757 lines
17 KiB
C
757 lines
17 KiB
C
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/*
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* zsmalloc memory allocator
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*
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* Copyright (C) 2011 Nitin Gupta
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*
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* This code is released using a dual license strategy: BSD/GPL
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* You can choose the license that better fits your requirements.
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*
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* Released under the terms of 3-clause BSD License
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* Released under the terms of GNU General Public License Version 2.0
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*/
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#ifdef CONFIG_ZSMALLOC_DEBUG
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#define DEBUG
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#endif
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/bitops.h>
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#include <linux/errno.h>
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#include <linux/highmem.h>
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#include <linux/init.h>
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#include <linux/string.h>
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#include <linux/slab.h>
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#include <asm/tlbflush.h>
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#include <asm/pgtable.h>
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#include <linux/cpumask.h>
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#include <linux/cpu.h>
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#include "zsmalloc.h"
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#include "zsmalloc_int.h"
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/*
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* A zspage's class index and fullness group
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* are encoded in its (first)page->mapping
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*/
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#define CLASS_IDX_BITS 28
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#define FULLNESS_BITS 4
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#define CLASS_IDX_MASK ((1 << CLASS_IDX_BITS) - 1)
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#define FULLNESS_MASK ((1 << FULLNESS_BITS) - 1)
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/*
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* Object location (<PFN>, <obj_idx>) is encoded as
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* as single (void *) handle value.
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*
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* Note that object index <obj_idx> is relative to system
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* page <PFN> it is stored in, so for each sub-page belonging
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* to a zspage, obj_idx starts with 0.
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*/
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#define _PFN_BITS (MAX_PHYSMEM_BITS - PAGE_SHIFT)
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#define OBJ_INDEX_BITS (BITS_PER_LONG - _PFN_BITS)
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#define OBJ_INDEX_MASK ((_AC(1, UL) << OBJ_INDEX_BITS) - 1)
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/* per-cpu VM mapping areas for zspage accesses that cross page boundaries */
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static DEFINE_PER_CPU(struct mapping_area, zs_map_area);
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static int is_first_page(struct page *page)
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{
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return test_bit(PG_private, &page->flags);
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}
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static int is_last_page(struct page *page)
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{
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return test_bit(PG_private_2, &page->flags);
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}
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static void get_zspage_mapping(struct page *page, unsigned int *class_idx,
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enum fullness_group *fullness)
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{
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unsigned long m;
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BUG_ON(!is_first_page(page));
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m = (unsigned long)page->mapping;
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*fullness = m & FULLNESS_MASK;
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*class_idx = (m >> FULLNESS_BITS) & CLASS_IDX_MASK;
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}
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static void set_zspage_mapping(struct page *page, unsigned int class_idx,
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enum fullness_group fullness)
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{
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unsigned long m;
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BUG_ON(!is_first_page(page));
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m = ((class_idx & CLASS_IDX_MASK) << FULLNESS_BITS) |
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(fullness & FULLNESS_MASK);
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page->mapping = (struct address_space *)m;
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}
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static int get_size_class_index(int size)
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{
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int idx = 0;
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if (likely(size > ZS_MIN_ALLOC_SIZE))
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idx = DIV_ROUND_UP(size - ZS_MIN_ALLOC_SIZE,
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ZS_SIZE_CLASS_DELTA);
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return idx;
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}
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static enum fullness_group get_fullness_group(struct page *page)
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{
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int inuse, max_objects;
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enum fullness_group fg;
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BUG_ON(!is_first_page(page));
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inuse = page->inuse;
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max_objects = page->objects;
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if (inuse == 0)
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fg = ZS_EMPTY;
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else if (inuse == max_objects)
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fg = ZS_FULL;
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else if (inuse <= max_objects / fullness_threshold_frac)
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fg = ZS_ALMOST_EMPTY;
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else
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fg = ZS_ALMOST_FULL;
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return fg;
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}
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static void insert_zspage(struct page *page, struct size_class *class,
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enum fullness_group fullness)
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{
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struct page **head;
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BUG_ON(!is_first_page(page));
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if (fullness >= _ZS_NR_FULLNESS_GROUPS)
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return;
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head = &class->fullness_list[fullness];
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if (*head)
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list_add_tail(&page->lru, &(*head)->lru);
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*head = page;
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}
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static void remove_zspage(struct page *page, struct size_class *class,
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enum fullness_group fullness)
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{
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struct page **head;
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BUG_ON(!is_first_page(page));
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if (fullness >= _ZS_NR_FULLNESS_GROUPS)
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return;
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head = &class->fullness_list[fullness];
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BUG_ON(!*head);
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if (list_empty(&(*head)->lru))
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*head = NULL;
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else if (*head == page)
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*head = (struct page *)list_entry((*head)->lru.next,
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struct page, lru);
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list_del_init(&page->lru);
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}
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static enum fullness_group fix_fullness_group(struct zs_pool *pool,
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struct page *page)
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{
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int class_idx;
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struct size_class *class;
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enum fullness_group currfg, newfg;
