symlink.c 3.78 KB
Newer Older
1 2 3 4
/*
 * Squashfs - a compressed read only filesystem for Linux
 *
 * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
5
 * Phillip Lougher <phillip@squashfs.org.uk>
6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2,
 * or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * symlink.c
 */

/*
 * This file implements code to handle symbolic links.
 *
 * The data contents of symbolic links are stored inside the symbolic
 * link inode within the inode table.  This allows the normally small symbolic
 * link to be compressed as part of the inode table, achieving much greater
 * compression than if the symbolic link was compressed individually.
 */

#include <linux/fs.h>
#include <linux/vfs.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/pagemap.h>
38
#include <linux/xattr.h>
39 40 41 42 43

#include "squashfs_fs.h"
#include "squashfs_fs_sb.h"
#include "squashfs_fs_i.h"
#include "squashfs.h"
44
#include "xattr.h"
45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92

static int squashfs_symlink_readpage(struct file *file, struct page *page)
{
	struct inode *inode = page->mapping->host;
	struct super_block *sb = inode->i_sb;
	struct squashfs_sb_info *msblk = sb->s_fs_info;
	int index = page->index << PAGE_CACHE_SHIFT;
	u64 block = squashfs_i(inode)->start;
	int offset = squashfs_i(inode)->offset;
	int length = min_t(int, i_size_read(inode) - index, PAGE_CACHE_SIZE);
	int bytes, copied;
	void *pageaddr;
	struct squashfs_cache_entry *entry;

	TRACE("Entered squashfs_symlink_readpage, page index %ld, start block "
			"%llx, offset %x\n", page->index, block, offset);

	/*
	 * Skip index bytes into symlink metadata.
	 */
	if (index) {
		bytes = squashfs_read_metadata(sb, NULL, &block, &offset,
								index);
		if (bytes < 0) {
			ERROR("Unable to read symlink [%llx:%x]\n",
				squashfs_i(inode)->start,
				squashfs_i(inode)->offset);
			goto error_out;
		}
	}

	/*
	 * Read length bytes from symlink metadata.  Squashfs_read_metadata
	 * is not used here because it can sleep and we want to use
	 * kmap_atomic to map the page.  Instead call the underlying
	 * squashfs_cache_get routine.  As length bytes may overlap metadata
	 * blocks, we may need to call squashfs_cache_get multiple times.
	 */
	for (bytes = 0; bytes < length; offset = 0, bytes += copied) {
		entry = squashfs_cache_get(sb, msblk->block_cache, block, 0);
		if (entry->error) {
			ERROR("Unable to read symlink [%llx:%x]\n",
				squashfs_i(inode)->start,
				squashfs_i(inode)->offset);
			squashfs_cache_put(entry);
			goto error_out;
		}

93
		pageaddr = kmap_atomic(page);
94 95 96 97 98 99
		copied = squashfs_copy_data(pageaddr + bytes, entry, offset,
								length - bytes);
		if (copied == length - bytes)
			memset(pageaddr + length, 0, PAGE_CACHE_SIZE - length);
		else
			block = entry->next_index;
100
		kunmap_atomic(pageaddr);
101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118
		squashfs_cache_put(entry);
	}

	flush_dcache_page(page);
	SetPageUptodate(page);
	unlock_page(page);
	return 0;

error_out:
	SetPageError(page);
	unlock_page(page);
	return 0;
}


const struct address_space_operations squashfs_symlink_aops = {
	.readpage = squashfs_symlink_readpage
};
119 120 121 122 123 124 125 126 127

const struct inode_operations squashfs_symlink_inode_ops = {
	.readlink = generic_readlink,
	.follow_link = page_follow_link_light,
	.put_link = page_put_link,
	.getxattr = generic_getxattr,
	.listxattr = squashfs_listxattr
};