1 /* CacheFiles statistics
2  *
3  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
4  * Written by David Howells (dhowells@redhat.com)
5  *
6  * This program is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU General Public Licence
8  * as published by the Free Software Foundation; either version
9  * 2 of the Licence, or (at your option) any later version.
10  */
11 
12 #include <linux/module.h>
13 #include <linux/proc_fs.h>
14 #include <linux/seq_file.h>
15 #include "internal.h"
16 
17 atomic_t cachefiles_lookup_histogram[HZ];
18 atomic_t cachefiles_mkdir_histogram[HZ];
19 atomic_t cachefiles_create_histogram[HZ];
20 
21 /*
22  * display the latency histogram
23  */
cachefiles_histogram_show(struct seq_file * m,void * v)24 static int cachefiles_histogram_show(struct seq_file *m, void *v)
25 {
26 	unsigned long index;
27 	unsigned x, y, z, t;
28 
29 	switch ((unsigned long) v) {
30 	case 1:
31 		seq_puts(m, "JIFS  SECS  LOOKUPS   MKDIRS    CREATES\n");
32 		return 0;
33 	case 2:
34 		seq_puts(m, "===== ===== ========= ========= =========\n");
35 		return 0;
36 	default:
37 		index = (unsigned long) v - 3;
38 		x = atomic_read(&cachefiles_lookup_histogram[index]);
39 		y = atomic_read(&cachefiles_mkdir_histogram[index]);
40 		z = atomic_read(&cachefiles_create_histogram[index]);
41 		if (x == 0 && y == 0 && z == 0)
42 			return 0;
43 
44 		t = (index * 1000) / HZ;
45 
46 		seq_printf(m, "%4lu  0.%03u %9u %9u %9u\n", index, t, x, y, z);
47 		return 0;
48 	}
49 }
50 
51 /*
52  * set up the iterator to start reading from the first line
53  */
cachefiles_histogram_start(struct seq_file * m,loff_t * _pos)54 static void *cachefiles_histogram_start(struct seq_file *m, loff_t *_pos)
55 {
56 	if ((unsigned long long)*_pos >= HZ + 2)
57 		return NULL;
58 	if (*_pos == 0)
59 		*_pos = 1;
60 	return (void *)(unsigned long) *_pos;
61 }
62 
63 /*
64  * move to the next line
65  */
cachefiles_histogram_next(struct seq_file * m,void * v,loff_t * pos)66 static void *cachefiles_histogram_next(struct seq_file *m, void *v, loff_t *pos)
67 {
68 	(*pos)++;
69 	return (unsigned long long)*pos > HZ + 2 ?
70 		NULL : (void *)(unsigned long) *pos;
71 }
72 
73 /*
74  * clean up after reading
75  */
cachefiles_histogram_stop(struct seq_file * m,void * v)76 static void cachefiles_histogram_stop(struct seq_file *m, void *v)
77 {
78 }
79 
80 static const struct seq_operations cachefiles_histogram_ops = {
81 	.start		= cachefiles_histogram_start,
82 	.stop		= cachefiles_histogram_stop,
83 	.next		= cachefiles_histogram_next,
84 	.show		= cachefiles_histogram_show,
85 };
86 
87 /*
88  * open "/proc/fs/cachefiles/XXX" which provide statistics summaries
89  */
cachefiles_histogram_open(struct inode * inode,struct file * file)90 static int cachefiles_histogram_open(struct inode *inode, struct file *file)
91 {
92 	return seq_open(file, &cachefiles_histogram_ops);
93 }
94 
95 static const struct file_operations cachefiles_histogram_fops = {
96 	.owner		= THIS_MODULE,
97 	.open		= cachefiles_histogram_open,
98 	.read		= seq_read,
99 	.llseek		= seq_lseek,
100 	.release	= seq_release,
101 };
102 
103 /*
104  * initialise the /proc/fs/cachefiles/ directory
105  */
cachefiles_proc_init(void)106 int __init cachefiles_proc_init(void)
107 {
108 	_enter("");
109 
110 	if (!proc_mkdir("fs/cachefiles", NULL))
111 		goto error_dir;
112 
113 	if (!proc_create("fs/cachefiles/histogram", S_IFREG | 0444, NULL,
114 			 &cachefiles_histogram_fops))
115 		goto error_histogram;
116 
117 	_leave(" = 0");
118 	return 0;
119 
120 error_histogram:
121 	remove_proc_entry("fs/cachefiles", NULL);
122 error_dir:
123 	_leave(" = -ENOMEM");
124 	return -ENOMEM;
125 }
126 
127 /*
128  * clean up the /proc/fs/cachefiles/ directory
129  */
cachefiles_proc_cleanup(void)130 void cachefiles_proc_cleanup(void)
131 {
132 	remove_proc_entry("fs/cachefiles/histogram", NULL);
133 	remove_proc_entry("fs/cachefiles", NULL);
134 }
135