }
> +
> +/*
>   * Set PG_hwpoison flag if a given page is confirmed to be a free page.  This
>   * test is performed under the zone lock to prevent a race against page
>   * allocation.
> -- 
> 2.12.3
> 
> 


  parent reply index

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-17 14:21 [RFC PATCH v2 00/16] Hwpoison rework {hard,soft}-offline Oscar Salvador
2019-10-17 14:21 ` [RFC PATCH v2 01/16] mm,hwpoison: cleanup unused PageHuge() check Oscar Salvador
2019-10-18 11:48   ` Michal Hocko
2019-10-21  7:00     ` Naoya Horiguchi
2019-10-21 12:16       ` Michal Hocko
2019-11-12 12:22       ` Aneesh Kumar K.V
2019-11-13  6:02         ` Naoya Horiguchi
2019-10-17 14:21 ` [RFC PATCH v2 02/16] mm,madvise: call soft_offline_page() without MF_COUNT_INCREASED Oscar Salvador
2019-10-18 11:52   ` Michal Hocko
2019-10-21  7:02     ` Naoya Horiguchi
2019-10-21 12:20       ` Michal Hocko
2019-10-17 14:21 ` [RFC PATCH v2 03/16] mm,madvise: Refactor madvise_inject_error Oscar Salvador
2019-10-21  7:03   ` Naoya Horiguchi
2019-10-17 14:21 ` [RFC PATCH v2 04/16] mm,hwpoison-inject: don't pin for hwpoison_filter Oscar Salvador
2019-10-17 14:21 ` [RFC PATCH v2 05/16] mm,hwpoison: Un-export get_hwpoison_page and make it static Oscar Salvador
2019-10-21  7:03   ` Naoya Horiguchi
2019-10-17 14:21 ` [RFC PATCH v2 06/16] mm,hwpoison: Kill put_hwpoison_page Oscar Salvador
2019-10-21  7:04   ` Naoya Horiguchi
2019-10-17 14:21 ` [RFC PATCH v2 07/16] mm,hwpoison: remove MF_COUNT_INCREASED Oscar Salvador
2019-10-17 14:21 ` [RFC PATCH v2 08/16] mm,hwpoison: remove flag argument from soft offline functions Oscar Salvador
2019-10-17 14:21 ` [RFC PATCH v2 09/16] mm,hwpoison: Unify THP handling for hard and soft offline Oscar Salvador
2019-10-21  7:04   ` Naoya Horiguchi
2019-10-21  9:51     ` [PATCH 17/16] mm,hwpoison: introduce MF_MSG_UNSPLIT_THP Naoya Horiguchi
2019-10-22  8:00       ` Oscar Salvador
2019-10-17 14:21 ` [RFC PATCH v2 10/16] mm,hwpoison: Rework soft offline for free pages Oscar Salvador
2019-10-18 12:06   ` Michal Hocko
2019-10-21 12:58     ` Oscar Salvador
2019-10-21 15:41       ` Michal Hocko
2019-10-22  7:46         ` Oscar Salvador
2019-10-22  8:26           ` Michal Hocko
2019-10-22  8:35             ` Oscar Salvador
2019-10-22  9:22               ` Michal Hocko
2019-10-22  9:58                 ` Oscar Salvador
2019-10-22 10:24                   ` Michal Hocko
2019-10-22 10:33                     ` Oscar Salvador
2019-10-23  2:15                       ` Naoya Horiguchi
2019-10-23  2:01                   ` Naoya Horiguchi
2019-10-21  7:45   ` Naoya Horiguchi [this message]
2019-10-22  8:00     ` Oscar Salvador
2019-10-17 14:21 ` [RFC PATCH v2 11/16] mm,hwpoison: Rework soft offline for in-use pages Oscar Salvador
2019-10-18 12:39   ` Michal Hocko
2019-10-21 13:48     ` Oscar Salvador
2019-10-21 14:06       ` Michal Hocko
2019-10-22  7:56         ` Oscar Salvador
2019-10-22  8:30           ` Michal Hocko
2019-10-22  9:40             ` Oscar Salvador
2019-10-17 14:21 ` [RFC PATCH v2 12/16] mm,hwpoison: Refactor soft_offline_huge_page and __soft_offline_page Oscar Salvador
2019-10-17 14:21 ` [RFC PATCH v2 13/16] mm,hwpoison: Take pages off the buddy when hard-offlining Oscar Salvador
2019-10-17 14:21 ` [RFC PATCH v2 14/16] mm,hwpoison: Return 0 if the page is already poisoned in soft-offline Oscar Salvador
2019-10-21  9:20   ` Naoya Horiguchi
2019-10-17 14:21 ` [RFC PATCH v2 15/16] mm/hwpoison-inject: Rip off duplicated checks Oscar Salvador
2019-10-21  9:40   ` David Hildenbrand
2019-10-22  7:57     ` Oscar Salvador
2019-10-17 14:21 ` [RFC PATCH v2 16/16] mm, soft-offline: convert parameter to pfn Oscar Salvador
2019-10-18  8:15   ` David Hildenbrand
2020-06-11 16:43 ` [RFC PATCH v2 00/16] Hwpoison rework {hard,soft}-offline Dmitry Yakunin
2020-06-15  6:19   ` HORIGUCHI NAOYA(堀口 直也)

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