fs/xfs/xfs_inode_buf.c - kernel/msm-4.9 - Gitiles

 /*
  * Copyright (c) 2000-2006 Silicon Graphics, 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_format.h"
 #include "xfs_log.h"
 #include "xfs_trans.h"
 #include "xfs_sb.h"
 #include "xfs_ag.h"
 #include "xfs_mount.h"
 #include "xfs_bmap_btree.h"
 #include "xfs_ialloc_btree.h"
 #include "xfs_dinode.h"
 #include "xfs_inode.h"
 #include "xfs_error.h"
 #include "xfs_cksum.h"
 #include "xfs_icache.h"
 #include "xfs_ialloc.h"

 /*
  * Check that none of the inode's in the buffer have a next
  * unlinked field of 0.
  */
 #if defined(DEBUG)
 void
 xfs_inobp_check(
 	xfs_mount_t	*mp,
 	xfs_buf_t	*bp)
 {
 	int		i;
 	int		j;
 	xfs_dinode_t	*dip;

 	j = mp->m_inode_cluster_size >> mp->m_sb.sb_inodelog;

 	for (i = 0; i < j; i++) {
 		dip = (xfs_dinode_t *)xfs_buf_offset(bp,
 					i * mp->m_sb.sb_inodesize);
 		if (!dip->di_next_unlinked)  {
 			xfs_alert(mp,
 	"Detected bogus zero next_unlinked field in inode %d buffer 0x%llx.",
 				i, (long long)bp->b_bn);
 		}
 	}
 }
 #endif

 /*
  * If we are doing readahead on an inode buffer, we might be in log recovery
  * reading an inode allocation buffer that hasn't yet been replayed, and hence
  * has not had the inode cores stamped into it. Hence for readahead, the buffer
  * may be potentially invalid.
  *
  * If the readahead buffer is invalid, we don't want to mark it with an error,
  * but we do want to clear the DONE status of the buffer so that a followup read
  * will re-read it from disk. This will ensure that we don't get an unnecessary
  * warnings during log recovery and we don't get unnecssary panics on debug
  * kernels.
  */
 static void
 xfs_inode_buf_verify(
 	struct xfs_buf	*bp,
 	bool		readahead)
 {
 	struct xfs_mount *mp = bp->b_target->bt_mount;
 	int		i;
 	int		ni;

 	/*
 	 * Validate the magic number and version of every inode in the buffer
 	 */
 	ni = XFS_BB_TO_FSB(mp, bp->b_length) * mp->m_sb.sb_inopblock;
 	for (i = 0; i < ni; i++) {
 		int		di_ok;
 		xfs_dinode_t	*dip;

 		dip = (struct xfs_dinode *)xfs_buf_offset(bp,
 					(i << mp->m_sb.sb_inodelog));
 		di_ok = dip->di_magic == cpu_to_be16(XFS_DINODE_MAGIC) &&
 			    XFS_DINODE_GOOD_VERSION(dip->di_version);
 		if (unlikely(XFS_TEST_ERROR(!di_ok, mp,
 						XFS_ERRTAG_ITOBP_INOTOBP,
 						XFS_RANDOM_ITOBP_INOTOBP))) {
 			if (readahead) {
 				bp->b_flags &= ~XBF_DONE;
 				return;
 			}

 			xfs_buf_ioerror(bp, EFSCORRUPTED);
 			XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_HIGH,
 					     mp, dip);
 #ifdef DEBUG
 			xfs_alert(mp,
 				"bad inode magic/vsn daddr %lld #%d (magic=%x)",
 				(unsigned long long)bp->b_bn, i,
 				be16_to_cpu(dip->di_magic));
 #endif
 		}
 	}
 	xfs_inobp_check(mp, bp);
 }


 static void
 xfs_inode_buf_read_verify(
 	struct xfs_buf	*bp)
 {
 	xfs_inode_buf_verify(bp, false);
 }

 static void
 xfs_inode_buf_readahead_verify(
 	struct xfs_buf	*bp)
 {
 	xfs_inode_buf_verify(bp, true);
 }

 static void
 xfs_inode_buf_write_verify(
 	struct xfs_buf	*bp)
 {
 	xfs_inode_buf_verify(bp, false);
 }

 const struct xfs_buf_ops xfs_inode_buf_ops = {
 	.verify_read = xfs_inode_buf_read_verify,
 	.verify_write = xfs_inode_buf_write_verify,
 };

 const struct xfs_buf_ops xfs_inode_buf_ra_ops = {
 	.verify_read = xfs_inode_buf_readahead_verify,
 	.verify_write = xfs_inode_buf_write_verify,
 };


