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1 : // SPDX-License-Identifier: GPL-2.0+
2 : /*
3 : * Copyright (C) 2016 Oracle. All Rights Reserved.
4 : * Author: Darrick J. Wong <darrick.wong@oracle.com>
5 : */
6 : #include "xfs.h"
7 : #include "xfs_fs.h"
8 : #include "xfs_shared.h"
9 : #include "xfs_format.h"
10 : #include "xfs_log_format.h"
11 : #include "xfs_trans_resv.h"
12 : #include "xfs_mount.h"
13 : #include "xfs_alloc.h"
14 : #include "xfs_errortag.h"
15 : #include "xfs_error.h"
16 : #include "xfs_trace.h"
17 : #include "xfs_trans.h"
18 : #include "xfs_rmap_btree.h"
19 : #include "xfs_btree.h"
20 : #include "xfs_refcount_btree.h"
21 : #include "xfs_ialloc_btree.h"
22 : #include "xfs_ag.h"
23 : #include "xfs_ag_resv.h"
24 :
25 : /*
26 : * Per-AG Block Reservations
27 : *
28 : * For some kinds of allocation group metadata structures, it is advantageous
29 : * to reserve a small number of blocks in each AG so that future expansions of
30 : * that data structure do not encounter ENOSPC because errors during a btree
31 : * split cause the filesystem to go offline.
32 : *
33 : * Prior to the introduction of reflink, this wasn't an issue because the free
34 : * space btrees maintain a reserve of space (the AGFL) to handle any expansion
35 : * that may be necessary; and allocations of other metadata (inodes, BMBT,
36 : * dir/attr) aren't restricted to a single AG. However, with reflink it is
37 : * possible to allocate all the space in an AG, have subsequent reflink/CoW
38 : * activity expand the refcount btree, and discover that there's no space left
39 : * to handle that expansion. Since we can calculate the maximum size of the
40 : * refcount btree, we can reserve space for it and avoid ENOSPC.
41 : *
42 : * Handling per-AG reservations consists of three changes to the allocator's
43 : * behavior: First, because these reservations are always needed, we decrease
44 : * the ag_max_usable counter to reflect the size of the AG after the reserved
45 : * blocks are taken. Second, the reservations must be reflected in the
46 : * fdblocks count to maintain proper accounting. Third, each AG must maintain
47 : * its own reserved block counter so that we can calculate the amount of space
48 : * that must remain free to maintain the reservations. Fourth, the "remaining
49 : * reserved blocks" count must be used when calculating the length of the
50 : * longest free extent in an AG and to clamp maxlen in the per-AG allocation
51 : * functions. In other words, we maintain a virtual allocation via in-core
52 : * accounting tricks so that we don't have to clean up after a crash. :)
53 : *
54 : * Reserved blocks can be managed by passing one of the enum xfs_ag_resv_type
55 : * values via struct xfs_alloc_arg or directly to the xfs_free_extent
56 : * function. It might seem a little funny to maintain a reservoir of blocks
57 : * to feed another reservoir, but the AGFL only holds enough blocks to get
58 : * through the next transaction. The per-AG reservation is to ensure (we
59 : * hope) that each AG never runs out of blocks. Each data structure wanting
60 : * to use the reservation system should update ask/used in xfs_ag_resv_init.
61 : */
62 :
63 : /*
64 : * Are we critically low on blocks? For now we'll define that as the number
65 : * of blocks we can get our hands on being less than 10% of what we reserved
66 : * or less than some arbitrary number (maximum btree height).
67 : */
68 : bool
69 96305003 : xfs_ag_resv_critical(
70 : struct xfs_perag *pag,
71 : enum xfs_ag_resv_type type)
72 : {
73 96305003 : xfs_extlen_t avail;
74 96305003 : xfs_extlen_t orig;
75 :
76 96305003 : switch (type) {
77 48152499 : case XFS_AG_RESV_METADATA:
78 48152499 : avail = pag->pagf_freeblks - pag->pag_rmapbt_resv.ar_reserved;
79 48152499 : orig = pag->pag_meta_resv.ar_asked;
80 48152499 : break;
81 48152504 : case XFS_AG_RESV_RMAPBT:
82 48152504 : avail = pag->pagf_freeblks + pag->pagf_flcount -
83 48152504 : pag->pag_meta_resv.ar_reserved;
84 48152504 : orig = pag->pag_rmapbt_resv.ar_asked;
85 48152504 : break;
86 0 : default:
87 0 : ASSERT(0);
88 0 : return false;
89 : }
90 :
91 96305003 : trace_xfs_ag_resv_critical(pag, type, avail);
92 :
93 : /* Critically low if less than 10% or max btree height remains. */
94 96305002 : return XFS_TEST_ERROR(avail < orig / 10 ||
95 : avail < pag->pag_mount->m_agbtree_maxlevels,
96 : pag->pag_mount, XFS_ERRTAG_AG_RESV_CRITICAL);
97 : }
98 :
99 : /*
100 : * How many blocks are reserved but not used, and therefore must not be
101 : * allocated away?
