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 1.2 2008/05/18 01:48:50 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         int error;
  59         int isdir;
  60         int realign_cre;
  61         int realign_del;
  62
  63         if (prune->nelms < 0 || prune->nelms > HAMMER_MAX_PRUNE_ELMS)
  64                 return(EINVAL);
  65         if (prune->beg_obj_id >= prune->end_obj_id)
  66                 return(EINVAL);
  67         if ((prune->head.flags & HAMMER_IOC_PRUNE_ALL) && prune->nelms)
  68                 return(EINVAL);
  69
  70         prune->cur_localization = prune->end_localization;
  71         prune->cur_obj_id = prune->end_obj_id;
  72         prune->cur_key = HAMMER_MAX_KEY;
  73
  74 retry:
  75         error = hammer_init_cursor(trans, &cursor, NULL, NULL);
  76         if (error) {
  77                 hammer_done_cursor(&cursor);
  78                 return(error);
  79         }
  80         cursor.key_beg.localization = prune->beg_localization;
  81         cursor.key_beg.obj_id = prune->beg_obj_id;
  82         cursor.key_beg.key = HAMMER_MIN_KEY;
  83         cursor.key_beg.create_tid = 1;
  84         cursor.key_beg.delete_tid = 0;
  85         cursor.key_beg.rec_type = HAMMER_MIN_RECTYPE;
  86         cursor.key_beg.obj_type = 0;
  87
  88         cursor.key_end.localization = prune->cur_localization;
  89         cursor.key_end.obj_id = prune->cur_obj_id;
  90         cursor.key_end.key = prune->cur_key;
  91         cursor.key_end.create_tid = HAMMER_MAX_TID - 1;
  92         cursor.key_end.delete_tid = 0;
  93         cursor.key_end.rec_type = HAMMER_MAX_RECTYPE;
  94         cursor.key_end.obj_type = 0;
  95
  96         cursor.flags |= HAMMER_CURSOR_END_INCLUSIVE;
  97         cursor.flags |= HAMMER_CURSOR_BACKEND;
  98
  99         /*
 100          * This flag allows the B-Tree code to clean up loose ends.
 101          */
 102         cursor.flags |= HAMMER_CURSOR_PRUNING;
 103
 104         hammer_sync_lock_sh(trans);
 105         error = hammer_btree_last(&cursor);
 106         while (error == 0) {
 107                 /*
 108                  * Yield to more important tasks
 109                  */
 110                 if (trans->hmp->sync_lock.wanted) {
 111                         hammer_sync_unlock(trans);
 112                         tsleep(trans, 0, "hmrslo", hz / 10);
 113                         hammer_sync_lock_sh(trans);
 114                 }
 115
 116                 /*
 117                  * Check for work
 118                  */
 119                 elm = &cursor.node->ondisk->elms[cursor.index];
 120                 prune->cur_localization = elm->base.localization;
 121                 prune->cur_obj_id = elm->base.obj_id;
 122                 prune->cur_key = elm->base.key;
 123
 124                 if (prune->stat_oldest_tid > elm->leaf.base.create_tid)
 125                         prune->stat_oldest_tid = elm->leaf.base.create_tid;
 126
 127                 if (check_prune(prune, elm, &realign_cre, &realign_del) == 0) {
 128                         if (hammer_debug_general & 0x0200) {
 129                                 kprintf("check %016llx %016llx: DELETE\n",
 130                                         elm->base.obj_id, elm->base.key);
 131                         }
 132
 133                         /*
 134                          * NOTE: This can return EDEADLK
 135                          *
 136                          * Acquiring the sync lock guarantees that the
 137                          * operation will not cross a synchronization
 138                          * boundary (see the flusher).
 139                          */
 140                         isdir = (elm->base.rec_type == HAMMER_RECTYPE_DIRENTRY);
 141
 142                         error = hammer_delete_at_cursor(&cursor,
 143                                                         &prune->stat_bytes);
 144                         if (error)
 145                                 break;
 146
 147                         if (isdir)
 148                                 ++prune->stat_dirrecords;
 149                         else
 150                                 ++prune->stat_rawrecords;
 151
 152                         /*
 153                          * The current record might now be the one after
 154                          * the one we deleted, set ATEDISK to force us
 155                          * to skip it (since we are iterating backwards).
