1bcca6c6bSrsc // File system implementation. 2bcca6c6bSrsc // 3bcca6c6bSrsc // Four layers: 4bcca6c6bSrsc // + Blocks: allocator for raw disk blocks. 5bcca6c6bSrsc // + Files: inode allocator, reading, writing, metadata. 6bcca6c6bSrsc // + Directories: inode with special contents (list of other inodes!) 7bcca6c6bSrsc // + Names: paths like /usr/rtm/xv6/fs.c for convenient naming. 8bcca6c6bSrsc // 94d39b633Srsc // Disk layout is: superblock, inodes, block in-use bitmap, data blocks. 10eaea18cbSrsc // 11eaea18cbSrsc // This file contains the low-level file system manipulation 12eaea18cbSrsc // routines. The (higher-level) system call implementations 13eaea18cbSrsc // are in sysfile.c. 14bcca6c6bSrsc 1511a9947fSrtm #include "types.h" 161f544842Skaashoek #include "stat.h" 1711a9947fSrtm #include "param.h" 1811a9947fSrtm #include "x86.h" 1911a9947fSrtm #include "mmu.h" 2011a9947fSrtm #include "proc.h" 2111a9947fSrtm #include "defs.h" 2211a9947fSrtm #include "spinlock.h" 2311a9947fSrtm #include "buf.h" 2411a9947fSrtm #include "fs.h" 2511a9947fSrtm #include "fsvar.h" 266fa5ffb5Skaashoek #include "dev.h" 2711a9947fSrtm 28bcca6c6bSrsc #define min(a, b) ((a) < (b) ? (a) : (b)) 29fbf91039Srsc static void itrunc(struct inode*); 3011a9947fSrtm 31bcca6c6bSrsc // Blocks. 325be0039cSrtm 33f5527388Srsc // Allocate a disk block. 3424111398Skaashoek static uint 3524111398Skaashoek balloc(uint dev) 3624111398Skaashoek { 377d4aef6cSrsc int b, bi, m, ninodes, size; 3824111398Skaashoek struct buf *bp; 3924111398Skaashoek struct superblock *sb; 4024111398Skaashoek 4124111398Skaashoek bp = bread(dev, 1); 4224111398Skaashoek sb = (struct superblock*) bp->data; 4324111398Skaashoek size = sb->size; 4424111398Skaashoek ninodes = sb->ninodes; 4524111398Skaashoek 4624111398Skaashoek for(b = 0; b < size; b++) { 4724111398Skaashoek if(b % BPB == 0) { 4824111398Skaashoek brelse(bp); 4924111398Skaashoek bp = bread(dev, BBLOCK(b, ninodes)); 5024111398Skaashoek } 5124111398Skaashoek bi = b % BPB; 5224111398Skaashoek m = 0x1 << (bi % 8); 5324111398Skaashoek if((bp->data[bi/8] & m) == 0) { // is block free? 54902b13f5Srtm bp->data[bi/8] |= m; 55eaea18cbSrsc bwrite(bp); // mark it allocated on disk 5628d9ef04Skaashoek brelse(bp); 5724111398Skaashoek return b; 5824111398Skaashoek } 597d4aef6cSrsc } 607d4aef6cSrsc panic("balloc: out of blocks"); 617d4aef6cSrsc } 6224111398Skaashoek 63bb207a1dSrsc // Free a disk block. 6428d9ef04Skaashoek static void 6528d9ef04Skaashoek bfree(int dev, uint b) 6628d9ef04Skaashoek { 6728d9ef04Skaashoek struct buf *bp; 6828d9ef04Skaashoek struct superblock *sb; 697d4aef6cSrsc int bi, m, ninodes; 7028d9ef04Skaashoek 7128d9ef04Skaashoek bp = bread(dev, 1); 7228d9ef04Skaashoek sb = (struct superblock*) bp->data; 7328d9ef04Skaashoek ninodes = sb->ninodes; 7428d9ef04Skaashoek brelse(bp); 7528d9ef04Skaashoek 76c372e8dcSkaashoek