1 /* 2 * Copyright (c) 1982, 1986 Regents of the University of California. 3 * All rights reserved. The Berkeley software License Agreement 4 * specifies the terms and conditions for redistribution. 5 * 6 * @(#)ufs_lookup.c 7.1 (Berkeley) 06/05/86 7 */ 8 9 #include "param.h" 10 #include "systm.h" 11 #include "inode.h" 12 #include "fs.h" 13 #include "mount.h" 14 #include "dir.h" 15 #include "user.h" 16 #include "buf.h" 17 #include "conf.h" 18 #include "uio.h" 19 #include "kernel.h" 20 21 struct buf *blkatoff(); 22 struct buf *freenamebuf; 23 int dirchk = 0; 24 25 /* 26 * Structures associated with name cacheing. 27 */ 28 #define NCHHASH 32 /* size of hash table */ 29 30 #if ((NCHHASH)&((NCHHASH)-1)) != 0 31 #define NHASH(h, i, d) ((unsigned)((h) + (i) + 13 * (int)(d)) % (NCHHASH)) 32 #else 33 #define NHASH(h, i, d) ((unsigned)((h) + (i) + 13 * (int)(d)) & ((NCHHASH)-1)) 34 #endif 35 36 union nchash { 37 union nchash *nch_head[2]; 38 struct namecache *nch_chain[2]; 39 } nchash[NCHHASH]; 40 #define nch_forw nch_chain[0] 41 #define nch_back nch_chain[1] 42 43 struct namecache *nchhead, **nchtail; /* LRU chain pointers */ 44 struct nchstats nchstats; /* cache effectiveness statistics */ 45 46 /* 47 * Convert a pathname into a pointer to a locked inode. 48 * This is a very central and rather complicated routine. 49 * If the file system is not maintained in a strict tree hierarchy, 50 * this can result in a deadlock situation (see comments in code below). 51 * 52 * The flag argument is LOOKUP, CREATE, or DELETE depending on whether 53 * the name is to be looked up, created, or deleted. When CREATE or 54 * DELETE is specified, information usable in creating or deleteing a 55 * directory entry is also calculated. If flag has LOCKPARENT or'ed 56 * into it and the target of the pathname exists, namei returns both 57 * the target and its parent directory locked. When creating and 58 * LOCKPARENT is specified, the target may not be ".". When deleting 59 * and LOCKPARENT is specified, the target may be ".", but the caller 60 * must check to insure it does an irele and iput instead of two iputs. 61 * 62 * The FOLLOW flag is set when symbolic links are to be followed 63 * when they occur at the end of the name translation process. 64 * Symbolic links are always followed for all other pathname 65 * components other than the last. 66 * 67 * The segflg defines whether the name is to be copied from user 68 * space or kernel space. 69 * 70 * Name caching works as follows: 71 * 72 * Names found by directory scans are retained in a cache 73 * for future reference. It is managed LRU, so frequently 74 * used names will hang around. Cache is indexed by hash value 75 * obtained from (ino,dev,name) where ino & dev refer to the 76 * directory containing name. 77 * 78 * For simplicity (and economy of storage), names longer than 79 * a maximum length of NCHNAMLEN are not cached; they occur 80 * infrequently in any case, and are almost never of interest. 81 * 82 * Upon reaching the last segment of a path, if the reference 83 * is for DELETE, or NOCACHE is set (rewrite), and the 84 * name is located in the cache, it will be dropped. 85 * 86 * Overall outline of namei: 87 * 88 * copy in name 89 * get starting directory 90 * dirloop: 91 * check accessibility of directory 92 * dirloop2: 93 * copy next component of name to ndp->ni_dent 94 * handle degenerate case where name is null string 95 * look for name in cache, if found, then if at end of path 96 * and deleting or creating, drop it, else to haveino 97 * search for name in directory, to found or notfound 98 * notfound: 99 * if creating, return locked directory, leaving info on avail. slots 100 * else return error 101 * found: 102 * if at end of path and deleting, return information to allow delete 103 * if at end of path and rewriting (CREATE and LOCKPARENT), lock target 104 * inode and return info to allow rewrite 105 * if .. and on mounted filesys, look in mount table for parent 106 * if not at end, add name to cache; if at end and neither creating 107 * nor deleting, add name to cache 108 * haveino: 109 * if symbolic link, massage name in buffer and continue at dirloop 110 * if more components of name, do next level at dirloop 111 * return the answer as locked inode 112 * 113 * NOTE: (LOOKUP | LOCKPARENT) currently returns the parent inode, 114 * but unlocked. 