 156                          */
 157                         cursor.flags |= HAMMER_CURSOR_ATEDISK;
 158                 } else if (realign_cre >= 0 || realign_del >= 0) {
 159                         error = realign_prune(prune, &cursor,
 160                                               realign_cre, realign_del);
 161                         if (error == 0) {
 162                                 cursor.flags |= HAMMER_CURSOR_ATEDISK;
 163                                 if (hammer_debug_general & 0x0200) {
 164                                         kprintf("check %016llx %016llx: "
 165                                                 "REALIGN\n",
 166                                                 elm->base.obj_id,
 167                                                 elm->base.key);
 168                                 }
 169                         }
 170                 } else {
 171                         cursor.flags |= HAMMER_CURSOR_ATEDISK;
 172                         if (hammer_debug_general & 0x0100) {
 173                                 kprintf("check %016llx %016llx: SKIP\n",
 174                                         elm->base.obj_id, elm->base.key);
 175                         }
 176                 }
 177                 ++prune->stat_scanrecords;
 178
 179                 /*
 180                  * Bad hack for now, don't blow out the kernel's buffer
 181                  * cache.  NOTE: We still hold locks on the cursor, we
 182                  * cannot call the flusher synchronously.
 183                  */
 184                 if (trans->hmp->locked_dirty_count +
 185                     trans->hmp->io_running_count > hammer_limit_dirtybufs) {
 186                         hammer_flusher_async(trans->hmp);
 187                         tsleep(trans, 0, "hmrslo", hz / 10);
 188                 }
 189                 error = hammer_signal_check(trans->hmp);
 190                 if (error == 0)
 191                         error = hammer_btree_iterate_reverse(&cursor);
 192         }
 193         hammer_sync_unlock(trans);
 194         if (error == ENOENT)
 195                 error = 0;
 196         hammer_done_cursor(&cursor);
 197         if (error == EDEADLK)
 198                 goto retry;
 199         if (error == EINTR) {
 200                 prune->head.flags |= HAMMER_IOC_HEAD_INTR;
 201                 error = 0;
 202         }
 203         return(error);
 204 }
 205
 206 /*
 207  * Check pruning list.  The list must be sorted in descending order.
 208  */
 209 static int
 210 check_prune(struct hammer_ioc_prune *prune, hammer_btree_elm_t elm,
 211             int *realign_cre, int *realign_del)
 212 {
 213         struct hammer_ioc_prune_elm *scan;
 214         int i;
 215
 216         *realign_cre = -1;
 217         *realign_del = -1;
 218
 219         /*
 220          * If pruning everything remove all records with a non-zero
 221          * delete_tid.
 222          */
 223         if (prune->head.flags & HAMMER_IOC_PRUNE_ALL) {
 224                 if (elm->base.delete_tid != 0)
 225                         return(0);
 226                 return(-1);
 227         }
 228
 229         for (i = 0; i < prune->nelms; ++i) {
 230                 scan = &prune->elms[i];
 231
 232                 /*
 233                  * Locate the scan index covering the create and delete TIDs.
 234                  */
 235                 if (*realign_cre < 0 &&
 236                     elm->base.create_tid >= scan->beg_tid &&
 237                     elm->base.create_tid < scan->end_tid) {
 238                         *realign_cre = i;
 239                 }
 240                 if (*realign_del < 0 && elm->base.delete_tid &&
 241                     elm->base.delete_tid > scan->beg_tid &&
 242                     elm->base.delete_tid <= scan->end_tid) {
 243                         *realign_del = i;
 244                 }
 245
 246                 /*
 247                  * Now check for loop termination.
 248                  */
 249                 if (elm->base.create_tid >= scan->end_tid ||
 250                     elm->base.delete_tid > scan->end_tid) {
 251                         break;
 252                 }
 253
 254                 /*
 255                  * Now determine if we can delete the record.
