[thirdparty/xfsprogs-dev.git] / libxfs / xfs_ag_resv.c

/*
 * Copyright (C) 2016 Oracle.  All Rights Reserved.
 *
 * Author: Darrick J. Wong <darrick.wong@oracle.com>
 *
 * 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; either version 2
 * of the License, or (at your option) any later version.
 *
 * 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 "libxfs_priv.h"
#include "xfs_fs.h"
#include "xfs_shared.h"
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_trans_resv.h"
#include "xfs_sb.h"
#include "xfs_mount.h"
#include "xfs_defer.h"
#include "xfs_alloc.h"
#include "xfs_errortag.h"
#include "xfs_trace.h"
#include "xfs_cksum.h"
#include "xfs_trans.h"
#include "xfs_bit.h"
#include "xfs_bmap.h"
#include "xfs_bmap_btree.h"
#include "xfs_ag_resv.h"
#include "xfs_trans_space.h"
#include "xfs_rmap_btree.h"
#include "xfs_btree.h"
#include "xfs_refcount_btree.h"
#include "xfs_ialloc_btree.h"

/*
 * Per-AG Block Reservations
 *
 * For some kinds of allocation group metadata structures, it is advantageous
 * to reserve a small number of blocks in each AG so that future expansions of
 * that data structure do not encounter ENOSPC because errors during a btree
 * split cause the filesystem to go offline.
 *
 * Prior to the introduction of reflink, this wasn't an issue because the free
 * space btrees maintain a reserve of space (the AGFL) to handle any expansion
 * that may be necessary; and allocations of other metadata (inodes, BMBT,
 * dir/attr) aren't restricted to a single AG.  However, with reflink it is
 * possible to allocate all the space in an AG, have subsequent reflink/CoW
 * activity expand the refcount btree, and discover that there's no space left
 * to handle that expansion.  Since we can calculate the maximum size of the
 * refcount btree, we can reserve space for it and avoid ENOSPC.
 *
 * Handling per-AG reservations consists of three changes to the allocator's
 * behavior:  First, because these reservations are always needed, we decrease
 * the ag_max_usable counter to reflect the size of the AG after the reserved
 * blocks are taken.  Second, the reservations must be reflected in the
 * fdblocks count to maintain proper accounting.  Third, each AG must maintain
 * its own reserved block counter so that we can calculate the amount of space
 * that must remain free to maintain the reservations.  Fourth, the "remaining
 * reserved blocks" count must be used when calculating the length of the
 * longest free extent in an AG and to clamp maxlen in the per-AG allocation
 * functions.  In other words, we maintain a virtual allocation via in-core
 * accounting tricks so that we don't have to clean up after a crash. :)
 *
 * Reserved blocks can be managed by passing one of the enum xfs_ag_resv_type
 * values via struct xfs_alloc_arg or directly to the xfs_free_extent
 * function.  It might seem a little funny to maintain a reservoir of blocks
 * to feed another reservoir, but the AGFL only holds enough blocks to get
 * through the next transaction.  The per-AG reservation is to ensure (we
 * hope) that each AG never runs out of blocks.  Each data structure wanting
 * to use the reservation system should update ask/used in xfs_ag_resv_init.
 */

/*
 * Are we critically low on blocks?  For now we'll define that as the number
 * of blocks we can get our hands on being less than 10% of what we reserved
 * or less than some arbitrary number (maximum btree height).
 */
bool
xfs_ag_resv_critical(
	struct xfs_perag		*pag,
	enum xfs_ag_resv_type		type)
{
	xfs_extlen_t			avail;
	xfs_extlen_t			orig;

	switch (type) {
	case XFS_AG_RESV_METADATA:
		avail = pag->pagf_freeblks - pag->pag_agfl_resv.ar_reserved;
		orig = pag->pag_meta_resv.ar_asked;
		break;
	case XFS_AG_RESV_AGFL:
		avail = pag->pagf_freeblks + pag->pagf_flcount -
			pag->pag_meta_resv.ar_reserved;
		orig = pag->pag_agfl_resv.ar_asked;
		break;
	default:
		ASSERT(0);
		return false;
	}

	trace_xfs_ag_resv_critical(pag, type, avail);

