1/* 2 * Copyright (c) 1999-2012 Apple Inc. All rights reserved. 3 * 4 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@ 5 * 6 * This file contains Original Code and/or Modifications of Original Code 7 * as defined in and that are subject to the Apple Public Source License 8 * Version 2.0 (the 'License'). You may not use this file except in 9 * compliance with the License. The rights granted to you under the License 10 * may not be used to create, or enable the creation or redistribution of, 11 * unlawful or unlicensed copies of an Apple operating system, or to 12 * circumvent, violate, or enable the circumvention or violation of, any 13 * terms of an Apple operating system software license agreement. 14 * 15 * Please obtain a copy of the License at 16 * http://www.opensource.apple.com/apsl/ and read it before using this file. 17 * 18 * The Original Code and all software distributed under the License are 19 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER 20 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, 21 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, 22 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. 23 * Please see the License for the specific language governing rights and 24 * limitations under the License. 25 * 26 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@ 27 */ 28/* 29 * Copyright (c) 1989, 1993 30 * The Regents of the University of California. All rights reserved. 31 * (c) UNIX System Laboratories, Inc. 32 * All or some portions of this file are derived from material licensed 33 * to the University of California by American Telephone and Telegraph 34 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 35 * the permission of UNIX System Laboratories, Inc. 36 * 37 * Redistribution and use in source and binary forms, with or without 38 * modification, are permitted provided that the following conditions 39 * are met: 40 * 1. Redistributions of source code must retain the above copyright 41 * notice, this list of conditions and the following disclaimer. 42 * 2. Redistributions in binary form must reproduce the above copyright 43 * notice, this list of conditions and the following disclaimer in the 44 * documentation and/or other materials provided with the distribution. 45 * 3. All advertising materials mentioning features or use of this software 46 * must display the following acknowledgement: 47 * This product includes software developed by the University of 48 * California, Berkeley and its contributors. 49 * 4. Neither the name of the University nor the names of its contributors 50 * may be used to endorse or promote products derived from this software 51 * without specific prior written permission. 52 * 53 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 54 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 55 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 56 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 57 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 58 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 59 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 60 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 61 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 62 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 63 * SUCH DAMAGE. 64 * 65 * @(#)hfs_lookup.c 1.0 66 * derived from @(#)ufs_lookup.c 8.15 (Berkeley) 6/16/95 67 * 68 * (c) 1998-1999 Apple Computer, Inc. All Rights Reserved 69 * (c) 1990, 1992 NeXT Computer, Inc. All Rights Reserved 70 * 71 * 72 * hfs_lookup.c -- code to handle directory traversal on HFS/HFS+ volume 73 */ 74 75#include <sys/param.h> 76#include <sys/file.h> 77#include <sys/mount.h> 78#include <sys/vnode.h> 79#include <sys/malloc.h> 80#include <sys/kdebug.h> 81#include <sys/kauth.h> 82#include <sys/namei.h> 83#include <sys/user.h> 84 85#include "hfs.h" 86#include "hfs_catalog.h" 87#include "hfs_cnode.h" 88 89 90/* 91 * FROM FREEBSD 3.1 92 * Convert a component of a pathname into a pointer to a locked cnode. 