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/fs.h>
8 #include <linux/vfs.h>
9 #include <linux/kernel.h>
10 #include <linux/slab.h>
11 #include <linux/string.h>
12 #include <linux/pagemap.h>
13 #include <linux/mutex.h>
14
15 #include "squashfs_fs.h"
16 #include "squashfs_fs_sb.h"
17 #include "squashfs_fs_i.h"
18 #include "squashfs.h"
19 #include "page_actor.h"
20
21 /* Read separately compressed datablock directly into page cache */
22 int squashfs_readpage_block(struct page *target_page, u64 block, int bsize,
23 int expected)
24
25 {
26 struct inode *inode = target_page->mapping->host;
27 struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
28
29 loff_t file_end = (i_size_read(inode) - 1) >> PAGE_SHIFT;
30 int mask = (1 << (msblk->block_log - PAGE_SHIFT)) - 1;
31 loff_t start_index = target_page->index & ~mask;
32 loff_t end_index = start_index | mask;
33 int i, n, pages, bytes, res = -ENOMEM;
34 struct page **page;
35 struct squashfs_page_actor *actor;
36 void *pageaddr;
37
38 if (end_index > file_end)
39 end_index = file_end;
40
41 pages = end_index - start_index + 1;
42
43 page = kmalloc_array(pages, sizeof(void *), GFP_KERNEL);
44 if (page == NULL)
45 return res;
46
47 /* Try to grab all the pages covered by the Squashfs block */
48 for (i = 0, n = start_index; n <= end_index; n++) {
49 page[i] = (n == target_page->index) ? target_page :
50 grab_cache_page_nowait(target_page->mapping, n);
51
52 if (page[i] == NULL)
53 continue;
54
55 if (PageUptodate(page[i])) {
56 unlock_page(page[i]);
57 put_page(page[i]);
58 continue;
59 }
60
61 i++;
62 }
63
64 pages = i;
65
66 /*
67 * Create a "page actor" which will kmap and kunmap the
68 * page cache pages appropriately within the decompressor
69 */
70 actor = squashfs_page_actor_init_special(msblk, page, pages, expected);
71 if (actor == NULL)
72 goto out;
73
74 /* Decompress directly into the page cache buffers */
75 res = squashfs_read_data(inode->i_sb, block, bsize, NULL, actor);
76
77 squashfs_page_actor_free(actor);
78
79 if (res < 0)
80 goto mark_errored;
81
82 if (res != expected) {
83 res = -EIO;
84 goto mark_errored;
85 }
86
87 /* Last page (if present) may have trailing bytes not filled */
88 bytes = res % PAGE_SIZE;
89 if (page[pages - 1]->index == end_index && bytes) {
90 pageaddr = kmap_local_page(page[pages - 1]);
91 memset(pageaddr + bytes, 0, PAGE_SIZE - bytes);
92 kunmap_local(pageaddr);
93 }
94
95 /* Mark pages as uptodate, unlock and release */
96 for (i = 0; i < pages; i++) {
97 flush_dcache_page(page[i]);
98 SetPageUptodate(page[i]);
99 unlock_page(page[i]);
100 if (page[i] != target_page)
101 put_page(page[i]);
102 }
103
104 kfree(page);
105
106 return 0;
107
108 mark_errored:
109 /* Decompression failed. Target_page is
110 * dealt with by the caller
111 */
112 for (i = 0; i < pages; i++) {
113 if (page[i] == NULL || page[i] == target_page)
114 continue;
115 flush_dcache_page(page[i]);
116 unlock_page(page[i]);
117 put_page(page[i]);
118 }
119
120 out:
121 kfree(page);
122 return res;
123 }
124
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