115 */ 116 struct inode * 117 namei(ndp) 118 register struct nameidata *ndp; 119 { 120 register char *cp; /* pointer into pathname argument */ 121 /* these variables refer to things which must be freed or unlocked */ 122 register struct inode *dp = 0; /* the directory we are searching */ 123 register struct namecache *ncp; /* cache slot for entry */ 124 register struct fs *fs; /* file system that directory is in */ 125 register struct buf *bp = 0; /* a buffer of directory entries */ 126 register struct direct *ep; /* the current directory entry */ 127 int entryoffsetinblock; /* offset of ep in bp's buffer */ 128 register struct buf *nbp; /* buffer storing path name argument */ 129 /* these variables hold information about the search for a slot */ 130 enum {NONE, COMPACT, FOUND} slotstatus; 131 int slotoffset = -1; /* offset of area with free space */ 132 int slotsize; /* size of area at slotoffset */ 133 int slotfreespace; /* amount of space free in slot */ 134 int slotneeded; /* size of the entry we're seeking */ 135 /* */ 136 int numdirpasses; /* strategy for directory search */ 137 int endsearch; /* offset to end directory search */ 138 int prevoff; /* ndp->ni_offset of previous entry */ 139 int nlink = 0; /* number of symbolic links taken */ 140 struct inode *pdp; /* saved dp during symlink work */ 141 int error, i; 142 int lockparent; 143 int docache; /* == 0 do not cache last component */ 144 int makeentry; /* != 0 if name to be added to cache */ 145 unsigned hash; /* value of name hash for entry */ 146 union nchash *nhp; /* cache chain head for entry */ 147 int isdotdot; /* != 0 if current name is ".." */ 148 int flag; /* op ie, LOOKUP, CREATE, or DELETE */ 149 off_t enduseful; /* pointer past last used dir slot */ 150 151 lockparent = ndp->ni_nameiop & LOCKPARENT; 152 docache = (ndp->ni_nameiop & NOCACHE) ^ NOCACHE; 153 flag = ndp->ni_nameiop &~ (LOCKPARENT|NOCACHE|FOLLOW); 154 if (flag == DELETE || lockparent) 155 docache = 0; 156 /* 157 * Get a buffer for the name to be translated, and copy the 158 * name into the buffer. 159 */ 160 nbp = freenamebuf; 161 if (nbp == NULL) 162 nbp = geteblk(MAXPATHLEN); 163 else 164 freenamebuf = nbp->av_forw; 165 if (ndp->ni_segflg == UIO_SYSSPACE) 166 error = copystr(ndp->ni_dirp, nbp->b_un.b_addr, MAXPATHLEN, 167 (u_int *)0); 168 else 169 error = copyinstr(ndp->ni_dirp, nbp->b_un.b_addr, MAXPATHLEN, 170 (u_int *)0); 171 if (error) { 172 u.u_error = error; 173 goto bad; 174 } 175 176 /* 177 * Get starting directory. 178 */ 179 cp = nbp->b_un.b_addr; 180 if (*cp == '/') { 181 while (*cp == '/') 182 cp++; 183 if ((dp = u.u_rdir) == NULL) 184 dp = rootdir; 185 } else 186 dp = u.u_cdir; 187 fs = dp->i_fs; 188 ILOCK(dp); 189 dp->i_count++; 190 ndp->ni_pdir = (struct inode *)0xc0000000; /* illegal */ 191 ndp->ni_endoff = 0; 192 193 /* 194 * We come to dirloop to search a new directory. 195 * The directory must be locked so that it can be 196 * iput, and fs must be already set to dp->i_fs. 197 */ 198 dirloop: 199 /* 200 * Check accessiblity of directory. 201 */ 202 if ((dp->i_mode&IFMT) != IFDIR) { 203 u.u_error = ENOTDIR; 204 goto bad; 205 } 206 if (access(dp, IEXEC)) 207 goto bad; 208 209 dirloop2: 210 /* 211 * Copy next component of name to ndp->ni_dent. 212 */ 213 hash = 0; 214 for (i = 0; *cp != 0 && *cp != '/'; cp++) { 215 if (i >= MAXNAMLEN) { 216 u.u_error = ENAMETOOLONG; 217 goto bad; 218 } 219 if (*cp & 0200) 220 if ((*cp&0377) == ('/'|0200) || flag != DELETE) { 221 u.u_error = EINVAL; 222 goto bad; 223 } 224 ndp->ni_dent.d_name[i++] = *cp; 225 hash += (unsigned char)*cp * i; 226 } 227 ndp->ni_dent.d_namlen = i; 228 ndp->ni_dent.d_name[i] = '\0'; 229 isdotdot = (i == 2 && 230 ndp->ni_dent.d_name[0] == '.' && ndp->ni_dent.d_name[1] == '.'); 231 makeentry = 1; 232 if (*cp == '\0' && docache == 0) 233 makeentry = 0; 234 235 /* 236 * Check for degenerate name (e.g. / or "") 237 * which is a way of talking about a directory, 238 * e.g. like "/." or ".". 239 */ 240 if (ndp->ni_dent.d_name[0] == '\0') { 241 if (flag != LOOKUP || lockparent) { 242 u.u_error = EISDIR; 243 goto bad; 244 } 245 nbp->av_forw = freenamebuf; 246 freenamebuf = nbp; 247 return (dp); 248 } 249 250 /* 251 * We now have a segment name to search for, and a directory to search. 252 * 253 * Before tediously performing a linear scan of the directory, 254 * check the name cache to see if the directory/name pair 255 * we are looking for is known already. We don't do this 256 * if the segment name is long, simply so the cache can avoid 257 * holding long names (which would either waste space, or 258 * add greatly to the complexity). 