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 "squashfs_fs_sb.h"
11#include "decompressor.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->tmp_buffer = NULL;
56	actor->squashfs_first_page = cache_first_page;
57	actor->squashfs_next_page = cache_next_page;
58	actor->squashfs_finish_page = cache_finish_page;
59	return actor;
60}
61
62/* Implementation of page_actor for decompressing directly into page cache. */
63static void *handle_next_page(struct squashfs_page_actor *actor)
64{
65	int max_pages = (actor->length + PAGE_SIZE - 1) >> PAGE_SHIFT;
66
67	if (actor->returned_pages == max_pages)
68		return NULL;
69
70	if ((actor->next_page == actor->pages) ||
71			(actor->next_index != actor->page[actor->next_page]->index)) {
72		actor->next_index++;
73		actor->returned_pages++;
74		actor->last_page = NULL;
75		return actor->alloc_buffer ? actor->tmp_buffer : ERR_PTR(-ENOMEM);
76	}
77
78	actor->next_index++;
79	actor->returned_pages++;
80	actor->last_page = actor->page[actor->next_page];
81	return actor->pageaddr = kmap_local_page(actor->page[actor->next_page++]);
82}
83
84static void *direct_first_page(struct squashfs_page_actor *actor)
85{
86	return handle_next_page(actor);
87}
88
89static void *direct_next_page(struct squashfs_page_actor *actor)
90{
91	if (actor->pageaddr) {
92		kunmap_local(actor->pageaddr);
93		actor->pageaddr = NULL;
94	}
95
96	return handle_next_page(actor);
97}
98
99static void direct_finish_page(struct squashfs_page_actor *actor)
100{
101	if (actor->pageaddr)
102		kunmap_local(actor->pageaddr);
103}
104
105struct squashfs_page_actor *squashfs_page_actor_init_special(struct squashfs_sb_info *msblk,
106	struct page **page, int pages, int length)
107{
108	struct squashfs_page_actor *actor = kmalloc(sizeof(*actor), GFP_KERNEL);
109
110	if (actor == NULL)
111		return NULL;
112
113	if (msblk->decompressor->alloc_buffer) {
114		actor->tmp_buffer = kmalloc(PAGE_SIZE, GFP_KERNEL);
115
116		if (actor->tmp_buffer == NULL) {
117			kfree(actor);
118			return NULL;
119		}
120	} else
121		actor->tmp_buffer = NULL;
122
123	actor->length = length ? : pages * PAGE_SIZE;
124	actor->page = page;
125	actor->pages = pages;
126	actor->next_page = 0;
127	actor->returned_pages = 0;
128	actor->next_index = page[0]->index & ~((1 << (msblk->block_log - PAGE_SHIFT)) - 1);
129	actor->pageaddr = NULL;
130	actor->last_page = NULL;
131	actor->alloc_buffer = msblk->decompressor->alloc_buffer;
132	actor->squashfs_first_page = direct_first_page;
133	actor->squashfs_next_page = direct_next_page;
134	actor->squashfs_finish_page = direct_finish_page;
135	return actor;
136}
137