1 // SPDX-License-Identifier: GPL-2.0+ 2 /* 3 * Copyright (C) 2019 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_trans_resv.h" 11 #include "xfs_mount.h" 12 #include "xfs_alloc.h" 13 #include "xfs_ialloc.h" 14 #include "xfs_health.h" 15 #include "xfs_btree.h" 16 #include "xfs_ag.h" 17 #include "xfs_rtalloc.h" 18 #include "xfs_inode.h" 19 #include "scrub/scrub.h" 20 #include "scrub/common.h" 21 #include "scrub/trace.h" 22 23 /* 24 * FS Summary Counters 25 * =================== 26 * 27 * The basics of filesystem summary counter checking are that we iterate the 28 * AGs counting the number of free blocks, free space btree blocks, per-AG 29 * reservations, inodes, delayed allocation reservations, and free inodes. 30 * Then we compare what we computed against the in-core counters. 31 * 32 * However, the reality is that summary counters are a tricky beast to check. 33 * While we /could/ freeze the filesystem and scramble around the AGs counting 34 * the free blocks, in practice we prefer not do that for a scan because 35 * freezing is costly. To get around this, we added a per-cpu counter of the 36 * delalloc reservations so that we can rotor around the AGs relatively 37 * quickly, and we allow the counts to be slightly off because we're not taking 38 * any locks while we do this. 39 * 40 * So the first thing we do is warm up the buffer cache in the setup routine by 41 * walking all the AGs to make sure the incore per-AG structure has been 42 * initialized. The expected value calculation then iterates the incore per-AG 43 * structures as quickly as it can. We snapshot the percpu counters before and 44 * after this operation and use the difference in counter values to guess at 45 * our tolerance for mismatch between expected and actual counter values. 46 */ 47 48 struct xchk_fscounters { 49 struct xfs_scrub *sc; 50 uint64_t icount; 51 uint64_t ifree; 52 uint64_t fdblocks; 53 uint64_t frextents; 54 unsigned long long icount_min; 55 unsigned long long icount_max; 56 }; 57 58 /* 59 * Since the expected value computation is lockless but only browses incore 60 * values, the percpu counters should be fairly close to each other. However, 61 * we'll allow ourselves to be off by at least this (arbitrary) amount. 62 */ 63 #define XCHK_FSCOUNT_MIN_VARIANCE (512) 64 65 /* 66 * Make sure the per-AG structure has been initialized from the on-disk header 67 * contents and trust that the incore counters match the ondisk counters. (The 68 * AGF and AGI scrubbers check them, and a normal xfs_scrub run checks the 69 * summary counters after checking all AG headers). Do this from the setup 70 * function so that the inner AG aggregation loop runs as quickly as possible. 71 * 72 * This function runs during the setup phase /before/ we start checking any 73 * metadata. 74 */ 75 STATIC int 76 xchk_fscount_warmup( 77 struct xfs_scrub *sc) 78 { 79 struct xfs_mount *mp = sc->mp; 80 struct xfs_buf *agi_bp = NULL; 81 struct xfs_buf *agf_bp = NULL; 82 struct xfs_perag *pag = NULL; 83 xfs_agnumber_t agno; 84 int error = 0; 85 86 for_each_perag(mp, agno, pag) { 87 if (xchk_should_terminate(sc, &error)) 88 break; 89 if (pag->pagi_init && pag->pagf_init) 90 continue; 91 92 /* Lock both AG headers. */ 93 error = xfs_ialloc_read_agi(pag, sc->tp, &agi_bp); 94 if (error) 95 break; 96 error = xfs_alloc_read_agf(pag, sc->tp, 0, &agf_bp); 97 if (error) 98 break; 99 100 /* 101 * These are supposed to be initialized by the header read 102 * function. 