bp = bread(dev, b); 77c372e8dcSkaashoek memset(bp->data, 0, BSIZE); 78eaea18cbSrsc bwrite(bp); 79c372e8dcSkaashoek brelse(bp); 80c372e8dcSkaashoek 8128d9ef04Skaashoek bp = bread(dev, BBLOCK(b, ninodes)); 8228d9ef04Skaashoek bi = b % BPB; 837d4aef6cSrsc m = 0x1 << (bi % 8); 84902b13f5Srtm if((bp->data[bi/8] & m) == 0) 85902b13f5Srtm panic("freeing free block"); 867d4aef6cSrsc bp->data[bi/8] &= ~m; 87eaea18cbSrsc bwrite(bp); // mark it free on disk 8828d9ef04Skaashoek brelse(bp); 8928d9ef04Skaashoek } 9024111398Skaashoek 91bcca6c6bSrsc // Inodes 92bcca6c6bSrsc // 93bcca6c6bSrsc // The inodes are laid out sequentially on disk immediately after 94bcca6c6bSrsc // the superblock. The kernel keeps a cache of the in-use 95bcca6c6bSrsc // on-disk structures to provide a place for synchronizing access 96bcca6c6bSrsc // to inodes shared between multiple processes. 97bcca6c6bSrsc // 98902b13f5Srtm // ip->ref counts the number of pointer references to this cached 99bcca6c6bSrsc // inode; references are typically kept in struct file and in cp->cwd. 100bcca6c6bSrsc // When ip->ref falls to zero, the inode is no longer cached. 101bcca6c6bSrsc // It is an error to use an inode without holding a reference to it. 102bcca6c6bSrsc // 103902b13f5Srtm // Inodes can be locked with I_BUSY (like bufs and B_BUSY). 104eaea18cbSrsc // Processes are only allowed to read and write inode 105eaea18cbSrsc // metadata and contents when holding the inode's lock. 106902b13f5Srtm // Because inode locks are held during disk accesses, 107902b13f5Srtm // they are implemented using a flag rather than with 108902b13f5Srtm // spin locks. Callers are responsible for locking 109eaea18cbSrsc // inodes before passing them to routines in this file; leaving 110eaea18cbSrsc // this responsibility with the caller makes it possible for them 111eaea18cbSrsc // to create arbitrarily-sized atomic operations. 112eaea18cbSrsc // 113eaea18cbSrsc // To give maximum control over locking to the callers, 114eaea18cbSrsc // the routines in this file that return inode pointers 115eaea18cbSrsc // return pointers to *unlocked* inodes. It is the callers' 116902b13f5Srtm // responsibility to lock them before using them. A non-zero 117902b13f5Srtm // ip->ref keeps these unlocked inodes in the cache. 118bcca6c6bSrsc 119bcca6c6bSrsc struct { 120bcca6c6bSrsc struct spinlock lock; 121bcca6c6bSrsc struct inode inode[NINODE]; 122bcca6c6bSrsc } icache; 123bcca6c6bSrsc 124bcca6c6bSrsc void 125bcca6c6bSrsc iinit(void) 126bcca6c6bSrsc { 127bcca6c6bSrsc initlock(&icache.lock, "icache.lock"); 128bcca6c6bSrsc } 129bcca6c6bSrsc 130f5527388Srsc // Find the inode with number inum on device dev 131eaea18cbSrsc // and return the in-memory copy. h 13207090dd7Srsc static struct inode* 13311a9947fSrtm iget(uint dev, uint inum) 13411a9947fSrtm { 135bcca6c6bSrsc struct inode *ip, *empty; 13611a9947fSrtm 137bcca6c6bSrsc acquire(&icache.lock); 13811a9947fSrtm 139bcca6c6bSrsc // Try for cached inode. 