259 */ 260 if (ndp->ni_dent.d_namlen > NCHNAMLEN) { 261 nchstats.ncs_long++; 262 makeentry = 0; 263 } else { 264 nhp = &nchash[NHASH(hash, dp->i_number, dp->i_dev)]; 265 for (ncp = nhp->nch_forw; ncp != (struct namecache *)nhp; 266 ncp = ncp->nc_forw) { 267 if (ncp->nc_ino == dp->i_number && 268 ncp->nc_dev == dp->i_dev && 269 ncp->nc_nlen == ndp->ni_dent.d_namlen && 270 !bcmp(ncp->nc_name, ndp->ni_dent.d_name, 271 (unsigned)ncp->nc_nlen)) 272 break; 273 } 274 if (ncp == (struct namecache *)nhp) { 275 nchstats.ncs_miss++; 276 ncp = NULL; 277 } else { 278 if (ncp->nc_id != ncp->nc_ip->i_id) 279 nchstats.ncs_falsehits++; 280 else if (!makeentry) 281 nchstats.ncs_badhits++; 282 else { 283 /* 284 * move this slot to end of LRU 285 * chain, if not already there 286 */ 287 if (ncp->nc_nxt) { 288 /* remove from LRU chain */ 289 *ncp->nc_prev = ncp->nc_nxt; 290 ncp->nc_nxt->nc_prev = ncp->nc_prev; 291 292 /* and replace at end of it */ 293 ncp->nc_nxt = NULL; 294 ncp->nc_prev = nchtail; 295 *nchtail = ncp; 296 nchtail = &ncp->nc_nxt; 297 } 298 299 /* 300 * Get the next inode in the path. 301 * See comment above other `IUNLOCK' code for 302 * an explaination of the locking protocol. 303 */ 304 pdp = dp; 305 if (!isdotdot || dp != u.u_rdir) 306 dp = ncp->nc_ip; 307 if (dp == NULL) 308 panic("namei: null cache ino"); 309 if (pdp == dp) 310 dp->i_count++; 311 else if (isdotdot) { 312 IUNLOCK(pdp); 313 igrab(dp); 314 } else { 315 igrab(dp); 316 IUNLOCK(pdp); 317 } 318 319 /* 320 * Verify that the inode that we got 321 * did not change while we were waiting 322 * for it to be locked. 323 */ 324 if (ncp->nc_id != ncp->nc_ip->i_id) { 325 iput(dp); 326 ILOCK(pdp); 327 dp = pdp; 328 nchstats.ncs_falsehits++; 329 } else { 330 ndp->ni_dent.d_ino = dp->i_number; 331 /* ni_dent.d_reclen is garbage ... */ 332 nchstats.ncs_goodhits++; 333 goto haveino; 334 } 335 } 336 337 /* 338 * Last component and we are renaming or deleting, 339 * the cache entry is invalid, or otherwise don't 340 * want cache entry to exist. 341 */ 342 /* remove from LRU chain */ 343 *ncp->nc_prev = ncp->nc_nxt; 344 if (ncp->nc_nxt) 345 ncp->nc_nxt->nc_prev = ncp->nc_prev; 346 else 347 nchtail = ncp->nc_prev; 348 remque(ncp); /* remove from hash chain */ 349 /* insert at head of LRU list (first to grab) */ 350 ncp->nc_nxt = nchhead; 351 ncp->nc_prev = &nchhead; 352 nchhead->nc_prev = &ncp->nc_nxt; 353 nchhead = ncp; 354 /* and make a dummy hash chain */ 355 ncp->nc_forw = ncp; 356 ncp->nc_back = ncp; 357 ncp = NULL; 358 } 359 } 360 361 /* 362 * Suppress search for slots unless creating 363 * file and at end of pathname, in which case 364 * we watch for a place to put the new file in 365 * case it doesn't already exist. 366 */ 367 slotstatus = FOUND; 368 if (flag == CREATE && *cp == 0) { 369 slotstatus = NONE; 370 slotfreespace = 0; 371 slotneeded = DIRSIZ(&ndp->ni_dent); 372 } 373 /* 374 * If this is the same directory that this process 375 * previously searched, pick up where we last left off. 376 * We cache only lookups as these are the most common 377 * and have the greatest payoff. Caching CREATE has little 378 * benefit as it usually must search the entire directory 379 * to determine that the entry does not exist. Caching the 380 * location of the last DELETE has not reduced profiling time 381 * and hence has been removed in the interest of simplicity. 382 */ 383 if (flag != LOOKUP || dp->i_number != u.u_ncache.nc_inumber || 384 dp->i_dev != u.u_ncache.nc_dev) { 385 ndp->ni_offset = 0; 386 numdirpasses = 1; 387 } else { 388 if (u.u_ncache.nc_prevoffset > dp->i_size) 389 u.u_ncache.nc_prevoffset = 0; 390 ndp->ni_offset = u.u_ncache.nc_prevoffset; 391 entryoffsetinblock = blkoff(fs, ndp->ni_offset); 392 if (entryoffsetinblock != 0) { 393 bp = blkatoff(dp, ndp->ni_offset, (char **)0); 394 if (bp == 0) 395 goto bad; 396 } 397 numdirpasses = 2; 398 nchstats.ncs_2passes++; 399 } 400 endsearch = roundup(dp->i_size, DIRBLKSIZ); 401 enduseful = 0; 402 403 searchloop: 404 while (ndp->ni_offset < endsearch) { 405 /* 406 * If offset is on a block boundary, 407 * read the next directory block. 408 * Release previous if it exists. 409 */ 410 if (blkoff(fs, ndp->ni_offset) == 0) { 411 if (bp != NULL) 412 brelse(bp); 413 bp = blkatoff(dp, ndp->ni_offset, (char **)0); 414 if (bp == 0) 415 goto bad; 416 entryoffsetinblock = 0; 417 } 418 /* 419 * If still looking for a slot, and at a DIRBLKSIZE 420 * boundary, have to start looking for free space again. 421 */ 422 if (slotstatus == NONE && 423 (entryoffsetinblock&(DIRBLKSIZ-1)) == 0) { 424 slotoffset = -1; 425 slotfreespace = 0; 426 } 427 /* 428 * Get pointer to next entry. 429 * Full validation checks are slow, so we only check 430 * enough to insure forward progress through the 431 * directory. Complete checks can be run by patching 432 * "dirchk" to be true. 433 */ 434 ep = (struct direct *)(bp->b_un.b_addr + entryoffsetinblock); 435 if (ep->d_reclen == 0 || 436 dirchk && dirbadentry(ep, entryoffsetinblock)) { 437 dirbad(dp, ndp->ni_offset, "mangled entry"); 438 i = DIRBLKSIZ - (entryoffsetinblock & (DIRBLKSIZ - 1)); 439 ndp->ni_offset += i; 440 entryoffsetinblock += i; 441 continue; 442 } 443 444 /* 445 * If an appropriate sized slot has not yet been found, 446 * check to see if one is available. Also accumulate space 447 * in the current block so that we can determine if 448 * compaction is viable. 