 /*
  * This routine is called to map an inode to the buffer containing the on-disk
  * version of the inode.  It returns a pointer to the buffer containing the
  * on-disk inode in the bpp parameter, and in the dipp parameter it returns a
  * pointer to the on-disk inode within that buffer.
  *
  * If a non-zero error is returned, then the contents of bpp and dipp are
  * undefined.
  */
 int
 xfs_imap_to_bp(
 	struct xfs_mount	*mp,
 	struct xfs_trans	*tp,
 	struct xfs_imap		*imap,
 	struct xfs_dinode       **dipp,
 	struct xfs_buf		**bpp,
 	uint			buf_flags,
 	uint			iget_flags)
 {
 	struct xfs_buf		*bp;
 	int			error;

 	buf_flags |= XBF_UNMAPPED;
 	error = xfs_trans_read_buf(mp, tp, mp->m_ddev_targp, imap->im_blkno,
 				   (int)imap->im_len, buf_flags, &bp,
 				   &xfs_inode_buf_ops);
 	if (error) {
 		if (error == EAGAIN) {
 			ASSERT(buf_flags & XBF_TRYLOCK);
 			return error;
 		}

 		if (error == EFSCORRUPTED &&
 		    (iget_flags & XFS_IGET_UNTRUSTED))
 			return XFS_ERROR(EINVAL);

 		xfs_warn(mp, "%s: xfs_trans_read_buf() returned error %d.",
 			__func__, error);
 		return error;
 	}

 	*bpp = bp;
 	*dipp = (struct xfs_dinode *)xfs_buf_offset(bp, imap->im_boffset);
 	return 0;
 }

 void
 xfs_dinode_from_disk(
 	xfs_icdinode_t		*to,
 	xfs_dinode_t		*from)
 {
 	to->di_magic = be16_to_cpu(from->di_magic);
 	to->di_mode = be16_to_cpu(from->di_mode);
 	to->di_version = from ->di_version;
 	to->di_format = from->di_format;
 	to->di_onlink = be16_to_cpu(from->di_onlink);
 	to->di_uid = be32_to_cpu(from->di_uid);
 	to->di_gid = be32_to_cpu(from->di_gid);
 	to->di_nlink = be32_to_cpu(from->di_nlink);
 	to->di_projid_lo = be16_to_cpu(from->di_projid_lo);
 	to->di_projid_hi = be16_to_cpu(from->di_projid_hi);
 	memcpy(to->di_pad, from->di_pad, sizeof(to->di_pad));
 	to->di_flushiter = be16_to_cpu(from->di_flushiter);
 	to->di_atime.t_sec = be32_to_cpu(from->di_atime.t_sec);
 	to->di_atime.t_nsec = be32_to_cpu(from->di_atime.t_nsec);
 	to->di_mtime.t_sec = be32_to_cpu(from->di_mtime.t_sec);
 	to->di_mtime.t_nsec = be32_to_cpu(from->di_mtime.t_nsec);
 	to->di_ctime.t_sec = be32_to_cpu(from->di_ctime.t_sec);
 	to->di_ctime.t_nsec = be32_to_cpu(from->di_ctime.t_nsec);
 	to->di_size = be64_to_cpu(from->di_size);
 	to->di_nblocks = be64_to_cpu(from->di_nblocks);
 	to->di_extsize = be32_to_cpu(from->di_extsize);
 	to->di_nextents = be32_to_cpu(from->di_nextents);
 	to->di_anextents = be16_to_cpu(from->di_anextents);
 	to->di_forkoff = from->di_forkoff;
 	to->di_aformat	= from->di_aformat;
 	to->di_dmevmask	= be32_to_cpu(from->di_dmevmask);
 	to->di_dmstate	= be16_to_cpu(from->di_dmstate);
 	to->di_flags	= be16_to_cpu(from->di_flags);
 	to->di_gen	= be32_to_cpu(from->di_gen);

 	if (to->di_version == 3) {
 		to->di_changecount = be64_to_cpu(from->di_changecount);
 		to->di_crtime.t_sec = be32_to_cpu(from->di_crtime.t_sec);
 		to->di_crtime.t_nsec = be32_to_cpu(from->di_crtime.t_nsec);
 		to->di_flags2 = be64_to_cpu(from->di_flags2);
 		to->di_ino = be64_to_cpu(from->di_ino);
 		to->di_lsn = be64_to_cpu(from->di_lsn);
 		memcpy(to->di_pad2, from->di_pad2, sizeof(to->di_pad2));
 		uuid_copy(&to->di_uuid, &from->di_uuid);
 	}
 }

