[GitHub/mt8127/android_kernel_alcatel_ttab.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];
};

/*
 * 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 <= FLEX_ARRAY_BASE_BYTES_LEFT)
		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 = FLEX_ARRAY_NR_BASE_PTRS *
				FLEX_ARRAY_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,
						FLEX_ARRAY_BASE_BYTES_LEFT);
	return ret;
}

static int fa_element_to_part_nr(struct flex_array *fa,
					unsigned int element_nr)
{
	return element_nr / FLEX_ARRAY_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;

	if (elements_fit_in_base(fa))
		return;
	for (part_nr = 0; part_nr < FLEX_ARRAY_NR_BASE_PTRS; 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 %
				FLEX_ARRAY_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)];
}

static int part_is_free(struct flex_array_part *part)
{
	int i;

	for (i = 0; i < sizeof(struct flex_array_part); i++)
		if (part->elements[i] != FLEX_ARRAY_FREE)
			return 0;
	return 1;
}

/**
 * flex_array_shrink - free unused second-level pages
 *
 * Frees all second-level pages that consist solely of unused
 * elements.  Returns the number of pages freed.
 *
 * Locking must be provided by the caller.
 */
int flex_array_shrink(struct flex_array *fa)
{
	struct flex_array_part *part;
	int part_nr;
	int ret = 0;

