[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>
#include <linux/module.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
 * @flags:		page allocation flags to use for base array
 *
 * 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 = 0;

	if (element_size)
		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;
}
EXPORT_SYMBOL(flex_array_alloc);

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
 * @fa:		the flex array from which to free parts
 *
 * 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]);
}
EXPORT_SYMBOL(flex_array_free_parts);

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

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
 * @fa:		the flex array to copy data into
 * @element_nr:	index of the position in which to insert
 * 		the new element.
 * @src:	address of data to copy into the array
 * @flags:	page allocation flags to use for array expansion
 *
 *
 * 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.
 * You may instead wish to use the flex_array_put_ptr()
 * helper function.
 *
 * 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;
	struct flex_array_part *part;
	void *dst;

	if (element_nr >= fa->total_nr_elements)
		return -ENOSPC;
	if (!fa->element_size)
		return 0;
	if (elements_fit_in_base(fa))
		part = (struct flex_array_part *)&fa->parts[0];
	else {
		part_nr = fa_element_to_part_nr(fa, element_nr);
		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;
}
EXPORT_SYMBOL(flex_array_put);

/**
 * flex_array_clear - clear element in array at @element_nr
 * @fa:		the flex array of the element.
 * @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;
	struct flex_array_part *part;
	void *dst;

	if (element_nr >= fa->total_nr_elements)
		return -ENOSPC;
	if (!fa->element_size)
		return 0;
	if (elements_fit_in_base(fa))
		part = (struct flex_array_part *)&fa->parts[0];
	else {
		part_nr = fa_element_to_part_nr(fa, element_nr);
		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;
}
EXPORT_SYMBOL(flex_array_clear);

/**
 * flex_array_prealloc - guarantee that array space exists
 * @fa:			the flex array for which to preallocate parts
 * @start:		index of first array element for which space is allocated
 * @nr_elements:	number of elements for which space is allocated
 * @flags:		page allocation flags
 *
 * 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 nr_elements, gfp_t flags)
{
	int start_part;
	int end_part;
	int part_nr;
	unsigned int end;
	struct flex_array_part *part;

	if (!start && !nr_elements)
		return 0;
	if (start >= fa->total_nr_elements)
		return -ENOSPC;
	if (!nr_elements)
		return 0;

	end = start + nr_elements - 1;

	if (end >= fa->total_nr_elements)
		return -ENOSPC;
	if (!fa->element_size)
		return 0;
	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;
}
EXPORT_SYMBOL(flex_array_prealloc);

/**
 * flex_array_get - pull data back out of the array
 * @fa:		the flex array from which to extract data
 * @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.  You
 * may instead wish to use the flex_array_get_ptr helper.
 *
 * Locking must be provided by the caller.
 */
void *flex_array_get(struct flex_array *fa, unsigned int element_nr)
{
	int part_nr;
	struct flex_array_part *part;

	if (!fa->element_size)
		return NULL;
	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_nr = fa_element_to_part_nr(fa, element_nr);
		part = fa->parts[part_nr];
		if (!part)
			return NULL;
	}
	return &part->elements[index_inside_part(fa, element_nr)];
}
EXPORT_SYMBOL(flex_array_get);

/**
 * flex_array_get_ptr - pull a ptr back out of the array
 * @fa:		the flex array from which to extract data
 * @element_nr:	index of the element to fetch from the array
 *
 * Returns the pointer placed in the flex array at element_nr using
 * flex_array_put_ptr().  This function should not be called if the
 * element in question was not set using the _put_ptr() helper.
 */
void *flex_array_get_ptr(struct flex_array *fa, unsigned int element_nr)
{
	void **tmp;

	tmp = flex_array_get(fa, element_nr);
	if (!tmp)
		return NULL;

	return *tmp;
}
EXPORT_SYMBOL(flex_array_get_ptr);