 void
 xfs_dinode_to_disk(
 	xfs_dinode_t		*to,
 	xfs_icdinode_t		*from)
 {
 	to->di_magic = cpu_to_be16(from->di_magic);
 	to->di_mode = cpu_to_be16(from->di_mode);
 	to->di_version = from ->di_version;
 	to->di_format = from->di_format;
 	to->di_onlink = cpu_to_be16(from->di_onlink);
 	to->di_uid = cpu_to_be32(from->di_uid);
 	to->di_gid = cpu_to_be32(from->di_gid);
 	to->di_nlink = cpu_to_be32(from->di_nlink);
 	to->di_projid_lo = cpu_to_be16(from->di_projid_lo);
 	to->di_projid_hi = cpu_to_be16(from->di_projid_hi);
 	memcpy(to->di_pad, from->di_pad, sizeof(to->di_pad));
 	to->di_atime.t_sec = cpu_to_be32(from->di_atime.t_sec);
 	to->di_atime.t_nsec = cpu_to_be32(from->di_atime.t_nsec);
 	to->di_mtime.t_sec = cpu_to_be32(from->di_mtime.t_sec);
 	to->di_mtime.t_nsec = cpu_to_be32(from->di_mtime.t_nsec);
 	to->di_ctime.t_sec = cpu_to_be32(from->di_ctime.t_sec);
 	to->di_ctime.t_nsec = cpu_to_be32(from->di_ctime.t_nsec);
 	to->di_size = cpu_to_be64(from->di_size);
 	to->di_nblocks = cpu_to_be64(from->di_nblocks);
 	to->di_extsize = cpu_to_be32(from->di_extsize);
 	to->di_nextents = cpu_to_be32(from->di_nextents);
 	to->di_anextents = cpu_to_be16(from->di_anextents);
 	to->di_forkoff = from->di_forkoff;
 	to->di_aformat = from->di_aformat;
 	to->di_dmevmask = cpu_to_be32(from->di_dmevmask);
 	to->di_dmstate = cpu_to_be16(from->di_dmstate);
 	to->di_flags = cpu_to_be16(from->di_flags);
 	to->di_gen = cpu_to_be32(from->di_gen);

 	if (from->di_version == 3) {
 		to->di_changecount = cpu_to_be64(from->di_changecount);
 		to->di_crtime.t_sec = cpu_to_be32(from->di_crtime.t_sec);
 		to->di_crtime.t_nsec = cpu_to_be32(from->di_crtime.t_nsec);
 		to->di_flags2 = cpu_to_be64(from->di_flags2);
 		to->di_ino = cpu_to_be64(from->di_ino);
 		to->di_lsn = cpu_to_be64(from->di_lsn);
 		memcpy(to->di_pad2, from->di_pad2, sizeof(to->di_pad2));
 		uuid_copy(&to->di_uuid, &from->di_uuid);
 		to->di_flushiter = 0;
 	} else {
 		to->di_flushiter = cpu_to_be16(from->di_flushiter);
 	}
 }

 static bool
 xfs_dinode_verify(
 	struct xfs_mount	*mp,
 	struct xfs_inode	*ip,
 	struct xfs_dinode	*dip)
 {
 	if (dip->di_magic != cpu_to_be16(XFS_DINODE_MAGIC))
 		return false;

 	/* only version 3 or greater inodes are extensively verified here */
 	if (dip->di_version < 3)
 		return true;

 	if (!xfs_sb_version_hascrc(&mp->m_sb))
 		return false;
 	if (!xfs_verify_cksum((char *)dip, mp->m_sb.sb_inodesize,
 			      offsetof(struct xfs_dinode, di_crc)))
 		return false;
 	if (be64_to_cpu(dip->di_ino) != ip->i_ino)
 		return false;
 	if (!uuid_equal(&dip->di_uuid, &mp->m_sb.sb_uuid))
 		return false;
 	return true;
 }

 void
 xfs_dinode_calc_crc(
 	struct xfs_mount	*mp,
 	struct xfs_dinode	*dip)
 {
 	__uint32_t		crc;

 	if (dip->di_version < 3)
 		return;

 	ASSERT(xfs_sb_version_hascrc(&mp->m_sb));
 	crc = xfs_start_cksum((char *)dip, mp->m_sb.sb_inodesize,
 			      offsetof(struct xfs_dinode, di_crc));
 	dip->di_crc = xfs_end_cksum(crc);
 }

 /*
  * Read the disk inode attributes into the in-core inode structure.
  *
  * For version 5 superblocks, if we are initialising a new inode and we are not
  * utilising the XFS_MOUNT_IKEEP inode cluster mode, we can simple build the new
  * inode core with a random generation number. If we are keeping inodes around,
  * we need to read the inode cluster to get the existing generation number off
  * disk. Further, if we are using version 4 superblocks (i.e. v1/v2 inode
  * format) then log recovery is dependent on the di_flushiter field being
  * initialised from the current on-disk value and hence we must also read the
  * inode off disk.
  */
 int
 xfs_iread(
 	xfs_mount_t	*mp,
 	xfs_trans_t	*tp,
 	xfs_inode_t	*ip,
 	uint		iget_flags)
 {
 	xfs_buf_t	*bp;
 	xfs_dinode_t	*dip;
 	int		error;

