sys/vfs/hammer/hammer_cursor.c

   1 /*
   2  * Copyright (c) 2007 The DragonFly Project.  All rights reserved.
   3  *
   4  * This code is derived from software contributed to The DragonFly Project
   5  * by Matthew Dillon <dillon@backplane.com>
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  *
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in
  15  *    the documentation and/or other materials provided with the
  16  *    distribution.
  17  * 3. Neither the name of The DragonFly Project nor the names of its
  18  *    contributors may be used to endorse or promote products derived
  19  *    from this software without specific, prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  22  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  23  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  24  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
  25  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  26  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
  27  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  28  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
  29  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  30  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  31  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  32  * SUCH DAMAGE.
  33  *
  34  * $DragonFly: src/sys/vfs/hammer/hammer_cursor.c,v 1.17 2008/02/08 08:30:59 dillon Exp $
  35  */
  36
  37 /*
  38  * HAMMER B-Tree index - cursor support routines
  39  */
  40 #include "hammer.h"
  41
  42 static int hammer_load_cursor_parent(hammer_cursor_t cursor);
  43
  44 /*
  45  * Initialize a fresh cursor using the B-Tree node cache.  If the cache
  46  * is not available initialize a fresh cursor at the root of the filesystem.
  47  */
  48 int
  49 hammer_init_cursor_hmp(hammer_cursor_t cursor, struct hammer_node **cache,
  50                        hammer_mount_t hmp)
  51 {
  52         hammer_volume_t volume;
  53         hammer_node_t node;
  54         int error;
  55
  56         bzero(cursor, sizeof(*cursor));
  57
  58         /*
  59          * Step 1 - acquire a locked node from the cache if possible
  60          */
  61         if (cache && *cache) {
  62                 node = hammer_ref_node_safe(hmp, cache, &error);
  63                 if (error == 0) {
  64                         hammer_lock_sh(&node->lock);
  65                         if (node->flags & HAMMER_NODE_DELETED) {
  66                                 hammer_unlock(&node->lock);
  67                                 hammer_rel_node(node);
  68                                 node = NULL;
  69                         }
  70                 }
  71         } else {
  72                 node = NULL;
  73         }
  74
  75         /*
  76          * Step 2 - If we couldn't get a node from the cache, get
  77          * the one from the root of the filesystem.
  78          */
  79         while (node == NULL) {
  80                 volume = hammer_get_root_volume(hmp, &error);
  81                 if (error)
  82                         break;
  83                 node = hammer_get_node(hmp, volume->ondisk->vol0_btree_root,
  84                                        &error);
  85                 hammer_rel_volume(volume, 0);
  86                 if (error)
  87                         break;
  88                 hammer_lock_sh(&node->lock);
  89                 if (node->flags & HAMMER_NODE_DELETED) {
  90                         hammer_unlock(&node->lock);
  91                         hammer_rel_node(node);
  92                         node = NULL;
  93                 }
  94         }
  95
  96         /*
  97          * Step 3 - finish initializing the cursor by acquiring the parent
  98          */
  99         cursor->node = node;
 100         if (error == 0)
 101                 error = hammer_load_cursor_parent(cursor);
 102         KKASSERT(error == 0);
 103         return(error);
 104 }
 105
 106 /*
 107  * We are finished with a cursor.  We NULL out various fields as sanity
 108  * check, in case the structure is inappropriately used afterwords.
 109  */
 110 void
 111 hammer_done_cursor(hammer_cursor_t cursor)
 112 {
 113         if (cursor->parent) {
 114                 hammer_unlock(&cursor->parent->lock);
 115                 hammer_rel_node(cursor->parent);
 116                 cursor->parent = NULL;
 117         }
 118         if (cursor->node) {
 119                 hammer_unlock(&cursor->node->lock);
 120                 hammer_rel_node(cursor->node);
 121                 cursor->node = NULL;
 122         }
 123         if (cursor->data_buffer) {
 124                 hammer_rel_buffer(cursor->data_buffer, 0);
 125                 cursor->data_buffer = NULL;
 126         }
 127         if (cursor->record_buffer) {
 128                 hammer_rel_buffer(cursor->record_buffer, 0);
 129                 cursor->record_buffer = NULL;
 130         }
 131         if (cursor->ip)
 132                 hammer_mem_done(cursor);
 133
 134         /*
 135          * If we deadlocked this node will be referenced.  Do a quick
 136          * lock/unlock to wait for the deadlock condition to clear.
