1
  2#include <linux/atomic.h>
  3#include <linux/export.h>
  4#include <linux/generic-radix-tree.h>
  5#include <linux/gfp.h>
  6#include <linux/kmemleak.h>
  7
  8#define GENRADIX_ARY		(GENRADIX_NODE_SIZE / sizeof(struct genradix_node *))
  9#define GENRADIX_ARY_SHIFT	ilog2(GENRADIX_ARY)
 10
 11struct genradix_node {
 12	union {
 13		/* Interior node: */
 14		struct genradix_node	*children[GENRADIX_ARY];
 15
 16		/* Leaf: */
 17		u8			data[GENRADIX_NODE_SIZE];
 18	};
 19};
 20
 21static inline int genradix_depth_shift(unsigned depth)
 22{
 23	return GENRADIX_NODE_SHIFT + GENRADIX_ARY_SHIFT * depth;
 24}
 25
 26/*
 27 * Returns size (of data, in bytes) that a tree of a given depth holds:
 28 */
 29static inline size_t genradix_depth_size(unsigned depth)
 30{
 31	return 1UL << genradix_depth_shift(depth);
 32}
 33
 34/* depth that's needed for a genradix that can address up to ULONG_MAX: */
 35#define GENRADIX_MAX_DEPTH	\
 36	DIV_ROUND_UP(BITS_PER_LONG - GENRADIX_NODE_SHIFT, GENRADIX_ARY_SHIFT)
 37
 38#define GENRADIX_DEPTH_MASK				\
 39	((unsigned long) (roundup_pow_of_two(GENRADIX_MAX_DEPTH + 1) - 1))
 40
 41static inline unsigned genradix_root_to_depth(struct genradix_root *r)
 42{
 43	return (unsigned long) r & GENRADIX_DEPTH_MASK;
 44}
 45
 46static inline struct genradix_node *genradix_root_to_node(struct genradix_root *r)
 47{
 48	return (void *) ((unsigned long) r & ~GENRADIX_DEPTH_MASK);
 49}
 50
 51/*
 52 * Returns pointer to the specified byte @offset within @radix, or NULL if not
 53 * allocated
 54 */
 55void *__genradix_ptr(struct __genradix *radix, size_t offset)
 56{
 57	struct genradix_root *r = READ_ONCE(radix->root);
 58	struct genradix_node *n = genradix_root_to_node(r);
 59	unsigned level		= genradix_root_to_depth(r);
 60
 61	if (ilog2(offset) >= genradix_depth_shift(level))
 62		return NULL;
 63
 64	while (1) {
 65		if (!n)
 66			return NULL;
 67		if (!level)
 68			break;
 69
 70		level--;
 71
 72		n = n->children[offset >> genradix_depth_shift(level)];
 73		offset &= genradix_depth_size(level) - 1;
 74	}
 75
 76	return &n->data[offset];
 77}
 78EXPORT_SYMBOL(__genradix_ptr);
 79
 80static inline struct genradix_node *genradix_alloc_node(gfp_t gfp_mask)
 81{
 82	return kzalloc(GENRADIX_NODE_SIZE, gfp_mask);
 83}
 84
 85static inline void genradix_free_node(struct genradix_node *node)
 86{
 87	kfree(node);
 88}
 89
 90/*
 91 * Returns pointer to the specified byte @offset within @radix, allocating it if
 92 * necessary - newly allocated slots are always zeroed out:
 93 */
 94void *__genradix_ptr_alloc(struct __genradix *radix, size_t offset,
 95			   gfp_t gfp_mask)
 96{
 97	struct genradix_root *v = READ_ONCE(radix->root);
 98	struct genradix_node *n, *new_node = NULL;
 99	unsigned level;
100
101	/* Increase tree depth if necessary: */
102	while (1) {
103		struct genradix_root *r = v, *new_root;
104
105		n	= genradix_root_to_node(r);
106		level	= genradix_root_to_depth(r);
107
108		if (n && ilog2(offset) < genradix_depth_shift(level))
109			break;
110
111		if (!new_node) {
112			new_node = genradix_alloc_node(gfp_mask);
113			if (!new_node)
114				return NULL;
115		}
116
117		new_node->children[0] = n;
118		new_root = ((struct genradix_root *)
119			    ((unsigned long) new_node | (n ? level + 1 : 0)));
120
121		if ((v = cmpxchg_release(&radix->root, r, new_root)) == r) {
122			v = new_root;
123			new_node = NULL;
124		}
125	}
126
127	while (level--) {
128		struct genradix_node **p =
129			&n->children[offset >> genradix_depth_shift(level)];
130		offset &= genradix_depth_size(level) - 1;
131
132		n = READ_ONCE(*p);
133		if (!n) {
134			if (!new_node) {
135				new_node = genradix_alloc_node(gfp_mask);
136				if (!new_node)
137					return NULL;
138			}
139