140bcca6c6bSrsc empty = 0; 141bcca6c6bSrsc for(ip = &icache.inode[0]; ip < &icache.inode[NINODE]; ip++){ 1420d6bbd31Srsc if(ip->ref > 0 && ip->dev == dev && ip->inum == inum){ 1430d6bbd31Srsc ip->ref++; 144bcca6c6bSrsc release(&icache.lock); 14507090dd7Srsc return ip; 14611a9947fSrtm } 147bcca6c6bSrsc if(empty == 0 && ip->ref == 0) // Remember empty slot. 148bcca6c6bSrsc empty = ip; 14911a9947fSrtm } 15011a9947fSrtm 151bcca6c6bSrsc // Allocate fresh inode. 152bcca6c6bSrsc if(empty == 0) 15332eea766Srsc panic("iget: no inodes"); 15411a9947fSrtm 155bcca6c6bSrsc ip = empty; 156bcca6c6bSrsc ip->dev = dev; 157bcca6c6bSrsc ip->inum = inum; 158bcca6c6bSrsc ip->ref = 1; 159f32f3638Srsc ip->flags = 0; 160bcca6c6bSrsc release(&icache.lock); 16111a9947fSrtm 16207090dd7Srsc return ip; 163f32f3638Srsc } 164f32f3638Srsc 165eaea18cbSrsc // Increment reference count for ip. 166eaea18cbSrsc // Returns ip to enable ip = idup(ip1) idiom. 16707090dd7Srsc struct inode* 16807090dd7Srsc idup(struct inode *ip) 169f32f3638Srsc { 170eaea18cbSrsc acquire(&icache.lock); 171eaea18cbSrsc ip->ref++; 172eaea18cbSrsc release(&icache.lock); 17307090dd7Srsc return ip; 174f32f3638Srsc } 175f32f3638Srsc 176f32f3638Srsc // Lock the given inode. 17707090dd7Srsc void 17807090dd7Srsc ilock(struct inode *ip) 179f32f3638Srsc { 180f32f3638Srsc struct buf *bp; 181f32f3638Srsc struct dinode *dip; 182eaea18cbSrsc 18307090dd7Srsc if(ip == 0 || ip->ref < 1) 18407090dd7Srsc panic("ilock"); 185f32f3638Srsc 186f32f3638Srsc acquire(&icache.lock); 187f32f3638Srsc while(ip->flags & I_BUSY) 188f32f3638Srsc sleep(ip, &icache.lock); 189f32f3638Srsc ip->flags |= I_BUSY; 190f32f3638Srsc release(&icache.lock); 191f32f3638Srsc 192f32f3638Srsc if(!(ip->flags & I_VALID)){ 193f32f3638Srsc bp = bread(ip->dev, IBLOCK(ip->inum)); 194f32f3638Srsc dip = &((struct dinode*)(bp->data))[ip->inum % IPB]; 195bcca6c6bSrsc ip->type = dip->type; 196bcca6c6bSrsc ip->major = dip->major; 197bcca6c6bSrsc ip->minor = dip->minor; 198bcca6c6bSrsc ip->nlink = dip->nlink; 199bcca6c6bSrsc ip->size = dip->size; 200bcca6c6bSrsc memmove(ip->addrs, dip->addrs, sizeof(ip->addrs)); 20111a9947fSrtm brelse(bp); 202f32f3638Srsc ip->flags |= I_VALID; 203eaea18cbSrsc if(ip->type == 0) 204eaea18cbSrsc panic("ilock: no type"); 20511a9947fSrtm } 206bcca6c6bSrsc } 207bcca6c6bSrsc 208bcca6c6bSrsc // Unlock the given inode. 20907090dd7Srsc void 210bcca6c6bSrsc iunlock(struct inode *ip) 211bcca6c6bSrsc { 21207090dd7Srsc if(ip == 0 || !(ip->flags & I_BUSY) || ip->ref < 1) 213bcca6c6bSrsc panic("iunlock"); 214bcca6c6bSrsc 215bcca6c6bSrsc acquire(&icache.lock); 216f32f3638Srsc ip->flags &= ~I_BUSY; 217bcca6c6bSrsc wakeup(ip); 218bcca6c6bSrsc release(&icache.lock); 219bcca6c6bSrsc } 220bcca6c6bSrsc 221f32f3638Srsc // Caller holds reference to unlocked ip. Drop reference. 