1a505fd66Srsc // File system implementation. Four layers: 2bcca6c6bSrsc // + Blocks: allocator for raw disk blocks. 3bcca6c6bSrsc // + Files: inode allocator, reading, writing, metadata. 4bcca6c6bSrsc // + Directories: inode with special contents (list of other inodes!) 5bcca6c6bSrsc // + Names: paths like /usr/rtm/xv6/fs.c for convenient naming. 6bcca6c6bSrsc // 74d39b633Srsc // Disk layout is: superblock, inodes, block in-use bitmap, data blocks. 8eaea18cbSrsc // 9eaea18cbSrsc // This file contains the low-level file system manipulation 10eaea18cbSrsc // routines. The (higher-level) system call implementations 11eaea18cbSrsc // are in sysfile.c. 12bcca6c6bSrsc 1311a9947fSrtm #include "types.h" 141f544842Skaashoek #include "stat.h" 1511a9947fSrtm #include "param.h" 1611a9947fSrtm #include "x86.h" 1711a9947fSrtm #include "mmu.h" 1811a9947fSrtm #include "proc.h" 1911a9947fSrtm #include "defs.h" 2011a9947fSrtm #include "spinlock.h" 2111a9947fSrtm #include "buf.h" 2211a9947fSrtm #include "fs.h" 2311a9947fSrtm #include "fsvar.h" 246fa5ffb5Skaashoek #include "dev.h" 2511a9947fSrtm 26bcca6c6bSrsc #define min(a, b) ((a) < (b) ? (a) : (b)) 27fbf91039Srsc static void itrunc(struct inode*); 2811a9947fSrtm 29a505fd66Srsc // Read the super block. 30a505fd66Srsc static void 31a505fd66Srsc readsb(int dev, struct superblock *sb) 32a505fd66Srsc { 33a505fd66Srsc struct buf *bp; 34a505fd66Srsc 35a505fd66Srsc bp = bread(dev, 1); 36a505fd66Srsc memmove(sb, bp->data, sizeof(*sb)); 37a505fd66Srsc brelse(bp); 38a505fd66Srsc } 39a505fd66Srsc 40a505fd66Srsc // Zero a block. 41a505fd66Srsc static void 42a505fd66Srsc bzero(int dev, int bno) 43a505fd66Srsc { 44a505fd66Srsc struct buf *bp; 45a505fd66Srsc 46a505fd66Srsc bp = bread(dev, bno); 47a505fd66Srsc memset(bp->data, 0, BSIZE); 48a505fd66Srsc bwrite(bp); 49a505fd66Srsc brelse(bp); 50a505fd66Srsc } 51a505fd66Srsc 52bcca6c6bSrsc // Blocks. 535be0039cSrtm 54f5527388Srsc // Allocate a disk block. 5524111398Skaashoek static uint 5624111398Skaashoek balloc(uint dev) 5724111398Skaashoek { 58a505fd66Srsc int b, bi, m; 5924111398Skaashoek struct buf *bp; 60a505fd66Srsc struct superblock sb; 6124111398Skaashoek 62a505fd66Srsc bp = 0; 63a505fd66Srsc readsb(dev, &sb); 64a505fd66Srsc for(b = 0; b < sb.size; b += BPB){ 65a505fd66Srsc bp = bread(dev, BBLOCK(b, sb.ninodes)); 66a505fd66Srsc for(bi = 0; bi < BPB; bi++){ 67a505fd66Srsc m = 1 << (bi % 8); 68a505fd66Srsc if((bp->data[bi/8] & m) == 0){ // Is block free? 69a505fd66Srsc bp->data[bi/8] |= m; // Mark block in use on disk. 70a505fd66Srsc bwrite(bp); 7124111398Skaashoek brelse(bp); 72a505fd66Srsc return b + bi; 7324111398Skaashoek } 74a505fd66Srsc } 7528d9ef04Skaashoek brelse(bp); 767d4aef6cSrsc } 777d4aef6cSrsc panic("balloc: out of blocks"); 787d4aef6cSrsc } 7924111398Skaashoek 80bb207a1dSrsc // Free a disk block. 