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

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Squashfs - a compressed read only filesystem for Linux
 *
 * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
 * Phillip Lougher <phillip@squashfs.org.uk>
 *
 * 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>
#include <linux/xattr.h>

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

static int squashfs_symlink_read_folio(struct file *file, struct folio *folio)
{
	struct inode *inode = folio->mapping->host;
	struct super_block *sb = inode->i_sb;
	struct squashfs_sb_info *msblk = sb->s_fs_info;
	int index = folio_pos(folio);
	u64 block = squashfs_i(inode)->start;
	int offset = squashfs_i(inode)->offset;
	int length = min_t(int, i_size_read(inode) - index, PAGE_SIZE);
	int bytes, copied, error;
	void *pageaddr;
	struct squashfs_cache_entry *entry;

	TRACE("Entered squashfs_symlink_readpage, page index %ld, start block "
			"%llx, offset %x\n", folio->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);
			error = bytes;
			goto out;
		}
	}

	/*
	 * Read length bytes from symlink metadata.  Squashfs_read_metadata
	 * is not used here because it can sleep and we want to use
	 * kmap_local to map the folio.  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);
			error = entry->error;
			goto out;
		}

		pageaddr = kmap_local_folio(folio, 0);
		copied = squashfs_copy_data(pageaddr + bytes, entry, offset,
								length - bytes);
		if (copied == length - bytes)
			memset(pageaddr + length, 0, PAGE_SIZE - length);
		else
			block = entry->next_index;
		kunmap_local(pageaddr);
		squashfs_cache_put(entry);
	}

	flush_dcache_folio(folio);
	error = 0;
out:
	folio_end_read(folio, error == 0);
	return error;
}


const struct address_space_operations squashfs_symlink_aops = {
	.read_folio = squashfs_symlink_read_folio
};

const struct inode_operations squashfs_symlink_inode_ops = {
	.get_link = page_get_link,
	.listxattr = squashfs_listxattr
};
Commit	Line	Data
	1	// SPDX-License-Identifier: GPL-2.0-or-later
	2	/*
	3	* Squashfs - a compressed read only filesystem for Linux
	4	*
	5	* Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
	6	* Phillip Lougher <phillip@squashfs.org.uk>
	7	*
	8	* symlink.c
	9	*/
	10
	11	/*
	12	* This file implements code to handle symbolic links.
	13	*
	14	* The data contents of symbolic links are stored inside the symbolic
	15	* link inode within the inode table. This allows the normally small symbolic
	16	* link to be compressed as part of the inode table, achieving much greater
	17	* compression than if the symbolic link was compressed individually.
	18	*/
	19
	20	#include <linux/fs.h>
	21	#include <linux/vfs.h>
	22	#include <linux/kernel.h>
	23	#include <linux/string.h>
	24	#include <linux/pagemap.h>
	25	#include <linux/xattr.h>
	26
	27	#include "squashfs_fs.h"
	28	#include "squashfs_fs_sb.h"
	29	#include "squashfs_fs_i.h"
	30	#include "squashfs.h"
	31	#include "xattr.h"
	32
	33	static int squashfs_symlink_read_folio(struct file file, struct folio folio)
	34	{
	35	struct inode *inode = folio->mapping->host;
	36	struct super_block *sb = inode->i_sb;
	37	struct squashfs_sb_info *msblk = sb->s_fs_info;
	38	int index = folio_pos(folio);
	39	u64 block = squashfs_i(inode)->start;
	40	int offset = squashfs_i(inode)->offset;
	41	int length = min_t(int, i_size_read(inode) - index, PAGE_SIZE);
	42	int bytes, copied, error;
	43	void *pageaddr;
	44	struct squashfs_cache_entry *entry;
	45
	46	TRACE("Entered squashfs_symlink_readpage, page index %ld, start block "
	47	"%llx, offset %x\n", folio->index, block, offset);
	48
	49	/*
	50	* Skip index bytes into symlink metadata.
	51	*/
	52	if (index) {
	53	bytes = squashfs_read_metadata(sb, NULL, &block, &offset,
	54	index);
	55	if (bytes < 0) {
	56	ERROR("Unable to read symlink [%llx:%x]\n",
	57	squashfs_i(inode)->start,
	58	squashfs_i(inode)->offset);
	59	error = bytes;
	60	goto out;
	61	}
	62	}
	63
	64	/*
	65	* Read length bytes from symlink metadata. Squashfs_read_metadata
	66	* is not used here because it can sleep and we want to use
	67	* kmap_local to map the folio. Instead call the underlying
	68	* squashfs_cache_get routine. As length bytes may overlap metadata
	69	* blocks, we may need to call squashfs_cache_get multiple times.
	70	*/
	71	for (bytes = 0; bytes < length; offset = 0, bytes += copied) {
	72	entry = squashfs_cache_get(sb, msblk->block_cache, block, 0);
	73	if (entry->error) {
	74	ERROR("Unable to read symlink [%llx:%x]\n",
	75	squashfs_i(inode)->start,
	76	squashfs_i(inode)->offset);
	77	squashfs_cache_put(entry);
	78	error = entry->error;
	79	goto out;
	80	}
	81
	82	pageaddr = kmap_local_folio(folio, 0);
	83	copied = squashfs_copy_data(pageaddr + bytes, entry, offset,
	84	length - bytes);
	85	if (copied == length - bytes)
	86	memset(pageaddr + length, 0, PAGE_SIZE - length);
	87	else
	88	block = entry->next_index;
	89	kunmap_local(pageaddr);
	90	squashfs_cache_put(entry);
	91	}
	92
	93	flush_dcache_folio(folio);
	94	error = 0;
	95	out:
	96	folio_end_read(folio, error == 0);
	97	return error;
	98	}
	99
	100
	101	const struct address_space_operations squashfs_symlink_aops = {
	102	.read_folio = squashfs_symlink_read_folio
	103	};
	104
	105	const struct inode_operations squashfs_symlink_inode_ops = {
	106	.get_link = page_get_link,
	107	.listxattr = squashfs_listxattr
	108	};
	109