fs/xfs/xfs_attr_remote.c - third_party/linux - Git at Google

 /*
  * Copyright (c) 2000-2005 Silicon Graphics, Inc.
  * 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
  */
 #include "xfs.h"
 #include "xfs_fs.h"
 #include "xfs_types.h"
 #include "xfs_bit.h"
 #include "xfs_log.h"
 #include "xfs_trans.h"
 #include "xfs_trans_priv.h"
 #include "xfs_sb.h"
 #include "xfs_ag.h"
 #include "xfs_mount.h"
 #include "xfs_error.h"
 #include "xfs_da_btree.h"
 #include "xfs_bmap_btree.h"
 #include "xfs_dinode.h"
 #include "xfs_inode.h"
 #include "xfs_alloc.h"
 #include "xfs_inode_item.h"
 #include "xfs_bmap.h"
 #include "xfs_bmap_util.h"
 #include "xfs_attr.h"
 #include "xfs_attr_leaf.h"
 #include "xfs_attr_remote.h"
 #include "xfs_trans_space.h"
 #include "xfs_trace.h"
 #include "xfs_cksum.h"
 #include "xfs_buf_item.h"

 #define ATTR_RMTVALUE_MAPSIZE	1	/* # of map entries at once */

 /*
  * Each contiguous block has a header, so it is not just a simple attribute
  * length to FSB conversion.
  */
 int
 xfs_attr3_rmt_blocks(
 	struct xfs_mount *mp,
 	int		attrlen)
 {
 	if (xfs_sb_version_hascrc(&mp->m_sb)) {
 		int buflen = XFS_ATTR3_RMT_BUF_SPACE(mp, mp->m_sb.sb_blocksize);
 		return (attrlen + buflen - 1) / buflen;
 	}
 	return XFS_B_TO_FSB(mp, attrlen);
 }

 /*
  * Checking of the remote attribute header is split into two parts. The verifier
  * does CRC, location and bounds checking, the unpacking function checks the
  * attribute parameters and owner.
  */
 static bool
 xfs_attr3_rmt_hdr_ok(
 	struct xfs_mount	*mp,
 	void			*ptr,
 	xfs_ino_t		ino,
 	uint32_t		offset,
 	uint32_t		size,
 	xfs_daddr_t		bno)
 {
 	struct xfs_attr3_rmt_hdr *rmt = ptr;

 	if (bno != be64_to_cpu(rmt->rm_blkno))
 		return false;
 	if (offset != be32_to_cpu(rmt->rm_offset))
 		return false;
 	if (size != be32_to_cpu(rmt->rm_bytes))
 		return false;
 	if (ino != be64_to_cpu(rmt->rm_owner))
 		return false;

 	/* ok */
 	return true;
 }

 static bool
 xfs_attr3_rmt_verify(
 	struct xfs_mount	*mp,
 	void			*ptr,
 	int			fsbsize,
 	xfs_daddr_t		bno)
 {
 	struct xfs_attr3_rmt_hdr *rmt = ptr;

 	if (!xfs_sb_version_hascrc(&mp->m_sb))
 		return false;
 	if (rmt->rm_magic != cpu_to_be32(XFS_ATTR3_RMT_MAGIC))
 		return false;
 	if (!uuid_equal(&rmt->rm_uuid, &mp->m_sb.sb_uuid))
 		return false;
 	if (be64_to_cpu(rmt->rm_blkno) != bno)
 		return false;
 	if (be32_to_cpu(rmt->rm_bytes) > fsbsize - sizeof(*rmt))
 		return false;
 	if (be32_to_cpu(rmt->rm_offset) +
 				be32_to_cpu(rmt->rm_bytes) >= XATTR_SIZE_MAX)
 		return false;
 	if (rmt->rm_owner == 0)
 		return false;

 	return true;
 }

 static void
 xfs_attr3_rmt_read_verify(
 	struct xfs_buf	*bp)
 {
 	struct xfs_mount *mp = bp->b_target->bt_mount;
 	char		*ptr;
 	int		len;
 	bool		corrupt = false;
 	xfs_daddr_t	bno;

 	/* no verification of non-crc buffers */
 	if (!xfs_sb_version_hascrc(&mp->m_sb))
 		return;

 	ptr = bp->b_addr;
 	bno = bp->b_bn;
 	len = BBTOB(bp->b_length);
 	ASSERT(len >= XFS_LBSIZE(mp));

 	while (len > 0) {
 		if (!xfs_verify_cksum(ptr, XFS_LBSIZE(mp),
 				      XFS_ATTR3_RMT_CRC_OFF)) {
 			corrupt = true;
 			break;
 		}
 		if (!xfs_attr3_rmt_verify(mp, ptr, XFS_LBSIZE(mp), bno)) {
 			corrupt = true;
 			break;
 		}
 		len -= XFS_LBSIZE(mp);
 		ptr += XFS_LBSIZE(mp);
 		bno += mp->m_bsize;
 	}

 	if (corrupt) {
 		XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp, bp->b_addr);
 		xfs_buf_ioerror(bp, EFSCORRUPTED);
 	} else
 		ASSERT(len == 0);
 }

 static void
 xfs_attr3_rmt_write_verify(
 	struct xfs_buf	*bp)
 {
 	struct xfs_mount *mp = bp->b_target->bt_mount;
 	struct xfs_buf_log_item	*bip = bp->b_fspriv;
 	char		*ptr;
 	int		len;
 	xfs_daddr_t	bno;

