[mirror_ubuntu-artful-kernel.git] / lib / flex_array.c

/*
 * Flexible array managed in PAGE_SIZE parts
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 * Copyright IBM Corporation, 2009
 *
 * Author: Dave Hansen <dave@linux.vnet.ibm.com>
 */

#include <linux/flex_array.h>
#include <linux/slab.h>
#include <linux/stddef.h>

struct flex_array_part {
	char elements[FLEX_ARRAY_PART_SIZE];
};

static inline int __elements_per_part(int element_size)
{
	return FLEX_ARRAY_PART_SIZE / element_size;
}

static inline int bytes_left_in_base(void)
{
	int element_offset = offsetof(struct flex_array, parts);
	int bytes_left = FLEX_ARRAY_BASE_SIZE - element_offset;
	return bytes_left;
}

static inline int nr_base_part_ptrs(void)
{
	return bytes_left_in_base() / sizeof(struct flex_array_part *);
}

/*
 * If a user requests an allocation which is small
 * enough, we may simply use the space in the
 * flex_array->parts[] array to store the user
 * data.
 */
static inline int elements_fit_in_base(struct flex_array *fa)
{
	int data_size = fa->element_size * fa->total_nr_elements;
	if (data_size <= bytes_left_in_base())
		return 1;
	return 0;
}

/**
 * flex_array_alloc - allocate a new flexible array
 * @element_size:	the size of individual elements in the array
 * @total:		total number of elements that this should hold
 *
 * Note: all locking must be provided by the caller.
 *
 * @total is used to size internal structures.  If the user ever
 * accesses any array indexes >=@total, it will produce errors.
 *
 * The maximum number of elements is defined as: the number of
 * elements that can be stored in a page times the number of
 * page pointers that we can fit in the base structure or (using
 * integer math):
 *
 * 	(PAGE_SIZE/element_size) * (PAGE_SIZE-8)/sizeof(void *)
 *
 * Here's a table showing example capacities.  Note that the maximum
 * index that the get/put() functions is just nr_objects-1.   This
 * basically means that you get 4MB of storage on 32-bit and 2MB on
 * 64-bit.
 *
 *
 * Element size | Objects | Objects |
 * PAGE_SIZE=4k |  32-bit |  64-bit |
 * ---------------------------------|
 *      1 bytes | 4186112 | 2093056 |
 *      2 bytes | 2093056 | 1046528 |
 *      3 bytes | 1395030 |  697515 |
 *      4 bytes | 1046528 |  523264 |
 *     32 bytes |  130816 |   65408 |
 *     33 bytes |  126728 |   63364 |
 *   2048 bytes |    2044 |    1022 |
 *   2049 bytes |    1022 |     511 |
 *       void * | 1046528 |  261632 |
 *
 * Since 64-bit pointers are twice the size, we lose half the
 * capacity in the base structure.  Also note that no effort is made
 * to efficiently pack objects across page boundaries.
 */
struct flex_array *flex_array_alloc(int element_size, unsigned int total,
					gfp_t flags)
{
	struct flex_array *ret;
	int max_size = nr_base_part_ptrs() * __elements_per_part(element_size);

	/* max_size will end up 0 if element_size > PAGE_SIZE */
	if (total > max_size)
		return NULL;
	ret = kzalloc(sizeof(struct flex_array), flags);
	if (!ret)
		return NULL;
	ret->element_size = element_size;
	ret->total_nr_elements = total;
	if (elements_fit_in_base(ret) && !(flags & __GFP_ZERO))
		memset(ret->parts[0], FLEX_ARRAY_FREE, bytes_left_in_base());
	return ret;
}

static int fa_element_to_part_nr(struct flex_array *fa,
					unsigned int element_nr)
{
	return element_nr / __elements_per_part(fa->element_size);
}

