/* Generic associative array implementation. * * See Documentation/core-api/assoc_array.rst for information. * * Copyright (C) 2013 Red Hat, Inc. All Rights Reserved. * Written by David Howells (dhowells@redhat.com) * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public Licence * as published by the Free Software Foundation; either version * 2 of the Licence, or (at your option) any later version. */ //#define DEBUG #include <linux/rcupdate.h> #include <linux/slab.h> #include <linux/err.h> #include <linux/assoc_array_priv.h> /* * Iterate over an associative array. The caller must hold the RCU read lock * or better. */ static int assoc_array_subtree_iterate(const struct assoc_array_ptr *root, const struct assoc_array_ptr *stop, int (*iterator)(const void *leaf, void *iterator_data), void *iterator_data) { const struct assoc_array_shortcut *shortcut; const struct assoc_array_node *node; const struct assoc_array_ptr *cursor, *ptr, *parent; unsigned long has_meta; int slot, ret; cursor = root; begin_node: if (assoc_array_ptr_is_shortcut(cursor)) { /* Descend through a shortcut */ shortcut = assoc_array_ptr_to_shortcut(cursor); smp_read_barrier_depends(); cursor = READ_ONCE(shortcut->next_node); } node = assoc_array_ptr_to_node(cursor); smp_read_barrier_depends(); slot = 0; /* We perform two passes of each node. * * The first pass does all the leaves in this node. This means we * don't miss any leaves if the node is split up by insertion whilst * we're iterating over the branches rooted here (we may, however, see * some leaves twice). */ has_meta = 0; for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) { ptr = READ_ONCE(node->slots[slot]); has_meta |= (unsigned long)ptr; if (ptr && assoc_array_ptr_is_leaf(ptr)) { /* We need a barrier between the read of the pointer * and dereferencing the pointer - but only if we are * actually going to dereference it. */ smp_read_barrier_depends(); /* Invoke the callback */ ret = iterator(assoc_array_ptr_to_leaf(ptr), iterator_data); if (ret) return ret; } } /* The second pass attends to all the metadata pointers. If we follow * one of these we may find that we don't come back here, but rather go * back to a replacement node with the leaves in a different layout. * * We are guaranteed to make progress, however, as the slot number for * a particular portion of the key space cannot change - and we * continue at the back pointer + 1. */ if (!(has_meta & ASSOC_ARRAY_PTR_META_TYPE)) goto finished_node; slot = 0; continue_node: node = assoc_array_ptr_to_node(cursor); smp_read_barrier_depends(); for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) { ptr = READ_ONCE(node->slots[slot]); if (assoc_array_ptr_is_meta(ptr)) { cursor = ptr; goto begin_node; } } finished_node: /* Move up to the parent (may need to skip back over a shortcut) */ parent = READ_ONCE(node->back_pointer); slot = node->parent_slot; if (parent == stop) return 0; if (assoc_array_ptr_is_shortcut(parent)) { shortcut = assoc_array_ptr_to_shortcut(parent); smp_read_barrier_depends(); cursor = parent; parent = READ_ONCE(shortcut->back_pointer); slot = shortcut->parent_slot; if (parent == stop) return 0; } /* Ascend to next slot in parent node */ cursor = parent; slot++; goto continue_node; } /** * assoc_array_iterate - Pass all objects in the array to a callback * @array: The array to iterate over. * @iterator: The callback function. * @iterator_data: Private data for the callback function. * * Iterate over all the objects in an associative array. Each one will be * presented to the iterator function. * * If the array is being modified concurrently with the iteration then it is * possible that some objects in the array will be passed to the iterator * callback more than once - though every object should be passed at least * once. If this is undesirable then the caller must lock against modification * for the duration of this function. * * The function will return 0 if no objects were in the array or else it will * return the result of the last iterator function called. Iteration stops * immediately if any call to the iteration function results in a non-zero * return. * * The caller should hold the RCU read lock or better if concurrent * modification is possible. */ int assoc_array_iterate(const struct assoc_array *array, int (*iterator)(const void *object, void *iterator_data), void *iterator_data) { struct assoc_array_ptr *root = READ_ONCE(array->root); if (!root) return 0; return assoc_array_subtree_iterate(root, NULL, iterator, iterator_data); } enum assoc_array_walk_status { assoc_array_walk_tree_empty, assoc_array_walk_found_terminal_node, assoc_array_walk_found_wrong_shortcut, }; struct assoc_array_walk_result { struct { struct assoc_array_node *node; /* Node in which leaf might be found */ int level; int slot; } terminal_node; struct { struct assoc_array_shortcut *shortcut; int level; int sc_level; unsigned long sc_segments; unsigned long dissimilarity; } wrong_shortcut; }; /* * Navigate through the internal tree looking for the closest node to the key. */ static enum assoc_array_walk_status assoc_array_walk(const struct assoc_array *array, const struct assoc_array_ops *ops, const void *index_key, struct assoc_array_walk_result *result) { struct assoc_array_shortcut *shortcut; struct assoc_array_node *node; struct assoc_array_ptr *cursor, *ptr; unsigned long sc_segments, dissimilarity; unsigned long segments; int level, sc_level, next_sc_level; int slot; pr_devel("-->%s()\n", __func__); cursor = READ_ONCE(array->root); if (!cursor) return assoc_array_walk_tree_empty; level = 0; /* Use segments from the key for the new leaf to navigate through the * internal tree, skipping through nodes and shortcuts that are on * route to the destination. Eventually we'll come to a slot that is * either empty or contains a leaf at which point we've found a node in * which the leaf we're looking for might be found or into which it * should be inserted. */ jumped: segments = ops->get_key_chunk(index_key, level); pr_devel("segments[%d]: %lx\n", level, segments); if (assoc_array_ptr_is_shortcut(cursor)) goto follow_shortcut; consider_node: node = assoc_array_ptr_to_node(cursor); smp_read_barrier_depends(); slot = segments >> (level & ASSOC_ARRAY_KEY_CHUNK_MASK); slot &= ASSOC_ARRAY_FAN_MASK; ptr = READ_ONCE(node->slots[slot]); pr_devel("consider slot %x [ix=%d type=%lu]\n", slot, level, (unsigned long)ptr & 3); if (!assoc_array_ptr_is_meta(ptr)) { /* The node doesn't have a node/shortcut pointer in the slot * corresponding to the index key that we have to follow. */ result->terminal_node.node = node; result->terminal_node.level = level; result->terminal_node.slot = slot; pr_devel("<--%s() = terminal_node\n", __func__); return assoc_array_walk_found_terminal_node; } if (assoc_array_ptr_is_node(ptr)) { /* There is a pointer to a node in the slot corresponding to * this index key segment, so we need to follow it. */ cursor = ptr; level += ASSOC_ARRAY_LEVEL_STEP; if ((level & ASSOC_ARRAY_KEY_CHUNK_MASK) != 0) goto consider_node; goto jumped; } /* There is a shortcut in the slot corresponding to the index key * segment. We follow the shortcut if its partial index key matches * this leaf's. Otherwise we need to split the shortcut. */ cursor = ptr; follow_shortcut: shortcut = assoc_array_ptr_to_shortcut(cursor); smp_read_barrier_depends(); pr_devel("shortcut to %d\n", shortcut->skip_to_level); sc_level = level + ASSOC_ARRAY_LEVEL_STEP; BUG_ON(sc_level > shortcut->skip_to_level); do { /* Check the leaf against the shortcut's index key a word at a * time, trimming the final word (the shortcut stores the index * key completely from the root to the shortcut's target). */ if ((sc_level & ASSOC_ARRAY_KEY_CHUNK_MASK) == 0) segments = ops->get_key_chunk(index_key, sc_level); sc_segments = shortcut->index_key[sc_level >> ASSOC_ARRAY_KEY_CHUNK_SHIFT]; dissimilarity = segments ^ sc_segments; if (round_up(sc_level, ASSOC_ARRAY_KEY_CHUNK_SIZE) > shortcut->skip_to_level) { /* Trim segments that are beyond the shortcut */ int shift = shortcut->skip_to_level & ASSOC_ARRAY_KEY_CHUNK_MASK; dissimilarity &= ~(ULONG_MAX << shift); next_sc_level = shortcut->skip_to_level; } else { next_sc_level = sc_level + ASSOC_ARRAY_KEY_CHUNK_SIZE; next_sc_level = round_down(next_sc_level, ASSOC_ARRAY_KEY_CHUNK_SIZE); } if (dissimilarity != 0) { /* This shortcut points elsewhere */ result->wrong_shortcut.shortcut = shortcut; result->wrong_shortcut.level = level; result->wrong_shortcut.sc_level = sc_level; result->wrong_shortcut.sc_segments = sc_segments; result->wrong_shortcut.dissimilarity = dissimilarity; return assoc_array_walk_found_wrong_shortcut; } sc_level = next_sc_level; } while (sc_level < shortcut->skip_to_level); /* The shortcut matches the leaf's index to this point. */ cursor = READ_ONCE(shortcut->next_node); if (((level ^ sc_level) & ~ASSOC_ARRAY_KEY_CHUNK_MASK) != 0) { level = sc_level; goto jumped; } else { level = sc_level; goto consider_node; } } /** * assoc_array_find - Find an object by index key * @array: The associative array to search. * @ops: The operations to use. * @index_key: The key to the object. * * Find an object in an associative array by walking through the internal tree * to the node that should contain the object and then searching the leaves * there. NULL is returned if the requested object was not found in the array. * * The caller must hold the RCU read lock or better. */ void *assoc_array_find(const struct assoc_array *array, const struct assoc_array_ops *ops, const void *index_key) { struct assoc_array_walk_result result; const struct assoc_array_node *node; const struct assoc_array_ptr *ptr; const void *leaf; int slot; if (assoc_array_walk(array, ops, index_key, &result) != assoc_array_walk_found_terminal_node) return NULL; node = result.terminal_node.node; smp_read_barrier_depends(); /* If the target key is available to us, it's has to be pointed to by * the terminal node. */ for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) { ptr = READ_ONCE(node->slots[slot]); if (ptr && assoc_array_ptr_is_leaf(ptr)) { /* We need a barrier between the read of the pointer * and dereferencing the pointer - but only if we are * actually going to dereference it. */ leaf = assoc_array_ptr_to_leaf(ptr); smp_read_barrier_depends(); if (ops->compare_object(leaf, index_key)) return (void *)leaf; } } return NULL; } /* * Destructively iterate over an associative array. The caller must prevent * other simultaneous accesses. */ static void assoc_array_destroy_subtree(struct assoc_array_ptr *root, const struct assoc_array_ops *ops) { struct assoc_array_shortcut *shortcut; struct assoc_array_node *node; struct assoc_array_ptr *cursor, *parent = NULL; int slot = -1; pr_devel("-->%s()\n", __func__); cursor = root; if (!cursor) { pr_devel("empty\n"); return; } move_to_meta: if (assoc_array_ptr_is_shortcut(cursor)) { /* Descend through a shortcut */ pr_devel("[%d] shortcut\n", slot); BUG_ON(!assoc_array_ptr_is_shortcut(cursor)); shortcut = assoc_array_ptr_to_shortcut(cursor); BUG_ON(shortcut->back_pointer != parent); BUG_ON(slot != -1 && shortcut->parent_slot != slot); parent = cursor; cursor = shortcut->next_node; slot = -1; BUG_ON(!assoc_array_ptr_is_node(cursor)); } pr_devel("[%d] node\n", slot); node = assoc_array_ptr_to_node(cursor); BUG_ON(node->back_pointer != parent); BUG_ON(slot != -1 && node->parent_slot != slot); slot = 0; continue_node: pr_devel("Node %p [back=%p]\n", node, node->back_pointer); for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) { struct assoc_array_ptr *ptr = node->slots[slot]; if (!ptr) continue; if (assoc_array_ptr_is_meta(ptr)) { parent = cursor; cursor = ptr; goto move_to_meta; } if (ops) { pr_devel("[%d] free leaf\n", slot); ops->free_object(assoc_array_ptr_to_leaf(ptr)); } } parent = node->back_pointer; slot = node->parent_slot; pr_devel("free node\n"); kfree(node); if (!parent) return; /* Done */ /* Move back up to the parent (may need to free a shortcut on * the way up) */ if (assoc_array_ptr_is_shortcut(parent)) { shortcut = assoc_array_ptr_to_shortcut(parent); BUG_ON(shortcut->next_node != cursor); cursor = parent; parent = shortcut->back_pointer; slot = shortcut->parent_slot; pr_devel("free shortcut\n"); kfree(shortcut); if (!parent) return; BUG_ON(!assoc_array_ptr_is_node(parent)); } /* Ascend to next slot in parent node */ pr_devel("ascend to %p[%d]\n", parent, slot); cursor = parent; node = assoc_array_ptr_to_node(cursor); slot++; goto continue_node; } /** * assoc_array_destroy - Destroy an associative array * @array: The array to destroy. * @ops: The operations