1a5fbfe41SRobert Morris // File system implementation. Five layers: 2bcca6c6bSrsc // + Blocks: allocator for raw disk blocks. 3a5fbfe41SRobert Morris // + Log: crash recovery for multi-step updates. 4bcca6c6bSrsc // + Files: inode allocator, reading, writing, metadata. 5bcca6c6bSrsc // + Directories: inode with special contents (list of other inodes!) 6bcca6c6bSrsc // + Names: paths like /usr/rtm/xv6/fs.c for convenient naming. 7bcca6c6bSrsc // 8eaea18cbSrsc // This file contains the low-level file system manipulation 9eaea18cbSrsc // routines. The (higher-level) system call implementations 10eaea18cbSrsc // are in sysfile.c. 11bcca6c6bSrsc 1211a9947fSrtm #include "types.h" 13558ab49fSrsc #include "defs.h" 1411a9947fSrtm #include "param.h" 15558ab49fSrsc #include "stat.h" 1611a9947fSrtm #include "mmu.h" 1711a9947fSrtm #include "proc.h" 1811a9947fSrtm #include "spinlock.h" 1911a9947fSrtm #include "fs.h" 20*c24ac5d7SFrans Kaashoek #include "buf.h" 210aef8914SRuss Cox #include "file.h" 2211a9947fSrtm 23bcca6c6bSrsc #define min(a, b) ((a) < (b) ? (a) : (b)) 24fbf91039Srsc static void itrunc(struct inode*); 2511a9947fSrtm 26a505fd66Srsc // Read the super block. 2713a96baeSFrans Kaashoek void 28a505fd66Srsc readsb(int dev, struct superblock *sb) 29a505fd66Srsc { 30a505fd66Srsc struct buf *bp; 31a505fd66Srsc 32a505fd66Srsc bp = bread(dev, 1); 33a505fd66Srsc memmove(sb, bp->data, sizeof(*sb)); 34a505fd66Srsc brelse(bp); 35a505fd66Srsc } 36a505fd66Srsc 37a505fd66Srsc // Zero a block. 38a505fd66Srsc static void 39a505fd66Srsc bzero(int dev, int bno) 40a505fd66Srsc { 41a505fd66Srsc struct buf *bp; 42a505fd66Srsc 43a505fd66Srsc bp = bread(dev, bno); 44a505fd66Srsc memset(bp->data, 0, BSIZE); 455053dd6aSRobert Morris log_write(bp); 46a505fd66Srsc brelse(bp); 47a505fd66Srsc } 48a505fd66Srsc 49bcca6c6bSrsc // Blocks. 505be0039cSrtm 515053dd6aSRobert Morris // Allocate a zeroed disk block. 5224111398Skaashoek static uint 5324111398Skaashoek balloc(uint dev) 5424111398Skaashoek { 55a505fd66Srsc int b, bi, m; 5624111398Skaashoek struct buf *bp; 57a505fd66Srsc struct superblock sb; 5824111398Skaashoek 59a505fd66Srsc bp = 0; 60a505fd66Srsc readsb(dev, &sb); 61a505fd66Srsc for(b = 0; b < sb.size; b += BPB){ 62a505fd66Srsc bp = bread(dev, BBLOCK(b, sb.ninodes)); 63a5fbfe41SRobert Morris for(bi = 0; bi < BPB && b + bi < sb.size; bi++){ 64a505fd66Srsc m = 1 << (bi % 8); 65a505fd66Srsc if((bp->data[bi/8] & m) == 0){ // Is block free? 66a5fbfe41SRobert Morris bp->data[bi/8] |= m; // Mark block in use. 6713a96baeSFrans Kaashoek log_write(bp); 6824111398Skaashoek brelse(bp); 695053dd6aSRobert Morris bzero(dev, b + bi); 70a505fd66Srsc return b + bi; 7124111398Skaashoek } 72a505fd66Srsc } 7328d9ef04Skaashoek brelse(bp); 747d4aef6cSrsc } 757d4aef6cSrsc panic("balloc: out of blocks"); 767d4aef6cSrsc } 7724111398Skaashoek 78bb207a1dSrsc // Free a disk block. 