 	/*
 	 * Fill in the location information in the in-core inode.
 	 */
 	error = xfs_imap(mp, tp, ip->i_ino, &ip->i_imap, iget_flags);
 	if (error)
 		return error;

 	/* shortcut IO on inode allocation if possible */
 	if ((iget_flags & XFS_IGET_CREATE) &&
 	    xfs_sb_version_hascrc(&mp->m_sb) &&
 	    !(mp->m_flags & XFS_MOUNT_IKEEP)) {
 		/* initialise the on-disk inode core */
 		memset(&ip->i_d, 0, sizeof(ip->i_d));
 		ip->i_d.di_magic = XFS_DINODE_MAGIC;
 		ip->i_d.di_gen = prandom_u32();
 		if (xfs_sb_version_hascrc(&mp->m_sb)) {
 			ip->i_d.di_version = 3;
 			ip->i_d.di_ino = ip->i_ino;
 			uuid_copy(&ip->i_d.di_uuid, &mp->m_sb.sb_uuid);
 		} else
 			ip->i_d.di_version = 2;
 		return 0;
 	}

 	/*
 	 * Get pointers to the on-disk inode and the buffer containing it.
 	 */
 	error = xfs_imap_to_bp(mp, tp, &ip->i_imap, &dip, &bp, 0, iget_flags);
 	if (error)
 		return error;

 	/* even unallocated inodes are verified */
 	if (!xfs_dinode_verify(mp, ip, dip)) {
 		xfs_alert(mp, "%s: validation failed for inode %lld failed",
 				__func__, ip->i_ino);

 		XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp, dip);
 		error = XFS_ERROR(EFSCORRUPTED);
 		goto out_brelse;
 	}

 	/*
 	 * If the on-disk inode is already linked to a directory
 	 * entry, copy all of the inode into the in-core inode.
 	 * xfs_iformat_fork() handles copying in the inode format
 	 * specific information.
 	 * Otherwise, just get the truly permanent information.
 	 */
 	if (dip->di_mode) {
 		xfs_dinode_from_disk(&ip->i_d, dip);
 		error = xfs_iformat_fork(ip, dip);
 		if (error)  {
 #ifdef DEBUG
 			xfs_alert(mp, "%s: xfs_iformat() returned error %d",
 				__func__, error);
 #endif /* DEBUG */
 			goto out_brelse;
 		}
 	} else {
 		/*
 		 * Partial initialisation of the in-core inode. Just the bits
 		 * that xfs_ialloc won't overwrite or relies on being correct.
 		 */
 		ip->i_d.di_magic = be16_to_cpu(dip->di_magic);
 		ip->i_d.di_version = dip->di_version;
 		ip->i_d.di_gen = be32_to_cpu(dip->di_gen);
 		ip->i_d.di_flushiter = be16_to_cpu(dip->di_flushiter);

 		if (dip->di_version == 3) {
 			ip->i_d.di_ino = be64_to_cpu(dip->di_ino);
 			uuid_copy(&ip->i_d.di_uuid, &dip->di_uuid);
 		}

 		/*
 		 * Make sure to pull in the mode here as well in
 		 * case the inode is released without being used.
 		 * This ensures that xfs_inactive() will see that
 		 * the inode is already free and not try to mess
 		 * with the uninitialized part of it.
 		 */
 		ip->i_d.di_mode = 0;
 	}

 	/*
 	 * The inode format changed when we moved the link count and
 	 * made it 32 bits long.  If this is an old format inode,
 	 * convert it in memory to look like a new one.  If it gets
 	 * flushed to disk we will convert back before flushing or
 	 * logging it.  We zero out the new projid field and the old link
 	 * count field.  We'll handle clearing the pad field (the remains
 	 * of the old uuid field) when we actually convert the inode to
 	 * the new format. We don't change the version number so that we
 	 * can distinguish this from a real new format inode.
 	 */
 	if (ip->i_d.di_version == 1) {
 		ip->i_d.di_nlink = ip->i_d.di_onlink;
 		ip->i_d.di_onlink = 0;
 		xfs_set_projid(ip, 0);
 	}

 	ip->i_delayed_blks = 0;

 	/*
 	 * Mark the buffer containing the inode as something to keep
 	 * around for a while.  This helps to keep recently accessed
 	 * meta-data in-core longer.
 	 */
 	xfs_buf_set_ref(bp, XFS_INO_REF);

