1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Copyright (c) 2000-2002,2005 Silicon Graphics, Inc. 4 * Copyright (c) 2010 David Chinner. 5 * Copyright (c) 2011 Christoph Hellwig. 6 * All Rights Reserved. 7 */ 8 #include "xfs.h" 9 #include "xfs_fs.h" 10 #include "xfs_format.h" 11 #include "xfs_log_format.h" 12 #include "xfs_shared.h" 13 #include "xfs_trans_resv.h" 14 #include "xfs_mount.h" 15 #include "xfs_alloc.h" 16 #include "xfs_extent_busy.h" 17 #include "xfs_trace.h" 18 #include "xfs_trans.h" 19 #include "xfs_log.h" 20 #include "xfs_ag.h" 21 22 void 23 xfs_extent_busy_insert( 24 struct xfs_trans *tp, 25 struct xfs_perag *pag, 26 xfs_agblock_t bno, 27 xfs_extlen_t len, 28 unsigned int flags) 29 { 30 struct xfs_extent_busy *new; 31 struct xfs_extent_busy *busyp; 32 struct rb_node **rbp; 33 struct rb_node *parent = NULL; 34 35 new = kmem_zalloc(sizeof(struct xfs_extent_busy), 0); 36 new->agno = pag->pag_agno; 37 new->bno = bno; 38 new->length = len; 39 INIT_LIST_HEAD(&new->list); 40 new->flags = flags; 41 42 /* trace before insert to be able to see failed inserts */ 43 trace_xfs_extent_busy(tp->t_mountp, pag->pag_agno, bno, len); 44 45 spin_lock(&pag->pagb_lock); 46 rbp = &pag->pagb_tree.rb_node; 47 while (*rbp) { 48 parent = *rbp; 49 busyp = rb_entry(parent, struct xfs_extent_busy, rb_node); 50 51 if (new->bno < busyp->bno) { 52 rbp = &(*rbp)->rb_left; 53 ASSERT(new->bno + new->length <= busyp->bno); 54 } else if (new->bno > busyp->bno) { 55 rbp = &(*rbp)->rb_right; 56 ASSERT(bno >= busyp->bno + busyp->length); 57 } else { 58 ASSERT(0); 59 } 60 } 61 62 rb_link_node(&new->rb_node, parent, rbp); 63 rb_insert_color(&new->rb_node, &pag->pagb_tree); 64 65 list_add(&new->list, &tp->t_busy); 66 spin_unlock(&pag->pagb_lock); 67 } 68 69 /* 70 * Search for a busy extent within the range of the extent we are about to 71 * allocate. You need to be holding the busy extent tree lock when calling 72 * xfs_extent_busy_search(). This function returns 0 for no overlapping busy 73 * extent, -1 for an overlapping but not exact busy extent, and 1 for an exact 74 * match. This is done so that a non-zero return indicates an overlap that 75 * will require a synchronous transaction, but it can still be 76 * used to distinguish between a partial or exact match. 77 */ 78 int 79 xfs_extent_busy_search( 80 struct xfs_mount *mp, 81 struct xfs_perag *pag, 82 xfs_agblock_t bno, 83 xfs_extlen_t len) 84 { 85 struct rb_node *rbp; 86 struct xfs_extent_busy *busyp; 87 int match = 0; 88 89 /* find closest start bno overlap */ 90 spin_lock(&pag->pagb_lock); 91 rbp = pag->pagb_tree.rb_node; 92 while (rbp) { 93 busyp = rb_entry(rbp, struct xfs_extent_busy, rb_node); 94 if (bno < busyp->bno) { 95 /* may overlap, but exact start block is lower */ 96 if (bno + len > busyp->bno) 97 match = -1; 98 rbp = rbp->rb_left; 99 } else if (bno > busyp->bno) { 100 /* may overlap, but exact start block is higher */ 101 if (bno < busyp->bno + busyp->length) 102 match = -1; 103 rbp = rbp->rb_right; 104 } else { 105 /* bno matches busyp, length determines exact match */ 106 match = (busyp->length == len) ? 1 : -1; 107 break; 108 } 109 } 110 spin_unlock(&pag->pagb_lock); 111 return match; 112 } 113 114 /* 115 * The found free extent [fbno, fend] overlaps part or all of the given busy 116 * extent. If the overlap covers the beginning, the end, or all of the busy 117 * extent, the overlapping portion can be made unbusy and used for the 118 * allocation. We can't split a busy extent because we can't modify a 119 * transaction/CIL context busy list, but we can update an entry's block 120 * number or length. 