[linux-2.6-block.git] / fs / squashfs / symlink.c

/*
 * Squashfs - a compressed read only filesystem for Linux
 *
 * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
 * Phillip Lougher <phillip@lougher.demon.co.uk>
 *
 * 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/slab.h>
#include <linux/string.h>
#include <linux/pagemap.h>

#include "squashfs_fs.h"
#include "squashfs_fs_sb.h"
#include "squashfs_fs_i.h"
#include "squashfs.h"

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;
		}

		pageaddr = kmap_atomic(page, KM_USER0);
		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;
		kunmap_atomic(pageaddr, KM_USER0);
		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
};
Commit	Line	Data
1dc4bba3 PL	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@lougher.demon.co.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/slab.h>
	37	#include <linux/string.h>
	38	#include <linux/pagemap.h>
1dc4bba3 PL	39
	40	#include "squashfs_fs.h"
	41	#include "squashfs_fs_sb.h"
	42	#include "squashfs_fs_i.h"
	43	#include "squashfs.h"
	44
	45	static int squashfs_symlink_readpage(struct file file, struct page page)
	46	{
	47	struct inode *inode = page->mapping->host;
	48	struct super_block *sb = inode->i_sb;
	49	struct squashfs_sb_info *msblk = sb->s_fs_info;
	50	int index = page->index << PAGE_CACHE_SHIFT;
	51	u64 block = squashfs_i(inode)->start;
	52	int offset = squashfs_i(inode)->offset;
	53	int length = min_t(int, i_size_read(inode) - index, PAGE_CACHE_SIZE);
	54	int bytes, copied;
	55	void *pageaddr;
	56	struct squashfs_cache_entry *entry;
	57
	58	TRACE("Entered squashfs_symlink_readpage, page index %ld, start block "
	59	"%llx, offset %x\n", page->index, block, offset);
	60
	61	/*
	62	* Skip index bytes into symlink metadata.
	63	*/
	64	if (index) {
	65	bytes = squashfs_read_metadata(sb, NULL, &block, &offset,
	66	index);
	67	if (bytes < 0) {
	68	ERROR("Unable to read symlink [%llx:%x]\n",
	69	squashfs_i(inode)->start,
	70	squashfs_i(inode)->offset);
	71	goto error_out;
	72	}
	73	}
	74
	75	/*
	76	* Read length bytes from symlink metadata. Squashfs_read_metadata
	77	* is not used here because it can sleep and we want to use
	78	* kmap_atomic to map the page. Instead call the underlying
	79	* squashfs_cache_get routine. As length bytes may overlap metadata
	80	* blocks, we may need to call squashfs_cache_get multiple times.
	81	*/
	82	for (bytes = 0; bytes < length; offset = 0, bytes += copied) {
	83	entry = squashfs_cache_get(sb, msblk->block_cache, block, 0);
	84	if (entry->error) {
	85	ERROR("Unable to read symlink [%llx:%x]\n",
	86	squashfs_i(inode)->start,
	87	squashfs_i(inode)->offset);
	88	squashfs_cache_put(entry);
	89	goto error_out;
	90	}
	91
	92	pageaddr = kmap_atomic(page, KM_USER0);
	93	copied = squashfs_copy_data(pageaddr + bytes, entry, offset,
	94	length - bytes);
	95	if (copied == length - bytes)
	96	memset(pageaddr + length, 0, PAGE_CACHE_SIZE - length);
	97	else
	98	block = entry->next_index;
	99	kunmap_atomic(pageaddr, KM_USER0);
	100	squashfs_cache_put(entry);
	101	}
	102
103	flush_dcache_page(page);
104	SetPageUptodate(page);
105	unlock_page(page);
106	return 0;
107
108	error_out:
109	SetPageError(page);
110	unlock_page(page);
111	return 0;
112	}
113
114
115	const struct address_space_operations squashfs_symlink_aops = {
116	.readpage = squashfs_symlink_readpage
117	};