222bcca6c6bSrsc void 22307090dd7Srsc iput(struct inode *ip) 224bcca6c6bSrsc { 225f32f3638Srsc acquire(&icache.lock); 226f32f3638Srsc if(ip->ref == 1 && (ip->flags & I_VALID) && ip->nlink == 0) { 227f32f3638Srsc // inode is no longer used: truncate and free inode. 228f32f3638Srsc if(ip->flags & I_BUSY) 229eaea18cbSrsc panic("iput busy"); 230f32f3638Srsc ip->flags |= I_BUSY; 231f32f3638Srsc release(&icache.lock); 232f32f3638Srsc // XXX convince rsc that no one will come find this inode. 233f32f3638Srsc itrunc(ip); 234f32f3638Srsc ip->type = 0; 235f32f3638Srsc iupdate(ip); 236f32f3638Srsc acquire(&icache.lock); 237f32f3638Srsc ip->flags &= ~I_BUSY; 238f32f3638Srsc } 239f32f3638Srsc ip->ref--; 240f32f3638Srsc release(&icache.lock); 241bcca6c6bSrsc } 242bcca6c6bSrsc 24307090dd7Srsc void 24407090dd7Srsc iunlockput(struct inode *ip) 24507090dd7Srsc { 24607090dd7Srsc iunlock(ip); 24707090dd7Srsc iput(ip); 24807090dd7Srsc } 24907090dd7Srsc 250*8d2e9a48Srsc //PAGEBREAK! 251bcca6c6bSrsc // Allocate a new inode with the given type on device dev. 25207090dd7Srsc struct inode* 253e8d11c2eSkaashoek ialloc(uint dev, short type) 254e8d11c2eSkaashoek { 255f32f3638Srsc int inum, ninodes; 256f32f3638Srsc struct buf *bp; 2577d4aef6cSrsc struct dinode *dip; 258e8d11c2eSkaashoek struct superblock *sb; 259e8d11c2eSkaashoek 260e8d11c2eSkaashoek bp = bread(dev, 1); 26124111398Skaashoek sb = (struct superblock*)bp->data; 262e8d11c2eSkaashoek ninodes = sb->ninodes; 263e8d11c2eSkaashoek brelse(bp); 264e8d11c2eSkaashoek 265e8d11c2eSkaashoek for(inum = 1; inum < ninodes; inum++) { // loop over inode blocks 26624111398Skaashoek bp = bread(dev, IBLOCK(inum)); 267e8d11c2eSkaashoek dip = &((struct dinode*)(bp->data))[inum % IPB]; 268e8d11c2eSkaashoek if(dip->type == 0) { // a free inode 2692aa4c3bcSrtm memset(dip, 0, sizeof(*dip)); 270e8d11c2eSkaashoek dip->type = type; 271eaea18cbSrsc bwrite(bp); // mark it allocated on the disk 272e8d11c2eSkaashoek brelse(bp); 273f32f3638Srsc return iget(dev, inum); 274e8d11c2eSkaashoek } 27595c07f82Srsc brelse(bp); 27695c07f82Srsc } 27795c07f82Srsc panic("ialloc: no inodes"); 27895c07f82Srsc } 279e8d11c2eSkaashoek 280bcca6c6bSrsc // Copy inode, which has changed, from memory to disk. 281eaea18cbSrsc void 282bcca6c6bSrsc iupdate(struct inode *ip) 283bcca6c6bSrsc { 284bcca6c6bSrsc struct buf *bp; 285bcca6c6bSrsc struct dinode *dip; 286bcca6c6bSrsc 287bcca6c6bSrsc bp = bread(ip->dev, IBLOCK(ip->inum)); 288bcca6c6bSrsc dip = &((struct dinode*)(bp->data))[ip->inum % IPB]; 289bcca6c6bSrsc dip->type = ip->type; 290bcca6c6bSrsc dip->major = ip->major; 291bcca6c6bSrsc dip->minor = ip->minor; 292bcca6c6bSrsc dip->nlink = ip->nlink; 293bcca6c6bSrsc dip->size = ip->size; 294bcca6c6bSrsc memmove(dip->addrs, ip->addrs, sizeof(ip->addrs)); 295eaea18cbSrsc bwrite(bp); 296bcca6c6bSrsc brelse(bp); 297bcca6c6bSrsc } 298bcca6c6bSrsc 299*8d2e9a48Srsc //PAGEBREAK! 