/**
 * flex_array_free_parts - just free the second-level pages
 *
 * This is to be used in cases where the base 'struct flex_array'
 * has been statically allocated and should not be free.
 */
void flex_array_free_parts(struct flex_array *fa)
{
	int part_nr;
	int max_part = nr_base_part_ptrs();

	if (elements_fit_in_base(fa))
		return;
	for (part_nr = 0; part_nr < max_part; part_nr++)
		kfree(fa->parts[part_nr]);
}

void flex_array_free(struct flex_array *fa)
{
	flex_array_free_parts(fa);
	kfree(fa);
}

static unsigned int index_inside_part(struct flex_array *fa,
					unsigned int element_nr)
{
	unsigned int part_offset;

	part_offset = element_nr % __elements_per_part(fa->element_size);
	return part_offset * fa->element_size;
}

static struct flex_array_part *
__fa_get_part(struct flex_array *fa, int part_nr, gfp_t flags)
{
	struct flex_array_part *part = fa->parts[part_nr];
	if (!part) {
		part = kmalloc(sizeof(struct flex_array_part), flags);
		if (!part)
			return NULL;
		if (!(flags & __GFP_ZERO))
			memset(part, FLEX_ARRAY_FREE,
				sizeof(struct flex_array_part));
		fa->parts[part_nr] = part;
	}
	return part;
}

/**
 * flex_array_put - copy data into the array at @element_nr
 * @src:	address of data to copy into the array
 * @element_nr:	index of the position in which to insert
 * 		the new element.
 *
 * Note that this *copies* the contents of @src into
 * the array.  If you are trying to store an array of
 * pointers, make sure to pass in &ptr instead of ptr.
 *
 * Locking must be provided by the caller.
 */
int flex_array_put(struct flex_array *fa, unsigned int element_nr, void *src,
			gfp_t flags)
{
	int part_nr = fa_element_to_part_nr(fa, element_nr);
	struct flex_array_part *part;
	void *dst;

	if (element_nr >= fa->total_nr_elements)
		return -ENOSPC;
	if (elements_fit_in_base(fa))
		part = (struct flex_array_part *)&fa->parts[0];
	else {
		part = __fa_get_part(fa, part_nr, flags);
		if (!part)
			return -ENOMEM;
	}
	dst = &part->elements[index_inside_part(fa, element_nr)];
	memcpy(dst, src, fa->element_size);
	return 0;
}

/**
 * flex_array_clear - clear element in array at @element_nr
 * @element_nr:	index of the position to clear.
 *
 * Locking must be provided by the caller.
 */
int flex_array_clear(struct flex_array *fa, unsigned int element_nr)
{
	int part_nr = fa_element_to_part_nr(fa, element_nr);
	struct flex_array_part *part;
	void *dst;

	if (element_nr >= fa->total_nr_elements)
		return -ENOSPC;
	if (elements_fit_in_base(fa))
		part = (struct flex_array_part *)&fa->parts[0];
	else {
		part = fa->parts[part_nr];
		if (!part)
			return -EINVAL;
	}
	dst = &part->elements[index_inside_part(fa, element_nr)];
	memset(dst, FLEX_ARRAY_FREE, fa->element_size);
	return 0;
}

/**
 * flex_array_prealloc - guarantee that array space exists
 * @start:	index of first array element for which space is allocated
 * @end:	index of last (inclusive) element for which space is allocated
 *
 * This will guarantee that no future calls to flex_array_put()
 * will allocate memory.  It can be used if you are expecting to
 * be holding a lock or in some atomic context while writing
 * data into the array.
 *
 * Locking must be provided by the caller.
 */
int flex_array_prealloc(struct flex_array *fa, unsigned int start,
			unsigned int end, gfp_t flags)
{
	int start_part;
	int end_part;
	int part_nr;
	struct flex_array_part *part;

	if (start >= fa->total_nr_elements || end >= fa->total_nr_elements)
		return -ENOSPC;
	if (elements_fit_in_base(fa))
		return 0;
	start_part = fa_element_to_part_nr(fa, start);
	end_part = fa_element_to_part_nr(fa, end);
	for (part_nr = start_part; part_nr <= end_part; part_nr++) {
		part = __fa_get_part(fa, part_nr, flags);
		if (!part)
			return -ENOMEM;
	}
	return 0;
}