93 * This is a very central and rather complicated routine. 94 * If the file system is not maintained in a strict tree hierarchy, 95 * this can result in a deadlock situation (see comments in code below). 96 * 97 * The cnp->cn_nameiop argument is LOOKUP, CREATE, RENAME, or DELETE depending 98 * on whether the name is to be looked up, created, renamed, or deleted. 99 * When CREATE, RENAME, or DELETE is specified, information usable in 100 * creating, renaming, or deleting a directory entry may be calculated. 101 * Notice that these are the only operations that can affect the directory of the target. 102 * 103 * LOCKPARENT and WANTPARENT actually refer to the parent of the last item, 104 * so if ISLASTCN is not set, they should be ignored. Also they are mutually exclusive, or 105 * WANTPARENT really implies DONTLOCKPARENT. Either of them set means that the calling 106 * routine wants to access the parent of the target, locked or unlocked. 107 * 108 * Keeping the parent locked as long as possible protects from other processes 109 * looking up the same item, so it has to be locked until the cnode is totally finished 110 * 111 * hfs_cache_lookup() performs the following for us: 112 * check that it is a directory 113 * check accessibility of directory 114 * check for modification attempts on read-only mounts 115 * if name found in cache 116 * if at end of path and deleting or creating 117 * drop it 118 * else 119 * return name. 120 * return hfs_lookup() 121 * 122 * Overall outline of hfs_lookup: 123 * 124 * handle simple cases of . and .. 125 * search for name in directory, to found or notfound 126 * notfound: 127 * if creating, return locked directory, leaving info on available slots 128 * else return error 129 * found: 130 * if at end of path and deleting, return information to allow delete 131 * if at end of path and rewriting (RENAME and LOCKPARENT), lock target 132 * cnode and return info to allow rewrite 133 * if not at end, add name to cache; if at end and neither creating 134 * nor deleting, add name to cache 135 */ 136 137 138/* 139 * Lookup *cnp in directory *dvp, return it in *vpp. 140 * **vpp is held on exit. 141 * We create a cnode for the file, but we do NOT open the file here. 142 143#% lookup dvp L ? ? 144#% lookup vpp - L - 145 146 IN struct vnode *dvp - Parent node of file; 147 INOUT struct vnode **vpp - node of target file, its a new node if 148 the target vnode did not exist; 149 IN struct componentname *cnp - Name of file; 150 151 * When should we lock parent_hp in here ?? 152 */ 153static int 154hfs_lookup(struct vnode *dvp, struct vnode **vpp, struct componentname *cnp, int *cnode_locked) 155{ 156 struct cnode *dcp; /* cnode for directory being searched */ 157 struct vnode *tvp; /* target vnode */ 158 struct hfsmount *hfsmp; 159 int flags; 160 int nameiop; 161 int retval = 0; 162 int isDot; 163 struct cat_desc desc; 164 struct cat_desc cndesc; 165 struct cat_attr attr; 166 struct cat_fork fork; 167 int lockflags; 168 int newvnode_flags; 169 170 retry: 171 newvnode_flags = 0; 172 dcp = NULL; 173 hfsmp = VTOHFS(dvp); 174 *vpp = NULL; 175 *cnode_locked = 0; 176 isDot = FALSE; 177 tvp = NULL; 178 nameiop = cnp->cn_nameiop; 179 flags = cnp->cn_flags; 180 bzero(&desc, sizeof(desc)); 181 182 /* 183 * First check to see if it is a . or .., else look it up. 184 */ 185 if (flags & ISDOTDOT) { /* Wanting