CacheFiles: A cache that backs onto a mounted filesystem
[linux-2.6.git] / fs / cachefiles / proc.c
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  */
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  */
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  */
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  */
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  */
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  */
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  */
130 void cachefiles_proc_cleanup(void)
131 {
132         remove_proc_entry("fs/cachefiles/histogram", NULL);
133         remove_proc_entry("fs/cachefiles", NULL);
134 }