449 */ 450 if (slotstatus != FOUND) { 451 int size = ep->d_reclen; 452 453 if (ep->d_ino != 0) 454 size -= DIRSIZ(ep); 455 if (size > 0) { 456 if (size >= slotneeded) { 457 slotstatus = FOUND; 458 slotoffset = ndp->ni_offset; 459 slotsize = ep->d_reclen; 460 } else if (slotstatus == NONE) { 461 slotfreespace += size; 462 if (slotoffset == -1) 463 slotoffset = ndp->ni_offset; 464 if (slotfreespace >= slotneeded) { 465 slotstatus = COMPACT; 466 slotsize = ndp->ni_offset + 467 ep->d_reclen - slotoffset; 468 } 469 } 470 } 471 } 472 473 /* 474 * Check for a name match. 475 */ 476 if (ep->d_ino) { 477 if (ep->d_namlen == ndp->ni_dent.d_namlen && 478 !bcmp(ndp->ni_dent.d_name, ep->d_name, 479 (unsigned)ep->d_namlen)) 480 goto found; 481 } 482 prevoff = ndp->ni_offset; 483 ndp->ni_offset += ep->d_reclen; 484 entryoffsetinblock += ep->d_reclen; 485 if (ep->d_ino) 486 enduseful = ndp->ni_offset; 487 } 488 /* notfound: */ 489 /* 490 * If we started in the middle of the directory and failed 491 * to find our target, we must check the beginning as well. 492 */ 493 if (numdirpasses == 2) { 494 numdirpasses--; 495 ndp->ni_offset = 0; 496 endsearch = u.u_ncache.nc_prevoffset; 497 goto searchloop; 498 } 499 /* 500 * If creating, and at end of pathname and current 501 * directory has not been removed, then can consider 502 * allowing file to be created. 503 */ 504 if (flag == CREATE && *cp == 0 && dp->i_nlink != 0) { 505 /* 506 * Access for write is interpreted as allowing 507 * creation of files in the directory. 508 */ 509 if (access(dp, IWRITE)) 510 goto bad; 511 /* 512 * Return an indication of where the new directory 513 * entry should be put. If we didn't find a slot, 514 * then set ndp->ni_count to 0 indicating that the new 515 * slot belongs at the end of the directory. If we found 516 * a slot, then the new entry can be put in the range 517 * [ndp->ni_offset .. ndp->ni_offset + ndp->ni_count) 518 */ 519 if (slotstatus == NONE) { 520 ndp->ni_offset = roundup(dp->i_size, DIRBLKSIZ); 521 ndp->ni_count = 0; 522 enduseful = ndp->ni_offset; 523 } else { 524 ndp->ni_offset = slotoffset; 525 ndp->ni_count = slotsize; 526 if (enduseful < slotoffset + slotsize) 527 enduseful = slotoffset + slotsize; 528 } 529 ndp->ni_endoff = roundup(enduseful, DIRBLKSIZ); 530 dp->i_flag |= IUPD|ICHG; 531 if (bp) 532 brelse(bp); 533 nbp->av_forw = freenamebuf; 534 freenamebuf = nbp; 535 /* 536 * We return with the directory locked, so that 537 * the parameters we set up above will still be 538 * valid if we actually decide to do a direnter(). 539 * We return NULL to indicate that the entry doesn't 540 * currently exist, leaving a pointer to the (locked) 541 * directory inode in ndp->ni_pdir. 542 */ 543 ndp->ni_pdir = dp; 544 return (NULL); 545 } 546 u.u_error = ENOENT; 547 goto bad; 548 found: 549 if (numdirpasses == 2) 550 nchstats.ncs_pass2++; 551 /* 552 * Check that directory length properly reflects presence 553 * of this entry. 554 */ 555 if (entryoffsetinblock + DIRSIZ(ep) > dp->i_size) { 556 dirbad(dp, ndp->ni_offset, "i_size too small"); 557 dp->i_size = entryoffsetinblock + DIRSIZ(ep); 558 dp->i_flag |= IUPD|ICHG; 559 } 560 561 /* 562 * Found component in pathname. 563 * If the final component of path name, save information 564 * in the cache as to where the entry was found. 565 */ 566 if (*cp == '\0' && flag == LOOKUP) { 567 u.u_ncache.nc_prevoffset = ndp->ni_offset &~ (DIRBLKSIZ - 1); 568 u.u_ncache.nc_inumber = dp->i_number; 569 u.u_ncache.nc_dev = dp->i_dev; 570 } 571 /* 572 * Save directory entry's inode number and reclen in ndp->ni_dent, 573 * and release directory buffer. 574 */ 575 ndp->ni_dent.d_ino = ep->d_ino; 576 ndp->ni_dent.d_reclen = ep->d_reclen; 577 brelse(bp); 578 bp = NULL; 579 580 /* 581 * If deleting, and at end of pathname, return 582 * parameters which can be used to remove file. 583 * If the lockparent flag isn't set, we return only 584 * the directory (in ndp->ni_pdir), otherwise we go 585 * on and lock the inode, being careful with ".". 586 */ 587 if (flag == DELETE && *cp == 0) { 588 /* 589 * Write access to directory required to delete files. 590 */ 591 if (access(dp, IWRITE)) 592 goto bad; 593 ndp->ni_pdir = dp; /* for dirremove() */ 594 /* 595 * Return pointer to current entry in ndp->ni_offset, 596 * and distance past previous entry (if there 597 * is a previous entry in this block) in ndp->ni_count. 598 * Save directory inode pointer in ndp->ni_pdir for dirremove(). 