From: Al Viro <viro@zeniv.linux.org.uk>
Date: Tue, 25 Feb 2025 18:21:14 +0000 (-0500)
Subject: d_set_mounted(): we don't need to bump seqcount component of rename_lock
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5e317d23f6c6c4b59d84e228a2271228e81cc797;p=thirdparty%2Flinux.git

d_set_mounted(): we don't need to bump seqcount component of rename_lock

IOW, read_seqlock_excl() is sufficient there; no need to bother
with write_seqlock() (forcing all rename_lock readers into retry).

That leaves rename_lock taken for write only when we want to change
someone's parent or name.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---

diff --git a/fs/dcache.c b/fs/dcache.c
index 03d58b2d4fa34..3c3cfb345233e 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1436,7 +1436,7 @@ int d_set_mounted(struct dentry *dentry)
 {
 	struct dentry *p;
 	int ret = -ENOENT;
-	write_seqlock(&rename_lock);
+	read_seqlock_excl(&rename_lock);
 	for (p = dentry->d_parent; !IS_ROOT(p); p = p->d_parent) {
 		/* Need exclusion wrt. d_invalidate() */
 		spin_lock(&p->d_lock);
@@ -1456,7 +1456,7 @@ int d_set_mounted(struct dentry *dentry)
 	}
  	spin_unlock(&dentry->d_lock);
 out:
-	write_sequnlock(&rename_lock);
+	read_sequnlock_excl(&rename_lock);
 	return ret;
 }