Пример #1
0
/*
 * Roll a transaction, keeping the AG headers locked and reinitializing
 * the btree cursors.
 */
int
xrep_roll_ag_trans(
	struct xfs_scrub	*sc)
{
	int			error;

	/* Keep the AG header buffers locked so we can keep going. */
	if (sc->sa.agi_bp)
		xfs_trans_bhold(sc->tp, sc->sa.agi_bp);
	if (sc->sa.agf_bp)
		xfs_trans_bhold(sc->tp, sc->sa.agf_bp);
	if (sc->sa.agfl_bp)
		xfs_trans_bhold(sc->tp, sc->sa.agfl_bp);

	/*
	 * Roll the transaction.  We still own the buffer and the buffer lock
	 * regardless of whether or not the roll succeeds.  If the roll fails,
	 * the buffers will be released during teardown on our way out of the
	 * kernel.  If it succeeds, we join them to the new transaction and
	 * move on.
	 */
	error = xfs_trans_roll(&sc->tp);
	if (error)
		return error;

	/* Join AG headers to the new transaction. */
	if (sc->sa.agi_bp)
		xfs_trans_bjoin(sc->tp, sc->sa.agi_bp);
	if (sc->sa.agf_bp)
		xfs_trans_bjoin(sc->tp, sc->sa.agf_bp);
	if (sc->sa.agfl_bp)
		xfs_trans_bjoin(sc->tp, sc->sa.agfl_bp);

	return 0;
}
Пример #2
0
/*
 * Hold dabuf at transaction commit.
 * 
 * Originally from xfs_da_btree.c in the kernel, but only used
 * in userspace so it now resides here.
 */
void
libxfs_da_bhold(xfs_trans_t *tp, xfs_dabuf_t *dabuf)
{
	int	i;

	for (i = 0; i < dabuf->nbuf; i++)
		xfs_trans_bhold(tp, dabuf->bps[i]);
}
Пример #3
0
/*
 * Wrapper around call to libxfs_ialloc. Takes care of committing and
 * allocating a new transaction as needed.
 *
 * Originally there were two copies of this code - one in mkfs, the
 * other in repair - now there is just the one.
 */
int
libxfs_inode_alloc(
	xfs_trans_t	**tp,
	xfs_inode_t	*pip,
	mode_t		mode,
	nlink_t		nlink,
	xfs_dev_t	rdev,
	struct cred	*cr,
	struct fsxattr	*fsx,
	xfs_inode_t	**ipp)
{
	xfs_buf_t	*ialloc_context;
	xfs_inode_t	*ip;
	int		error;

	ialloc_context = (xfs_buf_t *)0;
	error = libxfs_ialloc(*tp, pip, mode, nlink, rdev, cr, fsx,
			   1, &ialloc_context, &ip);
	if (error) {
		*ipp = NULL;
		return error;
	}
	if (!ialloc_context && !ip) {
		*ipp = NULL;
		return -ENOSPC;
	}

	if (ialloc_context) {

		xfs_trans_bhold(*tp, ialloc_context);

		error = xfs_trans_roll(tp, NULL);
		if (error) {
			fprintf(stderr, _("%s: cannot duplicate transaction: %s\n"),
				progname, strerror(error));
			exit(1);
		}
		xfs_trans_bjoin(*tp, ialloc_context);
		error = libxfs_ialloc(*tp, pip, mode, nlink, rdev, cr,
				   fsx, 1, &ialloc_context, &ip);
		if (!ip)
			error = -ENOSPC;
		if (error)
			return error;
	}

	*ipp = ip;
	return error;
}
Пример #4
0
/*
 * Wrapper around call to libxfs_ialloc. Takes care of committing and
 * allocating a new transaction as needed.
 *
 * Originally there were two copies of this code - one in mkfs, the
 * other in repair - now there is just the one.
 */
int
libxfs_inode_alloc(
	xfs_trans_t     **tp,
	xfs_inode_t     *pip,
	mode_t		mode,
	ushort		nlink,
	dev_t		rdev,
	cred_t		*cr,
	xfs_inode_t	**ipp)
{
	boolean_t	call_again;
	int		i;
	xfs_buf_t	*ialloc_context;
	xfs_inode_t	*ip;
	xfs_trans_t	*ntp;
	int		error;