 	/* no verification of non-crc buffers */
 	if (!xfs_sb_version_hascrc(&mp->m_sb))
 		return;

 	ptr = bp->b_addr;
 	bno = bp->b_bn;
 	len = BBTOB(bp->b_length);
 	ASSERT(len >= XFS_LBSIZE(mp));

 	while (len > 0) {
 		if (!xfs_attr3_rmt_verify(mp, ptr, XFS_LBSIZE(mp), bno)) {
 			XFS_CORRUPTION_ERROR(__func__,
 					    XFS_ERRLEVEL_LOW, mp, bp->b_addr);
 			xfs_buf_ioerror(bp, EFSCORRUPTED);
 			return;
 		}
 		if (bip) {
 			struct xfs_attr3_rmt_hdr *rmt;

 			rmt = (struct xfs_attr3_rmt_hdr *)ptr;
 			rmt->rm_lsn = cpu_to_be64(bip->bli_item.li_lsn);
 		}
 		xfs_update_cksum(ptr, XFS_LBSIZE(mp), XFS_ATTR3_RMT_CRC_OFF);

 		len -= XFS_LBSIZE(mp);
 		ptr += XFS_LBSIZE(mp);
 		bno += mp->m_bsize;
 	}
 	ASSERT(len == 0);
 }

 const struct xfs_buf_ops xfs_attr3_rmt_buf_ops = {
 	.verify_read = xfs_attr3_rmt_read_verify,
 	.verify_write = xfs_attr3_rmt_write_verify,
 };

 STATIC int
 xfs_attr3_rmt_hdr_set(
 	struct xfs_mount	*mp,
 	void			*ptr,
 	xfs_ino_t		ino,
 	uint32_t		offset,
 	uint32_t		size,
 	xfs_daddr_t		bno)
 {
 	struct xfs_attr3_rmt_hdr *rmt = ptr;

 	if (!xfs_sb_version_hascrc(&mp->m_sb))
 		return 0;

 	rmt->rm_magic = cpu_to_be32(XFS_ATTR3_RMT_MAGIC);
 	rmt->rm_offset = cpu_to_be32(offset);
 	rmt->rm_bytes = cpu_to_be32(size);
 	uuid_copy(&rmt->rm_uuid, &mp->m_sb.sb_uuid);
 	rmt->rm_owner = cpu_to_be64(ino);
 	rmt->rm_blkno = cpu_to_be64(bno);

 	return sizeof(struct xfs_attr3_rmt_hdr);
 }

 /*
  * Helper functions to copy attribute data in and out of the one disk extents
  */
 STATIC int
 xfs_attr_rmtval_copyout(
 	struct xfs_mount *mp,
 	struct xfs_buf	*bp,
 	xfs_ino_t	ino,
 	int		*offset,
 	int		*valuelen,
 	__uint8_t	**dst)
 {
 	char		*src = bp->b_addr;
 	xfs_daddr_t	bno = bp->b_bn;
 	int		len = BBTOB(bp->b_length);

 	ASSERT(len >= XFS_LBSIZE(mp));

 	while (len > 0 && *valuelen > 0) {
 		int hdr_size = 0;
 		int byte_cnt = XFS_ATTR3_RMT_BUF_SPACE(mp, XFS_LBSIZE(mp));

 		byte_cnt = min(*valuelen, byte_cnt);

 		if (xfs_sb_version_hascrc(&mp->m_sb)) {
 			if (!xfs_attr3_rmt_hdr_ok(mp, src, ino, *offset,
 						  byte_cnt, bno)) {
 				xfs_alert(mp,
 "remote attribute header mismatch bno/off/len/owner (0x%llx/0x%x/Ox%x/0x%llx)",
 					bno, *offset, byte_cnt, ino);
 				return EFSCORRUPTED;
 			}
 			hdr_size = sizeof(struct xfs_attr3_rmt_hdr);
 		}

 		memcpy(*dst, src + hdr_size, byte_cnt);

 		/* roll buffer forwards */
 		len -= XFS_LBSIZE(mp);
 		src += XFS_LBSIZE(mp);
 		bno += mp->m_bsize;

 		/* roll attribute data forwards */
 		*valuelen -= byte_cnt;
 		*dst += byte_cnt;
 		*offset += byte_cnt;
 	}
 	return 0;
 }

 STATIC void
 xfs_attr_rmtval_copyin(
 	struct xfs_mount *mp,
 	struct xfs_buf	*bp,
 	xfs_ino_t	ino,
 	int		*offset,
 	int		*valuelen,
 	__uint8_t	**src)
 {
 	char		*dst = bp->b_addr;
 	xfs_daddr_t	bno = bp->b_bn;
 	int		len = BBTOB(bp->b_length);

 	ASSERT(len >= XFS_LBSIZE(mp));

 	while (len > 0 && *valuelen > 0) {
 		int hdr_size;
 		int byte_cnt = XFS_ATTR3_RMT_BUF_SPACE(mp, XFS_LBSIZE(mp));

 		byte_cnt = min(*valuelen, byte_cnt);
 		hdr_size = xfs_attr3_rmt_hdr_set(mp, dst, ino, *offset,
 						 byte_cnt, bno);

 		memcpy(dst + hdr_size, *src, byte_cnt);