the parent */ 186 cnp->cn_flags &= ~MAKEENTRY; 187 goto found; /* .. is always defined */ 188 } else if ((cnp->cn_nameptr[0] == '.') && (cnp->cn_namelen == 1)) { 189 isDot = TRUE; 190 cnp->cn_flags &= ~MAKEENTRY; 191 goto found; /* We always know who we are */ 192 } else { 193 if (hfs_lock(VTOC(dvp), HFS_EXCLUSIVE_LOCK) != 0) { 194 retval = ENOENT; /* The parent no longer exists ? */ 195 goto exit; 196 } 197 dcp = VTOC(dvp); 198 199 if (dcp->c_flag & C_DIR_MODIFICATION) { 200 // XXXdbg - if we could msleep on a lck_rw_t then we would do that 201 // but since we can't we have to unlock, delay for a bit 202 // and then retry... 203 // msleep((caddr_t)&dcp->c_flag, &dcp->c_rwlock, PINOD, "hfs_vnop_lookup", 0); 204 hfs_unlock(dcp); 205 tsleep((caddr_t)dvp, PRIBIO, "hfs_lookup", 1); 206 207 goto retry; 208 } 209 210 /* No need to go to catalog if there are no children */ 211 if (dcp->c_entries == 0) { 212 goto notfound; 213 } 214 215 bzero(&cndesc, sizeof(cndesc)); 216 cndesc.cd_nameptr = (const u_int8_t *)cnp->cn_nameptr; 217 cndesc.cd_namelen = cnp->cn_namelen; 218 cndesc.cd_parentcnid = dcp->c_fileid; 219 cndesc.cd_hint = dcp->c_childhint; 220 221 lockflags = hfs_systemfile_lock(hfsmp, SFL_CATALOG, HFS_SHARED_LOCK); 222 223 retval = cat_lookup(hfsmp, &cndesc, 0, &desc, &attr, &fork, NULL); 224 225 hfs_systemfile_unlock(hfsmp, lockflags); 226 227 if (retval == 0) { 228 dcp->c_childhint = desc.cd_hint; 229 /* 230 * Note: We must drop the parent lock here before calling 231 * hfs_getnewvnode (which takes the child lock). 232 */ 233 hfs_unlock(dcp); 234 dcp = NULL; 235 236 /* Verify that the item just looked up isn't one of the hidden directories. */ 237 if (desc.cd_cnid == hfsmp->hfs_private_desc[FILE_HARDLINKS].cd_cnid || 238 desc.cd_cnid == hfsmp->hfs_private_desc[DIR_HARDLINKS].cd_cnid) { 239 retval = ENOENT; 240 goto exit; 241 } 242 243 goto found; 244 } 245notfound: 246 /* 247 * ENAMETOOLONG supersedes other errors 248 * 249 * For a CREATE or RENAME operation on the last component 250 * the ENAMETOOLONG will be handled in the next VNOP. 251 */ 252 if ((retval != ENAMETOOLONG) && 253 (cnp->cn_namelen > kHFSPlusMaxFileNameChars) && 254 (((flags & ISLASTCN) == 0) || ((nameiop != CREATE) && (nameiop != RENAME)))) { 255 retval = ENAMETOOLONG; 256 } else if (retval == 0) { 257 retval = ENOENT; 258 } 259 if (retval != ENOENT) 260 goto exit; 261 /* 262 * This is a non-existing entry 263 * 264 * If creating, and at end of pathname and current 265 * directory has not been removed, then can consider 266 * allowing file to be created. 267 */ 268 if ((nameiop == CREATE || nameiop == RENAME || 269 (nameiop == DELETE && 270 (cnp->cn_flags & DOWHITEOUT) && 271 (cnp->cn_flags & ISWHITEOUT))) && 272 (flags & ISLASTCN) && 273 !(ISSET(dcp->c_flag, C_DELETED | C_NOEXISTS))) { 274 retval = EJUSTRETURN; 275 goto exit; 276 } 277 /* 278 * Insert name into the name cache (as non-existent). 279 */ 280 if ((hfsmp->hfs_flags & HFS_STANDARD) == 0 && 281 (cnp->cn_flags & MAKEENTRY) && 282 (nameiop != CREATE)) { 283 cache_enter(dvp, NULL, cnp); 284 dcp->c_flag |= C_NEG_ENTRIES; 285 } 286 goto exit; 287 } 288 289found: 290 if (flags & ISLASTCN) { 291 switch(nameiop) { 292 case DELETE: 293 cnp->cn_flags &= ~MAKEENTRY; 294 break; 295 296 case RENAME: 297 cnp->cn_flags &= ~MAKEENTRY; 298 if (isDot) { 299 retval = EISDIR; 300 goto exit; 301 } 302 break; 303 } 304 } 305 306 if (isDot) { 307 if ((retval = vnode_get(dvp))) 308 goto exit; 309 *vpp = dvp; 310 } else if (flags & ISDOTDOT) { 311 /* 312 * Directory hard links can have multiple parents so 313 * find the appropriate parent for the current thread. 