sys/vfs/hammer/hammer_cursor.c

   1 /*
   2  * Copyright (c) 2007-2008 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 1.22 2008/04/24 21:20:33 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(hammer_transaction_t trans, hammer_cursor_t cursor,
  50                    struct hammer_node **cache)
  51 {
  52         hammer_volume_t volume;
  53         hammer_node_t node;
  54         int error;
  55
  56         bzero(cursor, sizeof(*cursor));
  57
  58         cursor->trans = trans;
  59
  60         /*
  61          * Step 1 - acquire a locked node from the cache if possible
  62          */
  63         if (cache && *cache) {
  64                 node = hammer_ref_node_safe(trans->hmp, cache, &error);
  65                 if (error == 0) {
  66                         hammer_lock_sh(&node->lock);
  67                         if (node->flags & HAMMER_NODE_DELETED) {
  68                                 hammer_unlock(&node->lock);
  69                                 hammer_rel_node(node);
  70                                 node = NULL;
  71                         }
  72                 }
  73         } else {
  74                 node = NULL;
  75         }
  76
  77         /*
  78          * Step 2 - If we couldn't get a node from the cache, get
  79          * the one from the root of the filesystem.
  80          */
  81         while (node == NULL) {
  82                 volume = hammer_get_root_volume(trans->hmp, &error);
  83                 if (error)
  84                         break;
  85                 node = hammer_get_node(trans->hmp,
  86                                        volume->ondisk->vol0_btree_root, &error);
  87                 hammer_rel_volume(volume, 0);
  88                 if (error)
  89                         break;
  90                 hammer_lock_sh(&node->lock);
  91                 if (node->flags & HAMMER_NODE_DELETED) {
  92                         hammer_unlock(&node->lock);
  93                         hammer_rel_node(node);
  94                         node = NULL;
  95                 }
  96         }
  97
  98         /*
  99          * Step 3 - finish initializing the cursor by acquiring the parent
 100          */
 101         cursor->node = node;
 102         if (error == 0)
 103                 error = hammer_load_cursor_parent(cursor);
 104         KKASSERT(error == 0);
 105         /* if (error) hammer_done_cursor(cursor); */
 106         return(error);
 107 }
 108
 109 /*
 110  * We are finished with a cursor.  We NULL out various fields as sanity
 111  * check, in case the structure is inappropriately used afterwords.
 112  */
 113 void
 114 hammer_done_cursor(hammer_cursor_t cursor)
 115 {
 116         if (cursor->parent) {
 117                 hammer_unlock(&cursor->parent->lock);
 118                 hammer_rel_node(cursor->parent);
 119                 cursor->parent = NULL;
 120         }
 121         if (cursor->node) {
 122                 hammer_unlock(&cursor->node->lock);
 123                 hammer_rel_node(cursor->node);
 124                 cursor->node = NULL;
 125         }
 126         if (cursor->data_buffer) {
 127                 hammer_rel_buffer(cursor->data_buffer, 0);
 128                 cursor->data_buffer = NULL;
 129         }
 130         if (cursor->record_buffer) {
 131                 hammer_rel_buffer(cursor->record_buffer, 0);
 132                 cursor->record_buffer = NULL;
 133         }
 134         if (cursor->ip)
 135                 hammer_mem_done(cursor);
 136
 137         /*
 138          * If we deadlocked this node will be referenced.  Do a quick
 139          * lock/unlock to wait for the deadlock condition to clear.
 140          */
 141         if (cursor->deadlk_node) {
 142                 hammer_lock_ex(&cursor->deadlk_node->lock);
 143                 hammer_unlock(&cursor->deadlk_node->lock);
 144                 hammer_rel_node(cursor->deadlk_node);
 145                 cursor->deadlk_node = NULL;
 146         }
 147         if (cursor->deadlk_rec) {
 148                 hammer_wait_mem_record(cursor->deadlk_rec);
 149                 hammer_rel_mem_record(cursor->deadlk_rec);
 150                 cursor->deadlk_rec = NULL;
 151         }
 152
 153         cursor->data = NULL;
 154         cursor->record = NULL;
 155         cursor->left_bound = NULL;
 156         cursor->right_bound = NULL;
 157         cursor->trans = NULL;
 158 }
 159
 160 /*
 161  * Upgrade cursor->node and cursor->parent to exclusive locks.  This
 162  * function can return EDEADLK.
