fs/fscache/main.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* General filesystem local caching manager
   3  *
   4  * Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  */
   7
   8 #define FSCACHE_DEBUG_LEVEL CACHE
   9 #include <linux/module.h>
  10 #include <linux/init.h>
  11 #include <linux/sched.h>
  12 #include <linux/completion.h>
  13 #include <linux/slab.h>
  14 #include <linux/seq_file.h>
  15 #define CREATE_TRACE_POINTS
  16 #include "internal.h"
  17
  18 MODULE_DESCRIPTION("FS Cache Manager");
  19 MODULE_AUTHOR("Red Hat, Inc.");
  20 MODULE_LICENSE("GPL");
  21
  22 unsigned fscache_defer_lookup = 1;
  23 module_param_named(defer_lookup, fscache_defer_lookup, uint,
  24                    S_IWUSR | S_IRUGO);
  25 MODULE_PARM_DESC(fscache_defer_lookup,
  26                  "Defer cookie lookup to background thread");
  27
  28 unsigned fscache_defer_create = 1;
  29 module_param_named(defer_create, fscache_defer_create, uint,
  30                    S_IWUSR | S_IRUGO);
  31 MODULE_PARM_DESC(fscache_defer_create,
  32                  "Defer cookie creation to background thread");
  33
  34 unsigned fscache_debug;
  35 module_param_named(debug, fscache_debug, uint,
  36                    S_IWUSR | S_IRUGO);
  37 MODULE_PARM_DESC(fscache_debug,
  38                  "FS-Cache debugging mask");
  39
  40 struct kobject *fscache_root;
  41 struct workqueue_struct *fscache_object_wq;
  42 struct workqueue_struct *fscache_op_wq;
  43
  44 DEFINE_PER_CPU(wait_queue_head_t, fscache_object_cong_wait);
  45
  46 /* these values serve as lower bounds, will be adjusted in fscache_init() */
  47 static unsigned fscache_object_max_active = 4;
  48 static unsigned fscache_op_max_active = 2;
  49
  50 #ifdef CONFIG_SYSCTL
  51 static struct ctl_table_header *fscache_sysctl_header;
  52
  53 static int fscache_max_active_sysctl(struct ctl_table *table, int write,
  54                                      void *buffer, size_t *lenp, loff_t *ppos)
  55 {
  56         struct workqueue_struct **wqp = table->extra1;
  57         unsigned int *datap = table->data;
  58         int ret;
  59
  60         ret = proc_dointvec(table, write, buffer, lenp, ppos);
  61         if (ret == 0)
  62                 workqueue_set_max_active(*wqp, *datap);
  63         return ret;
  64 }
  65
  66 static struct ctl_table fscache_sysctls[] = {
  67         {
  68                 .procname       = "object_max_active",
  69                 .data           = &fscache_object_max_active,
  70                 .maxlen         = sizeof(unsigned),
  71                 .mode           = 0644,
  72                 .proc_handler   = fscache_max_active_sysctl,
  73                 .extra1         = &fscache_object_wq,
  74         },
  75         {
  76                 .procname       = "operation_max_active",
  77                 .data           = &fscache_op_max_active,
  78                 .maxlen         = sizeof(unsigned),
  79                 .mode           = 0644,
  80                 .proc_handler   = fscache_max_active_sysctl,
  81                 .extra1         = &fscache_op_wq,
  82         },
  83         {}
  84 };
  85
  86 static struct ctl_table fscache_sysctls_root[] = {
  87         {
  88                 .procname       = "fscache",
  89                 .mode           = 0555,
  90                 .child          = fscache_sysctls,
  91         },
  92         {}
  93 };
  94 #endif
  95
  96 /*
  97  * Mixing scores (in bits) for (7,20):
  98  * Input delta: 1-bit      2-bit
  99  * 1 round:     330.3     9201.6
 100  * 2 rounds:   1246.4    25475.4
 101  * 3 rounds:   1907.1    31295.1
 102  * 4 rounds:   2042.3    31718.6
 103  * Perfect:    2048      31744
 104  *            (32*64)   (32*31/2 * 64)
 105  */
 106 #define HASH_MIX(x, y, a)       \
 107         (       x ^= (a),       \
 108         y ^= x, x = rol32(x, 7),\
 109         x += y, y = rol32(y,20),\
 110         y *= 9                  )
 111
 112 static inline unsigned int fold_hash(unsigned long x, unsigned long y)
 113 {
 114         /* Use arch-optimized multiply if one exists */
 115         return __hash_32(y ^ __hash_32(x));
 116 }
 117
 118 /*
 119  * Generate a hash.  This is derived from full_name_hash(), but we want to be
 120  * sure it is arch independent and that it doesn't change as bits of the
 121  * computed hash value might appear on disk.  The caller also guarantees that
 122  * the hashed data will be a series of aligned 32-bit words.
