linux-yocto-4.8 - Linux 4.8 Embedded Kernel

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/* * 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/export.h> #include <linux/reciprocal_div.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 | 4177920 | 2088960 | * 2 bytes | 2088960 | 1044480 | * 3 bytes | 1392300 | 696150 | * 4 bytes | 1044480 | 522240 | * 32 bytes | 130560 | 65408 | * 33 bytes | 126480 | 63240 | * 2048 bytes | 2040 | 1020 | * 2049 bytes | 1020 | 510 | * void * | 1044480 | 261120 | * * 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 elems_per_part = 0; int max_size = 0; struct reciprocal_value reciprocal_elems = { 0 }; if (element_size) { elems_per_part = FLEX_ARRAY_ELEMENTS_PER_PART(element_size); reciprocal_elems = reciprocal_value(elems_per_part); max_size = FLEX_ARRAY_NR_BASE_PTRS * elems_per_part; } /* 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; ret->elems_per_part = elems_per_part; ret->reciprocal_elems = reciprocal_elems; 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) { /* * if element_size == 0 we don't get here, so we never touch * the zeroed fa->reciprocal_elems, which would yield invalid * results */ return reciprocal_divide(element_nr, fa->reciprocal_elems); } /** * 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_nr) { unsigned int part_offset; part_offset = element_nr - part_nr * fa->elems_per_part; 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 = 0; 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, part_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 = 0; 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, part_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 = 0; 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, part_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);


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