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 struct xfs_mount *mp = pag_mount(pag); 74 xfs_extlen_t avail; 75 xfs_extlen_t orig; 76 77 switch (type) { 78 case XFS_AG_RESV_METADATA: 79 avail = pag->pagf_freeblks - pag->pag_rmapbt_resv.ar_reserved; 80 orig = pag->pag_meta_resv.ar_asked; 81 break; 82 case XFS_AG_RESV_RMAPBT: 83 avail = pag->pagf_freeblks + pag->pagf_flcount - 84 pag->pag_meta_resv.ar_reserved; 85 orig = pag->pag_rmapbt_resv.ar_asked; 86 break; 87 default: 88 ASSERT(0); 89 return false; 90 } 91 92 trace_xfs_ag_resv_critical(pag, type, avail); 93 94 /* Critically low if less than 10% or max btree height remains. */ 95 return XFS_TEST_ERROR(avail < orig / 10 || 96 avail < mp->m_agbtree_maxlevels, 97 mp, XFS_ERRTAG_AG_RESV_CRITICAL); 98 } 99 100 /* 101 * How many blocks are reserved but not used, and therefore must not be 102 * allocated away? 103 */ 104 xfs_extlen_t 105 xfs_ag_resv_needed( 106 struct xfs_perag *pag, 107 enum xfs_ag_resv_type type) 108 { 109 xfs_extlen_t len; 110 111 len = pag->pag_meta_resv.ar_reserved + pag->pag_rmapbt_resv.ar_reserved; 112 switch (type) { 113 case XFS_AG_RESV_METADATA: 114 case XFS_AG_RESV_RMAPBT: 115 len -= xfs_perag_resv(pag, type)->ar_reserved; 116 break; 117 case XFS_AG_RESV_NONE: 118 /* empty */ 119 break; 120 default: 121 ASSERT(0); 122 } 123 124 trace_xfs_ag_resv_needed(pag, type, len); 125 126 return len; 127 } 128 129 /* Clean out a reservation */ 130 static void 131 __xfs_ag_resv_free( 132 struct xfs_perag *pag, 133 enum xfs_ag_resv_type type) 134 { 135 struct xfs_ag_resv *resv; 136 xfs_extlen_t oldresv; 137 138 trace_xfs_ag_resv_free(pag, type, 0); 139 140 resv = xfs_perag_resv(pag, type); 141 if (pag_agno(pag) == 0) 142 pag_mount(pag)->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 xfs_add_fdblocks(pag_mount(pag), oldresv); 153 resv->ar_reserved = 0; 154 resv->ar_asked = 0; 155 resv->ar_orig_reserved = 0; 156 } 157 158 /* Free a per-AG reservation. */ 159 void 160 xfs_ag_resv_free( 161 struct xfs_perag *pag) 162 { 163 __xfs_ag_resv_free(pag, XFS_AG_RESV_RMAPBT); 164 __xfs_ag_resv_free(pag, XFS_AG_RESV_METADATA); 165 } 166 167 static int 168 __xfs_ag_resv_init( 169 struct xfs_perag *pag, 170 enum xfs_ag_resv_type type, 171 xfs_extlen_t ask, 172 xfs_extlen_t used) 173 { 174 struct xfs_mount *mp = pag_mount(pag); 175 struct xfs_ag_resv *resv; 176 int error; 177 xfs_extlen_t hidden_space; 178 179 if (used > ask) 180 ask = used; 181 182 switch (type) { 183 case XFS_AG_RESV_RMAPBT: 184 /* 185 * Space taken by the rmapbt is not subtracted from fdblocks 186 * because the rmapbt lives in the free space. Here we must 187 * subtract the entire reservation from fdblocks so that we 188 * always have blocks available for rmapbt expansion. 189 */ 190 hidden_space = ask; 191 break; 192 case XFS_AG_RESV_METADATA: 193 /* 194 * Space taken by all other metadata btrees are accounted 195 * on-disk as used space. We therefore only hide the space 196 * that is reserved but not used by the trees. 