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 */
cache_first_page(struct squashfs_page_actor * actor)22 static void *cache_first_page(struct squashfs_page_actor *actor)
23 {
24 	actor->next_page = 1;
25 	return actor->buffer[0];
26 }
27 
cache_next_page(struct squashfs_page_actor * actor)28 static 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 
cache_finish_page(struct squashfs_page_actor * actor)36 static void cache_finish_page(struct squashfs_page_actor *actor)
37 {
38 	/* empty */
39 }
40 
squashfs_page_actor_init(void ** buffer,int pages,int length)41 struct 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. */
direct_first_page(struct squashfs_page_actor * actor)60 static 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 
direct_next_page(struct squashfs_page_actor * actor)66 static 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 
direct_finish_page(struct squashfs_page_actor * actor)75 static void direct_finish_page(struct squashfs_page_actor *actor)
76 {
77 	if (actor->pageaddr)
78 		kunmap_atomic(actor->pageaddr);
79 }
80 
squashfs_page_actor_init_special(struct page ** page,int pages,int length)81 struct 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 }
99