8128d9ef04Skaashoek static void 8228d9ef04Skaashoek bfree(int dev, uint b) 8328d9ef04Skaashoek { 8428d9ef04Skaashoek struct buf *bp; 85a505fd66Srsc struct superblock sb; 86a505fd66Srsc int bi, m; 8728d9ef04Skaashoek 88a505fd66Srsc bzero(dev, b); 8928d9ef04Skaashoek 90a505fd66Srsc readsb(dev, &sb); 91a505fd66Srsc bp = bread(dev, BBLOCK(b, sb.ninodes)); 9228d9ef04Skaashoek bi = b % BPB; 93a505fd66Srsc m = 1 << (bi % 8); 94902b13f5Srtm if((bp->data[bi/8] & m) == 0) 95902b13f5Srtm panic("freeing free block"); 96a505fd66Srsc bp->data[bi/8] &= ~m; // Mark block free on disk. 97a505fd66Srsc bwrite(bp); 9828d9ef04Skaashoek brelse(bp); 9928d9ef04Skaashoek } 10024111398Skaashoek 101*6c34f97cSrsc // Inodes. 102*6c34f97cSrsc // 103*6c34f97cSrsc // An inode is a single, unnamed file in the file system. 104*6c34f97cSrsc // The inode disk structure holds metadata (the type, device numbers, 105*6c34f97cSrsc // and data size) along with a list of blocks where the associated 106*6c34f97cSrsc // data can be found. 107bcca6c6bSrsc // 108bcca6c6bSrsc // The inodes are laid out sequentially on disk immediately after 109bcca6c6bSrsc // the superblock. The kernel keeps a cache of the in-use 110bcca6c6bSrsc // on-disk structures to provide a place for synchronizing access 111bcca6c6bSrsc // to inodes shared between multiple processes. 112bcca6c6bSrsc // 113902b13f5Srtm // ip->ref counts the number of pointer references to this cached 114bcca6c6bSrsc // inode; references are typically kept in struct file and in cp->cwd. 115bcca6c6bSrsc // When ip->ref falls to zero, the inode is no longer cached. 116bcca6c6bSrsc // It is an error to use an inode without holding a reference to it. 117bcca6c6bSrsc // 118eaea18cbSrsc // Processes are only allowed to read and write inode 119*6c34f97cSrsc // metadata and contents when holding the inode's lock, 120*6c34f97cSrsc // represented by the I_BUSY flag in the in-memory copy. 121902b13f5Srtm // Because inode locks are held during disk accesses, 122902b13f5Srtm // they are implemented using a flag rather than with 123902b13f5Srtm // spin locks. Callers are responsible for locking 124eaea18cbSrsc // inodes before passing them to routines in this file; leaving 125eaea18cbSrsc // this responsibility with the caller makes it possible for them 126eaea18cbSrsc // to create arbitrarily-sized atomic operations. 127eaea18cbSrsc // 128eaea18cbSrsc // To give maximum control over locking to the callers, 129eaea18cbSrsc // the routines in this file that return inode pointers 130eaea18cbSrsc // return pointers to *unlocked* inodes. It is the callers' 131902b13f5Srtm // responsibility to lock them before using them. A non-zero 132902b13f5Srtm // ip->ref keeps these unlocked inodes in the cache. 