/* * 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;	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) {		/*		 * This leaves the part pages uninitialized		 * and with potentially random data, just		 * as if the user had kmalloc()'d the whole.		 * __GFP_ZERO can be used to zero it.		 */		part = kmalloc(FLEX_ARRAY_PART_SIZE, flags);		if (!part)			return NULL;		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_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)];}