xfs_alloc_fix_freelist(
	struct xfs_alloc_arg	*args,	/* allocation argument structure */
	int			flags)	/* XFS_ALLOC_FLAG_... */
{
	struct xfs_mount	*mp = args->mp;
	struct xfs_perag	*pag = args->pag;
	struct xfs_trans	*tp = args->tp;
	struct xfs_buf		*agbp = NULL;
	struct xfs_buf		*agflbp = NULL;
	struct xfs_alloc_arg	targs;	/* local allocation arguments */
	xfs_agblock_t		bno;	/* freelist block */
	xfs_extlen_t		need;	/* total blocks needed in freelist */
	int			error = 0;

	/* deferred ops (AGFL block frees) require permanent transactions */
	ASSERT(tp->t_flags & XFS_TRANS_PERM_LOG_RES);

	if (!pag->pagf_init) {
		error = xfs_alloc_read_agf(mp, tp, args->agno, flags, &agbp);
		if (error) {
			/* Couldn't lock the AGF so skip this AG. */
			if (error == -EAGAIN)
				error = 0;
			goto out_no_agbp;
		}
	}

	/*
	 * If this is a metadata preferred pag and we are user data then try
	 * somewhere else if we are not being asked to try harder at this
	 * point
	 */
	if (pag->pagf_metadata && (args->datatype & XFS_ALLOC_USERDATA) &&
	    (flags & XFS_ALLOC_FLAG_TRYLOCK)) {
		ASSERT(!(flags & XFS_ALLOC_FLAG_FREEING));
		goto out_agbp_relse;
	}

	need = xfs_alloc_min_freelist(mp, pag);
	if (!xfs_alloc_space_available(args, need, flags |
			XFS_ALLOC_FLAG_CHECK))
		goto out_agbp_relse;

	/*
	 * Get the a.g. freespace buffer.
	 * Can fail if we're not blocking on locks, and it's held.
	 */
	if (!agbp) {
		error = xfs_alloc_read_agf(mp, tp, args->agno, flags, &agbp);
		if (error) {
			/* Couldn't lock the AGF so skip this AG. */
			if (error == -EAGAIN)
				error = 0;
			goto out_no_agbp;
		}
	}

	/* reset a padding mismatched agfl before final free space check */
	if (pag->pagf_agflreset)
		xfs_agfl_reset(tp, agbp, pag);

	/* If there isn't enough total space or single-extent, reject it. */
	need = xfs_alloc_min_freelist(mp, pag);
	if (!xfs_alloc_space_available(args, need, flags))
		goto out_agbp_relse;

	/*
	 * Make the freelist shorter if it's too long.
	 *
	 * Note that from this point onwards, we will always release the agf and
	 * agfl buffers on error. This handles the case where we error out and
	 * the buffers are clean or may not have been joined to the transaction
	 * and hence need to be released manually. If they have been joined to
	 * the transaction, then xfs_trans_brelse() will handle them
	 * appropriately based on the recursion count and dirty state of the
	 * buffer.
	 *
	 * XXX (dgc): When we have lots of free space, does this buy us
	 * anything other than extra overhead when we need to put more blocks
	 * back on the free list? Maybe we should only do this when space is
	 * getting low or the AGFL is more than half full?
	 *
	 * The NOSHRINK flag prevents the AGFL from being shrunk if it's too
	 * big; the NORMAP flag prevents AGFL expand/shrink operations from
	 * updating the rmapbt.  Both flags are used in xfs_repair while we're
	 * rebuilding the rmapbt, and neither are used by the kernel.  They're
	 * both required to ensure that rmaps are correctly recorded for the
	 * regenerated AGFL, bnobt, and cntbt.  See repair/phase5.c and
	 * repair/rmap.c in xfsprogs for details.
	 */
	memset(&targs, 0, sizeof(targs));
	/* struct copy below */
	if (flags & XFS_ALLOC_FLAG_NORMAP)
		targs.oinfo = XFS_RMAP_OINFO_SKIP_UPDATE;
	else
		targs.oinfo = XFS_RMAP_OINFO_AG;
	while (!(flags & XFS_ALLOC_FLAG_NOSHRINK) && pag->pagf_flcount > need) {
		error = xfs_alloc_get_freelist(tp, agbp, &bno, 0);
		if (error)
			goto out_agbp_relse;

		/* defer agfl frees */
		xfs_defer_agfl_block(tp, args->agno, bno, &targs.oinfo);
	}

	targs.tp = tp;
	targs.mp = mp;
	targs.agbp = agbp;
	targs.agno = args->agno;
	targs.alignment = targs.minlen = targs.prod = 1;
	targs.type = XFS_ALLOCTYPE_THIS_AG;
	targs.pag = pag;
	error = xfs_alloc_read_agfl(mp, tp, targs.agno, &agflbp);
	if (error)
		goto out_agbp_relse;

	/* Make the freelist longer if it's too short. */
	while (pag->pagf_flcount < need) {
		targs.agbno = 0;
		targs.maxlen = need - pag->pagf_flcount;
		targs.resv = XFS_AG_RESV_AGFL;

		/* Allocate as many blocks as possible at once. */
		error = xfs_alloc_ag_vextent(&targs);
		if (error)
			goto out_agflbp_relse;

		/*
		 * Stop if we run out.  Won't happen if callers are obeying
		 * the restrictions correctly.  Can happen for free calls
		 * on a completely full ag.
		 */
		if (targs.agbno == NULLAGBLOCK) {
			if (flags & XFS_ALLOC_FLAG_FREEING)
				break;
			goto out_agflbp_relse;
		}
		/*
		 * Put each allocated block on the list.
		 */
		for (bno = targs.agbno; bno < targs.agbno + targs.len; bno++) {
			error = xfs_alloc_put_freelist(tp, agbp,
							agflbp, bno, 0);
			if (error)
				goto out_agflbp_relse;
		}
	}
	xfs_trans_brelse(tp, agflbp);
	args->agbp = agbp;
	return 0;

out_agflbp_relse:
	xfs_trans_brelse(tp, agflbp);
out_agbp_relse:
	if (agbp)
		xfs_trans_brelse(tp, agbp);
out_no_agbp:
	args->agbp = NULL;
	return error;
}