2 * Copyright (c) 2007-2008 The DragonFly Project. All rights reserved.
4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@backplane.com>
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
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
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.
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
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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
34 * $DragonFly: src/sys/vfs/hammer/hammer_btree.c,v 1.76 2008/08/06 15:38:58 dillon Exp $
40 * HAMMER implements a modified B+Tree. In documentation this will
41 * simply be refered to as the HAMMER B-Tree. Basically a HAMMER B-Tree
42 * looks like a B+Tree (A B-Tree which stores its records only at the leafs
43 * of the tree), but adds two additional boundary elements which describe
44 * the left-most and right-most element a node is able to represent. In
45 * otherwords, we have boundary elements at the two ends of a B-Tree node
46 * instead of sub-tree pointers.
48 * A B-Tree internal node looks like this:
50 * B N N N N N N B <-- boundary and internal elements
51 * S S S S S S S <-- subtree pointers
53 * A B-Tree leaf node basically looks like this:
55 * L L L L L L L L <-- leaf elemenets
57 * The radix for an internal node is 1 less then a leaf but we get a
58 * number of significant benefits for our troubles.
60 * The big benefit to using a B-Tree containing boundary information
61 * is that it is possible to cache pointers into the middle of the tree
62 * and not have to start searches, insertions, OR deletions at the root
63 * node. In particular, searches are able to progress in a definitive
64 * direction from any point in the tree without revisting nodes. This
65 * greatly improves the efficiency of many operations, most especially
68 * B-Trees also make the stacking of trees fairly straightforward.
70 * INSERTIONS: A search performed with the intention of doing
71 * an insert will guarantee that the terminal leaf node is not full by
72 * splitting full nodes. Splits occur top-down during the dive down the
75 * DELETIONS: A deletion makes no attempt to proactively balance the
76 * tree and will recursively remove nodes that become empty. If a
77 * deadlock occurs a deletion may not be able to remove an empty leaf.
78 * Deletions never allow internal nodes to become empty (that would blow
85 static int btree_search(hammer_cursor_t cursor, int flags);
86 static int btree_split_internal(hammer_cursor_t cursor);
87 static int btree_split_leaf(hammer_cursor_t cursor);
88 static int btree_remove(hammer_cursor_t cursor);
89 static int btree_node_is_full(hammer_node_ondisk_t node);
90 static int hammer_btree_mirror_propagate(hammer_cursor_t cursor,
91 hammer_tid_t mirror_tid);
92 static void hammer_make_separator(hammer_base_elm_t key1,
93 hammer_base_elm_t key2, hammer_base_elm_t dest);
94 static void hammer_cursor_mirror_filter(hammer_cursor_t cursor);
97 * Iterate records after a search. The cursor is iterated forwards past
98 * the current record until a record matching the key-range requirements
99 * is found. ENOENT is returned if the iteration goes past the ending
102 * The iteration is inclusive of key_beg and can be inclusive or exclusive
103 * of key_end depending on whether HAMMER_CURSOR_END_INCLUSIVE is set.
105 * When doing an as-of search (cursor->asof != 0), key_beg.create_tid
106 * may be modified by B-Tree functions.
108 * cursor->key_beg may or may not be modified by this function during
109 * the iteration. XXX future - in case of an inverted lock we may have
110 * to reinitiate the lookup and set key_beg to properly pick up where we
113 * If HAMMER_CURSOR_ITERATE_CHECK is set it is possible that the cursor
114 * was reverse indexed due to being moved to a parent while unlocked,
115 * and something else might have inserted an element outside the iteration
116 * range. When this case occurs the iterator just keeps iterating until
117 * it gets back into the iteration range (instead of asserting).
119 * NOTE! EDEADLK *CANNOT* be returned by this procedure.
122 hammer_btree_iterate(hammer_cursor_t cursor)
124 hammer_node_ondisk_t node;
125 hammer_btree_elm_t elm;
132 * Skip past the current record
134 hmp = cursor->trans->hmp;
135 node = cursor->node->ondisk;
138 if (cursor->index < node->count &&
139 (cursor->flags & HAMMER_CURSOR_ATEDISK)) {
144 * HAMMER can wind up being cpu-bound.
146 if (++hmp->check_yield > hammer_yield_check) {
147 hmp->check_yield = 0;
153 * Loop until an element is found or we are done.
157 * We iterate up the tree and then index over one element
158 * while we are at the last element in the current node.
160 * If we are at the root of the filesystem, cursor_up
163 * XXX this could be optimized by storing the information in
164 * the parent reference.
166 * XXX we can lose the node lock temporarily, this could mess
169 ++hammer_stats_btree_iterations;
170 hammer_flusher_clean_loose_ios(hmp);
172 if (cursor->index == node->count) {
173 if (hammer_debug_btree) {
174 kprintf("BRACKETU %016llx[%d] -> %016llx[%d] (td=%p)\n",
175 (long long)cursor->node->node_offset,
177 (long long)(cursor->parent ? cursor->parent->node_offset : -1),
178 cursor->parent_index,
181 KKASSERT(cursor->parent == NULL || cursor->parent->ondisk->elms[cursor->parent_index].internal.subtree_offset == cursor->node->node_offset);
182 error = hammer_cursor_up(cursor);
185 /* reload stale pointer */
186 node = cursor->node->ondisk;
187 KKASSERT(cursor->index != node->count);
190 * If we are reblocking we want to return internal
191 * nodes. Note that the internal node will be
192 * returned multiple times, on each upward recursion
193 * from its children. The caller selects which
194 * revisit it cares about (usually first or last only).
196 if (cursor->flags & HAMMER_CURSOR_REBLOCKING) {
197 cursor->flags |= HAMMER_CURSOR_ATEDISK;
205 * Check internal or leaf element. Determine if the record
206 * at the cursor has gone beyond the end of our range.
208 * We recurse down through internal nodes.
210 if (node->type == HAMMER_BTREE_TYPE_INTERNAL) {
211 elm = &node->elms[cursor->index];
213 r = hammer_btree_cmp(&cursor->key_end, &elm[0].base);
214 s = hammer_btree_cmp(&cursor->key_beg, &elm[1].base);
215 if (hammer_debug_btree) {
216 kprintf("BRACKETL %016llx[%d] %016llx %02x %016llx lo=%02x %d (td=%p)\n",
217 (long long)cursor->node->node_offset,
219 (long long)elm[0].internal.base.obj_id,
220 elm[0].internal.base.rec_type,
221 (long long)elm[0].internal.base.key,
222 elm[0].internal.base.localization,
226 kprintf("BRACKETR %016llx[%d] %016llx %02x %016llx lo=%02x %d\n",
227 (long long)cursor->node->node_offset,
229 (long long)elm[1].internal.base.obj_id,
230 elm[1].internal.base.rec_type,
231 (long long)elm[1].internal.base.key,
232 elm[1].internal.base.localization,
241 if (r == 0 && (cursor->flags &
242 HAMMER_CURSOR_END_INCLUSIVE) == 0) {
250 KKASSERT(elm->internal.subtree_offset != 0);
254 * If running the mirror filter see if we
255 * can skip one or more entire sub-trees.
256 * If we can we return the internal node
257 * and the caller processes the skipped
258 * range (see mirror_read).
261 HAMMER_CURSOR_MIRROR_FILTERED) {
262 if (elm->internal.mirror_tid <
263 cursor->cmirror->mirror_tid) {
264 hammer_cursor_mirror_filter(cursor);
270 * Normally it would be impossible for the
271 * cursor to have gotten back-indexed,
272 * but it can happen if a node is deleted
273 * and the cursor is moved to its parent
274 * internal node. ITERATE_CHECK will be set.
276 KKASSERT(cursor->flags &
277 HAMMER_CURSOR_ITERATE_CHECK);
278 kprintf("hammer_btree_iterate: "
279 "DEBUG: Caught parent seek "
280 "in internal iteration\n");
283 error = hammer_cursor_down(cursor);
286 KKASSERT(cursor->index == 0);
287 /* reload stale pointer */
288 node = cursor->node->ondisk;
291 elm = &node->elms[cursor->index];
292 r = hammer_btree_cmp(&cursor->key_end, &elm->base);
293 if (hammer_debug_btree) {
294 kprintf("ELEMENT %016llx:%d %c %016llx %02x %016llx lo=%02x %d\n",
295 (long long)cursor->node->node_offset,
297 (elm[0].leaf.base.btype ?
298 elm[0].leaf.base.btype : '?'),
299 (long long)elm[0].leaf.base.obj_id,
300 elm[0].leaf.base.rec_type,
301 (long long)elm[0].leaf.base.key,
302 elm[0].leaf.base.localization,
312 * We support both end-inclusive and
313 * end-exclusive searches.
316 (cursor->flags & HAMMER_CURSOR_END_INCLUSIVE) == 0) {
322 * If ITERATE_CHECK is set an unlocked cursor may
323 * have been moved to a parent and the iterate can
324 * happen upon elements that are not in the requested
327 if (cursor->flags & HAMMER_CURSOR_ITERATE_CHECK) {
328 s = hammer_btree_cmp(&cursor->key_beg,
331 kprintf("hammer_btree_iterate: "
332 "DEBUG: Caught parent seek "
333 "in leaf iteration\n");
338 cursor->flags &= ~HAMMER_CURSOR_ITERATE_CHECK;
343 switch(elm->leaf.base.btype) {
344 case HAMMER_BTREE_TYPE_RECORD:
345 if ((cursor->flags & HAMMER_CURSOR_ASOF) &&
346 hammer_btree_chkts(cursor->asof, &elm->base)) {
360 * node pointer invalid after loop
366 if (hammer_debug_btree) {
367 int i = cursor->index;
368 hammer_btree_elm_t elm = &cursor->node->ondisk->elms[i];
369 kprintf("ITERATE %p:%d %016llx %02x %016llx lo=%02x\n",
371 (long long)elm->internal.base.obj_id,
372 elm->internal.base.rec_type,
373 (long long)elm->internal.base.key,
374 elm->internal.base.localization
383 * We hit an internal element that we could skip as part of a mirroring
384 * scan. Calculate the entire range being skipped.
386 * It is important to include any gaps between the parent's left_bound
387 * and the node's left_bound, and same goes for the right side.
390 hammer_cursor_mirror_filter(hammer_cursor_t cursor)
392 struct hammer_cmirror *cmirror;
393 hammer_node_ondisk_t ondisk;
394 hammer_btree_elm_t elm;
396 ondisk = cursor->node->ondisk;
397 cmirror = cursor->cmirror;
400 * Calculate the skipped range
402 elm = &ondisk->elms[cursor->index];
403 if (cursor->index == 0)
404 cmirror->skip_beg = *cursor->left_bound;
406 cmirror->skip_beg = elm->internal.base;
407 while (cursor->index < ondisk->count) {
408 if (elm->internal.mirror_tid >= cmirror->mirror_tid)
413 if (cursor->index == ondisk->count)
414 cmirror->skip_end = *cursor->right_bound;
416 cmirror->skip_end = elm->internal.base;
419 * clip the returned result.
421 if (hammer_btree_cmp(&cmirror->skip_beg, &cursor->key_beg) < 0)
422 cmirror->skip_beg = cursor->key_beg;
423 if (hammer_btree_cmp(&cmirror->skip_end, &cursor->key_end) > 0)
424 cmirror->skip_end = cursor->key_end;
428 * Iterate in the reverse direction. This is used by the pruning code to
429 * avoid overlapping records.
432 hammer_btree_iterate_reverse(hammer_cursor_t cursor)
434 hammer_node_ondisk_t node;
435 hammer_btree_elm_t elm;
441 /* mirror filtering not supported for reverse iteration */
442 KKASSERT ((cursor->flags & HAMMER_CURSOR_MIRROR_FILTERED) == 0);
445 * Skip past the current record. For various reasons the cursor
446 * may end up set to -1 or set to point at the end of the current
447 * node. These cases must be addressed.
