linux-kernel - Re: [PATCH v3 1/4] mm/page_isolation: make page isolation a standalone bit.

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Message-ID: <E40B7150-70AA-4D51-B5F3-4FF22AD887FD@nvidia.com>
Date: Fri, 09 May 2025 09:57:42 -0400
From: Zi Yan <ziy@...dia.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Johannes Weiner <hannes@...xchg.org>, linux-mm@...ck.org,
 David Hildenbrand <david@...hat.com>, Oscar Salvador <osalvador@...e.de>,
 Vlastimil Babka <vbabka@...e.cz>,
 Baolin Wang <baolin.wang@...ux.alibaba.com>,
 "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
 Mel Gorman <mgorman@...hsingularity.net>,
 Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>,
 Brendan Jackman <jackmanb@...gle.com>, Richard Chang <richardycc@...gle.com>,
 linux-kernel@...r.kernel.org, Zi Yan <ziy@...dia.com>
Subject: Re: [PATCH v3 1/4] mm/page_isolation: make page isolation a
 standalone bit.

On 8 May 2025, at 16:22, Zi Yan wrote:

> On 7 May 2025, at 17:10, Zi Yan wrote:
>
>> During page isolation, the original migratetype is overwritten, since
>> MIGRATE_* are enums and stored in pageblock bitmaps. Change
>> MIGRATE_ISOLATE to be stored a standalone bit, PB_migrate_isolate, like
>> PB_migrate_skip, so that migratetype is not lost during pageblock
>> isolation. pageblock bits needs to be word aligned, so expand
>> the number of pageblock bits from 4 to 8 and make PB_migrate_isolate bit 7.
>>
>> Signed-off-by: Zi Yan <ziy@...dia.com>
>> ---
>>  include/linux/mmzone.h          | 17 ++++++++++----
>>  include/linux/page-isolation.h  |  2 +-
>>  include/linux/pageblock-flags.h | 33 +++++++++++++++++++++++++-
>>  mm/page_alloc.c                 | 41 ++++++++++++++++++++++++++++++++-
>>  4 files changed, 86 insertions(+), 7 deletions(-)
>>
>
> Here is the fixup 1/3 to address Johannes’ comments.
>
> From 7eb1d9fa58fdab216862436181e5d2baf2958c54 Mon Sep 17 00:00:00 2001
> From: Zi Yan <ziy@...dia.com>
> Date: Thu, 8 May 2025 12:05:59 -0400
> Subject: [PATCH] fixup for mm/page_isolation: make page isolation a standalone
>  bit
>
> 1. keep the original is_migrate_isolate_page()
> 2. move {get,set,clear}_pageblock_isolate() to mm/page_isolation.c
> 3. use a single version for get_pageblock_migratetype() and
>    get_pfnblock_migratetype().
>
> Signed-off-by: Zi Yan <ziy@...dia.com>
> ---
>  include/linux/mmzone.h          |  6 ------
>  include/linux/page-isolation.h  |  2 +-
>  include/linux/pageblock-flags.h | 24 ------------------------
>  mm/page_alloc.c                 | 25 ++++++++++---------------
>  mm/page_isolation.c             | 17 +++++++++++++++++
>  5 files changed, 28 insertions(+), 46 deletions(-)
>

Hi Andrew,

This fixup gets rid of the unused function warning[1].

BTW, this series gets several fixups. Let me know if you think a V4
is necessary. Thanks.

[1] https://lore.kernel.org/linux-mm/202505092126.yRGhLhg1-lkp@intel.com/

>From 126d116cb737bf3d8c475460b9b48edc6696e6dc Mon Sep 17 00:00:00 2001
From: Zi Yan <ziy@...dia.com>
Date: Fri, 9 May 2025 09:29:09 -0400
Subject: [PATCH] fix unused function warnings

1. add __maybe_unused to get_pageblock_isolate(), which is used in
   VM_BUG_ON only.
2. remove unused set_pageblock_isolate().

Signed-off-by: Zi Yan <ziy@...dia.com>
---
 mm/page_isolation.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index b0f83a7c508d..ce7e38c9f839 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -15,7 +15,7 @@
 #define CREATE_TRACE_POINTS
 #include <trace/events/page_isolation.h>

-static inline bool get_pageblock_isolate(struct page *page)
+static inline bool __maybe_unused get_pageblock_isolate(struct page *page)
 {
 	return get_pfnblock_flags_mask(page, page_to_pfn(page),
 			PB_migrate_isolate_bit);
@@ -25,12 +25,6 @@ static inline void clear_pageblock_isolate(struct page *page)
 	set_pfnblock_flags_mask(page, 0, page_to_pfn(page),
 			PB_migrate_isolate_bit);
 }
-static inline void set_pageblock_isolate(struct page *page)
-{
-	set_pfnblock_flags_mask(page, PB_migrate_isolate_bit,
-			page_to_pfn(page),
-			PB_migrate_isolate_bit);
-}

 /*
  * This function checks whether the range [start_pfn, end_pfn) includes
-- 
2.47.2



--
Best Regards,
Yan, Zi