1
2#include <linux/export.h>
3#include <linux/generic-radix-tree.h>
4#include <linux/gfp.h>
5#include <linux/kmemleak.h>
6
7#define GENRADIX_ARY		(PAGE_SIZE / sizeof(struct genradix_node *))
8#define GENRADIX_ARY_SHIFT	ilog2(GENRADIX_ARY)
9
10struct genradix_node {
11	union {
12		/* Interior node: */
13		struct genradix_node	*children[GENRADIX_ARY];
14
15		/* Leaf: */
16		u8			data[PAGE_SIZE];
17	};
18};
19
20static inline int genradix_depth_shift(unsigned depth)
21{
22	return PAGE_SHIFT + GENRADIX_ARY_SHIFT * depth;
23}
24
25/*
26 * Returns size (of data, in bytes) that a tree of a given depth holds:
27 */
28static inline size_t genradix_depth_size(unsigned depth)
29{
30	return 1UL << genradix_depth_shift(depth);
31}
32
33/* depth that's needed for a genradix that can address up to ULONG_MAX: */
34#define GENRADIX_MAX_DEPTH	\
35	DIV_ROUND_UP(BITS_PER_LONG - PAGE_SHIFT, GENRADIX_ARY_SHIFT)
36
37#define GENRADIX_DEPTH_MASK				\
38	((unsigned long) (roundup_pow_of_two(GENRADIX_MAX_DEPTH + 1) - 1))
39
40static inline unsigned genradix_root_to_depth(struct genradix_root *r)
41{
42	return (unsigned long) r & GENRADIX_DEPTH_MASK;
43}
44
45static inline struct genradix_node *genradix_root_to_node(struct genradix_root *r)
46{
47	return (void *) ((unsigned long) r & ~GENRADIX_DEPTH_MASK);
48}
49
50/*
51 * Returns pointer to the specified byte @offset within @radix, or NULL if not
52 * allocated
53 */
54void *__genradix_ptr(struct __genradix *radix, size_t offset)
55{
56	struct genradix_root *r = READ_ONCE(radix->root);
57	struct genradix_node *n = genradix_root_to_node(r);
58	unsigned level		= genradix_root_to_depth(r);
59
60	if (ilog2(offset) >= genradix_depth_shift(level))
61		return NULL;
62
63	while (1) {
64		if (!n)
65			return NULL;
66		if (!level)
67			break;
68
69		level--;
70
71		n = n->children[offset >> genradix_depth_shift(level)];
72		offset &= genradix_depth_size(level) - 1;
73	}
74
75	return &n->data[offset];
76}
77EXPORT_SYMBOL(__genradix_ptr);
78
79static inline struct genradix_node *genradix_alloc_node(gfp_t gfp_mask)
80{
81	struct genradix_node *node;
82
83	node = (struct genradix_node *)__get_free_page(gfp_mask|__GFP_ZERO);
84
85	/*
86	 * We're using pages (not slab allocations) directly for kernel data
87	 * structures, so we need to explicitly inform kmemleak of them in order
88	 * to avoid false positive memory leak reports.
