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 }