133bcca6c6bSrsc 134bcca6c6bSrsc struct { 135bcca6c6bSrsc struct spinlock lock; 136bcca6c6bSrsc struct inode inode[NINODE]; 137bcca6c6bSrsc } icache; 138bcca6c6bSrsc 139bcca6c6bSrsc void 140bcca6c6bSrsc iinit(void) 141bcca6c6bSrsc { 142bcca6c6bSrsc initlock(&icache.lock, "icache.lock"); 143bcca6c6bSrsc } 144bcca6c6bSrsc 145f5527388Srsc // Find the inode with number inum on device dev 146eaea18cbSrsc // and return the in-memory copy. h 14707090dd7Srsc static struct inode* 14811a9947fSrtm iget(uint dev, uint inum) 14911a9947fSrtm { 150bcca6c6bSrsc struct inode *ip, *empty; 15111a9947fSrtm 152bcca6c6bSrsc acquire(&icache.lock); 15311a9947fSrtm 154bcca6c6bSrsc // Try for cached inode. 155bcca6c6bSrsc empty = 0; 156bcca6c6bSrsc for(ip = &icache.inode[0]; ip < &icache.inode[NINODE]; ip++){ 1570d6bbd31Srsc if(ip->ref > 0 && ip->dev == dev && ip->inum == inum){ 1580d6bbd31Srsc ip->ref++; 159bcca6c6bSrsc release(&icache.lock); 16007090dd7Srsc return ip; 16111a9947fSrtm } 162bcca6c6bSrsc if(empty == 0 && ip->ref == 0) // Remember empty slot. 163bcca6c6bSrsc empty = ip; 16411a9947fSrtm } 16511a9947fSrtm 166bcca6c6bSrsc // Allocate fresh inode. 167bcca6c6bSrsc if(empty == 0) 16832eea766Srsc panic("iget: no inodes"); 16911a9947fSrtm 170bcca6c6bSrsc ip = empty; 171bcca6c6bSrsc ip->dev = dev; 172bcca6c6bSrsc ip->inum = inum; 173bcca6c6bSrsc ip->ref = 1; 174f32f3638Srsc ip->flags = 0; 175bcca6c6bSrsc release(&icache.lock); 17611a9947fSrtm 17707090dd7Srsc return ip; 178f32f3638Srsc } 179f32f3638Srsc 180eaea18cbSrsc // Increment reference count for ip. 181eaea18cbSrsc // Returns ip to enable ip = idup(ip1) idiom. 18207090dd7Srsc struct inode* 18307090dd7Srsc idup(struct inode *ip) 184f32f3638Srsc { 185eaea18cbSrsc acquire(&icache.lock); 186eaea18cbSrsc ip->ref++; 187eaea18cbSrsc release(&icache.lock); 18807090dd7Srsc return ip; 189f32f3638Srsc } 190f32f3638Srsc 191f32f3638Srsc // Lock the given inode. 19207090dd7Srsc void 19307090dd7Srsc ilock(struct inode *ip) 194f32f3638Srsc { 195f32f3638Srsc struct buf *bp; 196f32f3638Srsc struct dinode *dip; 197eaea18cbSrsc 19807090dd7Srsc if(ip == 0 || ip->ref < 1) 19907090dd7Srsc panic("ilock"); 200f32f3638Srsc 201f32f3638Srsc acquire(&icache.lock); 202f32f3638Srsc while(ip->flags & I_BUSY) 203f32f3638Srsc sleep(ip, &icache.lock); 204f32f3638Srsc ip->flags |= I_BUSY; 205f32f3638Srsc release(&icache.lock); 206f32f3638Srsc 207f32f3638Srsc if(!(ip->flags & I_VALID)){ 208f32f3638Srsc bp = bread(ip->dev, IBLOCK(ip->inum)); 209f32f3638Srsc dip = &((struct dinode*)(bp->data))[ip->inum % IPB]; 210bcca6c6bSrsc ip->type = dip->type; 211bcca6c6bSrsc ip->major = dip->major; 212bcca6c6bSrsc ip->minor = dip->minor; 213bcca6c6bSrsc ip->nlink = dip->nlink; 214bcca6c6bSrsc ip->size = dip->size; 215bcca6c6bSrsc memmove(ip->addrs, dip->addrs, sizeof(ip->addrs)); 21611a9947fSrtm brelse(bp); 217f32f3638Srsc ip->flags |= I_VALID; 218eaea18cbSrsc if(ip->type == 0) 219eaea18cbSrsc panic("ilock: no type"); 22011a9947fSrtm } 221bcca6c6bSrsc } 222bcca6c6bSrsc 223bcca6c6bSrsc // Unlock the given inode. 