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 xfs_ag_resv_critical( 70 struct xfs_perag *pag, 71 enum xfs_ag_resv_type type) 72 { 73 xfs_extlen_t avail; 74 xfs_extlen_t orig; 75 76 switch (type) { 77 case XFS_AG_RESV_METADATA: 78 avail = pag->pagf_freeblks - pag->pag_rmapbt_resv.ar_reserved; 79 orig = pag->pag_meta_resv.ar_asked; 80 break; 81 case XFS_AG_RESV_RMAPBT: 82 avail = pag->pagf_freeblks + pag->pagf_flcount - 83 pag->pag_meta_resv.ar_reserved; 84 orig = pag->pag_rmapbt_resv.ar_asked; 85 break; 86 default: 87 ASSERT(0); 88 return false; 89 } 90 91 trace_xfs_ag_resv_critical(pag, type, avail); 92 93 /* Critically low if less than 10% or max btree height remains. */ 94 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 xfs_ag_resv_needed( 105 struct xfs_perag *pag, 106 enum xfs_ag_resv_type type) 107 { 108 xfs_extlen_t len; 109 110 len = pag->pag_meta_resv.ar_reserved + pag->pag_rmapbt_resv.ar_reserved; 111 switch (type) { 112 case XFS_AG_RESV_METADATA: 113 case XFS_AG_RESV_RMAPBT: 114 len -= xfs_perag_resv(pag, type)->ar_reserved; 115 break; 116 case XFS_AG_RESV_NONE: 117 /* empty */ 118 break; 119 default: 120 ASSERT(0); 121 } 122 123 trace_xfs_ag_resv_needed(pag, type, len); 124 125 return len; 126 } 127 128 /* Clean out a reservation */ 129 static int 130 __xfs_ag_resv_free( 131 struct xfs_perag *pag, 132 enum xfs_ag_resv_type type) 133 { 134 struct xfs_ag_resv *resv; 135 xfs_extlen_t oldresv; 136 int error; 137 138 trace_xfs_ag_resv_free(pag, type, 0); 139 140 resv = xfs_perag_resv(pag, type); 141 if (pag->pag_agno == 0) 142 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 if (type == XFS_AG_RESV_RMAPBT) 149 oldresv = resv->ar_orig_reserved; 150 else 151 oldresv = resv->ar_reserved; 152 error = xfs_mod_fdblocks(pag->pag_mount, oldresv, true); 153 resv->ar_reserved = 0; 154 resv->ar_asked = 0; 155 resv->ar_orig_reserved = 0; 156 157 if (error) 158 trace_xfs_ag_resv_free_error(pag->pag_mount, pag->pag_agno, 159 error, _RET_IP_); 160 return error; 161 } 162 163 /* Free a per-AG reservation. */ 164 int 165 xfs_ag_resv_free( 166 struct xfs_perag *pag) 167 { 168 int error; 169 int err2; 170 171 error = __xfs_ag_resv_free(pag, XFS_AG_RESV_RMAPBT); 172 err2 = __xfs_ag_resv_free(pag, XFS_AG_RESV_METADATA); 173 if (err2 && !error) 174 error = err2; 175 return error; 176 } 177 178 static int 179 __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 struct xfs_mount *mp = pag->pag_mount; 186 struct xfs_ag_resv *resv; 187 int error; 188 xfs_extlen_t hidden_space; 189 190 if (used > ask) 191 ask = used; 192 193 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 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 hidden_space = ask - used; 210 break; 211 default: 212 ASSERT(0); 213 return -EINVAL; 214 } 215 216 if (XFS_TEST_ERROR(false, mp, XFS_ERRTAG_AG_RESV_FAIL)) 217 error = -ENOSPC; 218 else 219 error = xfs_mod_fdblocks(mp, -(int64_t)hidden_space, true); 220 if (error) { 221 trace_xfs_ag_resv_init_error(pag->pag_mount, pag->pag_agno, 222 error, _RET_IP_); 223 xfs_warn(mp, 224 "Per-AG reservation for AG %u failed. Filesystem may run out of space.", 225 pag->pag_agno); 226 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 if (pag->pag_agno == 0) 236 mp->m_ag_max_usable -= ask; 237 238 resv = xfs_perag_resv(pag, type); 239 resv->ar_asked = ask; 240 resv->ar_orig_reserved = hidden_space; 241 resv->ar_reserved = ask - used; 242 243 trace_xfs_ag_resv_init(pag, type, ask); 244 return 0; 245 } 246 247 /* Create a per-AG block reservation. */ 248 int 249 xfs_ag_resv_init( 250 struct xfs_perag *pag, 251 struct xfs_trans *tp) 252 { 253 struct xfs_mount *mp = pag->pag_mount; 254 xfs_extlen_t