 163  *
 164  * The lock must already be either held shared or already held exclusively
 165  * by us.
 166  *
 167  * If we fail to upgrade the lock and cursor->deadlk_node is NULL,
 168  * we add another reference to the node that failed and set
 169  * cursor->deadlk_node so hammer_done_cursor() can block on it.
 170  */
 171 int
 172 hammer_cursor_upgrade(hammer_cursor_t cursor)
 173 {
 174         int error;
 175
 176         error = hammer_lock_upgrade(&cursor->node->lock);
 177         if (error && cursor->deadlk_node == NULL) {
 178                 cursor->deadlk_node = cursor->node;
 179                 hammer_ref_node(cursor->deadlk_node);
 180         } else if (error == 0 && cursor->parent) {
 181                 error = hammer_lock_upgrade(&cursor->parent->lock);
 182                 if (error && cursor->deadlk_node == NULL) {
 183                         cursor->deadlk_node = cursor->parent;
 184                         hammer_ref_node(cursor->deadlk_node);
 185                 }
 186         }
 187         return(error);
 188 }
 189
 190 /*
 191  * Downgrade cursor->node and cursor->parent to shared locks.  This
 192  * function can return EDEADLK.
 193  */
 194 void
 195 hammer_cursor_downgrade(hammer_cursor_t cursor)
 196 {
 197         if (hammer_lock_excl_owned(&cursor->node->lock, curthread))
 198                 hammer_lock_downgrade(&cursor->node->lock);
 199         if (cursor->parent &&
 200             hammer_lock_excl_owned(&cursor->parent->lock, curthread)) {
 201                 hammer_lock_downgrade(&cursor->parent->lock);
 202         }
 203 }
 204
 205 /*
 206  * Seek the cursor to the specified node and index.
 207  */
 208 int
 209 hammer_cursor_seek(hammer_cursor_t cursor, hammer_node_t node, int index)
 210 {
 211         int error;
 212
 213         hammer_cursor_downgrade(cursor);
 214         error = 0;
 215
 216         if (cursor->node != node) {
 217                 hammer_unlock(&cursor->node->lock);
 218                 hammer_rel_node(cursor->node);
 219                 cursor->node = node;
 220                 hammer_ref_node(node);
 221                 hammer_lock_sh(&node->lock);
 222
 223                 if (cursor->parent) {
 224                         hammer_unlock(&cursor->parent->lock);
 225                         hammer_rel_node(cursor->parent);
 226                         cursor->parent = NULL;
 227                         cursor->parent_index = 0;
 228                 }
 229                 error = hammer_load_cursor_parent(cursor);
 230         }
 231         cursor->index = index;
 232         return (error);
 233 }
 234
 235 /*
 236  * Load the parent of cursor->node into cursor->parent.
 237  */
 238 static
 239 int
 240 hammer_load_cursor_parent(hammer_cursor_t cursor)
 241 {
 242         hammer_mount_t hmp;
 243         hammer_node_t parent;
 244         hammer_node_t node;
 245         hammer_btree_elm_t elm;
 246         int error;
 247         int i;
 248
 249         hmp = cursor->trans->hmp;
 250
 251         if (cursor->node->ondisk->parent) {
 252                 node = cursor->node;
 253                 parent = hammer_get_node(hmp, node->ondisk->parent, &error);
 254                 if (error)
 255                         return(error);
 256                 hammer_lock_sh(&parent->lock);
 257                 elm = NULL;
 258                 for (i = 0; i < parent->ondisk->count; ++i) {
 259                         elm = &parent->ondisk->elms[i];
 260                         if (parent->ondisk->elms[i].internal.subtree_offset ==
 261                             node->node_offset) {
 262                                 break;
 263                         }
 264                 }
 265                 if (i == parent->ondisk->count) {
 266                         hammer_unlock(&parent->lock);
 267                         panic("Bad B-Tree link: parent %p node %p\n", parent, node);
 268                 }
 269                 KKASSERT(i != parent->ondisk->count);
 270                 cursor->parent = parent;
 271                 cursor->parent_index = i;
 272                 cursor->left_bound = &elm[0].internal.base;
 273                 cursor->right_bound = &elm[1].internal.base;
 274                 return(error);
 275         } else {
 276                 cursor->parent = NULL;
 277                 cursor->parent_index = 0;
 278                 cursor->left_bound = &hmp->root_btree_beg;
 279                 cursor->right_bound = &hmp->root_btree_end;
 280                 error = 0;
 281         }
 282         return(error);
 283 }
 284
 285 /*
 286  * Cursor up to our parent node.  Return ENOENT if we are at the root of
 287  * the filesystem.