314 */ 315 if ((retval = hfs_vget(hfsmp, hfs_currentparent(VTOC(dvp)), &tvp, 0, 0))) { 316 goto exit; 317 } 318 *cnode_locked = 1; 319 *vpp = tvp; 320 } else { 321 int type = (attr.ca_mode & S_IFMT); 322 323 if (!(flags & ISLASTCN) && (type != S_IFDIR) && (type != S_IFLNK)) { 324 retval = ENOTDIR; 325 goto exit; 326 } 327 /* Don't cache directory hardlink names. */ 328 if (attr.ca_recflags & kHFSHasLinkChainMask) { 329 cnp->cn_flags &= ~MAKEENTRY; 330 } 331 /* Names with composed chars are not cached. */ 332 if (cnp->cn_namelen != desc.cd_namelen) 333 cnp->cn_flags &= ~MAKEENTRY; 334 335 retval = hfs_getnewvnode(hfsmp, dvp, cnp, &desc, 0, &attr, &fork, &tvp, &newvnode_flags); 336 337 if (retval) { 338 /* 339 * If this was a create/rename operation lookup, then by this point 340 * we expected to see the item returned from hfs_getnewvnode above. 341 * In the create case, it would probably eventually bubble out an EEXIST 342 * because the item existed when we were trying to create it. In the 343 * rename case, it would let us know that we need to go ahead and 344 * delete it as part of the rename. However, if we hit the condition below 345 * then it means that we found the element during cat_lookup above, but 346 * it is now no longer there. We simply behave as though we never found 347 * the element at all and return EJUSTRETURN. 348 */ 349 if ((retval == ENOENT) && 350 ((cnp->cn_nameiop == CREATE) || (cnp->cn_nameiop == RENAME)) && 351 (flags & ISLASTCN)) { 352 retval = EJUSTRETURN; 353 } 354 355 /* 356 * If this was a straight lookup operation, we may need to redrive the entire 357 * lookup starting from cat_lookup if the element was deleted as the result of 358 * a rename operation. Since rename is supposed to guarantee atomicity, then 359 * lookups cannot fail because the underlying element is deleted as a result of 360 * the rename call -- either they returned the looked up element prior to rename 361 * or return the newer element. If we are in this region, then all we can do is add 362 * workarounds to guarantee the latter case. The element has already been deleted, so 363 * we just re-try the lookup to ensure the caller gets the most recent element. 364 */ 365 if ((retval == ENOENT) && (cnp->cn_nameiop == LOOKUP) && 366 (newvnode_flags & (GNV_CHASH_RENAMED | GNV_CAT_DELETED))) { 367 if (dcp) { 368 hfs_unlock (dcp); 369 } 370 /* get rid of any name buffers that may have lingered from the cat_lookup call */ 371 cat_releasedesc (&desc); 372 goto retry; 373 } 374 375 /* Also, re-drive the lookup if the item we looked up was a hardlink, and the number 376 * or name of hardlinks has changed in the interim between the cat_lookup above, and 377 * our call to hfs_getnewvnode. hfs_getnewvnode will validate the cattr we passed it 378 * against what is actually in the catalog after the cnode is created. If there were 379 * any issues, it will bubble out ERECYCLE, which we need to swallow and use as the 380 * key to redrive as well. We need to special case this below because in this case, 381 * it needs to occur regardless of the type of lookup we're doing here. 382 */ 383 if ((retval == ERECYCLE) && (newvnode_flags & GNV_CAT_ATTRCHANGED)) { 384 if (dcp) { 385 hfs_unlock (dcp); 386 } 387 /* get rid of any name buffers that may have lingered from the cat_lookup call */ 388 cat_releasedesc (&desc); 389 retval = 0; 390 goto retry; 391 } 392 393 /* skip to the error-handling code if we can't retry */ 394 goto exit; 395 } 396 397 /* 398 * Save the origin info for file and directory hardlinks. Directory hardlinks 399 * need the origin for '..' lookups, and file hardlinks need it to ensure that 400 * competing lookups do not cause us to vend different hardlinks than the ones requested. 