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BUG_ON(!is_first_page(page));
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get_zspage_mapping(page, &class_idx, &currfg);
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newfg = get_fullness_group(page);
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if (newfg == currfg)
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goto out;
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class = &pool->size_class[class_idx];
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remove_zspage(page, class, currfg);
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insert_zspage(page, class, newfg);
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set_zspage_mapping(page, class_idx, newfg);
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out:
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return newfg;
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}
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/*
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* We have to decide on how many pages to link together
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* to form a zspage for each size class. This is important
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* to reduce wastage due to unusable space left at end of
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* each zspage which is given as:
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* wastage = Zp - Zp % size_class
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* where Zp = zspage size = k * PAGE_SIZE where k = 1, 2, ...
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*
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* For example, for size class of 3/8 * PAGE_SIZE, we should
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* link together 3 PAGE_SIZE sized pages to form a zspage
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* since then we can perfectly fit in 8 such objects.
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*/
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static int get_zspage_order(int class_size)
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{
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int i, max_usedpc = 0;
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/* zspage order which gives maximum used size per KB */
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int max_usedpc_order = 1;
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for (i = 1; i <= max_zspage_order; i++) {
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int zspage_size;
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int waste, usedpc;
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zspage_size = i * PAGE_SIZE;
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waste = zspage_size % class_size;
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usedpc = (zspage_size - waste) * 100 / zspage_size;
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if (usedpc > max_usedpc) {
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max_usedpc = usedpc;
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max_usedpc_order = i;
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}
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}
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return max_usedpc_order;
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}
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/*
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* A single 'zspage' is composed of many system pages which are
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* linked together using fields in struct page. This function finds
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* the first/head page, given any component page of a zspage.
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*/
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static struct page *get_first_page(struct page *page)
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{
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if (is_first_page(page))
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return page;
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else
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return page->first_page;
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}
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static struct page *get_next_page(struct page *page)
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{
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struct page *next;
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if (is_last_page(page))
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next = NULL;
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else if (is_first_page(page))
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next = (struct page *)page->private;
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else
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next = list_entry(page->lru.next, struct page, lru);
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return next;
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}
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/* Encode <page, obj_idx> as a single handle value */
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static void *obj_location_to_handle(struct page *page, unsigned long obj_idx)
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{
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unsigned long handle;
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if (!page) {
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BUG_ON(obj_idx);
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return NULL;
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}
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handle = page_to_pfn(page) << OBJ_INDEX_BITS;
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handle |= (obj_idx & OBJ_INDEX_MASK);
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return (void *)handle;
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}
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/* Decode <page, obj_idx> pair from the given object handle */
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static void obj_handle_to_location(void *handle, struct page **page,
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unsigned long *obj_idx)
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{
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unsigned long hval = (unsigned long)handle;
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*page = pfn_to_page(hval >> OBJ_INDEX_BITS);
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*obj_idx = hval & OBJ_INDEX_MASK;
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}
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static unsigned long obj_idx_to_offset(struct page *page,
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unsigned long obj_idx, int class_size)
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{
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unsigned long off = 0;
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if (!is_first_page(page))
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off = page->index;
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return off + obj_idx * class_size;
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}
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static void free_zspage(struct page *first_page)
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{
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struct page *nextp, *tmp;
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BUG_ON(!is_first_page(first_page));
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BUG_ON(first_page->inuse);
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nextp = (struct page *)page_private(first_page);
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clear_bit(PG_private, &first_page->flags);
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clear_bit(PG_private_2, &first_page->flags);
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set_page_private(first_page, 0);
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first_page->mapping = NULL;
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first_page->freelist = NULL;
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reset_page_mapcount(first_page);
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__free_page(first_page);
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/* zspage with only 1 system page */
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if (!nextp)
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return;
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list_for_each_entry_safe(nextp, tmp, &nextp->lru, lru) {
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list_del(&nextp->lru);
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clear_bit(PG_private_2, &nextp->flags);
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nextp->index = 0;
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__free_page(nextp);
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}
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}
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/* Initialize a newly allocated zspage */
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static void init_zspage(struct page *first_page, struct size_class *class)
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{
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unsigned long off = 0;
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struct page *page = first_page;
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BUG_ON(!is_first_page(first_page));
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while (page) {
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struct page *next_page;
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struct link_free *link;
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unsigned int i, objs_on_page;
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/*
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* page->index stores offset of first object starting
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* in the page. For the first page, this is always 0,
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* so we use first_page->index (aka ->freelist) to store
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* head of corresponding zspage's freelist.
