summaryrefslogtreecommitdiffstats
path: root/fs/xfs/libxfs/xfs_ag_resv.c
blob: e3ae0f2b4294cae7cb8adec79886b18ba6fe34dd (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
/*
 * 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 "xfs.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_error.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"

/*
 * 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 avail < orig / 10 || avail < XFS_BTREE_MAXLEVELS;
}

/*
 * 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);
	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;

	resv = xfs_perag_resv(pag, type);
	if (used > ask)
		ask = used;
	resv->ar_asked = ask;
	resv->ar_reserved = resv->ar_orig_reserved = ask - used;
	mp->m_ag_max_usable -= ask;

	trace_xfs_ag_resv_init(pag, type, ask);

	error = xfs_mod_fdblocks(mp, -(int64_t)resv->ar_reserved, true);
	if (error)
		trace_xfs_ag_resv_init_error(pag->pag_mount, pag->pag_agno,
				error, _RET_IP_);

	return error;
}

/* Create a per-AG block reservation. */
int
xfs_ag_resv_init(
	struct xfs_perag		*pag)
{
	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_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_ag_resv_init(pag, XFS_AG_RESV_AGFL, ask, used);
		if (error)
			goto out;
	}

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);
}
OpenPOWER on IntegriCloud