102 : */
103 : xfs_extlen_t
104 169747158 : xfs_ag_resv_needed(
105 : struct xfs_perag *pag,
106 : enum xfs_ag_resv_type type)
107 : {
108 169747158 : xfs_extlen_t len;
109 :
110 169747158 : len = pag->pag_meta_resv.ar_reserved + pag->pag_rmapbt_resv.ar_reserved;
111 169747158 : switch (type) {
112 : case XFS_AG_RESV_METADATA:
113 : case XFS_AG_RESV_RMAPBT:
114 153552 : len -= xfs_perag_resv(pag, type)->ar_reserved;
115 153552 : break;
116 : case XFS_AG_RESV_NONE:
117 : /* empty */
118 : break;
119 0 : default:
120 0 : ASSERT(0);
121 : }
122 :
123 169747158 : trace_xfs_ag_resv_needed(pag, type, len);
124 :
125 169749477 : return len;
126 : }
127 :
128 : /* Clean out a reservation */
129 : static int
130 495682 : __xfs_ag_resv_free(
131 : struct xfs_perag *pag,
132 : enum xfs_ag_resv_type type)
133 : {
134 495682 : struct xfs_ag_resv *resv;
135 495682 : xfs_extlen_t oldresv;
136 495682 : int error;
137 :
138 495682 : trace_xfs_ag_resv_free(pag, type, 0);
139 :
140 495682 : resv = xfs_perag_resv(pag, type);
141 495682 : if (pag->pag_agno == 0)
142 90772 : pag->pag_mount->m_ag_max_usable += resv->ar_asked;
143 : /*
144 : * RMAPBT blocks come from the AGFL and AGFL blocks are always
145 : * considered "free", so whatever was reserved at mount time must be
146 : * given back at umount.
147 : */
148 495682 : if (type == XFS_AG_RESV_RMAPBT)
149 247841 : oldresv = resv->ar_orig_reserved;
150 : else
151 247841 : oldresv = resv->ar_reserved;
152 495682 : error = xfs_mod_fdblocks(pag->pag_mount, oldresv, true);
153 495682 : resv->ar_reserved = 0;
154 495682 : resv->ar_asked = 0;
155 495682 : resv->ar_orig_reserved = 0;
156 :
157 495682 : if (error)
158 0 : trace_xfs_ag_resv_free_error(pag->pag_mount, pag->pag_agno,
159 0 : error, _RET_IP_);
160 495682 : return error;
161 : }
162 :
163 : /* Free a per-AG reservation. */
164 : int
165 247841 : xfs_ag_resv_free(
166 : struct xfs_perag *pag)
167 : {
168 247841 : int error;
169 247841 : int err2;
170 :
171 247841 : error = __xfs_ag_resv_free(pag, XFS_AG_RESV_RMAPBT);
172 247841 : err2 = __xfs_ag_resv_free(pag, XFS_AG_RESV_METADATA);
173 247841 : if (err2 && !error)
174 0 : error = err2;
175 247841 : return error;
176 : }
177 :
178 : static int
179 479122 : __xfs_ag_resv_init(
180 : struct xfs_perag *pag,
181 : enum xfs_ag_resv_type type,
182 : xfs_extlen_t ask,
183 : xfs_extlen_t used)
184 : {
185 479122 : struct xfs_mount *mp = pag->pag_mount;
186 479122 : struct xfs_ag_resv *resv;
187 479122 : int error;
188 479122 : xfs_extlen_t hidden_space;
189 :
190 479122 : if (used > ask)
191 : ask = used;
192 :
193 479122 : switch (type) {
194 : case XFS_AG_RESV_RMAPBT:
195 : /*
196 : * Space taken by the rmapbt is not subtracted from fdblocks
197 : * because the rmapbt lives in the free space. Here we must
198 : * subtract the entire reservation from fdblocks so that we
199 : * always have blocks available for rmapbt expansion.
200 : */
201 : hidden_space = ask;
202 : break;
203 239561 : case XFS_AG_RESV_METADATA:
204 : /*
205 : * Space taken by all other metadata btrees are accounted
206 : * on-disk as used space. We therefore only hide the space
207 : * that is reserved but not used by the trees.
