linux-kernel - [PATCH v2] fs: hide names_cache behind runtime const machinery

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Message-ID: <20251201083226.268846-1-mjguzik@gmail.com>
Date: Mon,  1 Dec 2025 09:32:26 +0100
From: Mateusz Guzik <mjguzik@...il.com>
To: viro@...iv.linux.org.uk
Cc: brauner@...nel.org,
	jack@...e.cz,
	linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	Mateusz Guzik <mjguzik@...il.com>
Subject: [PATCH v2] fs: hide names_cache behind runtime const machinery

s/names_cachep/names_cache/ for consistency with dentry cache.

Signed-off-by: Mateusz Guzik <mjguzik@...il.com>
---

v2:
- rebased on top of work.filename-refcnt

ACHTUNG: there is a change queued for 6.19 merge window which treats
dentry cache the same way:
commit 21b561dab1406e63740ebe240c7b69f19e1bcf58
Author: Mateusz Guzik <mjguzik@...il.com>
Date:   Wed Nov 5 16:36:22 2025 +0100

    fs: hide dentry_cache behind runtime const machinery

which would result in a merge conflict in vmlinux.lds.h. thus I
cherry-picked before generating the diff to avoid the issue for later.

 fs/namei.c                        | 16 ++++++++++------
 include/asm-generic/vmlinux.lds.h |  3 ++-
 2 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index d6eac90084e1..eff4cbffe241 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -41,6 +41,8 @@
 #include <linux/init_task.h>
 #include <linux/uaccess.h>
 
+#include <asm/runtime-const.h>
+
 #include "internal.h"
 #include "mount.h"
 
@@ -124,23 +126,25 @@
  */
 
 /* SLAB cache for struct filename instances */
-static struct kmem_cache *names_cachep __ro_after_init;
+static struct kmem_cache *__names_cache __ro_after_init;
+#define names_cache	runtime_const_ptr(__names_cache)
 
 void __init filename_init(void)
 {
-	names_cachep = kmem_cache_create_usercopy("names_cache", sizeof(struct filename), 0,
-			SLAB_HWCACHE_ALIGN|SLAB_PANIC, offsetof(struct filename, iname),
-						EMBEDDED_NAME_MAX, NULL);
+	__names_cache = kmem_cache_create_usercopy("names_cache", sizeof(struct filename), 0,
+			 SLAB_HWCACHE_ALIGN|SLAB_PANIC, offsetof(struct filename, iname),
+			 EMBEDDED_NAME_MAX, NULL);
+	runtime_const_init(ptr, __names_cache);
 }
 
 static inline struct filename *alloc_filename(void)
 {
-	return kmem_cache_alloc(names_cachep, GFP_KERNEL);
+	return kmem_cache_alloc(names_cache, GFP_KERNEL);
 }
 
 static inline void free_filename(struct filename *p)
 {
-	kmem_cache_free(names_cachep, p);
+	kmem_cache_free(names_cache, p);
 }
 
 static inline void initname(struct filename *name)
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 20939d2445e7..3abd76ac723a 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -956,7 +956,8 @@ defined(CONFIG_AUTOFDO_CLANG) || defined(CONFIG_PROPELLER_CLANG)
 #define RUNTIME_CONST_VARIABLES						\
 		RUNTIME_CONST(shift, d_hash_shift)			\
 		RUNTIME_CONST(ptr, dentry_hashtable)			\
-		RUNTIME_CONST(ptr, __dentry_cache)
+		RUNTIME_CONST(ptr, __dentry_cache)			\
+		RUNTIME_CONST(ptr, __names_cache)
 
 /* Alignment must be consistent with (kunit_suite *) in include/kunit/test.h */
 #define KUNIT_TABLE()							\
-- 
2.48.1