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119 lines
3.6 KiB
C
119 lines
3.6 KiB
C
/*
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* Squashfs - a compressed read only filesystem for Linux
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*
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* Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
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* Phillip Lougher <phillip@lougher.demon.co.uk>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2,
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* or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*
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* symlink.c
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*/
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/*
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* This file implements code to handle symbolic links.
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*
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* The data contents of symbolic links are stored inside the symbolic
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* link inode within the inode table. This allows the normally small symbolic
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* link to be compressed as part of the inode table, achieving much greater
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* compression than if the symbolic link was compressed individually.
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*/
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#include <linux/fs.h>
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#include <linux/vfs.h>
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#include <linux/kernel.h>
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#include <linux/slab.h>
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#include <linux/string.h>
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#include <linux/pagemap.h>
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#include <linux/zlib.h>
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#include "squashfs_fs.h"
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#include "squashfs_fs_sb.h"
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#include "squashfs_fs_i.h"
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#include "squashfs.h"
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static int squashfs_symlink_readpage(struct file *file, struct page *page)
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{
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struct inode *inode = page->mapping->host;
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struct super_block *sb = inode->i_sb;
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struct squashfs_sb_info *msblk = sb->s_fs_info;
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int index = page->index << PAGE_CACHE_SHIFT;
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u64 block = squashfs_i(inode)->start;
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int offset = squashfs_i(inode)->offset;
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int length = min_t(int, i_size_read(inode) - index, PAGE_CACHE_SIZE);
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int bytes, copied;
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void *pageaddr;
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struct squashfs_cache_entry *entry;
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TRACE("Entered squashfs_symlink_readpage, page index %ld, start block "
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"%llx, offset %x\n", page->index, block, offset);
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/*
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* Skip index bytes into symlink metadata.
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*/
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if (index) {
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bytes = squashfs_read_metadata(sb, NULL, &block, &offset,
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index);
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if (bytes < 0) {
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ERROR("Unable to read symlink [%llx:%x]\n",
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squashfs_i(inode)->start,
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squashfs_i(inode)->offset);
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goto error_out;
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}
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}
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/*
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* Read length bytes from symlink metadata. Squashfs_read_metadata
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* is not used here because it can sleep and we want to use
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* kmap_atomic to map the page. Instead call the underlying
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* squashfs_cache_get routine. As length bytes may overlap metadata
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* blocks, we may need to call squashfs_cache_get multiple times.
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*/
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for (bytes = 0; bytes < length; offset = 0, bytes += copied) {
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entry = squashfs_cache_get(sb, msblk->block_cache, block, 0);
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if (entry->error) {
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ERROR("Unable to read symlink [%llx:%x]\n",
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squashfs_i(inode)->start,
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squashfs_i(inode)->offset);
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squashfs_cache_put(entry);
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goto error_out;
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}
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pageaddr = kmap_atomic(page, KM_USER0);
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copied = squashfs_copy_data(pageaddr + bytes, entry, offset,
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length - bytes);
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if (copied == length - bytes)
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memset(pageaddr + length, 0, PAGE_CACHE_SIZE - length);
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else
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block = entry->next_index;
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kunmap_atomic(pageaddr, KM_USER0);
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squashfs_cache_put(entry);
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}
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flush_dcache_page(page);
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SetPageUptodate(page);
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unlock_page(page);
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return 0;
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error_out:
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SetPageError(page);
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unlock_page(page);
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return 0;
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}
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const struct address_space_operations squashfs_symlink_aops = {
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.readpage = squashfs_symlink_readpage
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};
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