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*/
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if (page != first_page)
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page->index = off;
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link = (struct link_free *)kmap_atomic(page) +
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off / sizeof(*link);
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objs_on_page = (PAGE_SIZE - off) / class->size;
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for (i = 1; i <= objs_on_page; i++) {
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off += class->size;
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if (off < PAGE_SIZE) {
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link->next = obj_location_to_handle(page, i);
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link += class->size / sizeof(*link);
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}
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}
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/*
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* We now come to the last (full or partial) object on this
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* page, which must point to the first object on the next
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* page (if present)
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*/
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next_page = get_next_page(page);
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link->next = obj_location_to_handle(next_page, 0);
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kunmap_atomic(link);
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page = next_page;
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off = (off + class->size) % PAGE_SIZE;
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}
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}
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/*
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* Allocate a zspage for the given size class
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*/
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static struct page *alloc_zspage(struct size_class *class, gfp_t flags)
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{
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int i, error;
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struct page *first_page = NULL;
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/*
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* Allocate individual pages and link them together as:
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* 1. first page->private = first sub-page
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* 2. all sub-pages are linked together using page->lru
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* 3. each sub-page is linked to the first page using page->first_page
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*
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* For each size class, First/Head pages are linked together using
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* page->lru. Also, we set PG_private to identify the first page
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* (i.e. no other sub-page has this flag set) and PG_private_2 to
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* identify the last page.
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*/
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error = -ENOMEM;
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for (i = 0; i < class->zspage_order; i++) {
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struct page *page, *prev_page;
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page = alloc_page(flags);
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if (!page)
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goto cleanup;
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INIT_LIST_HEAD(&page->lru);
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if (i == 0) { /* first page */
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set_bit(PG_private, &page->flags);
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set_page_private(page, 0);
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first_page = page;
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first_page->inuse = 0;
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}
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if (i == 1)
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first_page->private = (unsigned long)page;
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if (i >= 1)
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page->first_page = first_page;
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if (i >= 2)
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list_add(&page->lru, &prev_page->lru);
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if (i == class->zspage_order - 1) /* last page */
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set_bit(PG_private_2, &page->flags);
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prev_page = page;
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}
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init_zspage(first_page, class);
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first_page->freelist = obj_location_to_handle(first_page, 0);
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/* Maximum number of objects we can store in this zspage */