/**
 * flex_array_get - pull data back out of the array
 * @element_nr:	index of the element to fetch from the array
 *
 * Returns a pointer to the data at index @element_nr.  Note
 * that this is a copy of the data that was passed in.  If you
 * are using this to store pointers, you'll get back &ptr.
 *
 * Locking must be provided by the caller.
 */
void *flex_array_get(struct flex_array *fa, unsigned int element_nr)
{
	int part_nr = fa_element_to_part_nr(fa, element_nr);
	struct flex_array_part *part;

	if (element_nr >= fa->total_nr_elements)
		return NULL;
	if (elements_fit_in_base(fa))
		part = (struct flex_array_part *)&fa->parts[0];
	else {
		part = fa->parts[part_nr];
		if (!part)
			return NULL;
	}
	return &part->elements[index_inside_part(fa, element_nr)];
}
Commit	Line	Data
534acc05 DH	1	/*
	2	* Flexible array managed in PAGE_SIZE parts
	3	*
	4	* This program is free software; you can redistribute it and/or modify
	5	* it under the terms of the GNU General Public License as published by
	6	* the Free Software Foundation; either version 2 of the License, or
	7	* (at your option) any later version.
	8	*
	9	* This program is distributed in the hope that it will be useful,
	10	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	11	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	12	* GNU General Public License for more details.
	13	*
	14	* You should have received a copy of the GNU General Public License
	15	* along with this program; if not, write to the Free Software
	16	* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
	17	*
	18	* Copyright IBM Corporation, 2009
	19	*
	20	* Author: Dave Hansen <dave@linux.vnet.ibm.com>
	21	*/
	22
	23	#include <linux/flex_array.h>
	24	#include <linux/slab.h>
	25	#include <linux/stddef.h>
	26
	27	struct flex_array_part {
	28	char elements[FLEX_ARRAY_PART_SIZE];
	29	};
	30
	31	static inline int __elements_per_part(int element_size)
	32	{
	33	return FLEX_ARRAY_PART_SIZE / element_size;
	34	}
	35
	36	static inline int bytes_left_in_base(void)
	37	{
	38	int element_offset = offsetof(struct flex_array, parts);
	39	int bytes_left = FLEX_ARRAY_BASE_SIZE - element_offset;
	40	return bytes_left;
	41	}
	42
	43	static inline int nr_base_part_ptrs(void)
	44	{
	45	return bytes_left_in_base() / sizeof(struct flex_array_part *);
	46	}
	47
	48	/*
	49	* If a user requests an allocation which is small
	50	* enough, we may simply use the space in the
	51	* flex_array->parts[] array to store the user
	52	* data.
	53	*/
	54	static inline int elements_fit_in_base(struct flex_array *fa)
	55	{
	56	int data_size = fa->element_size * fa->total_nr_elements;
	57	if (data_size <= bytes_left_in_base())
	58	return 1;
	59	return 0;
	60	}
	61
	62	/**
	63	* flex_array_alloc - allocate a new flexible array
	64	* @element_size: the size of individual elements in the array
65	* @total: total number of elements that this should hold
66	*
67	* Note: all locking must be provided by the caller.
68	*
69	* @total is used to size internal structures. If the user ever
70	* accesses any array indexes >=@total, it will produce errors.
71	*
72	* The maximum number of elements is defined as: the number of
73	* elements that can be stored in a page times the number of
74	* page pointers that we can fit in the base structure or (using
75	* integer math):
76	*
77	* (PAGE_SIZE/element_size) * (PAGE_SIZE-8)/sizeof(void *)
78	*
79	* Here's a table showing example capacities. Note that the maximum
80	* index that the get/put() functions is just nr_objects-1. This
81	* basically means that you get 4MB of storage on 32-bit and 2MB on