to use. * * Discard all metadata and free all objects in an associative array. The * array will be empty and ready to use again upon completion. This function * cannot fail. * * The caller must prevent all other accesses whilst this takes place as no * attempt is made to adjust pointers gracefully to permit RCU readlock-holding * accesses to continue. On the other hand, no memory allocation is required. */ void assoc_array_destroy(struct assoc_array *array, const struct assoc_array_ops *ops) { assoc_array_destroy_subtree(array->root, ops); array->root = NULL; } /* * Handle insertion into an empty tree. */ static bool assoc_array_insert_in_empty_tree(struct assoc_array_edit *edit) { struct assoc_array_node *new_n0; pr_devel("-->%s()\n", __func__); new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL); if (!new_n0) return false; edit->new_meta[0] = assoc_array_node_to_ptr(new_n0); edit->leaf_p = &new_n0->slots[0]; edit->adjust_count_on = new_n0; edit->set[0].ptr = &edit->array->root; edit->set[0].to = assoc_array_node_to_ptr(new_n0); pr_devel("<--%s() = ok [no root]\n", __func__); return true; } /* * Handle insertion into a terminal node. */ static bool assoc_array_insert_into_terminal_node(struct assoc_array_edit *edit, const struct assoc_array_ops *ops, const void *index_key, struct assoc_array_walk_result *result) { struct assoc_array_shortcut *shortcut, *new_s0; struct assoc_array_node *node, *new_n0, *new_n1, *side; struct assoc_array_ptr *ptr; unsigned long dissimilarity, base_seg, blank; size_t keylen; bool have_meta; int level, diff; int slot, next_slot, free_slot, i, j; node = result->terminal_node.node; level = result->terminal_node.level; edit->segment_cache[ASSOC_ARRAY_FAN_OUT] = result->terminal_node.slot; pr_devel("-->%s()\n", __func__); /* We arrived at a node which doesn't have an onward node or shortcut * pointer that we have to follow. This means that (a) the leaf we * want must go here (either by insertion or replacement) or (b) we * need to split this node and insert in one of the fragments. */ free_slot = -1; /* Firstly, we have to check the leaves in this node to see if there's * a matching one we should replace in place. */ for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { ptr = node->slots[i]; if (!ptr) { free_slot = i; continue; } if (assoc_array_ptr_is_leaf(ptr) && ops->compare_object(assoc_array_ptr_to_leaf(ptr), index_key)) { pr_devel("replace in slot %d\n", i); edit->leaf_p = &node->slots[i]; edit->dead_leaf = node->slots[i]; pr_devel("<--%s() = ok [replace]\n", __func__); return true; } } /* If there is a free slot in this node then we can just insert the * leaf here. */ if (free_slot >= 0) { pr_devel("insert in free slot %d\n", free_slot); edit->leaf_p = &node->slots[free_slot]; edit->adjust_count_on = node; pr_devel("<--%s() = ok [insert]\n", __func__); return true; } /* The node has no spare slots - so we're either going to have to split * it or insert another node before it. * * Whatever, we're going to need at least two new nodes - so allocate * those now. We may also need a new shortcut, but we deal with that * when we need it. */ new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL); if (!new_n0) return false; edit->new_meta[0] = assoc_array_node_to_ptr(new_n0); new_n1 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL); if (!new_n1) return false; edit->new_meta[1] = assoc_array_node_to_ptr(new_n1); /* We need to find out how similar the leaves are. */ pr_devel("no spare slots\n"); have_meta = false; for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { ptr = node->slots[i]; if (assoc_array_ptr_is_meta(ptr)) { edit->segment_cache[i] = 0xff; have_meta = true; continue; } base_seg = ops->get_object_key_chunk( assoc_array_ptr_to_leaf(ptr), level); base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK; edit->segment_cache[i] = base_seg & ASSOC_ARRAY_FAN_MASK; } if (have_meta) { pr_devel("have meta\n"); goto split_node; } /* The node contains only leaves */ dissimilarity = 0; base_seg = edit->segment_cache[0]; for (i = 1; i < ASSOC_ARRAY_FAN_OUT; i++) dissimilarity |= edit->segment_cache[i] ^ base_seg; pr_devel("only leaves; dissimilarity=%lx\n", dissimilarity); if ((dissimilarity & ASSOC_ARRAY_FAN_MASK) == 0) { /* The old leaves all cluster in the same slot. We will need * to insert a shortcut if the new node wants to cluster with them. */ if ((edit->segment_cache[ASSOC_ARRAY_FAN_OUT] ^ base_seg) == 0) goto all_leaves_cluster_together; /* Otherwise all the old leaves cluster in the same slot, but * the new leaf wants to go into a different slot - so we * create a new node (n0) to hold the new leaf and a pointer to * a new node (n1) holding all the old leaves. * * This can be done by falling through to the node splitting * path. */ pr_devel("present leaves cluster but not new leaf\n"); } split_node: pr_devel("split node\n"); /* We need to split the current node. The node must contain anything * from a single leaf (in the one leaf case, this leaf will cluster * with the new leaf) and the rest meta-pointers, to all leaves, some * of which may cluster. * * It won't contain the case in which all the current leaves plus the * new leaves want to cluster in the same slot. * * We need to expel at least two leaves out of a set consisting of the * leaves in the node and the new leaf. The current meta pointers can * just be copied as they shouldn't cluster with any of the leaves. * * We need a new node (n0) to replace the current one and a new node to * take the expelled nodes (n1). */ edit->set[0].to = assoc_array_node_to_ptr(new_n0); new_n0->back_pointer = node->back_pointer; new_n0->parent_slot = node->parent_slot; new_n1->back_pointer = assoc_array_node_to_ptr(new_n0); new_n1->parent_slot = -1; /* Need to calculate this */ do_split_node: pr_devel("do_split_node\n"); new_n0->nr_leaves_on_branch = node->nr_leaves_on_branch; new_n1->nr_leaves_on_branch = 0; /* Begin by finding two matching leaves. There have to be at least two * that match - even if there are meta pointers - because any leaf that * would match a slot with a meta pointer in it must be somewhere * behind that meta pointer and cannot be here. Further, given N * remaining leaf slots, we now have N+1 leaves to go in them. */ for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { slot = edit->segment_cache[i]; if (slot != 0xff) for (j = i + 1; j < ASSOC_ARRAY_FAN_OUT + 1; j++) if (edit->segment_cache[j] == slot) goto found_slot_for_multiple_occupancy; } found_slot_for_multiple_occupancy: pr_devel("same slot: %x %x [%02x]\n", i, j, slot); BUG_ON(i >= ASSOC_ARRAY_FAN_OUT); BUG_ON(j >= ASSOC_ARRAY_FAN_OUT + 1); BUG_ON(slot >= ASSOC_ARRAY_FAN_OUT); new_n1->parent_slot = slot; /* Metadata pointers cannot change slot */ for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) if (assoc_array_ptr_is_meta(node->slots[i])) new_n0->slots[i] = node->slots[i]; else new_n0->slots[i] = NULL; BUG_ON(new_n0->slots[slot] != NULL); new_n0->slots[slot] = assoc_array_node_to_ptr(new_n1); /* Filter the leaf pointers between the new nodes */ free_slot = -1; next_slot = 0; for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { if (assoc_array_ptr_is_meta(node->slots[i])) continue; if (edit->segment_cache[i] == slot) { new_n1->slots[next_slot++] = node->slots[i]; new_n1->nr_leaves_on_branch++; } else { do { free_slot++; } while (new_n0->slots[free_slot] != NULL); new_n0->slots[free_slot] = node->slots[i]; } } pr_devel("filtered: f=%x n=%x\n", free_slot, next_slot); if (edit->segment_cache[ASSOC_ARRAY_FAN_OUT] != slot) { do { free_slot++; } while (new_n0->slots[free_slot] != NULL); edit->leaf_p = &new_n0->slots[free_slot]; edit->adjust_count_on = new_n0; } else { edit->leaf_p = &new_n1->slots[next_slot++]; edit->adjust_count_on = new_n1; } BUG_ON(next_slot <= 1); edit->set_backpointers_to = assoc_array_node_to_ptr(new_n0); for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { if (edit->segment_cache[i] == 0xff) { ptr = node->slots[i]; BUG_ON(assoc_array_ptr_is_leaf(ptr)); if (assoc_array_ptr_is_node(ptr)) { side = assoc_array_ptr_to_node(ptr); edit->set_backpointers[i] = &side->back_pointer; } else { shortcut = assoc_array_ptr_to_shortcut(ptr); edit->set_backpointers[i] = &shortcut->back_pointer; } } } ptr = node->back_pointer; if (!ptr) edit->set[0].ptr = &edit->array->root; else if (assoc_array_ptr_is_node(ptr)) edit->set[0].ptr = &assoc_array_ptr_to_node(ptr)->slots[node->parent_slot]; else edit->set[0].ptr = &assoc_array_ptr_to_shortcut(ptr)->next_node; edit->excised_meta[0] = assoc_array_node_to_ptr(node); pr_devel("<--%s() = ok [split node]\n", __func__); return true; all_leaves_cluster_together: /* All the leaves, new and old, want to cluster together in this node * in the same slot, so we have to replace this node with a shortcut to * skip over the identical parts of the key and then place a pair of * nodes, one inside the other, at the end of the shortcut and * distribute the keys between them. * * Firstly we need to work out where the leaves start diverging as a * bit position into their keys so that we know how big the shortcut * needs to be. * * We only need to make a single pass of N of the N+1 leaves because if * any keys differ between themselves at bit X then at least one of * them must also differ with the base key at bit X or before. */ pr_devel("all leaves cluster together\n"); diff = INT_MAX; for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { int x = ops->diff_objects(assoc_array_ptr_to_leaf(node->slots[i]), index_key); if (x < diff) { BUG_ON(x < 0); diff = x; } } BUG_ON(diff == INT_MAX); BUG_ON(diff < level + ASSOC_ARRAY_LEVEL_STEP); keylen = round_up(diff, ASSOC_ARRAY_KEY_CHUNK_SIZE); keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT; new_s0 = kzalloc(sizeof(struct assoc_array_shortcut) + keylen * sizeof(unsigned long), GFP_KERNEL); if (!new_s0) return false; edit->new_meta[2] = assoc_array_shortcut_to_ptr(new_s0); edit->set[0].to = assoc_array_shortcut_to_ptr(new_s0); new_s0->back_pointer = node->back_pointer; new_s0->parent_slot = node->parent_slot; new_s0->next_node = assoc_array_node_to_ptr(new_n0); new_n0->back_pointer = assoc_array_shortcut_to_ptr(new_s0); new_n0->parent_slot = 0; new_n1->back_pointer = assoc_array_node_to_ptr(new_n0); new_n1->parent_slot = -1; /* Need to calculate this */ new_s0->skip_to_level = level = diff & ~ASSOC_ARRAY_LEVEL_STEP_MASK; pr_devel("skip_to_level = %d [diff %d]\n", level, diff); BUG_ON(level <= 0); for (i = 0; i < keylen; i++) new_s0->index_key[i] = ops->get_key_chunk(index_key, i * ASSOC_ARRAY_KEY_CHUNK_SIZE); blank = ULONG_MAX << (level & ASSOC_ARRAY_KEY_CHUNK_MASK); pr_devel("blank off [%zu] %d: %lx\n", keylen - 1, level, blank); new_s0->index_key[keylen - 1] &= ~blank; /* This now reduces to a node splitting exercise for which we'll need * to regenerate the disparity table. */ for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { ptr = node->slots[i]; base_seg = ops->get_object_key_chunk(assoc_array_ptr_to_leaf(ptr), level); base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK; edit->segment_cache[i] = base_seg & ASSOC_ARRAY_FAN_MASK; } base_seg = ops->get_key_chunk(index_key, level); base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK; edit->segment_cache[ASSOC_ARRAY_FAN_OUT] = base_seg & ASSOC_ARRAY_FAN_MASK; goto do_split_node; } /* * Handle insertion into the middle of a shortcut. */ static bool assoc_array_insert_mid_shortcut(struct assoc_array_edit *edit, const struct assoc_array_ops *ops, struct assoc_array_walk_result *result) { struct assoc_array_shortcut *shortcut, *new_s0, *new_s1; struct assoc_array_node *node, *new_n0, *side; unsigned long sc_segments, dissimilarity, blank; size_t keylen; int level, sc_level, diff; int sc_slot; shortcut = result->wrong_shortcut.shortcut; level = result->wrong_shortcut.level; sc_level = result->wrong_shortcut.sc_level; sc_segments = result->wrong_shortcut.sc_segments; dissimilarity = result->wrong_shortcut.dissimilarity; pr_devel("-->%s(ix=%d dis=%lx scix=%d)\n", __func__, level, dissimilarity, sc_level); /* We need to split a shortcut and insert a node between the two * pieces. Zero-length pieces will be dispensed with entirely. * * First of all, we need to find out in which level the first * difference was. */ diff = __ffs(dissimilarity); diff &= ~ASSOC_ARRAY_LEVEL_STEP_MASK; diff += sc_level & ~ASSOC_ARRAY_KEY_CHUNK_MASK; pr_devel("diff=%d\n", diff); if (!shortcut->back_pointer) { edit->set[0].ptr = &edit->array->root; } else if (assoc_array_ptr_is_node(shortcut->back_pointer)) { node = assoc_array_ptr_to_node(shortcut->back_pointer); edit->set[0].ptr = &node->slots[shortcut->parent_slot]; } else { BUG(); } edit->excised_meta[0] = assoc_array_shortcut_to_ptr(shortcut); /* Create a new node now since we're going to need it anyway */ new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL); if (!new_n0) return false; edit->new_meta[0] = assoc_array_node_to_ptr(new_n0); edit->adjust_count_on = new_n0; /* Insert a new shortcut before the new node if this segment isn't of * zero length - otherwise we just connect the new node directly to the * parent. */ level += ASSOC_ARRAY_LEVEL_STEP; if (diff > level) { pr_devel("pre-shortcut %d...