	/* Critically low if less than 10% or max btree height remains. */
	return XFS_TEST_ERROR(avail < orig / 10 || avail < XFS_BTREE_MAXLEVELS,
			pag->pag_mount, XFS_ERRTAG_AG_RESV_CRITICAL);
}

/*
 * How many blocks are reserved but not used, and therefore must not be
 * allocated away?
 */
xfs_extlen_t
xfs_ag_resv_needed(
	struct xfs_perag		*pag,
	enum xfs_ag_resv_type		type)
{
	xfs_extlen_t			len;

	len = pag->pag_meta_resv.ar_reserved + pag->pag_agfl_resv.ar_reserved;
	switch (type) {
	case XFS_AG_RESV_METADATA:
	case XFS_AG_RESV_AGFL:
		len -= xfs_perag_resv(pag, type)->ar_reserved;
		break;
	case XFS_AG_RESV_NONE:
		/* empty */
		break;
	default:
		ASSERT(0);
	}

	trace_xfs_ag_resv_needed(pag, type, len);

	return len;
}

/* Clean out a reservation */
static int
__xfs_ag_resv_free(
	struct xfs_perag		*pag,
	enum xfs_ag_resv_type		type)
{
	struct xfs_ag_resv		*resv;
	xfs_extlen_t			oldresv;
	int				error;

	trace_xfs_ag_resv_free(pag, type, 0);

	resv = xfs_perag_resv(pag, type);
	if (pag->pag_agno == 0)
		pag->pag_mount->m_ag_max_usable += resv->ar_asked;
	/*
	 * AGFL blocks are always considered "free", so whatever
	 * was reserved at mount time must be given back at umount.
	 */
	if (type == XFS_AG_RESV_AGFL)
		oldresv = resv->ar_orig_reserved;
	else
		oldresv = resv->ar_reserved;
	error = xfs_mod_fdblocks(pag->pag_mount, oldresv, true);
	resv->ar_reserved = 0;
	resv->ar_asked = 0;

	if (error)
		trace_xfs_ag_resv_free_error(pag->pag_mount, pag->pag_agno,
				error, _RET_IP_);
	return error;
}

/* Free a per-AG reservation. */
int
xfs_ag_resv_free(
	struct xfs_perag		*pag)
{
	int				error;
	int				err2;

	error = __xfs_ag_resv_free(pag, XFS_AG_RESV_AGFL);
	err2 = __xfs_ag_resv_free(pag, XFS_AG_RESV_METADATA);
	if (err2 && !error)
		error = err2;
	return error;
}

static int
__xfs_ag_resv_init(
	struct xfs_perag		*pag,
	enum xfs_ag_resv_type		type,
	xfs_extlen_t			ask,
	xfs_extlen_t			used)
{
	struct xfs_mount		*mp = pag->pag_mount;
	struct xfs_ag_resv		*resv;
	int				error;
	xfs_extlen_t			reserved;

	if (used > ask)
		ask = used;
	reserved = ask - used;

	error = xfs_mod_fdblocks(mp, -(int64_t)reserved, true);
	if (error) {
		trace_xfs_ag_resv_init_error(pag->pag_mount, pag->pag_agno,
				error, _RET_IP_);
		xfs_warn(mp,
"Per-AG reservation for AG %u failed.  Filesystem may run out of space.",
				pag->pag_agno);
		return error;
	}

	/*
	 * Reduce the maximum per-AG allocation length by however much we're
	 * trying to reserve for an AG.  Since this is a filesystem-wide
	 * counter, we only make the adjustment for AG 0.  This assumes that
	 * there aren't any AGs hungrier for per-AG reservation than AG 0.
	 */
	if (pag->pag_agno == 0)
		mp->m_ag_max_usable -= ask;

	resv = xfs_perag_resv(pag, type);
	resv->ar_asked = ask;
	resv->ar_reserved = resv->ar_orig_reserved = reserved;

	trace_xfs_ag_resv_init(pag, type, ask);
	return 0;
}

/* Create a per-AG block reservation. */
int
xfs_ag_resv_init(
	struct xfs_perag		*pag)
{
	struct xfs_mount		*mp = pag->pag_mount;
	xfs_agnumber_t			agno = pag->pag_agno;
	xfs_extlen_t			ask;
	xfs_extlen_t			used;
	int				error = 0;