121 * 122 * Returns true if the extent can safely be reused, or false if the search 123 * needs to be restarted. 124 */ 125 STATIC bool 126 xfs_extent_busy_update_extent( 127 struct xfs_mount *mp, 128 struct xfs_perag *pag, 129 struct xfs_extent_busy *busyp, 130 xfs_agblock_t fbno, 131 xfs_extlen_t flen, 132 bool userdata) __releases(&pag->pagb_lock) 133 __acquires(&pag->pagb_lock) 134 { 135 xfs_agblock_t fend = fbno + flen; 136 xfs_agblock_t bbno = busyp->bno; 137 xfs_agblock_t bend = bbno + busyp->length; 138 139 /* 140 * This extent is currently being discarded. Give the thread 141 * performing the discard a chance to mark the extent unbusy 142 * and retry. 143 */ 144 if (busyp->flags & XFS_EXTENT_BUSY_DISCARDED) { 145 spin_unlock(&pag->pagb_lock); 146 delay(1); 147 spin_lock(&pag->pagb_lock); 148 return false; 149 } 150 151 /* 152 * If there is a busy extent overlapping a user allocation, we have 153 * no choice but to force the log and retry the search. 154 * 155 * Fortunately this does not happen during normal operation, but 156 * only if the filesystem is very low on space and has to dip into 157 * the AGFL for normal allocations. 158 */ 159 if (userdata) 160 goto out_force_log; 161 162 if (bbno < fbno && bend > fend) { 163 /* 164 * Case 1: 165 * bbno bend 166 * +BBBBBBBBBBBBBBBBB+ 167 * +---------+ 168 * fbno fend 169 */ 170 171 /* 172 * We would have to split the busy extent to be able to track 173 * it correct, which we cannot do because we would have to 174 * modify the list of busy extents attached to the transaction 175 * or CIL context, which is immutable. 176 * 177 * Force out the log to clear the busy extent and retry the 178 * search. 179 */ 180 goto out_force_log; 181 } else if (bbno >= fbno && bend <= fend) { 182 /* 183 * Case 2: 184 * bbno bend 185 * +BBBBBBBBBBBBBBBBB+ 186 * +-----------------+ 187 * fbno fend 188 * 189 * Case 3: 190 * bbno bend 191 * +BBBBBBBBBBBBBBBBB+ 192 * +--------------------------+ 193 * fbno fend 194 * 195 * Case 4: 196 * bbno bend 197 * +BBBBBBBBBBBBBBBBB+ 198 * +--------------------------+ 199 * fbno fend 200 * 201 * Case 5: 202 * bbno bend 203 * +BBBBBBBBBBBBBBBBB+ 204 * +-----------------------------------+ 205 * fbno fend 206 * 207 */ 208 209 /* 210 * The busy extent is fully covered by the extent we are 211 * allocating, and can simply be removed from the rbtree. 212 * However we cannot remove it from the immutable list 213 * tracking busy extents in the transaction or CIL context, 214 * so set the length to zero to mark it invalid. 215 * 216 * We also need to restart the busy extent search from the 217 * tree root, because erasing the node can rearrange the 218 * tree topology. 219 */ 220 rb_erase(&busyp->rb_node, &pag->pagb_tree); 221 busyp->length = 0; 222 return false; 223 } else if (fend < bend) { 224 /* 225 * Case 6: 226 * bbno bend 227 * +BBBBBBBBBBBBBBBBB+ 228 * +---------+ 229 * fbno fend 230 * 231 * Case 7: 232 * bbno bend 233 * +BBBBBBBBBBBBBBBBB+ 234 * +------------------+ 235 * fbno fend 236 * 237 */ 238 busyp->bno = fend; 239 busyp->length = bend - fend; 240 } else if (bbno < fbno) { 241 /* 242 * Case 8: 243 * bbno bend 244 * +BBBBBBBBBBBBBBBBB+ 245 * +-------------+ 246 * fbno fend 247 * 248 * Case 9: 249 * bbno bend 250 * +BBBBBBBBBBBBBBBBB+ 251 * +----------------------+ 252 * fbno fend 253 */ 254 busyp->length = fbno - busyp->bno; 255 } else { 256 ASSERT(0); 257 } 258 259 trace_xfs_extent_busy_reuse(mp, pag->pag_agno, fbno, flen); 260 return true; 261 262 out_force_log: 263 spin_unlock(&pag->pagb_lock); 264 xfs_log_force(mp, XFS_LOG_SYNC); 265 trace_xfs_extent_busy_force(mp, pag->pag_agno, fbno, flen); 266 spin_lock(&pag->pagb_lock); 267 return false; 268 } 269 270 271 /* 272 * For a given extent [fbno, flen], make sure we can reuse it safely. 273 */ 274 void 275 xfs_extent_busy_reuse( 276 struct xfs_mount *mp, 277 struct xfs_perag *pag, 278 xfs_agblock_t fbno, 279 xfs_extlen_t flen, 280 bool userdata) 281 { 282 struct rb_node *rbp; 283 284 ASSERT(flen > 0); 285 spin_lock(&pag->pagb_lock); 286 restart: 287 rbp = pag->pagb_tree.rb_node; 288 while (rbp) { 289 struct xfs_extent_busy *busyp = 290 rb_entry(rbp, struct xfs_extent_busy, rb_node); 291 xfs_agblock_t bbno = busyp->bno; 292 xfs_agblock_t bend = bbno + busyp->length; 293 294 if (fbno + flen <= bbno) { 295 rbp = rbp->rb_left; 296 continue; 297 } else if (fbno >= bend) { 298 rbp = rbp->rb_right; 299 continue; 300 } 301 302 if (!xfs_extent_busy_update_extent(mp, pag, busyp, fbno, flen, 303 userdata)) 304 goto restart; 305 } 306 spin_unlock(&pag->pagb_lock); 307 } 308 309 /* 310 * For a given extent [fbno, flen], search the busy extent list to find a 311 * subset of the extent that is not busy. If *rlen is smaller than 312 * args->minlen no suitable extent could be found, and the higher level 313 * code needs to force out the log and retry the allocation. 314 * 315 * Return the current busy generation for the AG if the extent is busy. This 316 * value can be used to wait for at least one of the currently busy extents 317 * to be cleared. Note that the busy list is not guaranteed to be empty after 318 * the gen is woken. The state of a specific extent must always be confirmed 319 * with another call to xfs_extent_busy_trim() before it can be used. 320 */ 321 bool 322 xfs_extent_busy_trim( 323 struct xfs_alloc_arg *args, 324 xfs_agblock_t *bno, 325 xfs_extlen_t *len, 326 unsigned *busy_gen) 327 { 328 xfs_agblock_t fbno; 329 xfs_extlen_t flen; 330 struct rb_node *rbp; 331 bool ret = false; 332 333 ASSERT(*len > 0); 334 335 spin_lock(&args->pag->pagb_lock); 336 fbno = *bno; 337 flen = *len; 338 rbp = args->pag->pagb_tree.rb_node; 339 while (rbp && flen >= args->minlen) { 340 struct xfs_extent_busy *busyp = 341 rb_entry(rbp, struct xfs_extent_busy, rb_node); 342 xfs_agblock_t fend = fbno + flen; 343 xfs_agblock_t bbno = busyp->bno; 344 xfs_agblock_t bend = bbno + busyp->length; 345 346 if (fend <= bbno) { 347 rbp = rbp->rb_left; 348 continue; 349 } else if (fbno >= bend) { 350 rbp = rbp->rb_right; 351 continue; 352 } 353 354 if (bbno <= fbno) { 355 /* start overlap */ 356 357 /* 358 * Case 1: 359 * bbno bend 360 * +BBBBBBBBBBBBBBBBB+ 361 * +---------+ 362 * fbno fend 363 * 364 * Case 2: 365 * bbno bend 366 * +BBBBBBBBBBBBBBBBB+ 367 * +-------------+ 368 * fbno fend 369 * 370 * Case 3: 371 * bbno bend 372 * +BBBBBBBBBBBBBBBBB+ 373 * +-------------+ 374 * fbno fend 375 * 376 * Case 4: 377 * bbno bend 378 * +BBBBBBBBBBBBBBBBB+ 379 * +-----------------+ 380 * fbno fend 381 * 382 * No unbusy region in extent, return failure. 