449 node = cursor->node->ondisk;
452 if (cursor->index != -1 &&
453 (cursor->flags & HAMMER_CURSOR_ATEDISK)) {
456 if (cursor->index == cursor->node->ondisk->count)
460 * HAMMER can wind up being cpu-bound.
462 hmp = cursor->trans->hmp;
463 if (++hmp->check_yield > hammer_yield_check) {
464 hmp->check_yield = 0;
469 * Loop until an element is found or we are done.
472 ++hammer_stats_btree_iterations;
473 hammer_flusher_clean_loose_ios(hmp);
476 * We iterate up the tree and then index over one element
477 * while we are at the last element in the current node.
479 if (cursor->index == -1) {
480 error = hammer_cursor_up(cursor);
482 cursor->index = 0; /* sanity */
485 /* reload stale pointer */
486 node = cursor->node->ondisk;
487 KKASSERT(cursor->index != node->count);
493 * Check internal or leaf element. Determine if the record
494 * at the cursor has gone beyond the end of our range.
496 * We recurse down through internal nodes.
498 KKASSERT(cursor->index != node->count);
499 if (node->type == HAMMER_BTREE_TYPE_INTERNAL) {
500 elm = &node->elms[cursor->index];
501 r = hammer_btree_cmp(&cursor->key_end, &elm[0].base);
502 s = hammer_btree_cmp(&cursor->key_beg, &elm[1].base);
503 if (hammer_debug_btree) {
504 kprintf("BRACKETL %016llx[%d] %016llx %02x %016llx lo=%02x %d\n",
505 (long long)cursor->node->node_offset,
507 (long long)elm[0].internal.base.obj_id,
508 elm[0].internal.base.rec_type,
509 (long long)elm[0].internal.base.key,
510 elm[0].internal.base.localization,
513 kprintf("BRACKETR %016llx[%d] %016llx %02x %016llx lo=%02x %d\n",
514 (long long)cursor->node->node_offset,
516 (long long)elm[1].internal.base.obj_id,
517 elm[1].internal.base.rec_type,
518 (long long)elm[1].internal.base.key,
519 elm[1].internal.base.localization,
530 * It shouldn't be possible to be seeked past key_end,
531 * even if the cursor got moved to a parent.
538 KKASSERT(elm->internal.subtree_offset != 0);
540 error = hammer_cursor_down(cursor);
543 KKASSERT(cursor->index == 0);
544 /* reload stale pointer */
545 node = cursor->node->ondisk;
547 /* this can assign -1 if the leaf was empty */
548 cursor->index = node->count - 1;
551 elm = &node->elms[cursor->index];
552 s = hammer_btree_cmp(&cursor->key_beg, &elm->base);
553 if (hammer_debug_btree) {
554 kprintf("ELEMENT %016llx:%d %c %016llx %02x %016llx lo=%02x %d\n",
555 (long long)cursor->node->node_offset,
557 (elm[0].leaf.base.btype ?
558 elm[0].leaf.base.btype : '?'),
559 (long long)elm[0].leaf.base.obj_id,
560 elm[0].leaf.base.rec_type,
561 (long long)elm[0].leaf.base.key,
562 elm[0].leaf.base.localization,
572 * It shouldn't be possible to be seeked past key_end,
573 * even if the cursor got moved to a parent.
575 cursor->flags &= ~HAMMER_CURSOR_ITERATE_CHECK;
580 switch(elm->leaf.base.btype) {
581 case HAMMER_BTREE_TYPE_RECORD:
582 if ((cursor->flags & HAMMER_CURSOR_ASOF) &&
583 hammer_btree_chkts(cursor->asof, &elm->base)) {
597 * node pointer invalid after loop
603 if (hammer_debug_btree) {
604 int i = cursor->index;
605 hammer_btree_elm_t elm = &cursor->node->ondisk->elms[i];
606 kprintf("ITERATE %p:%d %016llx %02x %016llx lo=%02x\n",
608 (long long)elm->internal.base.obj_id,
609 elm->internal.base.rec_type,
610 (long long)elm->internal.base.key,
611 elm->internal.base.localization
620 * Lookup cursor->key_beg. 0 is returned on success, ENOENT if the entry
621 * could not be found, EDEADLK if inserting and a retry is needed, and a
622 * fatal error otherwise. When retrying, the caller must terminate the
623 * cursor and reinitialize it. EDEADLK cannot be returned if not inserting.
625 * The cursor is suitably positioned for a deletion on success, and suitably
626 * positioned for an insertion on ENOENT if HAMMER_CURSOR_INSERT was
629 * The cursor may begin anywhere, the search will traverse the tree in
630 * either direction to locate the requested element.
632 * Most of the logic implementing historical searches is handled here. We
633 * do an initial lookup with create_tid set to the asof TID. Due to the
634 * way records are laid out, a backwards iteration may be required if
635 * ENOENT is returned to locate the historical record. Here's the
638 * create_tid: 10 15 20
642 * Lets say we want to do a lookup AS-OF timestamp 17. We will traverse
643 * LEAF2 but the only record in LEAF2 has a create_tid of 18, which is
644 * not visible and thus causes ENOENT to be returned. We really need
645 * to check record 11 in LEAF1. If it also fails then the search fails
646 * (e.g. it might represent the range 11-16 and thus still not match our
647 * AS-OF timestamp of 17). Note that LEAF1 could be empty, requiring
648 * further iterations.
650 * If this case occurs btree_search() will set HAMMER_CURSOR_CREATE_CHECK
651 * and the cursor->create_check TID if an iteration might be needed.
652 * In the above example create_check would be set to 14.
655 hammer_btree_lookup(hammer_cursor_t cursor)
659 cursor->flags &= ~HAMMER_CURSOR_ITERATE_CHECK;
660 KKASSERT ((cursor->flags & HAMMER_CURSOR_INSERT) == 0 ||
661 cursor->trans->sync_lock_refs > 0);
662 ++hammer_stats_btree_lookups;
663 if (cursor->flags & HAMMER_CURSOR_ASOF) {
664 KKASSERT((cursor->flags & HAMMER_CURSOR_INSERT) == 0);
665 cursor->key_beg.create_tid = cursor->asof;
667 cursor->flags &= ~HAMMER_CURSOR_CREATE_CHECK;
668 error = btree_search(cursor, 0);
669 if (error != ENOENT ||
670 (cursor->flags & HAMMER_CURSOR_CREATE_CHECK) == 0) {
673 * Stop if error other then ENOENT.
674 * Stop if ENOENT and not special case.
678 if (hammer_debug_btree) {
679 kprintf("CREATE_CHECK %016llx\n",
680 (long long)cursor->create_check);
682 cursor->key_beg.create_tid = cursor->create_check;
686 error = btree_search(cursor, 0);
689 error = hammer_btree_extract(cursor, cursor->flags);
694 * Execute the logic required to start an iteration. The first record
695 * located within the specified range is returned and iteration control
696 * flags are adjusted for successive hammer_btree_iterate() calls.
698 * Set ATEDISK so a low-level caller can call btree_first/btree_iterate
699 * in a loop without worrying about it. Higher-level merged searches will
700 * adjust the flag appropriately.
703 hammer_btree_first(hammer_cursor_t cursor)
707 error = hammer_btree_lookup(cursor);
708 if (error == ENOENT) {
709 cursor->flags &= ~HAMMER_CURSOR_ATEDISK;
710 error = hammer_btree_iterate(cursor);
712 cursor->flags |= HAMMER_CURSOR_ATEDISK;
717 * Similarly but for an iteration in the reverse direction.
719 * Set ATEDISK when iterating backwards to skip the current entry,
720 * which after an ENOENT lookup will be pointing beyond our end point.
722 * Set ATEDISK so a low-level caller can call btree_last/btree_iterate_reverse
723 * in a loop without worrying about it. Higher-level merged searches will
724 * adjust the flag appropriately.
727 hammer_btree_last(hammer_cursor_t cursor)
729 struct hammer_base_elm save;
732 save = cursor->key_beg;
733 cursor->key_beg = cursor->key_end;
734 error = hammer_btree_lookup(cursor);
735 cursor->key_beg = save;
736 if (error == ENOENT ||
737 (cursor->flags & HAMMER_CURSOR_END_INCLUSIVE) == 0) {
738 cursor->flags |= HAMMER_CURSOR_ATEDISK;
739 error = hammer_btree_iterate_reverse(cursor);
741 cursor->flags |= HAMMER_CURSOR_ATEDISK;
746 * Extract the record and/or data associated with the cursor's current
747 * position. Any prior record or data stored in the cursor is replaced.
748 * The cursor must be positioned at a leaf node.
750 * NOTE: All extractions occur at the leaf of the B-Tree.
753 hammer_btree_extract(hammer_cursor_t cursor, int flags)
755 hammer_node_ondisk_t node;
756 hammer_btree_elm_t elm;
757 hammer_off_t data_off;
763 * The case where the data reference resolves to the same buffer
764 * as the record reference must be handled.
766 node = cursor->node->ondisk;
767 elm = &node->elms[cursor->index];
769 hmp = cursor->node->hmp;
772 * There is nothing to extract for an internal element.
774 if (node->type == HAMMER_BTREE_TYPE_INTERNAL)
778 * Only record types have data.
780 KKASSERT(node->type == HAMMER_BTREE_TYPE_LEAF);
781 cursor->leaf = &elm->leaf;
783 if ((flags & HAMMER_CURSOR_GET_DATA) == 0)
785 if (elm->leaf.base.btype != HAMMER_BTREE_TYPE_RECORD)
787 data_off = elm->leaf.data_offset;
788 data_len = elm->leaf.data_len;
795 KKASSERT(data_len >= 0 && data_len <= HAMMER_XBUFSIZE);
796 cursor->data = hammer_bread_ext(hmp, data_off, data_len,
797 &error, &cursor->data_buffer);
800 * Mark the data buffer as not being meta-data if it isn't
801 * meta-data (sometimes bulk data is accessed via a volume
805 switch(elm->leaf.base.rec_type) {
806 case HAMMER_RECTYPE_DATA:
807 case HAMMER_RECTYPE_DB:
808 if ((data_off & HAMMER_ZONE_LARGE_DATA) == 0)
810 if (hammer_double_buffer == 0 ||
811 (cursor->flags & HAMMER_CURSOR_NOSWAPCACHE)) {
812 hammer_io_notmeta(cursor->data_buffer);
821 * Deal with CRC errors on the extracted data.
824 hammer_crc_test_leaf(cursor->data, &elm->leaf) == 0) {
825 kprintf("CRC DATA @ %016llx/%d FAILED\n",
826 (long long)elm->leaf.data_offset, elm->leaf.data_len);
827 if (hammer_debug_critical)
828 Debugger("CRC FAILED: DATA");
829 if (cursor->trans->flags & HAMMER_TRANSF_CRCDOM)
830 error = EDOM; /* less critical (mirroring) */
832 error = EIO; /* critical */
839 * Insert a leaf element into the B-Tree at the current cursor position.
840 * The cursor is positioned such that the element at and beyond the cursor
841 * are shifted to make room for the new record.
843 * The caller must call hammer_btree_lookup() with the HAMMER_CURSOR_INSERT
844 * flag set and that call must return ENOENT before this function can be
847 * The caller may depend on the cursor's exclusive lock after return to
848 * interlock frontend visibility (see HAMMER_RECF_CONVERT_DELETE).
850 * ENOSPC is returned if there is no room to insert a new record.
