source: src/linux/universal/linux-4.9/fs/squashfs/page_actor.c @ 31630

Last change on this file since 31630 was 31630, checked in by brainslayer, 2 weeks ago

new fs is compatible with standard squashfs, just smaller

File size: 2.6 KB
Line 
1/*
2 * Copyright (c) 2013
3 * Phillip Lougher <phillip@squashfs.org.uk>
4 *
5 * This work is licensed under the terms of the GNU GPL, version 2. See
6 * the COPYING file in the top-level directory.
7 */
8
9#include <linux/kernel.h>
10#include <linux/slab.h>
11#include <linux/pagemap.h>
12#include "page_actor.h"
13
14/*
15 * This file contains implementations of page_actor for decompressing into
16 * an intermediate buffer, and for decompressing directly into the
17 * page cache.
18 *
19 * Calling code should avoid sleeping between calls to squashfs_first_page()
20 * and squashfs_finish_page().
21 */
22
23/* Implementation of page_actor for decompressing into intermediate buffer */
24static void *cache_first_page(struct squashfs_page_actor *actor)
25{
26        actor->next_page = 1;
27        return actor->buffer[0];
28}
29
30static void *cache_next_page(struct squashfs_page_actor *actor)
31{
32        if (actor->next_page == actor->pages)
33                return NULL;
34
35        return actor->buffer[actor->next_page++];
36}
37
38static void cache_finish_page(struct squashfs_page_actor *actor)
39{
40        /* empty */
41}
42
43struct squashfs_page_actor *squashfs_page_actor_init(void **buffer,
44        int pages, int length)
45{
46        struct squashfs_page_actor *actor = kmalloc(sizeof(*actor), GFP_KERNEL);
47
48        if (actor == NULL)
49                return NULL;
50
51        actor->length = length ? : pages * PAGE_SIZE;
52        actor->buffer = buffer;
53        actor->pages = pages;
54        actor->next_page = 0;
55        actor->squashfs_first_page = cache_first_page;
56        actor->squashfs_next_page = cache_next_page;
57        actor->squashfs_finish_page = cache_finish_page;
58        return actor;
59}
60
61/* Implementation of page_actor for decompressing directly into page cache. */
62static void *direct_first_page(struct squashfs_page_actor *actor)
63{
64        actor->next_page = 1;
65        return actor->pageaddr = kmap_atomic(actor->page[0]);
66}
67
68static void *direct_next_page(struct squashfs_page_actor *actor)
69{
70        if (actor->pageaddr)
71                kunmap_atomic(actor->pageaddr);
72
73        return actor->pageaddr = actor->next_page == actor->pages ? NULL :
74                kmap_atomic(actor->page[actor->next_page++]);
75}
76
77static void direct_finish_page(struct squashfs_page_actor *actor)
78{
79        if (actor->pageaddr)
80                kunmap_atomic(actor->pageaddr);
81}
82
83struct squashfs_page_actor *squashfs_page_actor_init_special(struct page **page,
84        int pages, int length)
85{
86        struct squashfs_page_actor *actor = kmalloc(sizeof(*actor), GFP_KERNEL);
87
88        if (actor == NULL)
89                return NULL;
90
91        actor->length = length ? : pages * PAGE_SIZE;
92        actor->page = page;
93        actor->pages = pages;
94        actor->next_page = 0;
95        actor->pageaddr = NULL;
96        actor->squashfs_first_page = direct_first_page;
97        actor->squashfs_next_page = direct_next_page;
98        actor->squashfs_finish_page = direct_finish_page;
99        return actor;
100}
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