208 : */
209 239561 : hidden_space = ask - used;
210 239561 : break;
211 0 : default:
212 0 : ASSERT(0);
213 0 : return -EINVAL;
214 : }
215 :
216 479122 : if (XFS_TEST_ERROR(false, mp, XFS_ERRTAG_AG_RESV_FAIL))
217 : error = -ENOSPC;
218 : else
219 479122 : error = xfs_mod_fdblocks(mp, -(int64_t)hidden_space, true);
220 479122 : if (error) {
221 0 : trace_xfs_ag_resv_init_error(pag->pag_mount, pag->pag_agno,
222 0 : error, _RET_IP_);
223 0 : xfs_warn(mp,
224 : "Per-AG reservation for AG %u failed. Filesystem may run out of space.",
225 : pag->pag_agno);
226 0 : return error;
227 : }
228 :
229 : /*
230 : * Reduce the maximum per-AG allocation length by however much we're
231 : * trying to reserve for an AG. Since this is a filesystem-wide
232 : * counter, we only make the adjustment for AG 0. This assumes that
233 : * there aren't any AGs hungrier for per-AG reservation than AG 0.
234 : */
235 479122 : if (pag->pag_agno == 0)
236 86598 : mp->m_ag_max_usable -= ask;
237 :
238 479122 : resv = xfs_perag_resv(pag, type);
239 479122 : resv->ar_asked = ask;
240 479122 : resv->ar_orig_reserved = hidden_space;
241 479122 : resv->ar_reserved = ask - used;
242 :
243 479122 : trace_xfs_ag_resv_init(pag, type, ask);
244 479122 : return 0;
245 : }
246 :
247 : /* Create a per-AG block reservation. */
248 : int
249 240201 : xfs_ag_resv_init(
250 : struct xfs_perag *pag,
251 : struct xfs_trans *tp)
252 : {
253 240201 : struct xfs_mount *mp = pag->pag_mount;
254 240201 : xfs_extlen_t ask;
255 240201 : xfs_extlen_t used;
256 240201 : int error = 0, error2;
257 240201 : bool has_resv = false;
258 :
259 : /* Create the metadata reservation. */
260 240201 : if (pag->pag_meta_resv.ar_asked == 0) {
261 239639 : ask = used = 0;
262 :
263 239639 : error = xfs_refcountbt_calc_reserves(mp, tp, pag, &ask, &used);
264 239639 : if (error)
265 78 : goto out;
266 :
267 239561 : error = xfs_finobt_calc_reserves(pag, tp, &ask, &used);
268 239561 : if (error)
269 0 : goto out;
270 :
271 239561 : error = __xfs_ag_resv_init(pag, XFS_AG_RESV_METADATA,
272 : ask, used);
273 239561 : if (error) {
274 : /*
275 : * Because we didn't have per-AG reservations when the
276 : * finobt feature was added we might not be able to
277 : * reserve all needed blocks. Warn and fall back to the
278 : * old and potentially buggy code in that case, but
279 : * ensure we do have the reservation for the refcountbt.
280 : */
281 0 : ask = used = 0;
282 :
283 0 : mp->m_finobt_nores = true;
284 :
285 0 : error = xfs_refcountbt_calc_reserves(mp, tp, pag, &ask,
286 : &used);
287 0 : if (error)
288 0 : goto out;
289 :
290 0 : error = __xfs_ag_resv_init(pag, XFS_AG_RESV_METADATA,
291 : ask, used);
292 0 : if (error)
293 0 : goto out;
294 : }
295 239561 : if (ask)
296 236937 : has_resv = true;
297 : }
298 :
299 : /* Create the RMAPBT metadata reservation */
300 240123 : if (pag->pag_rmapbt_resv.ar_asked == 0) {
301 239561 : ask = used = 0;
302 :
303 239561 : error = xfs_rmapbt_calc_reserves(mp, tp, pag, &ask, &used);
304 239561 : if (error)
305 0 : goto out;
306 :
307 239561 : error = __xfs_ag_resv_init(pag, XFS_AG_RESV_RMAPBT, ask, used);
308 239561 : if (error)
309 0 : goto out;
310 239561 : if (ask)
311 : has_resv = true;
312 : }
313 :
314 5414 : out:
315 : /*
316 : * Initialize the pagf if we have at least one active reservation on the
317 : * AG. This may have occurred already via reservation calculation, but
318 : * fall back to an explicit init to ensure the in-core allocbt usage
319 : * counters are initialized as soon as possible. This is important
320 : * because filesystems with large perag reservations are susceptible to
321 : * free space reservation problems that the allocbt counter is used to
322 : * address.
