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