853 hammer_btree_insert(hammer_cursor_t cursor, hammer_btree_leaf_elm_t elm,
856 hammer_node_ondisk_t node;
861 if ((error = hammer_cursor_upgrade_node(cursor)) != 0)
863 ++hammer_stats_btree_inserts;
866 * Insert the element at the leaf node and update the count in the
867 * parent. It is possible for parent to be NULL, indicating that
868 * the filesystem's ROOT B-Tree node is a leaf itself, which is
869 * possible. The root inode can never be deleted so the leaf should
872 * Remember that the right-hand boundary is not included in the
875 hammer_modify_node_all(cursor->trans, cursor->node);
876 node = cursor->node->ondisk;
878 KKASSERT(elm->base.btype != 0);
879 KKASSERT(node->type == HAMMER_BTREE_TYPE_LEAF);
880 KKASSERT(node->count < HAMMER_BTREE_LEAF_ELMS);
881 if (i != node->count) {
882 bcopy(&node->elms[i], &node->elms[i+1],
883 (node->count - i) * sizeof(*elm));
885 node->elms[i].leaf = *elm;
887 hammer_cursor_inserted_element(cursor->node, i);
890 * Update the leaf node's aggregate mirror_tid for mirroring
893 if (node->mirror_tid < elm->base.delete_tid) {
894 node->mirror_tid = elm->base.delete_tid;
897 if (node->mirror_tid < elm->base.create_tid) {
898 node->mirror_tid = elm->base.create_tid;
901 hammer_modify_node_done(cursor->node);
904 * Debugging sanity checks.
906 KKASSERT(hammer_btree_cmp(cursor->left_bound, &elm->base) <= 0);
907 KKASSERT(hammer_btree_cmp(cursor->right_bound, &elm->base) > 0);
909 KKASSERT(hammer_btree_cmp(&node->elms[i-1].leaf.base, &elm->base) < 0);
911 if (i != node->count - 1)
912 KKASSERT(hammer_btree_cmp(&node->elms[i+1].leaf.base, &elm->base) > 0);
918 * Delete a record from the B-Tree at the current cursor position.
919 * The cursor is positioned such that the current element is the one
922 * On return the cursor will be positioned after the deleted element and
923 * MAY point to an internal node. It will be suitable for the continuation
924 * of an iteration but not for an insertion or deletion.
926 * Deletions will attempt to partially rebalance the B-Tree in an upward
927 * direction, but will terminate rather then deadlock. Empty internal nodes
928 * are never allowed by a deletion which deadlocks may end up giving us an
929 * empty leaf. The pruner will clean up and rebalance the tree.
931 * This function can return EDEADLK, requiring the caller to retry the
932 * operation after clearing the deadlock.
935 hammer_btree_delete(hammer_cursor_t cursor)
937 hammer_node_ondisk_t ondisk;
939 hammer_node_t parent;
943 KKASSERT (cursor->trans->sync_lock_refs > 0);
944 if ((error = hammer_cursor_upgrade(cursor)) != 0)
946 ++hammer_stats_btree_deletes;
949 * Delete the element from the leaf node.
951 * Remember that leaf nodes do not have boundaries.
954 ondisk = node->ondisk;
957 KKASSERT(ondisk->type == HAMMER_BTREE_TYPE_LEAF);
958 KKASSERT(i >= 0 && i < ondisk->count);
959 hammer_modify_node_all(cursor->trans, node);
960 if (i + 1 != ondisk->count) {
961 bcopy(&ondisk->elms[i+1], &ondisk->elms[i],
962 (ondisk->count - i - 1) * sizeof(ondisk->elms[0]));
965 hammer_modify_node_done(node);
966 hammer_cursor_deleted_element(node, i);
969 * Validate local parent
971 if (ondisk->parent) {
972 parent = cursor->parent;
974 KKASSERT(parent != NULL);
975 KKASSERT(parent->node_offset == ondisk->parent);
979 * If the leaf becomes empty it must be detached from the parent,
980 * potentially recursing through to the filesystem root.
982 * This may reposition the cursor at one of the parent's of the
985 * Ignore deadlock errors, that simply means that btree_remove
986 * was unable to recurse and had to leave us with an empty leaf.
988 KKASSERT(cursor->index <= ondisk->count);
989 if (ondisk->count == 0) {
990 error = btree_remove(cursor);
991 if (error == EDEADLK)
996 KKASSERT(cursor->parent == NULL ||
997 cursor->parent_index < cursor->parent->ondisk->count);
1002 * PRIMAY B-TREE SEARCH SUPPORT PROCEDURE
1004 * Search the filesystem B-Tree for cursor->key_beg, return the matching node.
1006 * The search can begin ANYWHERE in the B-Tree. As a first step the search
1007 * iterates up the tree as necessary to properly position itself prior to
1008 * actually doing the sarch.
1010 * INSERTIONS: The search will split full nodes and leaves on its way down
1011 * and guarentee that the leaf it ends up on is not full. If we run out
1012 * of space the search continues to the leaf (to position the cursor for
1013 * the spike), but ENOSPC is returned.
1015 * The search is only guarenteed to end up on a leaf if an error code of 0
1016 * is returned, or if inserting and an error code of ENOENT is returned.
1017 * Otherwise it can stop at an internal node. On success a search returns
1020 * COMPLEXITY WARNING! This is the core B-Tree search code for the entire
1021 * filesystem, and it is not simple code. Please note the following facts:
1023 * - Internal node recursions have a boundary on the left AND right. The
1024 * right boundary is non-inclusive. The create_tid is a generic part
1025 * of the key for internal nodes.
1027 * - Leaf nodes contain terminal elements only now.
1029 * - Filesystem lookups typically set HAMMER_CURSOR_ASOF, indicating a
1030 * historical search. ASOF and INSERT are mutually exclusive. When
1031 * doing an as-of lookup btree_search() checks for a right-edge boundary
1032 * case. If while recursing down the left-edge differs from the key
1033 * by ONLY its create_tid, HAMMER_CURSOR_CREATE_CHECK is set along
1034 * with cursor->create_check. This is used by btree_lookup() to iterate.
1035 * The iteration backwards because as-of searches can wind up going
1036 * down the wrong branch of the B-Tree.
1040 btree_search(hammer_cursor_t cursor, int flags)
1042 hammer_node_ondisk_t node;
1043 hammer_btree_elm_t elm;
1050 flags |= cursor->flags;
1051 ++hammer_stats_btree_searches;
1053 if (hammer_debug_btree) {
1054 kprintf("SEARCH %016llx[%d] %016llx %02x key=%016llx cre=%016llx lo=%02x (td = %p)\n",
1055 (long long)cursor->node->node_offset,
1057 (long long)cursor->key_beg.obj_id,
1058 cursor->key_beg.rec_type,
1059 (long long)cursor->key_beg.key,
1060 (long long)cursor->key_beg.create_tid,
1061 cursor->key_beg.localization,
1065 kprintf("SEARCHP %016llx[%d] (%016llx/%016llx %016llx/%016llx) (%p/%p %p/%p)\n",
1066 (long long)cursor->parent->node_offset,
1067 cursor->parent_index,
1068 (long long)cursor->left_bound->obj_id,
1069 (long long)cursor->parent->ondisk->elms[cursor->parent_index].internal.base.obj_id,
1070 (long long)cursor->right_bound->obj_id,
1071 (long long)cursor->parent->ondisk->elms[cursor->parent_index+1].internal.base.obj_id,
1073 &cursor->parent->ondisk->elms[cursor->parent_index],
1074 cursor->right_bound,
1075 &cursor->parent->ondisk->elms[cursor->parent_index+1]
1080 * Move our cursor up the tree until we find a node whos range covers
1081 * the key we are trying to locate.
1083 * The left bound is inclusive, the right bound is non-inclusive.
1084 * It is ok to cursor up too far.
1087 r = hammer_btree_cmp(&cursor->key_beg, cursor->left_bound);
1088 s = hammer_btree_cmp(&cursor->key_beg, cursor->right_bound);
1089 if (r >= 0 && s < 0)
1091 KKASSERT(cursor->parent);
1092 ++hammer_stats_btree_iterations;
1093 error = hammer_cursor_up(cursor);
1099 * The delete-checks below are based on node, not parent. Set the
1100 * initial delete-check based on the parent.
1103 KKASSERT(cursor->left_bound->create_tid != 1);
1104 cursor->create_check = cursor->left_bound->create_tid - 1;
1105 cursor->flags |= HAMMER_CURSOR_CREATE_CHECK;
1109 * We better have ended up with a node somewhere.
1111 KKASSERT(cursor->node != NULL);
1114 * If we are inserting we can't start at a full node if the parent
1115 * is also full (because there is no way to split the node),
1116 * continue running up the tree until the requirement is satisfied
1117 * or we hit the root of the filesystem.
1119 * (If inserting we aren't doing an as-of search so we don't have
1120 * to worry about create_check).
1122 while ((flags & HAMMER_CURSOR_INSERT) && enospc == 0) {
1123 if (cursor->node->ondisk->type == HAMMER_BTREE_TYPE_INTERNAL) {
1124 if (btree_node_is_full(cursor->node->ondisk) == 0)
1127 if (btree_node_is_full(cursor->node->ondisk) ==0)
1130 if (cursor->node->ondisk->parent == 0 ||
1131 cursor->parent->ondisk->count != HAMMER_BTREE_INT_ELMS) {
1134 ++hammer_stats_btree_iterations;
1135 error = hammer_cursor_up(cursor);
1136 /* node may have become stale */
1142 * Push down through internal nodes to locate the requested key.
1144 node = cursor->node->ondisk;
1145 while (node->type == HAMMER_BTREE_TYPE_INTERNAL) {
1147 * Scan the node to find the subtree index to push down into.
1148 * We go one-past, then back-up.
1150 * We must proactively remove deleted elements which may
1151 * have been left over from a deadlocked btree_remove().
1153 * The left and right boundaries are included in the loop
1154 * in order to detect edge cases.
1156 * If the separator only differs by create_tid (r == 1)
1157 * and we are doing an as-of search, we may end up going
1158 * down a branch to the left of the one containing the
1159 * desired key. This requires numerous special cases.
1161 ++hammer_stats_btree_iterations;
1162 if (hammer_debug_btree) {
1163 kprintf("SEARCH-I %016llx count=%d\n",
1164 (long long)cursor->node->node_offset,
1169 * Try to shortcut the search before dropping into the
1170 * linear loop. Locate the first node where r <= 1.
1172 i = hammer_btree_search_node(&cursor->key_beg, node);
1173 while (i <= node->count) {
1174 ++hammer_stats_btree_elements;
1175 elm = &node->elms[i];
1176 r = hammer_btree_cmp(&cursor->key_beg, &elm->base);
1177 if (hammer_debug_btree > 2) {
1178 kprintf(" IELM %p %d r=%d\n",
1179 &node->elms[i], i, r);
1184 KKASSERT(elm->base.create_tid != 1);
1185 cursor->create_check = elm->base.create_tid - 1;
1186 cursor->flags |= HAMMER_CURSOR_CREATE_CHECK;
1190 if (hammer_debug_btree) {
1191 kprintf("SEARCH-I preI=%d/%d r=%d\n",
1196 * These cases occur when the parent's idea of the boundary
1197 * is wider then the child's idea of the boundary, and
1198 * require special handling. If not inserting we can
1199 * terminate the search early for these cases but the
1200 * child's boundaries cannot be unconditionally modified.
1204 * If i == 0 the search terminated to the LEFT of the
1205 * left_boundary but to the RIGHT of the parent's left
1210 elm = &node->elms[0];
1213 * If we aren't inserting we can stop here.
1215 if ((flags & (HAMMER_CURSOR_INSERT |
1216 HAMMER_CURSOR_PRUNING)) == 0) {
1222 * Correct a left-hand boundary mismatch.
1224 * We can only do this if we can upgrade the lock,
1225 * and synchronized as a background cursor (i.e.
1226 * inserting or pruning).
1228 * WARNING: We can only do this if inserting, i.e.
1229 * we are running on the backend.
