2 * Copyright (c) 2009 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
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
37 static int rebalance_node(struct hammer_ioc_rebalance
*rebal
,
38 hammer_cursor_t cursor
, hammer_node_lock_t lcache
);
39 static void rebalance_closeout(hammer_node_lock_t base_item
, int base_count
,
40 hammer_btree_elm_t elm
);
41 static void rebalance_parent_ptrs(hammer_node_lock_t base_item
, int index
,
42 hammer_node_lock_t item
, hammer_node_lock_t chld_item
);
45 * Iterate through the specified range of object ids and rebalance B-Tree
46 * leaf and internal nodes we encounter. A forwards iteration is used.
48 * All leafs are at the same depth. We use the b-tree scan code loosely
49 * to position ourselves and create degenerate cases to skip indices
50 * that we have rebalanced in bulk.
54 hammer_ioc_rebalance(hammer_transaction_t trans
, hammer_inode_t ip
,
55 struct hammer_ioc_rebalance
*rebal
)
57 struct hammer_cursor cursor
;
58 struct hammer_node_lock lcache
;
59 hammer_btree_leaf_elm_t elm
;
62 uint32_t key_end_localization
;
64 if ((rebal
->key_beg
.localization
| rebal
->key_end
.localization
) &
65 HAMMER_LOCALIZE_PSEUDOFS_MASK
) {
68 if (rebal
->key_beg
.localization
> rebal
->key_end
.localization
)
70 if (rebal
->key_beg
.localization
== rebal
->key_end
.localization
) {
71 if (rebal
->key_beg
.obj_id
> rebal
->key_end
.obj_id
)
73 /* key-space limitations - no check needed */
75 if (rebal
->saturation
< HAMMER_BTREE_INT_ELMS
/ 2)
76 rebal
->saturation
= HAMMER_BTREE_INT_ELMS
/ 2;
77 if (rebal
->saturation
> HAMMER_BTREE_INT_ELMS
)
78 rebal
->saturation
= HAMMER_BTREE_INT_ELMS
;
81 * Ioctl caller has only set localization type to rebalance.
82 * Initialize cursor key localization with ip localization.
84 rebal
->key_cur
= rebal
->key_beg
;
85 rebal
->key_cur
.localization
&= HAMMER_LOCALIZE_MASK
;
86 if (rebal
->allpfs
== 0)
87 rebal
->key_cur
.localization
|= ip
->obj_localization
;
89 key_end_localization
= rebal
->key_end
.localization
;
90 key_end_localization
&= HAMMER_LOCALIZE_MASK
;
91 if (rebal
->allpfs
== 0)
92 key_end_localization
|= ip
->obj_localization
;
94 key_end_localization
|= pfs_to_lo(HAMMER_MAX_PFSID
);
96 hammer_btree_lcache_init(trans
->hmp
, &lcache
, 2);
98 seq
= trans
->hmp
->flusher
.done
;
101 * Scan forwards. Retries typically occur if a deadlock is detected.
104 error
= hammer_init_cursor(trans
, &cursor
, NULL
, NULL
);
106 hammer_done_cursor(&cursor
);
109 cursor
.key_beg
= rebal
->key_cur
;
110 cursor
.key_end
= rebal
->key_end
;
111 cursor
.key_end
.localization
= key_end_localization
;
112 cursor
.flags
|= HAMMER_CURSOR_END_INCLUSIVE
;
113 cursor
.flags
|= HAMMER_CURSOR_BACKEND
;
116 * Cause internal nodes to be returned on the way up. Internal nodes
117 * are not returned on the way down so we can create a degenerate
118 * case to handle internal nodes as a trailing function of their
121 * Note that by not setting INSERTING or PRUNING no boundary
122 * corrections will be made and a sync lock is not needed for the
123 * B-Tree scan itself.
125 cursor
.flags
|= HAMMER_CURSOR_REBLOCKING
;
127 error
= hammer_btree_first(&cursor
);
131 * Rebalancing can be hard on the memory allocator, make
132 * sure there is enough free memory before doing it.
134 if (vm_test_nominal()) {
135 hammer_unlock_cursor(&cursor
);
137 hammer_lock_cursor(&cursor
);
141 * We only care about internal nodes visited for the last
142 * time on the way up... that is, a trailing scan of the
143 * internal node after all of its children have been recursed
146 if (cursor
.node
->ondisk
->type
== HAMMER_BTREE_TYPE_INTERNAL
) {
148 * Leave cursor.index alone, we want to recurse
149 * through all children of the internal node before
152 * Process the internal node on the way up after
153 * the last child's sub-tree has been balanced.
