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Message-ID: <a319a71d57a2af3930051c46dad954d03d55857d.1763126447.git.lorenzo.stoakes@oracle.com>
Date: Fri, 14 Nov 2025 13:26:09 +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>,
Vlastimil Babka <vbabka@...e.cz>, Mike Rapoport <rppt@...nel.org>,
Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>,
Axel Rasmussen <axelrasmussen@...gle.com>,
Yuanchu Xie <yuanchu@...gle.com>, Wei Xu <weixugc@...gle.com>,
Peter Xu <peterx@...hat.com>, Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
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Kees Cook <kees@...nel.org>, Matthew Wilcox <willy@...radead.org>,
Jason Gunthorpe <jgg@...pe.ca>, John Hubbard <jhubbard@...dia.com>,
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Baolin Wang <baolin.wang@...ux.alibaba.com>,
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Alistair Popple <apopple@...dia.com>, Pedro Falcato <pfalcato@...e.de>,
Shakeel Butt <shakeel.butt@...ux.dev>,
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Kemeng Shi <shikemeng@...weicloud.com>,
Kairui Song <kasong@...cent.com>, Nhat Pham <nphamcs@...il.com>,
Baoquan He <bhe@...hat.com>, Chris Li <chrisl@...nel.org>,
Johannes Weiner <hannes@...xchg.org>,
Qi Zheng <zhengqi.arch@...edance.com>, linux-kernel@...r.kernel.org,
linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>,
Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
Bjorn Roy Baron <bjorn3_gh@...tonmail.com>,
Benno Lossin <lossin@...nel.org>,
Andreas Hindborg <a.hindborg@...nel.org>,
Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>,
Danilo Krummrich <dakr@...nel.org>, rust-for-linux@...r.kernel.org
Subject: [PATCH v2 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 eliminate 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 4f66a3206a63..3550672e0f9e 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -1314,15 +1314,13 @@ 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);
@@ -1331,9 +1329,7 @@ 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
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