197 */ 198 hidden_space = ask - used; 199 break; 200 default: 201 ASSERT(0); 202 return -EINVAL; 203 } 204 205 if (XFS_TEST_ERROR(false, mp, XFS_ERRTAG_AG_RESV_FAIL)) 206 error = -ENOSPC; 207 else 208 error = xfs_dec_fdblocks(mp, hidden_space, true); 209 if (error) { 210 trace_xfs_ag_resv_init_error(pag, error, _RET_IP_); 211 xfs_warn(mp, 212 "Per-AG reservation for AG %u failed. Filesystem may run out of space.", 213 pag_agno(pag)); 214 return error; 215 } 216 217 /* 218 * Reduce the maximum per-AG allocation length by however much we're 219 * trying to reserve for an AG. Since this is a filesystem-wide 220 * counter, we only make the adjustment for AG 0. This assumes that 221 * there aren't any AGs hungrier for per-AG reservation than AG 0. 222 */ 223 if (pag_agno(pag) == 0) 224 mp->m_ag_max_usable -= ask; 225 226 resv = xfs_perag_resv(pag, type); 227 resv->ar_asked = ask; 228 resv->ar_orig_reserved = hidden_space; 229 resv->ar_reserved = ask - used; 230 231 trace_xfs_ag_resv_init(pag, type, ask); 232 return 0; 233 } 234 235 /* Create a per-AG block reservation. */ 236 int 237 xfs_ag_resv_init( 238 struct xfs_perag *pag, 239 struct xfs_trans *tp) 240 { 241 struct xfs_mount *mp = pag_mount(pag); 242 xfs_extlen_t ask; 243 xfs_extlen_t used; 244 int error = 0, error2; 245 bool has_resv = false; 246 247 /* Create the metadata reservation. */ 248 if (pag->pag_meta_resv.ar_asked == 0) { 249 ask = used = 0; 250 251 error = xfs_refcountbt_calc_reserves(mp, tp, pag, &ask, &used); 252 if (error) 253 goto out; 254 255 error = xfs_finobt_calc_reserves(pag, tp, &ask, &used); 256 if (error) 257 goto out; 258 259 error = __xfs_ag_resv_init(pag, XFS_AG_RESV_METADATA, 260 ask, used); 261 if (error) { 262 /* 263 * Because we didn't have per-AG reservations when the 264 * finobt feature was added we might not be able to 265 * reserve all needed blocks. Warn and fall back to the 266 * old and potentially buggy code in that case, but 267 * ensure we do have the reservation for the refcountbt. 268 */ 269 ask = used = 0; 270 271 mp->m_finobt_nores = true; 272 273 error = xfs_refcountbt_calc_reserves(mp, tp, pag, &ask, 274 &used); 275 if (error) 276 goto out; 277 278 error = __xfs_ag_resv_init(pag, XFS_AG_RESV_METADATA, 279 ask, used); 280 if (error) 281 goto out; 282 } 283 if (ask) 284 has_resv = true; 285 } 286 287 /* Create the RMAPBT metadata reservation */ 288 if (pag->pag_rmapbt_resv.ar_asked == 0) { 289 ask = used = 0; 290 291 error = xfs_rmapbt_calc_reserves(mp, tp, pag, &ask, &used); 292 if (error) 293 goto out; 294 295 error = __xfs_ag_resv_init(pag, XFS_AG_RESV_RMAPBT, ask, used); 296 if (error) 297 goto out; 298 if (ask) 299 has_resv = true; 300 } 301 302 out: 303 /* 304 * Initialize the pagf if we have at least one active reservation on the 305 * AG. This may have occurred already via reservation calculation, but 306 * fall back to an explicit init to ensure the in-core allocbt usage 307 * counters are initialized as soon as possible. This is important 308 * because filesystems with large perag reservations are susceptible to 309 * free space reservation problems that the allocbt counter is used to 310 * address. 