401 * We want to restrict saving the cache entries to LOOKUP namei operations, since 402 * we're really doing this to protect getattr. 403 */ 404 if ((nameiop == LOOKUP) && (VTOC(tvp)->c_flag & C_HARDLINK)) { 405 hfs_savelinkorigin(VTOC(tvp), VTOC(dvp)->c_fileid); 406 } 407 *cnode_locked = 1; 408 *vpp = tvp; 409 } 410exit: 411 if (dcp) { 412 hfs_unlock(dcp); 413 } 414 cat_releasedesc(&desc); 415 return (retval); 416} 417 418 419 420/* 421 * Name caching works as follows: 422 * 423 * Names found by directory scans are retained in a cache 424 * for future reference. It is managed LRU, so frequently 425 * used names will hang around. Cache is indexed by hash value 426 * obtained from (vp, name) where vp refers to the directory 427 * containing name. 428 * 429 * If it is a "negative" entry, (i.e. for a name that is known NOT to 430 * exist) the vnode pointer will be NULL. 431 * 432 * Upon reaching the last segment of a path, if the reference 433 * is for DELETE, or NOCACHE is set (rewrite), and the 434 * name is located in the cache, it will be dropped. 435 * 436 */ 437 438#define S_IXALL 0000111 439 440int 441hfs_vnop_lookup(struct vnop_lookup_args *ap) 442{ 443 struct vnode *dvp = ap->a_dvp; 444 struct vnode *vp; 445 struct cnode *cp; 446 struct cnode *dcp; 447 struct hfsmount *hfsmp; 448 int error; 449 struct vnode **vpp = ap->a_vpp; 450 struct componentname *cnp = ap->a_cnp; 451 int flags = cnp->cn_flags; 452 int cnode_locked; 453 454 *vpp = NULL; 455 dcp = VTOC(dvp); 456 457 hfsmp = VTOHFS(dvp); 458 459 /* 460 * Lookup an entry in the cache 461 * 462 * If the lookup succeeds, the vnode is returned in *vpp, 463 * and a status of -1 is returned. 464 * 465 * If the lookup determines that the name does not exist 466 * (negative cacheing), a status of ENOENT is returned. 467 * 468 * If the lookup fails, a status of zero is returned. 469 */ 470 error = cache_lookup(dvp, vpp, cnp); 471 if (error != -1) { 472 if ((error == ENOENT) && (cnp->cn_nameiop != CREATE)) 473 goto exit; /* found a negative cache entry */ 474 goto lookup; /* did not find it in the cache */ 475 } 476 /* 477 * We have a name that matched 478 * cache_lookup returns the vp with an iocount reference already taken 479 */ 480 error = 0; 481 vp = *vpp; 482 cp = VTOC(vp); 483 484 /* We aren't allowed to vend out vp's via lookup to the hidden directory */ 485 if (cp->c_cnid == hfsmp->hfs_private_desc[FILE_HARDLINKS].cd_cnid || 486 cp->c_cnid == hfsmp->hfs_private_desc[DIR_HARDLINKS].cd_cnid) { 487 /* Drop the iocount from cache_lookup */ 488 vnode_put (vp); 489 error = ENOENT; 490 goto exit; 491 } 492 493 494 /* 495 * If this is a hard-link vnode then we need to update 496 * the name (of the link), the parent ID, the cnid, the 497 * text encoding and the catalog hint. This enables 498 * getattrlist calls to return the correct link info. 499 */ 500 501 if ((flags & ISLASTCN) && (cp->c_flag & C_HARDLINK)) { 502 int stale_link = 0; 503 504 hfs_lock(cp, HFS_FORCE_LOCK); 505 if ((cp->c_parentcnid != dcp->c_cnid) || 506 (bcmp(cnp->cn_nameptr, cp->c_desc.cd_nameptr, cp->c_desc.cd_namelen) != 0)) { 507 struct cat_desc desc; 508 struct cat_attr lookup_attr; 509 int lockflags; 510 /* 511 * Get an updated descriptor 512 */ 513 desc.cd_nameptr = (const u_int8_t *)cnp->cn_nameptr; 514 desc.cd_namelen = cnp->cn_namelen; 515 desc.cd_parentcnid = dcp->c_fileid; 516 desc.cd_hint = dcp->c_childhint; 517 desc.cd_encoding = 0; 518 desc.cd_cnid = 0; 519 desc.cd_flags = S_ISDIR(cp->c_mode) ? CD_ISDIR : 0; 520 521 /* 522 * Because lookups call replace_desc to put a new descriptor in 523 * the cnode we are modifying it is possible that this cnode's 524 * descriptor is out of date for the parent ID / name that 525 * we are trying to look up. (It may point to a different hardlink). 