linux-kernel - [RFC PATCH 05/11] mm: shmem: kick khugepaged for enabling none-PMD-sized shmem mTHPs

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Message-ID: <7c8ee99eb146a9e8abd20d110cb591d33fa1ebae.1755677674.git.baolin.wang@linux.alibaba.com>
Date: Wed, 20 Aug 2025 17:07:16 +0800
From: Baolin Wang <baolin.wang@...ux.alibaba.com>
To: akpm@...ux-foundation.org,
	hughd@...gle.com,
	david@...hat.com,
	lorenzo.stoakes@...cle.com
Cc: ziy@...dia.com,
	Liam.Howlett@...cle.com,
	npache@...hat.com,
	ryan.roberts@....com,
	dev.jain@....com,
	baohua@...nel.org,
	baolin.wang@...ux.alibaba.com,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: [RFC PATCH 05/11] mm: shmem: kick khugepaged for enabling none-PMD-sized shmem mTHPs

When only non-PMD-sized mTHP is enabled (such as only 64K mTHP enabled),
we should also allow kicking khugepaged to attempt scanning and collapsing
64K shmem mTHP. Modify shmem_hpage_pmd_enabled() to support shmem mTHP
collapse, and while we are at it, rename it to make the function name
more clear.

Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
---
 include/linux/shmem_fs.h |  4 ++--
 mm/khugepaged.c          |  2 +-
 mm/shmem.c               | 10 +++++-----
 3 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
index 6d0f9c599ff7..cbe46e0c8bce 100644
--- a/include/linux/shmem_fs.h
+++ b/include/linux/shmem_fs.h
@@ -118,7 +118,7 @@ int shmem_unuse(unsigned int type);
 unsigned long shmem_allowable_huge_orders(struct inode *inode,
 				struct vm_area_struct *vma, pgoff_t index,
 				loff_t write_end, bool shmem_huge_force);
-bool shmem_hpage_pmd_enabled(void);
+bool shmem_hpage_enabled(void);
 #else
 static inline unsigned long shmem_allowable_huge_orders(struct inode *inode,
 				struct vm_area_struct *vma, pgoff_t index,
@@ -127,7 +127,7 @@ static inline unsigned long shmem_allowable_huge_orders(struct inode *inode,
 	return 0;
 }
 
-static inline bool shmem_hpage_pmd_enabled(void)
+static inline bool shmem_hpage_enabled(void)
 {
 	return false;
 }
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 53ca7bb72fbc..eb0b433d6ccb 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -453,7 +453,7 @@ static bool hugepage_enabled(void)
 	if (READ_ONCE(huge_anon_orders_inherit) &&
 	    hugepage_global_enabled())
 		return true;
-	if (IS_ENABLED(CONFIG_SHMEM) && shmem_hpage_pmd_enabled())
+	if (IS_ENABLED(CONFIG_SHMEM) && shmem_hpage_enabled())
 		return true;
 	return false;
 }
diff --git a/mm/shmem.c b/mm/shmem.c
index 13cc51df3893..a360738ab732 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1791,17 +1791,17 @@ static gfp_t limit_gfp_mask(gfp_t huge_gfp, gfp_t limit_gfp)
 }
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
-bool shmem_hpage_pmd_enabled(void)
+bool shmem_hpage_enabled(void)
 {
 	if (shmem_huge == SHMEM_HUGE_DENY)
 		return false;
-	if (test_bit(HPAGE_PMD_ORDER, &huge_shmem_orders_always))
+	if (READ_ONCE(huge_shmem_orders_always))
 		return true;
-	if (test_bit(HPAGE_PMD_ORDER, &huge_shmem_orders_madvise))
+	if (READ_ONCE(huge_shmem_orders_madvise))
 		return true;
-	if (test_bit(HPAGE_PMD_ORDER, &huge_shmem_orders_within_size))
+	if (READ_ONCE(huge_shmem_orders_within_size))
 		return true;
-	if (test_bit(HPAGE_PMD_ORDER, &huge_shmem_orders_inherit) &&
+	if (READ_ONCE(huge_shmem_orders_inherit) &&
 	    shmem_huge != SHMEM_HUGE_NEVER)
 		return true;
 
-- 
2.43.5