	/* Create the metadata reservation. */
	if (pag->pag_meta_resv.ar_asked == 0) {
		ask = used = 0;

		error = xfs_refcountbt_calc_reserves(mp, agno, &ask, &used);
		if (error)
			goto out;

		error = xfs_finobt_calc_reserves(mp, agno, &ask, &used);
		if (error)
			goto out;

		error = __xfs_ag_resv_init(pag, XFS_AG_RESV_METADATA,
				ask, used);
		if (error) {
			/*
			 * Because we didn't have per-AG reservations when the
			 * finobt feature was added we might not be able to
			 * reserve all needed blocks.  Warn and fall back to the
			 * old and potentially buggy code in that case, but
			 * ensure we do have the reservation for the refcountbt.
			 */
			ask = used = 0;

			mp->m_inotbt_nores = true;

			error = xfs_refcountbt_calc_reserves(mp, agno, &ask,
					&used);
			if (error)
				goto out;

			error = __xfs_ag_resv_init(pag, XFS_AG_RESV_METADATA,
					ask, used);
			if (error)
				goto out;
		}
	}

	/* Create the AGFL metadata reservation */
	if (pag->pag_agfl_resv.ar_asked == 0) {
		ask = used = 0;

		error = xfs_rmapbt_calc_reserves(mp, agno, &ask, &used);
		if (error)
			goto out;

		error = __xfs_ag_resv_init(pag, XFS_AG_RESV_AGFL, ask, used);
		if (error)
			goto out;
	}

#ifdef DEBUG
	/* need to read in the AGF for the ASSERT below to work */
	error = xfs_alloc_pagf_init(pag->pag_mount, NULL, pag->pag_agno, 0);
	if (error)
		return error;

	ASSERT(xfs_perag_resv(pag, XFS_AG_RESV_METADATA)->ar_reserved +
	       xfs_perag_resv(pag, XFS_AG_RESV_AGFL)->ar_reserved <=
	       pag->pagf_freeblks + pag->pagf_flcount);
#endif
out:
	return error;
}

/* Allocate a block from the reservation. */
void
xfs_ag_resv_alloc_extent(
	struct xfs_perag		*pag,
	enum xfs_ag_resv_type		type,
	struct xfs_alloc_arg		*args)
{
	struct xfs_ag_resv		*resv;
	xfs_extlen_t			len;
	uint				field;

	trace_xfs_ag_resv_alloc_extent(pag, type, args->len);

	switch (type) {
	case XFS_AG_RESV_METADATA:
	case XFS_AG_RESV_AGFL:
		resv = xfs_perag_resv(pag, type);
		break;
	default:
		ASSERT(0);
		/* fall through */
	case XFS_AG_RESV_NONE:
		field = args->wasdel ? XFS_TRANS_SB_RES_FDBLOCKS :
				       XFS_TRANS_SB_FDBLOCKS;
		xfs_trans_mod_sb(args->tp, field, -(int64_t)args->len);
		return;
	}

	len = min_t(xfs_extlen_t, args->len, resv->ar_reserved);
	resv->ar_reserved -= len;
	if (type == XFS_AG_RESV_AGFL)
		return;
	/* Allocations of reserved blocks only need on-disk sb updates... */
	xfs_trans_mod_sb(args->tp, XFS_TRANS_SB_RES_FDBLOCKS, -(int64_t)len);
	/* ...but non-reserved blocks need in-core and on-disk updates. */
	if (args->len > len)
		xfs_trans_mod_sb(args->tp, XFS_TRANS_SB_FDBLOCKS,
				-((int64_t)args->len - len));
}

/* Free a block to the reservation. */
void
xfs_ag_resv_free_extent(
	struct xfs_perag		*pag,
	enum xfs_ag_resv_type		type,
	struct xfs_trans		*tp,
	xfs_extlen_t			len)
{
	xfs_extlen_t			leftover;
	struct xfs_ag_resv		*resv;

	trace_xfs_ag_resv_free_extent(pag, type, len);

	switch (type) {
	case XFS_AG_RESV_METADATA:
	case XFS_AG_RESV_AGFL:
		resv = xfs_perag_resv(pag, type);
		break;
	default:
		ASSERT(0);
		/* fall through */
	case XFS_AG_RESV_NONE:
		xfs_trans_mod_sb(tp, XFS_TRANS_SB_FDBLOCKS, (int64_t)len);
		return;
	}