300bcca6c6bSrsc // Inode contents 301bcca6c6bSrsc // 302bcca6c6bSrsc // The contents (data) associated with each inode is stored 303bcca6c6bSrsc // in a sequence of blocks on the disk. The first NDIRECT blocks 304bcca6c6bSrsc // are stored in ip->addrs[]. The next NINDIRECT blocks are 305bcca6c6bSrsc // listed in the block ip->addrs[INDIRECT]. 3069d3fb671Srtm 307bb207a1dSrsc // Return the disk block address of the nth block in inode ip. 308eaea18cbSrsc // If there is no such block, alloc controls whether one is allocated. 309eaea18cbSrsc static uint 310bcca6c6bSrsc bmap(struct inode *ip, uint bn, int alloc) 31122bac2cbSkaashoek { 312bcca6c6bSrsc uint addr, *a; 313bcca6c6bSrsc struct buf *bp; 31422bac2cbSkaashoek 315ea2909b6Skaashoek if(bn < NDIRECT) { 316bcca6c6bSrsc if((addr = ip->addrs[bn]) == 0) { 317bcca6c6bSrsc if(!alloc) 318bcca6c6bSrsc return -1; 319bcca6c6bSrsc ip->addrs[bn] = addr = balloc(ip->dev); 320ea2909b6Skaashoek } 321bcca6c6bSrsc return addr; 322bcca6c6bSrsc } 323bcca6c6bSrsc bn -= NDIRECT; 324bcca6c6bSrsc 325bcca6c6bSrsc if(bn < NINDIRECT) { 326bcca6c6bSrsc // Load indirect block, allocating if necessary. 327bcca6c6bSrsc if((addr = ip->addrs[INDIRECT]) == 0) { 328bcca6c6bSrsc if(!alloc) 329bcca6c6bSrsc return -1; 330bcca6c6bSrsc ip->addrs[INDIRECT] = addr = balloc(ip->dev); 331bcca6c6bSrsc } 332bcca6c6bSrsc bp = bread(ip->dev, addr); 333bcca6c6bSrsc a = (uint*)bp->data; 334bcca6c6bSrsc 335bcca6c6bSrsc if((addr = a[bn]) == 0) { 336bcca6c6bSrsc if(!alloc) { 337bcca6c6bSrsc brelse(bp); 338bcca6c6bSrsc return -1; 339bcca6c6bSrsc } 340bcca6c6bSrsc a[bn] = addr = balloc(ip->dev); 341eaea18cbSrsc bwrite(bp); 342bcca6c6bSrsc } 343bcca6c6bSrsc brelse(bp); 344bcca6c6bSrsc return addr; 34522bac2cbSkaashoek } 34622bac2cbSkaashoek 347bcca6c6bSrsc panic("bmap: out of range"); 348bcca6c6bSrsc } 349bcca6c6bSrsc 350eaea18cbSrsc // PAGEBREAK: 30 351bcca6c6bSrsc // Truncate inode (discard contents). 352fbf91039Srsc static void 3532aa4c3bcSrtm itrunc(struct inode *ip) 35422bac2cbSkaashoek { 355ea2909b6Skaashoek int i, j; 356bcca6c6bSrsc struct buf *bp; 3577d4aef6cSrsc uint *a; 35822bac2cbSkaashoek 359bcca6c6bSrsc for(i = 0; i < NDIRECT; i++) { 360bcca6c6bSrsc if(ip->addrs[i]) { 36122bac2cbSkaashoek bfree(ip->dev, ip->addrs[i]); 36222bac2cbSkaashoek ip->addrs[i] = 0; 36322bac2cbSkaashoek } 36422bac2cbSkaashoek } 365bcca6c6bSrsc 366bcca6c6bSrsc if(ip->addrs[INDIRECT]) { 367bcca6c6bSrsc bp = bread(ip->dev, ip->addrs[INDIRECT]); 368bcca6c6bSrsc a = (uint*)bp->data; 369bcca6c6bSrsc for(j = 0; j < NINDIRECT; j++) { 370bcca6c6bSrsc if(a[j]) 371bcca6c6bSrsc bfree(ip->dev, a[j]); 372bcca6c6bSrsc } 373bcca6c6bSrsc brelse(bp); 374bcca6c6bSrsc ip->addrs[INDIRECT] = 0; 375bcca6c6bSrsc } 376bcca6c6bSrsc 37722bac2cbSkaashoek ip->size = 0; 37822bac2cbSkaashoek iupdate(ip); 37922bac2cbSkaashoek } 38022bac2cbSkaashoek 381bb207a1dSrsc // Copy stat information from inode. 