 256                  */
 257                 if (elm->base.delete_tid &&
 258                     elm->base.create_tid >= scan->beg_tid &&
 259                     elm->base.delete_tid <= scan->end_tid &&
 260                     elm->base.create_tid / scan->mod_tid ==
 261                     elm->base.delete_tid / scan->mod_tid) {
 262                         return(0);
 263                 }
 264         }
 265         return(-1);
 266 }
 267
 268 /*
 269  * Align the record to cover any gaps created through the deletion of
 270  * records within the pruning space.  If we were to just delete the records
 271  * there would be gaps which in turn would cause a snapshot that is NOT on
 272  * a pruning boundary to appear corrupt to the user.  Forcing alignment
 273  * of the create_tid and delete_tid for retained records 'reconnects'
 274  * the previously contiguous space, making it contiguous again after the
 275  * deletions.
 276  *
 277  * The use of a reverse iteration allows us to safely align the records and
 278  * related elements without creating temporary overlaps.  XXX we should
 279  * add ordering dependancies for record buffers to guarantee consistency
 280  * during recovery.
 281  */
 282 static int
 283 realign_prune(struct hammer_ioc_prune *prune,
 284               hammer_cursor_t cursor, int realign_cre, int realign_del)
 285 {
 286         hammer_btree_elm_t elm;
 287         hammer_tid_t delta;
 288         hammer_tid_t mod;
 289         hammer_tid_t tid;
 290         int error;
 291
 292         hammer_cursor_downgrade(cursor);
 293
 294         elm = &cursor->node->ondisk->elms[cursor->index];
 295         ++prune->stat_realignments;
 296
 297         /*
 298          * Align the create_tid.  By doing a reverse iteration we guarantee
 299          * that all records after our current record have already been
 300          * aligned, allowing us to safely correct the right-hand-boundary
 301          * (because no record to our right if otherwise exactly matching
 302          * will have a create_tid to the left of our aligned create_tid).
 303          *
 304          * Ordering is important here XXX but disk write ordering for
 305          * inter-cluster corrections is not currently guaranteed.
 306          */
 307         error = 0;
 308         if (realign_cre >= 0) {
 309                 mod = prune->elms[realign_cre].mod_tid;
 310                 delta = elm->leaf.base.create_tid % mod;
 311                 if (delta) {
 312                         tid = elm->leaf.base.create_tid - delta + mod;
 313
 314                         /* can EDEADLK */
 315                         error = hammer_btree_correct_rhb(cursor, tid + 1);
 316                         if (error == 0) {
 317                                 error = hammer_btree_extract(cursor,
 318                                                      HAMMER_CURSOR_GET_LEAF);
 319                         }
 320                         if (error == 0) {
 321                                 /* can EDEADLK */
 322                                 error = hammer_cursor_upgrade(cursor);
 323                         }
 324                         if (error == 0) {
 325                                 hammer_modify_node(cursor->trans, cursor->node,
 326                                             &elm->leaf.base.create_tid,
 327                                             sizeof(elm->leaf.base.create_tid));
 328                                 elm->leaf.base.create_tid = tid;
 329                                 hammer_modify_node_done(cursor->node);
 330                         }
 331                 }
 332         }
 333
 334         /*
 335          * Align the delete_tid.  This only occurs if the record is historical
 336          * was deleted at some point.  Realigning the delete_tid does not
 337          * move the record within the B-Tree but may cause it to temporarily
 338          * overlap a record that has not yet been pruned.
 339          */
 340         if (error == 0 && realign_del >= 0) {
 341                 mod = prune->elms[realign_del].mod_tid;
 342                 delta = elm->leaf.base.delete_tid % mod;
 343                 if (delta) {
 344                         error = hammer_btree_extract(cursor,
 345                                                      HAMMER_CURSOR_GET_LEAF);
 346                         if (error == 0) {
 347                                 hammer_modify_node(cursor->trans, cursor->node,
 348                                             &elm->leaf.base.delete_tid,
 349                                             sizeof(elm->leaf.base.delete_tid));
 350                                 elm->leaf.base.delete_tid =
 351                                             elm->leaf.base.delete_tid -
 352                                             delta + mod;
 353                                 hammer_modify_node_done(cursor->node);
 354                         }
 355                 }
 356         }
 357         return (error);
 358 }
 359