	call_again = B_FALSE;
	ialloc_context = (xfs_buf_t *)0;
	error = libxfs_ialloc(*tp, pip, mode, nlink, rdev, cr, (xfs_prid_t) 0,
			   1, &ialloc_context, &call_again, &ip);
	if (error) {
		return error;
	}
	if (call_again) {
		xfs_trans_bhold(*tp, ialloc_context);
		ntp = xfs_trans_dup(*tp);
		xfs_trans_commit(*tp, 0, NULL);
		*tp = ntp;
		if ((i = xfs_trans_reserve(*tp, 0, 0, 0, 0, 0))) {
			fprintf(stderr, "%s: cannot reserve space: %s\n",
				progname, strerror(errno));
			exit(1);
		}
		xfs_trans_bjoin(*tp, ialloc_context);
		error = libxfs_ialloc(*tp, pip, mode, nlink, rdev, cr,
				   (xfs_prid_t) 0, 1, &ialloc_context,
				   &call_again, &ip);
		if (error) {
			return error;
		}
	}
	*ipp = ip;
	ASSERT(ip);
	return error;
}
Пример #5
0
/*
 * Allocates a new inode from disk and return a pointer to the
 * incore copy. This routine will internally commit the current
 * transaction and allocate a new one if the Space Manager needed
 * to do an allocation to replenish the inode free-list.
 *
 * This routine is designed to be called from xfs_create and
 * xfs_create_dir.
 *
 */
int
xfs_dir_ialloc(
	xfs_trans_t	**tpp,		/* input: current transaction;
					   output: may be a new transaction. */
	xfs_inode_t	*dp,		/* directory within whose allocate
					   the inode. */
	mode_t		mode,
	xfs_nlink_t	nlink,
	xfs_dev_t	rdev,
	prid_t		prid,		/* project id */
	int		okalloc,	/* ok to allocate new space */
	xfs_inode_t	**ipp,		/* pointer to inode; it will be
					   locked. */
	int		*committed)

{
	xfs_trans_t	*tp;
	xfs_trans_t	*ntp;
	xfs_inode_t	*ip;
	xfs_buf_t	*ialloc_context = NULL;
	boolean_t	call_again = B_FALSE;
	int		code;
	uint		log_res;
	uint		log_count;
	void		*dqinfo;
	uint		tflags;

	tp = *tpp;
	ASSERT(tp->t_flags & XFS_TRANS_PERM_LOG_RES);

	/*
	 * xfs_ialloc will return a pointer to an incore inode if
	 * the Space Manager has an available inode on the free
	 * list. Otherwise, it will do an allocation and replenish
	 * the freelist.  Since we can only do one allocation per
	 * transaction without deadlocks, we will need to commit the
	 * current transaction and start a new one.  We will then
	 * need to call xfs_ialloc again to get the inode.
	 *
	 * If xfs_ialloc did an allocation to replenish the freelist,
	 * it returns the bp containing the head of the freelist as
	 * ialloc_context. We will hold a lock on it across the
	 * transaction commit so that no other process can steal
	 * the inode(s) that we've just allocated.
	 */
	code = xfs_ialloc(tp, dp, mode, nlink, rdev, prid, okalloc,
			  &ialloc_context, &call_again, &ip);

	/*
	 * Return an error if we were unable to allocate a new inode.
	 * This should only happen if we run out of space on disk or
	 * encounter a disk error.
	 */
	if (code) {
		*ipp = NULL;
		return code;
	}
	if (!call_again && (ip == NULL)) {
		*ipp = NULL;
		return XFS_ERROR(ENOSPC);
	}

	/*
	 * If call_again is set, then we were unable to get an
	 * inode in one operation.  We need to commit the current
	 * transaction and call xfs_ialloc() again.  It is guaranteed
	 * to succeed the second time.
	 */
	if (call_again) {

		/*
		 * Normally, xfs_trans_commit releases all the locks.
		 * We call bhold to hang on to the ialloc_context across
		 * the commit.  Holding this buffer prevents any other
		 * processes from doing any allocations in this
		 * allocation group.
		 */
		xfs_trans_bhold(tp, ialloc_context);
		/*
		 * Save the log reservation so we can use
		 * them in the next transaction.
		 */
		log_res = xfs_trans_get_log_res(tp);
		log_count = xfs_trans_get_log_count(tp);