599 */ 600 if ((ndp->ni_offset&(DIRBLKSIZ-1)) == 0) 601 ndp->ni_count = 0; 602 else 603 ndp->ni_count = ndp->ni_offset - prevoff; 604 if (lockparent) { 605 if (dp->i_number == ndp->ni_dent.d_ino) 606 dp->i_count++; 607 else { 608 dp = iget(dp->i_dev, fs, ndp->ni_dent.d_ino); 609 if (dp == NULL) { 610 iput(ndp->ni_pdir); 611 goto bad; 612 } 613 /* 614 * If directory is "sticky", then user must own 615 * the directory, or the file in it, else he 616 * may not delete it (unless he's root). This 617 * implements append-only directories. 618 */ 619 if ((ndp->ni_pdir->i_mode & ISVTX) && 620 u.u_uid != 0 && 621 u.u_uid != ndp->ni_pdir->i_uid && 622 dp->i_uid != u.u_uid) { 623 iput(ndp->ni_pdir); 624 u.u_error = EPERM; 625 goto bad; 626 } 627 } 628 } 629 nbp->av_forw = freenamebuf; 630 freenamebuf = nbp; 631 return (dp); 632 } 633 634 /* 635 * Special handling for ".." allowing chdir out of mounted 636 * file system: indirect .. in root inode to reevaluate 637 * in directory file system was mounted on. 638 */ 639 if (isdotdot) { 640 if (dp == u.u_rdir) { 641 ndp->ni_dent.d_ino = dp->i_number; 642 makeentry = 0; 643 } else if (ndp->ni_dent.d_ino == ROOTINO && 644 dp->i_number == ROOTINO) { 645 for (i = 1; i < NMOUNT; i++) 646 if (mount[i].m_bufp != NULL && 647 mount[i].m_dev == dp->i_dev) { 648 iput(dp); 649 dp = mount[i].m_inodp; 650 ILOCK(dp); 651 dp->i_count++; 652 fs = dp->i_fs; 653 cp -= 2; /* back over .. */ 654 goto dirloop2; 655 } 656 } 657 } 658 659 /* 660 * If rewriting (rename), return the inode and the 661 * information required to rewrite the present directory 662 * Must get inode of directory entry to verify it's a 663 * regular file, or empty directory. 664 */ 665 if ((flag == CREATE && lockparent) && *cp == 0) { 666 if (access(dp, IWRITE)) 667 goto bad; 668 ndp->ni_pdir = dp; /* for dirrewrite() */ 669 /* 670 * Careful about locking second inode. 671 * This can only occur if the target is ".". 672 */ 673 if (dp->i_number == ndp->ni_dent.d_ino) { 674 u.u_error = EISDIR; /* XXX */ 675 goto bad; 676 } 677 dp = iget(dp->i_dev, fs, ndp->ni_dent.d_ino); 678 if (dp == NULL) { 679 iput(ndp->ni_pdir); 680 goto bad; 681 } 682 nbp->av_forw = freenamebuf; 683 freenamebuf = nbp; 684 return (dp); 685 } 686 687 /* 688 * Check for symbolic link, which may require us to massage the 689 * name before we continue translation. We do not `iput' the 690 * directory because we may need it again if the symbolic link 691 * is relative to the current directory. Instead we save it 692 * unlocked as "pdp". We must get the target inode before unlocking 693 * the directory to insure that the inode will not be removed 694 * before we get it. We prevent deadlock by always fetching 695 * inodes from the root, moving down the directory tree. Thus 696 * when following backward pointers ".." we must unlock the 697 * parent directory before getting the requested directory. 698 * There is a potential race condition here if both the current 699 * and parent directories are removed before the `iget' for the 700 * inode associated with ".." returns. We hope that this occurs 701 * infrequently since we cannot avoid this race condition without 702 * implementing a sophisticated deadlock detection algorithm. 703 * Note also that this simple deadlock detection scheme will not 704 * work if the file system has any hard links other than ".." 705 * that point backwards in the directory structure. 706 */ 707 pdp = dp; 708 if (isdotdot) { 709 IUNLOCK(pdp); /* race to get the inode */ 710 dp = iget(dp->i_dev, fs, ndp->ni_dent.d_ino); 711 if (dp == NULL) 712 goto bad2; 713 } else if (dp->i_number == ndp->ni_dent.d_ino) { 714 dp->i_count++; /* we want ourself, ie "." */ 715 } else { 716 dp = iget(dp->i_dev, fs, ndp->ni_dent.d_ino); 717 IUNLOCK(pdp); 718 if (dp == NULL) 719 goto bad2; 720 } 721 722 /* 723 * Insert name into cache if appropriate. 724 */ 725 if (makeentry) { 726 if (ncp != NULL) 727 panic("namei: duplicating cache"); 728 /* 729 * Free the cache slot at head of lru chain. 730 */ 731 if (ncp = nchhead) { 732 /* remove from lru chain */ 733 *ncp->nc_prev = ncp->nc_nxt; 734 if (ncp->nc_nxt) 735 ncp->nc_nxt->nc_prev = ncp->nc_prev; 736 else 737 nchtail = ncp->nc_prev; 738 remque(ncp); /* remove from old hash chain */ 739 /* grab the inode we just found */ 740 ncp->nc_ip = dp; 741 /* fill in cache info */ 742 ncp->nc_ino = pdp->i_number; /* parents inum */ 743 ncp->nc_dev = pdp->i_dev; /* & device */ 744 ncp->nc_idev = dp->i_dev; /* our device */ 745 ncp->nc_id = dp->i_id; /* identifier */ 746 ncp->nc_nlen = ndp->ni_dent.d_namlen; 747 bcopy(ndp->ni_dent.d_name, ncp->nc_name, 748 (unsigned)ncp->nc_nlen); 749 /* link at end of lru chain */ 750 ncp->nc_nxt = NULL; 751 ncp->nc_prev = nchtail; 752 *nchtail = ncp; 