1231 if ((error = hammer_cursor_upgrade(cursor)) != 0)
1233 KKASSERT(cursor->flags & HAMMER_CURSOR_BACKEND);
1234 hammer_modify_node_field(cursor->trans, cursor->node,
1236 save = node->elms[0].base.btype;
1237 node->elms[0].base = *cursor->left_bound;
1238 node->elms[0].base.btype = save;
1239 hammer_modify_node_done(cursor->node);
1240 } else if (i == node->count + 1) {
1242 * If i == node->count + 1 the search terminated to
1243 * the RIGHT of the right boundary but to the LEFT
1244 * of the parent's right boundary. If we aren't
1245 * inserting we can stop here.
1247 * Note that the last element in this case is
1248 * elms[i-2] prior to adjustments to 'i'.
1251 if ((flags & (HAMMER_CURSOR_INSERT |
1252 HAMMER_CURSOR_PRUNING)) == 0) {
1258 * Correct a right-hand boundary mismatch.
1259 * (actual push-down record is i-2 prior to
1260 * adjustments to i).
1262 * We can only do this if we can upgrade the lock,
1263 * and synchronized as a background cursor (i.e.
1264 * inserting or pruning).
1266 * WARNING: We can only do this if inserting, i.e.
1267 * we are running on the backend.
1269 if ((error = hammer_cursor_upgrade(cursor)) != 0)
1271 elm = &node->elms[i];
1272 KKASSERT(cursor->flags & HAMMER_CURSOR_BACKEND);
1273 hammer_modify_node(cursor->trans, cursor->node,
1274 &elm->base, sizeof(elm->base));
1275 elm->base = *cursor->right_bound;
1276 hammer_modify_node_done(cursor->node);
1280 * The push-down index is now i - 1. If we had
1281 * terminated on the right boundary this will point
1282 * us at the last element.
1287 elm = &node->elms[i];
1289 if (hammer_debug_btree) {
1290 kprintf("RESULT-I %016llx[%d] %016llx %02x "
1291 "key=%016llx cre=%016llx lo=%02x\n",
1292 (long long)cursor->node->node_offset,
1294 (long long)elm->internal.base.obj_id,
1295 elm->internal.base.rec_type,
1296 (long long)elm->internal.base.key,
1297 (long long)elm->internal.base.create_tid,
1298 elm->internal.base.localization
1303 * We better have a valid subtree offset.
1305 KKASSERT(elm->internal.subtree_offset != 0);
1308 * Handle insertion and deletion requirements.
1310 * If inserting split full nodes. The split code will
1311 * adjust cursor->node and cursor->index if the current
1312 * index winds up in the new node.
1314 * If inserting and a left or right edge case was detected,
1315 * we cannot correct the left or right boundary and must
1316 * prepend and append an empty leaf node in order to make
1317 * the boundary correction.
1319 * If we run out of space we set enospc and continue on
1320 * to a leaf to provide the spike code with a good point
1323 if ((flags & HAMMER_CURSOR_INSERT) && enospc == 0) {
1324 if (btree_node_is_full(node)) {
1325 error = btree_split_internal(cursor);
1327 if (error != ENOSPC)
1332 * reload stale pointers
1335 node = cursor->node->ondisk;
1340 * Push down (push into new node, existing node becomes
1341 * the parent) and continue the search.
1343 error = hammer_cursor_down(cursor);
1344 /* node may have become stale */
1347 node = cursor->node->ondisk;
1351 * We are at a leaf, do a linear search of the key array.
1353 * On success the index is set to the matching element and 0
1356 * On failure the index is set to the insertion point and ENOENT
1359 * Boundaries are not stored in leaf nodes, so the index can wind
1360 * up to the left of element 0 (index == 0) or past the end of
1361 * the array (index == node->count). It is also possible that the
1362 * leaf might be empty.
1364 ++hammer_stats_btree_iterations;
1365 KKASSERT (node->type == HAMMER_BTREE_TYPE_LEAF);
1366 KKASSERT(node->count <= HAMMER_BTREE_LEAF_ELMS);
1367 if (hammer_debug_btree) {
1368 kprintf("SEARCH-L %016llx count=%d\n",
1369 (long long)cursor->node->node_offset,
1374 * Try to shortcut the search before dropping into the
1375 * linear loop. Locate the first node where r <= 1.
1377 i = hammer_btree_search_node(&cursor->key_beg, node);
1378 while (i < node->count) {
1379 ++hammer_stats_btree_elements;
1380 elm = &node->elms[i];
1382 r = hammer_btree_cmp(&cursor->key_beg, &elm->leaf.base);
1384 if (hammer_debug_btree > 1)
1385 kprintf(" ELM %p %d r=%d\n", &node->elms[i], i, r);
1388 * We are at a record element. Stop if we've flipped past
1389 * key_beg, not counting the create_tid test. Allow the
1390 * r == 1 case (key_beg > element but differs only by its
1391 * create_tid) to fall through to the AS-OF check.
1393 KKASSERT (elm->leaf.base.btype == HAMMER_BTREE_TYPE_RECORD);
1403 * Check our as-of timestamp against the element.
1405 if (flags & HAMMER_CURSOR_ASOF) {
1406 if (hammer_btree_chkts(cursor->asof,
1407 &node->elms[i].base) != 0) {
1413 if (r > 0) { /* can only be +1 */
1421 if (hammer_debug_btree) {
1422 kprintf("RESULT-L %016llx[%d] (SUCCESS)\n",
1423 (long long)cursor->node->node_offset, i);
1429 * The search of the leaf node failed. i is the insertion point.
1432 if (hammer_debug_btree) {
1433 kprintf("RESULT-L %016llx[%d] (FAILED)\n",
1434 (long long)cursor->node->node_offset, i);
1438 * No exact match was found, i is now at the insertion point.
1440 * If inserting split a full leaf before returning. This
1441 * may have the side effect of adjusting cursor->node and
1445 if ((flags & HAMMER_CURSOR_INSERT) && enospc == 0 &&
1446 btree_node_is_full(node)) {
1447 error = btree_split_leaf(cursor);
1449 if (error != ENOSPC)
1454 * reload stale pointers
1458 node = &cursor->node->internal;
1463 * We reached a leaf but did not find the key we were looking for.
1464 * If this is an insert we will be properly positioned for an insert
1465 * (ENOENT) or spike (ENOSPC) operation.
1467 error = enospc ? ENOSPC : ENOENT;
1473 * Heuristical search for the first element whos comparison is <= 1. May
1474 * return an index whos compare result is > 1 but may only return an index
1475 * whos compare result is <= 1 if it is the first element with that result.
1478 hammer_btree_search_node(hammer_base_elm_t elm, hammer_node_ondisk_t node)
1486 * Don't bother if the node does not have very many elements
1491 i = b + (s - b) / 2;
1492 ++hammer_stats_btree_elements;
1493 r = hammer_btree_cmp(elm, &node->elms[i].leaf.base);
1504 /************************************************************************
1505 * SPLITTING AND MERGING *
1506 ************************************************************************
1508 * These routines do all the dirty work required to split and merge nodes.
1512 * Split an internal node into two nodes and move the separator at the split
1513 * point to the parent.
1515 * (cursor->node, cursor->index) indicates the element the caller intends
1516 * to push into. We will adjust node and index if that element winds
1517 * up in the split node.
1519 * If we are at the root of the filesystem a new root must be created with
1520 * two elements, one pointing to the original root and one pointing to the
1521 * newly allocated split node.
1525 btree_split_internal(hammer_cursor_t cursor)
1527 hammer_node_ondisk_t ondisk;
1529 hammer_node_t parent;
1530 hammer_node_t new_node;
1531 hammer_btree_elm_t elm;
1532 hammer_btree_elm_t parent_elm;
1533 struct hammer_node_lock lockroot;
1534 hammer_mount_t hmp = cursor->trans->hmp;
1541 const int esize = sizeof(*elm);
1543 hammer_node_lock_init(&lockroot, cursor->node);
1544 error = hammer_btree_lock_children(cursor, 1, &lockroot, NULL);
1547 if ((error = hammer_cursor_upgrade(cursor)) != 0)
1549 ++hammer_stats_btree_splits;
1552 * Calculate the split point. If the insertion point is at the
1553 * end of the leaf we adjust the split point significantly to the
1554 * right to try to optimize node fill and flag it. If we hit
1555 * that same leaf again our heuristic failed and we don't try
1556 * to optimize node fill (it could lead to a degenerate case).
1558 node = cursor->node;
1559 ondisk = node->ondisk;
1560 KKASSERT(ondisk->count > 4);
1561 if (cursor->index == ondisk->count &&
1562 (node->flags & HAMMER_NODE_NONLINEAR) == 0) {
1563 split = (ondisk->count + 1) * 3 / 4;
1564 node->flags |= HAMMER_NODE_NONLINEAR;
1567 * We are splitting but elms[split] will be promoted to
1568 * the parent, leaving the right hand node with one less
1569 * element. If the insertion point will be on the
1570 * left-hand side adjust the split point to give the
1571 * right hand side one additional node.
1573 split = (ondisk->count + 1) / 2;
1574 if (cursor->index <= split)
1579 * If we are at the root of the filesystem, create a new root node
1580 * with 1 element and split normally. Avoid making major
1581 * modifications until we know the whole operation will work.
1583 if (ondisk->parent == 0) {
1584 parent = hammer_alloc_btree(cursor->trans, 0, &error);
1587 hammer_lock_ex(&parent->lock);
1588 hammer_modify_node_noundo(cursor->trans, parent);
1589 ondisk = parent->ondisk;
1592 ondisk->mirror_tid = node->ondisk->mirror_tid;
1593 ondisk->type = HAMMER_BTREE_TYPE_INTERNAL;
1594 ondisk->elms[0].base = hmp->root_btree_beg;
1595 ondisk->elms[0].base.btype = node->ondisk->type;
1596 ondisk->elms[0].internal.subtree_offset = node->node_offset;
1597 ondisk->elms[1].base = hmp->root_btree_end;
1598 hammer_modify_node_done(parent);
1599 /* ondisk->elms[1].base.btype - not used */
1601 parent_index = 0; /* index of current node in parent */
1604 parent = cursor->parent;
1605 parent_index = cursor->parent_index;
1609 * Calculate a hint for the allocation of the new B-Tree node.
1610 * The most likely expansion is coming from the insertion point
1611 * at cursor->index, so try to localize the allocation of our
1612 * new node to accomodate that sub-tree.
1614 * Use the right-most sub-tree when expandinging on the right edge.
1615 * This is a very common case when copying a directory tree.
1617 if (cursor->index == ondisk->count)
1618 hint = ondisk->elms[cursor->index - 1].internal.subtree_offset;
1620 hint = ondisk->elms[cursor->index].internal.subtree_offset;
1623 * Split node into new_node at the split point.
1625 * B O O O P N N B <-- P = node->elms[split] (index 4)
1626 * 0 1 2 3 4 5 6 <-- subtree indices
1631 * B O O O B B N N B <--- inner boundary points are 'P'
1634 new_node = hammer_alloc_btree(cursor->trans, 0, &error);
1635 if (new_node == NULL) {
1637 hammer_unlock(&parent->lock);
1638 hammer_delete_node(cursor->trans, parent);
1639 hammer_rel_node(parent);
1643 hammer_lock_ex(&new_node->lock);
1646 * Create the new node. P becomes the left-hand boundary in the
1647 * new node. Copy the right-hand boundary as well.
1649 * elm is the new separator.
1651 hammer_modify_node_noundo(cursor->trans, new_node);
1652 hammer_modify_node_all(cursor->trans, node);
1653 ondisk = node->ondisk;
1654 elm = &ondisk->elms[split];
1655 bcopy(elm, &new_node->ondisk->elms[0],
1656 (ondisk->count - split + 1) * esize);
1657 new_node->ondisk->count = ondisk->count - split;
1658 new_node->ondisk->parent = parent->node_offset;
1659 new_node->ondisk->type = HAMMER_BTREE_TYPE_INTERNAL;
1660 new_node->ondisk->mirror_tid = ondisk->mirror_tid;
1661 KKASSERT(ondisk->type == new_node->ondisk->type);
1662 hammer_cursor_split_node(node, new_node, split);
1665 * Cleanup the original node. Elm (P) becomes the new boundary,
1666 * its subtree_offset was moved to the new node. If we had created
1667 * a new root its parent pointer may have changed.
