2 * Copyright (C) 2016 Oracle. All Rights Reserved.
4 * Author: Darrick J. Wong <darrick.wong@oracle.com>
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.
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.
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.
22 #include "xfs_shared.h"
23 #include "xfs_format.h"
24 #include "xfs_log_format.h"
25 #include "xfs_trans_resv.h"
27 #include "xfs_mount.h"
28 #include "xfs_defer.h"
29 #include "xfs_alloc.h"
30 #include "xfs_error.h"
31 #include "xfs_trace.h"
32 #include "xfs_cksum.h"
33 #include "xfs_trans.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"
41 #include "xfs_refcount_btree.h"
42 #include "xfs_ialloc_btree.h"
45 * Per-AG Block Reservations
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.
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.
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. :)
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.
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).
89 struct xfs_perag *pag,
90 enum xfs_ag_resv_type 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;
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;
110 trace_xfs_ag_resv_critical(pag, type, avail);
112 /* Critically low if less than 10% or max btree height remains. */
113 return XFS_TEST_ERROR(avail < orig / 10 || avail < XFS_BTREE_MAXLEVELS,
114 pag->pag_mount, XFS_ERRTAG_AG_RESV_CRITICAL);
118 * How many blocks are reserved but not used, and therefore must not be
123 struct xfs_perag *pag,
124 enum xfs_ag_resv_type type)
128 len = pag->pag_meta_resv.ar_reserved + pag->pag_agfl_resv.ar_reserved;
130 case XFS_AG_RESV_METADATA:
131 case XFS_AG_RESV_AGFL:
132 len -= xfs_perag_resv(pag, type)->ar_reserved;
134 case XFS_AG_RESV_NONE:
141 trace_xfs_ag_resv_needed(pag, type, len);
146 /* Clean out a reservation */
149 struct xfs_perag *pag,
150 enum xfs_ag_resv_type type)
152 struct xfs_ag_resv *resv;
153 xfs_extlen_t oldresv;
156 trace_xfs_ag_resv_free(pag, type, 0);
158 resv = xfs_perag_resv(pag, type);
159 if (pag->pag_agno == 0)
160 pag->pag_mount->m_ag_max_usable += resv->ar_asked;
162 * AGFL blocks are always considered "free", so whatever
163 * was reserved at mount time must be given back at umount.
165 if (type == XFS_AG_RESV_AGFL)
166 oldresv = resv->ar_orig_reserved;
168 oldresv = resv->ar_reserved;
169 error = xfs_mod_fdblocks(pag->pag_mount, oldresv, true);
170 resv->ar_reserved = 0;
174 trace_xfs_ag_resv_free_error(pag->pag_mount, pag->pag_agno,
179 /* Free a per-AG reservation. */
182 struct xfs_perag *pag)
187 error = __xfs_ag_resv_free(pag, XFS_AG_RESV_AGFL);
188 err2 = __xfs_ag_resv_free(pag, XFS_AG_RESV_METADATA);
196 struct xfs_perag *pag,
197 enum xfs_ag_resv_type type,
201 struct xfs_mount *mp = pag->pag_mount;
202 struct xfs_ag_resv *resv;
204 xfs_extlen_t reserved;
208 reserved = ask - used;
210 error = xfs_mod_fdblocks(mp, -(int64_t)reserved, true);
212 trace_xfs_ag_resv_init_error(pag->pag_mount, pag->pag_agno,
215 "Per-AG reservation for AG %u failed. Filesystem may run out of space.",
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.
226 if (pag->pag_agno == 0)
227 mp->m_ag_max_usable -= ask;
229 resv = xfs_perag_resv(pag, type);
230 resv->ar_asked = ask;
231 resv->ar_reserved = resv->ar_orig_reserved = reserved;
233 trace_xfs_ag_resv_init(pag, type, ask);
237 /* Create a per-AG block reservation. */
240 struct xfs_perag *pag)
242 struct xfs_mount *mp = pag->pag_mount;
243 xfs_agnumber_t agno = pag->pag_agno;
248 /* Create the metadata reservation. */
249 if (pag->pag_meta_resv.ar_asked == 0) {
252 error = xfs_refcountbt_calc_reserves(mp, agno, &ask, &used);
256 error = xfs_finobt_calc_reserves(mp, agno, &ask, &used);
260 error = __xfs_ag_resv_init(pag, XFS_AG_RESV_METADATA,
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.
272 mp->m_inotbt_nores = true;
274 error = xfs_refcountbt_calc_reserves(mp, agno, &ask,
279 error = __xfs_ag_resv_init(pag, XFS_AG_RESV_METADATA,
286 /* Create the AGFL metadata reservation */
287 if (pag->pag_agfl_resv.ar_asked == 0) {
290 error = xfs_rmapbt_calc_reserves(mp, agno, &ask, &used);
294 error = __xfs_ag_resv_init(pag, XFS_AG_RESV_AGFL, ask, used);
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);
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);
313 /* Allocate a block from the reservation. */
315 xfs_ag_resv_alloc_extent(
316 struct xfs_perag *pag,
317 enum xfs_ag_resv_type type,
318 struct xfs_alloc_arg *args)
320 struct xfs_ag_resv *resv;
324 trace_xfs_ag_resv_alloc_extent(pag, type, args->len);
327 case XFS_AG_RESV_METADATA:
328 case XFS_AG_RESV_AGFL:
329 resv = xfs_perag_resv(pag, type);
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);
341 len = min_t(xfs_extlen_t, args->len, resv->ar_reserved);
342 resv->ar_reserved -= len;
343 if (type == XFS_AG_RESV_AGFL)
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. */
349 xfs_trans_mod_sb(args->tp, XFS_TRANS_SB_FDBLOCKS,
350 -((int64_t)args->len - len));
353 /* Free a block to the reservation. */
355 xfs_ag_resv_free_extent(
356 struct xfs_perag *pag,
357 enum xfs_ag_resv_type type,
358 struct xfs_trans *tp,
361 xfs_extlen_t leftover;
362 struct xfs_ag_resv *resv;
364 trace_xfs_ag_resv_free_extent(pag, type, len);
367 case XFS_AG_RESV_METADATA:
368 case XFS_AG_RESV_AGFL:
369 resv = xfs_perag_resv(pag, type);
374 case XFS_AG_RESV_NONE:
375 xfs_trans_mod_sb(tp, XFS_TRANS_SB_FDBLOCKS, (int64_t)len);
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)
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. */
387 xfs_trans_mod_sb(tp, XFS_TRANS_SB_FDBLOCKS, len - leftover);