 137          */
 138         if (cursor->deadlk_node) {
 139                 hammer_lock_ex(&cursor->deadlk_node->lock);
 140                 hammer_unlock(&cursor->deadlk_node->lock);
 141                 hammer_rel_node(cursor->deadlk_node);
 142                 cursor->deadlk_node = NULL;
 143         }
 144
 145         cursor->data1 = NULL;
 146         cursor->data2 = NULL;
 147         cursor->data_split = 0;
 148         cursor->record = NULL;
 149         cursor->left_bound = NULL;
 150         cursor->right_bound = NULL;
 151 }
 152
 153 /*
 154  * Upgrade cursor->node and cursor->parent to exclusive locks.  This
 155  * function can return EDEADLK.
 156  *
 157  * If we fail to upgrade the lock and cursor->deadlk_node is NULL,
 158  * we add another reference to the node that failed and set
 159  * cursor->deadlk_node so hammer_done_cursor() can block on it.
 160  */
 161 int
 162 hammer_cursor_upgrade(hammer_cursor_t cursor)
 163 {
 164         int error;
 165
 166         if (hammer_lock_held(&cursor->node->lock) < 0) {
 167                 error = hammer_lock_upgrade(&cursor->node->lock);
 168                 if (error && cursor->deadlk_node == NULL) {
 169                         cursor->deadlk_node = cursor->node;
 170                         hammer_ref_node(cursor->deadlk_node);
 171                 }
 172         } else {
 173                 error = 0;
 174         }
 175         if (cursor->parent && hammer_lock_held(&cursor->parent->lock) < 0) {
 176                 error = hammer_lock_upgrade(&cursor->parent->lock);
 177                 if (error && cursor->deadlk_node == NULL) {
 178                         cursor->deadlk_node = cursor->parent;
 179                         hammer_ref_node(cursor->deadlk_node);
 180                 }
 181         } else {
 182                 error = 0;
 183         }
 184         return(error);
 185 }
 186
 187 /*
 188  * Downgrade cursor->node and cursor->parent to shared locks.  This
 189  * function can return EDEADLK.
 190  */
 191 void
 192 hammer_cursor_downgrade(hammer_cursor_t cursor)
 193 {
 194         if (hammer_lock_held(&cursor->node->lock) > 0)
 195                 hammer_lock_downgrade(&cursor->node->lock);
 196         if (cursor->parent && hammer_lock_held(&cursor->parent->lock) > 0)
 197                 hammer_lock_downgrade(&cursor->parent->lock);
 198 }
 199
 200 /*
 201  * Seek the cursor to the specified node and index.
 202  */
 203 int
 204 hammer_cursor_seek(hammer_cursor_t cursor, hammer_node_t node, int index)
 205 {
 206         int error;
 207
 208         hammer_cursor_downgrade(cursor);
 209         error = 0;
 210
 211         if (cursor->node != node) {
 212                 hammer_unlock(&cursor->node->lock);
 213                 hammer_rel_node(cursor->node);
 214                 cursor->node = node;
 215                 cursor->index = index;
 216                 hammer_ref_node(node);
 217                 hammer_lock_sh(&node->lock);
 218
 219                 if (cursor->parent) {
 220                         hammer_unlock(&cursor->parent->lock);
 221                         hammer_rel_node(cursor->parent);
 222                         cursor->parent = NULL;
 223                         cursor->parent_index = 0;
 224                 }
 225                 error = hammer_load_cursor_parent(cursor);
 226         }
 227         return (error);
 228 }
 229
 230 /*
 231  * Load the parent of cursor->node into cursor->parent.
 232  */
 233 static
 234 int
 235 hammer_load_cursor_parent(hammer_cursor_t cursor)
 236 {
 237         hammer_mount_t hmp;
 238         hammer_node_t parent;
 239         hammer_node_t node;
 240         hammer_btree_elm_t elm;
 241         int error;
 242         int i;
 243
 244         hmp = cursor->node->volume->hmp;
 245
 246         if (cursor->node->ondisk->parent) {
 247                 node = cursor->node;
 248                 parent = hammer_get_node(node->volume->hmp,
 249                                          node->ondisk->parent, &error);
 250                 if (error)
 251                         return(error);
 252                 elm = NULL;
 253                 for (i = 0; i < parent->ondisk->count; ++i) {
 254                         elm = &parent->ondisk->elms[i];
 255                         if (parent->ondisk->elms[i].internal.subtree_offset ==
 256                             node->node_offset) {
 257                                 break;
 258                         }
 259                 }
 260                 if (i == parent->ondisk->count)
 261                         panic("Bad B-Tree link: parent %p node %p\n", parent, node);
 262                 KKASSERT(i != parent->ondisk->count);
 263                 cursor->parent = parent;
 264                 cursor->parent_index = i;
 265                 cursor->left_bound = &elm[0].internal.base;
 266                 cursor->right_bound = &elm[1].internal.base;
 267
 268                 hammer_lock_sh(&parent->lock);
 269                 return(error);
 270         } else {
 271                 cursor->parent = NULL;
 272                 cursor->parent_index = 0;
 273                 cursor->left_bound = &hmp->root_btree_beg;
 274                 cursor->right_bound = &hmp->root_btree_end;
 275                 error = 0;
 276         }
 277         return(error);
 278 }
 279
 280 /*
 281  * Cursor up to our parent node.  Return ENOENT if we are at the root of
 282  * the filesystem.