155 if (cursor
.index
== cursor
.node
->ondisk
->count
- 1) {
156 hammer_sync_lock_sh(trans
);
157 error
= rebalance_node(rebal
, &cursor
, &lcache
);
158 hammer_sync_unlock(trans
);
162 * We don't need to iterate through all the leaf
163 * elements, we only care about the parent (internal)
166 cursor
.index
= cursor
.node
->ondisk
->count
- 1;
172 * Update returned scan position and do a flush if
175 * WARNING: We extract the base using the leaf element
176 * type but this could be an internal node. The
177 * base is the same either way.
179 * However, due to the rebalancing operation the
180 * cursor position may have exceeded the right-hand
183 * WARNING: See warnings in hammer_unlock_cursor()
186 elm
= &cursor
.node
->ondisk
->elms
[cursor
.index
].leaf
;
187 rebal
->key_cur
= elm
->base
;
188 ++rebal
->stat_ncount
;
190 while (hammer_flusher_meta_halflimit(trans
->hmp
) ||
191 hammer_flusher_undo_exhausted(trans
, 2)) {
192 hammer_unlock_cursor(&cursor
);
193 hammer_flusher_wait(trans
->hmp
, seq
);
194 hammer_lock_cursor(&cursor
);
195 seq
= hammer_flusher_async_one(trans
->hmp
);
199 * Before iterating check if the rebalance operation caused
200 * the cursor to index past the right-hand boundary and make
201 * sure to stop if it does. Otherwise the iteration may
202 * panic e.g. due to the key maxing out its fields and no
203 * longer being within the strict bounds of the root node.
205 if (hammer_btree_cmp(&rebal
->key_cur
, &cursor
.key_end
) > 0) {
206 rebal
->key_cur
= cursor
.key_end
;
211 * Iterate, stop if a signal was received.
213 if ((error
= hammer_signal_check(trans
->hmp
)) != 0)
215 error
= hammer_btree_iterate(&cursor
);
219 hammer_done_cursor(&cursor
);
220 if (error
== EDEADLK
) {
221 ++rebal
->stat_collisions
;
224 if (error
== EINTR
) {
225 rebal
->head
.flags
|= HAMMER_IOC_HEAD_INTR
;
229 rebal
->key_cur
.localization
&= HAMMER_LOCALIZE_MASK
;
230 hammer_btree_lcache_free(trans
->hmp
, &lcache
);
235 * Rebalance an internal node, called via a trailing upward recursion.
236 * All the children have already been individually rebalanced.
238 * To rebalance we scan the elements in the children and pack them,
239 * so we actually need to lock the children and the children's children.
243 * C C C C C C C children (first level) (internal or leaf nodes)
244 * children's elements (second level)
246 * <<<---------- pack children's elements, possibly remove excess
247 * children after packing.
249 * NOTE: The mirror_tids, parent pointers, and child pointers must be updated.
250 * Any live tracked B-Tree nodes must be updated (we worm out of that
251 * by not allowing any). And boundary elements must be preserved.
253 * NOTE: If the children are leaf nodes we may have a degenerate case
254 * case where there are no elements in the leafs.
259 rebalance_node(struct hammer_ioc_rebalance
*rebal
, hammer_cursor_t cursor
,
260 hammer_node_lock_t lcache
)
262 struct hammer_node_lock lockroot
;
263 hammer_node_lock_t base_item
;
264 hammer_node_lock_t chld_item
;
265 hammer_node_lock_t item
;
266 hammer_btree_elm_t elm
;
269 uint8_t type1 __debugvar
;
279 * Lock the parent node via the cursor, collect and lock our
280 * children and children's children.
282 * By the way, this is a LOT of locks.
284 hammer_node_lock_init(&lockroot
, cursor
->node
);
285 error
= hammer_cursor_upgrade(cursor
);
288 error
= hammer_btree_lock_children(cursor
, 2, &lockroot
, lcache
);
293 * Make a copy of all the locked on-disk data to simplify the element
294 * shifting we are going to have to do. We will modify the copy
297 hammer_btree_lock_copy(cursor
, &lockroot
);
300 * Look at the first child node.
302 if (TAILQ_FIRST(&lockroot
.list
) == NULL
)
304 type1
= TAILQ_FIRST(&lockroot
.list
)->node
->ondisk
->type
;
307 * Figure out the total number of children's children and
308 * calculate the average number of elements per child.
310 * The minimum avg_elms is 1 when count > 0. avg_elms * root_elms
311 * is always greater or equal to count.
313 * If count == 0 we hit a degenerate case which will cause
314 * avg_elms to also calculate as 0.
316 if (hammer_debug_general
& 0x1000)
317 hdkprintf("lockroot %p count %d\n", &lockroot
, lockroot
.count
);
319 TAILQ_FOREACH(item
, &lockroot
.list
, entry
) {
320 if (hammer_debug_general
& 0x1000)
321 hdkprintf("add count %d\n", item
->count
);
322 count
+= item
->count
;
323 KKASSERT(item
->node
->ondisk
->type
== type1
);
325 avg_elms
= (count
+ (lockroot
.count
- 1)) / lockroot
.count
;
326 KKASSERT(avg_elms
>= 0);
329 * If the average number of elements per child is too low then
330 * calculate the desired number of children (n) such that the
331 * average number of elements is reasonable.