 288  *
 289  * If doing a nonblocking cursor-up and we are unable to acquire the lock,
 290  * the cursor remains unchanged.
 291  */
 292 int
 293 hammer_cursor_up(hammer_cursor_t cursor)
 294 {
 295         int error;
 296
 297         hammer_cursor_downgrade(cursor);
 298
 299         /*
 300          * Set the node to its parent.  If the parent is NULL we are at
 301          * the root of the filesystem and return ENOENT.
 302          */
 303         hammer_unlock(&cursor->node->lock);
 304         hammer_rel_node(cursor->node);
 305         cursor->node = cursor->parent;
 306         cursor->index = cursor->parent_index;
 307         cursor->parent = NULL;
 308         cursor->parent_index = 0;
 309
 310         if (cursor->node == NULL) {
 311                 error = ENOENT;
 312         } else {
 313                 error = hammer_load_cursor_parent(cursor);
 314         }
 315         return(error);
 316 }
 317
 318 /*
 319  * Cursor down through the current node, which must be an internal node.
 320  *
 321  * This routine adjusts the cursor and sets index to 0.
 322  */
 323 int
 324 hammer_cursor_down(hammer_cursor_t cursor)
 325 {
 326         hammer_node_t node;
 327         hammer_btree_elm_t elm;
 328         int error;
 329
 330         /*
 331          * The current node becomes the current parent
 332          */
 333         hammer_cursor_downgrade(cursor);
 334         node = cursor->node;
 335         KKASSERT(cursor->index >= 0 && cursor->index < node->ondisk->count);
 336         if (cursor->parent) {
 337                 hammer_unlock(&cursor->parent->lock);
 338                 hammer_rel_node(cursor->parent);
 339         }
 340         cursor->parent = node;
 341         cursor->parent_index = cursor->index;
 342         cursor->node = NULL;
 343         cursor->index = 0;
 344
 345         /*
 346          * Extract element to push into at (node,index), set bounds.
 347          */
 348         elm = &node->ondisk->elms[cursor->parent_index];
 349
 350         /*
 351          * Ok, push down into elm.  If elm specifies an internal or leaf
 352          * node the current node must be an internal node.  If elm specifies
 353          * a spike then the current node must be a leaf node.
 354          */
 355         switch(elm->base.btype) {
 356         case HAMMER_BTREE_TYPE_INTERNAL:
 357         case HAMMER_BTREE_TYPE_LEAF:
 358                 KKASSERT(node->ondisk->type == HAMMER_BTREE_TYPE_INTERNAL);
 359                 KKASSERT(elm->internal.subtree_offset != 0);
 360                 cursor->left_bound = &elm[0].internal.base;
 361                 cursor->right_bound = &elm[1].internal.base;
 362                 node = hammer_get_node(cursor->trans->hmp,
 363                                        elm->internal.subtree_offset, &error);
 364                 if (error == 0) {
 365                         KASSERT(elm->base.btype == node->ondisk->type, ("BTYPE MISMATCH %c %c NODE %p\n", elm->base.btype, node->ondisk->type, node));
 366                         if (node->ondisk->parent != cursor->parent->node_offset)
 367                                 panic("node %p %016llx vs %016llx\n", node, node->ondisk->parent, cursor->parent->node_offset);
 368                         KKASSERT(node->ondisk->parent == cursor->parent->node_offset);
 369                 }
 370                 break;
 371         default:
 372                 panic("hammer_cursor_down: illegal btype %02x (%c)\n",
 373                       elm->base.btype,
 374                       (elm->base.btype ? elm->base.btype : '?'));
 375                 break;
 376         }
 377         if (error == 0) {
 378                 hammer_lock_sh(&node->lock);
 379                 cursor->node = node;
 380                 cursor->index = 0;
 381         }
 382         return(error);
 383 }
 384