382e958c538Skaashoek void 3831f544842Skaashoek stati(struct inode *ip, struct stat *st) 3841f544842Skaashoek { 3851dca3afbSrsc st->dev = ip->dev; 3861dca3afbSrsc st->ino = ip->inum; 3871dca3afbSrsc st->type = ip->type; 3881dca3afbSrsc st->nlink = ip->nlink; 3891dca3afbSrsc st->size = ip->size; 3901f544842Skaashoek } 3911f544842Skaashoek 392eaea18cbSrsc //PAGEBREAK! 393bb207a1dSrsc // Read data from inode. 394c59361f1Srtm int 39517a85657Srtm readi(struct inode *ip, char *dst, uint off, uint n) 396c59361f1Srtm { 397bcca6c6bSrsc uint tot, m; 398c59361f1Srtm struct buf *bp; 399c59361f1Srtm 400939f9edeSkaashoek if(ip->type == T_DEV) { 4011dca3afbSrsc if(ip->major < 0 || ip->major >= NDEV || !devsw[ip->major].read) 402939f9edeSkaashoek return -1; 4031dca3afbSrsc return devsw[ip->major].read(ip->minor, dst, n); 404939f9edeSkaashoek } 405939f9edeSkaashoek 406bcca6c6bSrsc if(off + n < off) 407bcca6c6bSrsc return -1; 408bcca6c6bSrsc if(off + n > ip->size) 409bcca6c6bSrsc n = ip->size - off; 410bcca6c6bSrsc 411bcca6c6bSrsc for(tot=0; tot<n; tot+=m, off+=m, dst+=m) { 412bcca6c6bSrsc bp = bread(ip->dev, bmap(ip, off/BSIZE, 0)); 413bcca6c6bSrsc m = min(n - tot, BSIZE - off%BSIZE); 414bcca6c6bSrsc memmove(dst, bp->data + off%BSIZE, m); 415c59361f1Srtm brelse(bp); 416c59361f1Srtm } 417bcca6c6bSrsc return n; 418ea2909b6Skaashoek } 419ea2909b6Skaashoek 420eaea18cbSrsc // PAGEBREAK! 421bb207a1dSrsc // Write data to inode. 422ea2909b6Skaashoek int 423bcca6c6bSrsc writei(struct inode *ip, char *src, uint off, uint n) 4246fa5ffb5Skaashoek { 425bcca6c6bSrsc uint tot, m; 4267d4aef6cSrsc struct buf *bp; 4277d4aef6cSrsc 4286fa5ffb5Skaashoek if(ip->type == T_DEV) { 4291dca3afbSrsc if(ip->major < 0 || ip->major >= NDEV || !devsw[ip->major].write) 430939f9edeSkaashoek return -1; 431bcca6c6bSrsc return devsw[ip->major].write(ip->minor, src, n); 4327d4aef6cSrsc } 4337d4aef6cSrsc 434bcca6c6bSrsc if(off + n < off) 435bcca6c6bSrsc return -1; 436bcca6c6bSrsc if(off + n > MAXFILE*BSIZE) 437bcca6c6bSrsc n = MAXFILE*BSIZE - off; 438bcca6c6bSrsc 439bcca6c6bSrsc for(tot=0; tot<n; tot+=m, off+=m, src+=m) { 440bcca6c6bSrsc bp = bread(ip->dev, bmap(ip, off/BSIZE, 1)); 441bcca6c6bSrsc m = min(n - tot, BSIZE - off%BSIZE); 442bcca6c6bSrsc memmove(bp->data + off%BSIZE, src, m); 443eaea18cbSrsc bwrite(bp); 44428d9ef04Skaashoek brelse(bp); 44528d9ef04Skaashoek } 446bcca6c6bSrsc 447bcca6c6bSrsc if(n > 0 && off > ip->size) { 44848b82470Srsc ip->size = off; 44928d9ef04Skaashoek iupdate(ip); 45028d9ef04Skaashoek } 451bcca6c6bSrsc return n; 4526fa5ffb5Skaashoek } 4536fa5ffb5Skaashoek 454eaea18cbSrsc //PAGEBREAK! 