linux-2.6-590-dcookies-mm.patch

   1 diff -Nurb linux-2.6.27-580/fs/dcookies.c linux-2.6.27-590/fs/dcookies.c
   2 --- linux-2.6.27-580/fs/dcookies.c      2009-07-23 10:51:40.000000000 -0400
   3 +++ linux-2.6.27-590/fs/dcookies.c      2009-11-30 17:26:58.000000000 -0500
   4 @@ -24,6 +24,7 @@
   5  #include <linux/errno.h>
   6  #include <linux/dcookies.h>
   7  #include <linux/mutex.h>
   8 +#include <linux/spinlock.h>
   9  #include <linux/path.h>
  10  #include <asm/uaccess.h>
  11
  12 @@ -38,15 +39,21 @@
  13
  14  static LIST_HEAD(dcookie_users);
  15  static DEFINE_MUTEX(dcookie_mutex);
  16 +spinlock_t dcookie_hash_write_lock = SPIN_LOCK_UNLOCKED;
  17  static struct kmem_cache *dcookie_cache __read_mostly;
  18 -static struct list_head *dcookie_hashtable __read_mostly;
  19 +static struct list_head *dcookie_hashtable[3] __read_mostly;
  20  static size_t hash_size __read_mostly;
  21 +unsigned int current_hash = 1, old_hash = 0;
  22
  23  static inline int is_live(void)
  24  {
  25         return !(list_empty(&dcookie_users));
  26  }
  27
  28 +static inline int is_shared(void)
  29 +{
  30 +       return !(list_empty(&dcookie_users)) && !(list_empty(dcookie_users.next));
  31 +}
  32
  33  /* The dentry is locked, its address will do for the cookie */
  34  static inline unsigned long dcookie_value(struct dcookie_struct * dcs)
  35 @@ -68,7 +75,18 @@
  36         struct list_head * pos;
  37         struct list_head * list;
  38
  39 -       list = dcookie_hashtable + dcookie_hash(dcookie);
  40 +       list = dcookie_hashtable[current_hash] + dcookie_hash(dcookie);
  41 +
  42 +       list_for_each(pos, list) {
  43 +               dcs = list_entry(pos, struct dcookie_struct, hash_list);
  44 +               if (dcookie_value(dcs) == dcookie) {
  45 +                       found = dcs;
  46 +                       break;
  47 +               }
  48 +       }
  49 +
  50 +    if (!found) {
  51 +        list = dcookie_hashtable[old_hash] + dcookie_hash(dcookie);
  52
  53         list_for_each(pos, list) {
  54                 dcs = list_entry(pos, struct dcookie_struct, hash_list);
  55 @@ -77,6 +95,8 @@
  56                         break;
  57                 }
  58         }
  59 +    }
  60 +
  61
  62         return found;
  63  }
  64 @@ -84,15 +104,14 @@
  65
  66  static void hash_dcookie(struct dcookie_struct * dcs)
  67  {
  68 -       struct list_head * list = dcookie_hashtable + dcookie_hash(dcookie_value(dcs));
  69 +       struct list_head * list = dcookie_hashtable[current_hash] + dcookie_hash(dcookie_value(dcs));
  70         list_add(&dcs->hash_list, list);
  71  }
  72
  73
  74  static struct dcookie_struct *alloc_dcookie(struct path *path)
  75  {
  76 -       struct dcookie_struct *dcs = kmem_cache_alloc(dcookie_cache,
  77 -                                                       GFP_KERNEL);
  78 +       struct dcookie_struct * dcs = kmem_cache_alloc(dcookie_cache, GFP_ATOMIC);
  79         if (!dcs)
  80                 return NULL;
  81
  82 @@ -112,7 +131,7 @@
  83         int err = 0;
  84         struct dcookie_struct * dcs;
  85
  86 -       mutex_lock(&dcookie_mutex);
  87 +       spin_lock(&dcookie_hash_write_lock);
  88
  89         if (!is_live()) {
  90                 err = -EINVAL;
  91 @@ -132,7 +151,7 @@
  92         *cookie = dcookie_value(dcs);
  93
  94  out:
  95 -       mutex_unlock(&dcookie_mutex);
  96 +       spin_unlock(&dcookie_hash_write_lock);
  97         return err;
  98  }
  99
 100 @@ -204,7 +223,7 @@
 101  static int dcookie_init(void)
 102  {
 103         struct list_head * d;
 104 -       unsigned int i, hash_bits;
 105 +       unsigned int i, j, hash_bits;
 106         int err = -ENOMEM;
 107
 108         dcookie_cache = kmem_cache_create("dcookie_cache",
 109 @@ -214,9 +233,11 @@
 110         if (!dcookie_cache)
 111                 goto out;
 112
 113 -       dcookie_hashtable = kmalloc(PAGE_SIZE, GFP_KERNEL);
 114 -       if (!dcookie_hashtable)
 115 +    for (i=0; i<3; i++) {
 116 +        dcookie_hashtable[i] = kmalloc(PAGE_SIZE, GFP_KERNEL);
