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 */
22int squashfs_readpage_block(struct folio *folio, u64 block, int bsize,
23 int expected)
24{
25 struct page *target_page = &folio->page;
26 struct inode *inode = folio->mapping->host;
27 struct squashfs_sb_info *msblk = inode->i_sb->s_fs_info;
28 loff_t file_end = (i_size_read(inode) - 1) >> PAGE_SHIFT;
29 int mask = (1 << (msblk->block_log - PAGE_SHIFT)) - 1;
30 loff_t start_index = folio->index & ~mask;
31 loff_t end_index = start_index | mask;
32 loff_t index;
33 int i, pages, bytes, res = -ENOMEM;
34 struct page **page, *last_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, index = start_index; index <= end_index; index++) {
49 page[i] = (index == folio->index) ? target_page :
50 grab_cache_page_nowait(mapping: folio->mapping, index);
51
52 if (page[i] == NULL)
53 continue;
54
55 if (PageUptodate(page: page[i])) {
56 unlock_page(page: page[i]);
57 put_page(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, length: expected,
71 start_index: start_index << PAGE_SHIFT);
72 if (actor == NULL)
73 goto out;
74
75 /* Decompress directly into the page cache buffers */
76 res = squashfs_read_data(inode->i_sb, block, bsize, NULL, actor);
77
78 last_page = squashfs_page_actor_free(actor);
79
80 if (res < 0)
81 goto mark_errored;
82
83 if (res != expected || IS_ERR(ptr: last_page)) {
84 res = -EIO;
85 goto mark_errored;
86 }
87
88 /* Last page (if present) may have trailing bytes not filled */
89 bytes = res % PAGE_SIZE;
90 if (end_index == file_end && last_page && bytes) {
91 pageaddr = kmap_local_page(page: last_page);
92 memset(pageaddr + bytes, 0, PAGE_SIZE - bytes);
93 kunmap_local(pageaddr);
94 }
95
96 /* Mark pages as uptodate, unlock and release */
97 for (i = 0; i < pages; i++) {
98 flush_dcache_page(page: page[i]);
99 SetPageUptodate(page[i]);
100 unlock_page(page: page[i]);
101 if (page[i] != target_page)
102 put_page(page: page[i]);
103 }
104
105 kfree(objp: page);
106
107 return 0;
108
109mark_errored:
110 /* Decompression failed. Target_page is
111 * dealt with by the caller
112 */
113 for (i = 0; i < pages; i++) {
114 if (page[i] == NULL || page[i] == target_page)
115 continue;
116 flush_dcache_page(page: page[i]);
117 unlock_page(page: page[i]);
118 put_page(page: page[i]);
119 }
120
121out:
122 kfree(objp: page);
123 return res;
124}
125

source code of linux/fs/squashfs/file_direct.c