[PATCH 12/17] ns: make all reference counts on initial namespace a nop
From: Christian Brauner <brauner@kernel.org>
Date: 2025-11-10 15:09:43
Also in:
bpf, cgroups, linux-fsdevel, lkml
Subsystem:
the rest · Maintainer:
Linus Torvalds
They are always active so no need to needlessly cacheline ping-pong. Signed-off-by: Christian Brauner <brauner@kernel.org> --- include/linux/ns_common.h | 25 ++++++++++++++++++++++--- 1 file changed, 22 insertions(+), 3 deletions(-)
diff --git a/include/linux/ns_common.h b/include/linux/ns_common.h
index b9e8f21a6984..5b8f2f0163d7 100644
--- a/include/linux/ns_common.h
+++ b/include/linux/ns_common.h@@ -62,6 +62,8 @@ static __always_inline __must_check int __ns_ref_active_read(const struct ns_com static __always_inline __must_check bool __ns_ref_put(struct ns_common *ns) { + if (is_ns_init_id(ns)) + return false; if (refcount_dec_and_test(&ns->__ns_ref)) { VFS_WARN_ON_ONCE(__ns_ref_active_read(ns)); return true;
@@ -71,6 +73,8 @@ static __always_inline __must_check bool __ns_ref_put(struct ns_common *ns) static __always_inline __must_check bool __ns_ref_get(struct ns_common *ns) { + if (is_ns_init_id(ns)) + return true; if (refcount_inc_not_zero(&ns->__ns_ref)) return true; VFS_WARN_ON_ONCE(__ns_ref_active_read(ns));
@@ -82,12 +86,27 @@ static __always_inline __must_check int __ns_ref_read(const struct ns_common *ns return refcount_read(&ns->__ns_ref); } +static __always_inline void __ns_ref_inc(struct ns_common *ns) +{ + if (is_ns_init_id(ns)) + return; + refcount_inc(&ns->__ns_ref); +} + +static __always_inline __must_check bool __ns_ref_dec_and_lock(struct ns_common *ns, + spinlock_t *ns_lock) +{ + if (is_ns_init_id(ns)) + return false; + return refcount_dec_and_lock(&ns->__ns_ref, ns_lock); +} + #define ns_ref_read(__ns) __ns_ref_read(to_ns_common((__ns))) -#define ns_ref_inc(__ns) refcount_inc(&to_ns_common((__ns))->__ns_ref) +#define ns_ref_inc(__ns) __ns_ref_inc(to_ns_common((__ns))) #define ns_ref_get(__ns) __ns_ref_get(to_ns_common((__ns))) #define ns_ref_put(__ns) __ns_ref_put(to_ns_common((__ns))) -#define ns_ref_put_and_lock(__ns, __lock) \ - refcount_dec_and_lock(&to_ns_common((__ns))->__ns_ref, (__lock)) +#define ns_ref_put_and_lock(__ns, __ns_lock) \ + __ns_ref_dec_and_lock(to_ns_common((__ns)), __ns_lock) #define ns_ref_active_read(__ns) \ ((__ns) ? __ns_ref_active_read(to_ns_common(__ns)) : 0)
--
2.47.3