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
 * @fa:		the flex array to shrink
 *
 * 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 (!fa->total_nr_elements || !fa->element_size)
		return 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;
}
EXPORT_SYMBOL(flex_array_shrink);
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>
78c377d1	26	#include <linux/module.h>
534acc05 DH	27
	28	struct flex_array_part {
	29	char elements[FLEX_ARRAY_PART_SIZE];
	30	};
	31
534acc05 DH	32	/*
	33	* If a user requests an allocation which is small
	34	* enough, we may simply use the space in the
	35	* flex_array->parts[] array to store the user
	36	* data.
	37	*/
	38	static inline int elements_fit_in_base(struct flex_array *fa)
	39	{
	40	int data_size = fa->element_size * fa->total_nr_elements;
45b588d6	41	if (data_size <= FLEX_ARRAY_BASE_BYTES_LEFT)
534acc05 DH	42	return 1;
	43	return 0;
	44	}
	45
	46	/**
	47	* flex_array_alloc - allocate a new flexible array
	48	* @element_size: the size of individual elements in the array
	49	* @total: total number of elements that this should hold
fc0d8d94	50	* @flags: page allocation flags to use for base array
534acc05 DH	51	*
	52	* Note: all locking must be provided by the caller.
	53	*
	54	* @total is used to size internal structures. If the user ever
	55	* accesses any array indexes >=@total, it will produce errors.
	56	*
	57	* The maximum number of elements is defined as: the number of
	58	* elements that can be stored in a page times the number of
	59	* page pointers that we can fit in the base structure or (using
	60	* integer math):
	61	*
	62	* (PAGE_SIZE/element_size) * (PAGE_SIZE-8)/sizeof(void *)
	63	*
	64	* Here's a table showing example capacities. Note that the maximum
	65	* index that the get/put() functions is just nr_objects-1. This
	66	* basically means that you get 4MB of storage on 32-bit and 2MB on
	67	* 64-bit.
	68	*
	69	*
	70	* Element size \| Objects \| Objects \|
	71	* PAGE_SIZE=4k \| 32-bit \| 64-bit \|
	72	* ---------------------------------\|
	73	* 1 bytes \| 4186112 \| 2093056 \|
	74	* 2 bytes \| 2093056 \| 1046528 \|
	75	* 3 bytes \| 1395030 \| 697515 \|
	76	* 4 bytes \| 1046528 \| 523264 \|
	77	* 32 bytes \| 130816 \| 65408 \|
	78	* 33 bytes \| 126728 \| 63364 \|
	79	* 2048 bytes \| 2044 \| 1022 \|
	80	* 2049 bytes \| 1022 \| 511 \|
	81	* void * \| 1046528 \| 261632 \|
	82	*
	83	* Since 64-bit pointers are twice the size, we lose half the
	84	* capacity in the base structure. Also note that no effort is made
	85	* to efficiently pack objects across page boundaries.
	86	*/
b62e408c DR	87	struct flex_array *flex_array_alloc(int element_size, unsigned int total,
b62e408c DR	88	gfp_t flags)
534acc05 DH	89	{
534acc05 DH	90	struct flex_array *ret;
a8d05c81 EP	91	int max_size = 0;
	92
	93	if (element_size)
	94	max_size = FLEX_ARRAY_NR_BASE_PTRS *
	95	FLEX_ARRAY_ELEMENTS_PER_PART(element_size);
534acc05 DH	96
	97	/* max_size will end up 0 if element_size > PAGE_SIZE */
	98	if (total > max_size)
	99	return NULL;
	100	ret = kzalloc(sizeof(struct flex_array), flags);
	101	if (!ret)
	102	return NULL;
	103	ret->element_size = element_size;
	104	ret->total_nr_elements = total;
19da3dd1	105	if (elements_fit_in_base(ret) && !(flags & __GFP_ZERO))