 		/*
 		 * If this is the last block, zero the remainder of it.
 		 * Check that we are actually the last block, too.
 		 */
 		if (byte_cnt + hdr_size < XFS_LBSIZE(mp)) {
 			ASSERT(*valuelen - byte_cnt == 0);
 			ASSERT(len == XFS_LBSIZE(mp));
 			memset(dst + hdr_size + byte_cnt, 0,
 					XFS_LBSIZE(mp) - hdr_size - byte_cnt);
 		}

 		/* roll buffer forwards */
 		len -= XFS_LBSIZE(mp);
 		dst += XFS_LBSIZE(mp);
 		bno += mp->m_bsize;

 		/* roll attribute data forwards */
 		*valuelen -= byte_cnt;
 		*src += byte_cnt;
 		*offset += byte_cnt;
 	}
 }

 /*
  * Read the value associated with an attribute from the out-of-line buffer
  * that we stored it in.
  */
 int
 xfs_attr_rmtval_get(
 	struct xfs_da_args	*args)
 {
 	struct xfs_bmbt_irec	map[ATTR_RMTVALUE_MAPSIZE];
 	struct xfs_mount	*mp = args->dp->i_mount;
 	struct xfs_buf		*bp;
 	xfs_dablk_t		lblkno = args->rmtblkno;
 	__uint8_t		*dst = args->value;
 	int			valuelen = args->valuelen;
 	int			nmap;
 	int			error;
 	int			blkcnt = args->rmtblkcnt;
 	int			i;
 	int			offset = 0;

 	trace_xfs_attr_rmtval_get(args);

 	ASSERT(!(args->flags & ATTR_KERNOVAL));

 	while (valuelen > 0) {
 		nmap = ATTR_RMTVALUE_MAPSIZE;
 		error = xfs_bmapi_read(args->dp, (xfs_fileoff_t)lblkno,
 				       blkcnt, map, &nmap,
 				       XFS_BMAPI_ATTRFORK);
 		if (error)
 			return error;
 		ASSERT(nmap >= 1);

 		for (i = 0; (i < nmap) && (valuelen > 0); i++) {
 			xfs_daddr_t	dblkno;
 			int		dblkcnt;

 			ASSERT((map[i].br_startblock != DELAYSTARTBLOCK) &&
 			       (map[i].br_startblock != HOLESTARTBLOCK));
 			dblkno = XFS_FSB_TO_DADDR(mp, map[i].br_startblock);
 			dblkcnt = XFS_FSB_TO_BB(mp, map[i].br_blockcount);
 			error = xfs_trans_read_buf(mp, NULL, mp->m_ddev_targp,
 						   dblkno, dblkcnt, 0, &bp,
 						   &xfs_attr3_rmt_buf_ops);
 			if (error)
 				return error;

 			error = xfs_attr_rmtval_copyout(mp, bp, args->dp->i_ino,
 							&offset, &valuelen,
 							&dst);
 			xfs_buf_relse(bp);
 			if (error)
 				return error;

 			/* roll attribute extent map forwards */
 			lblkno += map[i].br_blockcount;
 			blkcnt -= map[i].br_blockcount;
 		}
 	}
 	ASSERT(valuelen == 0);
 	return 0;
 }

 /*
  * Write the value associated with an attribute into the out-of-line buffer
  * that we have defined for it.
  */
 int
 xfs_attr_rmtval_set(
 	struct xfs_da_args	*args)
 {
 	struct xfs_inode	*dp = args->dp;
 	struct xfs_mount	*mp = dp->i_mount;
 	struct xfs_bmbt_irec	map;
 	xfs_dablk_t		lblkno;
 	xfs_fileoff_t		lfileoff = 0;
 	__uint8_t		*src = args->value;
 	int			blkcnt;
 	int			valuelen;
 	int			nmap;
 	int			error;
 	int			offset = 0;

 	trace_xfs_attr_rmtval_set(args);

 	/*
 	 * Find a "hole" in the attribute address space large enough for
 	 * us to drop the new attribute's value into. Because CRC enable
 	 * attributes have headers, we can't just do a straight byte to FSB
 	 * conversion and have to take the header space into account.
 	 */
 	blkcnt = xfs_attr3_rmt_blocks(mp, args->valuelen);
 	error = xfs_bmap_first_unused(args->trans, args->dp, blkcnt, &lfileoff,
 						   XFS_ATTR_FORK);
 	if (error)
 		return error;

 	args->rmtblkno = lblkno = (xfs_dablk_t)lfileoff;
 	args->rmtblkcnt = blkcnt;

 	/*
 	 * Roll through the "value", allocating blocks on disk as required.
 	 */
 	while (blkcnt > 0) {
 		int	committed;

 		/*
 		 * Allocate a single extent, up to the size of the value.
 		 */
 		xfs_bmap_init(args->flist, args->firstblock);
 		nmap = 1;
 		error = xfs_bmapi_write(args->trans, dp, (xfs_fileoff_t)lblkno,
 				  blkcnt,
 				  XFS_BMAPI_ATTRFORK | XFS_BMAPI_METADATA,
 				  args->firstblock, args->total, &map, &nmap,
 				  args->flist);
 		if (!error) {
 			error = xfs_bmap_finish(&args->trans, args->flist,
 						&committed);
 		}
 		if (error) {
 			ASSERT(committed);
 			args->trans = NULL;
 			xfs_bmap_cancel(args->flist);
 			return(error);
 		}

