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.
 *
 * Locking works like so:
 * Directory components (xattr root, xattr dir) are protectd by their i_mutex.
 * The xattrs themselves are protected by the xattr_sem.
 */

#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/stat.h>
#include <linux/quotaops.h>

#define PRIVROOT_NAME ".reiserfs_priv"
#define XAROOT_NAME   "xattrs"


/* Helpers for inode ops. We do this so that we don't have all the VFS
 * overhead and also for proper i_mutex annotation.
 * dir->i_mutex must be held for all of them. */
#ifdef CONFIG_REISERFS_FS_XATTR
static int xattr_create(struct inode *dir, struct dentry *dentry, int mode)
{
	BUG_ON(!mutex_is_locked(&dir->i_mutex));
	vfs_dq_init(dir);
	return dir->i_op->create(dir, dentry, mode, NULL);
}
#endif

static int xattr_mkdir(struct inode *dir, struct dentry *dentry, int mode)
{
	BUG_ON(!mutex_is_locked(&dir->i_mutex));
	vfs_dq_init(dir);
	return dir->i_op->mkdir(dir, dentry, mode);
}

/* We use I_MUTEX_CHILD here to silence lockdep. It's safe because xattr
 * mutation ops aren't called during rename or splace, which are the
 * only other users of I_MUTEX_CHILD. It violates the ordering, but that's
 * better than allocating another subclass just for this code. */
static int xattr_unlink(struct inode *dir, struct dentry *dentry)
{
	int error;
	BUG_ON(!mutex_is_locked(&dir->i_mutex));
	vfs_dq_init(dir);

	reiserfs_mutex_lock_nested_safe(&dentry->d_inode->i_mutex,
					I_MUTEX_CHILD, dir->i_sb);
	error = dir->i_op->unlink(dir, dentry);
	mutex_unlock(&dentry->d_inode->i_mutex);

	if (!error)
		d_delete(dentry);
	return error;
}

static int xattr_rmdir(struct inode *dir, struct dentry *dentry)
{
	int error;
	BUG_ON(!mutex_is_locked(&dir->i_mutex));
	vfs_dq_init(dir);

	mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_CHILD);
	dentry_unhash(dentry);
	error = dir->i_op->rmdir(dir, dentry);
	if (!error)
		dentry->d_inode->i_flags |= S_DEAD;
	mutex_unlock(&dentry->d_inode->i_mutex);
	if (!error)
		d_delete(dentry);
	dput(dentry);

	return error;
}

#define xattr_may_create(flags)	(!flags || flags & XATTR_CREATE)

static struct dentry *open_xa_root(struct super_block *sb, int flags)
{
	struct dentry *privroot = REISERFS_SB(sb)->priv_root;
	struct dentry *xaroot;
	if (!privroot->d_inode)
		return ERR_PTR(-ENODATA);

	mutex_lock_nested(&privroot->d_inode->i_mutex, I_MUTEX_XATTR);

	xaroot = dget(REISERFS_SB(sb)->xattr_root);
	if (!xaroot)
		xaroot = ERR_PTR(-ENODATA);
	else if (!xaroot->d_inode) {
		int err = -ENODATA;
		if (xattr_may_create(flags))
			err = xattr_mkdir(privroot->d_inode, xaroot, 0700);
		if (err) {
			dput(xaroot);
			xaroot = ERR_PTR(err);
		}
	}

	mutex_unlock(&privroot->d_inode->i_mutex);
	return xaroot;
}

static struct dentry *open_xa_dir(const struct inode *inode, int flags)
{
	struct dentry *xaroot, *xadir;
	char namebuf[17];

	xaroot = open_xa_root(inode->i_sb, flags);
	if (IS_ERR(xaroot))
		return xaroot;

	snprintf