311 */ 312 if (has_resv) { 313 error2 = xfs_alloc_read_agf(pag, tp, 0, NULL); 314 if (error2) 315 return error2; 316 317 /* 318 * If there isn't enough space in the AG to satisfy the 319 * reservation, let the caller know that there wasn't enough 320 * space. Callers are responsible for deciding what to do 321 * next, since (in theory) we can stumble along with 322 * insufficient reservation if data blocks are being freed to 323 * replenish the AG's free space. 324 */ 325 if (!error && 326 xfs_perag_resv(pag, XFS_AG_RESV_METADATA)->ar_reserved + 327 xfs_perag_resv(pag, XFS_AG_RESV_RMAPBT)->ar_reserved > 328 pag->pagf_freeblks + pag->pagf_flcount) 329 error = -ENOSPC; 330 } 331 332 return error; 333 } 334 335 /* Allocate a block from the reservation. */ 336 void 337 xfs_ag_resv_alloc_extent( 338 struct xfs_perag *pag, 339 enum xfs_ag_resv_type type, 340 struct xfs_alloc_arg *args) 341 { 342 struct xfs_ag_resv *resv; 343 xfs_extlen_t len; 344 uint field; 345 346 trace_xfs_ag_resv_alloc_extent(pag, type, args->len); 347 348 switch (type) { 349 case XFS_AG_RESV_AGFL: 350 return; 351 case XFS_AG_RESV_METADATA: 352 case XFS_AG_RESV_RMAPBT: 353 resv = xfs_perag_resv(pag, type); 354 break; 355 default: 356 ASSERT(0); 357 fallthrough; 358 case XFS_AG_RESV_NONE: 359 field = args->wasdel ? XFS_TRANS_SB_RES_FDBLOCKS : 360 XFS_TRANS_SB_FDBLOCKS; 361 xfs_trans_mod_sb(args->tp, field, -(int64_t)args->len); 362 return; 363 } 364 365 len = min_t(xfs_extlen_t, args->len, resv->ar_reserved); 366 resv->ar_reserved -= len; 367 if (type == XFS_AG_RESV_RMAPBT) 368 return; 369 /* Allocations of reserved blocks only need on-disk sb updates... */ 370 xfs_trans_mod_sb(args->tp, XFS_TRANS_SB_RES_FDBLOCKS, -(int64_t)len); 371 /* ...but non-reserved blocks need in-core and on-disk updates. */ 372 if (args->len > len) 373 xfs_trans_mod_sb(args->tp, XFS_TRANS_SB_FDBLOCKS, 374 -((int64_t)args->len - len)); 375 } 376 377 /* Free a block to the reservation. */ 378 void 379 xfs_ag_resv_free_extent( 380 struct xfs_perag *pag, 381 enum xfs_ag_resv_type type, 382 struct xfs_trans *tp, 383 xfs_extlen_t len) 384 { 385 xfs_extlen_t leftover; 386 struct xfs_ag_resv *resv; 387 388 trace_xfs_ag_resv_free_extent(pag, type, len); 389 390 switch (type) { 391 case XFS_AG_RESV_AGFL: 392 return; 393 case XFS_AG_RESV_METADATA: 394 case XFS_AG_RESV_RMAPBT: 395 resv = xfs_perag_resv(pag, type); 396 break; 397 default: 398 ASSERT(0); 399 fallthrough; 400 case XFS_AG_RESV_NONE: 401 xfs_trans_mod_sb(tp, XFS_TRANS_SB_FDBLOCKS, (int64_t)len); 402 fallthrough; 403 case XFS_AG_RESV_IGNORE: 404 return; 405 } 406 407 leftover = min_t(xfs_extlen_t, len, resv->ar_asked - resv->ar_reserved); 408 resv->ar_reserved += leftover; 409 if (type == XFS_AG_RESV_RMAPBT) 410 return; 411 /* Freeing into the reserved pool only requires on-disk update... */ 412 xfs_trans_mod_sb(tp, XFS_TRANS_SB_RES_FDBLOCKS, len); 413 /* ...but freeing beyond that requires in-core and on-disk update. */ 414 if (len > leftover) 415 xfs_trans_mod_sb(tp, XFS_TRANS_SB_FDBLOCKS, len - leftover); 416 } 417