| /* |
| * 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; |
| } |