7928d9ef04Skaashoek static void 8028d9ef04Skaashoek bfree(int dev, uint b) 8128d9ef04Skaashoek { 8228d9ef04Skaashoek struct buf *bp; 83a505fd66Srsc struct superblock sb; 84a505fd66Srsc int bi, m; 8528d9ef04Skaashoek 86a505fd66Srsc readsb(dev, &sb); 87a505fd66Srsc bp = bread(dev, BBLOCK(b, sb.ninodes)); 8828d9ef04Skaashoek bi = b % BPB; 89a505fd66Srsc m = 1 << (bi % 8); 90902b13f5Srtm if((bp->data[bi/8] & m) == 0) 91902b13f5Srtm panic("freeing free block"); 92a5fbfe41SRobert Morris bp->data[bi/8] &= ~m; 9313a96baeSFrans Kaashoek log_write(bp); 9428d9ef04Skaashoek brelse(bp); 9528d9ef04Skaashoek } 9624111398Skaashoek 976c34f97cSrsc // Inodes. 986c34f97cSrsc // 99a5fbfe41SRobert Morris // An inode describes a single unnamed file. 100a5fbfe41SRobert Morris // The inode disk structure holds metadata: the file's type, 101a5fbfe41SRobert Morris // its size, the number of links referring to it, and the 102a5fbfe41SRobert Morris // list of blocks holding the file's content. 103bcca6c6bSrsc // 104bcca6c6bSrsc // The inodes are laid out sequentially on disk immediately after 105a5fbfe41SRobert Morris // the superblock. Each inode has a number, indicating its 106a5fbfe41SRobert Morris // position on the disk. 107a5fbfe41SRobert Morris // 108a5fbfe41SRobert Morris // The kernel keeps a cache of in-use inodes in memory 109a5fbfe41SRobert Morris // to provide a place for synchronizing access 110a5fbfe41SRobert Morris // to inodes used by multiple processes. The cached 111a5fbfe41SRobert Morris // inodes include book-keeping information that is 112a5fbfe41SRobert Morris // not stored on disk: ip->ref and ip->flags. 113bcca6c6bSrsc // 11438eee5bcSRobert Morris // An inode and its in-memory represtative go through a 11538eee5bcSRobert Morris // sequence of states before they can be used by the 11638eee5bcSRobert Morris // rest of the file system code. 117bcca6c6bSrsc // 11838eee5bcSRobert Morris // * Allocation: an inode is allocated if its type (on disk) 11938eee5bcSRobert Morris // is non-zero. ialloc() allocates, iput() frees if 12038eee5bcSRobert Morris // the link count has fallen to zero. 121eaea18cbSrsc // 12238eee5bcSRobert Morris // * Referencing in cache: an entry in the inode cache 12338eee5bcSRobert Morris // is free if ip->ref is zero. Otherwise ip->ref tracks 12438eee5bcSRobert Morris // the number of in-memory pointers to the entry (open 12538eee5bcSRobert Morris // files and current directories). iget() to find or 12638eee5bcSRobert Morris // create a cache entry and increment its ref, iput() 12738eee5bcSRobert Morris // to decrement ref. 128a5fbfe41SRobert Morris // 12938eee5bcSRobert Morris // * Valid: the information (type, size, &c) in an inode 13038eee5bcSRobert Morris // cache entry is only correct when the I_VALID bit 13138eee5bcSRobert Morris // is set in ip->flags. ilock() reads the inode from 13238eee5bcSRobert Morris // the disk and sets I_VALID, while iput() clears 13338eee5bcSRobert Morris // I_VALID if ip->ref has fallen to zero. 134a5fbfe41SRobert Morris // 13538eee5bcSRobert Morris // * Locked: file system code may only examine and modify 