 283  *
 284  * If doing a nonblocking cursor-up and we are unable to acquire the lock,
 285  * the cursor remains unchanged.
 286  */
 287 int
 288 hammer_cursor_up(hammer_cursor_t cursor)
 289 {
 290         int error;
 291
 292         hammer_cursor_downgrade(cursor);
 293
 294         /*
 295          * Set the node to its parent.  If the parent is NULL we are at
 296          * the root of the filesystem and return ENOENT.
 297          */
 298         hammer_unlock(&cursor->node->lock);
 299         hammer_rel_node(cursor->node);
 300         cursor->node = cursor->parent;
 301         cursor->index = cursor->parent_index;
 302         cursor->parent = NULL;
 303         cursor->parent_index = 0;
 304
 305         if (cursor->node == NULL) {
 306                 error = ENOENT;
 307         } else {
 308                 error = hammer_load_cursor_parent(cursor);
 309         }
 310         return(error);
 311 }
 312
 313 /*
 314  * Cursor down through the current node, which must be an internal node.
 315  *
 316  * This routine adjusts the cursor and sets index to 0.
 317  */
 318 int
 319 hammer_cursor_down(hammer_cursor_t cursor)
 320 {
 321         hammer_node_t node;
 322         hammer_btree_elm_t elm;
 323         int error;
 324
 325         /*
 326          * The current node becomes the current parent
 327          */
 328         hammer_cursor_downgrade(cursor);
 329         node = cursor->node;
 330         KKASSERT(cursor->index >= 0 && cursor->index < node->ondisk->count);
 331         if (cursor->parent) {
 332                 hammer_unlock(&cursor->parent->lock);
 333                 hammer_rel_node(cursor->parent);
 334         }
 335         cursor->parent = node;
 336         cursor->parent_index = cursor->index;
 337         cursor->node = NULL;
 338         cursor->index = 0;
 339
 340         /*
 341          * Extract element to push into at (node,index), set bounds.
 342          */
 343         elm = &node->ondisk->elms[cursor->parent_index];
 344
 345         /*
 346          * Ok, push down into elm.  If elm specifies an internal or leaf
 347          * node the current node must be an internal node.  If elm specifies
 348          * a spike then the current node must be a leaf node.
 349          */
 350         switch(elm->base.btype) {
 351         case HAMMER_BTREE_TYPE_INTERNAL:
 352         case HAMMER_BTREE_TYPE_LEAF:
 353                 KKASSERT(node->ondisk->type == HAMMER_BTREE_TYPE_INTERNAL);
 354                 KKASSERT(elm->internal.subtree_offset != 0);
 355                 cursor->left_bound = &elm[0].internal.base;
 356                 cursor->right_bound = &elm[1].internal.base;
 357                 node = hammer_get_node(node->volume->hmp,
 358                                        elm->internal.subtree_offset,
 359                                        &error);
 360                 if (error == 0) {
 361                         KKASSERT(elm->base.btype == node->ondisk->type);
 362                         if (node->ondisk->parent != cursor->parent->node_offset)
 363                                 panic("node %p %016llx vs %016llx\n", node, node->ondisk->parent, cursor->parent->node_offset);
 364                         KKASSERT(node->ondisk->parent == cursor->parent->node_offset);
 365                 }
 366                 break;
 367         default:
 368                 panic("hammer_cursor_down: illegal btype %02x (%c)\n",
 369                       elm->base.btype,
 370                       (elm->base.btype ? elm->base.btype : '?'));
 371                 break;
 372         }
 373         if (error == 0) {
 374                 hammer_lock_sh(&node->lock);
 375                 cursor->node = node;
 376                 cursor->index = 0;
 377         }
 378         return(error);
 379 }
 380