 	/*
 	 * Use xfs_trans_brelse() to release the buffer containing the on-disk
 	 * inode, because it was acquired with xfs_trans_read_buf() in
 	 * xfs_imap_to_bp() above.  If tp is NULL, this is just a normal
 	 * brelse().  If we're within a transaction, then xfs_trans_brelse()
 	 * will only release the buffer if it is not dirty within the
 	 * transaction.  It will be OK to release the buffer in this case,
 	 * because inodes on disk are never destroyed and we will be locking the
 	 * new in-core inode before putting it in the cache where other
 	 * processes can find it.  Thus we don't have to worry about the inode
 	 * being changed just because we released the buffer.
 	 */
  out_brelse:
 	xfs_trans_brelse(tp, bp);
 	return error;
 }
	/*
	* Copyright (c) 2000-2006 Silicon Graphics, 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_format.h"
	#include "xfs_log.h"
	#include "xfs_trans.h"
	#include "xfs_sb.h"
	#include "xfs_ag.h"
	#include "xfs_mount.h"
	#include "xfs_bmap_btree.h"
	#include "xfs_ialloc_btree.h"
	#include "xfs_dinode.h"
	#include "xfs_inode.h"
	#include "xfs_error.h"
	#include "xfs_cksum.h"
	#include "xfs_icache.h"
	#include "xfs_ialloc.h"

	/*
	* Check that none of the inode's in the buffer have a next
	* unlinked field of 0.
	*/
	#if defined(DEBUG)
	void
	xfs_inobp_check(
	xfs_mount_t *mp,
	xfs_buf_t *bp)
	{
	int i;
	int j;
	xfs_dinode_t *dip;

	j = mp->m_inode_cluster_size >> mp->m_sb.sb_inodelog;

	for (i = 0; i < j; i++) {
	dip = (xfs_dinode_t *)xfs_buf_offset(bp,
	i * mp->m_sb.sb_inodesize);
	if (!dip->di_next_unlinked) {
	xfs_alert(mp,
	"Detected bogus zero next_unlinked field in inode %d buffer 0x%llx.",
	i, (long long)bp->b_bn);
	}
	}
	}
	#endif

	/*
	* If we are doing readahead on an inode buffer, we might be in log recovery
	* reading an inode allocation buffer that hasn't yet been replayed, and hence
	* has not had the inode cores stamped into it. Hence for readahead, the buffer
	* may be potentially invalid.
	*
	* If the readahead buffer is invalid, we don't want to mark it with an error,
	* but we do want to clear the DONE status of the buffer so that a followup read
	* will re-read it from disk. This will ensure that we don't get an unnecessary
	* warnings during log recovery and we don't get unnecssary panics on debug
	* kernels.
	*/
	static void
	xfs_inode_buf_verify(
	struct xfs_buf *bp,
	bool readahead)
	{
	struct xfs_mount *mp = bp->b_target->bt_mount;
	int i;
	int ni;

	/*
	* Validate the magic number and version of every inode in the buffer
	*/
	ni = XFS_BB_TO_FSB(mp, bp->b_length) * mp->m_sb.sb_inopblock;
	for (i = 0; i < ni; i++) {
	int di_ok;
	xfs_dinode_t *dip;

	dip = (struct xfs_dinode *)xfs_buf_offset(bp,
	(i << mp->m_sb.sb_inodelog));
	di_ok = dip->di_magic == cpu_to_be16(XFS_DINODE_MAGIC) &&
	XFS_DINODE_GOOD_VERSION(dip->di_version);
	if (unlikely(XFS_TEST_ERROR(!di_ok, mp,
	XFS_ERRTAG_ITOBP_INOTOBP,
	XFS_RANDOM_ITOBP_INOTOBP))) {
	if (readahead) {
	bp->b_flags &= ~XBF_DONE;
	return;
	}

	xfs_buf_ioerror(bp, EFSCORRUPTED);
	XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_HIGH,
	mp, dip);
	#ifdef DEBUG
	xfs_alert(mp,
	"bad inode magic/vsn daddr %lld #%d (magic=%x)",
	(unsigned long long)bp->b_bn, i,
	be16_to_cpu(dip->di_magic));
	#endif
	}
	}
	xfs_inobp_check(mp, bp);
	}


	static void
	xfs_inode_buf_read_verify(
	struct xfs_buf *bp)
	{
	xfs_inode_buf_verify(bp, false);
	}

	static void
	xfs_inode_buf_readahead_verify(
	struct xfs_buf *bp)
	{
	xfs_inode_buf_verify(bp, true);
	}

	static void
	xfs_inode_buf_write_verify(
	struct xfs_buf *bp)
	{
	xfs_inode_buf_verify(bp, false);
	}

	const struct xfs_buf_ops xfs_inode_buf_ops = {
	.verify_read = xfs_inode_buf_read_verify,
	.verify_write = xfs_inode_buf_write_verify,
	};

	const struct xfs_buf_ops xfs_inode_buf_ra_ops = {
	.verify_read = xfs_inode_buf_readahead_verify,
	.verify_write = xfs_inode_buf_write_verify,
	};


