sys/vfs/hammer/hammer_prune.c

   1 /*
   2  * Copyright (c) 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_prune.c,v 1.3 2008/05/31 18:37:57 dillon Exp $
  35  */
  36
  37 #include "hammer.h"
  38
  39 /*
  40  * Iterate through the specified range of object ids and remove any
  41  * deleted records that fall entirely within a prune modulo.
  42  *
  43  * A reverse iteration is used to prevent overlapping records from being
  44  * created during the iteration due to alignments.  This also allows us
  45  * to adjust alignments without blowing up the B-Tree.
  46  */
  47 static int check_prune(struct hammer_ioc_prune *prune, hammer_btree_elm_t elm,
  48                         int *realign_cre, int *realign_del);
  49 static int realign_prune(struct hammer_ioc_prune *prune, hammer_cursor_t cursor,
  50                         int realign_cre, int realign_del);
  51
  52 int
  53 hammer_ioc_prune(hammer_transaction_t trans, hammer_inode_t ip,
  54                  struct hammer_ioc_prune *prune)
  55 {
  56         struct hammer_cursor cursor;
  57         hammer_btree_elm_t elm;
  58         struct hammer_ioc_prune_elm *copy_elms;
  59         struct hammer_ioc_prune_elm *user_elms;
  60         int error;
  61         int isdir;
  62         int realign_cre;
  63         int realign_del;
  64         int elm_array_size;
  65
  66         if (prune->nelms < 0 || prune->nelms > HAMMER_MAX_PRUNE_ELMS)
  67                 return(EINVAL);
  68         if (prune->beg_obj_id >= prune->end_obj_id)
  69                 return(EINVAL);
  70         if ((prune->head.flags & HAMMER_IOC_PRUNE_ALL) && prune->nelms)
  71                 return(EINVAL);
  72
  73         prune->cur_localization = prune->end_localization;
  74         prune->cur_obj_id = prune->end_obj_id;
  75         prune->cur_key = HAMMER_MAX_KEY;
  76
  77         /*
  78          * Copy element array from userland
  79          */
  80         elm_array_size = sizeof(*copy_elms) * prune->nelms;
  81         user_elms = prune->elms;
  82         copy_elms = kmalloc(elm_array_size, M_TEMP, M_WAITOK);
  83         if ((error = copyin(user_elms, copy_elms, elm_array_size)) != 0)
  84                 goto failed;
  85         prune->elms = copy_elms;
  86
  87         /*
  88          * Scan backwards.  Retries typically occur if a deadlock is detected.
  89          */
  90 retry:
  91         error = hammer_init_cursor(trans, &cursor, NULL, NULL);
  92         if (error) {
  93                 hammer_done_cursor(&cursor);
  94                 goto failed;
  95         }
  96         cursor.key_beg.localization = prune->beg_localization;
  97         cursor.key_beg.obj_id = prune->beg_obj_id;
  98         cursor.key_beg.key = HAMMER_MIN_KEY;
  99         cursor.key_beg.create_tid = 1;
 100         cursor.key_beg.delete_tid = 0;
 101         cursor.key_beg.rec_type = HAMMER_MIN_RECTYPE;
 102         cursor.key_beg.obj_type = 0;
 103
 104         cursor.key_end.localization = prune->cur_localization;
 105         cursor.key_end.obj_id = prune->cur_obj_id;
 106         cursor.key_end.key = prune->cur_key;
 107         cursor.key_end.create_tid = HAMMER_MAX_TID - 1;
 108         cursor.key_end.delete_tid = 0;
 109         cursor.key_end.rec_type = HAMMER_MAX_RECTYPE;
 110         cursor.key_end.obj_type = 0;
 111
 112         cursor.flags |= HAMMER_CURSOR_END_INCLUSIVE;
 113         cursor.flags |= HAMMER_CURSOR_BACKEND;
 114
 115         /*
 116          * This flag allows the B-Tree code to clean up loose ends.
 117          */
 118         cursor.flags |= HAMMER_CURSOR_PRUNING;
 119
 120         hammer_sync_lock_sh(trans);
 121         error = hammer_btree_last(&cursor);
 122         while (error == 0) {
 123                 /*
 124                  * Yield to more important tasks
 125                  */
 126                 if (trans->hmp->sync_lock.wanted) {
 127                         hammer_sync_unlock(trans);
 128                         tsleep(trans, 0, "hmrslo", hz / 10);
 129                         hammer_sync_lock_sh(trans);
 130                 }
 131
 132                 /*
 133                  * Check for work
 134                  */
 135                 elm = &cursor.node->ondisk->elms[cursor.index];
 136                 prune->cur_localization = elm->base.localization;
 137                 prune->cur_obj_id = elm->base.obj_id;
 138                 prune->cur_key = elm->base.key;
 139
 140                 if (prune->stat_oldest_tid > elm->leaf.base.create_tid)
 141                         prune->stat_oldest_tid = elm->leaf.base.create_tid;
 142
 143                 if (check_prune(prune, elm, &realign_cre, &realign_del) == 0) {
 144                         if (hammer_debug_general & 0x0200) {
 145                                 kprintf("check %016llx %016llx: DELETE\n",
 146                                         elm->base.obj_id, elm->base.key);
 147                         }
 148
 149                         /*
 150                          * NOTE: This can return EDEADLK
 151                          *
 152                          * Acquiring the sync lock guarantees that the
 153                          * operation will not cross a synchronization
 154                          * boundary (see the flusher).
