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 static int squashfs_read_cache(struct page *target_page, u64 block, int bsize,
22 int pages, struct page **page, int bytes);
23
24 /* Read separately compressed datablock directly into page cache */
squashfs_readpage_block(struct page * target_page,u64 block,int bsize,int expected)25 int squashfs_readpage_block(struct page *target_page, u64 block, int bsize,
26 int expected)
27
28 {
29 struct inode *inode = target_page->mapping->host;
30 struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
31
32 int file_end = (i_size_read(inode) - 1) >> PAGE_SHIFT;
33 int mask = (1 << (msblk->block_log - PAGE_SHIFT)) - 1;
34 int start_index = target_page->index & ~mask;
35 int end_index = start_index | mask;
36 int i, n, pages, missing_pages, bytes, res = -ENOMEM;
37 struct page **page;
38 struct squashfs_page_actor *actor;
39 void *pageaddr;
40
41 if (end_index > file_end)
42 end_index = file_end;
43
44 pages = end_index - start_index + 1;
45
46 page = kmalloc_array(pages, sizeof(void *), GFP_KERNEL);
47 if (page == NULL)
48 return res;
49
50 /*
51 * Create a "page actor" which will kmap and kunmap the
52 * page cache pages appropriately within the decompressor
53 */
54 actor = squashfs_page_actor_init_special(page, pages, 0);
55 if (actor == NULL)
56 goto out;
57
58 /* Try to grab all the pages covered by the Squashfs block */
59 for (missing_pages = 0, i = 0, n = start_index; i < pages; i++, n++) {
60 page[i] = (n == target_page->index) ? target_page :
61 grab_cache_page_nowait(target_page->mapping, n);
62
63 if (page[i] == NULL) {
64 missing_pages++;
65 continue;
66 }
67
68 if (PageUptodate(page[i])) {
69 unlock_page(page[i]);
70 put_page(page[i]);
71 page[i] = NULL;
72 missing_pages++;
73 }
74 }
75
76 if (missing_pages) {
77 /*
78 * Couldn't get one or more pages, this page has either
79 * been VM reclaimed, but others are still in the page cache
80 * and uptodate, or we're racing with another thread in
81 * squashfs_readpage also trying to grab them. Fall back to
82 * using an intermediate buffer.
83 */
84 res = squashfs_read_cache(target_page, block, bsize, pages,
85 page, expected);
86 if (res < 0)
87 goto mark_errored;
88
89 goto out;
90 }
91
92 /* Decompress directly into the page cache buffers */
93 res = squashfs_read_data(inode->i_sb, block, bsize, NULL, actor);
94 if (res < 0)
95 goto mark_errored;
96
97 if (res != expected) {
98 res = -EIO;
99 goto mark_errored;
100 }
101
102 /* Last page may have trailing bytes not filled */
103 bytes = res % PAGE_SIZE;
104 if (bytes) {
105 pageaddr = kmap_atomic(page[pages - 1]);
106 memset(pageaddr + bytes, 0, PAGE_SIZE - bytes);
107 kunmap_atomic(pageaddr);
108 }
109
110 /* Mark pages as uptodate, unlock and release */
111 for (i = 0; i < pages; i++) {
112 flush_dcache_page(page[i]);
113 SetPageUptodate(page[i]);
114 unlock_page(page[i]);
115 if (page[i] != target_page)
116 put_page(page[i]);
117 }
118
119 kfree(actor);
120 kfree(page);
121
122 return 0;
123
124 mark_errored:
125 /* Decompression failed, mark pages as errored. Target_page is
126 * dealt with by the caller
127 */
128 for (i = 0; i < pages; i++) {
129 if (page[i] == NULL || page[i] == target_page)
130 continue;
131 flush_dcache_page(page[i]);
132 SetPageError(page[i]);
133 unlock_page(page[i]);
134 put_page(page[i]);
135 }
136
137 out:
138 kfree(actor);
139 kfree(page);
140 return res;
141 }
142
143
squashfs_read_cache(struct page * target_page,u64 block,int bsize,int pages,struct page ** page,int bytes)144 static int squashfs_read_cache(struct page *target_page, u64 block, int bsize,
145 int pages, struct page **page, int bytes)
146 {
147 struct inode *i = target_page->mapping->host;
148 struct squashfs_cache_entry *buffer = squashfs_get_datablock(i->i_sb,
149 block, bsize);
150 int res = buffer->error, n, offset = 0;
151
152 if (res) {
153 ERROR("Unable to read page, block %llx, size %x\n", block,
154 bsize);
155 goto out;
156 }
157
158 for (n = 0; n < pages && bytes > 0; n++,
159 bytes -= PAGE_SIZE, offset += PAGE_SIZE) {
160 int avail = min_t(int, bytes, PAGE_SIZE);
161
162 if (page[n] == NULL)
163 continue;
164
165 squashfs_fill_page(page[n], buffer, offset, avail);
166 unlock_page(page[n]);
167 if (page[n] != target_page)
168 put_page(page[n]);
169 }
170
171 out:
172 squashfs_cache_put(buffer);
173 return res;
174 }
175
