1// SPDX-License-Identifier: GPL-2.0-only
 2/*
 3 * Copyright (c) 2013
 4 * Phillip Lougher <phillip@squashfs.org.uk>
 5 */
 6
 7#include <linux/kernel.h>
 8#include <linux/slab.h>
 9#include <linux/pagemap.h>
10#include "page_actor.h"
11
12/*
13 * This file contains implementations of page_actor for decompressing into
14 * an intermediate buffer, and for decompressing directly into the
15 * page cache.
16 *
17 * Calling code should avoid sleeping between calls to squashfs_first_page()
18 * and squashfs_finish_page().
19 */
20
21/* Implementation of page_actor for decompressing into intermediate buffer */
22static void *cache_first_page(struct squashfs_page_actor *actor)
23{
24	actor->next_page = 1;
25	return actor->buffer[0];
26}
27
28static void *cache_next_page(struct squashfs_page_actor *actor)
29{
30	if (actor->next_page == actor->pages)
31		return NULL;
32
33	return actor->buffer[actor->next_page++];
34}
35
36static void cache_finish_page(struct squashfs_page_actor *actor)
37{
38	/* empty */
39}
40
41struct squashfs_page_actor *squashfs_page_actor_init(void **buffer,
42	int pages, int length)
43{
44	struct squashfs_page_actor *actor = kmalloc(sizeof(*actor), GFP_KERNEL);
45
46	if (actor == NULL)
47		return NULL;
48
49	actor->length = length ? : pages * PAGE_SIZE;
50	actor->buffer = buffer;
51	actor->pages = pages;
52	actor->next_page = 0;
53	actor->squashfs_first_page = cache_first_page;
54	actor->squashfs_next_page = cache_next_page;
55	actor->squashfs_finish_page = cache_finish_page;
56	return actor;
57}
58
59/* Implementation of page_actor for decompressing directly into page cache. */
60static void *direct_first_page(struct squashfs_page_actor *actor)
61{
62	actor->next_page = 1;
63	return actor->pageaddr = kmap_atomic(actor->page[0]);
64}
65
66static void *direct_next_page(struct squashfs_page_actor *actor)
67{
68	if (actor->pageaddr)
69		kunmap_atomic(actor->pageaddr);
70
71	return actor->pageaddr = actor->next_page == actor->pages ? NULL :
72		kmap_atomic(actor->page[actor->next_page++]);
73}
74
75static void direct_finish_page(struct squashfs_page_actor *actor)
76{
77	if (actor->pageaddr)
78		kunmap_atomic(actor->pageaddr);
79}
80
81struct squashfs_page_actor *squashfs_page_actor_init_special(struct page **page,
82	int pages, int length)
83{
84	struct squashfs_page_actor *actor = kmalloc(sizeof(*actor), GFP_KERNEL);
85
86	if (actor == NULL)
87		return NULL;
88
89	actor->length = length ? : pages * PAGE_SIZE;
90	actor->page = page;
91	actor->pages = pages;
92	actor->next_page = 0;
93	actor->pageaddr = NULL;
94	actor->squashfs_first_page = direct_first_page;
95	actor->squashfs_next_page = direct_next_page;
96	actor->squashfs_finish_page = direct_finish_page;
97	return actor;
98}