path: root/fs/reiserfs/xattr.c

/*
 * linux/fs/reiserfs/xattr.c
 *
 * Copyright (c) 2002 by Jeff Mahoney, <jeffm@suse.com>
 *
 */

/*
 * In order to implement EA/ACLs in a clean, backwards compatible manner,
 * they are implemented as files in a "private" directory.
 * Each EA is in it's own file, with the directory layout like so (/ is assumed
 * to be relative to fs root). Inside the /.reiserfs_priv/xattrs directory,
 * directories named using the capital-hex form of the objectid and
 * generation number are used. Inside each directory are individual files
 * named with the name of the extended attribute.
 *
 * So, for objectid 12648430, we could have:
 * /.reiserfs_priv/xattrs/C0FFEE.0/system.posix_acl_access
 * /.reiserfs_priv/xattrs/C0FFEE.0/system.posix_acl_default
 * /.reiserfs_priv/xattrs/C0FFEE.0/user.Content-Type
 * .. or similar.
 *
 * The file contents are the text of the EA. The size is known based on the
 * stat data describing the file.
 *
 * In the case of system.posix_acl_access and system.posix_acl_default, since
 * these are special cases for filesystem ACLs, they are interpreted by the
 * kernel, in addition, they are negatively and positively cached and attached
 * to the inode so that unnecessary lookups are avoided.
 */

#include <linux/reiserfs_fs.h>
#include <linux/capability.h>
#include <linux/dcache.h>
#include <linux/namei.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/pagemap.h>
#include <linux/xattr.h>
#include <linux/reiserfs_xattr.h>
#include <linux/reiserfs_acl.h>
#include <asm/uaccess.h>
#include <net/checksum.h>
#include <linux/smp_lock.h>
#include <linux/stat.h>
#include <asm/semaphore.h>

#define FL_READONLY 128
#define FL_DIR_SEM_HELD 256
#define PRIVROOT_NAME ".reiserfs_priv"
#define XAROOT_NAME   "xattrs"

static struct reiserfs_xattr_handler *find_xattr_handler_prefix(const char
								*prefix);

/* Returns the dentry referring to the root of the extended attribute
 * directory tree. If it has already been retrieved, it is used. If it
 * hasn't been created and the flags indicate creation is allowed, we
 * attempt to create it. On error, we return a pointer-encoded error.
 */
static struct dentry *get_xa_root(struct super_block *sb, int flags)
{
	struct dentry *privroot = dget(REISERFS_SB(sb)->priv_root);
	struct dentry *xaroot;

	/* This needs to be created at mount-time */
	if (!privroot)
		return ERR_PTR(-ENODATA);

	mutex_lock_nested(&privroot->d_inode->i_mutex, I_MUTEX_XATTR);
	if (REISERFS_SB(sb)->xattr_root) {
		xaroot = dget(REISERFS_SB(sb)->xattr_root);
		goto out;
	}

	xaroot = lookup_one_len(XAROOT_NAME, privroot, strlen(XAROOT_NAME));
	if (IS_ERR(xaroot)) {
		goto out;
	} else if (!xaroot->d_inode) {
		int err = -ENODATA;
		if (flags == 0 || flags & XATTR_CREATE)
			err = privroot->d_inode->i_op->mkdir(privroot->d_inode,
			                                     xaroot, 0700);
		if (err) {
			dput(xaroot);
			xaroot = ERR_PTR(err);
			goto out;
		}
	}
	REISERFS_SB(sb)->xattr_root = dget(