linux-kernel - [PATCH 2/4] mm: simplify and rename mm flags function for clarity

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Message-ID: <2e956728c7af82d66286429c040451905b6acc7b.1761757731.git.lorenzo.stoakes@oracle.com>
Date: Wed, 29 Oct 2025 17:49:36 +0000
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Muchun Song <muchun.song@...ux.dev>, Oscar Salvador <osalvador@...e.de>,
        David Hildenbrand <david@...hat.com>,
        "Liam R . Howlett" <Liam.Howlett@...cle.com>,
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        Qi Zheng <zhengqi.arch@...edance.com>, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH 2/4] mm: simplify and rename mm flags function for clarity

The __mm_flags_set_word() function is slightly ambiguous - we use 'set' to
refer to setting individual bits (such as in mm_flags_set()) but here we
use it to refer to overwriting the value altogether.

Rename it to __mm_flags_overwrite_word() to eliniate this ambiguity.

We additionally simplify the functions, eliminating unnecessary
bitmap_xxx() operations (the compiler would have optimised these out but
it's worth being as clear as we can be here).

Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
---
 include/linux/mm_types.h | 14 +++++---------
 kernel/fork.c            |  4 ++--
 2 files changed, 7 insertions(+), 11 deletions(-)

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 5021047485a9..b47bd829ec9d 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -1289,15 +1289,13 @@ struct mm_struct {
 	unsigned long cpu_bitmap[];
 };
 
-/* Set the first system word of mm flags, non-atomically. */
-static inline void __mm_flags_set_word(struct mm_struct *mm, unsigned long value)
+/* Copy value to the first system word of mm flags, non-atomically. */
+static inline void __mm_flags_overwrite_word(struct mm_struct *mm, unsigned long value)
 {
-	unsigned long *bitmap = ACCESS_PRIVATE(&mm->flags, __mm_flags);
-
-	bitmap_copy(bitmap, &value, BITS_PER_LONG);
+	*ACCESS_PRIVATE(&mm->flags, __mm_flags) = value;
 }
 
-/* Obtain a read-only view of the bitmap. */
+/* Obtain a read-only view of the mm flags bitmap. */
 static inline const unsigned long *__mm_flags_get_bitmap(const struct mm_struct *mm)
 {
 	return (const unsigned long *)ACCESS_PRIVATE(&mm->flags, __mm_flags);
@@ -1306,9 +1304,7 @@ static inline const unsigned long *__mm_flags_get_bitmap(const struct mm_struct
 /* Read the first system word of mm flags, non-atomically. */
 static inline unsigned long __mm_flags_get_word(const struct mm_struct *mm)
 {
-	const unsigned long *bitmap = __mm_flags_get_bitmap(mm);
-
-	return bitmap_read(bitmap, 0, BITS_PER_LONG);
+	return *__mm_flags_get_bitmap(mm);
 }
 
 /*
diff --git a/kernel/fork.c b/kernel/fork.c
index dd0bb5fe4305..5e3309a2332c 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1061,10 +1061,10 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
 	if (current->mm) {
 		unsigned long flags = __mm_flags_get_word(current->mm);
 
-		__mm_flags_set_word(mm, mmf_init_legacy_flags(flags));
+		__mm_flags_overwrite_word(mm, mmf_init_legacy_flags(flags));
 		mm->def_flags = current->mm->def_flags & VM_INIT_DEF_MASK;
 	} else {
-		__mm_flags_set_word(mm, default_dump_filter);
+		__mm_flags_overwrite_word(mm, default_dump_filter);
 		mm->def_flags = 0;
 	}
 
-- 
2.51.0