	/*
	* This routine is called to map an inode to the buffer containing the on-disk
	* version of the inode. It returns a pointer to the buffer containing the
	* on-disk inode in the bpp parameter, and in the dipp parameter it returns a
	* pointer to the on-disk inode within that buffer.
	*
	* If a non-zero error is returned, then the contents of bpp and dipp are
	* undefined.
	*/
	int
	xfs_imap_to_bp(
	struct xfs_mount *mp,
	struct xfs_trans *tp,
	struct xfs_imap *imap,
	struct xfs_dinode **dipp,
	struct xfs_buf **bpp,
	uint buf_flags,
	uint iget_flags)
	{
	struct xfs_buf *bp;
	int error;

	buf_flags \|= XBF_UNMAPPED;
	error = xfs_trans_read_buf(mp, tp, mp->m_ddev_targp, imap->im_blkno,
	(int)imap->im_len, buf_flags, &bp,
	&xfs_inode_buf_ops);
	if (error) {
	if (error == EAGAIN) {
	ASSERT(buf_flags & XBF_TRYLOCK);
	return error;
	}

	if (error == EFSCORRUPTED &&
	(iget_flags & XFS_IGET_UNTRUSTED))
	return XFS_ERROR(EINVAL);

	xfs_warn(mp, "%s: xfs_trans_read_buf() returned error %d.",
	__func__, error);
	return error;
	}

	*bpp = bp;
	dipp = (struct xfs_dinode )xfs_buf_offset(bp, imap->im_boffset);
	return 0;
	}

	void
	xfs_dinode_from_disk(
	xfs_icdinode_t *to,
	xfs_dinode_t *from)
	{
	to->di_magic = be16_to_cpu(from->di_magic);
	to->di_mode = be16_to_cpu(from->di_mode);
	to->di_version = from ->di_version;
	to->di_format = from->di_format;
	to->di_onlink = be16_to_cpu(from->di_onlink);
	to->di_uid = be32_to_cpu(from->di_uid);
	to->di_gid = be32_to_cpu(from->di_gid);
	to->di_nlink = be32_to_cpu(from->di_nlink);
	to->di_projid_lo = be16_to_cpu(from->di_projid_lo);
	to->di_projid_hi = be16_to_cpu(from->di_projid_hi);
	memcpy(to->di_pad, from->di_pad, sizeof(to->di_pad));
	to->di_flushiter = be16_to_cpu(from->di_flushiter);
	to->di_atime.t_sec = be32_to_cpu(from->di_atime.t_sec);
	to->di_atime.t_nsec = be32_to_cpu(from->di_atime.t_nsec);
	to->di_mtime.t_sec = be32_to_cpu(from->di_mtime.t_sec);
	to->di_mtime.t_nsec = be32_to_cpu(from->di_mtime.t_nsec);
	to->di_ctime.t_sec = be32_to_cpu(from->di_ctime.t_sec);
	to->di_ctime.t_nsec = be32_to_cpu(from->di_ctime.t_nsec);
	to->di_size = be64_to_cpu(from->di_size);
	to->di_nblocks = be64_to_cpu(from->di_nblocks);
	to->di_extsize = be32_to_cpu(from->di_extsize);
	to->di_nextents = be32_to_cpu(from->di_nextents);
	to->di_anextents = be16_to_cpu(from->di_anextents);
	to->di_forkoff = from->di_forkoff;
	to->di_aformat = from->di_aformat;
	to->di_dmevmask = be32_to_cpu(from->di_dmevmask);
	to->di_dmstate = be16_to_cpu(from->di_dmstate);
	to->di_flags = be16_to_cpu(from->di_flags);
	to->di_gen = be32_to_cpu(from->di_gen);

	if (to->di_version == 3) {
	to->di_changecount = be64_to_cpu(from->di_changecount);
	to->di_crtime.t_sec = be32_to_cpu(from->di_crtime.t_sec);
	to->di_crtime.t_nsec = be32_to_cpu(from->di_crtime.t_nsec);
	to->di_flags2 = be64_to_cpu(from->di_flags2);
	to->di_ino = be64_to_cpu(from->di_ino);
	to->di_lsn = be64_to_cpu(from->di_lsn);
	memcpy(to->di_pad2, from->di_pad2, sizeof(to->di_pad2));
	uuid_copy(&to->di_uuid, &from->di_uuid);
	}
	}