1669 elm->internal.subtree_offset = 0;
1670 ondisk->count = split;
1673 * Insert the separator into the parent, fixup the parent's
1674 * reference to the original node, and reference the new node.
1675 * The separator is P.
1677 * Remember that base.count does not include the right-hand boundary.
1679 hammer_modify_node_all(cursor->trans, parent);
1680 ondisk = parent->ondisk;
1681 KKASSERT(ondisk->count != HAMMER_BTREE_INT_ELMS);
1682 parent_elm = &ondisk->elms[parent_index+1];
1683 bcopy(parent_elm, parent_elm + 1,
1684 (ondisk->count - parent_index) * esize);
1685 parent_elm->internal.base = elm->base; /* separator P */
1686 parent_elm->internal.base.btype = new_node->ondisk->type;
1687 parent_elm->internal.subtree_offset = new_node->node_offset;
1688 parent_elm->internal.mirror_tid = new_node->ondisk->mirror_tid;
1690 hammer_modify_node_done(parent);
1691 hammer_cursor_inserted_element(parent, parent_index + 1);
1694 * The children of new_node need their parent pointer set to new_node.
1695 * The children have already been locked by
1696 * hammer_btree_lock_children().
1698 for (i = 0; i < new_node->ondisk->count; ++i) {
1699 elm = &new_node->ondisk->elms[i];
1700 error = btree_set_parent(cursor->trans, new_node, elm);
1702 panic("btree_split_internal: btree-fixup problem");
1705 hammer_modify_node_done(new_node);
1708 * The filesystem's root B-Tree pointer may have to be updated.
1711 hammer_volume_t volume;
1713 volume = hammer_get_root_volume(hmp, &error);
1714 KKASSERT(error == 0);
1716 hammer_modify_volume_field(cursor->trans, volume,
1718 volume->ondisk->vol0_btree_root = parent->node_offset;
1719 hammer_modify_volume_done(volume);
1720 node->ondisk->parent = parent->node_offset;
1721 if (cursor->parent) {
1722 hammer_unlock(&cursor->parent->lock);
1723 hammer_rel_node(cursor->parent);
1725 cursor->parent = parent; /* lock'd and ref'd */
1726 hammer_rel_volume(volume, 0);
1728 hammer_modify_node_done(node);
1731 * Ok, now adjust the cursor depending on which element the original
1732 * index was pointing at. If we are >= the split point the push node
1733 * is now in the new node.
1735 * NOTE: If we are at the split point itself we cannot stay with the
1736 * original node because the push index will point at the right-hand
1737 * boundary, which is illegal.
1739 * NOTE: The cursor's parent or parent_index must be adjusted for
1740 * the case where a new parent (new root) was created, and the case
1741 * where the cursor is now pointing at the split node.
1743 if (cursor->index >= split) {
1744 cursor->parent_index = parent_index + 1;
1745 cursor->index -= split;
1746 hammer_unlock(&cursor->node->lock);
1747 hammer_rel_node(cursor->node);
1748 cursor->node = new_node; /* locked and ref'd */
1750 cursor->parent_index = parent_index;
1751 hammer_unlock(&new_node->lock);
1752 hammer_rel_node(new_node);
1756 * Fixup left and right bounds
1758 parent_elm = &parent->ondisk->elms[cursor->parent_index];
1759 cursor->left_bound = &parent_elm[0].internal.base;
1760 cursor->right_bound = &parent_elm[1].internal.base;
1761 KKASSERT(hammer_btree_cmp(cursor->left_bound,
1762 &cursor->node->ondisk->elms[0].internal.base) <= 0);
1763 KKASSERT(hammer_btree_cmp(cursor->right_bound,
1764 &cursor->node->ondisk->elms[cursor->node->ondisk->count].internal.base) >= 0);
1767 hammer_btree_unlock_children(cursor->trans->hmp, &lockroot, NULL);
1768 hammer_cursor_downgrade(cursor);
1773 * Same as the above, but splits a full leaf node.
1779 btree_split_leaf(hammer_cursor_t cursor)
1781 hammer_node_ondisk_t ondisk;
1782 hammer_node_t parent;
1785 hammer_node_t new_leaf;
1786 hammer_btree_elm_t elm;
1787 hammer_btree_elm_t parent_elm;
1788 hammer_base_elm_t mid_boundary;
1794 const size_t esize = sizeof(*elm);
1796 if ((error = hammer_cursor_upgrade(cursor)) != 0)
1798 ++hammer_stats_btree_splits;
1800 KKASSERT(hammer_btree_cmp(cursor->left_bound,
1801 &cursor->node->ondisk->elms[0].leaf.base) <= 0);
1802 KKASSERT(hammer_btree_cmp(cursor->right_bound,
1803 &cursor->node->ondisk->elms[cursor->node->ondisk->count-1].leaf.base) > 0);
1806 * Calculate the split point. If the insertion point is at the
1807 * end of the leaf we adjust the split point significantly to the
1808 * right to try to optimize node fill and flag it. If we hit
1809 * that same leaf again our heuristic failed and we don't try
1810 * to optimize node fill (it could lead to a degenerate case).
1812 * Spikes are made up of two leaf elements which cannot be
1815 leaf = cursor->node;
1816 ondisk = leaf->ondisk;
1817 KKASSERT(ondisk->count > 4);
1818 if (cursor->index == ondisk->count &&
1819 (leaf->flags & HAMMER_NODE_NONLINEAR) == 0) {
1820 split = (ondisk->count + 1) * 3 / 4;
1821 leaf->flags |= HAMMER_NODE_NONLINEAR;
1823 split = (ondisk->count + 1) / 2;
1828 * If the insertion point is at the split point shift the
1829 * split point left so we don't have to worry about
1831 if (cursor->index == split)
1834 KKASSERT(split > 0 && split < ondisk->count);
1839 elm = &ondisk->elms[split];
1841 KKASSERT(hammer_btree_cmp(cursor->left_bound, &elm[-1].leaf.base) <= 0);
1842 KKASSERT(hammer_btree_cmp(cursor->left_bound, &elm->leaf.base) <= 0);
1843 KKASSERT(hammer_btree_cmp(cursor->right_bound, &elm->leaf.base) > 0);
1844 KKASSERT(hammer_btree_cmp(cursor->right_bound, &elm[1].leaf.base) > 0);
1847 * If we are at the root of the tree, create a new root node with
1848 * 1 element and split normally. Avoid making major modifications
1849 * until we know the whole operation will work.
1851 if (ondisk->parent == 0) {
1852 parent = hammer_alloc_btree(cursor->trans, 0, &error);
1855 hammer_lock_ex(&parent->lock);
1856 hammer_modify_node_noundo(cursor->trans, parent);
1857 ondisk = parent->ondisk;
1860 ondisk->mirror_tid = leaf->ondisk->mirror_tid;
1861 ondisk->type = HAMMER_BTREE_TYPE_INTERNAL;
1862 ondisk->elms[0].base = hmp->root_btree_beg;
1863 ondisk->elms[0].base.btype = leaf->ondisk->type;
1864 ondisk->elms[0].internal.subtree_offset = leaf->node_offset;
1865 ondisk->elms[1].base = hmp->root_btree_end;
1866 /* ondisk->elms[1].base.btype = not used */
1867 hammer_modify_node_done(parent);
1869 parent_index = 0; /* insertion point in parent */
1872 parent = cursor->parent;
1873 parent_index = cursor->parent_index;
1877 * Calculate a hint for the allocation of the new B-Tree leaf node.
1878 * For now just try to localize it within the same bigblock as
1881 * If the insertion point is at the end of the leaf we recognize a
1882 * likely append sequence of some sort (data, meta-data, inodes,
1883 * whatever). Set the hint to zero to allocate out of linear space
1884 * instead of trying to completely fill previously hinted space.
1886 * This also sets the stage for recursive splits to localize using
1889 ondisk = leaf->ondisk;
1890 if (cursor->index == ondisk->count)
1893 hint = leaf->node_offset;
1896 * Split leaf into new_leaf at the split point. Select a separator
1897 * value in-between the two leafs but with a bent towards the right
1898 * leaf since comparisons use an 'elm >= separator' inequality.
1907 new_leaf = hammer_alloc_btree(cursor->trans, 0, &error);
1908 if (new_leaf == NULL) {
1910 hammer_unlock(&parent->lock);
1911 hammer_delete_node(cursor->trans, parent);
1912 hammer_rel_node(parent);
1916 hammer_lock_ex(&new_leaf->lock);
1919 * Create the new node and copy the leaf elements from the split
1920 * point on to the new node.
1922 hammer_modify_node_all(cursor->trans, leaf);
1923 hammer_modify_node_noundo(cursor->trans, new_leaf);
1924 ondisk = leaf->ondisk;
1925 elm = &ondisk->elms[split];
1926 bcopy(elm, &new_leaf->ondisk->elms[0], (ondisk->count - split) * esize);
1927 new_leaf->ondisk->count = ondisk->count - split;
1928 new_leaf->ondisk->parent = parent->node_offset;
1929 new_leaf->ondisk->type = HAMMER_BTREE_TYPE_LEAF;
1930 new_leaf->ondisk->mirror_tid = ondisk->mirror_tid;
1931 KKASSERT(ondisk->type == new_leaf->ondisk->type);
1932 hammer_modify_node_done(new_leaf);
1933 hammer_cursor_split_node(leaf, new_leaf, split);
1936 * Cleanup the original node. Because this is a leaf node and
1937 * leaf nodes do not have a right-hand boundary, there
1938 * aren't any special edge cases to clean up. We just fixup the
1941 ondisk->count = split;
1944 * Insert the separator into the parent, fixup the parent's
1945 * reference to the original node, and reference the new node.
1946 * The separator is P.
1948 * Remember that base.count does not include the right-hand boundary.
1949 * We are copying parent_index+1 to parent_index+2, not +0 to +1.
1951 hammer_modify_node_all(cursor->trans, parent);
1952 ondisk = parent->ondisk;
1953 KKASSERT(split != 0);
1954 KKASSERT(ondisk->count != HAMMER_BTREE_INT_ELMS);
1955 parent_elm = &ondisk->elms[parent_index+1];
1956 bcopy(parent_elm, parent_elm + 1,
1957 (ondisk->count - parent_index) * esize);
1959 hammer_make_separator(&elm[-1].base, &elm[0].base, &parent_elm->base);
1960 parent_elm->internal.base.btype = new_leaf->ondisk->type;
1961 parent_elm->internal.subtree_offset = new_leaf->node_offset;
1962 parent_elm->internal.mirror_tid = new_leaf->ondisk->mirror_tid;
1963 mid_boundary = &parent_elm->base;
1965 hammer_modify_node_done(parent);
1966 hammer_cursor_inserted_element(parent, parent_index + 1);
1969 * The filesystem's root B-Tree pointer may have to be updated.
1972 hammer_volume_t volume;
1974 volume = hammer_get_root_volume(hmp, &error);
1975 KKASSERT(error == 0);
1977 hammer_modify_volume_field(cursor->trans, volume,
1979 volume->ondisk->vol0_btree_root = parent->node_offset;
1980 hammer_modify_volume_done(volume);
1981 leaf->ondisk->parent = parent->node_offset;
1982 if (cursor->parent) {
1983 hammer_unlock(&cursor->parent->lock);
1984 hammer_rel_node(cursor->parent);
1986 cursor->parent = parent; /* lock'd and ref'd */
1987 hammer_rel_volume(volume, 0);
1989 hammer_modify_node_done(leaf);
1992 * Ok, now adjust the cursor depending on which element the original
1993 * index was pointing at. If we are >= the split point the push node
1994 * is now in the new node.
