fs/cachefiles/proc.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* CacheFiles statistics
   3  *
   4  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  */
   7
   8 #include <linux/module.h>
   9 #include <linux/proc_fs.h>
  10 #include <linux/seq_file.h>
  11 #include "internal.h"
  12
  13 atomic_t cachefiles_lookup_histogram[HZ];
  14 atomic_t cachefiles_mkdir_histogram[HZ];
  15 atomic_t cachefiles_create_histogram[HZ];
  16
  17 /*
  18  * display the latency histogram
  19  */
  20 static int cachefiles_histogram_show(struct seq_file *m, void *v)
  21 {
  22         unsigned long index;
  23         unsigned x, y, z, t;
  24
  25         switch ((unsigned long) v) {
  26         case 1:
  27                 seq_puts(m, "JIFS  SECS  LOOKUPS   MKDIRS    CREATES\n");
  28                 return 0;
  29         case 2:
  30                 seq_puts(m, "===== ===== ========= ========= =========\n");
  31                 return 0;
  32         default:
  33                 index = (unsigned long) v - 3;
  34                 x = atomic_read(&cachefiles_lookup_histogram[index]);
  35                 y = atomic_read(&cachefiles_mkdir_histogram[index]);
  36                 z = atomic_read(&cachefiles_create_histogram[index]);
  37                 if (x == 0 && y == 0 && z == 0)
  38                         return 0;
  39
  40                 t = (index * 1000) / HZ;
  41
  42                 seq_printf(m, "%4lu  0.%03u %9u %9u %9u\n", index, t, x, y, z);
  43                 return 0;
  44         }
  45 }
  46
  47 /*
  48  * set up the iterator to start reading from the first line
  49  */
  50 static void *cachefiles_histogram_start(struct seq_file *m, loff_t *_pos)
  51 {
  52         if ((unsigned long long)*_pos >= HZ + 2)
  53                 return NULL;
  54         if (*_pos == 0)
  55                 *_pos = 1;
  56         return (void *)(unsigned long) *_pos;
  57 }
  58
  59 /*
  60  * move to the next line
  61  */
  62 static void *cachefiles_histogram_next(struct seq_file *m, void *v, loff_t *pos)
  63 {
  64         (*pos)++;
  65         return (unsigned long long)*pos > HZ + 2 ?
  66                 NULL : (void *)(unsigned long) *pos;
  67 }
  68
  69 /*
  70  * clean up after reading
  71  */
  72 static void cachefiles_histogram_stop(struct seq_file *m, void *v)
  73 {
  74 }
  75
  76 static const struct seq_operations cachefiles_histogram_ops = {
  77         .start          = cachefiles_histogram_start,
  78         .stop           = cachefiles_histogram_stop,
  79         .next           = cachefiles_histogram_next,
  80         .show           = cachefiles_histogram_show,
  81 };
  82
  83 /*
  84  * initialise the /proc/fs/cachefiles/ directory
  85  */
  86 int __init cachefiles_proc_init(void)
  87 {
  88         _enter("");
  89
  90         if (!proc_mkdir("fs/cachefiles", NULL))
  91                 goto error_dir;
  92
  93         if (!proc_create_seq("fs/cachefiles/histogram", S_IFREG | 0444, NULL,
  94                          &cachefiles_histogram_ops))
  95                 goto error_histogram;
  96
  97         _leave(" = 0");
  98         return 0;
  99
 100 error_histogram:
 101         remove_proc_entry("fs/cachefiles", NULL);
 102 error_dir:
 103         _leave(" = -ENOMEM");
 104         return -ENOMEM;
 105 }
 106
 107 /*
 108  * clean up the /proc/fs/cachefiles/ directory
 109  */
 110 void cachefiles_proc_cleanup(void)
 111 {
 112         remove_proc_entry("fs/cachefiles/histogram", NULL);
 113         remove_proc_entry("fs/cachefiles", NULL);
 114 }