 155                          */
 156                         isdir = (elm->base.rec_type == HAMMER_RECTYPE_DIRENTRY);
 157
 158                         error = hammer_delete_at_cursor(&cursor,
 159                                                         &prune->stat_bytes);
 160                         if (error)
 161                                 break;
 162
 163                         if (isdir)
 164                                 ++prune->stat_dirrecords;
 165                         else
 166                                 ++prune->stat_rawrecords;
 167
 168                         /*
 169                          * The current record might now be the one after
 170                          * the one we deleted, set ATEDISK to force us
 171                          * to skip it (since we are iterating backwards).
 172                          */
 173                         cursor.flags |= HAMMER_CURSOR_ATEDISK;
 174                 } else if (realign_cre >= 0 || realign_del >= 0) {
 175                         error = realign_prune(prune, &cursor,
 176                                               realign_cre, realign_del);
 177                         if (error == 0) {
 178                                 cursor.flags |= HAMMER_CURSOR_ATEDISK;
 179                                 if (hammer_debug_general & 0x0200) {
 180                                         kprintf("check %016llx %016llx: "
 181                                                 "REALIGN\n",
 182                                                 elm->base.obj_id,
 183                                                 elm->base.key);
 184                                 }
 185                         }
 186                 } else {
 187                         cursor.flags |= HAMMER_CURSOR_ATEDISK;
 188                         if (hammer_debug_general & 0x0100) {
 189                                 kprintf("check %016llx %016llx: SKIP\n",
 190                                         elm->base.obj_id, elm->base.key);
 191                         }
 192                 }
 193                 ++prune->stat_scanrecords;
 194
 195                 /*
 196                  * Bad hack for now, don't blow out the kernel's buffer
 197                  * cache.  NOTE: We still hold locks on the cursor, we
 198                  * cannot call the flusher synchronously.
 199                  */
 200                 if (trans->hmp->locked_dirty_count +
 201                     trans->hmp->io_running_count > hammer_limit_dirtybufs) {
 202                         hammer_flusher_async(trans->hmp);
 203                         tsleep(trans, 0, "hmrslo", hz / 10);
 204                 }
 205                 error = hammer_signal_check(trans->hmp);
 206                 if (error == 0)
 207                         error = hammer_btree_iterate_reverse(&cursor);
 208         }
 209         hammer_sync_unlock(trans);
 210         if (error == ENOENT)
 211                 error = 0;
 212         hammer_done_cursor(&cursor);
 213         if (error == EDEADLK)
 214                 goto retry;
 215         if (error == EINTR) {
 216                 prune->head.flags |= HAMMER_IOC_HEAD_INTR;
 217                 error = 0;
 218         }
 219 failed:
 220         prune->elms = user_elms;
 221         kfree(copy_elms, M_TEMP);
 222         return(error);
 223 }
 224
 225 /*
 226  * Check pruning list.  The list must be sorted in descending order.
 227  */
 228 static int
 229 check_prune(struct hammer_ioc_prune *prune, hammer_btree_elm_t elm,
 230             int *realign_cre, int *realign_del)
 231 {
 232         struct hammer_ioc_prune_elm *scan;
 233         int i;
 234
 235         *realign_cre = -1;
 236         *realign_del = -1;
 237
 238         /*
 239          * If pruning everything remove all records with a non-zero
 240          * delete_tid.
 241          */
 242         if (prune->head.flags & HAMMER_IOC_PRUNE_ALL) {
 243                 if (elm->base.delete_tid != 0)
 244                         return(0);
 245                 return(-1);
 246         }
 247
 248         for (i = 0; i < prune->nelms; ++i) {
 249                 scan = &prune->elms[i];
 250
 251                 /*
 252                  * Locate the scan index covering the create and delete TIDs.
 253                  */
 254                 if (*realign_cre < 0 &&
 255                     elm->base.create_tid >= scan->beg_tid &&
 256                     elm->base.create_tid < scan->end_tid) {
 257                         *realign_cre = i;
 258                 }
 259                 if (*realign_del < 0 && elm->base.delete_tid &&
 260                     elm->base.delete_tid > scan->beg_tid &&
 261                     elm->base.delete_tid <= scan->end_tid) {
 262                         *realign_del = i;
 263                 }
 264
 265                 /*
 266                  * Now check for loop termination.