		/*
		 * We want the quota changes to be associated with the next
		 * transaction, NOT this one. So, detach the dqinfo from this
		 * and attach it to the next transaction.
		 */
		dqinfo = NULL;
		tflags = 0;
		if (tp->t_dqinfo) {
			dqinfo = (void *)tp->t_dqinfo;
			tp->t_dqinfo = NULL;
			tflags = tp->t_flags & XFS_TRANS_DQ_DIRTY;
			tp->t_flags &= ~(XFS_TRANS_DQ_DIRTY);
		}

		ntp = xfs_trans_dup(tp);
		code = xfs_trans_commit(tp, 0);
		tp = ntp;
		if (committed != NULL) {
			*committed = 1;
		}
		/*
		 * If we get an error during the commit processing,
		 * release the buffer that is still held and return
		 * to the caller.
		 */
		if (code) {
			xfs_buf_relse(ialloc_context);
			if (dqinfo) {
				tp->t_dqinfo = dqinfo;
				xfs_trans_free_dqinfo(tp);
			}
			*tpp = ntp;
			*ipp = NULL;
			return code;
		}

		/*
		 * transaction commit worked ok so we can drop the extra ticket
		 * reference that we gained in xfs_trans_dup()
		 */
		xfs_log_ticket_put(tp->t_ticket);
		code = xfs_trans_reserve(tp, 0, log_res, 0,
					 XFS_TRANS_PERM_LOG_RES, log_count);
		/*
		 * Re-attach the quota info that we detached from prev trx.
		 */
		if (dqinfo) {
			tp->t_dqinfo = dqinfo;
			tp->t_flags |= tflags;
		}

		if (code) {
			xfs_buf_relse(ialloc_context);
			*tpp = ntp;
			*ipp = NULL;
			return code;
		}
		xfs_trans_bjoin(tp, ialloc_context);

		/*
		 * Call ialloc again. Since we've locked out all
		 * other allocations in this allocation group,
		 * this call should always succeed.
		 */
		code = xfs_ialloc(tp, dp, mode, nlink, rdev, prid,
				  okalloc, &ialloc_context, &call_again, &ip);

		/*
		 * If we get an error at this point, return to the caller
		 * so that the current transaction can be aborted.
		 */
		if (code) {
			*tpp = tp;
			*ipp = NULL;
			return code;
		}
		ASSERT ((!call_again) && (ip != NULL));

	} else {
		if (committed != NULL) {
			*committed = 0;
		}
	}

	*ipp = ip;
	*tpp = tp;

	return 0;
}
Пример #6
0
int
xfs_attr_set(
	struct xfs_inode	*dp,
	const unsigned char	*name,
	unsigned char		*value,
	int			valuelen,
	int			flags)
{
	struct xfs_mount	*mp = dp->i_mount;
	struct xfs_buf		*leaf_bp = NULL;
	struct xfs_da_args	args;
	struct xfs_trans_res	tres;
	int			rsvd = (flags & ATTR_ROOT) != 0;
	int			error, err2, local;

	XFS_STATS_INC(mp, xs_attr_set);

	if (XFS_FORCED_SHUTDOWN(dp->i_mount))
		return -EIO;

	error = xfs_attr_args_init(&args, dp, name, flags);
	if (error)
		return error;

	args.value = value;
	args.valuelen = valuelen;
	args.op_flags = XFS_DA_OP_ADDNAME | XFS_DA_OP_OKNOENT;
	args.total = xfs_attr_calc_size(&args, &local);

	error = xfs_qm_dqattach(dp);
	if (error)
		return error;

	/*
	 * If the inode doesn't have an attribute fork, add one.
	 * (inode must not be locked when we call this routine)
	 */
	if (XFS_IFORK_Q(dp) == 0) {
		int sf_size = sizeof(xfs_attr_sf_hdr_t) +
			XFS_ATTR_SF_ENTSIZE_BYNAME(args.namelen, valuelen);

		error = xfs_bmap_add_attrfork(dp, sf_size, rsvd);
		if (error)
			return error;
	}

	tres.tr_logres = M_RES(mp)->tr_attrsetm.tr_logres +
			 M_RES(mp)->tr_attrsetrt.tr_logres * args.total;
	tres.tr_logcount = XFS_ATTRSET_LOG_COUNT;
	tres.tr_logflags = XFS_TRANS_PERM_LOG_RES;