753 nchtail = &ncp->nc_nxt; 754 /* and insert on hash chain */ 755 insque(ncp, nhp); 756 } 757 } 758 759 haveino: 760 fs = dp->i_fs; 761 762 /* 763 * Check for symbolic link 764 */ 765 if ((dp->i_mode & IFMT) == IFLNK && 766 ((ndp->ni_nameiop & FOLLOW) || *cp == '/')) { 767 u_int pathlen = strlen(cp) + 1; 768 769 if (dp->i_size + pathlen >= MAXPATHLEN - 1) { 770 u.u_error = ENAMETOOLONG; 771 goto bad2; 772 } 773 if (++nlink > MAXSYMLINKS) { 774 u.u_error = ELOOP; 775 goto bad2; 776 } 777 ovbcopy(cp, nbp->b_un.b_addr + dp->i_size, pathlen); 778 u.u_error = 779 rdwri(UIO_READ, dp, nbp->b_un.b_addr, (int)dp->i_size, 780 (off_t)0, 1, (int *)0); 781 if (u.u_error) 782 goto bad2; 783 cp = nbp->b_un.b_addr; 784 iput(dp); 785 if (*cp == '/') { 786 irele(pdp); 787 while (*cp == '/') 788 cp++; 789 if ((dp = u.u_rdir) == NULL) 790 dp = rootdir; 791 ILOCK(dp); 792 dp->i_count++; 793 } else { 794 dp = pdp; 795 ILOCK(dp); 796 } 797 fs = dp->i_fs; 798 goto dirloop; 799 } 800 801 /* 802 * Not a symbolic link. If more pathname, 803 * continue at next component, else return. 804 */ 805 if (*cp == '/') { 806 while (*cp == '/') 807 cp++; 808 irele(pdp); 809 goto dirloop; 810 } 811 nbp->av_forw = freenamebuf; 812 freenamebuf = nbp; 813 if (lockparent) 814 ndp->ni_pdir = pdp; 815 else 816 irele(pdp); 817 return (dp); 818 bad2: 819 irele(pdp); 820 bad: 821 if (bp) 822 brelse(bp); 823 if (dp) 824 iput(dp); 825 nbp->av_forw = freenamebuf; 826 freenamebuf = nbp; 827 return (NULL); 828 } 829 830 831 dirbad(ip, offset, how) 832 struct inode *ip; 833 off_t offset; 834 char *how; 835 { 836 837 printf("%s: bad dir ino %d at offset %d: %s\n", 838 ip->i_fs->fs_fsmnt, ip->i_number, offset, how); 839 } 840 841 /* 842 * Do consistency checking on a directory entry: 843 * record length must be multiple of 4 844 * entry must fit in rest of its DIRBLKSIZ block 845 * record must be large enough to contain entry 846 * name is not longer than MAXNAMLEN 847 * name must be as long as advertised, and null terminated 848 */ 849 dirbadentry(ep, entryoffsetinblock) 850 register struct direct *ep; 851 int entryoffsetinblock; 852 { 853 register int i; 854 855 if ((ep->d_reclen & 0x3) != 0 || 856 ep->d_reclen > DIRBLKSIZ - (entryoffsetinblock & (DIRBLKSIZ - 1)) || 857 ep->d_reclen < DIRSIZ(ep) || ep->d_namlen > MAXNAMLEN) 858 return (1); 859 for (i = 0; i < ep->d_namlen; i++) 860 if (ep->d_name[i] == '\0') 861 return (1); 862 return (ep->d_name[i]); 863 } 864 865 /* 866 * Write a directory entry after a call to namei, using the parameters 867 * which it left in the u. area. The argument ip is the inode which 868 * the new directory entry will refer to. The u. area field ndp->ni_pdir is 869 * a pointer to the directory to be written, which was left locked by 870 * namei. Remaining parameters (ndp->ni_offset, ndp->ni_count) indicate 871 * how the space for the new entry is to be gotten. 872 */ 873 direnter(ip, ndp) 874 struct inode *ip; 875 register struct nameidata *ndp; 876 { 877 register struct direct *ep, *nep; 878 register struct inode *dp = ndp->ni_pdir; 879 struct buf *bp; 880 int loc, spacefree, error = 0; 881 u_int dsize; 882 int newentrysize; 883 char *dirbuf; 884 885 ndp->ni_dent.d_ino = ip->i_number; 886 newentrysize = DIRSIZ(&ndp->ni_dent); 887 if (ndp->ni_count == 0) { 888 /* 889 * If ndp->ni_count is 0, then namei could find no space in the 890 * directory. In this case ndp->ni_offset will be on a directory 891 * block boundary and we will write the new entry into a fresh 892 * block. 893 */ 894 if (ndp->ni_offset&(DIRBLKSIZ-1)) 895 panic("wdir: newblk"); 896 ndp->ni_dent.d_reclen = DIRBLKSIZ; 897 error = rdwri(UIO_WRITE, dp, (caddr_t)&ndp->ni_dent, 898 newentrysize, ndp->ni_offset, 1, (int *)0); 899 if (DIRBLKSIZ > dp->i_fs->fs_fsize) 900 panic("wdir: blksize"); /* XXX - should grow w/bmap() */ 901 else 902 dp->i_size = roundup(dp->i_size, DIRBLKSIZ); 903 iput(dp); 904 return (error); 905 } 906 907 /* 908 * If ndp->ni_count is non-zero, then namei found space for the new 909 * entry in the range ndp->ni_offset to ndp->ni_offset + ndp->ni_count. 910 * in the directory. To use this space, we may have to compact 911 * the entries located there, by copying them together towards 912 * the beginning of the block, leaving the free space in 913 * one usable chunk at the end. 914 */ 915 916 /* 917 * Increase size of directory if entry eats into new space. 918 * This should never push the size past a new multiple of 919 * DIRBLKSIZE. 920 * 921 * N.B. - THIS IS AN ARTIFACT OF 4.2 AND SHOULD NEVER HAPPEN. 922 */ 923 if (ndp->ni_offset + ndp->ni_count > dp->i_size) 924 dp->i_size = ndp->ni_offset + ndp->ni_count; 925 /* 926 * Get the block containing the space for the new directory 927 * entry. Should return error by result instead of u.u_error. 