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first_page->objects = class->zspage_order * PAGE_SIZE / class->size;
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error = 0; /* Success */
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cleanup:
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if (unlikely(error) && first_page) {
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free_zspage(first_page);
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first_page = NULL;
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}
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return first_page;
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}
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static struct page *find_get_zspage(struct size_class *class)
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{
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int i;
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struct page *page;
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for (i = 0; i < _ZS_NR_FULLNESS_GROUPS; i++) {
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page = class->fullness_list[i];
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if (page)
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break;
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}
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return page;
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}
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/*
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* If this becomes a separate module, register zs_init() with
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* module_init(), zs_exit with module_exit(), and remove zs_initialized
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*/
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static int zs_initialized;
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static int zs_cpu_notifier(struct notifier_block *nb, unsigned long action,
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void *pcpu)
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{
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int cpu = (long)pcpu;
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struct mapping_area *area;
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switch (action) {
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case CPU_UP_PREPARE:
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area = &per_cpu(zs_map_area, cpu);
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if (area->vm)
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break;
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||
|
area->vm = alloc_vm_area(2 * PAGE_SIZE, area->vm_ptes);
|
||
|
if (!area->vm)
|
||
|
return notifier_from_errno(-ENOMEM);
|
||
|
break;
|
||
|
case CPU_DEAD:
|
||
|
case CPU_UP_CANCELED:
|
||
|
area = &per_cpu(zs_map_area, cpu);
|
||
|
if (area->vm)
|
||
|
free_vm_area(area->vm);
|
||
|
area->vm = NULL;
|
||
|
break;
|
||
|
}
|
||
|
|
||
|
return NOTIFY_OK;
|
||
|
}
|
||
|
|
||
|
static struct notifier_block zs_cpu_nb = {
|
||
|
.notifier_call = zs_cpu_notifier
|
||
|
};
|
||
|
|
||
|
static void zs_exit(void)
|
||
|
{
|
||
|
int cpu;
|
||
|
|
||
|
for_each_online_cpu(cpu)
|
||
|
zs_cpu_notifier(NULL, CPU_DEAD, (void *)(long)cpu);
|
||
|
unregister_cpu_notifier(&zs_cpu_nb);
|
||
|
}
|
||
|
|
||
|
static int zs_init(void)
|
||
|
{
|
||
|
int cpu, ret;
|
||
|
|
||
|
register_cpu_notifier(&zs_cpu_nb);
|
||
|
for_each_online_cpu(cpu) {
|
||
|
ret = zs_cpu_notifier(NULL, CPU_UP_PREPARE, (void *)(long)cpu);
|
||
|
if (notifier_to_errno(ret))
|
||
|
goto fail;
|
||
|
}
|
||
|
return 0;
|
||
|
fail:
|
||
|
zs_exit();
|
||
|
return notifier_to_errno(ret);
|
||
|
}
|
||
|
|
||
|
struct zs_pool *zs_create_pool(const char *name, gfp_t flags)
|
||
|
{
|
||
|
int i, error, ovhd_size;
|
||
|
struct zs_pool *pool;
|
||
|
|
||
|
if (!name)
|
||
|
return NULL;
|
||
|
|
||
|
ovhd_size = roundup(sizeof(*pool), PAGE_SIZE);
|
||
|
pool = kzalloc(ovhd_size, GFP_KERNEL);
|
||
|
if (!pool)
|
||
|
return NULL;
|
||
|
|
||
|
for (i = 0; i < ZS_SIZE_CLASSES; i++) {
|
||
|
int size;
|
||
|
struct size_class *class;
|
||
|
|
||
|
size = ZS_MIN_ALLOC_SIZE + i * ZS_SIZE_CLASS_DELTA;
|
||
|
if (size > ZS_MAX_ALLOC_SIZE)
|
||
|
size = ZS_MAX_ALLOC_SIZE;
|
||
|
|
||
|
class = &pool->size_class[i];
|
||
|
class->size = size;
|
||
|
class->index = i;
|
||
|
spin_lock_init(&class->lock);
|
||
|
class->zspage_order = get_zspage_order(size);
|
||
|
|
||
|
}
|
||
|
|
||
|
/*
|
||
|
* If this becomes a separate module, register zs_init with
|
||
|
* module_init, and remove this block
|
||
|
*/
|
||
|
if (!zs_initialized) {
|
||
|
error = zs_init();
|
||
|
if (error)
|
||
|
goto cleanup;
|
||
|
zs_initialized = 1;
|
||
|
}
|
||
|
|
||
|
pool->flags = flags;
|
||
|
pool->name = name;
|
||
|
|
||
|
error = 0; /* Success */
|
||
|
|
||
|
cleanup:
|
||
|
if (error) {
|
||
|
zs_destroy_pool(pool);
|
||
|
pool = NULL;
|
||
|
}
|
||
|
|
||
|
return pool;
|
||
|
}
|
||
|
EXPORT_SYMBOL_GPL(zs_create_pool);
|
||
|
|
||
|
void zs_destroy_pool(struct zs_pool *pool)
|
||
|
{
|
||
|
int i;
|
||
|
|
||
|
for (i = 0; i < ZS_SIZE_CLASSES; i++) {
|
||
|
int fg;
|
||
|
struct size_class *class = &pool->size_class[i];
|
||
|
|
||
|
for (fg = 0; fg < _ZS_NR_FULLNESS_GROUPS; fg++) {
|
||
|
if (class->fullness_list[fg]) {
|
||
|
pr_info("Freeing non-empty class with size "
|
||
|
"%db, fullness group %d\n",
|
||
|
class->size, fg);
|
||
|
}
|
||
|
}
|
||
|
}
|
||
|
kfree(pool);
|
||
|
}
|
||
|
EXPORT_SYMBOL_GPL(zs_destroy_pool);
|
||
|
|
||
|
/**
|
||
|
* zs_malloc - Allocate block of given size from pool.
