On Tue, 2025-10-28 at 00:45 +0000, Al Viro wrote:
[...]

+void d_make_discardable(struct dentry *dentry)
+{
+	spin_lock(&dentry->d_lock);
+	dentry->d_flags &= ~DCACHE_PERSISTENT;
+	dentry->d_lockref.count--;
+	rcu_read_lock();
+	finish_dput(dentry);
+}
+EXPORT_SYMBOL(d_make_discardable);

I was going to ask why you don't have a WARN_ON if the dentry is not
persistent here.  Fortunately I read the next patch which gives the
explanation and saw that you do do this in patch 50.  For those of us
who have a very linear way of reading and responding to patches, it
would have been helpful to put a comment at the top saying something
like persistency will be checked when all callers are converted, which
you can replace in patch 50.

Regards,

James