22407090dd7Srsc void 225bcca6c6bSrsc iunlock(struct inode *ip) 226bcca6c6bSrsc { 22707090dd7Srsc if(ip == 0 || !(ip->flags & I_BUSY) || ip->ref < 1) 228bcca6c6bSrsc panic("iunlock"); 229bcca6c6bSrsc 230bcca6c6bSrsc acquire(&icache.lock); 231f32f3638Srsc ip->flags &= ~I_BUSY; 232bcca6c6bSrsc wakeup(ip); 233bcca6c6bSrsc release(&icache.lock); 234bcca6c6bSrsc } 235bcca6c6bSrsc 236f32f3638Srsc // Caller holds reference to unlocked ip. Drop reference. 237bcca6c6bSrsc void 23807090dd7Srsc iput(struct inode *ip) 239bcca6c6bSrsc { 240f32f3638Srsc acquire(&icache.lock); 241f32f3638Srsc if(ip->ref == 1 && (ip->flags & I_VALID) && ip->nlink == 0) { 242f32f3638Srsc // inode is no longer used: truncate and free inode. 243f32f3638Srsc if(ip->flags & I_BUSY) 244eaea18cbSrsc panic("iput busy"); 245f32f3638Srsc ip->flags |= I_BUSY; 246f32f3638Srsc release(&icache.lock); 247f32f3638Srsc // XXX convince rsc that no one will come find this inode. 248f32f3638Srsc itrunc(ip); 249f32f3638Srsc ip->type = 0; 250f32f3638Srsc iupdate(ip); 251f32f3638Srsc acquire(&icache.lock); 252f32f3638Srsc ip->flags &= ~I_BUSY; 253f32f3638Srsc } 254f32f3638Srsc ip->ref--; 255f32f3638Srsc release(&icache.lock); 256bcca6c6bSrsc } 257bcca6c6bSrsc 25807090dd7Srsc void 25907090dd7Srsc iunlockput(struct inode *ip) 26007090dd7Srsc { 26107090dd7Srsc iunlock(ip); 26207090dd7Srsc iput(ip); 26307090dd7Srsc } 26407090dd7Srsc 2658d2e9a48Srsc //PAGEBREAK! 266bcca6c6bSrsc // Allocate a new inode with the given type on device dev. 26707090dd7Srsc struct inode* 268e8d11c2eSkaashoek ialloc(uint dev, short type) 269e8d11c2eSkaashoek { 270a505fd66Srsc int inum; 271f32f3638Srsc struct buf *bp; 2727d4aef6cSrsc struct dinode *dip; 273a505fd66Srsc struct superblock sb; 274e8d11c2eSkaashoek 275a505fd66Srsc readsb(dev, &sb); 276a505fd66Srsc for(inum = 1; inum < sb.ninodes; inum++) { // loop over inode blocks 27724111398Skaashoek bp = bread(dev, IBLOCK(inum)); 278e8d11c2eSkaashoek dip = &((struct dinode*)(bp->data))[inum % IPB]; 279e8d11c2eSkaashoek if(dip->type == 0) { // a free inode 2802aa4c3bcSrtm memset(dip, 0, sizeof(*dip)); 281e8d11c2eSkaashoek dip->type = type; 282eaea18cbSrsc bwrite(bp); // mark it allocated on the disk 283e8d11c2eSkaashoek brelse(bp); 284f32f3638Srsc return iget(dev, inum); 285e8d11c2eSkaashoek } 28695c07f82Srsc brelse(bp); 28795c07f82Srsc } 28895c07f82Srsc panic("ialloc: no inodes"); 28995c07f82Srsc } 290e8d11c2eSkaashoek 291bcca6c6bSrsc // Copy inode, which has changed, from memory to disk. 292eaea18cbSrsc void 293bcca6c6bSrsc iupdate(struct inode *ip) 294bcca6c6bSrsc { 295bcca6c6bSrsc struct buf *bp; 296bcca6c6bSrsc struct dinode *dip; 297bcca6c6bSrsc 298bcca6c6bSrsc bp = bread(ip->dev, IBLOCK(ip->inum)); 299bcca6c6bSrsc dip = &((struct dinode*)(bp->data))[ip->inum % IPB]; 300bcca6c6bSrsc dip->type = ip->type; 301bcca6c6bSrsc dip->major = ip->major; 302bcca6c6bSrsc dip->minor = ip->minor; 303bcca6c6bSrsc dip->nlink = ip->nlink; 304bcca6c6bSrsc dip->size = ip->size; 305bcca6c6bSrsc memmove(dip->addrs, ip->addrs, sizeof(ip->addrs)); 306eaea18cbSrsc bwrite(bp); 307bcca6c6bSrsc brelse(bp); 308bcca6c6bSrsc } 309bcca6c6bSrsc 3108d2e9a48Srsc //PAGEBREAK! 