383 */ 384 if (fend <= bend) 385 goto fail; 386 387 /* 388 * Case 5: 389 * bbno bend 390 * +BBBBBBBBBBBBBBBBB+ 391 * +----------------------+ 392 * fbno fend 393 * 394 * Case 6: 395 * bbno bend 396 * +BBBBBBBBBBBBBBBBB+ 397 * +--------------------------+ 398 * fbno fend 399 * 400 * Needs to be trimmed to: 401 * +-------+ 402 * fbno fend 403 */ 404 fbno = bend; 405 } else if (bend >= fend) { 406 /* end overlap */ 407 408 /* 409 * Case 7: 410 * bbno bend 411 * +BBBBBBBBBBBBBBBBB+ 412 * +------------------+ 413 * fbno fend 414 * 415 * Case 8: 416 * bbno bend 417 * +BBBBBBBBBBBBBBBBB+ 418 * +--------------------------+ 419 * fbno fend 420 * 421 * Needs to be trimmed to: 422 * +-------+ 423 * fbno fend 424 */ 425 fend = bbno; 426 } else { 427 /* middle overlap */ 428 429 /* 430 * Case 9: 431 * bbno bend 432 * +BBBBBBBBBBBBBBBBB+ 433 * +-----------------------------------+ 434 * fbno fend 435 * 436 * Can be trimmed to: 437 * +-------+ OR +-------+ 438 * fbno fend fbno fend 439 * 440 * Backward allocation leads to significant 441 * fragmentation of directories, which degrades 442 * directory performance, therefore we always want to 443 * choose the option that produces forward allocation 444 * patterns. 445 * Preferring the lower bno extent will make the next 446 * request use "fend" as the start of the next 447 * allocation; if the segment is no longer busy at 448 * that point, we'll get a contiguous allocation, but 449 * even if it is still busy, we will get a forward 450 * allocation. 451 * We try to avoid choosing the segment at "bend", 452 * because that can lead to the next allocation 453 * taking the segment at "fbno", which would be a 454 * backward allocation. We only use the segment at 455 * "fbno" if it is much larger than the current 456 * requested size, because in that case there's a 457 * good chance subsequent allocations will be 458 * contiguous. 459 */ 460 if (bbno - fbno >= args->maxlen) { 461 /* left candidate fits perfect */ 462 fend = bbno; 463 } else if (fend - bend >= args->maxlen * 4) { 464 /* right candidate has enough free space */ 465 fbno = bend; 466 } else if (bbno - fbno >= args->minlen) { 467 /* left candidate fits minimum requirement */ 468 fend = bbno; 469 } else { 470 goto fail; 471 } 472 } 473 474 flen = fend - fbno; 475 } 476 out: 477 478 if (fbno != *bno || flen != *len) { 479 trace_xfs_extent_busy_trim(args->mp, args->agno, *bno, *len, 480 fbno, flen); 481 *bno = fbno; 482 *len = flen; 483 *busy_gen = args->pag->pagb_gen; 484 ret = true; 485 } 486 spin_unlock(&args->pag->pagb_lock); 487 return ret; 488 fail: 489 /* 490 * Return a zero extent length as failure indications. All callers 491 * re-check if the trimmed extent satisfies the minlen requirement. 492 */ 493 flen = 0; 494 goto out; 495 } 496 497 STATIC void 498 xfs_extent_busy_clear_one( 499 struct xfs_mount *mp, 500 struct xfs_perag *pag, 501 struct xfs_extent_busy *busyp) 502 { 503 if (busyp->length) { 504 trace_xfs_extent_busy_clear(mp, busyp->agno, busyp->bno, 505 busyp->length); 506 rb_erase(&busyp->rb_node, &pag->pagb_tree); 507 } 508 509 list_del_init(&busyp->list); 510 kmem_free(busyp); 511 } 512 513 static void 514 xfs_extent_busy_put_pag( 515 struct xfs_perag *pag, 516 bool wakeup) 517 __releases(pag->pagb_lock) 518 { 519 if (wakeup) { 520 pag->pagb_gen++; 521 wake_up_all(&pag->pagb_wait); 522 } 523 524 spin_unlock(&pag->pagb_lock); 525 xfs_perag_put(pag); 526 } 527 528 /* 529 * Remove all extents on the passed in list from the busy extents tree. 530 * If do_discard is set skip extents that need to be discarded, and mark 531 * these as undergoing a discard operation instead. 