xref: /openbmc/linux/fs/squashfs/page_actor.c (revision c6fbb759)
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 */
24 static void *cache_first_page(struct squashfs_page_actor *actor)
25 {
26 	actor->next_page = 1;
27 	return actor->buffer[0];
28 }
29 
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 
38 static void cache_finish_page(struct squashfs_page_actor *actor)
39 {
40 	/* empty */
41 }
42 
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. */
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 		return actor->alloc_buffer ? actor->tmp_buffer : ERR_PTR(-ENOMEM);
75 	}
76 
77 	actor->next_index++;
78 	actor->returned_pages++;
79 	return actor->pageaddr = kmap_local_page(actor->page[actor->next_page++]);
80 }
81 
82 static void *direct_first_page(struct squashfs_page_actor *actor)
83 {
84 	return handle_next_page(actor);
85 }
86 
87 static void *direct_next_page(struct squashfs_page_actor *actor)
88 {
89 	if (actor->pageaddr) {
90 		kunmap_local(actor->pageaddr);
91 		actor->pageaddr = NULL;
92 	}
93 
94 	return handle_next_page(actor);
95 }
96 
97 static void direct_finish_page(struct squashfs_page_actor *actor)
98 {
99 	if (actor->pageaddr)
100 		kunmap_local(actor->pageaddr);
101 }
102 
103 struct squashfs_page_actor *squashfs_page_actor_init_special(struct squashfs_sb_info *msblk,
104 	struct page **page, int pages, int length)
105 {
106 	struct squashfs_page_actor *actor = kmalloc(sizeof(*actor), GFP_KERNEL);
107 
108 	if (actor == NULL)
109 		return NULL;
110 
111 	if (msblk->decompressor->alloc_buffer) {
112 		actor->tmp_buffer = kmalloc(PAGE_SIZE, GFP_KERNEL);
113 
114 		if (actor->tmp_buffer == NULL) {
115 			kfree(actor);
116 			return NULL;
117 		}
118 	} else
119 		actor->tmp_buffer = NULL;
120 
121 	actor->length = length ? : pages * PAGE_SIZE;
122 	actor->page = page;
123 	actor->pages = pages;
124 	actor->next_page = 0;
125 	actor->returned_pages = 0;
126 	actor->next_index = page[0]->index & ~((1 << (msblk->block_log - PAGE_SHIFT)) - 1);
127 	actor->pageaddr = NULL;
128 	actor->alloc_buffer = msblk->decompressor->alloc_buffer;
129 	actor->squashfs_first_page = direct_first_page;
130 	actor->squashfs_next_page = direct_next_page;
131 	actor->squashfs_finish_page = direct_finish_page;
132 	return actor;
133 }
134