82	* 64-bit.
83	*
84	*
85	* Element size \| Objects \| Objects \|
86	* PAGE_SIZE=4k \| 32-bit \| 64-bit \|
87	* ---------------------------------\|
88	* 1 bytes \| 4186112 \| 2093056 \|
89	* 2 bytes \| 2093056 \| 1046528 \|
90	* 3 bytes \| 1395030 \| 697515 \|
91	* 4 bytes \| 1046528 \| 523264 \|
92	* 32 bytes \| 130816 \| 65408 \|
93	* 33 bytes \| 126728 \| 63364 \|
94	* 2048 bytes \| 2044 \| 1022 \|
95	* 2049 bytes \| 1022 \| 511 \|
96	* void * \| 1046528 \| 261632 \|
97	*
98	* Since 64-bit pointers are twice the size, we lose half the
99	* capacity in the base structure. Also note that no effort is made
100	* to efficiently pack objects across page boundaries.
101	*/
b62e408c DR	102	struct flex_array *flex_array_alloc(int element_size, unsigned int total,
b62e408c DR	103	gfp_t flags)
534acc05 DH	104	{
	105	struct flex_array *ret;
	106	int max_size = nr_base_part_ptrs() * __elements_per_part(element_size);
	107
	108	/* max_size will end up 0 if element_size > PAGE_SIZE */
	109	if (total > max_size)
	110	return NULL;
	111	ret = kzalloc(sizeof(struct flex_array), flags);
	112	if (!ret)
	113	return NULL;
	114	ret->element_size = element_size;
	115	ret->total_nr_elements = total;
19da3dd1 DR	116	if (elements_fit_in_base(ret) && !(flags & __GFP_ZERO))
19da3dd1 DR	117	memset(ret->parts[0], FLEX_ARRAY_FREE, bytes_left_in_base());
534acc05 DH	118	return ret;
	119	}
	120
b62e408c DR	121	static int fa_element_to_part_nr(struct flex_array *fa,
b62e408c DR	122	unsigned int element_nr)
534acc05 DH	123	{
	124	return element_nr / __elements_per_part(fa->element_size);
	125	}
	126
	127	/**
	128	* flex_array_free_parts - just free the second-level pages
534acc05 DH	129	*
	130	* This is to be used in cases where the base 'struct flex_array'
	131	* has been statically allocated and should not be free.
	132	*/
	133	void flex_array_free_parts(struct flex_array *fa)
	134	{
	135	int part_nr;
	136	int max_part = nr_base_part_ptrs();
	137
	138	if (elements_fit_in_base(fa))
	139	return;
	140	for (part_nr = 0; part_nr < max_part; part_nr++)
	141	kfree(fa->parts[part_nr]);
	142	}
	143
	144	void flex_array_free(struct flex_array *fa)
	145	{
	146	flex_array_free_parts(fa);
	147	kfree(fa);
	148	}
	149
b62e408c DR	150	static unsigned int index_inside_part(struct flex_array *fa,
b62e408c DR	151	unsigned int element_nr)
534acc05	152	{
b62e408c	153	unsigned int part_offset;
534acc05	154
b62e408c	155	part_offset = element_nr % __elements_per_part(fa->element_size);
534acc05 DH	156	return part_offset * fa->element_size;
	157	}
	158
	159	static struct flex_array_part *
	160	__fa_get_part(struct flex_array *fa, int part_nr, gfp_t flags)
	161	{
	162	struct flex_array_part *part = fa->parts[part_nr];
	163	if (!part) {
19da3dd1	164	part = kmalloc(sizeof(struct flex_array_part), flags);
534acc05 DH	165	if (!part)
534acc05 DH	166	return NULL;
19da3dd1 DR	167	if (!(flags & __GFP_ZERO))
	168	memset(part, FLEX_ARRAY_FREE,
	169	sizeof(struct flex_array_part));
534acc05 DH	170	fa->parts[part_nr] = part;
	171	}
	172	return part;
	173	}
	174
	175	/**
	176	* flex_array_put - copy data into the array at @element_nr
	177	* @src: address of data to copy into the array
	178	* @element_nr: index of the position in which to insert
	179	* the new element.
	180	*
	181	* Note that this copies the contents of @src into
	182	* the array. If you are trying to store an array of
	183	* pointers, make sure to pass in &ptr instead of ptr.
	184	*
	185	* Locking must be provided by the caller.
	186	*/
b62e408c DR	187	int flex_array_put(struct flex_array fa, unsigned int element_nr, void src,