89	 */
90	kmemleak_alloc(node, PAGE_SIZE, 1, gfp_mask);
91	return node;
92}
93
94static inline void genradix_free_node(struct genradix_node *node)
95{
96	kmemleak_free(node);
97	free_page((unsigned long)node);
98}
99
100/*
101 * Returns pointer to the specified byte @offset within @radix, allocating it if
102 * necessary - newly allocated slots are always zeroed out:
103 */
104void *__genradix_ptr_alloc(struct __genradix *radix, size_t offset,
105			   gfp_t gfp_mask)
106{
107	struct genradix_root *v = READ_ONCE(radix->root);
108	struct genradix_node *n, *new_node = NULL;
109	unsigned level;
110
111	/* Increase tree depth if necessary: */
112	while (1) {
113		struct genradix_root *r = v, *new_root;
114
115		n	= genradix_root_to_node(r);
116		level	= genradix_root_to_depth(r);
117
118		if (n && ilog2(offset) < genradix_depth_shift(level))
119			break;
120
121		if (!new_node) {
122			new_node = genradix_alloc_node(gfp_mask);
123			if (!new_node)
124				return NULL;
125		}
126
127		new_node->children[0] = n;
128		new_root = ((struct genradix_root *)
129			    ((unsigned long) new_node | (n ? level + 1 : 0)));
130
131		if ((v = cmpxchg_release(&radix->root, r, new_root)) == r) {
132			v = new_root;
133			new_node = NULL;
134		}
135	}
136
137	while (level--) {
138		struct genradix_node **p =
139			&n->children[offset >> genradix_depth_shift(level)];
140		offset &= genradix_depth_size(level) - 1;
141
142		n = READ_ONCE(*p);
143		if (!n) {
144			if (!new_node) {
145				new_node = genradix_alloc_node(gfp_mask);
146				if (!new_node)
147					return NULL;
148			}
149
150			if (!(n = cmpxchg_release(p, NULL, new_node)))
151				swap(n, new_node);
152		}
153	}
154
155	if (new_node)
156		genradix_free_node(new_node);
157
158	return &n->data[offset];
159}
160EXPORT_SYMBOL(__genradix_ptr_alloc);
161
162void *__genradix_iter_peek(struct genradix_iter *iter,
163			   struct __genradix *radix,
164			   size_t objs_per_page)
165{
166	struct genradix_root *r;
167	struct genradix_node *n;
168	unsigned level, i;
169
170	if (iter->offset == SIZE_MAX)
171		return NULL;
172
173restart:
174	r = READ_ONCE(radix->root);
175	if (!r)
176		return NULL;
177
178	n	= genradix_root_to_node(r);
179	level	= genradix_root_to_depth(r);
180
181	if (ilog2(iter->offset) >= genradix_depth_shift(level))
182		return NULL;
183
184	while (level) {
185		level--;
186
187		i = (iter->offset >> genradix_depth_shift(level)) &
188			(GENRADIX_ARY - 1);
189
190		while (!n->children[i]) {
191			size_t objs_per_ptr = genradix_depth_size(level);
192
193			if (iter->offset + objs_per_ptr < iter->offset) {
194				iter->offset	= SIZE_MAX;
195				iter->pos	= SIZE_MAX;
196				return NULL;
197			}
198
199			i++;
200			iter->offset = round_down(iter->offset + objs_per_ptr,
201						  objs_per_ptr);
202			iter->pos = (iter->offset >> PAGE_SHIFT) *
203				objs_per_page;
204			if (i == GENRADIX_ARY)
205				goto restart;
206		}
207
208		n = n->children[i];
209	}
210
211	return &n->data[iter->offset & (PAGE_SIZE - 1)];
212}
213EXPORT_SYMBOL(__genradix_iter_peek);
214
215static void genradix_free_recurse(struct genradix_node *n, unsigned level)
216{
217	if (level) {
218		unsigned i;
219
220		for (i = 0; i < GENRADIX_ARY; i++)
221			if (n->children[i])
222				genradix_free_recurse(n->children[i], level - 1);
223	}
224
225	genradix_free_node(n);
226}
227
228int __genradix_prealloc(struct __genradix *radix, size_t size,
229			gfp_t gfp_mask)
230{
231	size_t offset;
232
233	for (offset = 0; offset < size; offset += PAGE_SIZE)
234		if (!__genradix_ptr_alloc(radix, offset, gfp_mask))
235			return -ENOMEM;
236
237	return 0;
238}
239EXPORT_SYMBOL(__genradix_prealloc);
240
241void __genradix_free(struct __genradix *radix)
242{
243	struct genradix_root *r = xchg(&radix->root, NULL);
244
245	genradix_free_recurse(genradix_root_to_node(r),
246			      genradix_root_to_depth(r));
247}
248EXPORT_SYMBOL(__genradix_free);
249