	leftover = min_t(xfs_extlen_t, len, resv->ar_asked - resv->ar_reserved);
	resv->ar_reserved += leftover;
	if (type == XFS_AG_RESV_AGFL)
		return;
	/* Freeing into the reserved pool only requires on-disk update... */
	xfs_trans_mod_sb(tp, XFS_TRANS_SB_RES_FDBLOCKS, len);
	/* ...but freeing beyond that requires in-core and on-disk update. */
	if (len > leftover)
		xfs_trans_mod_sb(tp, XFS_TRANS_SB_FDBLOCKS, len - leftover);
}
Commit	Line	Data
cf8ce220 DW	1	/*
	2	* Copyright (C) 2016 Oracle. All Rights Reserved.
	3	*
	4	* Author: Darrick J. Wong <darrick.wong@oracle.com>
	5	*
	6	* This program is free software; you can redistribute it and/or
	7	* modify it under the terms of the GNU General Public License
	8	* as published by the Free Software Foundation; either version 2
	9	* of the License, or (at your option) any later version.
	10	*
	11	* This program is distributed in the hope that it would be useful,
	12	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	13	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	14	* GNU General Public License for more details.
	15	*
	16	* You should have received a copy of the GNU General Public License
	17	* along with this program; if not, write the Free Software Foundation,
	18	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
	19	*/
	20	#include "libxfs_priv.h"
	21	#include "xfs_fs.h"
	22	#include "xfs_shared.h"
	23	#include "xfs_format.h"
	24	#include "xfs_log_format.h"
	25	#include "xfs_trans_resv.h"
	26	#include "xfs_sb.h"
	27	#include "xfs_mount.h"
	28	#include "xfs_defer.h"
	29	#include "xfs_alloc.h"
56d3fc2b	30	#include "xfs_errortag.h"
cf8ce220 DW	31	#include "xfs_trace.h"
	32	#include "xfs_cksum.h"
	33	#include "xfs_trans.h"
	34	#include "xfs_bit.h"
	35	#include "xfs_bmap.h"
	36	#include "xfs_bmap_btree.h"
	37	#include "xfs_ag_resv.h"
	38	#include "xfs_trans_space.h"
	39	#include "xfs_rmap_btree.h"
	40	#include "xfs_btree.h"
02cc8b2a	41	#include "xfs_refcount_btree.h"
74e502ac	42	#include "xfs_ialloc_btree.h"
cf8ce220 DW	43
	44	/*
	45	* Per-AG Block Reservations
	46	*
	47	* For some kinds of allocation group metadata structures, it is advantageous
	48	* to reserve a small number of blocks in each AG so that future expansions of
	49	* that data structure do not encounter ENOSPC because errors during a btree
	50	* split cause the filesystem to go offline.
	51	*
	52	* Prior to the introduction of reflink, this wasn't an issue because the free
	53	* space btrees maintain a reserve of space (the AGFL) to handle any expansion
	54	* that may be necessary; and allocations of other metadata (inodes, BMBT,
	55	* dir/attr) aren't restricted to a single AG. However, with reflink it is
	56	* possible to allocate all the space in an AG, have subsequent reflink/CoW
	57	* activity expand the refcount btree, and discover that there's no space left
	58	* to handle that expansion. Since we can calculate the maximum size of the
	59	* refcount btree, we can reserve space for it and avoid ENOSPC.
	60	*
	61	* Handling per-AG reservations consists of three changes to the allocator's
	62	* behavior: First, because these reservations are always needed, we decrease
	63	* the ag_max_usable counter to reflect the size of the AG after the reserved
	64	* blocks are taken. Second, the reservations must be reflected in the
