linux-kernel - [PATCH 5/5] seqlock: change __dentry_path() to use __SEQLOCK_READ

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Message-ID: <20251005145041.GA1266@redhat.com>
Date: Sun, 5 Oct 2025 16:50:41 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: Alexander Viro <viro@...iv.linux.org.uk>,
	Boqun Feng <boqun.feng@...il.com>,
	David Howells <dhowells@...hat.com>, Ingo Molnar <mingo@...hat.com>,
	Li RongQing <lirongqing@...du.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Waiman Long <longman@...hat.com>, Will Deacon <will@...nel.org>
Cc: linux-kernel@...r.kernel.org
Subject: [PATCH 5/5] seqlock: change __dentry_path() to use
 __SEQLOCK_READ_SECTION()

To simplify the code and make it more readable.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
 fs/d_path.c | 31 +++++++++++++------------------
 1 file changed, 13 insertions(+), 18 deletions(-)

diff --git a/fs/d_path.c b/fs/d_path.c
index bb365511066b..0dab1ab1e78d 100644
--- a/fs/d_path.c
+++ b/fs/d_path.c
@@ -332,28 +332,23 @@ static char *__dentry_path(const struct dentry *d, struct prepend_buffer *p)
 {
 	const struct dentry *dentry;
 	struct prepend_buffer b;
-	int seq = 0;
 
 	rcu_read_lock();
-restart:
-	dentry = d;
-	b = *p;
-	read_seqbegin_or_lock(&rename_lock, &seq);
-	while (!IS_ROOT(dentry)) {
-		const struct dentry *parent = dentry->d_parent;
+	__SEQLOCK_READ_SECTION(&rename_lock, lockless, seq, NULL) {
+		dentry = d;
+		b = *p;
+		while (!IS_ROOT(dentry)) {
+			const struct dentry *parent = dentry->d_parent;
 
-		prefetch(parent);
-		if (!prepend_name(&b, &dentry->d_name))
-			break;
-		dentry = parent;
-	}
-	if (!(seq & 1))
-		rcu_read_unlock();
-	if (need_seqretry(&rename_lock, seq)) {
-		seq = 1;
-		goto restart;
+			prefetch(parent);
+			if (!prepend_name(&b, &dentry->d_name))
+				break;
+			dentry = parent;
+		}
+		if (lockless)
+			rcu_read_unlock();
 	}
-	done_seqretry(&rename_lock, seq);
+
 	if (b.len == p->len)
 		prepend_char(&b, '/');
 	return extract_string(&b);
-- 
2.25.1.362.g51ebf55