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 1.18 2008/02/10 09:51:01 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->data = NULL;
 146         cursor->record = NULL;
 147         cursor->left_bound = NULL;
 148         cursor->right_bound = NULL;
 149 }
 150
 151 /*
 152  * Upgrade cursor->node and cursor->parent to exclusive locks.  This
 153  * function can return EDEADLK.
 154  *
 155  * If we fail to upgrade the lock and cursor->deadlk_node is NULL,
 156  * we add another reference to the node that failed and set
 157  * cursor->deadlk_node so hammer_done_cursor() can block on it.
 158  */
 159 int
 160 hammer_cursor_upgrade(hammer_cursor_t cursor)
 161 {
 162         int error;
 163
 164         if (hammer_lock_held(&cursor->node->lock) < 0) {
 165                 error = hammer_lock_upgrade(&cursor->node->lock);
 166                 if (error && cursor->deadlk_node == NULL) {
 167                         cursor->deadlk_node = cursor->node;
 168                         hammer_ref_node(cursor->deadlk_node);
 169                 }
 170         } else {
 171                 error = 0;
 172         }
 173         if (cursor->parent && hammer_lock_held(&cursor->parent->lock) < 0) {
 174                 error = hammer_lock_upgrade(&cursor->parent->lock);
 175                 if (error && cursor->deadlk_node == NULL) {
 176                         cursor->deadlk_node = cursor->parent;
 177                         hammer_ref_node(cursor->deadlk_node);
 178                 }
 179         } else {
 180                 error = 0;
 181         }
 182         return(error);
 183 }
 184
 185 /*
 186  * Downgrade cursor->node and cursor->parent to shared locks.  This
 187  * function can return EDEADLK.
 188  */
 189 void
 190 hammer_cursor_downgrade(hammer_cursor_t cursor)
 191 {
 192         if (hammer_lock_held(&cursor->node->lock) > 0)
 193                 hammer_lock_downgrade(&cursor->node->lock);
 194         if (cursor->parent && hammer_lock_held(&cursor->parent->lock) > 0)
 195                 hammer_lock_downgrade(&cursor->parent->lock);
 196 }
 197
 198 /*
 199  * Seek the cursor to the specified node and index.
 200  */
 201 int
 202 hammer_cursor_seek(hammer_cursor_t cursor, hammer_node_t node, int index)
 203 {
 204         int error;
 205
 206         hammer_cursor_downgrade(cursor);
 207         error = 0;
 208
 209         if (cursor->node != node) {
 210                 hammer_unlock(&cursor->node->lock);
 211                 hammer_rel_node(cursor->node);
 212                 cursor->node = node;
 213                 cursor->index = index;
 214                 hammer_ref_node(node);
 215                 hammer_lock_sh(&node->lock);
 216
 217                 if (cursor->parent) {
 218                         hammer_unlock(&cursor->parent->lock);
 219                         hammer_rel_node(cursor->parent);
 220                         cursor->parent = NULL;
 221                         cursor->parent_index = 0;
 222                 }
 223                 error = hammer_load_cursor_parent(cursor);
 224         }
 225         return (error);
 226 }
 227
 228 /*
 229  * Load the parent of cursor->node into cursor->parent.
 230  */
 231 static
 232 int
 233 hammer_load_cursor_parent(hammer_cursor_t cursor)
 234 {
 235         hammer_mount_t hmp;
 236         hammer_node_t parent;
 237         hammer_node_t node;
 238         hammer_btree_elm_t elm;
 239         int error;
 240         int i;
 241
 242         hmp = cursor->node->hmp;
 243
 244         if (cursor->node->ondisk->parent) {
 245                 node = cursor->node;
 246                 parent = hammer_get_node(node->hmp,
 247                                          node->ondisk->parent, &error);
 248                 if (error)
 249                         return(error);
 250                 elm = NULL;
 251                 for (i = 0; i < parent->ondisk->count; ++i) {
 252                         elm = &parent->ondisk->elms[i];
 253                         if (parent->ondisk->elms[i].internal.subtree_offset ==
 254                             node->node_offset) {
 255                                 break;
 256                         }
 257                 }
 258                 if (i == parent->ondisk->count)
 259                         panic("Bad B-Tree link: parent %p node %p\n", parent, node);
 260                 KKASSERT(i != parent->ondisk->count);
 261                 cursor->parent = parent;
 262                 cursor->parent_index = i;
 263                 cursor->left_bound = &elm[0].internal.base;
 264                 cursor->right_bound = &elm[1].internal.base;
 265
 266                 hammer_lock_sh(&parent->lock);
 267                 return(error);
 268         } else {
 269                 cursor->parent = NULL;
 270                 cursor->parent_index = 0;
 271                 cursor->left_bound = &hmp->root_btree_beg;
 272                 cursor->right_bound = &hmp->root_btree_end;
 273                 error = 0;
 274         }
 275         return(error);
 276 }
 277
 278 /*
 279  * Cursor up to our parent node.  Return ENOENT if we are at the root of
 280  * the filesystem.
