diff --git a/fs/dcache.c b/fs/dcache.c
index 8e166a4..c7cd9ee 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -118,7 +118,14 @@ struct dentry_stat_t dentry_stat = {
 };
 
 static DEFINE_PER_CPU(unsigned int, nr_dentry);
-static DEFINE_PER_CPU(unsigned int, nr_dentry_unused);
+/*
+ * The total counts for nr_dentry_unused are hotplug-safe, since we always loop
+ * through all possible cpus. It is quite possible, though, that the counters
+ * go negative.  That could easily happen for a dentry that is marked unused in
+ * one CPU but decrements that count after being preempted to another CPU.
+ * Therefore, we must use a signed quantity in here.
+ */
+static DEFINE_PER_CPU(long , nr_dentry_unused);
 
 #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
 static int get_nr_dentry(void)