xref: /kernel/linux/linux-5.10/fs/cachefiles/proc.c (revision 8c2ecf20) 
1// SPDX-License-Identifier: GPL-2.0-or-later
2/* CacheFiles statistics
3 *
4 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 */
7
8#include <linux/module.h>
9#include <linux/proc_fs.h>
10#include <linux/seq_file.h>
11#include "internal.h"
12
13atomic_t cachefiles_lookup_histogram[HZ];
14atomic_t cachefiles_mkdir_histogram[HZ];
15atomic_t cachefiles_create_histogram[HZ];
16
17/*
18 * display the latency histogram
19 */
20static int cachefiles_histogram_show(struct seq_file *m, void *v)
21{
22	unsigned long index;
23	unsigned x, y, z, t;
24
25	switch ((unsigned long) v) {
26	case 1:
27		seq_puts(m, "JIFS  SECS  LOOKUPS   MKDIRS    CREATES\n");
28		return 0;
29	case 2:
30		seq_puts(m, "===== ===== ========= ========= =========\n");
31		return 0;
32	default:
33		index = (unsigned long) v - 3;
34		x = atomic_read(&cachefiles_lookup_histogram[index]);
35		y = atomic_read(&cachefiles_mkdir_histogram[index]);
36		z = atomic_read(&cachefiles_create_histogram[index]);
37		if (x == 0 && y == 0 && z == 0)
38			return 0;
39
40		t = (index * 1000) / HZ;
41
42		seq_printf(m, "%4lu  0.%03u %9u %9u %9u\n", index, t, x, y, z);
43		return 0;
44	}
45}
46
47/*
48 * set up the iterator to start reading from the first line
49 */
50static void *cachefiles_histogram_start(struct seq_file *m, loff_t *_pos)
51{
52	if ((unsigned long long)*_pos >= HZ + 2)
53		return NULL;
54	if (*_pos == 0)
55		*_pos = 1;
56	return (void *)(unsigned long) *_pos;
57}
58
59/*
60 * move to the next line
61 */
62static void *cachefiles_histogram_next(struct seq_file *m, void *v, loff_t *pos)
63{
64	(*pos)++;
65	return (unsigned long long)*pos > HZ + 2 ?
66		NULL : (void *)(unsigned long) *pos;
67}
68
69/*
70 * clean up after reading
71 */
72static void cachefiles_histogram_stop(struct seq_file *m, void *v)
73{
74}
75
76static const struct seq_operations cachefiles_histogram_ops = {
77	.start		= cachefiles_histogram_start,
78	.stop		= cachefiles_histogram_stop,
79	.next		= cachefiles_histogram_next,
80	.show		= cachefiles_histogram_show,
81};
82
83/*
84 * initialise the /proc/fs/cachefiles/ directory
85 */
86int __init cachefiles_proc_init(void)
87{
88	_enter("");
89
90	if (!proc_mkdir("fs/cachefiles", NULL))
91		goto error_dir;
92
93	if (!proc_create_seq("fs/cachefiles/histogram", S_IFREG | 0444, NULL,
94			 &cachefiles_histogram_ops))
95		goto error_histogram;
96
97	_leave(" = 0");
98	return 0;
99
100error_histogram:
101	remove_proc_entry("fs/cachefiles", NULL);
102error_dir:
103	_leave(" = -ENOMEM");
104	return -ENOMEM;
105}
106
107/*
108 * clean up the /proc/fs/cachefiles/ directory
109 */
110void cachefiles_proc_cleanup(void)
111{
112	remove_proc_entry("fs/cachefiles/histogram", NULL);
113	remove_proc_entry("fs/cachefiles", NULL);
114}
115