GNU Linux-libre 4.19.211-gnu1
[releases.git] / fs / squashfs / page_actor.c
1 /*
2  * Copyright (c) 2013
3  * Phillip Lougher <phillip@squashfs.org.uk>
4  *
5  * This work is licensed under the terms of the GNU GPL, version 2. See
6  * the COPYING file in the top-level directory.
7  */
8
9 #include <linux/kernel.h>
10 #include <linux/slab.h>
11 #include <linux/pagemap.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->squashfs_first_page = cache_first_page;
56         actor->squashfs_next_page = cache_next_page;
57         actor->squashfs_finish_page = cache_finish_page;
58         return actor;
59 }
60
61 /* Implementation of page_actor for decompressing directly into page cache. */
62 static void *direct_first_page(struct squashfs_page_actor *actor)
63 {
64         actor->next_page = 1;
65         return actor->pageaddr = kmap_atomic(actor->page[0]);
66 }
67
68 static void *direct_next_page(struct squashfs_page_actor *actor)
69 {
70         if (actor->pageaddr)
71                 kunmap_atomic(actor->pageaddr);
72
73         return actor->pageaddr = actor->next_page == actor->pages ? NULL :
74                 kmap_atomic(actor->page[actor->next_page++]);
75 }
76
77 static void direct_finish_page(struct squashfs_page_actor *actor)
78 {
79         if (actor->pageaddr)
80                 kunmap_atomic(actor->pageaddr);
81 }
82
83 struct squashfs_page_actor *squashfs_page_actor_init_special(struct page **page,
84         int pages, int length)
85 {
86         struct squashfs_page_actor *actor = kmalloc(sizeof(*actor), GFP_KERNEL);
87
88         if (actor == NULL)
89                 return NULL;
90
91         actor->length = length ? : pages * PAGE_SIZE;
92         actor->page = page;
93         actor->pages = pages;
94         actor->next_page = 0;
95         actor->pageaddr = NULL;
96         actor->squashfs_first_page = direct_first_page;
97         actor->squashfs_next_page = direct_next_page;
98         actor->squashfs_finish_page = direct_finish_page;
99         return actor;
100 }