323 : */
324 5492 : if (has_resv) {
325 236937 : error2 = xfs_alloc_read_agf(pag, tp, 0, NULL);
326 236937 : if (error2)
327 : return error2;
328 :
329 : /*
330 : * If there isn't enough space in the AG to satisfy the
331 : * reservation, let the caller know that there wasn't enough
332 : * space. Callers are responsible for deciding what to do
333 : * next, since (in theory) we can stumble along with
334 : * insufficient reservation if data blocks are being freed to
335 : * replenish the AG's free space.
336 : */
337 236937 : if (!error &&
338 236937 : xfs_perag_resv(pag, XFS_AG_RESV_METADATA)->ar_reserved +
339 236937 : xfs_perag_resv(pag, XFS_AG_RESV_RMAPBT)->ar_reserved >
340 236937 : pag->pagf_freeblks + pag->pagf_flcount)
341 2 : error = -ENOSPC;
342 : }
343 :
344 : return error;
345 : }
346 :
347 : /* Allocate a block from the reservation. */
348 : void
349 44863390 : xfs_ag_resv_alloc_extent(
350 : struct xfs_perag *pag,
351 : enum xfs_ag_resv_type type,
352 : struct xfs_alloc_arg *args)
353 : {
354 44863390 : struct xfs_ag_resv *resv;
355 44863390 : xfs_extlen_t len;
356 44863390 : uint field;
357 :
358 44863390 : trace_xfs_ag_resv_alloc_extent(pag, type, args->len);
359 :
360 44864565 : switch (type) {
361 : case XFS_AG_RESV_AGFL:
362 : return;
363 : case XFS_AG_RESV_METADATA:
364 : case XFS_AG_RESV_RMAPBT:
365 374033 : resv = xfs_perag_resv(pag, type);
366 374033 : break;
367 0 : default:
368 0 : ASSERT(0);
369 44490532 : fallthrough;
370 44490532 : case XFS_AG_RESV_NONE:
371 44490532 : field = args->wasdel ? XFS_TRANS_SB_RES_FDBLOCKS :
372 : XFS_TRANS_SB_FDBLOCKS;
373 44490532 : xfs_trans_mod_sb(args->tp, field, -(int64_t)args->len);
374 44490532 : return;
375 : }
376 :
377 374033 : len = min_t(xfs_extlen_t, args->len, resv->ar_reserved);
378 374033 : resv->ar_reserved -= len;
379 374033 : if (type == XFS_AG_RESV_RMAPBT)
380 : return;
381 : /* Allocations of reserved blocks only need on-disk sb updates... */
382 76776 : xfs_trans_mod_sb(args->tp, XFS_TRANS_SB_RES_FDBLOCKS, -(int64_t)len);
383 : /* ...but non-reserved blocks need in-core and on-disk updates. */
384 76776 : if (args->len > len)
385 0 : xfs_trans_mod_sb(args->tp, XFS_TRANS_SB_FDBLOCKS,
386 0 : -((int64_t)args->len - len));
387 : }
388 :
389 : /* Free a block to the reservation. */
390 : void
391 41100023 : xfs_ag_resv_free_extent(
392 : struct xfs_perag *pag,
393 : enum xfs_ag_resv_type type,
394 : struct xfs_trans *tp,
395 : xfs_extlen_t len)
396 : {
397 41100023 : xfs_extlen_t leftover;
398 41100023 : struct xfs_ag_resv *resv;
399 :
400 41100023 : trace_xfs_ag_resv_free_extent(pag, type, len);
401 :
402 41100082 : switch (type) {
403 : case XFS_AG_RESV_AGFL:
404 : return;
405 : case XFS_AG_RESV_METADATA:
406 : case XFS_AG_RESV_RMAPBT:
407 187483 : resv = xfs_perag_resv(pag, type);
408 187483 : break;
409 0 : default:
410 0 : ASSERT(0);
411 40757688 : fallthrough;
412 40757688 : case XFS_AG_RESV_NONE:
413 40757688 : xfs_trans_mod_sb(tp, XFS_TRANS_SB_FDBLOCKS, (int64_t)len);
414 40757688 : return;
415 : }
416 :
417 187483 : leftover = min_t(xfs_extlen_t, len, resv->ar_asked - resv->ar_reserved);
418 187483 : resv->ar_reserved += leftover;
419 187483 : if (type == XFS_AG_RESV_RMAPBT)
420 : return;
421 : /* Freeing into the reserved pool only requires on-disk update... */
422 65498 : xfs_trans_mod_sb(tp, XFS_TRANS_SB_RES_FDBLOCKS, len);
423 : /* ...but freeing beyond that requires in-core and on-disk update. */
424 65498 : if (len > leftover)
425 0 : xfs_trans_mod_sb(tp, XFS_TRANS_SB_FDBLOCKS, len - leftover);
426 : }
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