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Message-ID: <20230929081938.GT3303@kernel.org>
Date: Fri, 29 Sep 2023 11:19:38 +0300
From: Mike Rapoport <rppt@...nel.org>
To: Yajun Deng <yajun.deng@...ux.dev>
Cc: akpm@...ux-foundation.org, mike.kravetz@...cle.com,
muchun.song@...ux.dev, willy@...radead.org, david@...hat.com,
linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 1/2] mm: pass page count and reserved to
__init_single_page
On Thu, Sep 28, 2023 at 04:33:01PM +0800, Yajun Deng wrote:
> Subject: mm: pass page count and reserved to __init_single_page
We add pass flags that tell __init_single_page() how to initialize page
count and PG_Reserved, I think a better subject would be:
mm: allow optional initialization of page count and PG_reserved flag
> When we init a single page, we need to mark that page reserved when it
> is reserved. And some pages need to reset page count, such as compound
> pages.
>
> Introduce enum init_page_flags, the caller will init page count and mark
> page reserved by passing INIT_PAGE_COUNT and INIT_PAGE_RESERVED.
This does not really describe why the change is needed. How about
__init_single_page() unconditionally resets page count which is unnecessary
for reserved pages.
To allow skipping page count initialization and marking a page reserved in
one go add flags parameter to __init_single_page().
No functional changes.
> Signed-off-by: Yajun Deng <yajun.deng@...ux.dev>
> ---
> v4: move the changes of __init_zone_device_page().
> v3: Introduce enum init_page_flags.
> v2: Introduce INIT_PAGE_COUNT and INIT_PAGE_RESERVED.
> v1: https://lore.kernel.org/all/20230922070923.355656-1-yajun.deng@linux.dev/
> ---
> mm/hugetlb.c | 2 +-
> mm/internal.h | 8 +++++++-
> mm/mm_init.c | 24 +++++++++++++-----------
> 3 files changed, 21 insertions(+), 13 deletions(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index a82dc37669b0..bb9c334a8392 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -3196,7 +3196,7 @@ static void __init hugetlb_folio_init_tail_vmemmap(struct folio *folio,
> for (pfn = head_pfn + start_page_number; pfn < end_pfn; pfn++) {
> struct page *page = pfn_to_page(pfn);
>
> - __init_single_page(page, pfn, zone, nid);
> + __init_single_page(page, pfn, zone, nid, INIT_PAGE_COUNT);
> prep_compound_tail((struct page *)folio, pfn - head_pfn);
> ret = page_ref_freeze(page, 1);
> VM_BUG_ON(!ret);
> diff --git a/mm/internal.h b/mm/internal.h
> index d7916f1e9e98..449891ad7fdb 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -1209,8 +1209,14 @@ struct vma_prepare {
> struct vm_area_struct *remove2;
> };
>
> +enum init_page_flags {
enum page_init_flags please
> + INIT_PAGE_COUNT = (1 << 0),
> + INIT_PAGE_RESERVED = (1 << 1),
> +};
> +
> void __meminit __init_single_page(struct page *page, unsigned long pfn,
> - unsigned long zone, int nid);
> + unsigned long zone, int nid,
> + enum init_page_flags flags);
>
> /* shrinker related functions */
> unsigned long shrink_slab(gfp_t gfp_mask, int nid, struct mem_cgroup *memcg,
> diff --git a/mm/mm_init.c b/mm/mm_init.c
> index 06a72c223bce..9716c8a7ade9 100644
> --- a/mm/mm_init.c
> +++ b/mm/mm_init.c
> @@ -557,11 +557,11 @@ static void __init find_zone_movable_pfns_for_nodes(void)
> }
>
> void __meminit __init_single_page(struct page *page, unsigned long pfn,
> - unsigned long zone, int nid)
> + unsigned long zone, int nid,
> + enum init_page_flags flags)
> {
> mm_zero_struct_page(page);
> set_page_links(page, zone, nid, pfn);
> - init_page_count(page);
> page_mapcount_reset(page);
> page_cpupid_reset_last(page);
> page_kasan_tag_reset(page);
> @@ -572,6 +572,10 @@ void __meminit __init_single_page(struct page *page, unsigned long pfn,
> if (!is_highmem_idx(zone))
> set_page_address(page, __va(pfn << PAGE_SHIFT));
> #endif
> + if (flags & INIT_PAGE_COUNT)
> + init_page_count(page);
> + if (flags & INIT_PAGE_RESERVED)
> + __SetPageReserved(page);
> }
>
> #ifdef CONFIG_NUMA
> @@ -714,7 +718,7 @@ static void __meminit init_reserved_page(unsigned long pfn, int nid)
> if (zone_spans_pfn(zone, pfn))
> break;
> }
> - __init_single_page(pfn_to_page(pfn), pfn, zid, nid);
> + __init_single_page(pfn_to_page(pfn), pfn, zid, nid, INIT_PAGE_COUNT);
There is __SetPageReserved call a few lines below, it can be folded here.
> }
> #else
> static inline void pgdat_set_deferred_range(pg_data_t *pgdat) {}
> @@ -821,8 +825,8 @@ static void __init init_unavailable_range(unsigned long spfn,
> pfn = pageblock_end_pfn(pfn) - 1;
> continue;
> }
> - __init_single_page(pfn_to_page(pfn), pfn, zone, node);
> - __SetPageReserved(pfn_to_page(pfn));
> + __init_single_page(pfn_to_page(pfn), pfn, zone, node,
> + INIT_PAGE_COUNT | INIT_PAGE_RESERVED);
> pgcnt++;
> }
>
> @@ -884,7 +888,7 @@ void __meminit memmap_init_range(unsigned long size, int nid, unsigned long zone
> }
>
> page = pfn_to_page(pfn);
> - __init_single_page(page, pfn, zone, nid);
> + __init_single_page(page, pfn, zone, nid, INIT_PAGE_COUNT);
> if (context == MEMINIT_HOTPLUG)
> __SetPageReserved(page);
>
> @@ -967,9 +971,6 @@ static void __ref __init_zone_device_page(struct page *page, unsigned long pfn,
> unsigned long zone_idx, int nid,
> struct dev_pagemap *pgmap)
> {
> -
> - __init_single_page(page, pfn, zone_idx, nid);
> -
> /*
> * Mark page reserved as it will need to wait for onlining
> * phase for it to be fully associated with a zone.
> @@ -977,7 +978,8 @@ static void __ref __init_zone_device_page(struct page *page, unsigned long pfn,
> * We can use the non-atomic __set_bit operation for setting
> * the flag as we are still initializing the pages.
> */
> - __SetPageReserved(page);
> + __init_single_page(page, pfn, zone_idx, nid,
> + INIT_PAGE_COUNT | INIT_PAGE_RESERVED);
>
> /*
> * ZONE_DEVICE pages union ->lru with a ->pgmap back pointer
> @@ -2058,7 +2060,7 @@ static unsigned long __init deferred_init_pages(struct zone *zone,
> } else {
> page++;
> }
> - __init_single_page(page, pfn, zid, nid);
> + __init_single_page(page, pfn, zid, nid, INIT_PAGE_COUNT);
> nr_pages++;
> }
> return (nr_pages);
> --
> 2.25.1
>
--
Sincerely yours,
Mike.
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