linux/fs/cachefiles/proc.c
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   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
  17atomic_t cachefiles_lookup_histogram[HZ];
  18atomic_t cachefiles_mkdir_histogram[HZ];
  19atomic_t cachefiles_create_histogram[HZ];
  20
  21/*
  22 * display the latency histogram
  23 */
  24static 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 */
  54static 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 */
  66static 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 */
  76static void cachefiles_histogram_stop(struct seq_file *m, void *v)
  77{
  78}
  79
  80static 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 */
  90static int cachefiles_histogram_open(struct inode *inode, struct file *file)
  91{
  92        return seq_open(file, &cachefiles_histogram_ops);
  93}
  94
  95static 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 */
 106int __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
 120error_histogram:
 121        remove_proc_entry("fs/cachefiles", NULL);
 122error_dir:
 123        _leave(" = -ENOMEM");
 124        return -ENOMEM;
 125}
 126
 127/*
 128 * clean up the /proc/fs/cachefiles/ directory
 129 */
 130void cachefiles_proc_cleanup(void)
 131{
 132        remove_proc_entry("fs/cachefiles/histogram", NULL);
 133        remove_proc_entry("fs/cachefiles", NULL);
 134}
 135
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