311bcca6c6bSrsc // Inode contents 312bcca6c6bSrsc // 313bcca6c6bSrsc // The contents (data) associated with each inode is stored 314bcca6c6bSrsc // in a sequence of blocks on the disk. The first NDIRECT blocks 315bcca6c6bSrsc // are stored in ip->addrs[]. The next NINDIRECT blocks are 316bcca6c6bSrsc // listed in the block ip->addrs[INDIRECT]. 3179d3fb671Srtm 318bb207a1dSrsc // Return the disk block address of the nth block in inode ip. 319eaea18cbSrsc // If there is no such block, alloc controls whether one is allocated. 320eaea18cbSrsc static uint 321bcca6c6bSrsc bmap(struct inode *ip, uint bn, int alloc) 32222bac2cbSkaashoek { 323bcca6c6bSrsc uint addr, *a; 324bcca6c6bSrsc struct buf *bp; 32522bac2cbSkaashoek 326ea2909b6Skaashoek if(bn < NDIRECT) { 327bcca6c6bSrsc if((addr = ip->addrs[bn]) == 0) { 328bcca6c6bSrsc if(!alloc) 329bcca6c6bSrsc return -1; 330bcca6c6bSrsc ip->addrs[bn] = addr = balloc(ip->dev); 331ea2909b6Skaashoek } 332bcca6c6bSrsc return addr; 333bcca6c6bSrsc } 334bcca6c6bSrsc bn -= NDIRECT; 335bcca6c6bSrsc 336bcca6c6bSrsc if(bn < NINDIRECT) { 337bcca6c6bSrsc // Load indirect block, allocating if necessary. 338bcca6c6bSrsc if((addr = ip->addrs[INDIRECT]) == 0) { 339bcca6c6bSrsc if(!alloc) 340bcca6c6bSrsc return -1; 341bcca6c6bSrsc ip->addrs[INDIRECT] = addr = balloc(ip->dev); 342bcca6c6bSrsc } 343bcca6c6bSrsc bp = bread(ip->dev, addr); 344bcca6c6bSrsc a = (uint*)bp->data; 345bcca6c6bSrsc 346bcca6c6bSrsc if((addr = a[bn]) == 0) { 347bcca6c6bSrsc if(!alloc) { 348bcca6c6bSrsc brelse(bp); 349bcca6c6bSrsc return -1; 350bcca6c6bSrsc } 351bcca6c6bSrsc a[bn] = addr = balloc(ip->dev); 352eaea18cbSrsc bwrite(bp); 353bcca6c6bSrsc } 354bcca6c6bSrsc brelse(bp); 355bcca6c6bSrsc return addr; 35622bac2cbSkaashoek } 35722bac2cbSkaashoek 358bcca6c6bSrsc panic("bmap: out of range"); 359bcca6c6bSrsc } 360bcca6c6bSrsc 361eaea18cbSrsc // PAGEBREAK: 30 362bcca6c6bSrsc // Truncate inode (discard contents). 363fbf91039Srsc static void 3642aa4c3bcSrtm itrunc(struct inode *ip) 36522bac2cbSkaashoek { 366ea2909b6Skaashoek int i, j; 367bcca6c6bSrsc struct buf *bp; 3687d4aef6cSrsc uint *a; 36922bac2cbSkaashoek 370bcca6c6bSrsc for(i = 0; i < NDIRECT; i++) { 371bcca6c6bSrsc if(ip->addrs[i]) { 37222bac2cbSkaashoek bfree(ip->dev, ip->addrs[i]); 37322bac2cbSkaashoek ip->addrs[i] = 0; 37422bac2cbSkaashoek } 37522bac2cbSkaashoek } 376bcca6c6bSrsc 377bcca6c6bSrsc if(ip->addrs[INDIRECT]) { 378bcca6c6bSrsc bp = bread(ip->dev, ip->addrs[INDIRECT]); 379bcca6c6bSrsc a = (uint*)bp->data; 380bcca6c6bSrsc for(j = 0; j < NINDIRECT; j++) { 381bcca6c6bSrsc if(a[j]) 382bcca6c6bSrsc bfree(ip->dev, a[j]); 383bcca6c6bSrsc } 384bcca6c6bSrsc brelse(bp); 385bcca6c6bSrsc ip->addrs[INDIRECT] = 0; 386bcca6c6bSrsc } 387bcca6c6bSrsc 38822bac2cbSkaashoek ip->size = 0; 38922bac2cbSkaashoek iupdate(ip); 39022bac2cbSkaashoek } 39122bac2cbSkaashoek 392bb207a1dSrsc // Copy stat information from inode. 