455bcca6c6bSrsc // Directories 456bcca6c6bSrsc 457eaea18cbSrsc int 458fbf91039Srsc namecmp(const char *s, const char *t) 459fbf91039Srsc { 460766ba5ccSrsc return strncmp(s, t, DIRSIZ); 461fbf91039Srsc } 462fbf91039Srsc 463bcca6c6bSrsc // Look for a directory entry in a directory. 464eaea18cbSrsc // If found, set *poff to byte offset of entry. 46520365348Srtm // Caller must have already locked dp. 46607090dd7Srsc struct inode* 467fbf91039Srsc dirlookup(struct inode *dp, char *name, uint *poff) 468bcca6c6bSrsc { 469f32f3638Srsc uint off, inum; 470bcca6c6bSrsc struct buf *bp; 471bcca6c6bSrsc struct dirent *de; 472bcca6c6bSrsc 473bcca6c6bSrsc if(dp->type != T_DIR) 47420365348Srtm panic("dirlookup not DIR"); 475bcca6c6bSrsc 476bcca6c6bSrsc for(off = 0; off < dp->size; off += BSIZE){ 477bcca6c6bSrsc bp = bread(dp->dev, bmap(dp, off / BSIZE, 0)); 478bcca6c6bSrsc for(de = (struct dirent*) bp->data; 479bcca6c6bSrsc de < (struct dirent*) (bp->data + BSIZE); 480bcca6c6bSrsc de++){ 481bcca6c6bSrsc if(de->inum == 0) 482bcca6c6bSrsc continue; 483fbf91039Srsc if(namecmp(name, de->name) == 0){ 484bcca6c6bSrsc // entry matches path element 485e2a620daSrsc if(poff) 486bcca6c6bSrsc *poff = off + (uchar*)de - bp->data; 487f32f3638Srsc inum = de->inum; 488bcca6c6bSrsc brelse(bp); 489f32f3638Srsc return iget(dp->dev, inum); 490f32f3638Srsc } 491f32f3638Srsc } 492f32f3638Srsc brelse(bp); 493f32f3638Srsc } 494bcca6c6bSrsc return 0; 495bcca6c6bSrsc } 496bcca6c6bSrsc 497bcca6c6bSrsc // Write a new directory entry (name, ino) into the directory dp. 498eaea18cbSrsc int 499fbf91039Srsc dirlink(struct inode *dp, char *name, uint ino) 500bcca6c6bSrsc { 501e2a620daSrsc int off; 502bcca6c6bSrsc struct dirent de; 50307090dd7Srsc struct inode *ip; 504f32f3638Srsc 505eaea18cbSrsc // Check that name is not present. 50607090dd7Srsc if((ip = dirlookup(dp, name, 0)) != 0){ 50707090dd7Srsc iput(ip); 508f32f3638Srsc return -1; 509f32f3638Srsc } 510bcca6c6bSrsc 511bcca6c6bSrsc // Look for an empty dirent. 512bcca6c6bSrsc for(off = 0; off < dp->size; off += sizeof(de)){ 513bcca6c6bSrsc if(readi(dp, (char*)&de, off, sizeof(de)) != sizeof(de)) 514bcca6c6bSrsc panic("dirwrite read"); 515bcca6c6bSrsc if(de.inum == 0) 516bcca6c6bSrsc break; 517bcca6c6bSrsc } 518bcca6c6bSrsc 519766ba5ccSrsc strncpy(de.name, name, DIRSIZ); 520bcca6c6bSrsc de.inum = ino; 521bcca6c6bSrsc if(writei(dp, (char*)&de, off, sizeof(de)) != sizeof(de)) 522bcca6c6bSrsc panic("dirwrite"); 523f32f3638Srsc 524f32f3638Srsc return 0; 525bcca6c6bSrsc } 526bcca6c6bSrsc 527*8d2e9a48Srsc //PAGEBREAK! 528bcca6c6bSrsc // Paths 529bcca6c6bSrsc 530eaea18cbSrsc // Copy the next path element from path into name. 531eaea18cbSrsc // Return a pointer to the element following the copied one. 532eaea18cbSrsc // The returned path has no leading slashes, 533eaea18cbSrsc // so the caller can check *path=='\0' to see if the name is the last one. 534eaea18cbSrsc // If no name to remove, return 0. 