Unverified Commit 7cd3d204 authored by Christian Brauner's avatar Christian Brauner
Browse files

ns: don't increment or decrement initial namespaces 

There's no need to bump the active reference counts of initial
namespaces as they're always active and can simply remain at 1.

Link: https://patch.msgid.link/20251109-namespace-6-19-fixes-v1-2-ae8a4ad5a3b3@kernel.org


Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent 0355dcae

include/linux/ns_common.h

+20 −3
Original line number Diff line number Diff line
@@ -141,6 +141,12 @@ static __always_inline bool is_initial_namespace(struct ns_common *ns) 
				 IPC_NS_INIT_INO - MNT_NS_INIT_INO + 1));

}



static __always_inline bool is_ns_init_id(const struct ns_common *ns)

{

	VFS_WARN_ON_ONCE(ns->ns_id == 0);

	return ns->ns_id <= NS_LAST_INIT_ID;

}



#define to_ns_common(__ns)                                    \

	_Generic((__ns),                                      \

		struct cgroup_namespace *:       &(__ns)->ns, \
@@ -285,14 +291,19 @@ void __ns_ref_active_get_owner(struct ns_common *ns); 


static __always_inline void __ns_ref_active_get(struct ns_common *ns)

{

	/* Initial namespaces are always active. */

	if (!is_ns_init_id(ns))

		WARN_ON_ONCE(atomic_add_negative(1, &ns->__ns_ref_active));

	VFS_WARN_ON_ONCE(is_initial_namespace(ns) && __ns_ref_active_read(ns) <= 0);

}

#define ns_ref_active_get(__ns) \

	do { if (__ns) __ns_ref_active_get(to_ns_common(__ns)); } while (0)



static __always_inline bool __ns_ref_active_get_not_zero(struct ns_common *ns)

{

	/* Initial namespaces are always active. */

	if (is_ns_init_id(ns))

		return true;



	if (atomic_inc_not_zero(&ns->__ns_ref_active)) {

		VFS_WARN_ON_ONCE(!__ns_ref_read(ns));

		return true;
@@ -307,6 +318,10 @@ void __ns_ref_active_put_owner(struct ns_common *ns); 


static __always_inline void __ns_ref_active_put(struct ns_common *ns)

{

	/* Initial namespaces are always active. */

	if (is_ns_init_id(ns))

		return;



	if (atomic_dec_and_test(&ns->__ns_ref_active)) {

		VFS_WARN_ON_ONCE(is_initial_namespace(ns));

		VFS_WARN_ON_ONCE(!__ns_ref_read(ns));
@@ -319,8 +334,10 @@ static __always_inline void __ns_ref_active_put(struct ns_common *ns) 
static __always_inline struct ns_common *__must_check ns_get_unless_inactive(struct ns_common *ns)

{

	VFS_WARN_ON_ONCE(__ns_ref_active_read(ns) && !__ns_ref_read(ns));

	if (!__ns_ref_active_read(ns))

	if (!__ns_ref_active_read(ns)) {

		VFS_WARN_ON_ONCE(is_ns_init_id(ns));

		return NULL;

	}

	if (!__ns_ref_get(ns))

		return NULL;

	return ns;

kernel/nscommon.c

+6 −0
Original line number Diff line number Diff line
@@ -177,6 +177,7 @@ void __ns_ref_active_put_owner(struct ns_common *ns) 
		ns = ns_owner(ns);

		if (!ns)

			return;

		VFS_WARN_ON_ONCE(is_ns_init_id(ns));

		if (!atomic_dec_and_test(&ns->__ns_ref_active))

			return;

	}
@@ -276,6 +277,10 @@ void __ns_ref_active_put_owner(struct ns_common *ns) 
 */

void __ns_ref_active_resurrect(struct ns_common *ns)

{

	/* Initial namespaces are always active. */

	if (is_ns_init_id(ns))

		return;



	/* If we didn't resurrect the namespace we're done. */

	if (atomic_fetch_add(1, &ns->__ns_ref_active))

		return;
@@ -289,6 +294,7 @@ void __ns_ref_active_resurrect(struct ns_common *ns) 
		if (!ns)

			return;



		VFS_WARN_ON_ONCE(is_ns_init_id(ns));

		if (atomic_fetch_add(1, &ns->__ns_ref_active))

			return;

	}