	void
	xfs_dinode_to_disk(
	xfs_dinode_t *to,
	xfs_icdinode_t *from)
	{
	to->di_magic = cpu_to_be16(from->di_magic);
	to->di_mode = cpu_to_be16(from->di_mode);
	to->di_version = from ->di_version;
	to->di_format = from->di_format;
	to->di_onlink = cpu_to_be16(from->di_onlink);
	to->di_uid = cpu_to_be32(from->di_uid);
	to->di_gid = cpu_to_be32(from->di_gid);
	to->di_nlink = cpu_to_be32(from->di_nlink);
	to->di_projid_lo = cpu_to_be16(from->di_projid_lo);
	to->di_projid_hi = cpu_to_be16(from->di_projid_hi);
	memcpy(to->di_pad, from->di_pad, sizeof(to->di_pad));
	to->di_atime.t_sec = cpu_to_be32(from->di_atime.t_sec);
	to->di_atime.t_nsec = cpu_to_be32(from->di_atime.t_nsec);
	to->di_mtime.t_sec = cpu_to_be32(from->di_mtime.t_sec);
	to->di_mtime.t_nsec = cpu_to_be32(from->di_mtime.t_nsec);
	to->di_ctime.t_sec = cpu_to_be32(from->di_ctime.t_sec);
	to->di_ctime.t_nsec = cpu_to_be32(from->di_ctime.t_nsec);
	to->di_size = cpu_to_be64(from->di_size);
	to->di_nblocks = cpu_to_be64(from->di_nblocks);
	to->di_extsize = cpu_to_be32(from->di_extsize);
	to->di_nextents = cpu_to_be32(from->di_nextents);
	to->di_anextents = cpu_to_be16(from->di_anextents);
	to->di_forkoff = from->di_forkoff;
	to->di_aformat = from->di_aformat;
	to->di_dmevmask = cpu_to_be32(from->di_dmevmask);
	to->di_dmstate = cpu_to_be16(from->di_dmstate);
	to->di_flags = cpu_to_be16(from->di_flags);
	to->di_gen = cpu_to_be32(from->di_gen);

	if (from->di_version == 3) {
	to->di_changecount = cpu_to_be64(from->di_changecount);
	to->di_crtime.t_sec = cpu_to_be32(from->di_crtime.t_sec);
	to->di_crtime.t_nsec = cpu_to_be32(from->di_crtime.t_nsec);
	to->di_flags2 = cpu_to_be64(from->di_flags2);
	to->di_ino = cpu_to_be64(from->di_ino);
	to->di_lsn = cpu_to_be64(from->di_lsn);
	memcpy(to->di_pad2, from->di_pad2, sizeof(to->di_pad2));
	uuid_copy(&to->di_uuid, &from->di_uuid);
	to->di_flushiter = 0;
	} else {
	to->di_flushiter = cpu_to_be16(from->di_flushiter);
	}
	}

	static bool
	xfs_dinode_verify(
	struct xfs_mount *mp,
	struct xfs_inode *ip,
	struct xfs_dinode *dip)
	{
	if (dip->di_magic != cpu_to_be16(XFS_DINODE_MAGIC))
	return false;

	/* only version 3 or greater inodes are extensively verified here */
	if (dip->di_version < 3)
	return true;

	if (!xfs_sb_version_hascrc(&mp->m_sb))
	return false;
	if (!xfs_verify_cksum((char *)dip, mp->m_sb.sb_inodesize,
	offsetof(struct xfs_dinode, di_crc)))
	return false;
	if (be64_to_cpu(dip->di_ino) != ip->i_ino)
	return false;
	if (!uuid_equal(&dip->di_uuid, &mp->m_sb.sb_uuid))
	return false;
	return true;
	}

	void
	xfs_dinode_calc_crc(
	struct xfs_mount *mp,
	struct xfs_dinode *dip)
	{
	__uint32_t crc;

	if (dip->di_version < 3)
	return;

	ASSERT(xfs_sb_version_hascrc(&mp->m_sb));
	crc = xfs_start_cksum((char *)dip, mp->m_sb.sb_inodesize,
	offsetof(struct xfs_dinode, di_crc));
	dip->di_crc = xfs_end_cksum(crc);
	}

	/*
	* Read the disk inode attributes into the in-core inode structure.
	*
	* For version 5 superblocks, if we are initialising a new inode and we are not
	* utilising the XFS_MOUNT_IKEEP inode cluster mode, we can simple build the new
	* inode core with a random generation number. If we are keeping inodes around,
	* we need to read the inode cluster to get the existing generation number off
	* disk. Further, if we are using version 4 superblocks (i.e. v1/v2 inode
	* format) then log recovery is dependent on the di_flushiter field being
	* initialised from the current on-disk value and hence we must also read the
	* inode off disk.
	*/
	int
	xfs_iread(
	xfs_mount_t *mp,
	xfs_trans_t *tp,
	xfs_inode_t *ip,
	uint iget_flags)
	{
	xfs_buf_t *bp;
	xfs_dinode_t *dip;
	int error;

