Merging upstream version 6.9.11.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 14 insertions, 17 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index 66515fbc9d..4c144519aa 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -3035,28 +3035,25 @@ EXPORT_SYMBOL(d_splice_alias);
   
 bool is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
 {
-	bool result;
+	bool subdir;
 	unsigned seq;
 
 	if (new_dentry == old_dentry)
 		return true;
 
-	do {
-		/* for restarting inner loop in case of seq retry */
-		seq = read_seqbegin(&rename_lock);
-		/*
-		 * Need rcu_readlock to protect against the d_parent trashing
-		 * due to d_move
-		 */
-		rcu_read_lock();
-		if (d_ancestor(old_dentry, new_dentry))
-			result = true;
-		else
-			result = false;
-		rcu_read_unlock();
-	} while (read_seqretry(&rename_lock, seq));
-
-	return result;
+	/* Access d_parent under rcu as d_move() may change it. */
+	rcu_read_lock();
+	seq = read_seqbegin(&rename_lock);
+	subdir = d_ancestor(old_dentry, new_dentry);
+	 /* Try lockless once... */
+	if (read_seqretry(&rename_lock, seq)) {
+		/* ...else acquire lock for progress even on deep chains. */
+		read_seqlock_excl(&rename_lock);
+		subdir = d_ancestor(old_dentry, new_dentry);
+		read_sequnlock_excl(&rename_lock);
+	}
+	rcu_read_unlock();
+	return subdir;
 }
 EXPORT_SYMBOL(is_subdir);