 		/*
 		 * bmap_finish() may have committed the last trans and started
 		 * a new one.  We need the inode to be in all transactions.
 		 */
 		if (committed)
 			xfs_trans_ijoin(args->trans, dp, 0);

 		ASSERT(nmap == 1);
 		ASSERT((map.br_startblock != DELAYSTARTBLOCK) &&
 		       (map.br_startblock != HOLESTARTBLOCK));
 		lblkno += map.br_blockcount;
 		blkcnt -= map.br_blockcount;

 		/*
 		 * Start the next trans in the chain.
 		 */
 		error = xfs_trans_roll(&args->trans, dp);
 		if (error)
 			return (error);
 	}

 	/*
 	 * Roll through the "value", copying the attribute value to the
 	 * already-allocated blocks.  Blocks are written synchronously
 	 * so that we can know they are all on disk before we turn off
 	 * the INCOMPLETE flag.
 	 */
 	lblkno = args->rmtblkno;
 	blkcnt = args->rmtblkcnt;
 	valuelen = args->valuelen;
 	while (valuelen > 0) {
 		struct xfs_buf	*bp;
 		xfs_daddr_t	dblkno;
 		int		dblkcnt;

 		ASSERT(blkcnt > 0);

 		xfs_bmap_init(args->flist, args->firstblock);
 		nmap = 1;
 		error = xfs_bmapi_read(dp, (xfs_fileoff_t)lblkno,
 				       blkcnt, &map, &nmap,
 				       XFS_BMAPI_ATTRFORK);
 		if (error)
 			return(error);
 		ASSERT(nmap == 1);
 		ASSERT((map.br_startblock != DELAYSTARTBLOCK) &&
 		       (map.br_startblock != HOLESTARTBLOCK));

 		dblkno = XFS_FSB_TO_DADDR(mp, map.br_startblock),
 		dblkcnt = XFS_FSB_TO_BB(mp, map.br_blockcount);

 		bp = xfs_buf_get(mp->m_ddev_targp, dblkno, dblkcnt, 0);
 		if (!bp)
 			return ENOMEM;
 		bp->b_ops = &xfs_attr3_rmt_buf_ops;

 		xfs_attr_rmtval_copyin(mp, bp, args->dp->i_ino, &offset,
 				       &valuelen, &src);

 		error = xfs_bwrite(bp);	/* GROT: NOTE: synchronous write */
 		xfs_buf_relse(bp);
 		if (error)
 			return error;


 		/* roll attribute extent map forwards */
 		lblkno += map.br_blockcount;
 		blkcnt -= map.br_blockcount;
 	}
 	ASSERT(valuelen == 0);
 	return 0;
 }

 /*
  * Remove the value associated with an attribute by deleting the
  * out-of-line buffer that it is stored on.
  */
 int
 xfs_attr_rmtval_remove(
 	struct xfs_da_args	*args)
 {
 	struct xfs_mount	*mp = args->dp->i_mount;
 	xfs_dablk_t		lblkno;
 	int			blkcnt;
 	int			error;
 	int			done;

 	trace_xfs_attr_rmtval_remove(args);

 	/*
 	 * Roll through the "value", invalidating the attribute value's blocks.
 	 */
 	lblkno = args->rmtblkno;
 	blkcnt = args->rmtblkcnt;
 	while (blkcnt > 0) {
 		struct xfs_bmbt_irec	map;
 		struct xfs_buf		*bp;
 		xfs_daddr_t		dblkno;
 		int			dblkcnt;
 		int			nmap;

 		/*
 		 * Try to remember where we decided to put the value.
 		 */
 		nmap = 1;
 		error = xfs_bmapi_read(args->dp, (xfs_fileoff_t)lblkno,
 				       blkcnt, &map, &nmap, XFS_BMAPI_ATTRFORK);
 		if (error)
 			return(error);
 		ASSERT(nmap == 1);
 		ASSERT((map.br_startblock != DELAYSTARTBLOCK) &&
 		       (map.br_startblock != HOLESTARTBLOCK));

 		dblkno = XFS_FSB_TO_DADDR(mp, map.br_startblock),
 		dblkcnt = XFS_FSB_TO_BB(mp, map.br_blockcount);

 		/*
 		 * If the "remote" value is in the cache, remove it.
 		 */
 		bp = xfs_incore(mp->m_ddev_targp, dblkno, dblkcnt, XBF_TRYLOCK);
 		if (bp) {
 			xfs_buf_stale(bp);
 			xfs_buf_relse(bp);
 			bp = NULL;
 		}

 		lblkno += map.br_blockcount;
 		blkcnt -= map.br_blockcount;
 	}

 	/*
 	 * Keep de-allocating extents until the remote-value region is gone.
 	 */
 	lblkno = args->rmtblkno;
 	blkcnt = args->rmtblkcnt;
 	done = 0;
 	while (!done) {
 		int committed;

 		xfs_bmap_init(args->flist, args->firstblock);
 		error = xfs_bunmapi(args->trans, args->dp, lblkno, blkcnt,
 				    XFS_BMAPI_ATTRFORK | XFS_BMAPI_METADATA,
 				    1, args->firstblock, args->flist,
 				    &done);
 		if (!error) {
 			error = xfs_bmap_finish(&args->trans, args->flist,
 						&committed);
 		}
 		if (error) {
 			ASSERT(committed);
 			args->trans = NULL;
 			xfs_bmap_cancel(args->flist);
 			return error;
 		}