 267                  */
 268                 if (elm->base.create_tid >= scan->end_tid ||
 269                     elm->base.delete_tid > scan->end_tid) {
 270                         break;
 271                 }
 272
 273                 /*
 274                  * Now determine if we can delete the record.
 275                  */
 276                 if (elm->base.delete_tid &&
 277                     elm->base.create_tid >= scan->beg_tid &&
 278                     elm->base.delete_tid <= scan->end_tid &&
 279                     (elm->base.create_tid - scan->beg_tid) / scan->mod_tid ==
 280                     (elm->base.delete_tid - scan->beg_tid) / scan->mod_tid) {
 281                         return(0);
 282                 }
 283         }
 284         return(-1);
 285 }
 286
 287 /*
 288  * Align the record to cover any gaps created through the deletion of
 289  * records within the pruning space.  If we were to just delete the records
 290  * there would be gaps which in turn would cause a snapshot that is NOT on
 291  * a pruning boundary to appear corrupt to the user.  Forcing alignment
 292  * of the create_tid and delete_tid for retained records 'reconnects'
 293  * the previously contiguous space, making it contiguous again after the
 294  * deletions.
 295  *
 296  * The use of a reverse iteration allows us to safely align the records and
 297  * related elements without creating temporary overlaps.  XXX we should
 298  * add ordering dependancies for record buffers to guarantee consistency
 299  * during recovery.
 300  */
 301 static int
 302 realign_prune(struct hammer_ioc_prune *prune,
 303               hammer_cursor_t cursor, int realign_cre, int realign_del)
 304 {
 305         struct hammer_ioc_prune_elm *scan;
 306         hammer_btree_elm_t elm;
 307         hammer_tid_t delta;
 308         hammer_tid_t tid;
 309         int error;
 310
 311         hammer_cursor_downgrade(cursor);
 312
 313         elm = &cursor->node->ondisk->elms[cursor->index];
 314         ++prune->stat_realignments;
 315
 316         /*
 317          * Align the create_tid.  By doing a reverse iteration we guarantee
 318          * that all records after our current record have already been
 319          * aligned, allowing us to safely correct the right-hand-boundary
 320          * (because no record to our right is otherwise exactly matching
 321          * will have a create_tid to the left of our aligned create_tid).
 322          */
 323         error = 0;
 324         if (realign_cre >= 0) {
 325                 scan = &prune->elms[realign_cre];
 326
 327                 delta = (elm->leaf.base.create_tid - scan->beg_tid) %
 328                         scan->mod_tid;
 329                 if (delta) {
 330                         tid = elm->leaf.base.create_tid - delta + scan->mod_tid;
 331
 332                         /* can EDEADLK */
 333                         error = hammer_btree_correct_rhb(cursor, tid + 1);
 334                         if (error == 0) {
 335                                 error = hammer_btree_extract(cursor,
 336                                                      HAMMER_CURSOR_GET_LEAF);
 337                         }
 338                         if (error == 0) {
 339                                 /* can EDEADLK */
 340                                 error = hammer_cursor_upgrade(cursor);
 341                         }
 342                         if (error == 0) {
 343                                 hammer_modify_node(cursor->trans, cursor->node,
 344                                             &elm->leaf.base.create_tid,
 345                                             sizeof(elm->leaf.base.create_tid));
 346                                 elm->leaf.base.create_tid = tid;
 347                                 hammer_modify_node_done(cursor->node);
 348                         }
 349                 }
 350         }
 351
 352         /*
 353          * Align the delete_tid.  This only occurs if the record is historical
 354          * was deleted at some point.  Realigning the delete_tid does not
 355          * move the record within the B-Tree but may cause it to temporarily
 356          * overlap a record that has not yet been pruned.
 357          */
 358         if (error == 0 && realign_del >= 0) {
 359                 scan = &prune->elms[realign_del];
 360
 361                 delta = (elm->leaf.base.delete_tid - scan->beg_tid) %
 362                         scan->mod_tid;
 363                 if (delta) {
 364                         error = hammer_btree_extract(cursor,
 365                                                      HAMMER_CURSOR_GET_LEAF);
 366                         if (error == 0) {
 367                                 hammer_modify_node(cursor->trans, cursor->node,
 368                                             &elm->leaf.base.delete_tid,
 369                                             sizeof(elm->leaf.base.delete_tid));
 370                                 elm->leaf.base.delete_tid =
 371                                             elm->leaf.base.delete_tid -
 372                                             delta + scan->mod_tid;
 373                                 hammer_modify_node_done(cursor->node);
 374                         }
 375                 }
 376         }
 377         return (error);
 378 }
 379