526 * 527 * We need to be cautious that when re-supplying the 528 * descriptor below that the results of the catalog lookup 529 * still point to the same raw inode for the hardlink. This would 530 * not be the case if we found something in the cache above but 531 * the vnode it returned no longer has a valid hardlink for the 532 * parent ID/filename combo we are requesting. (This is because 533 * hfs_unlink does not directly trigger namecache removal). 534 * 535 * As a result, before vending out the vnode (and replacing 536 * its descriptor) verify that the fileID is the same by comparing 537 * the in-cnode attributes vs. the one returned from the lookup call 538 * below. If they do not match, treat this lookup as if we never hit 539 * in the cache at all. 540 */ 541 542 lockflags = hfs_systemfile_lock(VTOHFS(dvp), SFL_CATALOG, HFS_SHARED_LOCK); 543 544 error = cat_lookup(VTOHFS(vp), &desc, 0, &desc, &lookup_attr, NULL, NULL); 545 546 hfs_systemfile_unlock(VTOHFS(dvp), lockflags); 547 548 /* 549 * Note that cat_lookup may fail to find something with the name provided in the 550 * stack-based descriptor above. In that case, an ENOENT is a legitimate errno 551 * to be placed in error, which will get returned in the fastpath below. 552 */ 553 if (error == 0) { 554 if (lookup_attr.ca_fileid == cp->c_attr.ca_fileid) { 555 /* It still points to the right raw inode. Replacing the descriptor is fine */ 556 replace_desc (cp, &desc); 557 558 /* 559 * Save the origin info for file and directory hardlinks. Directory hardlinks 560 * need the origin for '..' lookups, and file hardlinks need it to ensure that 561 * competing lookups do not cause us to vend different hardlinks than the ones requested. 562 * We want to restrict saving the cache entries to LOOKUP namei operations, since 563 * we're really doing this to protect getattr. 564 */ 565 if (cnp->cn_nameiop == LOOKUP) { 566 hfs_savelinkorigin(cp, dcp->c_fileid); 567 } 568 } 569 else { 570 /* If the fileID does not match then do NOT replace the descriptor! */ 571 stale_link = 1; 572 } 573 } 574 } 575 hfs_unlock (cp); 576 577 if (stale_link) { 578 /* 579 * If we had a stale_link, then we need to pretend as though 580 * we never found this vnode and force a lookup through the 581 * traditional path. Drop the iocount acquired through 582 * cache_lookup above and force a cat lookup / getnewvnode 583 */ 584 vnode_put(vp); 585 goto lookup; 586 } 587 588 if (error) { 589 /* 590 * If the cat_lookup failed then the caller will not expect 591 * a vnode with an iocount on it. 592 */ 593 vnode_put(vp); 594 } 595 596 } 597 goto exit; 598 599lookup: 600 /* 601 * The vnode was not in the name cache or it was stale. 602 * 603 * So we need to do a real lookup. 604 */ 605 cnode_locked = 0; 606 607 error = hfs_lookup(dvp, vpp, cnp, &cnode_locked); 608 609 if (cnode_locked) 610 hfs_unlock(VTOC(*vpp)); 611exit: 612 { 613 uthread_t ut = (struct uthread *)get_bsdthread_info(current_thread()); 614 615 /* 616 * check to see if we issued any I/O while completing this lookup and 617 * this thread/task is throttleable... if so, throttle now 618 * 619 * this allows us to throttle in between multiple meta data reads that 620 * might result due to looking up a long pathname (since we'll have to 621 * re-enter hfs_vnop_lookup for each component of the pathnam not in 622 * the VFS cache), instead of waiting until the entire path lookup has 623 * completed and throttling at the systemcall return 624 */ 625 if (__improbable(ut->uu_lowpri_window)) { 626 throttle_lowpri_io(TRUE); 627 } 628 } 629 630 return (error); 631} 632 633 634