 281  *
 282  * If doing a nonblocking cursor-up and we are unable to acquire the lock,
 283  * the cursor remains unchanged.
 284  */
 285 int
 286 hammer_cursor_up(hammer_cursor_t cursor)
 287 {
 288         int error;
 289
 290         hammer_cursor_downgrade(cursor);
 291
 292         /*
 293          * Set the node to its parent.  If the parent is NULL we are at
 294          * the root of the filesystem and return ENOENT.
 295          */
 296         hammer_unlock(&cursor->node->lock);
 297         hammer_rel_node(cursor->node);
 298         cursor->node = cursor->parent;
 299         cursor->index = cursor->parent_index;
 300         cursor->parent = NULL;
 301         cursor->parent_index = 0;
 302
 303         if (cursor->node == NULL) {
 304                 error = ENOENT;
 305         } else {
 306                 error = hammer_load_cursor_parent(cursor);
 307         }
 308         return(error);
 309 }
 310
 311 /*
 312  * Cursor down through the current node, which must be an internal node.
 313  *
 314  * This routine adjusts the cursor and sets index to 0.
 315  */
 316 int
 317 hammer_cursor_down(hammer_cursor_t cursor)
 318 {
 319         hammer_node_t node;
 320         hammer_btree_elm_t elm;
 321         int error;
 322
 323         /*
 324          * The current node becomes the current parent
 325          */
 326         hammer_cursor_downgrade(cursor);
 327         node = cursor->node;
 328         KKASSERT(cursor->index >= 0 && cursor->index < node->ondisk->count);
 329         if (cursor->parent) {
 330                 hammer_unlock(&cursor->parent->lock);
 331                 hammer_rel_node(cursor->parent);
 332         }
 333         cursor->parent = node;
 334         cursor->parent_index = cursor->index;
 335         cursor->node = NULL;
 336         cursor->index = 0;
 337
 338         /*
 339          * Extract element to push into at (node,index), set bounds.
 340          */
 341         elm = &node->ondisk->elms[cursor->parent_index];
 342
 343         /*
 344          * Ok, push down into elm.  If elm specifies an internal or leaf
 345          * node the current node must be an internal node.  If elm specifies
 346          * a spike then the current node must be a leaf node.
 347          */
 348         switch(elm->base.btype) {
 349         case HAMMER_BTREE_TYPE_INTERNAL:
 350         case HAMMER_BTREE_TYPE_LEAF:
 351                 KKASSERT(node->ondisk->type == HAMMER_BTREE_TYPE_INTERNAL);
 352                 KKASSERT(elm->internal.subtree_offset != 0);
 353                 cursor->left_bound = &elm[0].internal.base;
 354                 cursor->right_bound = &elm[1].internal.base;
 355                 node = hammer_get_node(node->hmp, elm->internal.subtree_offset,
 356                                        &error);
 357                 if (error == 0) {
 358                         KASSERT(elm->base.btype == node->ondisk->type, ("BTYPE MISMATCH %c %c NODE %p\n", elm->base.btype, node->ondisk->type, node));
 359                         if (node->ondisk->parent != cursor->parent->node_offset)
 360                                 panic("node %p %016llx vs %016llx\n", node, node->ondisk->parent, cursor->parent->node_offset);
 361                         KKASSERT(node->ondisk->parent == cursor->parent->node_offset);
 362                 }
 363                 break;
 364         default:
 365                 panic("hammer_cursor_down: illegal btype %02x (%c)\n",
 366                       elm->base.btype,
 367                       (elm->base.btype ? elm->base.btype : '?'));
 368                 break;
 369         }
 370         if (error == 0) {
 371                 hammer_lock_sh(&node->lock);
 372                 cursor->node = node;
 373                 cursor->index = 0;
 374         }
 375         return(error);
 376 }
 377