103 */ 104 if (!pag->pagi_init || !pag->pagf_init) { 105 error = -EFSCORRUPTED; 106 break; 107 } 108 109 xfs_buf_relse(agf_bp); 110 agf_bp = NULL; 111 xfs_buf_relse(agi_bp); 112 agi_bp = NULL; 113 } 114 115 if (agf_bp) 116 xfs_buf_relse(agf_bp); 117 if (agi_bp) 118 xfs_buf_relse(agi_bp); 119 if (pag) 120 xfs_perag_put(pag); 121 return error; 122 } 123 124 int 125 xchk_setup_fscounters( 126 struct xfs_scrub *sc) 127 { 128 struct xchk_fscounters *fsc; 129 int error; 130 131 sc->buf = kzalloc(sizeof(struct xchk_fscounters), XCHK_GFP_FLAGS); 132 if (!sc->buf) 133 return -ENOMEM; 134 fsc = sc->buf; 135 fsc->sc = sc; 136 137 xfs_icount_range(sc->mp, &fsc->icount_min, &fsc->icount_max); 138 139 /* We must get the incore counters set up before we can proceed. */ 140 error = xchk_fscount_warmup(sc); 141 if (error) 142 return error; 143 144 /* 145 * Pause background reclaim while we're scrubbing to reduce the 146 * likelihood of background perturbations to the counters throwing off 147 * our calculations. 148 */ 149 xchk_stop_reaping(sc); 150 151 return xchk_trans_alloc(sc, 0); 152 } 153 154 /* 155 * Part 1: Collecting filesystem summary counts. For each AG, we add its 156 * summary counts (total inodes, free inodes, free data blocks) to an incore 157 * copy of the overall filesystem summary counts. 158 * 159 * To avoid false corruption reports in part 2, any failure in this part must 160 * set the INCOMPLETE flag even when a negative errno is returned. This care 161 * must be taken with certain errno values (i.e. EFSBADCRC, EFSCORRUPTED, 162 * ECANCELED) that are absorbed into a scrub state flag update by 163 * xchk_*_process_error. 164 */ 165 166 /* Count free space btree blocks manually for pre-lazysbcount filesystems. */ 167 static int 168 xchk_fscount_btreeblks( 169 struct xfs_scrub *sc, 170 struct xchk_fscounters *fsc, 171 xfs_agnumber_t agno) 172 { 173 xfs_extlen_t blocks; 174 int error; 175 176 error = xchk_ag_init_existing(sc, agno, &sc->sa); 177 if (error) 178 goto out_free; 179 180 error = xfs_btree_count_blocks(sc->sa.bno_cur, &blocks); 181 if (error) 182 goto out_free; 183 fsc->fdblocks += blocks - 1; 184 185 error = xfs_btree_count_blocks(sc->sa.cnt_cur, &blocks); 186 if (error) 187 goto out_free; 188 fsc->fdblocks += blocks - 1; 189 190 out_free: 191 xchk_ag_free(sc, &sc->sa); 192 return error; 193 } 194 195 /* 196 * Calculate what the global in-core counters ought to be from the incore 197 * per-AG structure. Callers can compare this to the actual in-core counters 198 * to estimate by how much both in-core and on-disk counters need to be 199 * adjusted. 200 */ 201 STATIC int 202 xchk_fscount_aggregate_agcounts( 203 struct xfs_scrub *sc, 204 struct xchk_fscounters *fsc) 205 { 206 struct xfs_mount *mp = sc->mp; 207 struct xfs_perag *pag; 208 uint64_t delayed; 209 xfs_agnumber_t agno; 210 int tries = 8; 211 int error = 0; 212 213 retry: 214 fsc->icount = 0; 215 fsc->ifree = 0; 216 fsc->fdblocks = 0; 217 218 for_each_perag(mp, agno, pag) { 219 if (xchk_should_terminate(sc, &error)) 220 break; 221 222 /* This somehow got unset since the warmup? */ 223 if (!pag->pagi_init || !pag->pagf_init) { 224 error = -EFSCORRUPTED; 225 break; 226 } 227 228 /* Count all the inodes */ 229 fsc->icount += pag->pagi_count; 230 fsc->ifree += pag->pagi_freecount; 231 232 /* Add up the free/freelist/bnobt/cntbt blocks */ 233 fsc->fdblocks += pag->pagf_freeblks; 234 fsc->fdblocks += pag->pagf_flcount; 235 if (xfs_has_lazysbcount(sc->mp)) { 236 fsc->fdblocks += pag->pagf_btreeblks; 237 } else { 238 error = xchk_fscount_btreeblks(sc, fsc, agno); 239 if (error) 240 break; 241 } 242 243 /* 244 * Per-AG reservations are taken out of the incore counters, 245 * so they must be left out of the free blocks computation. 