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 */
cache_first_page(struct squashfs_page_actor * actor)24 static void *cache_first_page(struct squashfs_page_actor *actor)
25 {
26 actor->next_page = 1;
27 return actor->buffer[0];
28 }
29
cache_next_page(struct squashfs_page_actor * actor)30 static 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
cache_finish_page(struct squashfs_page_actor * actor)38 static void cache_finish_page(struct squashfs_page_actor *actor)
39 {
40 /* empty */
41 }
42
squashfs_page_actor_init(void ** buffer,int pages,int length)43 struct 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. */
handle_next_page(struct squashfs_page_actor * actor)63 static 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
direct_first_page(struct squashfs_page_actor * actor)84 static void *direct_first_page(struct squashfs_page_actor *actor)
85 {
86 return handle_next_page(actor);
87 }
88
direct_next_page(struct squashfs_page_actor * actor)89 static 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
direct_finish_page(struct squashfs_page_actor * actor)99 static void direct_finish_page(struct squashfs_page_actor *actor)
100 {
101 if (actor->pageaddr)
102 kunmap_local(actor->pageaddr);
103 }
104
squashfs_page_actor_init_special(struct squashfs_sb_info * msblk,struct page ** page,int pages,int length)105 struct 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