 117 +        if (!dcookie_hashtable[i])
 118                 goto out_kmem;
 119 +    }
 120
 121         err = 0;
 122
 123 @@ -239,13 +260,16 @@
 124         hash_size = 1UL << hash_bits;
 125
 126         /* And initialize the newly allocated array */
 127 -       d = dcookie_hashtable;
 128 -       i = hash_size;
 129 +
 130 +    for (i=0; i<3; i++) {
 131 +        d = dcookie_hashtable[i];
 132 +        j = hash_size;
 133         do {
 134                 INIT_LIST_HEAD(d);
 135                 d++;
 136 -               i--;
 137 -       } while (i);
 138 +            j--;
 139 +        } while (j);
 140 +    }
 141
 142  out:
 143         return err;
 144 @@ -262,25 +286,61 @@
 145         kmem_cache_free(dcookie_cache, dcs);
 146  }
 147
 148 +int dcookie_swap(void) {
 149 +    if (is_shared())
 150 +        return -EAGAIN;
 151
 152 -static void dcookie_exit(void)
 153 -{
 154 +    old_hash=current_hash;
 155 +    current_hash = (current_hash + 1) % 3;
 156 +    return 0;
 157 +}
 158 +
 159 +/* Switch to the second hash */
 160 +int dcookie_garbage_collect(void) {
 161         struct list_head * list;
 162         struct list_head * pos;
 163         struct list_head * pos2;
 164         struct dcookie_struct * dcs;
 165         size_t i;
 166 +    int next_hash=(current_hash + 1) % 3;
 167 +
 168 +    if (is_shared())
 169 +        return -EAGAIN;
 170
 171 +    /* XXX consider the consequence of dcookie allocation concurring with this cleanup */
 172         for (i = 0; i < hash_size; ++i) {
 173 -               list = dcookie_hashtable + i;
 174 +               list = dcookie_hashtable[next_hash] + i;
 175 +               list_for_each_safe(pos, pos2, list) {
 176 +                       dcs = list_entry(pos, struct dcookie_struct, hash_list);
 177 +                       list_del(&dcs->hash_list);
 178 +                       free_dcookie(dcs);
 179 +               }
 180 +       }
 181 +
 182 +    return 0;
 183 +}
 184 +
 185 +static void dcookie_exit(void)
 186 +{
 187 +       struct list_head * list;
 188 +       struct list_head * pos;
 189 +       struct list_head * pos2;
 190 +       struct dcookie_struct * dcs;
 191 +       size_t j;
 192 +    unsigned int i;
 193 +
 194 +    for (i = 0; i < 3; ++i) {
 195 +        for (j = 0; j < hash_size; ++j) {
 196 +            list = dcookie_hashtable[i] + j;
 197                 list_for_each_safe(pos, pos2, list) {
 198                         dcs = list_entry(pos, struct dcookie_struct, hash_list);
 199                         list_del(&dcs->hash_list);
 200                         free_dcookie(dcs);
 201                 }
 202         }
 203 +           kfree(dcookie_hashtable[i]);
 204 +    }
 205
 206 -       kfree(dcookie_hashtable);
 207         kmem_cache_destroy(dcookie_cache);
 208  }
 209
 210 @@ -330,3 +390,5 @@
 211  EXPORT_SYMBOL_GPL(dcookie_register);
 212  EXPORT_SYMBOL_GPL(dcookie_unregister);
 213  EXPORT_SYMBOL_GPL(get_dcookie);
 214 +EXPORT_SYMBOL_GPL(dcookie_garbage_collect);
 215 +EXPORT_SYMBOL_GPL(dcookie_swap);
 216 diff -Nurb linux-2.6.27-580/include/linux/dcookies.h linux-2.6.27-590/include/linux/dcookies.h
 217 --- linux-2.6.27-580/include/linux/dcookies.h   2008-10-09 18:13:53.000000000 -0400
 218 +++ linux-2.6.27-590/include/linux/dcookies.h   2009-11-30 16:42:59.000000000 -0500
 219 @@ -46,6 +46,27 @@
 220   */
 221  int get_dcookie(struct path *path, unsigned long *cookie);
 222
 223 +/**
 224 + * dcookie_swap - switch to the next dcookie epoch
 225 + *
 226 + * Deactivate the current dcookie hash table and activate
 227 + * the next one
 228 + *
 229 + * Returns 0 on success
 230 + */
 231 +
 232 +int dcookie_swap(void);
 233 +
 234 +/**
 235 + * dcookie_garbage_collect - clear the hash table next in line
 236 + *
 237 + * Clear the hash table to be activated in the next epoch.
 238 + *
 239 + * Returns 0 on success
 240 + */
 241 +
 242 +int dcookie_garbage_collect(void);
 243 +
 244  #else
 245
 246  static inline struct dcookie_user * dcookie_register(void)