277 lines
7.2 KiB
C
277 lines
7.2 KiB
C
/*
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* Copyright (C) 2011 STRATO AG
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* written by Arne Jansen <sensille@gmx.net>
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* Distributed under the GNU GPL license version 2.
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*/
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#include <linux/slab.h>
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#include <linux/export.h>
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#include "ulist.h"
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/*
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* ulist is a generic data structure to hold a collection of unique u64
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* values. The only operations it supports is adding to the list and
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* enumerating it.
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* It is possible to store an auxiliary value along with the key.
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*
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* The implementation is preliminary and can probably be sped up
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* significantly. A first step would be to store the values in an rbtree
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* as soon as ULIST_SIZE is exceeded.
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*
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* A sample usage for ulists is the enumeration of directed graphs without
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* visiting a node twice. The pseudo-code could look like this:
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*
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* ulist = ulist_alloc();
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* ulist_add(ulist, root);
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* ULIST_ITER_INIT(&uiter);
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*
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* while ((elem = ulist_next(ulist, &uiter)) {
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* for (all child nodes n in elem)
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* ulist_add(ulist, n);
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* do something useful with the node;
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* }
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* ulist_free(ulist);
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*
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* This assumes the graph nodes are adressable by u64. This stems from the
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* usage for tree enumeration in btrfs, where the logical addresses are
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* 64 bit.
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*
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* It is also useful for tree enumeration which could be done elegantly
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* recursively, but is not possible due to kernel stack limitations. The
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* loop would be similar to the above.
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*/
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/**
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* ulist_init - freshly initialize a ulist
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* @ulist: the ulist to initialize
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*
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* Note: don't use this function to init an already used ulist, use
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* ulist_reinit instead.
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*/
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void ulist_init(struct ulist *ulist)
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{
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ulist->nnodes = 0;
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ulist->nodes = ulist->int_nodes;
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ulist->nodes_alloced = ULIST_SIZE;
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ulist->root = RB_ROOT;
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}
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EXPORT_SYMBOL(ulist_init);
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/**
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* ulist_fini - free up additionally allocated memory for the ulist
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* @ulist: the ulist from which to free the additional memory
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*
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* This is useful in cases where the base 'struct ulist' has been statically
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* allocated.
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*/
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void ulist_fini(struct ulist *ulist)
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{
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/*
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* The first ULIST_SIZE elements are stored inline in struct ulist.
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* Only if more elements are alocated they need to be freed.
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*/
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if (ulist->nodes_alloced > ULIST_SIZE)
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kfree(ulist->nodes);
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ulist->nodes_alloced = 0; /* in case ulist_fini is called twice */
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ulist->root = RB_ROOT;
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}
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EXPORT_SYMBOL(ulist_fini);
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/**
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* ulist_reinit - prepare a ulist for reuse
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* @ulist: ulist to be reused
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*
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* Free up all additional memory allocated for the list elements and reinit
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* the ulist.
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*/
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void ulist_reinit(struct ulist *ulist)
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{
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ulist_fini(ulist);
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ulist_init(ulist);
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}
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EXPORT_SYMBOL(ulist_reinit);
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/**
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* ulist_alloc - dynamically allocate a ulist
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* @gfp_mask: allocation flags to for base allocation
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*
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* The allocated ulist will be returned in an initialized state.
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*/
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struct ulist *ulist_alloc(gfp_t gfp_mask)
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{
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struct ulist *ulist = kmalloc(sizeof(*ulist), gfp_mask);
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if (!ulist)
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return NULL;
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ulist_init(ulist);
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return ulist;
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}
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EXPORT_SYMBOL(ulist_alloc);
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/**
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* ulist_free - free dynamically allocated ulist
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* @ulist: ulist to free
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*
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* It is not necessary to call ulist_fini before.
