linux-kernel - [PATCH v4 04/12] fs: add const to pointer parameters for improved const-correctness

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Message-ID: <20250901091916.3002082-5-max.kellermann@ionos.com>
Date: Mon,  1 Sep 2025 11:19:07 +0200
From: Max Kellermann <max.kellermann@...os.com>
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Subject: [PATCH v4 04/12] fs: add const to pointer parameters for improved const-correctness

The memory management (mm) subsystem is a fundamental low-level component
of the Linux kernel. Establishing const-correctness at this foundational
level enables higher-level subsystems, such as filesystems and drivers,
to also adopt const-correctness in their interfaces. This patch lays
the groundwork for broader const-correctness throughout the kernel
by starting with the core mm subsystem.

This patch adds const qualifiers to address_space pointer parameters
in filesystem-related functions that do not modify the referenced memory,
improving type safety and enabling compiler optimizations.

Functions improved:
- mapping_tagged()
- mapping_mapped()
- mapping_writably_mapped()

Signed-off-by: Max Kellermann <max.kellermann@...os.com>
Reviewed-by: Vishal Moola (Oracle) <vishal.moola@...il.com>
---
 include/linux/fs.h | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 3b9f54446db0..8dc46337467d 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -537,7 +537,8 @@ struct address_space {
 /*
  * Returns true if any of the pages in the mapping are marked with the tag.
  */
-static inline bool mapping_tagged(struct address_space *mapping, xa_mark_t tag)
+static inline bool mapping_tagged(const struct address_space *const mapping,
+				  const xa_mark_t tag)
 {
 	return xa_marked(&mapping->i_pages, tag);
 }
@@ -585,7 +586,7 @@ static inline void i_mmap_assert_write_locked(struct address_space *mapping)
 /*
  * Might pages of this file be mapped into userspace?
  */
-static inline int mapping_mapped(struct address_space *mapping)
+static inline int mapping_mapped(const struct address_space *const mapping)
 {
 	return	!RB_EMPTY_ROOT(&mapping->i_mmap.rb_root);
 }
@@ -599,7 +600,7 @@ static inline int mapping_mapped(struct address_space *mapping)
  * If i_mmap_writable is negative, no new writable mappings are allowed. You
  * can only deny writable mappings, if none exists right now.
  */
-static inline int mapping_writably_mapped(struct address_space *mapping)
+static inline int mapping_writably_mapped(const struct address_space *const mapping)
 {
 	return atomic_read(&mapping->i_mmap_writable) > 0;
 }
-- 
2.47.2