928 */ 929 bp = blkatoff(dp, ndp->ni_offset, (char **)&dirbuf); 930 if (bp == 0) { 931 iput(dp); 932 return (u.u_error); 933 } 934 /* 935 * Find space for the new entry. In the simple case, the 936 * entry at offset base will have the space. If it does 937 * not, then namei arranged that compacting the region 938 * ndp->ni_offset to ndp->ni_offset+ndp->ni_count would yield the space. 939 */ 940 ep = (struct direct *)dirbuf; 941 dsize = DIRSIZ(ep); 942 spacefree = ep->d_reclen - dsize; 943 for (loc = ep->d_reclen; loc < ndp->ni_count; ) { 944 nep = (struct direct *)(dirbuf + loc); 945 if (ep->d_ino) { 946 /* trim the existing slot */ 947 ep->d_reclen = dsize; 948 ep = (struct direct *)((char *)ep + dsize); 949 } else { 950 /* overwrite; nothing there; header is ours */ 951 spacefree += dsize; 952 } 953 dsize = DIRSIZ(nep); 954 spacefree += nep->d_reclen - dsize; 955 loc += nep->d_reclen; 956 bcopy((caddr_t)nep, (caddr_t)ep, dsize); 957 } 958 /* 959 * Update the pointer fields in the previous entry (if any), 960 * copy in the new entry, and write out the block. 961 */ 962 if (ep->d_ino == 0) { 963 if (spacefree + dsize < newentrysize) 964 panic("wdir: compact1"); 965 ndp->ni_dent.d_reclen = spacefree + dsize; 966 } else { 967 if (spacefree < newentrysize) 968 panic("wdir: compact2"); 969 ndp->ni_dent.d_reclen = spacefree; 970 ep->d_reclen = dsize; 971 ep = (struct direct *)((char *)ep + dsize); 972 } 973 bcopy((caddr_t)&ndp->ni_dent, (caddr_t)ep, (u_int)newentrysize); 974 bwrite(bp); 975 dp->i_flag |= IUPD|ICHG; 976 if (ndp->ni_endoff && ndp->ni_endoff < dp->i_size) 977 itrunc(dp, (u_long)ndp->ni_endoff); 978 iput(dp); 979 return (error); 980 } 981 982 /* 983 * Remove a directory entry after a call to namei, using the 984 * parameters which it left in the u. area. The u. entry 985 * ni_offset contains the offset into the directory of the 986 * entry to be eliminated. The ni_count field contains the 987 * size of the previous record in the directory. If this 988 * is 0, the first entry is being deleted, so we need only 989 * zero the inode number to mark the entry as free. If the 990 * entry isn't the first in the directory, we must reclaim 991 * the space of the now empty record by adding the record size 992 * to the size of the previous entry. 993 */ 994 dirremove(ndp) 995 register struct nameidata *ndp; 996 { 997 register struct inode *dp = ndp->ni_pdir; 998 register struct buf *bp; 999 struct direct *ep; 1000 1001 if (ndp->ni_count == 0) { 1002 /* 1003 * First entry in block: set d_ino to zero. 1004 */ 1005 ndp->ni_dent.d_ino = 0; 1006 (void) rdwri(UIO_WRITE, dp, (caddr_t)&ndp->ni_dent, 1007 (int)DIRSIZ(&ndp->ni_dent), ndp->ni_offset, 1, (int *)0); 1008 } else { 1009 /* 1010 * Collapse new free space into previous entry. 1011 */ 1012 bp = blkatoff(dp, ndp->ni_offset - ndp->ni_count, (char **)&ep); 1013 if (bp == 0) 1014 return (0); 1015 ep->d_reclen += ndp->ni_dent.d_reclen; 1016 bwrite(bp); 1017 dp->i_flag |= IUPD|ICHG; 1018 } 1019 return (1); 1020 } 1021 1022 /* 1023 * Rewrite an existing directory entry to point at the inode 1024 * supplied. The parameters describing the directory entry are 1025 * set up by a call to namei. 1026 */ 1027 dirrewrite(dp, ip, ndp) 1028 struct inode *dp, *ip; 1029 struct nameidata *ndp; 1030 { 1031 1032 ndp->ni_dent.d_ino = ip->i_number; 1033 u.u_error = rdwri(UIO_WRITE, dp, (caddr_t)&ndp->ni_dent, 1034 (int)DIRSIZ(&ndp->ni_dent), ndp->ni_offset, 1, (int *)0); 1035 iput(dp); 1036 } 1037 1038 /* 1039 * Return buffer with contents of block "offset" 1040 * from the beginning of directory "ip". If "res" 1041 * is non-zero, fill it in with a pointer to the 1042 * remaining space in the directory. 1043 */ 1044 struct buf * 1045 blkatoff(ip, offset, res) 1046 struct inode *ip; 1047 off_t offset; 1048 char **res; 1049 { 1050 register struct fs *fs = ip->i_fs; 1051 daddr_t lbn = lblkno(fs, offset); 1052 int bsize = blksize(fs, ip, lbn); 1053 register struct buf *bp; 1054 daddr_t bn; 1055 1056 bn = bmap(ip, lbn, B_READ, bsize); 1057 if (u.u_error) 1058 return (0); 1059 if (bn == (daddr_t)-1) { 1060 dirbad(ip, offset, "hole in dir"); 1061 return (0); 1062 } 1063 bp = bread(ip->i_dev, fsbtodb(fs, bn), bsize); 1064 if (bp->b_flags & B_ERROR) { 1065 brelse(bp); 1066 return (0); 1067 } 1068 if (res) 1069 *res = bp->b_un.b_addr + blkoff(fs, offset); 1070 return (bp); 1071 } 1072 1073 /* 1074 * Check if a directory is empty or not. 1075 * Inode supplied must be locked. 1076 * 1077 * Using a struct dirtemplate here is not precisely 1078 * what we want, but better than using a struct direct. 1079 * 1080 * NB: does not handle corrupted directories. 