535ab5c2dbbSrsc // 536ab5c2dbbSrsc // Examples: 537eaea18cbSrsc // skipelem("a/bb/c", name) = "bb/c", setting name = "a" 53820365348Srtm // skipelem("///a/bb", name) = "bb", setting name="a" 539eaea18cbSrsc // skipelem("", name) = skipelem("////", name) = 0 540ab5c2dbbSrsc // 541ab5c2dbbSrsc static char* 542fbf91039Srsc skipelem(char *path, char *name) 543ab5c2dbbSrsc { 544fbf91039Srsc char *s; 545fbf91039Srsc int len; 546fbf91039Srsc 547ab5c2dbbSrsc while(*path == '/') 548ab5c2dbbSrsc path++; 549ab5c2dbbSrsc if(*path == 0) 550ab5c2dbbSrsc return 0; 551fbf91039Srsc s = path; 552ab5c2dbbSrsc while(*path != '/' && *path != 0) 553ab5c2dbbSrsc path++; 554fbf91039Srsc len = path - s; 555fbf91039Srsc if(len >= DIRSIZ) 556fbf91039Srsc memmove(name, s, DIRSIZ); 557fbf91039Srsc else{ 558fbf91039Srsc memmove(name, s, len); 559fbf91039Srsc name[len] = 0; 560fbf91039Srsc } 561ab5c2dbbSrsc while(*path == '/') 562ab5c2dbbSrsc path++; 563ab5c2dbbSrsc return path; 564ab5c2dbbSrsc } 565ab5c2dbbSrsc 566*8d2e9a48Srsc static struct inode* _namei(char*, int, char*); 567*8d2e9a48Srsc 568*8d2e9a48Srsc struct inode* 569*8d2e9a48Srsc namei(char *path) 570*8d2e9a48Srsc { 571*8d2e9a48Srsc char name[DIRSIZ]; 572*8d2e9a48Srsc return _namei(path, 0, name); 573*8d2e9a48Srsc } 574*8d2e9a48Srsc 575*8d2e9a48Srsc struct inode* 576*8d2e9a48Srsc nameiparent(char *path, char *name) 577*8d2e9a48Srsc { 578*8d2e9a48Srsc return _namei(path, 1, name); 579*8d2e9a48Srsc } 580*8d2e9a48Srsc 581eaea18cbSrsc // Look up and return the inode for a path name. 582eaea18cbSrsc // If parent is set, return the inode for the parent 583eaea18cbSrsc // and write the final path element to name, which 584eaea18cbSrsc // should have room for DIRSIZ bytes. 58507090dd7Srsc static struct inode* 586fbf91039Srsc _namei(char *path, int parent, char *name) 5879d3fb671Srtm { 58807090dd7Srsc struct inode *ip, *next; 589f32f3638Srsc uint off; 5909d3fb671Srtm 591ab5c2dbbSrsc if(*path == '/') 59207090dd7Srsc ip = iget(ROOTDEV, 1); 593f32f3638Srsc else 59407090dd7Srsc ip = idup(cp->cwd); 5959d3fb671Srtm 596fbf91039Srsc while((path = skipelem(path, name)) != 0){ 59707090dd7Srsc ilock(ip); 59807090dd7Srsc if(ip->type != T_DIR){ 59907090dd7Srsc iunlockput(ip); 600eaea18cbSrsc return 0; 601eaea18cbSrsc } 602ab5c2dbbSrsc 603e2a620daSrsc if(parent && *path == '\0'){ 604e2a620daSrsc // Stop one level early. 60507090dd7Srsc iunlock(ip); 60607090dd7Srsc return ip; 607ab5c2dbbSrsc } 608ab5c2dbbSrsc 60907090dd7Srsc if((next = dirlookup(ip, name, &off)) == 0){ 61007090dd7Srsc iunlockput(ip); 611eaea18cbSrsc return 0; 612eaea18cbSrsc } 61307090dd7Srsc iunlockput(ip); 61407090dd7Srsc ip = next; 615ab5c2dbbSrsc } 61620365348Srtm if(parent){ 61707090dd7Srsc iput(ip); 6185051da6dSrtm return 0; 61920365348Srtm } 62007090dd7Srsc return ip; 6210633b971Skaashoek } 6229d3fb671Srtm 623