	if (elements_fit_in_base(fa))
		return ret;
	for (part_nr = 0; part_nr < FLEX_ARRAY_NR_BASE_PTRS; part_nr++) {
		part = fa->parts[part_nr];
		if (!part)
			continue;
		if (part_is_free(part)) {
			fa->parts[part_nr] = NULL;
			kfree(part);
			ret++;
		}
	}
	return ret;
}
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
534acc05 DH	31	/*
	32	* If a user requests an allocation which is small
	33	* enough, we may simply use the space in the
	34	* flex_array->parts[] array to store the user
	35	* data.
	36	*/
	37	static inline int elements_fit_in_base(struct flex_array *fa)
	38	{
	39	int data_size = fa->element_size * fa->total_nr_elements;
45b588d6	40	if (data_size <= FLEX_ARRAY_BASE_BYTES_LEFT)
534acc05 DH	41	return 1;
	42	return 0;
	43	}
	44
	45	/**
	46	* flex_array_alloc - allocate a new flexible array
	47	* @element_size: the size of individual elements in the array
	48	* @total: total number of elements that this should hold
	49	*
	50	* Note: all locking must be provided by the caller.
	51	*
	52	* @total is used to size internal structures. If the user ever
	53	* accesses any array indexes >=@total, it will produce errors.
	54	*
	55	* The maximum number of elements is defined as: the number of
	56	* elements that can be stored in a page times the number of
	57	* page pointers that we can fit in the base structure or (using
	58	* integer math):
	59	*
	60	* (PAGE_SIZE/element_size) * (PAGE_SIZE-8)/sizeof(void *)
	61	*
	62	* Here's a table showing example capacities. Note that the maximum
	63	* index that the get/put() functions is just nr_objects-1. This
	64	* basically means that you get 4MB of storage on 32-bit and 2MB on
	65	* 64-bit.
	66	*
	67	*
	68	* Element size \| Objects \| Objects \|
	69	* PAGE_SIZE=4k \| 32-bit \| 64-bit \|
	70	* ---------------------------------\|
	71	* 1 bytes \| 4186112 \| 2093056 \|
	72	* 2 bytes \| 2093056 \| 1046528 \|
	73	* 3 bytes \| 1395030 \| 697515 \|
	74	* 4 bytes \| 1046528 \| 523264 \|
	75	* 32 bytes \| 130816 \| 65408 \|
	76	* 33 bytes \| 126728 \| 63364 \|
	77	* 2048 bytes \| 2044 \| 1022 \|
	78	* 2049 bytes \| 1022 \| 511 \|
	79	* void * \| 1046528 \| 261632 \|
	80	*
	81	* Since 64-bit pointers are twice the size, we lose half the
	82	* capacity in the base structure. Also note that no effort is made
	83	* to efficiently pack objects across page boundaries.
	84	*/
b62e408c DR	85	struct flex_array *flex_array_alloc(int element_size, unsigned int total,
b62e408c DR	86	gfp_t flags)
534acc05 DH	87	{
534acc05 DH	88	struct flex_array *ret;
45b588d6 DR	89	int max_size = FLEX_ARRAY_NR_BASE_PTRS *
45b588d6 DR	90	FLEX_ARRAY_ELEMENTS_PER_PART(element_size);
534acc05 DH	91
	92	/* max_size will end up 0 if element_size > PAGE_SIZE */
	93	if (total > max_size)
	94	return NULL;
	95	ret = kzalloc(sizeof(struct flex_array), flags);
	96	if (!ret)
	97	return NULL;
	98	ret->element_size = element_size;
	99	ret->total_nr_elements = total;
19da3dd1	100	if (elements_fit_in_base(ret) && !(flags & __GFP_ZERO))
45b588d6 DR	101	memset(ret->parts[0], FLEX_ARRAY_FREE,
45b588d6 DR	102	FLEX_ARRAY_BASE_BYTES_LEFT);
534acc05 DH	103	return ret;
	104	}
	105
b62e408c DR	106	static int fa_element_to_part_nr(struct flex_array *fa,
b62e408c DR	107	unsigned int element_nr)
534acc05	108	{
45b588d6	109	return element_nr / FLEX_ARRAY_ELEMENTS_PER_PART(fa->element_size);
534acc05 DH	110	}
	111
	112	/**
	113	* flex_array_free_parts - just free the second-level pages
534acc05 DH	114	*
	115	* This is to be used in cases where the base 'struct flex_array'
	116	* has been statically allocated and should not be free.
	117	*/
	118	void flex_array_free_parts(struct flex_array *fa)
	119	{
	120	int part_nr;
534acc05 DH	121
	122	if (elements_fit_in_base(fa))
	123	return;
45b588d6	124	for (part_nr = 0; part_nr < FLEX_ARRAY_NR_BASE_PTRS; part_nr++)
534acc05 DH	125	kfree(fa->parts[part_nr]);
	126	}
	127
	128	void flex_array_free(struct flex_array *fa)
	129	{
	130	flex_array_free_parts(fa);
	131	kfree(fa);
	132	}
	133
b62e408c DR	134	static unsigned int index_inside_part(struct flex_array *fa,
b62e408c DR	135	unsigned int element_nr)
534acc05	136	{
b62e408c	137	unsigned int part_offset;
534acc05	138
45b588d6 DR	139	part_offset = element_nr %
45b588d6 DR	140	FLEX_ARRAY_ELEMENTS_PER_PART(fa->element_size);
534acc05 DH	141	return part_offset * fa->element_size;
	142	}
	143
	144	static struct flex_array_part *
	145	__fa_get_part(struct flex_array *fa, int part_nr, gfp_t flags)
	146	{
	147	struct flex_array_part *part = fa->parts[part_nr];
	148	if (!part) {
19da3dd1	149	part = kmalloc(sizeof(struct flex_array_part), flags);
534acc05 DH	150	if (!part)
534acc05 DH	151	return NULL;
19da3dd1 DR	152	if (!(flags & __GFP_ZERO))
	153	memset(part, FLEX_ARRAY_FREE,
	154	sizeof(struct flex_array_part));
534acc05 DH	155	fa->parts[part_nr] = part;
	156	}
	157	return part;
	158	}
	159
	160	/**
	161	* flex_array_put - copy data into the array at @element_nr
	162	* @src: address of data to copy into the array
