fs/fscache/main.c

   1 /* General filesystem local caching manager
   2  *
   3  * Copyright (C) 2004-2007 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 License
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the License, or (at your option) any later version.
  10  */
  11
  12 #define FSCACHE_DEBUG_LEVEL CACHE
  13 #include <linux/module.h>
  14 #include <linux/init.h>
  15 #include <linux/sched.h>
  16 #include <linux/completion.h>
  17 #include <linux/slab.h>
  18 #include <linux/seq_file.h>
  19 #define CREATE_TRACE_POINTS
  20 #include "internal.h"
  21
  22 MODULE_DESCRIPTION("FS Cache Manager");
  23 MODULE_AUTHOR("Red Hat, Inc.");
  24 MODULE_LICENSE("GPL");
  25
  26 unsigned fscache_defer_lookup = 1;
  27 module_param_named(defer_lookup, fscache_defer_lookup, uint,
  28                    S_IWUSR | S_IRUGO);
  29 MODULE_PARM_DESC(fscache_defer_lookup,
  30                  "Defer cookie lookup to background thread");
  31
  32 unsigned fscache_defer_create = 1;
  33 module_param_named(defer_create, fscache_defer_create, uint,
  34                    S_IWUSR | S_IRUGO);
  35 MODULE_PARM_DESC(fscache_defer_create,
  36                  "Defer cookie creation to background thread");
  37
  38 unsigned fscache_debug;
  39 module_param_named(debug, fscache_debug, uint,
  40                    S_IWUSR | S_IRUGO);
  41 MODULE_PARM_DESC(fscache_debug,
  42                  "FS-Cache debugging mask");
  43
  44 struct kobject *fscache_root;
  45 struct workqueue_struct *fscache_object_wq;
  46 struct workqueue_struct *fscache_op_wq;
  47
  48 DEFINE_PER_CPU(wait_queue_head_t, fscache_object_cong_wait);
  49
  50 /* these values serve as lower bounds, will be adjusted in fscache_init() */
  51 static unsigned fscache_object_max_active = 4;
  52 static unsigned fscache_op_max_active = 2;
  53
  54 #ifdef CONFIG_SYSCTL
  55 static struct ctl_table_header *fscache_sysctl_header;
  56
  57 static int fscache_max_active_sysctl(struct ctl_table *table, int write,
  58                                      void __user *buffer,
  59                                      size_t *lenp, loff_t *ppos)
  60 {
  61         struct workqueue_struct **wqp = table->extra1;
  62         unsigned int *datap = table->data;
  63         int ret;
  64
  65         ret = proc_dointvec(table, write, buffer, lenp, ppos);
  66         if (ret == 0)
  67                 workqueue_set_max_active(*wqp, *datap);
  68         return ret;
  69 }
  70
  71 static struct ctl_table fscache_sysctls[] = {
  72         {
  73                 .procname       = "object_max_active",
  74                 .data           = &fscache_object_max_active,
  75                 .maxlen         = sizeof(unsigned),
  76                 .mode           = 0644,
  77                 .proc_handler   = fscache_max_active_sysctl,
  78                 .extra1         = &fscache_object_wq,
  79         },
  80         {
  81                 .procname       = "operation_max_active",
  82                 .data           = &fscache_op_max_active,
  83                 .maxlen         = sizeof(unsigned),
  84                 .mode           = 0644,
  85                 .proc_handler   = fscache_max_active_sysctl,
  86                 .extra1         = &fscache_op_wq,
  87         },
  88         {}
  89 };
  90
  91 static struct ctl_table fscache_sysctls_root[] = {
  92         {
  93                 .procname       = "fscache",
  94                 .mode           = 0555,
  95                 .child          = fscache_sysctls,
  96         },
  97         {}
  98 };
  99 #endif
 100
 101 /*
 102  * Mixing scores (in bits) for (7,20):
 103  * Input delta: 1-bit      2-bit
 104  * 1 round:     330.3     9201.6
 105  * 2 rounds:   1246.4    25475.4
 106  * 3 rounds:   1907.1    31295.1
 107  * 4 rounds:   2042.3    31718.6
 108  * Perfect:    2048      31744
 109  *            (32*64)   (32*31/2 * 64)
 110  */
 111 #define HASH_MIX(x, y, a)       \
 112         (       x ^= (a),       \
 113         y ^= x, x = rol32(x, 7),\
 114         x += y, y = rol32(y,20),\
 115         y *= 9                  )
 116
 117 static inline unsigned int fold_hash(unsigned long x, unsigned long y)
 118 {
 119         /* Use arch-optimized multiply if one exists */
 120         return __hash_32(y ^ __hash_32(x));
 121 }
 122
 123 /*
 124  * Generate a hash.  This is derived from full_name_hash(), but we want to be
 125  * sure it is arch independent and that it doesn't change as bits of the
 126  * computed hash value might appear on disk.  The caller also guarantees that
 127  * the hashed data will be a series of aligned 32-bit words.