%d\n", level, diff); keylen = round_up(diff, ASSOC_ARRAY_KEY_CHUNK_SIZE); keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT; new_s0 = kzalloc(sizeof(struct assoc_array_shortcut) + keylen * sizeof(unsigned long), GFP_KERNEL); if (!new_s0) return false; edit->new_meta[1] = assoc_array_shortcut_to_ptr(new_s0); edit->set[0].to = assoc_array_shortcut_to_ptr(new_s0); new_s0->back_pointer = shortcut->back_pointer; new_s0->parent_slot = shortcut->parent_slot; new_s0->next_node = assoc_array_node_to_ptr(new_n0); new_s0->skip_to_level = diff; new_n0->back_pointer = assoc_array_shortcut_to_ptr(new_s0); new_n0->parent_slot = 0; memcpy(new_s0->index_key, shortcut->index_key, keylen * sizeof(unsigned long)); blank = ULONG_MAX << (diff & ASSOC_ARRAY_KEY_CHUNK_MASK); pr_devel("blank off [%zu] %d: %lx\n", keylen - 1, diff, blank); new_s0->index_key[keylen - 1] &= ~blank; } else { pr_devel("no pre-shortcut\n"); edit->set[0].to = assoc_array_node_to_ptr(new_n0); new_n0->back_pointer = shortcut->back_pointer; new_n0->parent_slot = shortcut->parent_slot; } side = assoc_array_ptr_to_node(shortcut->next_node); new_n0->nr_leaves_on_branch = side->nr_leaves_on_branch; /* We need to know which slot in the new node is going to take a * metadata pointer. */ sc_slot = sc_segments >> (diff & ASSOC_ARRAY_KEY_CHUNK_MASK); sc_slot &= ASSOC_ARRAY_FAN_MASK; pr_devel("new slot %lx >> %d -> %d\n", sc_segments, diff & ASSOC_ARRAY_KEY_CHUNK_MASK, sc_slot); /* Determine whether we need to follow the new node with a replacement * for the current shortcut. We could in theory reuse the current * shortcut if its parent slot number doesn't change - but that's a * 1-in-16 chance so not worth expending the code upon. */ level = diff + ASSOC_ARRAY_LEVEL_STEP; if (level < shortcut->skip_to_level) { pr_devel("post-shortcut %d...%d\n", level, shortcut->skip_to_level); keylen = round_up(shortcut->skip_to_level, ASSOC_ARRAY_KEY_CHUNK_SIZE); keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT; new_s1 = kzalloc(sizeof(struct assoc_array_shortcut) + keylen * sizeof(unsigned long), GFP_KERNEL); if (!new_s1) return false; edit->new_meta[2] = assoc_array_shortcut_to_ptr(new_s1); new_s1->back_pointer = assoc_array_node_to_ptr(new_n0); new_s1->parent_slot = sc_slot; new_s1->next_node = shortcut->next_node; new_s1->skip_to_level = shortcut->skip_to_level; new_n0->slots[sc_slot] = assoc_array_shortcut_to_ptr(new_s1); memcpy(new_s1->index_key, shortcut->index_key, keylen * sizeof(unsigned long)); edit->set[1].ptr = &side->back_pointer; edit->set[1].to = assoc_array_shortcut_to_ptr(new_s1); } else { pr_devel("no post-shortcut\n"); /* We don't have to replace the pointed-to node as long as we * use memory barriers to make sure the parent slot number is * changed before the back pointer (the parent slot number is * irrelevant to the old parent shortcut). */ new_n0->slots[sc_slot] = shortcut->next_node; edit->set_parent_slot[0].p = &side->parent_slot; edit->set_parent_slot[0].to = sc_slot; edit->set[1].ptr = &side->back_pointer; edit->set[1].to = assoc_array_node_to_ptr(new_n0); } /* Install the new leaf in a spare slot in the new node. */ if (sc_slot == 0) edit->leaf_p = &new_n0->slots[1]; else edit->leaf_p = &new_n0->slots[0]; pr_devel("<--%s() = ok [split shortcut]\n", __func__); return edit; } /** * assoc_array_insert - Script insertion of an object into an associative array * @array: The array to insert into. * @ops: The operations to use. * @index_key: The key to insert at. * @object: The object to insert. * * Precalculate and preallocate a script for the insertion or replacement of an * object in an associative array. This results in an edit script that can * either be applied or cancelled. * * The function returns a pointer to an edit script or -ENOMEM. * * The caller should lock against other modifications and must continue to hold * the lock until assoc_array_apply_edit() has been called. * * Accesses to the tree may take place concurrently with this function, * provided they hold the RCU read lock. */ struct assoc_array_edit *assoc_array_insert(struct assoc_array *array, const struct assoc_array_ops *ops, const void *index_key, void *object) { struct assoc_array_walk_result result; struct assoc_array_edit *edit; pr_devel("-->%s()\n", __func__); /* The leaf pointer we're given must not have the bottom bit set as we * use those for type-marking the pointer. NULL pointers are also not * allowed as they indicate an empty slot but we have to allow them * here as they can be updated later. */ BUG_ON(assoc_array_ptr_is_meta(object)); edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL); if (!edit) return ERR_PTR(-ENOMEM); edit->array = array; edit->ops = ops; edit->leaf = assoc_array_leaf_to_ptr(object); edit->adjust_count_by = 1; switch (assoc_array_walk(array, ops, index_key, &result)) { case assoc_array_walk_tree_empty: /* Allocate a root node if there isn't one yet */ if (!assoc_array_insert_in_empty_tree(edit)) goto enomem; return edit; case assoc_array_walk_found_terminal_node: /* We found a node that doesn't have a node/shortcut pointer in * the slot corresponding to the index key that we have to * follow. */ if (!assoc_array_insert_into_terminal_node(edit, ops, index_key, &result)) goto enomem; return edit; case assoc_array_walk_found_wrong_shortcut: /* We found a shortcut that didn't match our key in a slot we * needed to follow. */ if (!assoc_array_insert_mid_shortcut(edit, ops, &result)) goto enomem; return edit; } enomem: /* Clean up after an out of memory error */ pr_devel("enomem\n"); assoc_array_cancel_edit(edit); return ERR_PTR(-ENOMEM); } /** * assoc_array_insert_set_object - Set the new object pointer in an edit script * @edit: The edit script to modify. * @object: The object pointer to set. * * Change the object to be inserted in an edit script. The object pointed to * by the old object is not freed. This must be done prior to applying the * script. */ void assoc_array_insert_set_object(struct assoc_array_edit *edit, void *object) { BUG_ON(!object); edit->leaf = assoc_array_leaf_to_ptr(object); } struct assoc_array_delete_collapse_context { struct assoc_array_node *node; const void *skip_leaf; int slot; }; /* * Subtree collapse to node iterator. */ static int assoc_array_delete_collapse_iterator(const void *leaf, void *iterator_data) { struct assoc_array_delete_collapse_context *collapse = iterator_data; if (leaf == collapse->skip_leaf) return 0; BUG_ON(collapse->slot >= ASSOC_ARRAY_FAN_OUT); collapse->node->slots[collapse->slot++] = assoc_array_leaf_to_ptr(leaf); return 0; } /** * assoc_array_delete - Script deletion of an object from an associative array * @array: The array to search. * @ops: The operations to use. * @index_key: The key to the object. * * Precalculate and preallocate a script for the deletion of an object from an * associative array. This results in an edit script that can either be * applied or cancelled. * * The function returns a pointer to an edit script if the object was found, * NULL if the object was not found or -ENOMEM. * * The caller should lock against other modifications and must continue to hold * the lock until assoc_array_apply_edit() has been called. * * Accesses to the tree may take place concurrently with this function, * provided they hold the RCU read lock. */ struct assoc_array_edit *assoc_array_delete(struct assoc_array *array, const struct assoc_array_ops *ops, const void *index_key) { struct assoc_array_delete_collapse_context collapse; struct assoc_array_walk_result result; struct assoc_array_node *node, *new_n0; struct assoc_array_edit *edit; struct assoc_array_ptr *ptr; bool has_meta; int slot, i; pr_devel("-->%s()\n", __func__); edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL); if (!edit) return ERR_PTR(-ENOMEM); edit->array = array; edit->ops = ops; edit->adjust_count_by = -1; switch (assoc_array_walk(array, ops, index_key, &result)) { case assoc_array_walk_found_terminal_node: /* We found a node that should contain the leaf we've been * asked to remove - *if* it's in the tree. */ pr_devel("terminal_node\n"); node = result.terminal_node.node; for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) { ptr = node->slots[slot]; if (ptr && assoc_array_ptr_is_leaf(ptr) && ops->compare_object(assoc_array_ptr_to_leaf(ptr), index_key)) goto found_leaf; } case assoc_array_walk_tree_empty: case assoc_array_walk_found_wrong_shortcut: default: assoc_array_cancel_edit(edit); pr_devel("not found\n"); return NULL; } found_leaf: BUG_ON(array->nr_leaves_on_tree <= 0); /* In the simplest form of deletion we just clear the slot and release * the leaf after a suitable interval. */ edit->dead_leaf = node->slots[slot]; edit->set[0].ptr = &node->slots[slot]; edit->set[0].to = NULL; edit->adjust_count_on = node; /* If that concludes erasure of the last leaf, then delete the entire * internal array. */ if (array->nr_leaves_on_tree == 1) { edit->set[1].ptr = &array->root; edit->set[1].to = NULL; edit->adjust_count_on = NULL; edit->excised_subtree = array->root; pr_devel("all gone\n"); return edit; } /* However, we'd also like to clear up some metadata blocks if we * possibly can. * * We go for a simple algorithm of: if this node has FAN_OUT or fewer * leaves in it, then attempt to collapse it - and attempt to * recursively collapse up the tree. * * We could also try and collapse in partially filled subtrees to take * up space in this node. */ if (node->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT + 1) { struct assoc_array_node *parent, *grandparent; struct assoc_array_ptr *ptr; /* First of all, we need to know if this node has metadata so * that we don't try collapsing if all the leaves are already * here. */ has_meta = false; for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { ptr = node->slots[i]; if (assoc_array_ptr_is_meta(ptr)) { has_meta = true; break; } } pr_devel("leaves: %ld [m=%d]\n", node->nr_leaves_on_branch - 1, has_meta); /* Look further up the tree to see if we can collapse this node * into a more proximal node too. */ parent = node; collapse_up: pr_devel("collapse subtree: %ld\n", parent->nr_leaves_on_branch); ptr = parent->back_pointer; if (!ptr) goto do_collapse; if (assoc_array_ptr_is_shortcut(ptr)) { struct assoc_array_shortcut *s = assoc_array_ptr_to_shortcut(ptr); ptr = s->back_pointer; if (!ptr) goto do_collapse; } grandparent = assoc_array_ptr_to_node(ptr); if (grandparent->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT + 1) { parent = grandparent; goto collapse_up; } do_collapse: /* There's no point collapsing if the original node has no meta * pointers to discard and if we didn't merge into one of that * node's ancestry. */ if (has_meta || parent != node) { node = parent; /* Create a new node to collapse into */ new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL); if (!new_n0) goto enomem; edit->new_meta[0] = assoc_array_node_to_ptr(new_n0); new_n0->back_pointer = node->back_pointer; new_n0->parent_slot = node->parent_slot; new_n0->nr_leaves_on_branch = node->nr_leaves_on_branch; edit->adjust_count_on = new_n0; collapse.node = new_n0; collapse.skip_leaf = assoc_array_ptr_to_leaf(edit->dead_leaf); collapse.slot = 0; assoc_array_subtree_iterate(assoc_array_node_to_ptr(node), node->back_pointer, assoc_array_delete_collapse_iterator, &collapse); pr_devel("collapsed %d,%lu\n", collapse.slot, new_n0->nr_leaves_on_branch); BUG_ON(collapse.slot != new_n0->nr_leaves_on_branch - 1); if (!node->back_pointer) { edit->set[1].ptr = &array->root; } else if (assoc_array_ptr_is_leaf(node->back_pointer)) { BUG(); } else if (assoc_array_ptr_is_node(node->back_pointer)) { struct assoc_array_node *p = assoc_array_ptr_to_node(node->back_pointer); edit->set[1].ptr = &p->slots[node->parent_slot]; } else if (assoc_array_ptr_is_shortcut(node->back_pointer)) { struct assoc_array_shortcut *s = assoc_array_ptr_to_shortcut(node->back_pointer); edit->set[1].ptr = &s->next_node; } edit->set[1].to = assoc_array_node_to_ptr(new_n0); edit->excised_subtree = assoc_array_node_to_ptr(node); } } return edit; enomem: /* Clean up after an out of memory error */ pr_devel("enomem\n"); assoc_array_cancel_edit(edit); return ERR_PTR(-ENOMEM); } /** * assoc_array_clear - Script deletion of all objects from an associative array * @array: The array to clear. * @ops: The operations to use. * * Precalculate and preallocate a script for the deletion of all the objects * from an associative array. This results in an edit script that can either * be applied or cancelled. * * The function returns a pointer to an edit script if there are objects to be * deleted, NULL if there are no objects in the array or -ENOMEM. * * The caller should lock against other modifications and must continue to hold * the lock until assoc_array_apply_edit() has been called. * * Accesses to the tree may take place concurrently with this function, * provided they hold the RCU read lock. */ struct assoc_array_edit *assoc_array_clear(struct assoc_array *array, const struct assoc_array_ops *ops) { struct assoc_array_edit *edit; pr_devel("-->%s()\n", __func__); if (!array->root) return NULL; edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL); if (!edit) return ERR_PTR(-ENOMEM); edit->array = array; edit->ops = ops; edit->set[1].ptr = &array->root; edit->set[1].to = NULL; edit->excised_subtree = array->root; edit->ops_for_excised_subtree = ops; pr_devel("all gone\n"); return edit; } /* * Handle the deferred destruction after an applied edit. */ static void assoc_array_rcu_cleanup(struct rcu_head *head) { struct assoc_array_edit *edit = container_of(head, struct assoc_array_edit, rcu); int i; pr_devel("-->%s()\n", __func__); if (edit->dead_leaf) edit->ops->free_object(assoc_array_ptr_to_leaf(edit->dead_leaf)); for (i = 0; i < ARRAY_SIZE(edit->excised_meta); i++) if (edit->excised_meta[i]) kfree(assoc_array_ptr_to_node(edit->excised_meta[i])); if (edit->excised_subtree) { BUG_ON(assoc_array_ptr_is_leaf(edit->excised_subtree)); if (assoc_array_ptr_is_node(edit->excised_subtree)) { struct assoc_array_node *n = assoc_array_ptr_to_node(edit->excised_subtree); n->back_pointer = NULL; } else { struct assoc_array_shortcut *s = assoc_array_ptr_to_shortcut(edit->excised_subtree); s->back_pointer = NULL; } assoc_array_destroy_subtree(edit->excised_subtree, edit->ops_for_excised_subtree); } kfree(edit); } /** * assoc_array_apply_edit - Apply an edit script to an associative array * @edit: The script to apply. * * Apply an edit script to an associative array to effect an insertion, * deletion or clearance. As the edit script includes preallocated memory, * this is guaranteed not to fail. * * The edit script, dead objects and dead metadata will be scheduled for * destruction after an RCU grace period to permit those doing read-only * accesses on the array to continue to do so under the RCU read lock whilst * the edit is taking place. */ void assoc_array_apply_edit(struct assoc_array_edit *edit) { struct assoc_array_shortcut *shortcut; struct assoc_array_node *node; struct assoc_array_ptr *ptr; int i; pr_devel("-->%s()\n", __func__); smp_wmb(); if (edit->leaf_p) *edit->leaf_p = edit->leaf; smp_wmb(); for (i = 0; i < ARRAY_SIZE(edit->set_parent_slot); i++) if (edit->set_parent_slot[i].p) *edit->set_parent_slot[i].p = edit->set_parent_slot[i].to; smp_wmb(); for (i = 0; i < ARRAY_SIZE(edit->set_backpointers); i++) if (edit->set_backpointers[i]) *edit->set_backpointers[i] = edit->set_backpointers_to; smp_wmb(); for (i = 0; i < ARRAY_SIZE(edit->set); i++) if (edit->set[i].ptr) *edit->set[i].ptr = edit->set[i].to; if (edit->array->root == NULL) { edit->array->nr_leaves_on_tree = 0; } else if (edit->adjust_count_on) { node = edit->adjust_count_on; for (;;) { node->nr_leaves_on_branch += edit->adjust_count_by; ptr = node->back_pointer; if (!ptr) break; if (assoc_array_ptr_is_shortcut(ptr)) { shortcut = assoc_array_ptr_to_shortcut(ptr); ptr = shortcut->back_pointer; if (!ptr) break; } BUG_ON(!assoc_array_ptr_is_node(ptr)); node = assoc_array_ptr_to_node(ptr); } edit->array->nr_leaves_on_tree += edit->adjust_count_by; } call_rcu(&edit->rcu, assoc_array_rcu_cleanup); } /** * assoc_array_cancel_edit - Discard an edit script. * @edit: The script to discard. * * Free an edit script and all the preallocated data it holds without making * any changes to the associative array it was intended for. * * NOTE! In the case of an insertion script, this does _not_ release the leaf * that was to be inserted. That is left to the caller. */ void assoc_array_cancel_edit(struct assoc_array_edit *edit) { struct assoc_array_ptr *ptr; int i; pr_devel("-->%s()\n", __func__); /* Clean up after an out of memory error */ for (i = 0; i < ARRAY_SIZE(edit->new_meta); i++) { ptr = edit->new_meta[i]; if (ptr) { if (assoc_array_ptr_is_node(ptr)) kfree(assoc_array_ptr_to_node(ptr)); else kfree(assoc_array_ptr_to_shortcut(ptr)); } } kfree(edit); } /** * assoc_array_gc - Garbage collect an associative array. * @array: The array to clean. * @ops: The operations to use. * @iterator: A callback function to pass judgement on each object. * @iterator_data: Private data for the callback function. * * Collect garbage from an associative array and pack down the internal tree to * save memory. * * The iterator function is asked to pass judgement upon each object in the * array. If it returns false, the object is discard and if it returns true, * the object is kept. If it returns true, it must increment the object's * usage count (or whatever it needs to do to retain it) before returning. * * This function returns 0 if successful or -ENOMEM if out of memory. In the * latter case, the array is not changed. * * The caller should lock against other modifications and must continue to hold * the lock until assoc_array_apply_edit() has been called. * * Accesses to the tree may take place concurrently with this function, * provided they hold the RCU read lock. */ int assoc_array_gc(struct assoc_array *array, const struct assoc_array_ops *ops, bool (*iterator)(void *object, void *iterator_data), void *iterator_data) { struct assoc_array_shortcut *shortcut, *new_s; struct assoc_array_node *node, *new_n; struct assoc_array_edit *edit; struct assoc_array_ptr *cursor, *ptr; struct assoc_array_ptr *new_root, *new_parent, **new_ptr_pp; unsigned long