393e958c538Skaashoek void 3941f544842Skaashoek stati(struct inode *ip, struct stat *st) 3951f544842Skaashoek { 3961dca3afbSrsc st->dev = ip->dev; 3971dca3afbSrsc st->ino = ip->inum; 3981dca3afbSrsc st->type = ip->type; 3991dca3afbSrsc st->nlink = ip->nlink; 4001dca3afbSrsc st->size = ip->size; 4011f544842Skaashoek } 4021f544842Skaashoek 403eaea18cbSrsc //PAGEBREAK! 404bb207a1dSrsc // Read data from inode. 405c59361f1Srtm int 40617a85657Srtm readi(struct inode *ip, char *dst, uint off, uint n) 407c59361f1Srtm { 408bcca6c6bSrsc uint tot, m; 409c59361f1Srtm struct buf *bp; 410c59361f1Srtm 411939f9edeSkaashoek if(ip->type == T_DEV) { 4121dca3afbSrsc if(ip->major < 0 || ip->major >= NDEV || !devsw[ip->major].read) 413939f9edeSkaashoek return -1; 4141dca3afbSrsc return devsw[ip->major].read(ip->minor, dst, n); 415939f9edeSkaashoek } 416939f9edeSkaashoek 417bcca6c6bSrsc if(off + n < off) 418bcca6c6bSrsc return -1; 419bcca6c6bSrsc if(off + n > ip->size) 420bcca6c6bSrsc n = ip->size - off; 421bcca6c6bSrsc 422bcca6c6bSrsc for(tot=0; tot<n; tot+=m, off+=m, dst+=m) { 423bcca6c6bSrsc bp = bread(ip->dev, bmap(ip, off/BSIZE, 0)); 424bcca6c6bSrsc m = min(n - tot, BSIZE - off%BSIZE); 425bcca6c6bSrsc memmove(dst, bp->data + off%BSIZE, m); 426c59361f1Srtm brelse(bp); 427c59361f1Srtm } 428bcca6c6bSrsc return n; 429ea2909b6Skaashoek } 430ea2909b6Skaashoek 431eaea18cbSrsc // PAGEBREAK! 432bb207a1dSrsc // Write data to inode. 433ea2909b6Skaashoek int 434bcca6c6bSrsc writei(struct inode *ip, char *src, uint off, uint n) 4356fa5ffb5Skaashoek { 436bcca6c6bSrsc uint tot, m; 4377d4aef6cSrsc struct buf *bp; 4387d4aef6cSrsc 4396fa5ffb5Skaashoek if(ip->type == T_DEV) { 4401dca3afbSrsc if(ip->major < 0 || ip->major >= NDEV || !devsw[ip->major].write) 441939f9edeSkaashoek return -1; 442bcca6c6bSrsc return devsw[ip->major].write(ip->minor, src, n); 4437d4aef6cSrsc } 4447d4aef6cSrsc 445bcca6c6bSrsc if(off + n < off) 446bcca6c6bSrsc return -1; 447bcca6c6bSrsc if(off + n > MAXFILE*BSIZE) 448bcca6c6bSrsc n = MAXFILE*BSIZE - off; 449bcca6c6bSrsc 450bcca6c6bSrsc for(tot=0; tot<n; tot+=m, off+=m, src+=m) { 451bcca6c6bSrsc bp = bread(ip->dev, bmap(ip, off/BSIZE, 1)); 452bcca6c6bSrsc m = min(n - tot, BSIZE - off%BSIZE); 453bcca6c6bSrsc memmove(bp->data + off%BSIZE, src, m); 454eaea18cbSrsc bwrite(bp); 45528d9ef04Skaashoek brelse(bp); 45628d9ef04Skaashoek } 457bcca6c6bSrsc 458bcca6c6bSrsc if(n > 0 && off > ip->size) { 45948b82470Srsc ip->size = off; 46028d9ef04Skaashoek iupdate(ip); 46128d9ef04Skaashoek } 462bcca6c6bSrsc return n; 4636fa5ffb5Skaashoek } 4646fa5ffb5Skaashoek 465eaea18cbSrsc //PAGEBREAK! 