linux-kernel - [PATCH 26/32] nsfs: add current_in

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Message-Id: <20250910-work-namespace-v1-26-4dd56e7359d8@kernel.org>
Date: Wed, 10 Sep 2025 16:37:11 +0200
From: Christian Brauner <brauner@...nel.org>
To: Jan Kara <jack@...e.cz>, Amir Goldstein <amir73il@...il.com>, 
 linux-fsdevel@...r.kernel.org
Cc: Josef Bacik <josef@...icpanda.com>, Jeff Layton <jlayton@...nel.org>, 
 Mike Yuan <me@...dnzj.com>, 
 Zbigniew Jędrzejewski-Szmek <zbyszek@...waw.pl>, 
 Lennart Poettering <mzxreary@...inter.de>, 
 Daan De Meyer <daan.j.demeyer@...il.com>, Aleksa Sarai <cyphar@...har.com>, 
 Alexander Viro <viro@...iv.linux.org.uk>, Jens Axboe <axboe@...nel.dk>, 
 Tejun Heo <tj@...nel.org>, Johannes Weiner <hannes@...xchg.org>, 
 Michal Koutný <mkoutny@...e.com>, 
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
 Chuck Lever <chuck.lever@...cle.com>, linux-nfs@...r.kernel.org, 
 linux-kselftest@...r.kernel.org, linux-block@...r.kernel.org, 
 linux-kernel@...r.kernel.org, cgroups@...r.kernel.org, 
 netdev@...r.kernel.org, Christian Brauner <brauner@...nel.org>
Subject: [PATCH 26/32] nsfs: add current_in_namespace()

Add a helper to easily check whether a given namespace is the caller's
current namespace. This is currently open-coded in a lot of places.
Simply switch on the type and compare the results.

Signed-off-by: Christian Brauner <brauner@...nel.org>
---
 include/linux/nsfs.h | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/include/linux/nsfs.h b/include/linux/nsfs.h
index fb84aa538091..e5a5fa83d36b 100644
--- a/include/linux/nsfs.h
+++ b/include/linux/nsfs.h
@@ -5,6 +5,8 @@
 #define _LINUX_NSFS_H
 
 #include <linux/ns_common.h>
+#include <linux/cred.h>
+#include <linux/pid_namespace.h>
 
 struct path;
 struct task_struct;
@@ -22,5 +24,17 @@ int ns_get_name(char *buf, size_t size, struct task_struct *task,
 			const struct proc_ns_operations *ns_ops);
 void nsfs_init(void);
 
-#endif /* _LINUX_NSFS_H */
+#define __current_namespace_from_type(__ns)				\
+	_Generic((__ns),						\
+		struct cgroup_namespace *: current->nsproxy->cgroup_ns,	\
+		struct ipc_namespace *:    current->nsproxy->ipc_ns,	\
+		struct net *:              current->nsproxy->net_ns,	\
+		struct pid_namespace *:    task_active_pid_ns(current),	\
+		struct mnt_namespace *:    current->nsproxy->mnt_ns,	\
+		struct time_namespace *:   current->nsproxy->time_ns,	\
+		struct user_namespace *:   current_user_ns(),		\
+		struct uts_namespace *:    current->nsproxy->uts_ns)
+
+#define current_in_namespace(__ns) (__current_namespace_from_type(__ns) == __ns)
 
+#endif /* _LINUX_NSFS_H */

-- 
2.47.3