	/*
	 * Root fork attributes can use reserved data blocks for this
	 * operation if necessary
	 */
	error = xfs_trans_alloc(mp, &tres, args.total, 0,
			rsvd ? XFS_TRANS_RESERVE : 0, &args.trans);
	if (error)
		return error;

	xfs_ilock(dp, XFS_ILOCK_EXCL);
	error = xfs_trans_reserve_quota_nblks(args.trans, dp, args.total, 0,
				rsvd ? XFS_QMOPT_RES_REGBLKS | XFS_QMOPT_FORCE_RES :
				       XFS_QMOPT_RES_REGBLKS);
	if (error) {
		xfs_iunlock(dp, XFS_ILOCK_EXCL);
		xfs_trans_cancel(args.trans);
		return error;
	}

	xfs_trans_ijoin(args.trans, dp, 0);

	/*
	 * If the attribute list is non-existent or a shortform list,
	 * upgrade it to a single-leaf-block attribute list.
	 */
	if (dp->i_d.di_aformat == XFS_DINODE_FMT_LOCAL ||
	    (dp->i_d.di_aformat == XFS_DINODE_FMT_EXTENTS &&
	     dp->i_d.di_anextents == 0)) {

		/*
		 * Build initial attribute list (if required).
		 */
		if (dp->i_d.di_aformat == XFS_DINODE_FMT_EXTENTS)
			xfs_attr_shortform_create(&args);

		/*
		 * Try to add the attr to the attribute list in
		 * the inode.
		 */
		error = xfs_attr_shortform_addname(&args);
		if (error != -ENOSPC) {
			/*
			 * Commit the shortform mods, and we're done.
			 * NOTE: this is also the error path (EEXIST, etc).
			 */
			ASSERT(args.trans != NULL);

			/*
			 * If this is a synchronous mount, make sure that
			 * the transaction goes to disk before returning
			 * to the user.
			 */
			if (mp->m_flags & XFS_MOUNT_WSYNC)
				xfs_trans_set_sync(args.trans);

			if (!error && (flags & ATTR_KERNOTIME) == 0) {
				xfs_trans_ichgtime(args.trans, dp,
							XFS_ICHGTIME_CHG);
			}
			err2 = xfs_trans_commit(args.trans);
			xfs_iunlock(dp, XFS_ILOCK_EXCL);

			return error ? error : err2;
		}

		/*
		 * It won't fit in the shortform, transform to a leaf block.
		 * GROT: another possible req'mt for a double-split btree op.
		 */
		error = xfs_attr_shortform_to_leaf(&args, &leaf_bp);
		if (error)
			goto out;
		/*
		 * Prevent the leaf buffer from being unlocked so that a
		 * concurrent AIL push cannot grab the half-baked leaf
		 * buffer and run into problems with the write verifier.
		 */
		xfs_trans_bhold(args.trans, leaf_bp);
		error = xfs_defer_finish(&args.trans);
		if (error)
			goto out;

		/*
		 * Commit the leaf transformation.  We'll need another (linked)
		 * transaction to add the new attribute to the leaf, which
		 * means that we have to hold & join the leaf buffer here too.
		 */
		error = xfs_trans_roll_inode(&args.trans, dp);
		if (error)
			goto out;
		xfs_trans_bjoin(args.trans, leaf_bp);
		leaf_bp = NULL;
	}

	if (xfs_bmap_one_block(dp, XFS_ATTR_FORK))
		error = xfs_attr_leaf_addname(&args);
	else
		error = xfs_attr_node_addname(&args);
	if (error)
		goto out;

	/*
	 * If this is a synchronous mount, make sure that the
	 * transaction goes to disk before returning to the user.
	 */
	if (mp->m_flags & XFS_MOUNT_WSYNC)
		xfs_trans_set_sync(args.trans);

	if ((flags & ATTR_KERNOTIME) == 0)
		xfs_trans_ichgtime(args.trans, dp, XFS_ICHGTIME_CHG);