e59464c7	106	memset(&ret->parts[0], FLEX_ARRAY_FREE,
45b588d6	107	FLEX_ARRAY_BASE_BYTES_LEFT);
534acc05 DH	108	return ret;
534acc05 DH	109	}
78c377d1	110	EXPORT_SYMBOL(flex_array_alloc);
534acc05	111
b62e408c DR	112	static int fa_element_to_part_nr(struct flex_array *fa,
b62e408c DR	113	unsigned int element_nr)
534acc05	114	{
45b588d6	115	return element_nr / FLEX_ARRAY_ELEMENTS_PER_PART(fa->element_size);
534acc05 DH	116	}
	117
	118	/**
	119	* flex_array_free_parts - just free the second-level pages
fc0d8d94	120	* @fa: the flex array from which to free parts
534acc05 DH	121	*
	122	* This is to be used in cases where the base 'struct flex_array'
	123	* has been statically allocated and should not be free.
	124	*/
	125	void flex_array_free_parts(struct flex_array *fa)
	126	{
	127	int part_nr;
534acc05 DH	128
	129	if (elements_fit_in_base(fa))
	130	return;
45b588d6	131	for (part_nr = 0; part_nr < FLEX_ARRAY_NR_BASE_PTRS; part_nr++)
534acc05 DH	132	kfree(fa->parts[part_nr]);
534acc05 DH	133	}
78c377d1	134	EXPORT_SYMBOL(flex_array_free_parts);
534acc05 DH	135
	136	void flex_array_free(struct flex_array *fa)
	137	{
	138	flex_array_free_parts(fa);
	139	kfree(fa);
	140	}
78c377d1	141	EXPORT_SYMBOL(flex_array_free);
534acc05	142
b62e408c DR	143	static unsigned int index_inside_part(struct flex_array *fa,
b62e408c DR	144	unsigned int element_nr)
534acc05	145	{
b62e408c	146	unsigned int part_offset;
534acc05	147
45b588d6 DR	148	part_offset = element_nr %
45b588d6 DR	149	FLEX_ARRAY_ELEMENTS_PER_PART(fa->element_size);
534acc05 DH	150	return part_offset * fa->element_size;
	151	}
	152
	153	static struct flex_array_part *
	154	__fa_get_part(struct flex_array *fa, int part_nr, gfp_t flags)
	155	{
	156	struct flex_array_part *part = fa->parts[part_nr];
	157	if (!part) {
19da3dd1	158	part = kmalloc(sizeof(struct flex_array_part), flags);
534acc05 DH	159	if (!part)
534acc05 DH	160	return NULL;
19da3dd1 DR	161	if (!(flags & __GFP_ZERO))
	162	memset(part, FLEX_ARRAY_FREE,
	163	sizeof(struct flex_array_part));
534acc05 DH	164	fa->parts[part_nr] = part;
	165	}
	166	return part;
	167	}
	168
	169	/**
	170	* flex_array_put - copy data into the array at @element_nr
fc0d8d94	171	* @fa: the flex array to copy data into
534acc05 DH	172	* @element_nr: index of the position in which to insert
534acc05 DH	173	* the new element.
fc0d8d94 DR	174	* @src: address of data to copy into the array
	175	* @flags: page allocation flags to use for array expansion
	176	*
534acc05 DH	177	*
	178	* Note that this copies the contents of @src into
	179	* the array. If you are trying to store an array of
	180	* pointers, make sure to pass in &ptr instead of ptr.
ea98eed9 EP	181	* You may instead wish to use the flex_array_put_ptr()
ea98eed9 EP	182	* helper function.
534acc05 DH	183	*
	184	* Locking must be provided by the caller.
	185	*/
b62e408c DR	186	int flex_array_put(struct flex_array fa, unsigned int element_nr, void src,
b62e408c DR	187	gfp_t flags)
534acc05	188	{
a8d05c81	189	int part_nr;
534acc05 DH	190	struct flex_array_part *part;
	191	void *dst;
	192
	193	if (element_nr >= fa->total_nr_elements)
	194	return -ENOSPC;
a8d05c81 EP	195	if (!fa->element_size)
a8d05c81 EP	196	return 0;