b62e408c DR	188	gfp_t flags)
534acc05 DH	189	{
	190	int part_nr = fa_element_to_part_nr(fa, element_nr);
	191	struct flex_array_part *part;
	192	void *dst;
	193
	194	if (element_nr >= fa->total_nr_elements)
	195	return -ENOSPC;
	196	if (elements_fit_in_base(fa))
	197	part = (struct flex_array_part *)&fa->parts[0];
a30b595d	198	else {
534acc05	199	part = __fa_get_part(fa, part_nr, flags);
a30b595d DR	200	if (!part)
	201	return -ENOMEM;
	202	}
534acc05 DH	203	dst = &part->elements[index_inside_part(fa, element_nr)];
	204	memcpy(dst, src, fa->element_size);
	205	return 0;
	206	}
	207
e6de3988 DR	208	/**
	209	* flex_array_clear - clear element in array at @element_nr
	210	* @element_nr: index of the position to clear.
	211	*
	212	* Locking must be provided by the caller.
	213	*/
	214	int flex_array_clear(struct flex_array *fa, unsigned int element_nr)
	215	{
	216	int part_nr = fa_element_to_part_nr(fa, element_nr);
	217	struct flex_array_part *part;
	218	void *dst;
	219
	220	if (element_nr >= fa->total_nr_elements)
	221	return -ENOSPC;
	222	if (elements_fit_in_base(fa))
	223	part = (struct flex_array_part *)&fa->parts[0];
	224	else {
	225	part = fa->parts[part_nr];
	226	if (!part)
	227	return -EINVAL;
	228	}
	229	dst = &part->elements[index_inside_part(fa, element_nr)];
19da3dd1	230	memset(dst, FLEX_ARRAY_FREE, fa->element_size);
e6de3988 DR	231	return 0;
	232	}
	233
534acc05 DH	234	/**
	235	* flex_array_prealloc - guarantee that array space exists
	236	* @start: index of first array element for which space is allocated
	237	* @end: index of last (inclusive) element for which space is allocated
	238	*
	239	* This will guarantee that no future calls to flex_array_put()
	240	* will allocate memory. It can be used if you are expecting to
	241	* be holding a lock or in some atomic context while writing
	242	* data into the array.
	243	*
	244	* Locking must be provided by the caller.
	245	*/
b62e408c DR	246	int flex_array_prealloc(struct flex_array *fa, unsigned int start,
b62e408c DR	247	unsigned int end, gfp_t flags)
534acc05 DH	248	{
	249	int start_part;
	250	int end_part;
	251	int part_nr;
	252	struct flex_array_part *part;
	253
	254	if (start >= fa->total_nr_elements \|\| end >= fa->total_nr_elements)
	255	return -ENOSPC;
	256	if (elements_fit_in_base(fa))
	257	return 0;
	258	start_part = fa_element_to_part_nr(fa, start);
	259	end_part = fa_element_to_part_nr(fa, end);
	260	for (part_nr = start_part; part_nr <= end_part; part_nr++) {
	261	part = __fa_get_part(fa, part_nr, flags);
	262	if (!part)
	263	return -ENOMEM;
	264	}
	265	return 0;
	266	}
	267
	268	/**
	269	* flex_array_get - pull data back out of the array
	270	* @element_nr: index of the element to fetch from the array
	271	*
	272	* Returns a pointer to the data at index @element_nr. Note
	273	* that this is a copy of the data that was passed in. If you
	274	* are using this to store pointers, you'll get back &ptr.
	275	*
	276	* Locking must be provided by the caller.
	277	*/
b62e408c	278	void flex_array_get(struct flex_array fa, unsigned int element_nr)
534acc05 DH	279	{
	280	int part_nr = fa_element_to_part_nr(fa, element_nr);
	281	struct flex_array_part *part;
534acc05 DH	282
	283	if (element_nr >= fa->total_nr_elements)
	284	return NULL;
534acc05 DH	285	if (elements_fit_in_base(fa))
534acc05 DH	286	part = (struct flex_array_part *)&fa->parts[0];
a30b595d	287	else {
534acc05	288	part = fa->parts[part_nr];
a30b595d DR	289	if (!part)
	290	return NULL;
	291	}
534acc05 DH	292	return &part->elements[index_inside_part(fa, element_nr)];
534acc05 DH	293	}