	/*
	 * Commit the last in the sequence of transactions.
	 */
	xfs_trans_log_inode(args.trans, dp, XFS_ILOG_CORE);
	error = xfs_trans_commit(args.trans);
	xfs_iunlock(dp, XFS_ILOCK_EXCL);

	return error;

out:
	if (leaf_bp)
		xfs_trans_brelse(args.trans, leaf_bp);
	if (args.trans)
		xfs_trans_cancel(args.trans);
	xfs_iunlock(dp, XFS_ILOCK_EXCL);
	return error;
}
/*
 * Allocate a block and fill it with dquots.
 * This is called when the bmapi finds a hole.
 */
STATIC int
xfs_qm_dqalloc(
	xfs_trans_t	**tpp,
	xfs_mount_t	*mp,
	xfs_dquot_t	*dqp,
	xfs_inode_t	*quotip,
	xfs_fileoff_t	offset_fsb,
	xfs_buf_t	**O_bpp)
{
	xfs_fsblock_t	firstblock;
	xfs_bmap_free_t flist;
	xfs_bmbt_irec_t map;
	int		nmaps, error, committed;
	xfs_buf_t	*bp;
	xfs_trans_t	*tp = *tpp;

	ASSERT(tp != NULL);
	xfs_dqtrace_entry(dqp, "DQALLOC");

	/*
	 * Initialize the bmap freelist prior to calling bmapi code.
	 */
	XFS_BMAP_INIT(&flist, &firstblock);
	xfs_ilock(quotip, XFS_ILOCK_EXCL);
	/*
	 * Return if this type of quotas is turned off while we didn't
	 * have an inode lock
	 */
	if (XFS_IS_THIS_QUOTA_OFF(dqp)) {
		xfs_iunlock(quotip, XFS_ILOCK_EXCL);
		return (ESRCH);
	}

	/*
	 * xfs_trans_commit normally decrements the vnode ref count
	 * when it unlocks the inode. Since we want to keep the quota
	 * inode around, we bump the vnode ref count now.
	 */
	VN_HOLD(XFS_ITOV(quotip));

	xfs_trans_ijoin(tp, quotip, XFS_ILOCK_EXCL);
	nmaps = 1;
	if ((error = xfs_bmapi(tp, quotip,
			      offset_fsb, XFS_DQUOT_CLUSTER_SIZE_FSB,
			      XFS_BMAPI_METADATA | XFS_BMAPI_WRITE,
			      &firstblock,
			      XFS_QM_DQALLOC_SPACE_RES(mp),
			      &map, &nmaps, &flist))) {
		goto error0;
	}
	ASSERT(map.br_blockcount == XFS_DQUOT_CLUSTER_SIZE_FSB);
	ASSERT(nmaps == 1);
	ASSERT((map.br_startblock != DELAYSTARTBLOCK) &&
	       (map.br_startblock != HOLESTARTBLOCK));

	/*
	 * Keep track of the blkno to save a lookup later
	 */
	dqp->q_blkno = XFS_FSB_TO_DADDR(mp, map.br_startblock);

	/* now we can just get the buffer (there's nothing to read yet) */
	bp = xfs_trans_get_buf(tp, mp->m_ddev_targp,
			       dqp->q_blkno,
			       XFS_QI_DQCHUNKLEN(mp),
			       0);
	if (!bp || (error = XFS_BUF_GETERROR(bp)))
		goto error1;
	/*
	 * Make a chunk of dquots out of this buffer and log
	 * the entire thing.
	 */
	xfs_qm_init_dquot_blk(tp, mp, be32_to_cpu(dqp->q_core.d_id),
			      dqp->dq_flags & XFS_DQ_ALLTYPES, bp);

	/*
	 * xfs_bmap_finish() may commit the current transaction and
	 * start a second transaction if the freelist is not empty.
	 *
	 * Since we still want to modify this buffer, we need to
	 * ensure that the buffer is not released on commit of
	 * the first transaction and ensure the buffer is added to the
	 * second transaction.
	 *
	 * If there is only one transaction then don't stop the buffer
	 * from being released when it commits later on.
	 */

	xfs_trans_bhold(tp, bp);

	if ((error = xfs_bmap_finish(tpp, &flist, firstblock, &committed))) {
		goto error1;
	}

	if (committed) {
		tp = *tpp;
		xfs_trans_bjoin(tp, bp);
	} else {
		xfs_trans_bhold_release(tp, bp);
	}

