path: root/fs/xfs/xfs_attr_remote.h

/*
 * Copyright (c) 2013 Red Hat, Inc.
 * All Rights Reserved.
 *
 * 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.
 *
 * This program is distributed in the hope that it would 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 the Free Software Foundation,
 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
#ifndef __XFS_ATTR_REMOTE_H__
#define	__XFS_ATTR_REMOTE_H__

#define XFS_ATTR3_RMT_MAGIC	0x5841524d	/* XARM */

/*
 * There is one of these headers per filesystem block in a remote attribute.
 * This is done to ensure there is a 1:1 mapping between the attribute value
 * length and the number of blocks needed to store the attribute. This makes the
 * verification of a buffer a little more complex, but greatly simplifies the
 * allocation, reading and writing of these attributes as we don't have to guess
 * the number of blocks needed to store the attribute data.
 */
struct xfs_attr3_rmt_hdr {
	__be32	rm_magic;
	__be32	rm_offset;
	__be32	rm_bytes;
	__be32	rm_crc;
	uuid_t	rm_uuid;
	__be64	rm_owner;
	__be64	rm_blkno;
	__be64	rm_lsn;
};

#define XFS_ATTR3_RMT_CRC_OFF	offsetof(struct xfs_attr3_rmt_hdr, rm_crc)

#define XFS_ATTR3_RMT_BUF_SPACE(mp, bufsize)	\
	((bufsize) - (xfs_sb_version_hascrc(&(mp)->m_sb) ? \
			sizeof(struct xfs_attr3_rmt_hdr) : 0))

extern const struct xfs_buf_ops xfs_attr3_rmt_buf_ops;

int xfs_attr3_rmt_blocks(struct xfs_mount *mp, int attrlen);

int xfs_attr_rmtval_get(struct xfs_da_args *args);
int xfs_attr_rmtval_set(struct xfs_da_args *args);
int xfs_attr_rmtval_remove(struct xfs_da_args *args);

#endif /* __XFS_ATTR_REMOTE_H__ */