466bcca6c6bSrsc // Directories 467bcca6c6bSrsc 468eaea18cbSrsc int 469fbf91039Srsc namecmp(const char *s, const char *t) 470fbf91039Srsc { 471766ba5ccSrsc return strncmp(s, t, DIRSIZ); 472fbf91039Srsc } 473fbf91039Srsc 474bcca6c6bSrsc // Look for a directory entry in a directory. 475eaea18cbSrsc // If found, set *poff to byte offset of entry. 47620365348Srtm // Caller must have already locked dp. 47707090dd7Srsc struct inode* 478fbf91039Srsc dirlookup(struct inode *dp, char *name, uint *poff) 479bcca6c6bSrsc { 480f32f3638Srsc uint off, inum; 481bcca6c6bSrsc struct buf *bp; 482bcca6c6bSrsc struct dirent *de; 483bcca6c6bSrsc 484bcca6c6bSrsc if(dp->type != T_DIR) 48520365348Srtm panic("dirlookup not DIR"); 486bcca6c6bSrsc 487bcca6c6bSrsc for(off = 0; off < dp->size; off += BSIZE){ 488bcca6c6bSrsc bp = bread(dp->dev, bmap(dp, off / BSIZE, 0)); 489bcca6c6bSrsc for(de = (struct dirent*) bp->data; 490bcca6c6bSrsc de < (struct dirent*) (bp->data + BSIZE); 491bcca6c6bSrsc de++){ 492bcca6c6bSrsc if(de->inum == 0) 493bcca6c6bSrsc continue; 494fbf91039Srsc if(namecmp(name, de->name) == 0){ 495bcca6c6bSrsc // entry matches path element 496e2a620daSrsc if(poff) 497bcca6c6bSrsc *poff = off + (uchar*)de - bp->data; 498f32f3638Srsc inum = de->inum; 499bcca6c6bSrsc brelse(bp); 500f32f3638Srsc return iget(dp->dev, inum); 501f32f3638Srsc } 502f32f3638Srsc } 503f32f3638Srsc brelse(bp); 504f32f3638Srsc } 505bcca6c6bSrsc return 0; 506bcca6c6bSrsc } 507bcca6c6bSrsc 508bcca6c6bSrsc // Write a new directory entry (name, ino) into the directory dp. 509eaea18cbSrsc int 510fbf91039Srsc dirlink(struct inode *dp, char *name, uint ino) 511bcca6c6bSrsc { 512e2a620daSrsc int off; 513bcca6c6bSrsc struct dirent de; 51407090dd7Srsc struct inode *ip; 515f32f3638Srsc 516eaea18cbSrsc // Check that name is not present. 51707090dd7Srsc if((ip = dirlookup(dp, name, 0)) != 0){ 51807090dd7Srsc iput(ip); 519f32f3638Srsc return -1; 520f32f3638Srsc } 521bcca6c6bSrsc 522bcca6c6bSrsc // Look for an empty dirent. 523bcca6c6bSrsc for(off = 0; off < dp->size; off += sizeof(de)){ 524bcca6c6bSrsc if(readi(dp, (char*)&de, off, sizeof(de)) != sizeof(de)) 525bcca6c6bSrsc panic("dirwrite read"); 526bcca6c6bSrsc if(de.inum == 0) 527bcca6c6bSrsc break; 528bcca6c6bSrsc } 529bcca6c6bSrsc 530766ba5ccSrsc strncpy(de.name, name, DIRSIZ); 531bcca6c6bSrsc de.inum = ino; 532bcca6c6bSrsc if(writei(dp, (char*)&de, off, sizeof(de)) != sizeof(de)) 533bcca6c6bSrsc panic("dirwrite"); 534f32f3638Srsc 535f32f3638Srsc return 0; 536bcca6c6bSrsc } 537bcca6c6bSrsc 5388d2e9a48Srsc //PAGEBREAK! 539bcca6c6bSrsc // Paths 540bcca6c6bSrsc 541eaea18cbSrsc // Copy the next path element from path into name. 542eaea18cbSrsc // Return a pointer to the element following the copied one. 543eaea18cbSrsc // The returned path has no leading slashes, 544eaea18cbSrsc // so the caller can check *path=='\0' to see if the name is the last one. 545eaea18cbSrsc // If no name to remove, return 0. 