333 * If the desired number of children is 1 then avg_elms will
334 * wind up being count, which may still be smaller then saturation
337 if (count
&& avg_elms
< rebal
->saturation
) {
338 n
= (count
+ (rebal
->saturation
- 1)) / rebal
->saturation
;
339 avg_elms
= (count
+ (n
- 1)) / n
;
343 * Pack the elements in the children. Elements for each item is
344 * packed into base_item until avg_elms is reached, then base_item
347 * hammer_cursor_moved_element() is called for each element moved
348 * to update tracked cursors, including the index beyond the last
349 * element (at count).
351 * Any cursors tracking the internal node itself must also be
352 * updated, potentially repointing them at a leaf and clearing
355 base_item
= TAILQ_FIRST(&lockroot
.list
);
359 TAILQ_FOREACH(item
, &lockroot
.list
, entry
) {
361 KKASSERT(item
->count
== node
->ondisk
->count
);
362 chld_item
= TAILQ_FIRST(&item
->list
);
363 for (i
= 0; i
< item
->count
; ++i
) {
365 * Closeout. If the next element is at index 0
366 * just use the existing separator in the parent.
368 if (base_count
== avg_elms
) {
370 elm
= &lockroot
.node
->ondisk
->elms
[
373 elm
= &node
->ondisk
->elms
[i
];
375 rebalance_closeout(base_item
, base_count
, elm
);
376 base_item
= TAILQ_NEXT(base_item
, entry
);
383 * Check degenerate no-work case. Otherwise pack
386 * All changes are made to the copy.
388 if (item
== base_item
&& i
== base_count
) {
391 chld_item
= TAILQ_NEXT(chld_item
, entry
);
398 elm
= &base_item
->copy
->elms
[base_count
];
399 *elm
= node
->ondisk
->elms
[i
];
400 base_item
->flags
|= HAMMER_NODE_LOCK_UPDATED
;
403 * Adjust the mirror_tid of the target and the
404 * internal element linkage.
406 * The parent node (lockroot.node) should already
407 * have an aggregate mirror_tid so we do not have
408 * to update that. However, it is possible for us
409 * to catch a hammer_btree_mirror_propagate() with
410 * its pants down. Update the parent if necessary.
412 tid
= node
->ondisk
->mirror_tid
;
414 if (base_item
->copy
->mirror_tid
< tid
) {
415 base_item
->copy
->mirror_tid
= tid
;
416 if (lockroot
.copy
->mirror_tid
< tid
) {
417 lockroot
.copy
->mirror_tid
= tid
;
419 HAMMER_NODE_LOCK_UPDATED
;
421 if (lockroot
.copy
->elms
[root_count
].
422 internal
.mirror_tid
< tid
) {
423 lockroot
.copy
->elms
[root_count
].
424 internal
.mirror_tid
= tid
;
426 HAMMER_NODE_LOCK_UPDATED
;
428 base_item
->flags
|= HAMMER_NODE_LOCK_UPDATED
;
432 * We moved elm. The parent pointers for any
433 * children of elm must be repointed.
435 if (item
!= base_item
&&
436 node
->ondisk
->type
== HAMMER_BTREE_TYPE_INTERNAL
) {
438 rebalance_parent_ptrs(base_item
, base_count
,
441 hammer_cursor_moved_element(item
->parent
->node
,
448 chld_item
= TAILQ_NEXT(chld_item
, entry
);
452 * Always call at the end (i == number of elements) in
453 * case a cursor is sitting indexed there.
455 hammer_cursor_moved_element(item
->parent
->node
, item
->index
,
457 base_item
->node
, base_count
);
461 * Packing complete, close-out base_item using the right-hand
462 * boundary of the original parent.
464 * If we will be deleting nodes from the root shift the old
465 * right-hand-boundary to the new ending index.
467 elm
= &lockroot
.node
->ondisk
->elms
[lockroot
.node
->ondisk
->count
];
468 rebalance_closeout(base_item
, base_count
, elm
);
470 if (lockroot
.copy
->count
!= root_count
) {
471 lockroot
.copy
->count
= root_count
;
472 lockroot
.copy
->elms
[root_count
] = *elm
;
473 lockroot
.flags
|= HAMMER_NODE_LOCK_UPDATED
;
477 * Any extra items beyond base_item are now completely empty and
478 * can be destroyed. Queue the destruction up in the copy. Note
479 * that none of the destroyed nodes are part of our cursor.
481 * The cursor is locked so it isn't on the tracking list. It
482 * should have been pointing at the boundary element (at root_count).