246 */ 247 fsc->fdblocks -= pag->pag_meta_resv.ar_reserved; 248 fsc->fdblocks -= pag->pag_rmapbt_resv.ar_orig_reserved; 249 250 } 251 if (pag) 252 xfs_perag_put(pag); 253 if (error) { 254 xchk_set_incomplete(sc); 255 return error; 256 } 257 258 /* 259 * The global incore space reservation is taken from the incore 260 * counters, so leave that out of the computation. 261 */ 262 fsc->fdblocks -= mp->m_resblks_avail; 263 264 /* 265 * Delayed allocation reservations are taken out of the incore counters 266 * but not recorded on disk, so leave them and their indlen blocks out 267 * of the computation. 268 */ 269 delayed = percpu_counter_sum(&mp->m_delalloc_blks); 270 fsc->fdblocks -= delayed; 271 272 trace_xchk_fscounters_calc(mp, fsc->icount, fsc->ifree, fsc->fdblocks, 273 delayed); 274 275 276 /* Bail out if the values we compute are totally nonsense. */ 277 if (fsc->icount < fsc->icount_min || fsc->icount > fsc->icount_max || 278 fsc->fdblocks > mp->m_sb.sb_dblocks || 279 fsc->ifree > fsc->icount_max) 280 return -EFSCORRUPTED; 281 282 /* 283 * If ifree > icount then we probably had some perturbation in the 284 * counters while we were calculating things. We'll try a few times 285 * to maintain ifree <= icount before giving up. 286 */ 287 if (fsc->ifree > fsc->icount) { 288 if (tries--) 289 goto retry; 290 xchk_set_incomplete(sc); 291 return 0; 292 } 293 294 return 0; 295 } 296 297 #ifdef CONFIG_XFS_RT 298 STATIC int 299 xchk_fscount_add_frextent( 300 struct xfs_mount *mp, 301 struct xfs_trans *tp, 302 const struct xfs_rtalloc_rec *rec, 303 void *priv) 304 { 305 struct xchk_fscounters *fsc = priv; 306 int error = 0; 307 308 fsc->frextents += rec->ar_extcount; 309 310 xchk_should_terminate(fsc->sc, &error); 311 return error; 312 } 313 314 /* Calculate the number of free realtime extents from the realtime bitmap. */ 315 STATIC int 316 xchk_fscount_count_frextents( 317 struct xfs_scrub *sc, 318 struct xchk_fscounters *fsc) 319 { 320 struct xfs_mount *mp = sc->mp; 321 int error; 322 323 fsc->frextents = 0; 324 if (!xfs_has_realtime(mp)) 325 return 0; 326 327 xfs_ilock(sc->mp->m_rbmip, XFS_ILOCK_SHARED | XFS_ILOCK_RTBITMAP); 328 error = xfs_rtalloc_query_all(sc->mp, sc->tp, 329 xchk_fscount_add_frextent, fsc); 330 if (error) { 331 xchk_set_incomplete(sc); 332 goto out_unlock; 333 } 334 335 out_unlock: 336 xfs_iunlock(sc->mp->m_rbmip, XFS_ILOCK_SHARED | XFS_ILOCK_RTBITMAP); 337 return error; 338 } 339 #else 340 STATIC int 341 xchk_fscount_count_frextents( 342 struct xfs_scrub *sc, 343 struct xchk_fscounters *fsc) 344 { 345 fsc->frextents = 0; 346 return 0; 347 } 348 #endif /* CONFIG_XFS_RT */ 349 350 /* 351 * Part 2: Comparing filesystem summary counters. All we have to do here is 352 * sum the percpu counters and compare them to what we've observed. 353 */ 354 355 /* 356 * Is the @counter reasonably close to the @expected value? 357 * 358 * We neither locked nor froze anything in the filesystem while aggregating the 359 * per-AG data to compute the @expected value, which means that the counter 360 * could have changed. We know the @old_value of the summation of the counter 361 * before the aggregation, and we re-sum the counter now. If the expected 362 * value falls between the two summations, we're ok. 363 * 364 * Otherwise, we /might/ have a problem. If the change in the summations is 365 * more than we want to tolerate, the filesystem is probably busy and we should 366 * just send back INCOMPLETE and see if userspace will try again. 