|
||
|
* @pool: pool to allocate from
|
||
|
* @size: size of block to allocate
|
||
|
* @page: page no. that holds the object
|
||
|
* @offset: location of object within page
|
||
|
*
|
||
|
* On success, <page, offset> identifies block allocated
|
||
|
* and 0 is returned. On failure, <page, offset> is set to
|
||
|
* 0 and -ENOMEM is returned.
|
||
|
*
|
||
|
* Allocation requests with size > ZS_MAX_ALLOC_SIZE will fail.
|
||
|
*/
|
||
|
void *zs_malloc(struct zs_pool *pool, size_t size)
|
||
|
{
|
||
|
void *obj;
|
||
|
struct link_free *link;
|
||
|
int class_idx;
|
||
|
struct size_class *class;
|
||
|
|
||
|
struct page *first_page, *m_page;
|
||
|
unsigned long m_objidx, m_offset;
|
||
|
|
||
|
if (unlikely(!size || size > ZS_MAX_ALLOC_SIZE))
|
||
|
return NULL;
|
||
|
|
||
|
class_idx = get_size_class_index(size);
|
||
|
class = &pool->size_class[class_idx];
|
||
|
BUG_ON(class_idx != class->index);
|
||
|
|
||
|
spin_lock(&class->lock);
|
||
|
first_page = find_get_zspage(class);
|
||
|
|
||
|
if (!first_page) {
|
||
|
spin_unlock(&class->lock);
|
||
|
first_page = alloc_zspage(class, pool->flags);
|
||
|
if (unlikely(!first_page))
|
||
|
return NULL;
|
||
|
|
||
|
set_zspage_mapping(first_page, class->index, ZS_EMPTY);
|
||
|
spin_lock(&class->lock);
|
||
|
class->pages_allocated += class->zspage_order;
|
||
|
}
|
||
|
|
||
|
obj = first_page->freelist;
|
||
|
obj_handle_to_location(obj, &m_page, &m_objidx);
|
||
|
m_offset = obj_idx_to_offset(m_page, m_objidx, class->size);
|
||
|
|
||
|
link = (struct link_free *)kmap_atomic(m_page) +
|
||
|
m_offset / sizeof(*link);
|
||
|
first_page->freelist = link->next;
|
||
|
memset(link, POISON_INUSE, sizeof(*link));
|
||
|
kunmap_atomic(link);
|
||
|
|
||
|
first_page->inuse++;
|
||
|
/* Now move the zspage to another fullness group, if required */
|
||
|
fix_fullness_group(pool, first_page);
|
||
|
spin_unlock(&class->lock);
|
||
|
|
||
|
return obj;
|
||
|
}
|
||
|
EXPORT_SYMBOL_GPL(zs_malloc);
|
||
|
|
||
|
void zs_free(struct zs_pool *pool, void *obj)
|
||
|
{
|
||
|
struct link_free *link;
|
||
|
struct page *first_page, *f_page;
|
||
|
unsigned long f_objidx, f_offset;
|
||
|
|
||
|
int class_idx;
|
||
|
struct size_class *class;
|
||
|
enum fullness_group fullness;
|
||
|
|
||
|
if (unlikely(!obj))
|
||
|
return;
|
||
|
|
||
|
obj_handle_to_location(obj, &f_page, &f_objidx);
|
||
|
first_page = get_first_page(f_page);
|
||
|
|
||
|
get_zspage_mapping(first_page, &class_idx, &fullness);
|
||
|
class = &pool->size_class[class_idx];
|
||
|
f_offset = obj_idx_to_offset(f_page, f_objidx, class->size);
|
||
|
|
||
|
spin_lock(&class->lock);
|
||
|
|
||
|
/* Insert this object in containing zspage's freelist */
|
||
|
link = (struct link_free *)((unsigned char *)kmap_atomic(f_page)
|
||
|
+ f_offset);
|
||
|
link->next = first_page->freelist;
|
||
|
kunmap_atomic(link);
|
||
|
first_page->freelist = obj;
