linux-kernel - [PATCH 07/17] nstree: use guards for ns_tree

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Message-Id: <20251110-work-namespace-nstree-fixes-v1-7-e8a9264e0fb9@kernel.org>
Date: Mon, 10 Nov 2025 16:08:19 +0100
From: Christian Brauner <brauner@...nel.org>
To: linux-fsdevel@...r.kernel.org, Josef Bacik <josef@...icpanda.com>, 
 Jeff Layton <jlayton@...nel.org>
Cc: Jann Horn <jannh@...gle.com>, 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>, 
 Amir Goldstein <amir73il@...il.com>, Tejun Heo <tj@...nel.org>, 
 Johannes Weiner <hannes@...xchg.org>, Thomas Gleixner <tglx@...utronix.de>, 
 Alexander Viro <viro@...iv.linux.org.uk>, Jan Kara <jack@...e.cz>, 
 linux-kernel@...r.kernel.org, cgroups@...r.kernel.org, bpf@...r.kernel.org, 
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
 netdev@...r.kernel.org, Arnd Bergmann <arnd@...db.de>, 
 Christian Brauner <brauner@...nel.org>
Subject: [PATCH 07/17] nstree: use guards for ns_tree_lock

Make use of the guard infrastructure for ns_tree_lock.

Signed-off-by: Christian Brauner <brauner@...nel.org>
---
 kernel/nstree.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/kernel/nstree.c b/kernel/nstree.c
index 476dd738d653..5270e0fa67a2 100644
--- a/kernel/nstree.c
+++ b/kernel/nstree.c
@@ -10,6 +10,14 @@
 
 static __cacheline_aligned_in_smp DEFINE_SEQLOCK(ns_tree_lock);
 
+DEFINE_LOCK_GUARD_0(ns_tree_writer,
+		    write_seqlock(&ns_tree_lock),
+		    write_sequnlock(&ns_tree_lock))
+
+DEFINE_LOCK_GUARD_0(ns_tree_locked_reader,
+		    read_seqlock_excl(&ns_tree_lock),
+		    read_sequnlock_excl(&ns_tree_lock))
+
 static struct ns_tree_root ns_unified_root = { /* protected by ns_tree_lock */
 	.ns_rb = RB_ROOT,
 	.ns_list_head = LIST_HEAD_INIT(ns_unified_root.ns_list_head),
@@ -193,7 +201,7 @@ void __ns_tree_add_raw(struct ns_common *ns, struct ns_tree_root *ns_tree)
 
 	VFS_WARN_ON_ONCE(!ns->ns_id);
 
-	write_seqlock(&ns_tree_lock);
+	guard(ns_tree_writer)();
 
 	/* Add to per-type tree and list */
 	node = ns_tree_node_add(&ns->ns_tree_node, ns_tree, ns_cmp);
@@ -218,7 +226,6 @@ void __ns_tree_add_raw(struct ns_common *ns, struct ns_tree_root *ns_tree)
 			VFS_WARN_ON_ONCE(ns != to_ns_common(&init_user_ns));
 		}
 	}
-	write_sequnlock(&ns_tree_lock);
 
 	VFS_WARN_ON_ONCE(node);
 }
@@ -461,9 +468,9 @@ static struct ns_common *lookup_ns_owner_at(u64 ns_id, struct ns_common *owner)
 
 	VFS_WARN_ON_ONCE(owner->ns_type != CLONE_NEWUSER);
 
-	read_seqlock_excl(&ns_tree_lock);
-	node = owner->ns_owner_root.ns_rb.rb_node;
+	guard(ns_tree_locked_reader)();
 
+	node = owner->ns_owner_root.ns_rb.rb_node;
 	while (node) {
 		struct ns_common *ns;
 
@@ -480,7 +487,6 @@ static struct ns_common *lookup_ns_owner_at(u64 ns_id, struct ns_common *owner)
 
 	if (ret)
 		ret = ns_get_unless_inactive(ret);
-	read_sequnlock_excl(&ns_tree_lock);
 	return ret;
 }
 
@@ -648,7 +654,8 @@ static struct ns_common *lookup_ns_id_at(u64 ns_id, int ns_type)
 			return NULL;
 	}
 
-	read_seqlock_excl(&ns_tree_lock);
+	guard(ns_tree_locked_reader)();
+
 	if (ns_tree)
 		node = ns_tree->ns_rb.rb_node;
 	else
@@ -677,7 +684,6 @@ static struct ns_common *lookup_ns_id_at(u64 ns_id, int ns_type)
 
 	if (ret)
 		ret = ns_get_unless_inactive(ret);
-	read_sequnlock_excl(&ns_tree_lock);
 	return ret;
 }
 

-- 
2.47.3