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git.proxmox.com Git - mirror_ubuntu-artful-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>
12 * ulist is a generic data structure to hold a collection of unique u64
13 * values. The only operations it supports is adding to the list and
15 * It is possible to store an auxiliary value along with the key.
17 * A sample usage for ulists is the enumeration of directed graphs without
18 * visiting a node twice. The pseudo-code could look like this:
20 * ulist = ulist_alloc();
21 * ulist_add(ulist, root);
22 * ULIST_ITER_INIT(&uiter);
24 * while ((elem = ulist_next(ulist, &uiter)) {
25 * for (all child nodes n in elem)
26 * ulist_add(ulist, n);
27 * do something useful with the node;
31 * This assumes the graph nodes are adressable by u64. This stems from the
32 * usage for tree enumeration in btrfs, where the logical addresses are
35 * It is also useful for tree enumeration which could be done elegantly
36 * recursively, but is not possible due to kernel stack limitations. The
37 * loop would be similar to the above.
41 * ulist_init - freshly initialize a ulist
42 * @ulist: the ulist to initialize
44 * Note: don't use this function to init an already used ulist, use
45 * ulist_reinit instead.
47 void ulist_init(struct ulist
*ulist
)
49 INIT_LIST_HEAD(&ulist
->nodes
);
50 ulist
->root
= RB_ROOT
;
55 * ulist_fini - free up additionally allocated memory for the ulist
56 * @ulist: the ulist from which to free the additional memory
58 * This is useful in cases where the base 'struct ulist' has been statically
61 static void ulist_fini(struct ulist
*ulist
)
63 struct ulist_node
*node
;
64 struct ulist_node
*next
;
66 list_for_each_entry_safe(node
, next
, &ulist
->nodes
, list
) {
69 ulist
->root
= RB_ROOT
;
70 INIT_LIST_HEAD(&ulist
->nodes
);
74 * ulist_reinit - prepare a ulist for reuse
75 * @ulist: ulist to be reused
77 * Free up all additional memory allocated for the list elements and reinit
80 void ulist_reinit(struct ulist
*ulist
)
87 * ulist_alloc - dynamically allocate a ulist
88 * @gfp_mask: allocation flags to for base allocation
90 * The allocated ulist will be returned in an initialized state.
92 struct ulist
*ulist_alloc(gfp_t gfp_mask
)
94 struct ulist
*ulist
= kmalloc(sizeof(*ulist
), gfp_mask
);
105 * ulist_free - free dynamically allocated ulist
106 * @ulist: ulist to free
108 * It is not necessary to call ulist_fini before.
110 void ulist_free(struct ulist
*ulist
)
118 static struct ulist_node
*ulist_rbtree_search(struct ulist
*ulist
, u64 val
)
120 struct rb_node
*n
= ulist
->root
.rb_node
;
121 struct ulist_node
*u
= NULL
;
124 u
= rb_entry(n
, struct ulist_node
, rb_node
);
127 else if (u
->val
> val
)
135 static int ulist_rbtree_insert(struct ulist
*ulist
, struct ulist_node
*ins
)
137 struct rb_node
**p
= &ulist
->root
.rb_node
;
138 struct rb_node
*parent
= NULL
;
139 struct ulist_node
*cur
= NULL
;
143 cur
= rb_entry(parent
, struct ulist_node
, rb_node
);
145 if (cur
->val
< ins
->val
)
147 else if (cur
->val
> ins
->val
)
152 rb_link_node(&ins
->rb_node
, parent
, p
);
153 rb_insert_color(&ins
->rb_node
, &ulist
->root
);
158 * ulist_add - add an element to the ulist
159 * @ulist: ulist to add the element to
160 * @val: value to add to ulist
161 * @aux: auxiliary value to store along with val
162 * @gfp_mask: flags to use for allocation
164 * Note: locking must be provided by the caller. In case of rwlocks write
167 * Add an element to a ulist. The @val will only be added if it doesn't
168 * already exist. If it is added, the auxiliary value @aux is stored along with
169 * it. In case @val already exists in the ulist, @aux is ignored, even if
170 * it differs from the already stored value.
172 * ulist_add returns 0 if @val already exists in ulist and 1 if @val has been
174 * In case of allocation failure -ENOMEM is returned and the ulist stays
177 int ulist_add(struct ulist
*ulist
, u64 val
, u64 aux
, gfp_t gfp_mask
)
179 return ulist_add_merge(ulist
, val
, aux
, NULL
, gfp_mask
);
182 int ulist_add_merge(struct ulist
*ulist
, u64 val
, u64 aux
,
183 u64
*old_aux
, gfp_t gfp_mask
)
186 struct ulist_node
*node
;
188 node
= ulist_rbtree_search(ulist
, val
);
191 *old_aux
= node
->aux
;
194 node
= kmalloc(sizeof(*node
), gfp_mask
);
200 #ifdef CONFIG_BTRFS_DEBUG
201 node
->seqnum
= ulist
->nnodes
;
204 ret
= ulist_rbtree_insert(ulist
, node
);
206 list_add_tail(&node
->list
, &ulist
->nodes
);
213 * ulist_next - iterate ulist
214 * @ulist: ulist to iterate
215 * @uiter: iterator variable, initialized with ULIST_ITER_INIT(&iterator)
217 * Note: locking must be provided by the caller. In case of rwlocks only read
220 * This function is used to iterate an ulist.
221 * It returns the next element from the ulist or %NULL when the
222 * end is reached. No guarantee is made with respect to the order in which
223 * the elements are returned. They might neither be returned in order of
224 * addition nor in ascending order.
225 * It is allowed to call ulist_add during an enumeration. Newly added items
226 * are guaranteed to show up in the running enumeration.
228 struct ulist_node
*ulist_next(struct ulist
*ulist
, struct ulist_iterator
*uiter
)
230 struct ulist_node
*node
;
232 if (list_empty(&ulist
->nodes
))
234 if (uiter
->cur_list
&& uiter
->cur_list
->next
== &ulist
->nodes
)
236 if (uiter
->cur_list
) {
237 uiter
->cur_list
= uiter
->cur_list
->next
;
239 uiter
->cur_list
= ulist
->nodes
.next
;
240 #ifdef CONFIG_BTRFS_DEBUG
244 node
= list_entry(uiter
->cur_list
, struct ulist_node
, list
);
245 #ifdef CONFIG_BTRFS_DEBUG
246 ASSERT(node
->seqnum
== uiter
->i
);
247 ASSERT(uiter
->i
>= 0 && uiter
->i
< ulist
->nnodes
);