1081 */ 1082 dirempty(ip, parentino) 1083 register struct inode *ip; 1084 ino_t parentino; 1085 { 1086 register off_t off; 1087 struct dirtemplate dbuf; 1088 register struct direct *dp = (struct direct *)&dbuf; 1089 int error, count; 1090 #define MINDIRSIZ (sizeof (struct dirtemplate) / 2) 1091 1092 for (off = 0; off < ip->i_size; off += dp->d_reclen) { 1093 error = rdwri(UIO_READ, ip, (caddr_t)dp, MINDIRSIZ, 1094 off, 1, &count); 1095 /* 1096 * Since we read MINDIRSIZ, residual must 1097 * be 0 unless we're at end of file. 1098 */ 1099 if (error || count != 0) 1100 return (0); 1101 /* avoid infinite loops */ 1102 if (dp->d_reclen == 0) 1103 return (0); 1104 /* skip empty entries */ 1105 if (dp->d_ino == 0) 1106 continue; 1107 /* accept only "." and ".." */ 1108 if (dp->d_namlen > 2) 1109 return (0); 1110 if (dp->d_name[0] != '.') 1111 return (0); 1112 /* 1113 * At this point d_namlen must be 1 or 2. 1114 * 1 implies ".", 2 implies ".." if second 1115 * char is also "." 1116 */ 1117 if (dp->d_namlen == 1) 1118 continue; 1119 if (dp->d_name[1] == '.' && dp->d_ino == parentino) 1120 continue; 1121 return (0); 1122 } 1123 return (1); 1124 } 1125 1126 /* 1127 * Check if source directory is in the path of the target directory. 1128 * Target is supplied locked, source is unlocked. 1129 * The target is always iput() before returning. 1130 */ 1131 checkpath(source, target) 1132 struct inode *source, *target; 1133 { 1134 struct dirtemplate dirbuf; 1135 register struct inode *ip; 1136 int error = 0; 1137 1138 ip = target; 1139 if (ip->i_number == source->i_number) { 1140 error = EEXIST; 1141 goto out; 1142 } 1143 if (ip->i_number == ROOTINO) 1144 goto out; 1145 1146 for (;;) { 1147 if ((ip->i_mode&IFMT) != IFDIR) { 1148 error = ENOTDIR; 1149 break; 1150 } 1151 error = rdwri(UIO_READ, ip, (caddr_t)&dirbuf, 1152 sizeof (struct dirtemplate), (off_t)0, 1, (int *)0); 1153 if (error != 0) 1154 break; 1155 if (dirbuf.dotdot_namlen != 2 || 1156 dirbuf.dotdot_name[0] != '.' || 1157 dirbuf.dotdot_name[1] != '.') { 1158 error = ENOTDIR; 1159 break; 1160 } 1161 if (dirbuf.dotdot_ino == source->i_number) { 1162 error = EINVAL; 1163 break; 1164 } 1165 if (dirbuf.dotdot_ino == ROOTINO) 1166 break; 1167 iput(ip); 1168 ip = iget(ip->i_dev, ip->i_fs, dirbuf.dotdot_ino); 1169 if (ip == NULL) { 1170 error = u.u_error; 1171 break; 1172 } 1173 } 1174 1175 out: 1176 if (error == ENOTDIR) 1177 printf("checkpath: .. not a directory\n"); 1178 if (ip != NULL) 1179 iput(ip); 1180 return (error); 1181 } 1182 1183 /* 1184 * Name cache initialization, from main() when we are booting 1185 */ 1186 nchinit() 1187 { 1188 register union nchash *nchp; 1189 register struct namecache *ncp; 1190 1191 nchhead = 0; 1192 nchtail = &nchhead; 1193 for (ncp = namecache; ncp < &namecache[nchsize]; ncp++) { 1194 ncp->nc_forw = ncp; /* hash chain */ 1195 ncp->nc_back = ncp; 1196 ncp->nc_nxt = NULL; /* lru chain */ 1197 *nchtail = ncp; 1198 ncp->nc_prev = nchtail; 1199 nchtail = &ncp->nc_nxt; 1200 /* all else is zero already */ 1201 } 1202 for (nchp = nchash; nchp < &nchash[NCHHASH]; nchp++) { 1203 nchp->nch_head[0] = nchp; 1204 nchp->nch_head[1] = nchp; 1205 } 1206 } 1207 1208 /* 1209 * Cache flush, called when filesys is umounted to 1210 * remove entries that would now be invalid 1211 * 1212 * The line "nxtcp = nchhead" near the end is to avoid potential problems 1213 * if the cache lru chain is modified while we are dumping the 1214 * inode. This makes the algorithm O(n^2), but do you think I care? 1215 */ 1216 nchinval(dev) 1217 register dev_t dev; 1218 { 1219 register struct namecache *ncp, *nxtcp; 1220 1221 for (ncp = nchhead; ncp; ncp = nxtcp) { 1222 nxtcp = ncp->nc_nxt; 1223 if (ncp->nc_ip == NULL || 1224 (ncp->nc_idev != dev && ncp->nc_dev != dev)) 1225 continue; 1226 /* free the resources we had */ 1227 ncp->nc_idev = NODEV; 1228 ncp->nc_dev = NODEV; 1229 ncp->nc_id = NULL; 1230 ncp->nc_ino = 0; 1231 ncp->nc_ip = NULL; 1232 remque(ncp); /* remove entry from its hash chain */ 1233 ncp->nc_forw = ncp; /* and make a dummy one */ 1234 ncp->nc_back = ncp; 1235 /* delete this entry from LRU chain */ 1236 *ncp->nc_prev = nxtcp; 1237 if (nxtcp) 1238 nxtcp->nc_prev = ncp->nc_prev; 1239 else 1240 nchtail = ncp->nc_prev; 1241 /* cause rescan of list, it may have altered */ 1242 nxtcp = nchhead; 1243 /* put the now-free entry at head of LRU */ 1244 ncp->nc_nxt = nxtcp; 1245 ncp->nc_prev = &nchhead; 1246 nxtcp->nc_prev = &ncp->nc_nxt; 1247 nchhead = ncp; 1248 } 1249 } 1250 1251 /* 1252 * Name cache invalidation of all entries. 1253 */ 1254 cacheinvalall() 1255 { 1256 register struct namecache *ncp; 1257 1258 for (ncp = namecache; ncp < &namecache[nchsize]; ncp++) 1259 ncp->nc_id = 0; 1260 } 1261