 		/*
 		 * bmap_finish() may have committed the last trans and started
 		 * a new one.  We need the inode to be in all transactions.
 		 */
 		if (committed)
 			xfs_trans_ijoin(args->trans, args->dp, 0);

 		/*
 		 * Close out trans and start the next one in the chain.
 		 */
 		error = xfs_trans_roll(&args->trans, args->dp);
 		if (error)
 			return (error);
 	}
 	return(0);
 }
	/*
	* Copyright (c) 2000-2005 Silicon Graphics, Inc.
	* 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
	*/
	#include "xfs.h"
	#include "xfs_fs.h"
	#include "xfs_types.h"
	#include "xfs_bit.h"
	#include "xfs_log.h"
	#include "xfs_trans.h"
	#include "xfs_trans_priv.h"
	#include "xfs_sb.h"
	#include "xfs_ag.h"
	#include "xfs_mount.h"
	#include "xfs_error.h"
	#include "xfs_da_btree.h"
	#include "xfs_bmap_btree.h"
	#include "xfs_dinode.h"
	#include "xfs_inode.h"
	#include "xfs_alloc.h"
	#include "xfs_inode_item.h"
	#include "xfs_bmap.h"
	#include "xfs_bmap_util.h"
	#include "xfs_attr.h"
	#include "xfs_attr_leaf.h"
	#include "xfs_attr_remote.h"
	#include "xfs_trans_space.h"
	#include "xfs_trace.h"
	#include "xfs_cksum.h"
	#include "xfs_buf_item.h"

	#define ATTR_RMTVALUE_MAPSIZE 1 /* # of map entries at once */

	/*
	* Each contiguous block has a header, so it is not just a simple attribute
	* length to FSB conversion.
	*/
	int
	xfs_attr3_rmt_blocks(
	struct xfs_mount *mp,
	int attrlen)
	{
	if (xfs_sb_version_hascrc(&mp->m_sb)) {
	int buflen = XFS_ATTR3_RMT_BUF_SPACE(mp, mp->m_sb.sb_blocksize);
	return (attrlen + buflen - 1) / buflen;
	}
	return XFS_B_TO_FSB(mp, attrlen);
	}

	/*
	* Checking of the remote attribute header is split into two parts. The verifier
	* does CRC, location and bounds checking, the unpacking function checks the
	* attribute parameters and owner.
	*/
	static bool
	xfs_attr3_rmt_hdr_ok(
	struct xfs_mount *mp,
	void *ptr,
	xfs_ino_t ino,
	uint32_t offset,
	uint32_t size,
	xfs_daddr_t bno)
	{
	struct xfs_attr3_rmt_hdr *rmt = ptr;

	if (bno != be64_to_cpu(rmt->rm_blkno))
	return false;
	if (offset != be32_to_cpu(rmt->rm_offset))
	return false;
	if (size != be32_to_cpu(rmt->rm_bytes))
	return false;
	if (ino != be64_to_cpu(rmt->rm_owner))
	return false;

	/* ok */
	return true;
	}

	static bool
	xfs_attr3_rmt_verify(
	struct xfs_mount *mp,
	void *ptr,
	int fsbsize,
	xfs_daddr_t bno)
	{
	struct xfs_attr3_rmt_hdr *rmt = ptr;

	if (!xfs_sb_version_hascrc(&mp->m_sb))
	return false;
	if (rmt->rm_magic != cpu_to_be32(XFS_ATTR3_RMT_MAGIC))
	return false;
	if (!uuid_equal(&rmt->rm_uuid, &mp->m_sb.sb_uuid))
	return false;
	if (be64_to_cpu(rmt->rm_blkno) != bno)
	return false;
	if (be32_to_cpu(rmt->rm_bytes) > fsbsize - sizeof(*rmt))
	return false;
	if (be32_to_cpu(rmt->rm_offset) +
	be32_to_cpu(rmt->rm_bytes) >= XATTR_SIZE_MAX)
	return false;
	if (rmt->rm_owner == 0)
	return false;

	return true;
	}

	static void
	xfs_attr3_rmt_read_verify(
	struct xfs_buf *bp)
	{
	struct xfs_mount *mp = bp->b_target->bt_mount;
	char *ptr;
	int len;
	bool corrupt = false;
	xfs_daddr_t bno;

	/* no verification of non-crc buffers */
	if (!xfs_sb_version_hascrc(&mp->m_sb))
	return;

	ptr = bp->b_addr;
	bno = bp->b_bn;
	len = BBTOB(bp->b_length);
	ASSERT(len >= XFS_LBSIZE(mp));

	while (len > 0) {
	if (!xfs_verify_cksum(ptr, XFS_LBSIZE(mp),
	XFS_ATTR3_RMT_CRC_OFF)) {
	corrupt = true;
	break;
	}
	if (!xfs_attr3_rmt_verify(mp, ptr, XFS_LBSIZE(mp), bno)) {
	corrupt = true;
	break;
	}
	len -= XFS_LBSIZE(mp);
	ptr += XFS_LBSIZE(mp);
	bno += mp->m_bsize;
	}

	if (corrupt) {
	XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp, bp->b_addr);
	xfs_buf_ioerror(bp, EFSCORRUPTED);
	} else
	ASSERT(len == 0);
	}

	static void
	xfs_attr3_rmt_write_verify(
	struct xfs_buf *bp)
	{
	struct xfs_mount *mp = bp->b_target->bt_mount;
	struct xfs_buf_log_item *bip = bp->b_fspriv;
	char *ptr;
	int len;
	xfs_daddr_t bno;