nr_leaves_on_tree; int keylen, slot, nr_free, next_slot, i; pr_devel("-->%s()\n", __func__); if (!array->root) return 0; edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL); if (!edit) return -ENOMEM; edit->array = array; edit->ops = ops; edit->ops_for_excised_subtree = ops; edit->set[0].ptr = &array->root; edit->excised_subtree = array->root; new_root = new_parent = NULL; new_ptr_pp = &new_root; cursor = array->root; descend: /* If this point is a shortcut, then we need to duplicate it and * advance the target cursor. */ if (assoc_array_ptr_is_shortcut(cursor)) { shortcut = assoc_array_ptr_to_shortcut(cursor); keylen = round_up(shortcut->skip_to_level, ASSOC_ARRAY_KEY_CHUNK_SIZE); keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT; new_s = kmalloc(sizeof(struct assoc_array_shortcut) + keylen * sizeof(unsigned long), GFP_KERNEL); if (!new_s) goto enomem; pr_devel("dup shortcut %p -> %p\n", shortcut, new_s); memcpy(new_s, shortcut, (sizeof(struct assoc_array_shortcut) + keylen * sizeof(unsigned long))); new_s->back_pointer = new_parent; new_s->parent_slot = shortcut->parent_slot; *new_ptr_pp = new_parent = assoc_array_shortcut_to_ptr(new_s); new_ptr_pp = &new_s->next_node; cursor = shortcut->next_node; } /* Duplicate the node at this position */ node = assoc_array_ptr_to_node(cursor); new_n = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL); if (!new_n) goto enomem; pr_devel("dup node %p -> %p\n", node, new_n); new_n->back_pointer = new_parent; new_n->parent_slot = node->parent_slot; *new_ptr_pp = new_parent = assoc_array_node_to_ptr(new_n); new_ptr_pp = NULL; slot = 0; continue_node: /* Filter across any leaves and gc any subtrees */ for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) { ptr = node->slots[slot]; if (!ptr) continue; if (assoc_array_ptr_is_leaf(ptr)) { if (iterator(assoc_array_ptr_to_leaf(ptr), iterator_data)) /* The iterator will have done any reference * counting on the object for us. */ new_n->slots[slot] = ptr; continue; } new_ptr_pp = &new_n->slots[slot]; cursor = ptr; goto descend; } pr_devel("-- compress node %p --\n", new_n); /* Count up the number of empty slots in this node and work out the * subtree leaf count. */ new_n->nr_leaves_on_branch = 0; nr_free = 0; for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) { ptr = new_n->slots[slot]; if (!ptr) nr_free++; else if (assoc_array_ptr_is_leaf(ptr)) new_n->nr_leaves_on_branch++; } pr_devel("free=%d, leaves=%lu\n", nr_free, new_n->nr_leaves_on_branch); /* See what we can fold in */ next_slot = 0; for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) { struct assoc_array_shortcut *s; struct assoc_array_node *child; ptr = new_n->slots[slot]; if (!ptr || assoc_array_ptr_is_leaf(ptr)) continue; s = NULL; if (assoc_array_ptr_is_shortcut(ptr)) { s = assoc_array_ptr_to_shortcut(ptr); ptr = s->next_node; } child = assoc_array_ptr_to_node(ptr); new_n->nr_leaves_on_branch += child->nr_leaves_on_branch; if (child->nr_leaves_on_branch <= nr_free + 1) { /* Fold the child node into this one */ pr_devel("[%d] fold node %lu/%d [nx %d]\n", slot, child->nr_leaves_on_branch, nr_free + 1, next_slot); /* We would already have reaped an intervening shortcut * on the way back up the tree. */ BUG_ON(s); new_n->slots[slot] = NULL; nr_free++; if (slot < next_slot) next_slot = slot; for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { struct assoc_array_ptr *p = child->slots[i]; if (!p) continue; BUG_ON(assoc_array_ptr_is_meta(p)); while (new_n->slots[next_slot]) next_slot++; BUG_ON(next_slot >= ASSOC_ARRAY_FAN_OUT); new_n->slots[next_slot++] = p; nr_free--; } kfree(child); } else { pr_devel("[%d] retain node %lu/%d [nx %d]\n", slot, child->nr_leaves_on_branch, nr_free + 1, next_slot); } } pr_devel("after: %lu\n", new_n->nr_leaves_on_branch); nr_leaves_on_tree = new_n->nr_leaves_on_branch; /* Excise this node if it is singly occupied by a shortcut */ if (nr_free == ASSOC_ARRAY_FAN_OUT - 1) { for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) if ((ptr = new_n->slots[slot])) break; if (assoc_array_ptr_is_meta(ptr) && assoc_array_ptr_is_shortcut(ptr)) { pr_devel("excise node %p with 1 shortcut\n", new_n); new_s = assoc_array_ptr_to_shortcut(ptr); new_parent = new_n->back_pointer; slot = new_n->parent_slot; kfree(new_n); if (!new_parent) { new_s->back_pointer = NULL; new_s->parent_slot = 0; new_root = ptr; goto gc_complete; } if (assoc_array_ptr_is_shortcut(new_parent)) { /* We can discard any preceding shortcut also */ struct assoc_array_shortcut *s = assoc_array_ptr_to_shortcut(new_parent); pr_devel("excise preceding shortcut\n"); new_parent = new_s->back_pointer = s->back_pointer; slot = new_s->parent_slot = s->parent_slot; kfree(s); if (!new_parent) { new_s->back_pointer = NULL; new_s->parent_slot = 0; new_root = ptr; goto gc_complete; } } new_s->back_pointer = new_parent; new_s->parent_slot = slot; new_n = assoc_array_ptr_to_node(new_parent); new_n->slots[slot] = ptr; goto ascend_old_tree; } } /* Excise any shortcuts we might encounter that point to nodes that * only contain leaves. */ ptr = new_n->back_pointer; if (!ptr) goto gc_complete; if (assoc_array_ptr_is_shortcut(ptr)) { new_s = assoc_array_ptr_to_shortcut(ptr); new_parent = new_s->back_pointer; slot = new_s->parent_slot; if (new_n->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT) { struct assoc_array_node *n; pr_devel("excise shortcut\n"); new_n->back_pointer = new_parent; new_n->parent_slot = slot; kfree(new_s); if (!new_parent) { new_root = assoc_array_node_to_ptr(new_n); goto gc_complete; } n = assoc_array_ptr_to_node(new_parent); n->slots[slot] = assoc_array_node_to_ptr(new_n); } } else { new_parent = ptr; } new_n = assoc_array_ptr_to_node(new_parent); ascend_old_tree: ptr = node->back_pointer; if (assoc_array_ptr_is_shortcut(ptr)) { shortcut = assoc_array_ptr_to_shortcut(ptr); slot = shortcut->parent_slot; cursor = shortcut->back_pointer; if (!cursor) goto gc_complete; } else { slot = node->parent_slot; cursor = ptr; } BUG_ON(!cursor); node = assoc_array_ptr_to_node(cursor); slot++; goto continue_node; gc_complete: edit->set[0].to = new_root; assoc_array_apply_edit(edit); array->nr_leaves_on_tree = nr_leaves_on_tree; return 0; enomem: pr_devel("enomem\n"); assoc_array_destroy_subtree(new_root, edit->ops); kfree(edit); return -ENOMEM; }