	163	* @element_nr: index of the position in which to insert
	164	* the new element.
	165	*
	166	* Note that this copies the contents of @src into
	167	* the array. If you are trying to store an array of
	168	* pointers, make sure to pass in &ptr instead of ptr.
	169	*
	170	* Locking must be provided by the caller.
	171	*/
b62e408c DR	172	int flex_array_put(struct flex_array fa, unsigned int element_nr, void src,
b62e408c DR	173	gfp_t flags)
534acc05 DH	174	{
	175	int part_nr = fa_element_to_part_nr(fa, element_nr);
	176	struct flex_array_part *part;
	177	void *dst;
	178
	179	if (element_nr >= fa->total_nr_elements)
	180	return -ENOSPC;
	181	if (elements_fit_in_base(fa))
	182	part = (struct flex_array_part *)&fa->parts[0];
a30b595d	183	else {
534acc05	184	part = __fa_get_part(fa, part_nr, flags);
a30b595d DR	185	if (!part)
	186	return -ENOMEM;
	187	}
534acc05 DH	188	dst = &part->elements[index_inside_part(fa, element_nr)];
	189	memcpy(dst, src, fa->element_size);
	190	return 0;
	191	}
	192
e6de3988 DR	193	/**
	194	* flex_array_clear - clear element in array at @element_nr
	195	* @element_nr: index of the position to clear.
	196	*
	197	* Locking must be provided by the caller.
	198	*/
	199	int flex_array_clear(struct flex_array *fa, unsigned int element_nr)
	200	{
	201	int part_nr = fa_element_to_part_nr(fa, element_nr);
	202	struct flex_array_part *part;
	203	void *dst;
	204
	205	if (element_nr >= fa->total_nr_elements)
	206	return -ENOSPC;
	207	if (elements_fit_in_base(fa))
	208	part = (struct flex_array_part *)&fa->parts[0];
	209	else {
	210	part = fa->parts[part_nr];
	211	if (!part)
	212	return -EINVAL;
	213	}
	214	dst = &part->elements[index_inside_part(fa, element_nr)];
19da3dd1	215	memset(dst, FLEX_ARRAY_FREE, fa->element_size);
e6de3988 DR	216	return 0;
	217	}
	218
534acc05 DH	219	/**
	220	* flex_array_prealloc - guarantee that array space exists
	221	* @start: index of first array element for which space is allocated
	222	* @end: index of last (inclusive) element for which space is allocated
	223	*
	224	* This will guarantee that no future calls to flex_array_put()
	225	* will allocate memory. It can be used if you are expecting to
	226	* be holding a lock or in some atomic context while writing
	227	* data into the array.
	228	*
	229	* Locking must be provided by the caller.
	230	*/
b62e408c DR	231	int flex_array_prealloc(struct flex_array *fa, unsigned int start,
b62e408c DR	232	unsigned int end, gfp_t flags)
534acc05 DH	233	{
	234	int start_part;
	235	int end_part;
	236	int part_nr;
	237	struct flex_array_part *part;
	238
	239	if (start >= fa->total_nr_elements \|\| end >= fa->total_nr_elements)
	240	return -ENOSPC;
	241	if (elements_fit_in_base(fa))
	242	return 0;
	243	start_part = fa_element_to_part_nr(fa, start);
	244	end_part = fa_element_to_part_nr(fa, end);
	245	for (part_nr = start_part; part_nr <= end_part; part_nr++) {
	246	part = __fa_get_part(fa, part_nr, flags);
	247	if (!part)
	248	return -ENOMEM;
	249	}
	250	return 0;
	251	}
	252
	253	/**
	254	* flex_array_get - pull data back out of the array
	255	* @element_nr: index of the element to fetch from the array
	256	*
	257	* Returns a pointer to the data at index @element_nr. Note
	258	* that this is a copy of the data that was passed in. If you
	259	* are using this to store pointers, you'll get back &ptr.
	260	*
	261	* Locking must be provided by the caller.
	262	*/
b62e408c	263	void flex_array_get(struct flex_array fa, unsigned int element_nr)
534acc05 DH	264	{
	265	int part_nr = fa_element_to_part_nr(fa, element_nr);
	266	struct flex_array_part *part;
534acc05 DH	267
	268	if (element_nr >= fa->total_nr_elements)
	269	return NULL;
534acc05 DH	270	if (elements_fit_in_base(fa))
534acc05 DH	271	part = (struct flex_array_part *)&fa->parts[0];
a30b595d	272	else {
534acc05	273	part = fa->parts[part_nr];
a30b595d DR	274	if (!part)
	275	return NULL;
	276	}
534acc05 DH	277	return &part->elements[index_inside_part(fa, element_nr)];
534acc05 DH	278	}
4af5a2f7 DR	279
	280	static int part_is_free(struct flex_array_part *part)
	281	{
	282	int i;
	283
	284	for (i = 0; i < sizeof(struct flex_array_part); i++)
	285	if (part->elements[i] != FLEX_ARRAY_FREE)
	286	return 0;
	287	return 1;
	288	}
	289
	290	/**
	291	* flex_array_shrink - free unused second-level pages
	292	*
	293	* Frees all second-level pages that consist solely of unused
	294	* elements. Returns the number of pages freed.
	295	*
	296	* Locking must be provided by the caller.
	297	*/
	298	int flex_array_shrink(struct flex_array *fa)
	299	{
	300	struct flex_array_part *part;
4af5a2f7 DR	301	int part_nr;
	302	int ret = 0;
	303
	304	if (elements_fit_in_base(fa))
	305	return ret;
45b588d6	306	for (part_nr = 0; part_nr < FLEX_ARRAY_NR_BASE_PTRS; part_nr++) {
4af5a2f7 DR	307	part = fa->parts[part_nr];
	308	if (!part)
	309	continue;
	310	if (part_is_free(part)) {
	311	fa->parts[part_nr] = NULL;
	312	kfree(part);
	313	ret++;
	314	}
	315	}
	316	return ret;
	317	}