	/* no verification of non-crc buffers */
	if (!xfs_sb_version_hascrc(&mp->m_sb))
	return;

	ptr = bp->b_addr;
	bno = bp->b_bn;
	len = BBTOB(bp->b_length);
	ASSERT(len >= XFS_LBSIZE(mp));

	while (len > 0) {
	if (!xfs_attr3_rmt_verify(mp, ptr, XFS_LBSIZE(mp), bno)) {
	XFS_CORRUPTION_ERROR(__func__,
	XFS_ERRLEVEL_LOW, mp, bp->b_addr);
	xfs_buf_ioerror(bp, EFSCORRUPTED);
	return;
	}
	if (bip) {
	struct xfs_attr3_rmt_hdr *rmt;

	rmt = (struct xfs_attr3_rmt_hdr *)ptr;
	rmt->rm_lsn = cpu_to_be64(bip->bli_item.li_lsn);
	}
	xfs_update_cksum(ptr, XFS_LBSIZE(mp), XFS_ATTR3_RMT_CRC_OFF);

	len -= XFS_LBSIZE(mp);
	ptr += XFS_LBSIZE(mp);
	bno += mp->m_bsize;
	}
	ASSERT(len == 0);
	}

	const struct xfs_buf_ops xfs_attr3_rmt_buf_ops = {
	.verify_read = xfs_attr3_rmt_read_verify,
	.verify_write = xfs_attr3_rmt_write_verify,
	};

	STATIC int
	xfs_attr3_rmt_hdr_set(
	struct xfs_mount *mp,
	void *ptr,
	xfs_ino_t ino,
	uint32_t offset,
	uint32_t size,
	xfs_daddr_t bno)
	{
	struct xfs_attr3_rmt_hdr *rmt = ptr;

	if (!xfs_sb_version_hascrc(&mp->m_sb))
	return 0;

	rmt->rm_magic = cpu_to_be32(XFS_ATTR3_RMT_MAGIC);
	rmt->rm_offset = cpu_to_be32(offset);
	rmt->rm_bytes = cpu_to_be32(size);
	uuid_copy(&rmt->rm_uuid, &mp->m_sb.sb_uuid);
	rmt->rm_owner = cpu_to_be64(ino);
	rmt->rm_blkno = cpu_to_be64(bno);

	return sizeof(struct xfs_attr3_rmt_hdr);
	}

	/*
	* Helper functions to copy attribute data in and out of the one disk extents
	*/
	STATIC int
	xfs_attr_rmtval_copyout(
	struct xfs_mount *mp,
	struct xfs_buf *bp,
	xfs_ino_t ino,
	int *offset,
	int *valuelen,
	__uint8_t **dst)
	{
	char *src = bp->b_addr;
	xfs_daddr_t bno = bp->b_bn;
	int len = BBTOB(bp->b_length);

	ASSERT(len >= XFS_LBSIZE(mp));

	while (len > 0 && *valuelen > 0) {
	int hdr_size = 0;
	int byte_cnt = XFS_ATTR3_RMT_BUF_SPACE(mp, XFS_LBSIZE(mp));

	byte_cnt = min(*valuelen, byte_cnt);

	if (xfs_sb_version_hascrc(&mp->m_sb)) {
	if (!xfs_attr3_rmt_hdr_ok(mp, src, ino, *offset,
	byte_cnt, bno)) {
	xfs_alert(mp,
	"remote attribute header mismatch bno/off/len/owner (0x%llx/0x%x/Ox%x/0x%llx)",
	bno, *offset, byte_cnt, ino);
	return EFSCORRUPTED;
	}
	hdr_size = sizeof(struct xfs_attr3_rmt_hdr);
	}

	memcpy(*dst, src + hdr_size, byte_cnt);

	/* roll buffer forwards */
	len -= XFS_LBSIZE(mp);
	src += XFS_LBSIZE(mp);
	bno += mp->m_bsize;

	/* roll attribute data forwards */
	*valuelen -= byte_cnt;
	*dst += byte_cnt;
	*offset += byte_cnt;
	}
	return 0;
	}

	STATIC void
	xfs_attr_rmtval_copyin(
	struct xfs_mount *mp,
	struct xfs_buf *bp,
	xfs_ino_t ino,
	int *offset,
	int *valuelen,
	__uint8_t **src)
	{
	char *dst = bp->b_addr;
	xfs_daddr_t bno = bp->b_bn;
	int len = BBTOB(bp->b_length);

	ASSERT(len >= XFS_LBSIZE(mp));

	while (len > 0 && *valuelen > 0) {
	int hdr_size;
	int byte_cnt = XFS_ATTR3_RMT_BUF_SPACE(mp, XFS_LBSIZE(mp));

	byte_cnt = min(*valuelen, byte_cnt);
	hdr_size = xfs_attr3_rmt_hdr_set(mp, dst, ino, *offset,
	byte_cnt, bno);

	memcpy(dst + hdr_size, *src, byte_cnt);