1996 * NOTE: If we are at the split point itself we need to select the
1997 * old or new node based on where key_beg's insertion point will be.
1998 * If we pick the wrong side the inserted element will wind up in
1999 * the wrong leaf node and outside that node's bounds.
2001 if (cursor->index > split ||
2002 (cursor->index == split &&
2003 hammer_btree_cmp(&cursor->key_beg, mid_boundary) >= 0)) {
2004 cursor->parent_index = parent_index + 1;
2005 cursor->index -= split;
2006 hammer_unlock(&cursor->node->lock);
2007 hammer_rel_node(cursor->node);
2008 cursor->node = new_leaf;
2010 cursor->parent_index = parent_index;
2011 hammer_unlock(&new_leaf->lock);
2012 hammer_rel_node(new_leaf);
2016 * Fixup left and right bounds
2018 parent_elm = &parent->ondisk->elms[cursor->parent_index];
2019 cursor->left_bound = &parent_elm[0].internal.base;
2020 cursor->right_bound = &parent_elm[1].internal.base;
2023 * Assert that the bounds are correct.
2025 KKASSERT(hammer_btree_cmp(cursor->left_bound,
2026 &cursor->node->ondisk->elms[0].leaf.base) <= 0);
2027 KKASSERT(hammer_btree_cmp(cursor->right_bound,
2028 &cursor->node->ondisk->elms[cursor->node->ondisk->count-1].leaf.base) > 0);
2029 KKASSERT(hammer_btree_cmp(cursor->left_bound, &cursor->key_beg) <= 0);
2030 KKASSERT(hammer_btree_cmp(cursor->right_bound, &cursor->key_beg) > 0);
2033 hammer_cursor_downgrade(cursor);
2040 * Recursively correct the right-hand boundary's create_tid to (tid) as
2041 * long as the rest of the key matches. We have to recurse upward in
2042 * the tree as well as down the left side of each parent's right node.
2044 * Return EDEADLK if we were only partially successful, forcing the caller
2045 * to try again. The original cursor is not modified. This routine can
2046 * also fail with EDEADLK if it is forced to throw away a portion of its
2049 * The caller must pass a downgraded cursor to us (otherwise we can't dup it).
2052 TAILQ_ENTRY(hammer_rhb) entry;
2057 TAILQ_HEAD(hammer_rhb_list, hammer_rhb);
2060 hammer_btree_correct_rhb(hammer_cursor_t cursor, hammer_tid_t tid)
2062 struct hammer_mount *hmp;
2063 struct hammer_rhb_list rhb_list;
2064 hammer_base_elm_t elm;
2065 hammer_node_t orig_node;
2066 struct hammer_rhb *rhb;
2070 TAILQ_INIT(&rhb_list);
2071 hmp = cursor->trans->hmp;
2074 * Save our position so we can restore it on return. This also
2075 * gives us a stable 'elm'.
2077 orig_node = cursor->node;
2078 hammer_ref_node(orig_node);
2079 hammer_lock_sh(&orig_node->lock);
2080 orig_index = cursor->index;
2081 elm = &orig_node->ondisk->elms[orig_index].base;
2084 * Now build a list of parents going up, allocating a rhb
2085 * structure for each one.
2087 while (cursor->parent) {
2089 * Stop if we no longer have any right-bounds to fix up
2091 if (elm->obj_id != cursor->right_bound->obj_id ||
2092 elm->rec_type != cursor->right_bound->rec_type ||
2093 elm->key != cursor->right_bound->key) {
2098 * Stop if the right-hand bound's create_tid does not
2099 * need to be corrected.
2101 if (cursor->right_bound->create_tid >= tid)
2104 rhb = kmalloc(sizeof(*rhb), hmp->m_misc, M_WAITOK|M_ZERO);
2105 rhb->node = cursor->parent;
2106 rhb->index = cursor->parent_index;
2107 hammer_ref_node(rhb->node);
2108 hammer_lock_sh(&rhb->node->lock);
2109 TAILQ_INSERT_HEAD(&rhb_list, rhb, entry);
2111 hammer_cursor_up(cursor);
2115 * now safely adjust the right hand bound for each rhb. This may
2116 * also require taking the right side of the tree and iterating down
2120 while (error == 0 && (rhb = TAILQ_FIRST(&rhb_list)) != NULL) {
2121 error = hammer_cursor_seek(cursor, rhb->node, rhb->index);
2124 TAILQ_REMOVE(&rhb_list, rhb, entry);
2125 hammer_unlock(&rhb->node->lock);
2126 hammer_rel_node(rhb->node);
2127 kfree(rhb, hmp->m_misc);
2129 switch (cursor->node->ondisk->type) {
2130 case HAMMER_BTREE_TYPE_INTERNAL:
2132 * Right-boundary for parent at internal node
2133 * is one element to the right of the element whos
2134 * right boundary needs adjusting. We must then
2135 * traverse down the left side correcting any left
2136 * bounds (which may now be too far to the left).
2139 error = hammer_btree_correct_lhb(cursor, tid);
2142 panic("hammer_btree_correct_rhb(): Bad node type");
2151 while ((rhb = TAILQ_FIRST(&rhb_list)) != NULL) {
2152 TAILQ_REMOVE(&rhb_list, rhb, entry);
2153 hammer_unlock(&rhb->node->lock);
2154 hammer_rel_node(rhb->node);
2155 kfree(rhb, hmp->m_misc);
2157 error = hammer_cursor_seek(cursor, orig_node, orig_index);
2158 hammer_unlock(&orig_node->lock);
2159 hammer_rel_node(orig_node);
2164 * Similar to rhb (in fact, rhb calls lhb), but corrects the left hand
2165 * bound going downward starting at the current cursor position.
2167 * This function does not restore the cursor after use.
2170 hammer_btree_correct_lhb(hammer_cursor_t cursor, hammer_tid_t tid)
2172 struct hammer_rhb_list rhb_list;
2173 hammer_base_elm_t elm;
2174 hammer_base_elm_t cmp;
2175 struct hammer_rhb *rhb;
2176 struct hammer_mount *hmp;
2179 TAILQ_INIT(&rhb_list);
2180 hmp = cursor->trans->hmp;
2182 cmp = &cursor->node->ondisk->elms[cursor->index].base;
2185 * Record the node and traverse down the left-hand side for all
2186 * matching records needing a boundary correction.
2190 rhb = kmalloc(sizeof(*rhb), hmp->m_misc, M_WAITOK|M_ZERO);
2191 rhb->node = cursor->node;
2192 rhb->index = cursor->index;
2193 hammer_ref_node(rhb->node);
2194 hammer_lock_sh(&rhb->node->lock);
2195 TAILQ_INSERT_HEAD(&rhb_list, rhb, entry);
2197 if (cursor->node->ondisk->type == HAMMER_BTREE_TYPE_INTERNAL) {
2199 * Nothing to traverse down if we are at the right
2200 * boundary of an internal node.
2202 if (cursor->index == cursor->node->ondisk->count)
2205 elm = &cursor->node->ondisk->elms[cursor->index].base;
2206 if (elm->btype == HAMMER_BTREE_TYPE_RECORD)
2208 panic("Illegal leaf record type %02x", elm->btype);
2210 error = hammer_cursor_down(cursor);
2214 elm = &cursor->node->ondisk->elms[cursor->index].base;
2215 if (elm->obj_id != cmp->obj_id ||
2216 elm->rec_type != cmp->rec_type ||
2217 elm->key != cmp->key) {
2220 if (elm->create_tid >= tid)
2226 * Now we can safely adjust the left-hand boundary from the bottom-up.
2227 * The last element we remove from the list is the caller's right hand
2228 * boundary, which must also be adjusted.
2230 while (error == 0 && (rhb = TAILQ_FIRST(&rhb_list)) != NULL) {
2231 error = hammer_cursor_seek(cursor, rhb->node, rhb->index);
2234 TAILQ_REMOVE(&rhb_list, rhb, entry);
2235 hammer_unlock(&rhb->node->lock);
2236 hammer_rel_node(rhb->node);
2237 kfree(rhb, hmp->m_misc);
2239 elm = &cursor->node->ondisk->elms[cursor->index].base;
2240 if (cursor->node->ondisk->type == HAMMER_BTREE_TYPE_INTERNAL) {
2241 hammer_modify_node(cursor->trans, cursor->node,
2243 sizeof(elm->create_tid));
2244 elm->create_tid = tid;
2245 hammer_modify_node_done(cursor->node);
2247 panic("hammer_btree_correct_lhb(): Bad element type");
2254 while ((rhb = TAILQ_FIRST(&rhb_list)) != NULL) {
2255 TAILQ_REMOVE(&rhb_list, rhb, entry);
2256 hammer_unlock(&rhb->node->lock);
2257 hammer_rel_node(rhb->node);
2258 kfree(rhb, hmp->m_misc);
2266 * Attempt to remove the locked, empty or want-to-be-empty B-Tree node at
2267 * (cursor->node). Returns 0 on success, EDEADLK if we could not complete
2268 * the operation due to a deadlock, or some other error.
2270 * This routine is initially called with an empty leaf and may be
2271 * recursively called with single-element internal nodes.
2273 * It should also be noted that when removing empty leaves we must be sure
2274 * to test and update mirror_tid because another thread may have deadlocked
2275 * against us (or someone) trying to propagate it up and cannot retry once
2276 * the node has been deleted.
2278 * On return the cursor may end up pointing to an internal node, suitable
2279 * for further iteration but not for an immediate insertion or deletion.
2282 btree_remove(hammer_cursor_t cursor)
2284 hammer_node_ondisk_t ondisk;
2285 hammer_btree_elm_t elm;
2287 hammer_node_t parent;
2288 const int esize = sizeof(*elm);
2291 node = cursor->node;
2294 * When deleting the root of the filesystem convert it to
2295 * an empty leaf node. Internal nodes cannot be empty.
2297 ondisk = node->ondisk;
2298 if (ondisk->parent == 0) {
2299 KKASSERT(cursor->parent == NULL);
2300 hammer_modify_node_all(cursor->trans, node);
2301 KKASSERT(ondisk == node->ondisk);
2302 ondisk->type = HAMMER_BTREE_TYPE_LEAF;
2304 hammer_modify_node_done(node);
2309 parent = cursor->parent;
2312 * Attempt to remove the parent's reference to the child. If the
2313 * parent would become empty we have to recurse. If we fail we
2314 * leave the parent pointing to an empty leaf node.
2316 * We have to recurse successfully before we can delete the internal
2317 * node as it is illegal to have empty internal nodes. Even though
2318 * the operation may be aborted we must still fixup any unlocked
2319 * cursors as if we had deleted the element prior to recursing
2320 * (by calling hammer_cursor_deleted_element()) so those cursors
2321 * are properly forced up the chain by the recursion.
2323 if (parent->ondisk->count == 1) {
2325 * This special cursor_up_locked() call leaves the original
2326 * node exclusively locked and referenced, leaves the
2327 * original parent locked (as the new node), and locks the
2328 * new parent. It can return EDEADLK.
2330 * We cannot call hammer_cursor_removed_node() until we are
2331 * actually able to remove the node. If we did then tracked
2332 * cursors in the middle of iterations could be repointed
2333 * to a parent node. If this occurs they could end up
2334 * scanning newly inserted records into the node (that could
2335 * not be deleted) when they push down again.
2337 * Due to the way the recursion works the final parent is left
2338 * in cursor->parent after the recursion returns. Each
2339 * layer on the way back up is thus able to call
2340 * hammer_cursor_removed_node() and 'jump' the node up to
2341 * the (same) final parent.
2343 * NOTE! The local variable 'parent' is invalid after we
2344 * call hammer_cursor_up_locked().