483 * When deleting elements from the root (which is cursor.node), we
484 * have to update the cursor.index manually to keep it in bounds.
486 while ((base_item
= TAILQ_NEXT(base_item
, entry
)) != NULL
) {
487 hammer_cursor_removed_node(base_item
->node
, lockroot
.node
,
489 hammer_cursor_deleted_element(lockroot
.node
, base_count
);
490 base_item
->copy
->type
= HAMMER_BTREE_TYPE_DELETED
;
491 base_item
->copy
->count
= 0;
492 base_item
->flags
|= HAMMER_NODE_LOCK_UPDATED
;
493 if (cursor
->index
> lockroot
.copy
->count
)
495 ++rebal
->stat_deletions
;
499 * All done, sync the locked child tree to disk. This will also
500 * flush and delete deleted nodes.
502 rebal
->stat_nrebal
+= hammer_btree_sync_copy(cursor
, &lockroot
);
504 hammer_btree_unlock_children(cursor
->trans
->hmp
, &lockroot
, lcache
);
505 hammer_cursor_downgrade(cursor
);
510 * Close-out the child base_item. This node contains base_count
513 * If the node is an internal node the right-hand boundary must be
518 rebalance_closeout(hammer_node_lock_t base_item
, int base_count
,
519 hammer_btree_elm_t elm
)
521 hammer_node_lock_t parent
;
522 hammer_btree_elm_t base_elm
;
523 hammer_btree_elm_t rbound_elm
;
527 * Update the count. NOTE: base_count can be 0 for the
528 * degenerate leaf case.
530 if (hammer_debug_general
& 0x1000) {
531 hdkprintf("%016jx:", (intmax_t)base_item
->node
->node_offset
);
533 if (base_item
->copy
->count
!= base_count
) {
534 base_item
->flags
|= HAMMER_NODE_LOCK_UPDATED
;
535 base_item
->copy
->count
= base_count
;
536 if (hammer_debug_general
& 0x1000)
537 kprintf(" (count update)");
541 * If we are closing out an internal node we must assign
542 * a right-hand boundary. Use the element contents as the
543 * right-hand boundary.
545 * Internal nodes are required to have at least one child,
546 * otherwise the left and right boundary would end up being
547 * the same element. Only leaf nodes can be empty.
549 * Rebalancing may cut-off an internal node such that the
550 * new right hand boundary is the next element anyway, but
551 * we still have to make sure that subtree_offset, btype,
552 * and mirror_tid are all 0.
554 if (base_item
->copy
->type
== HAMMER_BTREE_TYPE_INTERNAL
) {
555 KKASSERT(base_count
!= 0);
556 base_elm
= &base_item
->copy
->elms
[base_count
];
558 if (bcmp(base_elm
, elm
, sizeof(*elm
)) != 0 ||
559 elm
->internal
.subtree_offset
||
560 elm
->internal
.mirror_tid
||
563 base_elm
->internal
.subtree_offset
= 0;
564 base_elm
->internal
.mirror_tid
= 0;
565 base_elm
->base
.btype
= 0;
566 base_item
->flags
|= HAMMER_NODE_LOCK_UPDATED
;
567 if (hammer_debug_general
& 0x1000)
568 kprintf(" (rhs update)");
570 if (hammer_debug_general
& 0x1000)
571 kprintf(" (rhs same)");
576 * The parent's boundary must be updated. Be careful to retain
577 * the btype and non-base internal fields as that information is
580 parent
= base_item
->parent
;
581 rbound_elm
= &parent
->copy
->elms
[base_item
->index
+ 1];
582 if (bcmp(&rbound_elm
->base
, &elm
->base
, sizeof(elm
->base
)) != 0) {
583 save
= rbound_elm
->base
.btype
;
584 rbound_elm
->base
= elm
->base
;
585 rbound_elm
->base
.btype
= save
;
586 parent
->flags
|= HAMMER_NODE_LOCK_UPDATED
;
587 if (hammer_debug_general
& 0x1000) {
588 kprintf(" (parent bound update %d)",
589 base_item
->index
+ 1);
592 if (hammer_debug_general
& 0x1000)
597 * An element in item has moved to base_item. We must update the parent
598 * pointer of the node the element points to (which is chld_item).
602 rebalance_parent_ptrs(hammer_node_lock_t base_item
, int index
,
603 hammer_node_lock_t item
, hammer_node_lock_t chld_item
)
605 KKASSERT(chld_item
->node
->ondisk
->parent
== item
->node
->node_offset
);
606 chld_item
->copy
->parent
= base_item
->node
->node_offset
;
607 chld_item
->flags
|= HAMMER_NODE_LOCK_UPDATED
;
608 hammer_cursor_parent_changed(chld_item
->node
,
609 item
->node
, base_item
->node
, index
);