	/*
	* If this is the last block, zero the remainder of it.
	* Check that we are actually the last block, too.
	*/
	if (byte_cnt + hdr_size < XFS_LBSIZE(mp)) {
	ASSERT(*valuelen - byte_cnt == 0);
	ASSERT(len == XFS_LBSIZE(mp));
	memset(dst + hdr_size + byte_cnt, 0,
	XFS_LBSIZE(mp) - hdr_size - byte_cnt);
	}

	/* roll buffer forwards */
	len -= XFS_LBSIZE(mp);
	dst += XFS_LBSIZE(mp);
	bno += mp->m_bsize;

	/* roll attribute data forwards */
	*valuelen -= byte_cnt;
	*src += byte_cnt;
	*offset += byte_cnt;
	}
	}

	/*
	* Read the value associated with an attribute from the out-of-line buffer
	* that we stored it in.
	*/
	int
	xfs_attr_rmtval_get(
	struct xfs_da_args *args)
	{
	struct xfs_bmbt_irec map[ATTR_RMTVALUE_MAPSIZE];
	struct xfs_mount *mp = args->dp->i_mount;
	struct xfs_buf *bp;
	xfs_dablk_t lblkno = args->rmtblkno;
	__uint8_t *dst = args->value;
	int valuelen = args->valuelen;
	int nmap;
	int error;
	int blkcnt = args->rmtblkcnt;
	int i;
	int offset = 0;

	trace_xfs_attr_rmtval_get(args);

	ASSERT(!(args->flags & ATTR_KERNOVAL));

	while (valuelen > 0) {
	nmap = ATTR_RMTVALUE_MAPSIZE;
	error = xfs_bmapi_read(args->dp, (xfs_fileoff_t)lblkno,
	blkcnt, map, &nmap,
	XFS_BMAPI_ATTRFORK);
	if (error)
	return error;
	ASSERT(nmap >= 1);

	for (i = 0; (i < nmap) && (valuelen > 0); i++) {
	xfs_daddr_t dblkno;
	int dblkcnt;

	ASSERT((map[i].br_startblock != DELAYSTARTBLOCK) &&
	(map[i].br_startblock != HOLESTARTBLOCK));
	dblkno = XFS_FSB_TO_DADDR(mp, map[i].br_startblock);
	dblkcnt = XFS_FSB_TO_BB(mp, map[i].br_blockcount);
	error = xfs_trans_read_buf(mp, NULL, mp->m_ddev_targp,
	dblkno, dblkcnt, 0, &bp,
	&xfs_attr3_rmt_buf_ops);
	if (error)
	return error;

	error = xfs_attr_rmtval_copyout(mp, bp, args->dp->i_ino,
	&offset, &valuelen,
	&dst);
	xfs_buf_relse(bp);
	if (error)
	return error;

	/* roll attribute extent map forwards */
	lblkno += map[i].br_blockcount;
	blkcnt -= map[i].br_blockcount;
	}
	}
	ASSERT(valuelen == 0);
	return 0;
	}

	/*
	* Write the value associated with an attribute into the out-of-line buffer
	* that we have defined for it.
	*/
	int
	xfs_attr_rmtval_set(
	struct xfs_da_args *args)
	{
	struct xfs_inode *dp = args->dp;
	struct xfs_mount *mp = dp->i_mount;
	struct xfs_bmbt_irec map;
	xfs_dablk_t lblkno;
	xfs_fileoff_t lfileoff = 0;
	__uint8_t *src = args->value;
	int blkcnt;
	int valuelen;
	int nmap;
	int error;
	int offset = 0;

	trace_xfs_attr_rmtval_set(args);

	/*
	* Find a "hole" in the attribute address space large enough for
	* us to drop the new attribute's value into. Because CRC enable
	* attributes have headers, we can't just do a straight byte to FSB
	* conversion and have to take the header space into account.
	*/
	blkcnt = xfs_attr3_rmt_blocks(mp, args->valuelen);
	error = xfs_bmap_first_unused(args->trans, args->dp, blkcnt, &lfileoff,
	XFS_ATTR_FORK);
	if (error)
	return error;

	args->rmtblkno = lblkno = (xfs_dablk_t)lfileoff;
	args->rmtblkcnt = blkcnt;

	/*
	* Roll through the "value", allocating blocks on disk as required.
	*/
	while (blkcnt > 0) {
	int committed;

	/*
	* Allocate a single extent, up to the size of the value.
	*/
	xfs_bmap_init(args->flist, args->firstblock);
	nmap = 1;
	error = xfs_bmapi_write(args->trans, dp, (xfs_fileoff_t)lblkno,
	blkcnt,
	XFS_BMAPI_ATTRFORK \| XFS_BMAPI_METADATA,
	args->firstblock, args->total, &map, &nmap,
	args->flist);
	if (!error) {
	error = xfs_bmap_finish(&args->trans, args->flist,
	&committed);
	}
	if (error) {
	ASSERT(committed);
	args->trans = NULL;
	xfs_bmap_cancel(args->flist);
	return(error);
	}

	/*
	* bmap_finish() may have committed the last trans and started
	* a new one. We need the inode to be in all transactions.
	*/
	if (committed)
	xfs_trans_ijoin(args->trans, dp, 0);