 128  */
 129 unsigned int fscache_hash(unsigned int salt, unsigned int *data, unsigned int n)
 130 {
 131         unsigned int a, x = 0, y = salt;
 132
 133         for (; n; n--) {
 134                 a = *data++;
 135                 HASH_MIX(x, y, a);
 136         }
 137         return fold_hash(x, y);
 138 }
 139
 140 /*
 141  * initialise the fs caching module
 142  */
 143 static int __init fscache_init(void)
 144 {
 145         unsigned int nr_cpus = num_possible_cpus();
 146         unsigned int cpu;
 147         int ret;
 148
 149         fscache_object_max_active =
 150                 clamp_val(nr_cpus,
 151                           fscache_object_max_active, WQ_UNBOUND_MAX_ACTIVE);
 152
 153         ret = -ENOMEM;
 154         fscache_object_wq = alloc_workqueue("fscache_object", WQ_UNBOUND,
 155                                             fscache_object_max_active);
 156         if (!fscache_object_wq)
 157                 goto error_object_wq;
 158
 159         fscache_op_max_active =
 160                 clamp_val(fscache_object_max_active / 2,
 161                           fscache_op_max_active, WQ_UNBOUND_MAX_ACTIVE);
 162
 163         ret = -ENOMEM;
 164         fscache_op_wq = alloc_workqueue("fscache_operation", WQ_UNBOUND,
 165                                         fscache_op_max_active);
 166         if (!fscache_op_wq)
 167                 goto error_op_wq;
 168
 169         for_each_possible_cpu(cpu)
 170                 init_waitqueue_head(&per_cpu(fscache_object_cong_wait, cpu));
 171
 172         ret = fscache_proc_init();
 173         if (ret < 0)
 174                 goto error_proc;
 175
 176 #ifdef CONFIG_SYSCTL
 177         ret = -ENOMEM;
 178         fscache_sysctl_header = register_sysctl_table(fscache_sysctls_root);
 179         if (!fscache_sysctl_header)
 180                 goto error_sysctl;
 181 #endif
 182
 183         fscache_cookie_jar = kmem_cache_create("fscache_cookie_jar",
 184                                                sizeof(struct fscache_cookie),
 185                                                0, 0, NULL);
 186         if (!fscache_cookie_jar) {
 187                 pr_notice("Failed to allocate a cookie jar\n");
 188                 ret = -ENOMEM;
 189                 goto error_cookie_jar;
 190         }
 191
 192         fscache_root = kobject_create_and_add("fscache", kernel_kobj);
 193         if (!fscache_root)
 194                 goto error_kobj;
 195
 196         pr_notice("Loaded\n");
 197         return 0;
 198
 199 error_kobj:
 200         kmem_cache_destroy(fscache_cookie_jar);
 201 error_cookie_jar:
 202 #ifdef CONFIG_SYSCTL
 203         unregister_sysctl_table(fscache_sysctl_header);
 204 error_sysctl:
 205 #endif
 206         fscache_proc_cleanup();
 207 error_proc:
 208         destroy_workqueue(fscache_op_wq);
 209 error_op_wq:
 210         destroy_workqueue(fscache_object_wq);
 211 error_object_wq:
 212         return ret;
 213 }
 214
 215 fs_initcall(fscache_init);
 216
 217 /*
 218  * clean up on module removal
 219  */
 220 static void __exit fscache_exit(void)
 221 {
 222         _enter("");
 223
 224         kobject_put(fscache_root);
 225         kmem_cache_destroy(fscache_cookie_jar);
 226 #ifdef CONFIG_SYSCTL
 227         unregister_sysctl_table(fscache_sysctl_header);
 228 #endif
 229         fscache_proc_cleanup();
 230         destroy_workqueue(fscache_op_wq);
 231         destroy_workqueue(fscache_object_wq);
 232         pr_notice("Unloaded\n");
 233 }
 234
 235 module_exit(fscache_exit);