source: src/linux/universal/linux-4.9/fs/squashfs/symlink.c @ 31630

Last change on this file since 31630 was 31630, checked in by brainslayer, 5 months ago

new fs is compatible with standard squashfs, just smaller

File size: 3.7 KB
Line 
1/*
2 * Squashfs - a compressed read only filesystem for Linux
3 *
4 * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
5 * Phillip Lougher <phillip@squashfs.org.uk>
6 *
7 * This program is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public License
9 * as published by the Free Software Foundation; either version 2,
10 * or (at your option) any later version.
11 *
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15 * GNU General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with this program; if not, write to the Free Software
19 * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
20 *
21 * symlink.c
22 */
23
24/*
25 * This file implements code to handle symbolic links.
26 *
27 * The data contents of symbolic links are stored inside the symbolic
28 * link inode within the inode table.  This allows the normally small symbolic
29 * link to be compressed as part of the inode table, achieving much greater
30 * compression than if the symbolic link was compressed individually.
31 */
32
33#include <linux/fs.h>
34#include <linux/vfs.h>
35#include <linux/kernel.h>
36#include <linux/string.h>
37#include <linux/pagemap.h>
38#include <linux/xattr.h>
39
40#include "squashfs_fs.h"
41#include "squashfs_fs_sb.h"
42#include "squashfs_fs_i.h"
43#include "squashfs.h"
44#include "xattr.h"
45
46static int squashfs_symlink_readpage(struct file *file, struct page *page)
47{
48        struct inode *inode = page->mapping->host;
49        struct super_block *sb = inode->i_sb;
50        struct squashfs_sb_info *msblk = sb->s_fs_info;
51        int index = page->index << PAGE_SHIFT;
52        u64 block = squashfs_i(inode)->start;
53        int offset = squashfs_i(inode)->offset;
54        int length = min_t(int, i_size_read(inode) - index, PAGE_SIZE);
55        int bytes, copied;
56        void *pageaddr;
57        struct squashfs_cache_entry *entry;
58
59        TRACE("Entered squashfs_symlink_readpage, page index %ld, start block "
60                        "%llx, offset %x\n", page->index, block, offset);
61
62        /*
63         * Skip index bytes into symlink metadata.
64         */
65        if (index) {
66                bytes = squashfs_read_metadata(sb, NULL, &block, &offset,
67                                                                index);
68                if (bytes < 0) {
69                        ERROR("Unable to read symlink [%llx:%x]\n",
70                                squashfs_i(inode)->start,
71                                squashfs_i(inode)->offset);
72                        goto error_out;
73                }
74        }
75
76        /*
77         * Read length bytes from symlink metadata.  Squashfs_read_metadata
78         * is not used here because it can sleep and we want to use
79         * kmap_atomic to map the page.  Instead call the underlying
80         * squashfs_cache_get routine.  As length bytes may overlap metadata
81         * blocks, we may need to call squashfs_cache_get multiple times.
82         */
83        for (bytes = 0; bytes < length; offset = 0, bytes += copied) {
84                entry = squashfs_cache_get(sb, msblk->block_cache, block, 0);
85                if (entry->error) {
86                        ERROR("Unable to read symlink [%llx:%x]\n",
87                                squashfs_i(inode)->start,
88                                squashfs_i(inode)->offset);
89                        squashfs_cache_put(entry);
90                        goto error_out;
91                }
92
93                pageaddr = kmap_atomic(page);
94                copied = squashfs_copy_data(pageaddr + bytes, entry, offset,
95                                                                length - bytes);
96                if (copied == length - bytes)
97                        memset(pageaddr + length, 0, PAGE_SIZE - length);
98                else
99                        block = entry->next_index;
100                kunmap_atomic(pageaddr);
101                squashfs_cache_put(entry);
102        }
103
104        flush_dcache_page(page);
105        SetPageUptodate(page);
106        unlock_page(page);
107        return 0;
108
109error_out:
110        SetPageError(page);
111        unlock_page(page);
112        return 0;
113}
114
115
116const struct address_space_operations squashfs_symlink_aops = {
117        .readpage = squashfs_symlink_readpage
118};
119
120const struct inode_operations squashfs_symlink_inode_ops = {
121        .readlink = generic_readlink,
122        .get_link = page_get_link,
123        .listxattr = squashfs_listxattr
124};
125
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