	ASSERT(nmap == 1);
	ASSERT((map.br_startblock != DELAYSTARTBLOCK) &&
	(map.br_startblock != HOLESTARTBLOCK));
	lblkno += map.br_blockcount;
	blkcnt -= map.br_blockcount;

	/*
	* Start the next trans in the chain.
	*/
	error = xfs_trans_roll(&args->trans, dp);
	if (error)
	return (error);
	}

	/*
	* Roll through the "value", copying the attribute value to the
	* already-allocated blocks. Blocks are written synchronously
	* so that we can know they are all on disk before we turn off
	* the INCOMPLETE flag.
	*/
	lblkno = args->rmtblkno;
	blkcnt = args->rmtblkcnt;
	valuelen = args->valuelen;
	while (valuelen > 0) {
	struct xfs_buf *bp;
	xfs_daddr_t dblkno;
	int dblkcnt;

	ASSERT(blkcnt > 0);

	xfs_bmap_init(args->flist, args->firstblock);
	nmap = 1;
	error = xfs_bmapi_read(dp, (xfs_fileoff_t)lblkno,
	blkcnt, &map, &nmap,
	XFS_BMAPI_ATTRFORK);
	if (error)
	return(error);
	ASSERT(nmap == 1);
	ASSERT((map.br_startblock != DELAYSTARTBLOCK) &&
	(map.br_startblock != HOLESTARTBLOCK));

	dblkno = XFS_FSB_TO_DADDR(mp, map.br_startblock),
	dblkcnt = XFS_FSB_TO_BB(mp, map.br_blockcount);

	bp = xfs_buf_get(mp->m_ddev_targp, dblkno, dblkcnt, 0);
	if (!bp)
	return ENOMEM;
	bp->b_ops = &xfs_attr3_rmt_buf_ops;

	xfs_attr_rmtval_copyin(mp, bp, args->dp->i_ino, &offset,
	&valuelen, &src);

	error = xfs_bwrite(bp); /* GROT: NOTE: synchronous write */
	xfs_buf_relse(bp);
	if (error)
	return error;


	/* roll attribute extent map forwards */
	lblkno += map.br_blockcount;
	blkcnt -= map.br_blockcount;
	}
	ASSERT(valuelen == 0);
	return 0;
	}

	/*
	* Remove the value associated with an attribute by deleting the
	* out-of-line buffer that it is stored on.
	*/
	int
	xfs_attr_rmtval_remove(
	struct xfs_da_args *args)
	{
	struct xfs_mount *mp = args->dp->i_mount;
	xfs_dablk_t lblkno;
	int blkcnt;
	int error;
	int done;

	trace_xfs_attr_rmtval_remove(args);

	/*
	* Roll through the "value", invalidating the attribute value's blocks.
	*/
	lblkno = args->rmtblkno;
	blkcnt = args->rmtblkcnt;
	while (blkcnt > 0) {
	struct xfs_bmbt_irec map;
	struct xfs_buf *bp;
	xfs_daddr_t dblkno;
	int dblkcnt;
	int nmap;

	/*
	* Try to remember where we decided to put the value.
	*/
	nmap = 1;
	error = xfs_bmapi_read(args->dp, (xfs_fileoff_t)lblkno,
	blkcnt, &map, &nmap, XFS_BMAPI_ATTRFORK);
	if (error)
	return(error);
	ASSERT(nmap == 1);
	ASSERT((map.br_startblock != DELAYSTARTBLOCK) &&
	(map.br_startblock != HOLESTARTBLOCK));

	dblkno = XFS_FSB_TO_DADDR(mp, map.br_startblock),
	dblkcnt = XFS_FSB_TO_BB(mp, map.br_blockcount);

	/*
	* If the "remote" value is in the cache, remove it.
	*/
	bp = xfs_incore(mp->m_ddev_targp, dblkno, dblkcnt, XBF_TRYLOCK);
	if (bp) {
	xfs_buf_stale(bp);
	xfs_buf_relse(bp);
	bp = NULL;
	}

	lblkno += map.br_blockcount;
	blkcnt -= map.br_blockcount;
	}

	/*
	* Keep de-allocating extents until the remote-value region is gone.
	*/
	lblkno = args->rmtblkno;
	blkcnt = args->rmtblkcnt;
	done = 0;
	while (!done) {
	int committed;

	xfs_bmap_init(args->flist, args->firstblock);
	error = xfs_bunmapi(args->trans, args->dp, lblkno, blkcnt,
	XFS_BMAPI_ATTRFORK \| XFS_BMAPI_METADATA,
	1, args->firstblock, args->flist,
	&done);
	if (!error) {
	error = xfs_bmap_finish(&args->trans, args->flist,
	&committed);
	}
	if (error) {
	ASSERT(committed);
	args->trans = NULL;
	xfs_bmap_cancel(args->flist);
	return error;
	}

	/*
	* bmap_finish() may have committed the last trans and started
	* a new one. We need the inode to be in all transactions.
	*/
	if (committed)
	xfs_trans_ijoin(args->trans, args->dp, 0);

	/*
	* Close out trans and start the next one in the chain.
	*/
	error = xfs_trans_roll(&args->trans, args->dp);
	if (error)
	return (error);
	}
	return(0);
	}