534acc05 DH	197	if (elements_fit_in_base(fa))
534acc05 DH	198	part = (struct flex_array_part *)&fa->parts[0];
a30b595d	199	else {
a8d05c81	200	part_nr = fa_element_to_part_nr(fa, element_nr);
534acc05	201	part = __fa_get_part(fa, part_nr, flags);
a30b595d DR	202	if (!part)
	203	return -ENOMEM;
	204	}
534acc05 DH	205	dst = &part->elements[index_inside_part(fa, element_nr)];
	206	memcpy(dst, src, fa->element_size);
	207	return 0;
	208	}
78c377d1	209	EXPORT_SYMBOL(flex_array_put);
534acc05	210
e6de3988 DR	211	/**
e6de3988 DR	212	* flex_array_clear - clear element in array at @element_nr
fc0d8d94	213	* @fa: the flex array of the element.
e6de3988 DR	214	* @element_nr: index of the position to clear.
	215	*
	216	* Locking must be provided by the caller.
	217	*/
	218	int flex_array_clear(struct flex_array *fa, unsigned int element_nr)
	219	{
a8d05c81	220	int part_nr;
e6de3988 DR	221	struct flex_array_part *part;
	222	void *dst;
	223
	224	if (element_nr >= fa->total_nr_elements)
	225	return -ENOSPC;
a8d05c81 EP	226	if (!fa->element_size)
a8d05c81 EP	227	return 0;
e6de3988 DR	228	if (elements_fit_in_base(fa))
	229	part = (struct flex_array_part *)&fa->parts[0];
	230	else {
a8d05c81	231	part_nr = fa_element_to_part_nr(fa, element_nr);
e6de3988 DR	232	part = fa->parts[part_nr];
	233	if (!part)
	234	return -EINVAL;
	235	}
	236	dst = &part->elements[index_inside_part(fa, element_nr)];
19da3dd1	237	memset(dst, FLEX_ARRAY_FREE, fa->element_size);
e6de3988 DR	238	return 0;
e6de3988 DR	239	}
78c377d1	240	EXPORT_SYMBOL(flex_array_clear);
e6de3988	241
534acc05 DH	242	/**
534acc05 DH	243	* flex_array_prealloc - guarantee that array space exists
5a3ea878 EP	244	* @fa: the flex array for which to preallocate parts
	245	* @start: index of first array element for which space is allocated
	246	* @nr_elements: number of elements for which space is allocated
	247	* @flags: page allocation flags
534acc05 DH	248	*
	249	* This will guarantee that no future calls to flex_array_put()
	250	* will allocate memory. It can be used if you are expecting to
	251	* be holding a lock or in some atomic context while writing
	252	* data into the array.
	253	*
	254	* Locking must be provided by the caller.
	255	*/
b62e408c	256	int flex_array_prealloc(struct flex_array *fa, unsigned int start,
5a3ea878	257	unsigned int nr_elements, gfp_t flags)
534acc05 DH	258	{
	259	int start_part;
	260	int end_part;
	261	int part_nr;
5a3ea878	262	unsigned int end;
534acc05 DH	263	struct flex_array_part *part;
534acc05 DH	264
150cdf6e EP	265	if (!start && !nr_elements)
	266	return 0;
	267	if (start >= fa->total_nr_elements)
	268	return -ENOSPC;
	269	if (!nr_elements)
	270	return 0;
	271
5a3ea878 EP	272	end = start + nr_elements - 1;
5a3ea878 EP	273
150cdf6e	274	if (end >= fa->total_nr_elements)
534acc05	275	return -ENOSPC;
a8d05c81 EP	276	if (!fa->element_size)
a8d05c81 EP	277	return 0;
534acc05 DH	278	if (elements_fit_in_base(fa))
	279	return 0;
	280	start_part = fa_element_to_part_nr(fa, start);
	281	end_part = fa_element_to_part_nr(fa, end);
	282	for (part_nr = start_part; part_nr <= end_part; part_nr++) {
	283	part = __fa_get_part(fa, part_nr, flags);
	284	if (!part)
	285	return -ENOMEM;
	286	}
	287	return 0;
	288	}
78c377d1	289	EXPORT_SYMBOL(flex_array_prealloc);