	*O_bpp = bp;
	return 0;

      error1:
	xfs_bmap_cancel(&flist);
      error0:
	xfs_iunlock(quotip, XFS_ILOCK_EXCL);

	return (error);
}
Пример #8
0
/*
 * Allocate a block and fill it with dquots.
 * This is called when the bmapi finds a hole.
 */
STATIC int
xfs_qm_dqalloc(
	xfs_trans_t	**tpp,
	xfs_mount_t	*mp,
	xfs_dquot_t	*dqp,
	xfs_inode_t	*quotip,
	xfs_fileoff_t	offset_fsb,
	xfs_buf_t	**O_bpp)
{
	xfs_fsblock_t	firstblock;
	xfs_bmap_free_t flist;
	xfs_bmbt_irec_t map;
	int		nmaps, error, committed;
	xfs_buf_t	*bp;
	xfs_trans_t	*tp = *tpp;

	ASSERT(tp != NULL);

	trace_xfs_dqalloc(dqp);

	/*
	 * Initialize the bmap freelist prior to calling bmapi code.
	 */
	xfs_bmap_init(&flist, &firstblock);
	xfs_ilock(quotip, XFS_ILOCK_EXCL);
	/*
	 * Return if this type of quotas is turned off while we didn't
	 * have an inode lock
	 */
	if (!xfs_this_quota_on(dqp->q_mount, dqp->dq_flags)) {
		xfs_iunlock(quotip, XFS_ILOCK_EXCL);
		return (ESRCH);
	}

	xfs_trans_ijoin(tp, quotip, XFS_ILOCK_EXCL);
	nmaps = 1;
	error = xfs_bmapi_write(tp, quotip, offset_fsb,
				XFS_DQUOT_CLUSTER_SIZE_FSB, XFS_BMAPI_METADATA,
				&firstblock, XFS_QM_DQALLOC_SPACE_RES(mp),
				&map, &nmaps, &flist);
	if (error)
		goto error0;
	ASSERT(map.br_blockcount == XFS_DQUOT_CLUSTER_SIZE_FSB);
	ASSERT(nmaps == 1);
	ASSERT((map.br_startblock != DELAYSTARTBLOCK) &&
	       (map.br_startblock != HOLESTARTBLOCK));

	/*
	 * Keep track of the blkno to save a lookup later
	 */
	dqp->q_blkno = XFS_FSB_TO_DADDR(mp, map.br_startblock);

	/* now we can just get the buffer (there's nothing to read yet) */
	bp = xfs_trans_get_buf(tp, mp->m_ddev_targp,
			       dqp->q_blkno,
			       mp->m_quotainfo->qi_dqchunklen,
			       0);
	if (!bp) {
		error = ENOMEM;
		goto error1;
	}
	bp->b_ops = &xfs_dquot_buf_ops;

	/*
	 * Make a chunk of dquots out of this buffer and log
	 * the entire thing.
	 */
	xfs_qm_init_dquot_blk(tp, mp, be32_to_cpu(dqp->q_core.d_id),
			      dqp->dq_flags & XFS_DQ_ALLTYPES, bp);

	/*
	 * xfs_bmap_finish() may commit the current transaction and
	 * start a second transaction if the freelist is not empty.
	 *
	 * Since we still want to modify this buffer, we need to
	 * ensure that the buffer is not released on commit of
	 * the first transaction and ensure the buffer is added to the
	 * second transaction.
	 *
	 * If there is only one transaction then don't stop the buffer
	 * from being released when it commits later on.
	 */

	xfs_trans_bhold(tp, bp);

	if ((error = xfs_bmap_finish(tpp, &flist, &committed))) {
		goto error1;
	}

	if (committed) {
		tp = *tpp;
		xfs_trans_bjoin(tp, bp);
	} else {
		xfs_trans_bhold_release(tp, bp);
	}