2346 error = hammer_cursor_up_locked(cursor);
2350 hammer_cursor_deleted_element(cursor->node, 0);
2351 error = btree_remove(cursor);
2353 KKASSERT(node != cursor->node);
2354 hammer_cursor_removed_node(
2357 hammer_modify_node_all(cursor->trans, node);
2358 ondisk = node->ondisk;
2359 ondisk->type = HAMMER_BTREE_TYPE_DELETED;
2361 hammer_modify_node_done(node);
2362 hammer_flush_node(node, 0);
2363 hammer_delete_node(cursor->trans, node);
2366 * Defer parent removal because we could not
2367 * get the lock, just let the leaf remain
2372 hammer_unlock(&node->lock);
2373 hammer_rel_node(node);
2376 * Defer parent removal because we could not
2377 * get the lock, just let the leaf remain
2383 KKASSERT(parent->ondisk->count > 1);
2385 hammer_modify_node_all(cursor->trans, parent);
2386 ondisk = parent->ondisk;
2387 KKASSERT(ondisk->type == HAMMER_BTREE_TYPE_INTERNAL);
2389 elm = &ondisk->elms[cursor->parent_index];
2390 KKASSERT(elm->internal.subtree_offset == node->node_offset);
2391 KKASSERT(ondisk->count > 0);
2394 * We must retain the highest mirror_tid. The deleted
2395 * range is now encompassed by the element to the left.
2396 * If we are already at the left edge the new left edge
2397 * inherits mirror_tid.
2399 * Note that bounds of the parent to our parent may create
2400 * a gap to the left of our left-most node or to the right
2401 * of our right-most node. The gap is silently included
2402 * in the mirror_tid's area of effect from the point of view
2405 if (cursor->parent_index) {
2406 if (elm[-1].internal.mirror_tid <
2407 elm[0].internal.mirror_tid) {
2408 elm[-1].internal.mirror_tid =
2409 elm[0].internal.mirror_tid;
2412 if (elm[1].internal.mirror_tid <
2413 elm[0].internal.mirror_tid) {
2414 elm[1].internal.mirror_tid =
2415 elm[0].internal.mirror_tid;
2420 * Delete the subtree reference in the parent. Include
2421 * boundary element at end.
2423 bcopy(&elm[1], &elm[0],
2424 (ondisk->count - cursor->parent_index) * esize);
2426 hammer_modify_node_done(parent);
2427 hammer_cursor_removed_node(node, parent, cursor->parent_index);
2428 hammer_cursor_deleted_element(parent, cursor->parent_index);
2429 hammer_flush_node(node, 0);
2430 hammer_delete_node(cursor->trans, node);
2433 * cursor->node is invalid, cursor up to make the cursor
2434 * valid again. We have to flag the condition in case
2435 * another thread wiggles an insertion in during an
2438 cursor->flags |= HAMMER_CURSOR_ITERATE_CHECK;
2439 error = hammer_cursor_up(cursor);
2445 * Propagate cursor->trans->tid up the B-Tree starting at the current
2446 * cursor position using pseudofs info gleaned from the passed inode.
2448 * The passed inode has no relationship to the cursor position other
2449 * then being in the same pseudofs as the insertion or deletion we
2450 * are propagating the mirror_tid for.
2452 * WARNING! Because we push and pop the passed cursor, it may be
2453 * modified by other B-Tree operations while it is unlocked
2454 * and things like the node & leaf pointers, and indexes might
2458 hammer_btree_do_propagation(hammer_cursor_t cursor,
2459 hammer_pseudofs_inmem_t pfsm,
2460 hammer_btree_leaf_elm_t leaf)
2462 hammer_cursor_t ncursor;
2463 hammer_tid_t mirror_tid;
2467 * We do not propagate a mirror_tid if the filesystem was mounted
2468 * in no-mirror mode.
2470 if (cursor->trans->hmp->master_id < 0)
2474 * This is a bit of a hack because we cannot deadlock or return
2475 * EDEADLK here. The related operation has already completed and
2476 * we must propagate the mirror_tid now regardless.
2478 * Generate a new cursor which inherits the original's locks and
2479 * unlock the original. Use the new cursor to propagate the
2480 * mirror_tid. Then clean up the new cursor and reacquire locks
2483 * hammer_dup_cursor() cannot dup locks. The dup inherits the
2484 * original's locks and the original is tracked and must be
2487 mirror_tid = cursor->node->ondisk->mirror_tid;
2488 KKASSERT(mirror_tid != 0);
2489 ncursor = hammer_push_cursor(cursor);
2490 error = hammer_btree_mirror_propagate(ncursor, mirror_tid);
2491 KKASSERT(error == 0);
2492 hammer_pop_cursor(cursor, ncursor);
2493 /* WARNING: cursor's leaf pointer may change after pop */
2498 * Propagate a mirror TID update upwards through the B-Tree to the root.
2500 * A locked internal node must be passed in. The node will remain locked
2503 * This function syncs mirror_tid at the specified internal node's element,
2504 * adjusts the node's aggregation mirror_tid, and then recurses upwards.
2507 hammer_btree_mirror_propagate(hammer_cursor_t cursor, hammer_tid_t mirror_tid)
2509 hammer_btree_internal_elm_t elm;
2514 error = hammer_cursor_up(cursor);
2516 error = hammer_cursor_upgrade(cursor);
2519 * We can ignore HAMMER_CURSOR_ITERATE_CHECK, the
2520 * cursor will still be properly positioned for
2521 * mirror propagation, just not for iterations.
2523 while (error == EDEADLK) {
2524 hammer_recover_cursor(cursor);
2525 error = hammer_cursor_upgrade(cursor);
2531 * If the cursor deadlocked it could end up at a leaf
2532 * after we lost the lock.
2534 node = cursor->node;
2535 if (node->ondisk->type != HAMMER_BTREE_TYPE_INTERNAL)
2539 * Adjust the node's element
2541 elm = &node->ondisk->elms[cursor->index].internal;
2542 if (elm->mirror_tid >= mirror_tid)
2544 hammer_modify_node(cursor->trans, node, &elm->mirror_tid,
2545 sizeof(elm->mirror_tid));
2546 elm->mirror_tid = mirror_tid;
2547 hammer_modify_node_done(node);
2548 if (hammer_debug_general & 0x0002) {
2549 kprintf("mirror_propagate: propagate "
2550 "%016llx @%016llx:%d\n",
2551 (long long)mirror_tid,
2552 (long long)node->node_offset,
2558 * Adjust the node's mirror_tid aggregator
2560 if (node->ondisk->mirror_tid >= mirror_tid)
2562 hammer_modify_node_field(cursor->trans, node, mirror_tid);
2563 node->ondisk->mirror_tid = mirror_tid;
2564 hammer_modify_node_done(node);
2565 if (hammer_debug_general & 0x0002) {
2566 kprintf("mirror_propagate: propagate "
2567 "%016llx @%016llx\n",
2568 (long long)mirror_tid,
2569 (long long)node->node_offset);
2572 if (error == ENOENT)
2578 hammer_btree_get_parent(hammer_transaction_t trans, hammer_node_t node,
2579 int *parent_indexp, int *errorp, int try_exclusive)
2581 hammer_node_t parent;
2582 hammer_btree_elm_t elm;
2588 parent = hammer_get_node(trans, node->ondisk->parent, 0, errorp);
2590 KKASSERT(parent == NULL);
2593 KKASSERT ((parent->flags & HAMMER_NODE_DELETED) == 0);
2598 if (try_exclusive) {
2599 if (hammer_lock_ex_try(&parent->lock)) {
2600 hammer_rel_node(parent);
2605 hammer_lock_sh(&parent->lock);
2609 * Figure out which element in the parent is pointing to the
2612 if (node->ondisk->count) {
2613 i = hammer_btree_search_node(&node->ondisk->elms[0].base,
2618 while (i < parent->ondisk->count) {
2619 elm = &parent->ondisk->elms[i];
2620 if (elm->internal.subtree_offset == node->node_offset)
2624 if (i == parent->ondisk->count) {
2625 hammer_unlock(&parent->lock);
2626 panic("Bad B-Tree link: parent %p node %p\n", parent, node);
2629 KKASSERT(*errorp == 0);
2634 * The element (elm) has been moved to a new internal node (node).
2636 * If the element represents a pointer to an internal node that node's
2637 * parent must be adjusted to the element's new location.
2639 * XXX deadlock potential here with our exclusive locks
2642 btree_set_parent(hammer_transaction_t trans, hammer_node_t node,
2643 hammer_btree_elm_t elm)
2645 hammer_node_t child;
2650 switch(elm->base.btype) {
2651 case HAMMER_BTREE_TYPE_INTERNAL:
2652 case HAMMER_BTREE_TYPE_LEAF:
2653 child = hammer_get_node(trans, elm->internal.subtree_offset,
2656 hammer_modify_node_field(trans, child, parent);
2657 child->ondisk->parent = node->node_offset;
2658 hammer_modify_node_done(child);
2659 hammer_rel_node(child);
2669 * Initialize the root of a recursive B-Tree node lock list structure.
2672 hammer_node_lock_init(hammer_node_lock_t parent, hammer_node_t node)
2674 TAILQ_INIT(&parent->list);
2675 parent->parent = NULL;
2676 parent->node = node;
2678 parent->count = node->ondisk->count;
2679 parent->copy = NULL;
2684 * Initialize a cache of hammer_node_lock's including space allocated
2687 * This is used by the rebalancing code to preallocate the copy space
2688 * for ~4096 B-Tree nodes (16MB of data) prior to acquiring any HAMMER
2689 * locks, otherwise we can blow out the pageout daemon's emergency
2690 * reserve and deadlock it.
2692 * NOTE: HAMMER_NODE_LOCK_LCACHE is not set on items cached in the lcache.
2693 * The flag is set when the item is pulled off the cache for use.
2696 hammer_btree_lcache_init(hammer_mount_t hmp, hammer_node_lock_t lcache,
2699 hammer_node_lock_t item;
2702 for (count = 1; depth; --depth)
2703 count *= HAMMER_BTREE_LEAF_ELMS;
2704 bzero(lcache, sizeof(*lcache));
2705 TAILQ_INIT(&lcache->list);
2707 item = kmalloc(sizeof(*item), hmp->m_misc, M_WAITOK|M_ZERO);
2708 item->copy = kmalloc(sizeof(*item->copy),
2709 hmp->m_misc, M_WAITOK);
2710 TAILQ_INIT(&item->list);
2711 TAILQ_INSERT_TAIL(&lcache->list, item, entry);
2717 hammer_btree_lcache_free(hammer_mount_t hmp, hammer_node_lock_t lcache)
2719 hammer_node_lock_t item;
2721 while ((item = TAILQ_FIRST(&lcache->list)) != NULL) {
2722 TAILQ_REMOVE(&lcache->list, item, entry);
2723 KKASSERT(item->copy);
2724 KKASSERT(TAILQ_EMPTY(&item->list));
2725 kfree(item->copy, hmp->m_misc);
2726 kfree(item, hmp->m_misc);
2728 KKASSERT(lcache->copy == NULL);
2732 * Exclusively lock all the children of node. This is used by the split
2733 * code to prevent anyone from accessing the children of a cursor node
2734 * while we fix-up its parent offset.
2736 * If we don't lock the children we can really mess up cursors which block
2737 * trying to cursor-up into our node.
2739 * On failure EDEADLK (or some other error) is returned. If a deadlock
2740 * error is returned the cursor is adjusted to block on termination.
2742 * The caller is responsible for managing parent->node, the root's node
2743 * is usually aliased from a cursor.
2746 hammer_btree_lock_children(hammer_cursor_t cursor, int depth,
2747 hammer_node_lock_t parent,
2748 hammer_node_lock_t lcache)
2751 hammer_node_lock_t item;
2752 hammer_node_ondisk_t ondisk;
2753 hammer_btree_elm_t elm;
2754 hammer_node_t child;
2755 struct hammer_mount *hmp;
2759 node = parent->node;
2760 ondisk = node->ondisk;
2762 hmp = cursor->trans->hmp;
2765 * We really do not want to block on I/O with exclusive locks held,
2766 * pre-get the children before trying to lock the mess. This is
2767 * only done one-level deep for now.