534acc05 DH	290
	291	/**
	292	* flex_array_get - pull data back out of the array
fc0d8d94	293	* @fa: the flex array from which to extract data
534acc05 DH	294	* @element_nr: index of the element to fetch from the array
	295	*
	296	* Returns a pointer to the data at index @element_nr. Note
	297	* that this is a copy of the data that was passed in. If you
ea98eed9 EP	298	* are using this to store pointers, you'll get back &ptr. You
ea98eed9 EP	299	* may instead wish to use the flex_array_get_ptr helper.
534acc05 DH	300	*
	301	* Locking must be provided by the caller.
	302	*/
b62e408c	303	void flex_array_get(struct flex_array fa, unsigned int element_nr)
534acc05	304	{
a8d05c81	305	int part_nr;
534acc05	306	struct flex_array_part *part;
534acc05	307
a8d05c81 EP	308	if (!fa->element_size)
a8d05c81 EP	309	return NULL;
534acc05 DH	310	if (element_nr >= fa->total_nr_elements)
534acc05 DH	311	return NULL;
534acc05 DH	312	if (elements_fit_in_base(fa))
534acc05 DH	313	part = (struct flex_array_part *)&fa->parts[0];
a30b595d	314	else {
a8d05c81	315	part_nr = fa_element_to_part_nr(fa, element_nr);
534acc05	316	part = fa->parts[part_nr];
a30b595d DR	317	if (!part)
	318	return NULL;
	319	}
534acc05 DH	320	return &part->elements[index_inside_part(fa, element_nr)];
534acc05 DH	321	}
78c377d1	322	EXPORT_SYMBOL(flex_array_get);
4af5a2f7	323
ea98eed9 EP	324	/**
	325	* flex_array_get_ptr - pull a ptr back out of the array
	326	* @fa: the flex array from which to extract data
	327	* @element_nr: index of the element to fetch from the array
	328	*
	329	* Returns the pointer placed in the flex array at element_nr using
	330	* flex_array_put_ptr(). This function should not be called if the
	331	* element in question was not set using the _put_ptr() helper.
	332	*/
	333	void flex_array_get_ptr(struct flex_array fa, unsigned int element_nr)
	334	{
	335	void **tmp;
	336
	337	tmp = flex_array_get(fa, element_nr);
	338	if (!tmp)
	339	return NULL;
	340
	341	return *tmp;
	342	}
78c377d1	343	EXPORT_SYMBOL(flex_array_get_ptr);
ea98eed9	344
4af5a2f7 DR	345	static int part_is_free(struct flex_array_part *part)
	346	{
	347	int i;
	348
	349	for (i = 0; i < sizeof(struct flex_array_part); i++)
	350	if (part->elements[i] != FLEX_ARRAY_FREE)
	351	return 0;
	352	return 1;
	353	}
	354
	355	/**
	356	* flex_array_shrink - free unused second-level pages
fc0d8d94	357	* @fa: the flex array to shrink
4af5a2f7 DR	358	*
	359	* Frees all second-level pages that consist solely of unused
	360	* elements. Returns the number of pages freed.
	361	*
	362	* Locking must be provided by the caller.
	363	*/
	364	int flex_array_shrink(struct flex_array *fa)
	365	{
	366	struct flex_array_part *part;
4af5a2f7 DR	367	int part_nr;
	368	int ret = 0;
	369
a8d05c81	370	if (!fa->total_nr_elements \|\| !fa->element_size)
150cdf6e	371	return 0;
4af5a2f7 DR	372	if (elements_fit_in_base(fa))
4af5a2f7 DR	373	return ret;
45b588d6	374	for (part_nr = 0; part_nr < FLEX_ARRAY_NR_BASE_PTRS; part_nr++) {
4af5a2f7 DR	375	part = fa->parts[part_nr];
	376	if (!part)
	377	continue;
	378	if (part_is_free(part)) {
	379	fa->parts[part_nr] = NULL;
	380	kfree(part);
	381	ret++;
	382	}
	383	}
	384	return ret;
	385	}
78c377d1	386	EXPORT_SYMBOL(flex_array_shrink);