367 */ 368 static inline bool 369 xchk_fscount_within_range( 370 struct xfs_scrub *sc, 371 const int64_t old_value, 372 struct percpu_counter *counter, 373 uint64_t expected) 374 { 375 int64_t min_value, max_value; 376 int64_t curr_value = percpu_counter_sum(counter); 377 378 trace_xchk_fscounters_within_range(sc->mp, expected, curr_value, 379 old_value); 380 381 /* Negative values are always wrong. */ 382 if (curr_value < 0) 383 return false; 384 385 /* Exact matches are always ok. */ 386 if (curr_value == expected) 387 return true; 388 389 min_value = min(old_value, curr_value); 390 max_value = max(old_value, curr_value); 391 392 /* Within the before-and-after range is ok. */ 393 if (expected >= min_value && expected <= max_value) 394 return true; 395 396 /* 397 * If the difference between the two summations is too large, the fs 398 * might just be busy and so we'll mark the scrub incomplete. Return 399 * true here so that we don't mark the counter corrupt. 400 * 401 * XXX: In the future when userspace can grant scrub permission to 402 * quiesce the filesystem to solve the outsized variance problem, this 403 * check should be moved up and the return code changed to signal to 404 * userspace that we need quiesce permission. 405 */ 406 if (max_value - min_value >= XCHK_FSCOUNT_MIN_VARIANCE) { 407 xchk_set_incomplete(sc); 408 return true; 409 } 410 411 return false; 412 } 413 414 /* Check the superblock counters. */ 415 int 416 xchk_fscounters( 417 struct xfs_scrub *sc) 418 { 419 struct xfs_mount *mp = sc->mp; 420 struct xchk_fscounters *fsc = sc->buf; 421 int64_t icount, ifree, fdblocks, frextents; 422 int error; 423 424 /* Snapshot the percpu counters. */ 425 icount = percpu_counter_sum(&mp->m_icount); 426 ifree = percpu_counter_sum(&mp->m_ifree); 427 fdblocks = percpu_counter_sum(&mp->m_fdblocks); 428 frextents = percpu_counter_sum(&mp->m_frextents); 429 430 /* No negative values, please! */ 431 if (icount < 0 || ifree < 0 || fdblocks < 0 || frextents < 0) 432 xchk_set_corrupt(sc); 433 434 /* See if icount is obviously wrong. */ 435 if (icount < fsc->icount_min || icount > fsc->icount_max) 436 xchk_set_corrupt(sc); 437 438 /* See if fdblocks is obviously wrong. */ 439 if (fdblocks > mp->m_sb.sb_dblocks) 440 xchk_set_corrupt(sc); 441 442 /* See if frextents is obviously wrong. */ 443 if (frextents > mp->m_sb.sb_rextents) 444 xchk_set_corrupt(sc); 445 446 /* 447 * If ifree exceeds icount by more than the minimum variance then 448 * something's probably wrong with the counters. 449 */ 450 if (ifree > icount && ifree - icount > XCHK_FSCOUNT_MIN_VARIANCE) 451 xchk_set_corrupt(sc); 452 453 /* Walk the incore AG headers to calculate the expected counters. */ 454 error = xchk_fscount_aggregate_agcounts(sc, fsc); 455 if (!xchk_process_error(sc, 0, XFS_SB_BLOCK(mp), &error)) 456 return error; 457 if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_INCOMPLETE) 458 return 0; 459 460 /* Count the free extents counter for rt volumes. */ 461 error = xchk_fscount_count_frextents(sc, fsc); 462 if (!xchk_process_error(sc, 0, XFS_SB_BLOCK(mp), &error)) 463 return error; 464 if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_INCOMPLETE) 465 return 0; 466 467 /* Compare the in-core counters with whatever we counted. */ 468 if (!xchk_fscount_within_range(sc, icount, &mp->m_icount, fsc->icount)) 469 xchk_set_corrupt(sc); 470 471 if (!xchk_fscount_within_range(sc, ifree, &mp->m_ifree, fsc->ifree)) 472 xchk_set_corrupt(sc); 473 474 if (!xchk_fscount_within_range(sc, fdblocks, &mp->m_fdblocks, 475 fsc->fdblocks)) 476 xchk_set_corrupt(sc); 477 478 if (!xchk_fscount_within_range(sc, frextents, &mp->m_frextents, 479 fsc->frextents)) 480 xchk_set_corrupt(sc); 481 482 return 0; 483 } 484