v4.19.13 snapshot.
diff --git a/fs/cachefiles/proc.c b/fs/cachefiles/proc.c
new file mode 100644
index 0000000..0ce1aa5
--- /dev/null
+++ b/fs/cachefiles/proc.c
@@ -0,0 +1,118 @@
+/* CacheFiles statistics
+ *
+ * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#include <linux/module.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include "internal.h"
+
+atomic_t cachefiles_lookup_histogram[HZ];
+atomic_t cachefiles_mkdir_histogram[HZ];
+atomic_t cachefiles_create_histogram[HZ];
+
+/*
+ * display the latency histogram
+ */
+static int cachefiles_histogram_show(struct seq_file *m, void *v)
+{
+ unsigned long index;
+ unsigned x, y, z, t;
+
+ switch ((unsigned long) v) {
+ case 1:
+ seq_puts(m, "JIFS SECS LOOKUPS MKDIRS CREATES\n");
+ return 0;
+ case 2:
+ seq_puts(m, "===== ===== ========= ========= =========\n");
+ return 0;
+ default:
+ index = (unsigned long) v - 3;
+ x = atomic_read(&cachefiles_lookup_histogram[index]);
+ y = atomic_read(&cachefiles_mkdir_histogram[index]);
+ z = atomic_read(&cachefiles_create_histogram[index]);
+ if (x == 0 && y == 0 && z == 0)
+ return 0;
+
+ t = (index * 1000) / HZ;
+
+ seq_printf(m, "%4lu 0.%03u %9u %9u %9u\n", index, t, x, y, z);
+ return 0;
+ }
+}
+
+/*
+ * set up the iterator to start reading from the first line
+ */
+static void *cachefiles_histogram_start(struct seq_file *m, loff_t *_pos)
+{
+ if ((unsigned long long)*_pos >= HZ + 2)
+ return NULL;
+ if (*_pos == 0)
+ *_pos = 1;
+ return (void *)(unsigned long) *_pos;
+}
+
+/*
+ * move to the next line
+ */
+static void *cachefiles_histogram_next(struct seq_file *m, void *v, loff_t *pos)
+{
+ (*pos)++;
+ return (unsigned long long)*pos > HZ + 2 ?
+ NULL : (void *)(unsigned long) *pos;
+}
+
+/*
+ * clean up after reading
+ */
+static void cachefiles_histogram_stop(struct seq_file *m, void *v)
+{
+}
+
+static const struct seq_operations cachefiles_histogram_ops = {
+ .start = cachefiles_histogram_start,
+ .stop = cachefiles_histogram_stop,
+ .next = cachefiles_histogram_next,
+ .show = cachefiles_histogram_show,
+};
+
+/*
+ * initialise the /proc/fs/cachefiles/ directory
+ */
+int __init cachefiles_proc_init(void)
+{
+ _enter("");
+
+ if (!proc_mkdir("fs/cachefiles", NULL))
+ goto error_dir;
+
+ if (!proc_create_seq("fs/cachefiles/histogram", S_IFREG | 0444, NULL,
+ &cachefiles_histogram_ops))
+ goto error_histogram;
+
+ _leave(" = 0");
+ return 0;
+
+error_histogram:
+ remove_proc_entry("fs/cachefiles", NULL);
+error_dir:
+ _leave(" = -ENOMEM");
+ return -ENOMEM;
+}
+
+/*
+ * clean up the /proc/fs/cachefiles/ directory
+ */
+void cachefiles_proc_cleanup(void)
+{
+ remove_proc_entry("fs/cachefiles/histogram", NULL);
+ remove_proc_entry("fs/cachefiles", NULL);
+}