	*O_bpp = bp;
	return 0;

      error1:
	xfs_bmap_cancel(&flist);
      error0:
	xfs_iunlock(quotip, XFS_ILOCK_EXCL);

	return (error);
}
Пример #9
0
/*
 * Ensure that the given in-core dquot has a buffer on disk backing it, and
 * return the buffer locked and held. This is called when the bmapi finds a
 * hole.
 */
STATIC int
xfs_dquot_disk_alloc(
	struct xfs_trans	**tpp,
	struct xfs_dquot	*dqp,
	struct xfs_buf		**bpp)
{
	struct xfs_bmbt_irec	map;
	struct xfs_trans	*tp = *tpp;
	struct xfs_mount	*mp = tp->t_mountp;
	struct xfs_buf		*bp;
	struct xfs_inode	*quotip = xfs_quota_inode(mp, dqp->dq_flags);
	int			nmaps = 1;
	int			error;

	trace_xfs_dqalloc(dqp);

	xfs_ilock(quotip, XFS_ILOCK_EXCL);
	if (!xfs_this_quota_on(dqp->q_mount, dqp->dq_flags)) {
		/*
		 * Return if this type of quotas is turned off while we didn't
		 * have an inode lock
		 */
		xfs_iunlock(quotip, XFS_ILOCK_EXCL);
		return -ESRCH;
	}

	/* Create the block mapping. */
	xfs_trans_ijoin(tp, quotip, XFS_ILOCK_EXCL);
	error = xfs_bmapi_write(tp, quotip, dqp->q_fileoffset,
			XFS_DQUOT_CLUSTER_SIZE_FSB, XFS_BMAPI_METADATA,
			XFS_QM_DQALLOC_SPACE_RES(mp), &map, &nmaps);
	if (error)
		return error;
	ASSERT(map.br_blockcount == XFS_DQUOT_CLUSTER_SIZE_FSB);
	ASSERT(nmaps == 1);
	ASSERT((map.br_startblock != DELAYSTARTBLOCK) &&
	       (map.br_startblock != HOLESTARTBLOCK));

	/*
	 * Keep track of the blkno to save a lookup later
	 */
	dqp->q_blkno = XFS_FSB_TO_DADDR(mp, map.br_startblock);

	/* now we can just get the buffer (there's nothing to read yet) */
	bp = xfs_trans_get_buf(tp, mp->m_ddev_targp, dqp->q_blkno,
			mp->m_quotainfo->qi_dqchunklen, 0);
	if (!bp)
		return -ENOMEM;
	bp->b_ops = &xfs_dquot_buf_ops;

	/*
	 * Make a chunk of dquots out of this buffer and log
	 * the entire thing.
	 */
	xfs_qm_init_dquot_blk(tp, mp, be32_to_cpu(dqp->q_core.d_id),
			      dqp->dq_flags & XFS_DQ_ALLTYPES, bp);
	xfs_buf_set_ref(bp, XFS_DQUOT_REF);

	/*
	 * Hold the buffer and join it to the dfops so that we'll still own
	 * the buffer when we return to the caller.  The buffer disposal on
	 * error must be paid attention to very carefully, as it has been
	 * broken since commit efa092f3d4c6 "[XFS] Fixes a bug in the quota
	 * code when allocating a new dquot record" in 2005, and the later
	 * conversion to xfs_defer_ops in commit 310a75a3c6c747 failed to keep
	 * the buffer locked across the _defer_finish call.  We can now do
	 * this correctly with xfs_defer_bjoin.
	 *
	 * Above, we allocated a disk block for the dquot information and used
	 * get_buf to initialize the dquot. If the _defer_finish fails, the old
	 * transaction is gone but the new buffer is not joined or held to any
	 * transaction, so we must _buf_relse it.
	 *
	 * If everything succeeds, the caller of this function is returned a
	 * buffer that is locked and held to the transaction.  The caller
	 * is responsible for unlocking any buffer passed back, either
	 * manually or by committing the transaction.  On error, the buffer is
	 * released and not passed back.
	 */
	xfs_trans_bhold(tp, bp);
	error = xfs_defer_finish(tpp);
	if (error) {
		xfs_trans_bhold_release(*tpp, bp);
		xfs_trans_brelse(*tpp, bp);
		return error;
	}
	*bpp = bp;
	return 0;
}