ask; 255 xfs_extlen_t used; 256 int error = 0, error2; 257 bool has_resv = false; 258 259 /* Create the metadata reservation. */ 260 if (pag->pag_meta_resv.ar_asked == 0) { 261 ask = used = 0; 262 263 error = xfs_refcountbt_calc_reserves(mp, tp, pag, &ask, &used); 264 if (error) 265 goto out; 266 267 error = xfs_finobt_calc_reserves(mp, tp, pag, &ask, &used); 268 if (error) 269 goto out; 270 271 error = __xfs_ag_resv_init(pag, XFS_AG_RESV_METADATA, 272 ask, used); 273 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 ask = used = 0; 282 283 mp->m_finobt_nores = true; 284 285 error = xfs_refcountbt_calc_reserves(mp, tp, pag, &ask, 286 &used); 287 if (error) 288 goto out; 289 290 error = __xfs_ag_resv_init(pag, XFS_AG_RESV_METADATA, 291 ask, used); 292 if (error) 293 goto out; 294 } 295 if (ask) 296 has_resv = true; 297 } 298 299 /* Create the RMAPBT metadata reservation */ 300 if (pag->pag_rmapbt_resv.ar_asked == 0) { 301 ask = used = 0; 302 303 error = xfs_rmapbt_calc_reserves(mp, tp, pag, &ask, &used); 304 if (error) 305 goto out; 306 307 error = __xfs_ag_resv_init(pag, XFS_AG_RESV_RMAPBT, ask, used); 308 if (error) 309 goto out; 310 if (ask) 311 has_resv = true; 312 } 313 314 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 if (has_resv) { 325 error2 = xfs_alloc_pagf_init(mp, tp, pag->pag_agno, 0); 326 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 if (!error && 338 xfs_perag_resv(pag, XFS_AG_RESV_METADATA)->ar_reserved + 339 xfs_perag_resv(pag, XFS_AG_RESV_RMAPBT)->ar_reserved > 340 pag->pagf_freeblks + pag->pagf_flcount) 341 error = -ENOSPC; 342 } 343 344 return error; 345 } 346 347 /* Allocate a block from the reservation. */ 348 void 349 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 struct xfs_ag_resv *resv; 355 xfs_extlen_t len; 356 uint field; 357 358 trace_xfs_ag_resv_alloc_extent(pag, type, args->len); 359 360 switch (type) { 361 case XFS_AG_RESV_AGFL: 362 return; 363 case XFS_AG_RESV_METADATA: 364 case XFS_AG_RESV_RMAPBT: 365 resv = xfs_perag_resv(pag, type); 366 break; 367 default: 368 ASSERT(0); 369 fallthrough; 370 case XFS_AG_RESV_NONE: 371 field = args->wasdel ? XFS_TRANS_SB_RES_FDBLOCKS : 372 XFS_TRANS_SB_FDBLOCKS; 373 xfs_trans_mod_sb(args->tp, field, -(int64_t)args->len); 374 return; 375 } 376 377 len = min_t(xfs_extlen_t, args->len, resv->ar_reserved); 378 resv->ar_reserved -= len; 379 if (type == XFS_AG_RESV_RMAPBT) 380 return; 381 /* Allocations of reserved blocks only need on-disk sb updates... */ 382 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 if (args->len > len) 385 xfs_trans_mod_sb(args->tp, XFS_TRANS_SB_FDBLOCKS, 386 -((int64_t)args->len - len)); 387 } 388 389 /* Free a block to the reservation. */ 390 void 391 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 xfs_extlen_t leftover; 398 struct xfs_ag_resv *resv; 399 400 trace_xfs_ag_resv_free_extent(pag, type, len); 401 402 switch (type) { 403 case XFS_AG_RESV_AGFL: 404 return; 405 case XFS_AG_RESV_METADATA: 406 case XFS_AG_RESV_RMAPBT: 407 resv = xfs_perag_resv(pag, type); 408 break; 409 default: 410 ASSERT(0); 411 fallthrough; 412 case XFS_AG_RESV_NONE: 413 xfs_trans_mod_sb(tp, XFS_TRANS_SB_FDBLOCKS, (int64_t)len); 414 return; 415 } 416 417 leftover = min_t(xfs_extlen_t, len, resv->ar_asked - resv->ar_reserved); 418 resv->ar_reserved += leftover; 419 if (type == XFS_AG_RESV_RMAPBT) 420 return; 421 /* Freeing into the reserved pool only requires on-disk update... */ 422 xfs_trans_mod_sb(tp, XFS_TRANS_SB_RES_FDBLOCKS, len); 423 /* ...but freeing beyond that requires in-core and on-disk update. */ 424 if (len > leftover) 425 xfs_trans_mod_sb(tp, XFS_TRANS_SB_FDBLOCKS, len - leftover); 426 } 427