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. */
page_next_index(struct squashfs_page_actor * actor)63 static loff_t page_next_index(struct squashfs_page_actor *actor)
64 {
65 return page_folio(actor->page[actor->next_page])->index;
66 }
67
handle_next_page(struct squashfs_page_actor * actor)68 static void *handle_next_page(struct squashfs_page_actor *actor)
69 {
70 int max_pages = (actor->length + PAGE_SIZE - 1) >> PAGE_SHIFT;
71
72 if (actor->returned_pages == max_pages)
73 return NULL;
74
75 if ((actor->next_page == actor->pages) ||
76 (actor->next_index != page_next_index(actor))) {
77 actor->next_index++;
78 actor->returned_pages++;
79 actor->last_page = NULL;
80 return actor->alloc_buffer ? actor->tmp_buffer : ERR_PTR(-ENOMEM);
81 }
82
83 actor->next_index++;
84 actor->returned_pages++;
85 actor->last_page = actor->page[actor->next_page];
86 return actor->pageaddr = kmap_local_page(actor->page[actor->next_page++]);
87 }
88
direct_first_page(struct squashfs_page_actor * actor)89 static void *direct_first_page(struct squashfs_page_actor *actor)
90 {
91 return handle_next_page(actor);
92 }
93
direct_next_page(struct squashfs_page_actor * actor)94 static void *direct_next_page(struct squashfs_page_actor *actor)
95 {
96 if (actor->pageaddr) {
97 kunmap_local(actor->pageaddr);
98 actor->pageaddr = NULL;
99 }
100
101 return handle_next_page(actor);
102 }
103
direct_finish_page(struct squashfs_page_actor * actor)104 static void direct_finish_page(struct squashfs_page_actor *actor)
105 {
106 if (actor->pageaddr)
107 kunmap_local(actor->pageaddr);
108 }
109
squashfs_page_actor_init_special(struct squashfs_sb_info * msblk,struct page ** page,int pages,int length,loff_t start_index)110 struct squashfs_page_actor *squashfs_page_actor_init_special(struct squashfs_sb_info *msblk,
111 struct page **page, int pages, int length, loff_t start_index)
112 {
113 struct squashfs_page_actor *actor = kmalloc(sizeof(*actor), GFP_KERNEL);
114
115 if (actor == NULL)
116 return NULL;
117
118 if (msblk->decompressor->alloc_buffer) {
119 actor->tmp_buffer = kmalloc(PAGE_SIZE, GFP_KERNEL);
120
121 if (actor->tmp_buffer == NULL) {
122 kfree(actor);
123 return NULL;
124 }
125 } else
126 actor->tmp_buffer = NULL;
127
128 actor->length = length ? : pages * PAGE_SIZE;
129 actor->page = page;
130 actor->pages = pages;
131 actor->next_page = 0;
132 actor->returned_pages = 0;
133 actor->next_index = start_index >> PAGE_SHIFT;
134 actor->pageaddr = NULL;
135 actor->last_page = NULL;
136 actor->alloc_buffer = msblk->decompressor->alloc_buffer;
137 actor->squashfs_first_page = direct_first_page;
138 actor->squashfs_next_page = direct_next_page;
139 actor->squashfs_finish_page = direct_finish_page;
140 return actor;
141 }
142