linux-kernel - [PATCH mm-new 1/1] mm: clean up is_guard_pte

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Message-ID: <20250924045830.3817-1-lance.yang@linux.dev>
Date: Wed, 24 Sep 2025 12:58:30 +0800
From: Lance Yang <lance.yang@...ux.dev>
To: akpm@...ux-foundation.org
Cc: richard.weiyang@...il.com,
	Liam.Howlett@...cle.com,
	baohua@...nel.org,
	baolin.wang@...ux.alibaba.com,
	david@...hat.com,
	dev.jain@....com,
	hughd@...gle.com,
	ioworker0@...il.com,
	kasong@...cent.com,
	kirill@...temov.name,
	lance.yang@...ux.dev,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	lorenzo.stoakes@...cle.com,
	mpenttil@...hat.com,
	npache@...hat.com,
	ryan.roberts@....com,
	ziy@...dia.com
Subject: [PATCH mm-new 1/1] mm: clean up is_guard_pte_marker()

From: Lance Yang <lance.yang@...ux.dev>

Let's simplify the implementation. The current code is redundant as it
effectively expands to:

  is_swap_pte(pte) &&
  is_pte_marker_entry(...) && // from is_pte_marker()
  is_pte_marker_entry(...)    // from is_guard_swp_entry()

While a modern compiler could likely optimize this away, let's have clean
code and not rely on it.

Reviewed-by: Wei Yang <richard.weiyang@...il.com>
Reviewed-by: Zi Yan <ziy@...dia.com>
Acked-by: David Hildenbrand <david@...hat.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Signed-off-by: Lance Yang <lance.yang@...ux.dev>
---
This patch is split from the series[1]. The cleanup can be applied
independently because is_guard_pte_marker() is no longer exposed.

The original Acked-by and Reviewed-by tags are kept as the change is
trivial enough.

[1] https://lore.kernel.org/linux-mm/20250918050431.36855-1-lance.yang@linux.dev

 mm/madvise.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/madvise.c b/mm/madvise.c
index 35ed4ab0d7c5..fb1c86e630b6 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -1071,8 +1071,8 @@ static bool is_valid_guard_vma(struct vm_area_struct *vma, bool allow_locked)
 
 static bool is_guard_pte_marker(pte_t ptent)
 {
-	return is_pte_marker(ptent) &&
-		is_guard_swp_entry(pte_to_swp_entry(ptent));
+	return is_swap_pte(ptent) &&
+	       is_guard_swp_entry(pte_to_swp_entry(ptent));
 }
 
 static int guard_install_pud_entry(pud_t *pud, unsigned long addr,
-- 
2.49.0