	65	* fdblocks count to maintain proper accounting. Third, each AG must maintain
	66	* its own reserved block counter so that we can calculate the amount of space
	67	* that must remain free to maintain the reservations. Fourth, the "remaining
	68	* reserved blocks" count must be used when calculating the length of the
	69	* longest free extent in an AG and to clamp maxlen in the per-AG allocation
	70	* functions. In other words, we maintain a virtual allocation via in-core
	71	* accounting tricks so that we don't have to clean up after a crash. :)
	72	*
	73	* Reserved blocks can be managed by passing one of the enum xfs_ag_resv_type
	74	* values via struct xfs_alloc_arg or directly to the xfs_free_extent
	75	* function. It might seem a little funny to maintain a reservoir of blocks
	76	* to feed another reservoir, but the AGFL only holds enough blocks to get
	77	* through the next transaction. The per-AG reservation is to ensure (we
	78	* hope) that each AG never runs out of blocks. Each data structure wanting
	79	* to use the reservation system should update ask/used in xfs_ag_resv_init.
	80	*/
	81
	82	/*
	83	* Are we critically low on blocks? For now we'll define that as the number
	84	* of blocks we can get our hands on being less than 10% of what we reserved
	85	* or less than some arbitrary number (maximum btree height).
	86	*/
	87	bool
	88	xfs_ag_resv_critical(
	89	struct xfs_perag *pag,
	90	enum xfs_ag_resv_type type)
	91	{
	92	xfs_extlen_t avail;
	93	xfs_extlen_t orig;
	94
	95	switch (type) {
	96	case XFS_AG_RESV_METADATA:
	97	avail = pag->pagf_freeblks - pag->pag_agfl_resv.ar_reserved;
	98	orig = pag->pag_meta_resv.ar_asked;
	99	break;
	100	case XFS_AG_RESV_AGFL:
	101	avail = pag->pagf_freeblks + pag->pagf_flcount -
	102	pag->pag_meta_resv.ar_reserved;
	103	orig = pag->pag_agfl_resv.ar_asked;
	104	break;
	105	default:
	106	ASSERT(0);
107	return false;
108	}
109
110	trace_xfs_ag_resv_critical(pag, type, avail);
111
112	/* Critically low if less than 10% or max btree height remains. */
c7bf1398	113	return XFS_TEST_ERROR(avail < orig / 10 \|\| avail < XFS_BTREE_MAXLEVELS,
e2a190dd	114	pag->pag_mount, XFS_ERRTAG_AG_RESV_CRITICAL);
cf8ce220 DW	115	}
	116
	117	/*
	118	* How many blocks are reserved but not used, and therefore must not be
	119	* allocated away?
	120	*/
	121	xfs_extlen_t
	122	xfs_ag_resv_needed(
	123	struct xfs_perag *pag,
	124	enum xfs_ag_resv_type type)
	125	{
	126	xfs_extlen_t len;
	127
	128	len = pag->pag_meta_resv.ar_reserved + pag->pag_agfl_resv.ar_reserved;
	129	switch (type) {
	130	case XFS_AG_RESV_METADATA:
	131	case XFS_AG_RESV_AGFL:
	132	len -= xfs_perag_resv(pag, type)->ar_reserved;
	133	break;
	134	case XFS_AG_RESV_NONE:
	135	/* empty */
	136	break;
	137	default:
	138	ASSERT(0);
	139	}
	140
	141	trace_xfs_ag_resv_needed(pag, type, len);
	142
	143	return len;
	144	}
	145
	146	/* Clean out a reservation */
	147	static int
	148	__xfs_ag_resv_free(
	149	struct xfs_perag *pag,
	150	enum xfs_ag_resv_type type)
	151	{
	152	struct xfs_ag_resv *resv;
	153	xfs_extlen_t oldresv;
	154	int error;
	155
	156	trace_xfs_ag_resv_free(pag, type, 0);
	157
	158	resv = xfs_perag_resv(pag, type);
8b068926 DW	159	if (pag->pag_agno == 0)
8b068926 DW	160	pag->pag_mount->m_ag_max_usable += resv->ar_asked;
cf8ce220 DW	161	/*
	162	* AGFL blocks are always considered "free", so whatever