|
||
|
|
||
|
first_page->inuse--;
|
||
|
fullness = fix_fullness_group(pool, first_page);
|
||
|
|
||
|
if (fullness == ZS_EMPTY)
|
||
|
class->pages_allocated -= class->zspage_order;
|
||
|
|
||
|
spin_unlock(&class->lock);
|
||
|
|
||
|
if (fullness == ZS_EMPTY)
|
||
|
free_zspage(first_page);
|
||
|
}
|
||
|
EXPORT_SYMBOL_GPL(zs_free);
|
||
|
|
||
|
void *zs_map_object(struct zs_pool *pool, void *handle)
|
||
|
{
|
||
|
struct page *page;
|
||
|
unsigned long obj_idx, off;
|
||
|
|
||
|
unsigned int class_idx;
|
||
|
enum fullness_group fg;
|
||
|
struct size_class *class;
|
||
|
struct mapping_area *area;
|
||
|
|
||
|
BUG_ON(!handle);
|
||
|
|
||
|
obj_handle_to_location(handle, &page, &obj_idx);
|
||
|
get_zspage_mapping(get_first_page(page), &class_idx, &fg);
|
||
|
class = &pool->size_class[class_idx];
|
||
|
off = obj_idx_to_offset(page, obj_idx, class->size);
|
||
|
|
||
|
area = &get_cpu_var(zs_map_area);
|
||
|
if (off + class->size <= PAGE_SIZE) {
|
||
|
/* this object is contained entirely within a page */
|
||
|
area->vm_addr = kmap_atomic(page);
|
||
|
} else {
|
||
|
/* this object spans two pages */
|
||
|
struct page *nextp;
|
||
|
|
||
|
nextp = get_next_page(page);
|
||
|
BUG_ON(!nextp);
|
||
|
|
||
|
|
||
|
set_pte(area->vm_ptes[0], mk_pte(page, PAGE_KERNEL));
|
||
|
set_pte(area->vm_ptes[1], mk_pte(nextp, PAGE_KERNEL));
|
||
|
|
||
|
/* We pre-allocated VM area so mapping can never fail */
|
||
|
area->vm_addr = area->vm->addr;
|
||
|
}
|
||
|
|
||
|
return area->vm_addr + off;
|
||
|
}
|
||
|
EXPORT_SYMBOL_GPL(zs_map_object);
|
||
|
|
||
|
void zs_unmap_object(struct zs_pool *pool, void *handle)
|
||
|
{
|
||
|
struct page *page;
|
||
|
unsigned long obj_idx, off;
|
||
|
|
||
|
unsigned int class_idx;
|
||
|
enum fullness_group fg;
|
||
|
struct size_class *class;
|
||
|
struct mapping_area *area;
|
||
|
|
||
|
BUG_ON(!handle);
|
||
|
|
||
|
obj_handle_to_location(handle, &page, &obj_idx);
|
||
|
get_zspage_mapping(get_first_page(page), &class_idx, &fg);
|
||
|
class = &pool->size_class[class_idx];
|
||
|
off = obj_idx_to_offset(page, obj_idx, class->size);
|
||
|
|
||
|
area = &__get_cpu_var(zs_map_area);
|
||
|
if (off + class->size <= PAGE_SIZE) {
|
||
|
kunmap_atomic(area->vm_addr);
|
||
|
} else {
|
||
|
set_pte(area->vm_ptes[0], __pte(0));
|
||
|
set_pte(area->vm_ptes[1], __pte(0));
|
||
|
__flush_tlb_one((unsigned long)area->vm_addr);
|
||
|
__flush_tlb_one((unsigned long)area->vm_addr + PAGE_SIZE);
|
||
|
}
|
||
|
put_cpu_var(zs_map_area);
|
||
|
}
|
||
|
EXPORT_SYMBOL_GPL(zs_unmap_object);
|
||
|
|
||
|
u64 zs_get_total_size_bytes(struct zs_pool *pool)
|
||
|
{
|
||
|
int i;
|
||
|
u64 npages = 0;
|
||
|
|
||
|
for (i = 0; i < ZS_SIZE_CLASSES; i++)
|
||
|
npages += pool->size_class[i].pages_allocated;
|
||
|
|
||
|
return npages << PAGE_SHIFT;
|
||
|
}
|
||
|
EXPORT_SYMBOL_GPL(zs_get_total_size_bytes);
|