2769 for (i = 0; i < ondisk->count; ++i) {
2770 ++hammer_stats_btree_elements;
2771 elm = &ondisk->elms[i];
2772 if (elm->base.btype != HAMMER_BTREE_TYPE_LEAF &&
2773 elm->base.btype != HAMMER_BTREE_TYPE_INTERNAL) {
2776 child = hammer_get_node(cursor->trans,
2777 elm->internal.subtree_offset,
2780 hammer_rel_node(child);
2786 for (i = 0; error == 0 && i < ondisk->count; ++i) {
2787 ++hammer_stats_btree_elements;
2788 elm = &ondisk->elms[i];
2790 switch(elm->base.btype) {
2791 case HAMMER_BTREE_TYPE_INTERNAL:
2792 case HAMMER_BTREE_TYPE_LEAF:
2793 KKASSERT(elm->internal.subtree_offset != 0);
2794 child = hammer_get_node(cursor->trans,
2795 elm->internal.subtree_offset,
2803 if (hammer_lock_ex_try(&child->lock) != 0) {
2804 if (cursor->deadlk_node == NULL) {
2805 cursor->deadlk_node = child;
2806 hammer_ref_node(cursor->deadlk_node);
2809 hammer_rel_node(child);
2812 item = TAILQ_FIRST(&lcache->list);
2813 KKASSERT(item != NULL);
2814 item->flags |= HAMMER_NODE_LOCK_LCACHE;
2815 TAILQ_REMOVE(&lcache->list,
2818 item = kmalloc(sizeof(*item),
2821 TAILQ_INIT(&item->list);
2824 TAILQ_INSERT_TAIL(&parent->list, item, entry);
2825 item->parent = parent;
2828 item->count = child->ondisk->count;
2831 * Recurse (used by the rebalancing code)
2833 if (depth > 1 && elm->base.btype == HAMMER_BTREE_TYPE_INTERNAL) {
2834 error = hammer_btree_lock_children(
2844 hammer_btree_unlock_children(hmp, parent, lcache);
2849 * Create an in-memory copy of all B-Tree nodes listed, recursively,
2850 * including the parent.
2853 hammer_btree_lock_copy(hammer_cursor_t cursor, hammer_node_lock_t parent)
2855 hammer_mount_t hmp = cursor->trans->hmp;
2856 hammer_node_lock_t item;
2858 if (parent->copy == NULL) {
2859 KKASSERT((parent->flags & HAMMER_NODE_LOCK_LCACHE) == 0);
2860 parent->copy = kmalloc(sizeof(*parent->copy),
2861 hmp->m_misc, M_WAITOK);
2863 KKASSERT((parent->flags & HAMMER_NODE_LOCK_UPDATED) == 0);
2864 *parent->copy = *parent->node->ondisk;
2865 TAILQ_FOREACH(item, &parent->list, entry) {
2866 hammer_btree_lock_copy(cursor, item);
2871 * Recursively sync modified copies to the media.
2874 hammer_btree_sync_copy(hammer_cursor_t cursor, hammer_node_lock_t parent)
2876 hammer_node_lock_t item;
2879 if (parent->flags & HAMMER_NODE_LOCK_UPDATED) {
2881 hammer_modify_node_all(cursor->trans, parent->node);
2882 *parent->node->ondisk = *parent->copy;
2883 hammer_modify_node_done(parent->node);
2884 if (parent->copy->type == HAMMER_BTREE_TYPE_DELETED) {
2885 hammer_flush_node(parent->node, 0);
2886 hammer_delete_node(cursor->trans, parent->node);
2889 TAILQ_FOREACH(item, &parent->list, entry) {
2890 count += hammer_btree_sync_copy(cursor, item);
2896 * Release previously obtained node locks. The caller is responsible for
2897 * cleaning up parent->node itself (its usually just aliased from a cursor),
2898 * but this function will take care of the copies.
2900 * NOTE: The root node is not placed in the lcache and node->copy is not
2901 * deallocated when lcache != NULL.
2904 hammer_btree_unlock_children(hammer_mount_t hmp, hammer_node_lock_t parent,
2905 hammer_node_lock_t lcache)
2907 hammer_node_lock_t item;
2908 hammer_node_ondisk_t copy;
2910 while ((item = TAILQ_FIRST(&parent->list)) != NULL) {
2911 TAILQ_REMOVE(&parent->list, item, entry);
2912 hammer_btree_unlock_children(hmp, item, lcache);
2913 hammer_unlock(&item->node->lock);
2914 hammer_rel_node(item->node);
2917 * NOTE: When placing the item back in the lcache
2918 * the flag is cleared by the bzero().
2919 * Remaining fields are cleared as a safety
2922 KKASSERT(item->flags & HAMMER_NODE_LOCK_LCACHE);
2923 KKASSERT(TAILQ_EMPTY(&item->list));
2925 bzero(item, sizeof(*item));
2926 TAILQ_INIT(&item->list);
2929 bzero(copy, sizeof(*copy));
2930 TAILQ_INSERT_TAIL(&lcache->list, item, entry);
2932 kfree(item, hmp->m_misc);
2935 if (parent->copy && (parent->flags & HAMMER_NODE_LOCK_LCACHE) == 0) {
2936 kfree(parent->copy, hmp->m_misc);
2937 parent->copy = NULL; /* safety */
2941 /************************************************************************
2942 * MISCELLANIOUS SUPPORT *
2943 ************************************************************************/
2946 * Compare two B-Tree elements, return -N, 0, or +N (e.g. similar to strcmp).
2948 * Note that for this particular function a return value of -1, 0, or +1
2949 * can denote a match if create_tid is otherwise discounted. A create_tid
2950 * of zero is considered to be 'infinity' in comparisons.
2952 * See also hammer_rec_rb_compare() and hammer_rec_cmp() in hammer_object.c.
2955 hammer_btree_cmp(hammer_base_elm_t key1, hammer_base_elm_t key2)
2957 if (key1->localization < key2->localization)
2959 if (key1->localization > key2->localization)
2962 if (key1->obj_id < key2->obj_id)
2964 if (key1->obj_id > key2->obj_id)
2967 if (key1->rec_type < key2->rec_type)
2969 if (key1->rec_type > key2->rec_type)
2972 if (key1->key < key2->key)
2974 if (key1->key > key2->key)
2978 * A create_tid of zero indicates a record which is undeletable
2979 * and must be considered to have a value of positive infinity.
2981 if (key1->create_tid == 0) {
2982 if (key2->create_tid == 0)
2986 if (key2->create_tid == 0)
2988 if (key1->create_tid < key2->create_tid)
2990 if (key1->create_tid > key2->create_tid)
2996 * Test a timestamp against an element to determine whether the
2997 * element is visible. A timestamp of 0 means 'infinity'.
3000 hammer_btree_chkts(hammer_tid_t asof, hammer_base_elm_t base)
3003 if (base->delete_tid)
3007 if (asof < base->create_tid)
3009 if (base->delete_tid && asof >= base->delete_tid)
3015 * Create a separator half way inbetween key1 and key2. For fields just
3016 * one unit apart, the separator will match key2. key1 is on the left-hand
3017 * side and key2 is on the right-hand side.
3019 * key2 must be >= the separator. It is ok for the separator to match key2.
3021 * NOTE: Even if key1 does not match key2, the separator may wind up matching
3024 * NOTE: It might be beneficial to just scrap this whole mess and just
3025 * set the separator to key2.
3027 #define MAKE_SEPARATOR(key1, key2, dest, field) \
3028 dest->field = key1->field + ((key2->field - key1->field + 1) >> 1);
3031 hammer_make_separator(hammer_base_elm_t key1, hammer_base_elm_t key2,
3032 hammer_base_elm_t dest)
3034 bzero(dest, sizeof(*dest));
3036 dest->rec_type = key2->rec_type;
3037 dest->key = key2->key;
3038 dest->obj_id = key2->obj_id;
3039 dest->create_tid = key2->create_tid;
3041 MAKE_SEPARATOR(key1, key2, dest, localization);
3042 if (key1->localization == key2->localization) {
3043 MAKE_SEPARATOR(key1, key2, dest, obj_id);
3044 if (key1->obj_id == key2->obj_id) {
3045 MAKE_SEPARATOR(key1, key2, dest, rec_type);
3046 if (key1->rec_type == key2->rec_type) {
3047 MAKE_SEPARATOR(key1, key2, dest, key);
3049 * Don't bother creating a separator for
3050 * create_tid, which also conveniently avoids
3051 * having to handle the create_tid == 0
3052 * (infinity) case. Just leave create_tid
3055 * Worst case, dest matches key2 exactly,
3056 * which is acceptable.
3063 #undef MAKE_SEPARATOR
3066 * Return whether a generic internal or leaf node is full
3069 btree_node_is_full(hammer_node_ondisk_t node)
3071 switch(node->type) {
3072 case HAMMER_BTREE_TYPE_INTERNAL:
3073 if (node->count == HAMMER_BTREE_INT_ELMS)
3076 case HAMMER_BTREE_TYPE_LEAF:
3077 if (node->count == HAMMER_BTREE_LEAF_ELMS)
3081 panic("illegal btree subtype");
3088 btree_max_elements(u_int8_t type)
3090 if (type == HAMMER_BTREE_TYPE_LEAF)
3091 return(HAMMER_BTREE_LEAF_ELMS);
3092 if (type == HAMMER_BTREE_TYPE_INTERNAL)
3093 return(HAMMER_BTREE_INT_ELMS);
3094 panic("btree_max_elements: bad type %d\n", type);
3099 hammer_print_btree_node(hammer_node_ondisk_t ondisk)
3101 hammer_btree_elm_t elm;
3104 kprintf("node %p count=%d parent=%016llx type=%c\n",
3105 ondisk, ondisk->count,
3106 (long long)ondisk->parent, ondisk->type);
3109 * Dump both boundary elements if an internal node
3111 if (ondisk->type == HAMMER_BTREE_TYPE_INTERNAL) {
3112 for (i = 0; i <= ondisk->count; ++i) {
3113 elm = &ondisk->elms[i];
3114 hammer_print_btree_elm(elm, ondisk->type, i);
3117 for (i = 0; i < ondisk->count; ++i) {
3118 elm = &ondisk->elms[i];
3119 hammer_print_btree_elm(elm, ondisk->type, i);
3125 hammer_print_btree_elm(hammer_btree_elm_t elm, u_int8_t type, int i)
3128 kprintf("\tobj_id = %016llx\n", (long long)elm->base.obj_id);
3129 kprintf("\tkey = %016llx\n", (long long)elm->base.key);
3130 kprintf("\tcreate_tid = %016llx\n", (long long)elm->base.create_tid);
3131 kprintf("\tdelete_tid = %016llx\n", (long long)elm->base.delete_tid);
3132 kprintf("\trec_type = %04x\n", elm->base.rec_type);
3133 kprintf("\tobj_type = %02x\n", elm->base.obj_type);
3134 kprintf("\tbtype = %02x (%c)\n",
3136 (elm->base.btype ? elm->base.btype : '?'));
3137 kprintf("\tlocalization = %02x\n", elm->base.localization);
3140 case HAMMER_BTREE_TYPE_INTERNAL:
3141 kprintf("\tsubtree_off = %016llx\n",
3142 (long long)elm->internal.subtree_offset);
3144 case HAMMER_BTREE_TYPE_RECORD:
3145 kprintf("\tdata_offset = %016llx\n",
3146 (long long)elm->leaf.data_offset);
3147 kprintf("\tdata_len = %08x\n", elm->leaf.data_len);
3148 kprintf("\tdata_crc = %08x\n", elm->leaf.data_crc);