	163	* was reserved at mount time must be given back at umount.
	164	*/
	165	if (type == XFS_AG_RESV_AGFL)
	166	oldresv = resv->ar_orig_reserved;
	167	else
	168	oldresv = resv->ar_reserved;
	169	error = xfs_mod_fdblocks(pag->pag_mount, oldresv, true);
	170	resv->ar_reserved = 0;
	171	resv->ar_asked = 0;
	172
	173	if (error)
	174	trace_xfs_ag_resv_free_error(pag->pag_mount, pag->pag_agno,
	175	error, _RET_IP_);
	176	return error;
	177	}
	178
	179	/* Free a per-AG reservation. */
	180	int
	181	xfs_ag_resv_free(
	182	struct xfs_perag *pag)
	183	{
	184	int error;
	185	int err2;
	186
	187	error = __xfs_ag_resv_free(pag, XFS_AG_RESV_AGFL);
	188	err2 = __xfs_ag_resv_free(pag, XFS_AG_RESV_METADATA);
	189	if (err2 && !error)
	190	error = err2;
	191	return error;
	192	}
	193
	194	static int
	195	__xfs_ag_resv_init(
	196	struct xfs_perag *pag,
	197	enum xfs_ag_resv_type type,
	198	xfs_extlen_t ask,
	199	xfs_extlen_t used)
	200	{
	201	struct xfs_mount *mp = pag->pag_mount;
	202	struct xfs_ag_resv *resv;
	203	int error;
2ffa676f	204	xfs_extlen_t reserved;
cf8ce220	205
cf8ce220 DW	206	if (used > ask)
cf8ce220 DW	207	ask = used;
2ffa676f	208	reserved = ask - used;
cf8ce220	209
2ffa676f CH	210	error = xfs_mod_fdblocks(mp, -(int64_t)reserved, true);
2ffa676f CH	211	if (error) {
cf8ce220 DW	212	trace_xfs_ag_resv_init_error(pag->pag_mount, pag->pag_agno,
cf8ce220 DW	213	error, _RET_IP_);
74e502ac CH	214	xfs_warn(mp,
	215	"Per-AG reservation for AG %u failed. Filesystem may run out of space.",
	216	pag->pag_agno);
2ffa676f CH	217	return error;
2ffa676f CH	218	}
cf8ce220	219
8b068926 DW	220	/*
	221	* Reduce the maximum per-AG allocation length by however much we're
	222	* trying to reserve for an AG. Since this is a filesystem-wide
	223	* counter, we only make the adjustment for AG 0. This assumes that
	224	* there aren't any AGs hungrier for per-AG reservation than AG 0.
	225	*/
	226	if (pag->pag_agno == 0)
	227	mp->m_ag_max_usable -= ask;
2ffa676f CH	228
	229	resv = xfs_perag_resv(pag, type);
	230	resv->ar_asked = ask;
	231	resv->ar_reserved = resv->ar_orig_reserved = reserved;
	232
	233	trace_xfs_ag_resv_init(pag, type, ask);
	234	return 0;
cf8ce220 DW	235	}
	236
	237	/* Create a per-AG block reservation. */
	238	int
	239	xfs_ag_resv_init(
	240	struct xfs_perag *pag)
	241	{
74e502ac CH	242	struct xfs_mount *mp = pag->pag_mount;
74e502ac CH	243	xfs_agnumber_t agno = pag->pag_agno;
cf8ce220 DW	244	xfs_extlen_t ask;
	245	xfs_extlen_t used;
	246	int error = 0;
	247
	248	/* Create the metadata reservation. */
	249	if (pag->pag_meta_resv.ar_asked == 0) {
	250	ask = used = 0;
	251
74e502ac	252	error = xfs_refcountbt_calc_reserves(mp, agno, &ask, &used);
02cc8b2a DW	253	if (error)
	254	goto out;
	255
74e502ac	256	error = xfs_finobt_calc_reserves(mp, agno, &ask, &used);
cf8ce220 DW	257	if (error)
cf8ce220 DW	258	goto out;
74e502ac CH	259
	260	error = __xfs_ag_resv_init(pag, XFS_AG_RESV_METADATA,
	261	ask, used);
	262	if (error) {
	263	/*
	264	* Because we didn't have per-AG reservations when the
	265	* finobt feature was added we might not be able to
	266	* reserve all needed blocks. Warn and fall back to the
	267	* old and potentially buggy code in that case, but
	268	* ensure we do have the reservation for the refcountbt.
	269	*/
	270	ask = used = 0;
	271
	272	mp->m_inotbt_nores = true;
	273