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*/
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void ulist_free(struct ulist *ulist)
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{
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if (!ulist)
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return;
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ulist_fini(ulist);
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kfree(ulist);
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}
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EXPORT_SYMBOL(ulist_free);
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static struct ulist_node *ulist_rbtree_search(struct ulist *ulist, u64 val)
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{
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struct rb_node *n = ulist->root.rb_node;
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struct ulist_node *u = NULL;
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while (n) {
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u = rb_entry(n, struct ulist_node, rb_node);
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if (u->val < val)
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n = n->rb_right;
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else if (u->val > val)
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n = n->rb_left;
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else
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return u;
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}
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return NULL;
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}
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static int ulist_rbtree_insert(struct ulist *ulist, struct ulist_node *ins)
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{
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struct rb_node **p = &ulist->root.rb_node;
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struct rb_node *parent = NULL;
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struct ulist_node *cur = NULL;
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while (*p) {
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parent = *p;
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cur = rb_entry(parent, struct ulist_node, rb_node);
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if (cur->val < ins->val)
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p = &(*p)->rb_right;
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else if (cur->val > ins->val)
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p = &(*p)->rb_left;
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else
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return -EEXIST;
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}
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rb_link_node(&ins->rb_node, parent, p);
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rb_insert_color(&ins->rb_node, &ulist->root);
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return 0;
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}
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/**
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* ulist_add - add an element to the ulist
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* @ulist: ulist to add the element to
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* @val: value to add to ulist
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* @aux: auxiliary value to store along with val
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* @gfp_mask: flags to use for allocation
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*
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* Note: locking must be provided by the caller. In case of rwlocks write
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* locking is needed
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*
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* Add an element to a ulist. The @val will only be added if it doesn't
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* already exist. If it is added, the auxiliary value @aux is stored along with
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* it. In case @val already exists in the ulist, @aux is ignored, even if
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* it differs from the already stored value.
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*
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* ulist_add returns 0 if @val already exists in ulist and 1 if @val has been
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* inserted.
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* In case of allocation failure -ENOMEM is returned and the ulist stays
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* unaltered.
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*/
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int ulist_add(struct ulist *ulist, u64 val, u64 aux, gfp_t gfp_mask)
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{
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return ulist_add_merge(ulist, val, aux, NULL, gfp_mask);
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}
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int ulist_add_merge(struct ulist *ulist, u64 val, u64 aux,
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u64 *old_aux, gfp_t gfp_mask)
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{
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int ret = 0;
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struct ulist_node *node = NULL;
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node = ulist_rbtree_search(ulist, val);
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if (node) {
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if (old_aux)
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*old_aux = node->aux;
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return 0;
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}
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if (ulist->nnodes >= ulist->nodes_alloced) {
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u64 new_alloced = ulist->nodes_alloced + 128;
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struct ulist_node *new_nodes;
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void *old = NULL;
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int i;
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/*
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* if nodes_alloced == ULIST_SIZE no memory has been allocated
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* yet, so pass NULL to krealloc
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*/
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if (ulist->nodes_alloced > ULIST_SIZE)
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old = ulist->nodes;
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new_nodes = krealloc(old, sizeof(*new_nodes) * new_alloced,
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gfp_mask);
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if (!new_nodes)
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return -ENOMEM;
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if (!old)
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memcpy(new_nodes, ulist->int_nodes,
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sizeof(ulist->int_nodes));
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ulist->nodes = new_nodes;
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ulist->nodes_alloced = new_alloced;
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/*
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* krealloc actually uses memcpy, which does not copy rb_node
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* pointers, so we have to do it ourselves. Otherwise we may
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* be bitten by crashes.
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*/
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ulist->root = RB_ROOT;
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for (i = 0; i < ulist->nnodes; i++) {
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ret = ulist_rbtree_insert(ulist, &ulist->nodes[i]);
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if (ret < 0)
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return ret;
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}
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}
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ulist->nodes[ulist->nnodes].val = val;
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ulist->nodes[ulist->nnodes].aux = aux;
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ret = ulist_rbtree_insert(ulist, &ulist->nodes[ulist->nnodes]);
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BUG_ON(ret);
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++ulist->nnodes;
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return 1;
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}
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EXPORT_SYMBOL(ulist_add);
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/**
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* ulist_next - iterate ulist
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* @ulist: ulist to iterate
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* @uiter: iterator variable, initialized with ULIST_ITER_INIT(&iterator)
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*
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* Note: locking must be provided by the caller. In case of rwlocks only read
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* locking is needed
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*
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* This function is used to iterate an ulist.
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* It returns the next element from the ulist or %NULL when the
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* end is reached. No guarantee is made with respect to the order in which
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* the elements are returned. They might neither be returned in order of
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* addition nor in ascending order.
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* It is allowed to call ulist_add during an enumeration. Newly added items
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* are guaranteed to show up in the running enumeration.
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*/
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struct ulist_node *ulist_next(struct ulist *ulist, struct ulist_iterator *uiter)
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{
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if (ulist->nnodes == 0)
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return NULL;
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if (uiter->i < 0 || uiter->i >= ulist->nnodes)
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return NULL;
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return &ulist->nodes[uiter->i++];
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}
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EXPORT_SYMBOL(ulist_next);
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