path: root/fs/ext3/xattr.c

/*
 * linux/fs/ext3/xattr.c
 *
 * Copyright (C) 2001-2003 Andreas Gruenbacher, <agruen@suse.de>
 *
 * Fix by Harrison Xing <harrison@mountainviewdata.com>.
 * Ext3 code with a lot of help from Eric Jarman <ejarman@acm.org>.
 * Extended attributes for symlinks and special files added per
 *  suggestion of Luka Renko <luka.renko@hermes.si>.
 * xattr consolidation Copyright (c) 2004 James Morris <jmorris@redhat.com>,
 *  Red Hat Inc.
 * ea-in-inode support by Alex Tomas <alex@clusterfs.com> aka bzzz
 *  and Andreas Gruenbacher <agruen@suse.de>.
 */

/*
 * Extended attributes are stored directly in inodes (on file systems with
 * inodes bigger than 128 bytes) and on additional disk blocks. The i_file_acl
 * field contains the block number if an inode uses an additional block. All
 * attributes must fit in the inode and one additional block. Blocks that
 * contain the identical set of attributes may be shared among several inodes.
 * Identical blocks are detected by keeping a cache of blocks that have
 * recently been accessed.
 *
 * The attributes in inodes and on blocks have a different header; the entries
 * are stored in the same format:
 *
 *   +------------------+
 *   | header           |
 *   | entry 1          | |
 *   | entry 2          | | growing downwards
 *   | entry 3          | v
 *   | four null bytes  |
 *   | . . .            |
 *   | value 1          | ^
 *   | value 3          | | growing upwards
 *   | value 2          | |
 *   +------------------+
 *
 * The header is followed by multiple entry descriptors. In disk blocks, the
 * entry descriptors are kept sorted. In inodes, they are unsorted. The
 * attribute values are aligned to the end of the block in no specific order.
 *
 * Locking strategy
 * ----------------
 * EXT3_I(inode)->i_file_acl is protected by EXT3_I(inode)->xattr_sem.
 * EA blocks are only changed if they are exclusive to an inode, so
 * holding xattr_sem also means that nothing but the EA block's reference
 * count can change. Multiple writers to the same block are synchronized
 * by the buffer lock.
 */

#include <linux/init.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/ext3_jbd.h>
#include <linux/ext3_fs.h>
#include <linux/mbcache.h>
#include <linux/quotaops.h>
#include <linux/rwsem.h>
#include "xattr.h"
#include "acl.h"

#define BHDR(bh) ((struct ext3_xattr_header *)((bh)->b_data))
#define ENTRY(ptr) ((struct ext3_xattr_entry *)(ptr))
#define BFIRST(bh) ENTRY(BHDR(bh)+1)
#define IS_LAST_ENTRY(entry) (*(__u32 *)(entry) == 0)

#define IHDR(inode, raw_inode) \
	((struct ext3_xattr_ibody_header *) \
		((void *)raw_inode + \
		 EXT3_GOOD_OLD_INODE_SIZE + \
		 EXT3_I(inode)->i_extra_isize))
#define IFIRST(hdr) ((struct ext3_xattr_entry *)((hdr)+1))

#ifdef EXT3_XATTR_DEBUG
# define ea_idebug(inode, f...) do { \
		printk(KERN_DEBUG "inode %s:%lu: ", \
			inode->i_sb->s_id, inode->i_ino); \
		printk(f); \
		printk("\n"); \
	} while (0)
# define ea_bdebug(bh, f...) do { \
		char b[BDEVNAME_SIZE]; \
		printk(KERN_DEBUG "block %s:%lu: ", \
			bdevname(bh->b_bdev, b), \
			(unsigned long) bh->b_blocknr); \
		printk(f); \
		printk("\n"); \
	} while (0)
#else
# define ea_idebug(f...)
# define ea_bdebug(f...)
#endif

static void ext3_xattr_cache_insert(struct buffer_head *);
static struct buffer_head *ext3_xattr_cache_find(struct inode *,
						 struct ext3_xattr_header *,
						 struct mb_cache_entry **);
static void ext3_xattr_rehash(struct ext3_xattr_header *,
			      struct ext3_xattr_entry *);
static int ext3_xattr_list(struct inode *inode, char *buffer,
			   size_t buffer_size);

static struct mb_cache *ext3_xattr_cache;

static struct xattr_handler *ext3_xattr_handler_map[] = {
	[EXT3_XATTR_INDEX_USER]		     = &ext3_xattr_user_handler,
#ifdef CONFIG_EXT3_FS_POSIX_ACL
	[EXT3_XATTR_INDEX_POSIX_ACL_ACCESS]  = &ext3_xattr_acl_access_handler,
	[EXT3_XATTR_INDEX_POSIX_ACL_DEFAULT] = &ext3_xattr_acl_default_handler,
#endif
	[EXT3_XATTR_INDEX_TRUSTED]	     = &ext3_xattr_trusted_handler,
#ifdef CONFIG_EXT3_FS_SECURITY
	[EXT3_XATTR_INDEX_SECURITY]	     = &ext3_xattr_security_handler,
#endif
};

struct xattr_handler *ext3_xattr_handlers[] = {
	&ext3_xattr_user_handler,
	&ext3_xattr_trusted_handler,
#ifdef CONFIG_EXT3_FS_POSIX_ACL
	&