546ab5c2dbbSrsc // 547ab5c2dbbSrsc // Examples: 548eaea18cbSrsc // skipelem("a/bb/c", name) = "bb/c", setting name = "a" 54920365348Srtm // skipelem("///a/bb", name) = "bb", setting name="a" 550eaea18cbSrsc // skipelem("", name) = skipelem("////", name) = 0 551ab5c2dbbSrsc // 552ab5c2dbbSrsc static char* 553fbf91039Srsc skipelem(char *path, char *name) 554ab5c2dbbSrsc { 555fbf91039Srsc char *s; 556fbf91039Srsc int len; 557fbf91039Srsc 558ab5c2dbbSrsc while(*path == '/') 559ab5c2dbbSrsc path++; 560ab5c2dbbSrsc if(*path == 0) 561ab5c2dbbSrsc return 0; 562fbf91039Srsc s = path; 563ab5c2dbbSrsc while(*path != '/' && *path != 0) 564ab5c2dbbSrsc path++; 565fbf91039Srsc len = path - s; 566fbf91039Srsc if(len >= DIRSIZ) 567fbf91039Srsc memmove(name, s, DIRSIZ); 568fbf91039Srsc else{ 569fbf91039Srsc memmove(name, s, len); 570fbf91039Srsc name[len] = 0; 571fbf91039Srsc } 572ab5c2dbbSrsc while(*path == '/') 573ab5c2dbbSrsc path++; 574ab5c2dbbSrsc return path; 575ab5c2dbbSrsc } 576ab5c2dbbSrsc 5778d2e9a48Srsc static struct inode* _namei(char*, int, char*); 5788d2e9a48Srsc 5798d2e9a48Srsc struct inode* 5808d2e9a48Srsc namei(char *path) 5818d2e9a48Srsc { 5828d2e9a48Srsc char name[DIRSIZ]; 5838d2e9a48Srsc return _namei(path, 0, name); 5848d2e9a48Srsc } 5858d2e9a48Srsc 5868d2e9a48Srsc struct inode* 5878d2e9a48Srsc nameiparent(char *path, char *name) 5888d2e9a48Srsc { 5898d2e9a48Srsc return _namei(path, 1, name); 5908d2e9a48Srsc } 5918d2e9a48Srsc 592eaea18cbSrsc // Look up and return the inode for a path name. 593eaea18cbSrsc // If parent is set, return the inode for the parent 594eaea18cbSrsc // and write the final path element to name, which 595eaea18cbSrsc // should have room for DIRSIZ bytes. 59607090dd7Srsc static struct inode* 597fbf91039Srsc _namei(char *path, int parent, char *name) 5989d3fb671Srtm { 59907090dd7Srsc struct inode *ip, *next; 600f32f3638Srsc uint off; 6019d3fb671Srtm 602ab5c2dbbSrsc if(*path == '/') 60307090dd7Srsc ip = iget(ROOTDEV, 1); 604f32f3638Srsc else 60507090dd7Srsc ip = idup(cp->cwd); 6069d3fb671Srtm 607fbf91039Srsc while((path = skipelem(path, name)) != 0){ 60807090dd7Srsc ilock(ip); 60907090dd7Srsc if(ip->type != T_DIR){ 61007090dd7Srsc iunlockput(ip); 611eaea18cbSrsc return 0; 612eaea18cbSrsc } 613ab5c2dbbSrsc 614e2a620daSrsc if(parent && *path == '\0'){ 615e2a620daSrsc // Stop one level early. 61607090dd7Srsc iunlock(ip); 61707090dd7Srsc return ip; 618ab5c2dbbSrsc } 619ab5c2dbbSrsc 62007090dd7Srsc if((next = dirlookup(ip, name, &off)) == 0){ 62107090dd7Srsc iunlockput(ip); 622eaea18cbSrsc return 0; 623eaea18cbSrsc } 62407090dd7Srsc iunlockput(ip); 62507090dd7Srsc ip = next; 626ab5c2dbbSrsc } 62720365348Srtm if(parent){ 62807090dd7Srsc iput(ip); 6295051da6dSrtm return 0; 63020365348Srtm } 63107090dd7Srsc return ip; 6320633b971Skaashoek } 6339d3fb671Srtm 634