linux-kernel - Re: [PATCH v1 1/3] mm: pass meminit_context to __free_pages

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Date: Fri, 7 Jun 2024 20:40:52 +0200
From: David Hildenbrand <david@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org, linux-hyperv@...r.kernel.org,
 virtualization@...ts.linux.dev, xen-devel@...ts.xenproject.org,
 kasan-dev@...glegroups.com, Andrew Morton <akpm@...ux-foundation.org>,
 Mike Rapoport <rppt@...nel.org>, Oscar Salvador <osalvador@...e.de>,
 "K. Y. Srinivasan" <kys@...rosoft.com>,
 Haiyang Zhang <haiyangz@...rosoft.com>, Wei Liu <wei.liu@...nel.org>,
 Dexuan Cui <decui@...rosoft.com>, "Michael S. Tsirkin" <mst@...hat.com>,
 Jason Wang <jasowang@...hat.com>, Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
 Eugenio Pérez <eperezma@...hat.com>,
 Juergen Gross <jgross@...e.com>, Stefano Stabellini
 <sstabellini@...nel.org>,
 Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>,
 Alexander Potapenko <glider@...gle.com>, Marco Elver <elver@...gle.com>,
 Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [PATCH v1 1/3] mm: pass meminit_context to __free_pages_core()

On 07.06.24 11:09, David Hildenbrand wrote:
> In preparation for further changes, let's teach __free_pages_core()
> about the differences of memory hotplug handling.
> 
> Move the memory hotplug specific handling from generic_online_page() to
> __free_pages_core(), use adjust_managed_page_count() on the memory
> hotplug path, and spell out why memory freed via memblock
> cannot currently use adjust_managed_page_count().
> 
> Signed-off-by: David Hildenbrand <david@...hat.com>
> ---
>   mm/internal.h       |  3 ++-
>   mm/kmsan/init.c     |  2 +-
>   mm/memory_hotplug.c |  9 +--------
>   mm/mm_init.c        |  4 ++--
>   mm/page_alloc.c     | 17 +++++++++++++++--
>   5 files changed, 21 insertions(+), 14 deletions(-)
> 
> diff --git a/mm/internal.h b/mm/internal.h
> index 12e95fdf61e90..3fdee779205ab 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -604,7 +604,8 @@ extern void __putback_isolated_page(struct page *page, unsigned int order,
>   				    int mt);
>   extern void memblock_free_pages(struct page *page, unsigned long pfn,
>   					unsigned int order);
> -extern void __free_pages_core(struct page *page, unsigned int order);
> +extern void __free_pages_core(struct page *page, unsigned int order,
> +		enum meminit_context);
>   
>   /*
>    * This will have no effect, other than possibly generating a warning, if the
> diff --git a/mm/kmsan/init.c b/mm/kmsan/init.c
> index 3ac3b8921d36f..ca79636f858e5 100644
> --- a/mm/kmsan/init.c
> +++ b/mm/kmsan/init.c
> @@ -172,7 +172,7 @@ static void do_collection(void)
>   		shadow = smallstack_pop(&collect);
>   		origin = smallstack_pop(&collect);
>   		kmsan_setup_meta(page, shadow, origin, collect.order);
> -		__free_pages_core(page, collect.order);
> +		__free_pages_core(page, collect.order, MEMINIT_EARLY);
>   	}
>   }
>   
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 171ad975c7cfd..27e3be75edcf7 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -630,14 +630,7 @@ EXPORT_SYMBOL_GPL(restore_online_page_callback);
>   
>   void generic_online_page(struct page *page, unsigned int order)
>   {
> -	/*
> -	 * Freeing the page with debug_pagealloc enabled will try to unmap it,
> -	 * so we should map it first. This is better than introducing a special
> -	 * case in page freeing fast path.
> -	 */
> -	debug_pagealloc_map_pages(page, 1 << order);
> -	__free_pages_core(page, order);
> -	totalram_pages_add(1UL << order);
> +	__free_pages_core(page, order, MEMINIT_HOTPLUG);
>   }
>   EXPORT_SYMBOL_GPL(generic_online_page);
>   
> diff --git a/mm/mm_init.c b/mm/mm_init.c
> index 019193b0d8703..feb5b6e8c8875 100644
> --- a/mm/mm_init.c
> +++ b/mm/mm_init.c
> @@ -1938,7 +1938,7 @@ static void __init deferred_free_range(unsigned long pfn,
>   	for (i = 0; i < nr_pages; i++, page++, pfn++) {
>   		if (pageblock_aligned(pfn))
>   			set_pageblock_migratetype(page, MIGRATE_MOVABLE);
> -		__free_pages_core(page, 0);
> +		__free_pages_core(page, 0, MEMINIT_EARLY);
>   	}
>   }

The build bot just reminded me that I missed another case in this function:
(CONFIG_DEFERRED_STRUCT_PAGE_INIT)

diff --git a/mm/mm_init.c b/mm/mm_init.c
index feb5b6e8c8875..5a0752261a795 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -1928,7 +1928,7 @@ static void __init deferred_free_range(unsigned long pfn,
         if (nr_pages == MAX_ORDER_NR_PAGES && IS_MAX_ORDER_ALIGNED(pfn)) {
                 for (i = 0; i < nr_pages; i += pageblock_nr_pages)
                         set_pageblock_migratetype(page + i, MIGRATE_MOVABLE);
-               __free_pages_core(page, MAX_PAGE_ORDER);
+               __free_pages_core(page, MAX_PAGE_ORDER, MEMINIT_EARLY);
                 return;
         }
  

-- 
Cheers,

David / dhildenb