 123  */
 124 unsigned int fscache_hash(unsigned int salt, unsigned int *data, unsigned int n)
 125 {
 126         unsigned int a, x = 0, y = salt;
 127
 128         for (; n; n--) {
 129                 a = *data++;
 130                 HASH_MIX(x, y, a);
 131         }
 132         return fold_hash(x, y);
 133 }
 134
 135 /*
 136  * initialise the fs caching module
 137  */
 138 static int __init fscache_init(void)
 139 {
 140         unsigned int nr_cpus = num_possible_cpus();
 141         unsigned int cpu;
 142         int ret;
 143
 144         fscache_object_max_active =
 145                 clamp_val(nr_cpus,
 146                           fscache_object_max_active, WQ_UNBOUND_MAX_ACTIVE);
 147
 148         ret = -ENOMEM;
 149         fscache_object_wq = alloc_workqueue("fscache_object", WQ_UNBOUND,
 150                                             fscache_object_max_active);
 151         if (!fscache_object_wq)
 152                 goto error_object_wq;
 153
 154         fscache_op_max_active =
 155                 clamp_val(fscache_object_max_active / 2,
 156                           fscache_op_max_active, WQ_UNBOUND_MAX_ACTIVE);
 157
 158         ret = -ENOMEM;
 159         fscache_op_wq = alloc_workqueue("fscache_operation", WQ_UNBOUND,
 160                                         fscache_op_max_active);
 161         if (!fscache_op_wq)
 162                 goto error_op_wq;
 163
 164         for_each_possible_cpu(cpu)
 165                 init_waitqueue_head(&per_cpu(fscache_object_cong_wait, cpu));
 166
 167         ret = fscache_proc_init();
 168         if (ret < 0)
 169                 goto error_proc;
 170
 171 #ifdef CONFIG_SYSCTL
 172         ret = -ENOMEM;
 173         fscache_sysctl_header = register_sysctl_table(fscache_sysctls_root);
 174         if (!fscache_sysctl_header)
 175                 goto error_sysctl;
 176 #endif
 177
 178         fscache_cookie_jar = kmem_cache_create("fscache_cookie_jar",
 179                                                sizeof(struct fscache_cookie),
 180                                                0, 0, NULL);
 181         if (!fscache_cookie_jar) {
 182                 pr_notice("Failed to allocate a cookie jar\n");
 183                 ret = -ENOMEM;
 184                 goto error_cookie_jar;
 185         }
 186
 187         fscache_root = kobject_create_and_add("fscache", kernel_kobj);
 188         if (!fscache_root)
 189                 goto error_kobj;
 190
 191         pr_notice("Loaded\n");
 192         return 0;
 193
 194 error_kobj:
 195         kmem_cache_destroy(fscache_cookie_jar);
 196 error_cookie_jar:
 197 #ifdef CONFIG_SYSCTL
 198         unregister_sysctl_table(fscache_sysctl_header);
 199 error_sysctl:
 200 #endif
 201         fscache_proc_cleanup();
 202 error_proc:
 203         destroy_workqueue(fscache_op_wq);
 204 error_op_wq:
 205         destroy_workqueue(fscache_object_wq);
 206 error_object_wq:
 207         return ret;
 208 }
 209
 210 fs_initcall(fscache_init);
 211
 212 /*
 213  * clean up on module removal
 214  */
 215 static void __exit fscache_exit(void)
 216 {
 217         _enter("");
 218
 219         kobject_put(fscache_root);
 220         kmem_cache_destroy(fscache_cookie_jar);
 221 #ifdef CONFIG_SYSCTL
 222         unregister_sysctl_table(fscache_sysctl_header);
 223 #endif
 224         fscache_proc_cleanup();
 225         destroy_workqueue(fscache_op_wq);
 226         destroy_workqueue(fscache_object_wq);
 227         pr_notice("Unloaded\n");
 228 }
 229
 230 module_exit(fscache_exit);