linux-kernel - Re: [PATCH 1/1] mm/madvise: enhance lazyfreeing with mTHP in madvise

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Message-Id: <20240227012127.174048-1-21cnbao@gmail.com>
Date: Tue, 27 Feb 2024 14:21:27 +1300
From: Barry Song <21cnbao@...il.com>
To: ioworker0@...il.com
Cc: 21cnbao@...il.com,
	akpm@...ux-foundation.org,
	david@...hat.com,
	fengwei.yin@...el.com,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	mhocko@...e.com,
	minchan@...nel.org,
	peterx@...hat.com,
	ryan.roberts@....com,
	shy828301@...il.com,
	songmuchun@...edance.com,
	wangkefeng.wang@...wei.com,
	zokeefe@...gle.com,
	Barry Song <v-songbaohua@...o.com>
Subject: Re: [PATCH 1/1] mm/madvise: enhance lazyfreeing with mTHP in madvise_free

> Thanks for your suggestion. I'll use folio_pte_batch() in v2.

Hi Lance,
Obviously, we both need this. While making large folio swap-in
v2, I am exporting folio_pte_batch() as below,

From: Barry Song <v-songbaohua@...o.com>
Date: Tue, 27 Feb 2024 14:05:43 +1300
Subject: [PATCH] mm: export folio_pte_batch as a couple of modules need it

MADV_FREE, MADV_PAGEOUT and some other modules might need folio_pte_batch
to check if a range of PTEs are completely mapped to a large folio with
contiguous physcial offset.

Cc: Lance Yang <ioworker0@...il.com>
Cc: Ryan Roberts <ryan.roberts@....com>
Cc: David Hildenbrand <david@...hat.com>
Signed-off-by: Barry Song <v-songbaohua@...o.com>
---
 mm/internal.h | 13 +++++++++++++
 mm/memory.c   |  2 +-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/mm/internal.h b/mm/internal.h
index 36c11ea41f47..7e11aea3eda9 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -83,6 +83,19 @@ static inline void *folio_raw_mapping(struct folio *folio)
 	return (void *)(mapping & ~PAGE_MAPPING_FLAGS);
 }
 
+/* Flags for folio_pte_batch(). */
+typedef int __bitwise fpb_t;
+
+/* Compare PTEs after pte_mkclean(), ignoring the dirty bit. */
+#define FPB_IGNORE_DIRTY		((__force fpb_t)BIT(0))
+
+/* Compare PTEs after pte_clear_soft_dirty(), ignoring the soft-dirty bit. */
+#define FPB_IGNORE_SOFT_DIRTY		((__force fpb_t)BIT(1))
+
+extern int folio_pte_batch(struct folio *folio, unsigned long addr,
+		pte_t *start_ptep, pte_t pte, int max_nr, fpb_t flags,
+		bool *any_writable);
+
 void __acct_reclaim_writeback(pg_data_t *pgdat, struct folio *folio,
 						int nr_throttled);
 static inline void acct_reclaim_writeback(struct folio *folio)
diff --git a/mm/memory.c b/mm/memory.c
index 6378f6bc22c5..dd9bd67f037a 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -989,7 +989,7 @@ static inline pte_t __pte_batch_clear_ignored(pte_t pte, fpb_t flags)
  * If "any_writable" is set, it will indicate if any other PTE besides the
  * first (given) PTE is writable.
  */
-static inline int folio_pte_batch(struct folio *folio, unsigned long addr,
+int folio_pte_batch(struct folio *folio, unsigned long addr,
 		pte_t *start_ptep, pte_t pte, int max_nr, fpb_t flags,
 		bool *any_writable)
 {
-- 
2.34.1 

> Best,
> Lance

Thanks
Barry