140			if (!(n = cmpxchg_release(p, NULL, new_node)))
141				swap(n, new_node);
142		}
143	}
144
145	if (new_node)
146		genradix_free_node(new_node);
147
148	return &n->data[offset];
149}
150EXPORT_SYMBOL(__genradix_ptr_alloc);
151
152void *__genradix_iter_peek(struct genradix_iter *iter,
153			   struct __genradix *radix,
154			   size_t objs_per_page)
155{
156	struct genradix_root *r;
157	struct genradix_node *n;
158	unsigned level, i;
159
160	if (iter->offset == SIZE_MAX)
161		return NULL;
162
163restart:
164	r = READ_ONCE(radix->root);
165	if (!r)
166		return NULL;
167
168	n	= genradix_root_to_node(r);
169	level	= genradix_root_to_depth(r);
170
171	if (ilog2(iter->offset) >= genradix_depth_shift(level))
172		return NULL;
173
174	while (level) {
175		level--;
176
177		i = (iter->offset >> genradix_depth_shift(level)) &
178			(GENRADIX_ARY - 1);
179
180		while (!n->children[i]) {
181			size_t objs_per_ptr = genradix_depth_size(level);
182
183			if (iter->offset + objs_per_ptr < iter->offset) {
184				iter->offset	= SIZE_MAX;
185				iter->pos	= SIZE_MAX;
186				return NULL;
187			}
188
189			i++;
190			iter->offset = round_down(iter->offset + objs_per_ptr,
191						  objs_per_ptr);
192			iter->pos = (iter->offset >> GENRADIX_NODE_SHIFT) *
193				objs_per_page;
194			if (i == GENRADIX_ARY)
195				goto restart;
196		}
197
198		n = n->children[i];
199	}
200
201	return &n->data[iter->offset & (GENRADIX_NODE_SIZE - 1)];
202}
203EXPORT_SYMBOL(__genradix_iter_peek);
204
205void *__genradix_iter_peek_prev(struct genradix_iter *iter,
206				struct __genradix *radix,
207				size_t objs_per_page,
208				size_t obj_size_plus_page_remainder)
209{
210	struct genradix_root *r;
211	struct genradix_node *n;
212	unsigned level, i;
213
214	if (iter->offset == SIZE_MAX)
215		return NULL;
216
217restart:
218	r = READ_ONCE(radix->root);
219	if (!r)
220		return NULL;
221
222	n	= genradix_root_to_node(r);
223	level	= genradix_root_to_depth(r);
224
225	if (ilog2(iter->offset) >= genradix_depth_shift(level)) {
226		iter->offset = genradix_depth_size(level);
227		iter->pos = (iter->offset >> GENRADIX_NODE_SHIFT) * objs_per_page;
228
229		iter->offset -= obj_size_plus_page_remainder;
230		iter->pos--;
231	}
232
233	while (level) {
234		level--;
235
236		i = (iter->offset >> genradix_depth_shift(level)) &
237			(GENRADIX_ARY - 1);
238
239		while (!n->children[i]) {
240			size_t objs_per_ptr = genradix_depth_size(level);
241
242			iter->offset = round_down(iter->offset, objs_per_ptr);
243			iter->pos = (iter->offset >> GENRADIX_NODE_SHIFT) * objs_per_page;
244
245			if (!iter->offset)
246				return NULL;
247
248			iter->offset -= obj_size_plus_page_remainder;
249			iter->pos--;
250
251			if (!i)
252				goto restart;
253			--i;
254		}
255
256		n = n->children[i];
257	}
258
259	return &n->data[iter->offset & (GENRADIX_NODE_SIZE - 1)];
260}
261EXPORT_SYMBOL(__genradix_iter_peek_prev);
262
263static void genradix_free_recurse(struct genradix_node *n, unsigned level)
264{
265	if (level) {
266		unsigned i;
267
268		for (i = 0; i < GENRADIX_ARY; i++)
269			if (n->children[i])
270				genradix_free_recurse(n->children[i], level - 1);
271	}
272
273	genradix_free_node(n);
274}
275
276int __genradix_prealloc(struct __genradix *radix, size_t size,
277			gfp_t gfp_mask)
278{
279	size_t offset;
280
281	for (offset = 0; offset < size; offset += GENRADIX_NODE_SIZE)
282		if (!__genradix_ptr_alloc(radix, offset, gfp_mask))
283			return -ENOMEM;
284
285	return 0;
286}
287EXPORT_SYMBOL(__genradix_prealloc);
288
289void __genradix_free(struct __genradix *radix)
290{
291	struct genradix_root *r = xchg(&radix->root, NULL);
292
293	genradix_free_recurse(genradix_root_to_node(r),
294			      genradix_root_to_depth(r));
295}
296EXPORT_SYMBOL(__genradix_free);