	274	error = xfs_refcountbt_calc_reserves(mp, agno, &ask,
	275	&used);
	276	if (error)
	277	goto out;
	278
	279	error = __xfs_ag_resv_init(pag, XFS_AG_RESV_METADATA,
	280	ask, used);
	281	if (error)
	282	goto out;
	283	}
cf8ce220 DW	284	}
	285
	286	/* Create the AGFL metadata reservation */
	287	if (pag->pag_agfl_resv.ar_asked == 0) {
	288	ask = used = 0;
	289
74e502ac	290	error = xfs_rmapbt_calc_reserves(mp, agno, &ask, &used);
02cc8b2a DW	291	if (error)
	292	goto out;
	293
cf8ce220 DW	294	error = __xfs_ag_resv_init(pag, XFS_AG_RESV_AGFL, ask, used);
	295	if (error)
	296	goto out;
	297	}
	298
74e502ac CH	299	#ifdef DEBUG
	300	/* need to read in the AGF for the ASSERT below to work */
	301	error = xfs_alloc_pagf_init(pag->pag_mount, NULL, pag->pag_agno, 0);
	302	if (error)
	303	return error;
	304
f21c57ed DW	305	ASSERT(xfs_perag_resv(pag, XFS_AG_RESV_METADATA)->ar_reserved +
	306	xfs_perag_resv(pag, XFS_AG_RESV_AGFL)->ar_reserved <=
	307	pag->pagf_freeblks + pag->pagf_flcount);
74e502ac	308	#endif
cf8ce220 DW	309	out:
	310	return error;
	311	}
	312
	313	/* Allocate a block from the reservation. */
	314	void
	315	xfs_ag_resv_alloc_extent(
	316	struct xfs_perag *pag,
	317	enum xfs_ag_resv_type type,
	318	struct xfs_alloc_arg *args)
	319	{
	320	struct xfs_ag_resv *resv;
	321	xfs_extlen_t len;
	322	uint field;
	323
	324	trace_xfs_ag_resv_alloc_extent(pag, type, args->len);
	325
	326	switch (type) {
	327	case XFS_AG_RESV_METADATA:
	328	case XFS_AG_RESV_AGFL:
	329	resv = xfs_perag_resv(pag, type);
	330	break;
	331	default:
	332	ASSERT(0);
	333	/* fall through */
	334	case XFS_AG_RESV_NONE:
	335	field = args->wasdel ? XFS_TRANS_SB_RES_FDBLOCKS :
	336	XFS_TRANS_SB_FDBLOCKS;
	337	xfs_trans_mod_sb(args->tp, field, -(int64_t)args->len);
	338	return;
	339	}
	340
	341	len = min_t(xfs_extlen_t, args->len, resv->ar_reserved);
	342	resv->ar_reserved -= len;
	343	if (type == XFS_AG_RESV_AGFL)
	344	return;
	345	/* Allocations of reserved blocks only need on-disk sb updates... */
	346	xfs_trans_mod_sb(args->tp, XFS_TRANS_SB_RES_FDBLOCKS, -(int64_t)len);
	347	/* ...but non-reserved blocks need in-core and on-disk updates. */
	348	if (args->len > len)
	349	xfs_trans_mod_sb(args->tp, XFS_TRANS_SB_FDBLOCKS,
	350	-((int64_t)args->len - len));
	351	}
	352
	353	/* Free a block to the reservation. */
	354	void
	355	xfs_ag_resv_free_extent(
	356	struct xfs_perag *pag,
	357	enum xfs_ag_resv_type type,
	358	struct xfs_trans *tp,
	359	xfs_extlen_t len)
	360	{
	361	xfs_extlen_t leftover;
	362	struct xfs_ag_resv *resv;
	363
	364	trace_xfs_ag_resv_free_extent(pag, type, len);
	365
	366	switch (type) {
	367	case XFS_AG_RESV_METADATA:
	368	case XFS_AG_RESV_AGFL:
	369	resv = xfs_perag_resv(pag, type);
	370	break;
	371	default:
	372	ASSERT(0);
373	/* fall through */
374	case XFS_AG_RESV_NONE:
375	xfs_trans_mod_sb(tp, XFS_TRANS_SB_FDBLOCKS, (int64_t)len);
376	return;
377	}
378
379	leftover = min_t(xfs_extlen_t, len, resv->ar_asked - resv->ar_reserved);
380	resv->ar_reserved += leftover;
381	if (type == XFS_AG_RESV_AGFL)
382	return;
383	/* Freeing into the reserved pool only requires on-disk update... */
384	xfs_trans_mod_sb(tp, XFS_TRANS_SB_RES_FDBLOCKS, len);
385	/* ...but freeing beyond that requires in-core and on-disk update. */
386	if (len > leftover)
387	xfs_trans_mod_sb(tp, XFS_TRANS_SB_FDBLOCKS, len - leftover);
388	}