	/*
	* Fill in the location information in the in-core inode.
	*/
	error = xfs_imap(mp, tp, ip->i_ino, &ip->i_imap, iget_flags);
	if (error)
	return error;

	/* shortcut IO on inode allocation if possible */
	if ((iget_flags & XFS_IGET_CREATE) &&
	xfs_sb_version_hascrc(&mp->m_sb) &&
	!(mp->m_flags & XFS_MOUNT_IKEEP)) {
	/* initialise the on-disk inode core */
	memset(&ip->i_d, 0, sizeof(ip->i_d));
	ip->i_d.di_magic = XFS_DINODE_MAGIC;
	ip->i_d.di_gen = prandom_u32();
	if (xfs_sb_version_hascrc(&mp->m_sb)) {
	ip->i_d.di_version = 3;
	ip->i_d.di_ino = ip->i_ino;
	uuid_copy(&ip->i_d.di_uuid, &mp->m_sb.sb_uuid);
	} else
	ip->i_d.di_version = 2;
	return 0;
	}

	/*
	* Get pointers to the on-disk inode and the buffer containing it.
	*/
	error = xfs_imap_to_bp(mp, tp, &ip->i_imap, &dip, &bp, 0, iget_flags);
	if (error)
	return error;

	/* even unallocated inodes are verified */
	if (!xfs_dinode_verify(mp, ip, dip)) {
	xfs_alert(mp, "%s: validation failed for inode %lld failed",
	__func__, ip->i_ino);

	XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp, dip);
	error = XFS_ERROR(EFSCORRUPTED);
	goto out_brelse;
	}

	/*
	* If the on-disk inode is already linked to a directory
	* entry, copy all of the inode into the in-core inode.
	* xfs_iformat_fork() handles copying in the inode format
	* specific information.
	* Otherwise, just get the truly permanent information.
	*/
	if (dip->di_mode) {
	xfs_dinode_from_disk(&ip->i_d, dip);
	error = xfs_iformat_fork(ip, dip);
	if (error) {
	#ifdef DEBUG
	xfs_alert(mp, "%s: xfs_iformat() returned error %d",
	__func__, error);
	#endif /* DEBUG */
	goto out_brelse;
	}
	} else {
	/*
	* Partial initialisation of the in-core inode. Just the bits
	* that xfs_ialloc won't overwrite or relies on being correct.
	*/
	ip->i_d.di_magic = be16_to_cpu(dip->di_magic);
	ip->i_d.di_version = dip->di_version;
	ip->i_d.di_gen = be32_to_cpu(dip->di_gen);
	ip->i_d.di_flushiter = be16_to_cpu(dip->di_flushiter);

	if (dip->di_version == 3) {
	ip->i_d.di_ino = be64_to_cpu(dip->di_ino);
	uuid_copy(&ip->i_d.di_uuid, &dip->di_uuid);
	}

	/*
	* Make sure to pull in the mode here as well in
	* case the inode is released without being used.
	* This ensures that xfs_inactive() will see that
	* the inode is already free and not try to mess
	* with the uninitialized part of it.
	*/
	ip->i_d.di_mode = 0;
	}

	/*
	* The inode format changed when we moved the link count and
	* made it 32 bits long. If this is an old format inode,
	* convert it in memory to look like a new one. If it gets
	* flushed to disk we will convert back before flushing or
	* logging it. We zero out the new projid field and the old link
	* count field. We'll handle clearing the pad field (the remains
	* of the old uuid field) when we actually convert the inode to
	* the new format. We don't change the version number so that we
	* can distinguish this from a real new format inode.
	*/
	if (ip->i_d.di_version == 1) {
	ip->i_d.di_nlink = ip->i_d.di_onlink;
	ip->i_d.di_onlink = 0;
	xfs_set_projid(ip, 0);
	}

	ip->i_delayed_blks = 0;

	/*
	* Mark the buffer containing the inode as something to keep
	* around for a while. This helps to keep recently accessed
	* meta-data in-core longer.
	*/
	xfs_buf_set_ref(bp, XFS_INO_REF);

	/*
	* Use xfs_trans_brelse() to release the buffer containing the on-disk
	* inode, because it was acquired with xfs_trans_read_buf() in
	* xfs_imap_to_bp() above. If tp is NULL, this is just a normal
	* brelse(). If we're within a transaction, then xfs_trans_brelse()
	* will only release the buffer if it is not dirty within the
	* transaction. It will be OK to release the buffer in this case,
	* because inodes on disk are never destroyed and we will be locking the
	* new in-core inode before putting it in the cache where other
	* processes can find it. Thus we don't have to worry about the inode
	* being changed just because we released the buffer.
	*/
	out_brelse:
	xfs_trans_brelse(tp, bp);
	return error;
	}