532 */ 533 void 534 xfs_extent_busy_clear( 535 struct xfs_mount *mp, 536 struct list_head *list, 537 bool do_discard) 538 { 539 struct xfs_extent_busy *busyp, *n; 540 struct xfs_perag *pag = NULL; 541 xfs_agnumber_t agno = NULLAGNUMBER; 542 bool wakeup = false; 543 544 list_for_each_entry_safe(busyp, n, list, list) { 545 if (busyp->agno != agno) { 546 if (pag) 547 xfs_extent_busy_put_pag(pag, wakeup); 548 agno = busyp->agno; 549 pag = xfs_perag_get(mp, agno); 550 spin_lock(&pag->pagb_lock); 551 wakeup = false; 552 } 553 554 if (do_discard && busyp->length && 555 !(busyp->flags & XFS_EXTENT_BUSY_SKIP_DISCARD)) { 556 busyp->flags = XFS_EXTENT_BUSY_DISCARDED; 557 } else { 558 xfs_extent_busy_clear_one(mp, pag, busyp); 559 wakeup = true; 560 } 561 } 562 563 if (pag) 564 xfs_extent_busy_put_pag(pag, wakeup); 565 } 566 567 /* 568 * Flush out all busy extents for this AG. 569 * 570 * If the current transaction is holding busy extents, the caller may not want 571 * to wait for committed busy extents to resolve. If we are being told just to 572 * try a flush or progress has been made since we last skipped a busy extent, 573 * return immediately to allow the caller to try again. 574 * 575 * If we are freeing extents, we might actually be holding the only free extents 576 * in the transaction busy list and the log force won't resolve that situation. 577 * In this case, we must return -EAGAIN to avoid a deadlock by informing the 578 * caller it needs to commit the busy extents it holds before retrying the 579 * extent free operation. 580 */ 581 int 582 xfs_extent_busy_flush( 583 struct xfs_trans *tp, 584 struct xfs_perag *pag, 585 unsigned busy_gen, 586 uint32_t alloc_flags) 587 { 588 DEFINE_WAIT (wait); 589 int error; 590 591 error = xfs_log_force(tp->t_mountp, XFS_LOG_SYNC); 592 if (error) 593 return error; 594 595 /* Avoid deadlocks on uncommitted busy extents. */ 596 if (!list_empty(&tp->t_busy)) { 597 if (alloc_flags & XFS_ALLOC_FLAG_TRYFLUSH) 598 return 0; 599 600 if (busy_gen != READ_ONCE(pag->pagb_gen)) 601 return 0; 602 603 if (alloc_flags & XFS_ALLOC_FLAG_FREEING) 604 return -EAGAIN; 605 } 606 607 /* Wait for committed busy extents to resolve. */ 608 do { 609 prepare_to_wait(&pag->pagb_wait, &wait, TASK_KILLABLE); 610 if (busy_gen != READ_ONCE(pag->pagb_gen)) 611 break; 612 schedule(); 613 } while (1); 614 615 finish_wait(&pag->pagb_wait, &wait); 616 return 0; 617 } 618 619 void 620 xfs_extent_busy_wait_all( 621 struct xfs_mount *mp) 622 { 623 struct xfs_perag *pag; 624 DEFINE_WAIT (wait); 625 xfs_agnumber_t agno; 626 627 for_each_perag(mp, agno, pag) { 628 do { 629 prepare_to_wait(&pag->pagb_wait, &wait, TASK_KILLABLE); 630 if (RB_EMPTY_ROOT(&pag->pagb_tree)) 631 break; 632 schedule(); 633 } while (1); 634 finish_wait(&pag->pagb_wait, &wait); 635 } 636 } 637 638 /* 639 * Callback for list_sort to sort busy extents by the AG they reside in. 640 */ 641 int 642 xfs_extent_busy_ag_cmp( 643 void *priv, 644 const struct list_head *l1, 645 const struct list_head *l2) 646 { 647 struct xfs_extent_busy *b1 = 648 container_of(l1, struct xfs_extent_busy, list); 649 struct xfs_extent_busy *b2 = 650 container_of(l2, struct xfs_extent_busy, list); 651 s32 diff; 652 653 diff = b1->agno - b2->agno; 654 if (!diff) 655 diff = b1->bno - b2->bno; 656 return diff; 657 } 658