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git.proxmox.com Git - mirror_ubuntu-bionic-kernel.git/blob - fs/btrfs/ulist.c
2 * Copyright (C) 2011 STRATO AG
3 * written by Arne Jansen <sensille@gmx.net>
4 * Distributed under the GNU GPL license version 2.
7 #include <linux/slab.h>
8 #include <linux/export.h>
13 * ulist is a generic data structure to hold a collection of unique u64
14 * values. The only operations it supports is adding to the list and
16 * It is possible to store an auxiliary value along with the key.
18 * A sample usage for ulists is the enumeration of directed graphs without
19 * visiting a node twice. The pseudo-code could look like this:
21 * ulist = ulist_alloc();
22 * ulist_add(ulist, root);
23 * ULIST_ITER_INIT(&uiter);
25 * while ((elem = ulist_next(ulist, &uiter)) {
26 * for (all child nodes n in elem)
27 * ulist_add(ulist, n);
28 * do something useful with the node;
32 * This assumes the graph nodes are adressable by u64. This stems from the
33 * usage for tree enumeration in btrfs, where the logical addresses are
36 * It is also useful for tree enumeration which could be done elegantly
37 * recursively, but is not possible due to kernel stack limitations. The
38 * loop would be similar to the above.
42 * ulist_init - freshly initialize a ulist
43 * @ulist: the ulist to initialize
45 * Note: don't use this function to init an already used ulist, use
46 * ulist_reinit instead.
48 void ulist_init(struct ulist
*ulist
)
50 INIT_LIST_HEAD(&ulist
->nodes
);
51 ulist
->root
= RB_ROOT
;
54 EXPORT_SYMBOL(ulist_init
);
57 * ulist_fini - free up additionally allocated memory for the ulist
58 * @ulist: the ulist from which to free the additional memory
60 * This is useful in cases where the base 'struct ulist' has been statically
63 void ulist_fini(struct ulist
*ulist
)
65 struct ulist_node
*node
;
66 struct ulist_node
*next
;
68 list_for_each_entry_safe(node
, next
, &ulist
->nodes
, list
) {
71 ulist
->root
= RB_ROOT
;
72 INIT_LIST_HEAD(&ulist
->nodes
);
74 EXPORT_SYMBOL(ulist_fini
);
77 * ulist_reinit - prepare a ulist for reuse
78 * @ulist: ulist to be reused
80 * Free up all additional memory allocated for the list elements and reinit
83 void ulist_reinit(struct ulist
*ulist
)
88 EXPORT_SYMBOL(ulist_reinit
);
91 * ulist_alloc - dynamically allocate a ulist
92 * @gfp_mask: allocation flags to for base allocation
94 * The allocated ulist will be returned in an initialized state.
96 struct ulist
*ulist_alloc(gfp_t gfp_mask
)
98 struct ulist
*ulist
= kmalloc(sizeof(*ulist
), gfp_mask
);
107 EXPORT_SYMBOL(ulist_alloc
);
110 * ulist_free - free dynamically allocated ulist
111 * @ulist: ulist to free
113 * It is not necessary to call ulist_fini before.
115 void ulist_free(struct ulist
*ulist
)
122 EXPORT_SYMBOL(ulist_free
);
124 static struct ulist_node
*ulist_rbtree_search(struct ulist
*ulist
, u64 val
)
126 struct rb_node
*n
= ulist
->root
.rb_node
;
127 struct ulist_node
*u
= NULL
;
130 u
= rb_entry(n
, struct ulist_node
, rb_node
);
133 else if (u
->val
> val
)
141 static int ulist_rbtree_insert(struct ulist
*ulist
, struct ulist_node
*ins
)
143 struct rb_node
**p
= &ulist
->root
.rb_node
;
144 struct rb_node
*parent
= NULL
;
145 struct ulist_node
*cur
= NULL
;
149 cur
= rb_entry(parent
, struct ulist_node
, rb_node
);
151 if (cur
->val
< ins
->val
)
153 else if (cur
->val
> ins
->val
)
158 rb_link_node(&ins
->rb_node
, parent
, p
);
159 rb_insert_color(&ins
->rb_node
, &ulist
->root
);
164 * ulist_add - add an element to the ulist
165 * @ulist: ulist to add the element to
166 * @val: value to add to ulist
167 * @aux: auxiliary value to store along with val
168 * @gfp_mask: flags to use for allocation
170 * Note: locking must be provided by the caller. In case of rwlocks write
173 * Add an element to a ulist. The @val will only be added if it doesn't
174 * already exist. If it is added, the auxiliary value @aux is stored along with
175 * it. In case @val already exists in the ulist, @aux is ignored, even if
176 * it differs from the already stored value.
178 * ulist_add returns 0 if @val already exists in ulist and 1 if @val has been
180 * In case of allocation failure -ENOMEM is returned and the ulist stays
183 int ulist_add(struct ulist
*ulist
, u64 val
, u64 aux
, gfp_t gfp_mask
)
185 return ulist_add_merge(ulist
, val
, aux
, NULL
, gfp_mask
);
188 int ulist_add_merge(struct ulist
*ulist
, u64 val
, u64 aux
,
189 u64
*old_aux
, gfp_t gfp_mask
)
192 struct ulist_node
*node
;
194 node
= ulist_rbtree_search(ulist
, val
);
197 *old_aux
= node
->aux
;
200 node
= kmalloc(sizeof(*node
), gfp_mask
);
206 #ifdef CONFIG_BTRFS_DEBUG
207 node
->seqnum
= ulist
->nnodes
;
210 ret
= ulist_rbtree_insert(ulist
, node
);
212 list_add_tail(&node
->list
, &ulist
->nodes
);
217 EXPORT_SYMBOL(ulist_add
);
220 * ulist_next - iterate ulist
221 * @ulist: ulist to iterate
222 * @uiter: iterator variable, initialized with ULIST_ITER_INIT(&iterator)
224 * Note: locking must be provided by the caller. In case of rwlocks only read
227 * This function is used to iterate an ulist.
228 * It returns the next element from the ulist or %NULL when the
229 * end is reached. No guarantee is made with respect to the order in which
230 * the elements are returned. They might neither be returned in order of
231 * addition nor in ascending order.
232 * It is allowed to call ulist_add during an enumeration. Newly added items
233 * are guaranteed to show up in the running enumeration.
235 struct ulist_node
*ulist_next(struct ulist
*ulist
, struct ulist_iterator
*uiter
)
237 struct ulist_node
*node
;
239 if (list_empty(&ulist
->nodes
))
241 if (uiter
->cur_list
&& uiter
->cur_list
->next
== &ulist
->nodes
)
243 if (uiter
->cur_list
) {
244 uiter
->cur_list
= uiter
->cur_list
->next
;
246 uiter
->cur_list
= ulist
->nodes
.next
;
247 #ifdef CONFIG_BTRFS_DEBUG
251 node
= list_entry(uiter
->cur_list
, struct ulist_node
, list
);
252 #ifdef CONFIG_BTRFS_DEBUG
253 ASSERT(node
->seqnum
== uiter
->i
);
254 ASSERT(uiter
->i
>= 0 && uiter
->i
< ulist
->nnodes
);
259 EXPORT_SYMBOL(ulist_next
);