proc.c

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/* CacheFiles statistics
 *
 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells ([email protected])
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */

#include <linux/module.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include "internal.h"

atomic_t cachefiles_lookup_histogram[HZ];
atomic_t cachefiles_mkdir_histogram[HZ];
atomic_t cachefiles_create_histogram[HZ];

/*
 * display the latency histogram
 */
static int cachefiles_histogram_show(struct seq_file *m, void *v)
{
    unsigned long index;
    unsigned x, y, z, t;

    switch ((unsigned long) v) {
    case 1:
        seq_puts(m, "JIFS  SECS  LOOKUPS   MKDIRS    CREATES\n");
        return 0;
    case 2:
        seq_puts(m, "===== ===== ========= ========= =========\n");
        return 0;
    default:
        index = (unsigned long) v - 3;
        x = atomic_read(&cachefiles_lookup_histogram[index]);
        y = atomic_read(&cachefiles_mkdir_histogram[index]);
        z = atomic_read(&cachefiles_create_histogram[index]);
        if (x == 0 && y == 0 && z == 0)
            return 0;

        t = (index * 1000) / HZ;

        seq_printf(m, "%4lu  0.%03u %9u %9u %9u\n", index, t, x, y, z);
        return 0;
    }
}

/*
 * set up the iterator to start reading from the first line
 */
static void *cachefiles_histogram_start(struct seq_file *m, loff_t *_pos)
{
    if ((unsigned long long)*_pos >= HZ + 2)
        return NULL;
    if (*_pos == 0)
        *_pos = 1;
    return (void *)(unsigned long) *_pos;
}

/*
 * move to the next line
 */
static void *cachefiles_histogram_next(struct seq_file *m, void *v, loff_t *pos)
{
    (*pos)++;
    return (unsigned long long)*pos > HZ + 2 ?
        NULL : (void *)(unsigned long) *pos;
}

/*
 * clean up after reading
 */
static void cachefiles_histogram_stop(struct seq_file *m, void *v)
{
}

static const struct seq_operations cachefiles_histogram_ops = {
    .start      = cachefiles_histogram_start,
    .stop       = cachefiles_histogram_stop,
    .next       = cachefiles_histogram_next,
    .show       = cachefiles_histogram_show,
};

/*
 * open "/proc/fs/cachefiles/XXX" which provide statistics summaries
 */
static int cachefiles_histogram_open(struct inode *inode, struct file *file)
{
    return seq_open(file, &cachefiles_histogram_ops);
}

static const struct file_operations cachefiles_histogram_fops = {
    .owner      = THIS_MODULE,
    .open       = cachefiles_histogram_open,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = seq_release,
};

/*
 * initialise the /proc/fs/cachefiles/ directory
 */
int __init cachefiles_proc_init(void)
{
    _enter("");

    if (!proc_mkdir("fs/cachefiles", NULL))
        goto error_dir;

    if (!proc_create("fs/cachefiles/histogram", S_IFREG | 0444, NULL,
             &cachefiles_histogram_fops))
        goto error_histogram;

    _leave(" = 0");
    return 0;

error_histogram:
    remove_proc_entry("fs/cachefiles", NULL);
error_dir:
    _leave(" = -ENOMEM");
    return -ENOMEM;
}

/*
 * clean up the /proc/fs/cachefiles/ directory
 */
void cachefiles_proc_cleanup(void)
{
    remove_proc_entry("fs/cachefiles/histogram", NULL);
    remove_proc_entry("fs/cachefiles", NULL);
}