13638eee5bcSRobert Morris // the information in an inode and its content if it 13738eee5bcSRobert Morris // has first locked the inode. The I_BUSY flag indicates 13838eee5bcSRobert Morris // that the inode is locked. ilock() sets I_BUSY, 13938eee5bcSRobert Morris // while iunlock clears it. 14038eee5bcSRobert Morris // 14138eee5bcSRobert Morris // Thus a typical sequence is: 14238eee5bcSRobert Morris // ip = iget(dev, inum) 14338eee5bcSRobert Morris // ilock(ip) 14438eee5bcSRobert Morris // ... examine and modify ip->xxx ... 14538eee5bcSRobert Morris // iunlock(ip) 14638eee5bcSRobert Morris // iput(ip) 14738eee5bcSRobert Morris // 14838eee5bcSRobert Morris // ilock() is separate from iget() so that system calls can 14938eee5bcSRobert Morris // get a long-term reference to an inode (as for an open file) 15038eee5bcSRobert Morris // and only lock it for short periods (e.g., in read()). 15138eee5bcSRobert Morris // The separation also helps avoid deadlock and races during 15238eee5bcSRobert Morris // pathname lookup. iget() increments ip->ref so that the inode 15338eee5bcSRobert Morris // stays cached and pointers to it remain valid. 15438eee5bcSRobert Morris // 15538eee5bcSRobert Morris // Many internal file system functions expect the caller to 15638eee5bcSRobert Morris // have locked the inodes involved; this lets callers create 15738eee5bcSRobert Morris // multi-step atomic operations. 158bcca6c6bSrsc 159bcca6c6bSrsc struct { 160bcca6c6bSrsc struct spinlock lock; 161bcca6c6bSrsc struct inode inode[NINODE]; 162bcca6c6bSrsc } icache; 163bcca6c6bSrsc 164bcca6c6bSrsc void 165bcca6c6bSrsc iinit(void) 166bcca6c6bSrsc { 16734295f46Srsc initlock(&icache.lock, "icache"); 168bcca6c6bSrsc } 169bcca6c6bSrsc 170f9a06440SRuss Cox static struct inode* iget(uint dev, uint inum); 171f9a06440SRuss Cox 172f9a06440SRuss Cox //PAGEBREAK! 173f9a06440SRuss Cox // Allocate a new inode with the given type on device dev. 174a5fbfe41SRobert Morris // A free inode has a type of zero. 175f9a06440SRuss Cox struct inode* 176f9a06440SRuss Cox ialloc(uint dev, short type) 177f9a06440SRuss Cox { 178f9a06440SRuss Cox int inum; 179f9a06440SRuss Cox struct buf *bp; 180f9a06440SRuss Cox struct dinode *dip; 181f9a06440SRuss Cox struct superblock sb; 182f9a06440SRuss Cox 183f9a06440SRuss Cox readsb(dev, &sb); 184a5fbfe41SRobert Morris 185a5fbfe41SRobert Morris for(inum = 1; inum < sb.ninodes; inum++){ 186f9a06440SRuss Cox bp = bread(dev, IBLOCK(inum)); 187f9a06440SRuss Cox dip = (struct dinode*)bp->data + inum%IPB; 188f9a06440SRuss Cox if(dip->type == 0){ // a free inode 189f9a06440SRuss Cox memset(dip, 0, sizeof(*dip)); 190f9a06440SRuss Cox dip->type = type; 19113a96baeSFrans Kaashoek log_write(bp); // mark it allocated on the disk 192f9a06440SRuss Cox brelse(bp); 193f9a06440SRuss Cox return iget(dev, inum); 194f9a06440SRuss Cox } 195f9a06440SRuss Cox brelse(bp); 196f9a06440SRuss Cox } 197f9a06440SRuss Cox panic("ialloc: no inodes"); 198f9a06440SRuss Cox } 199f9a06440SRuss Cox 20038eee5bcSRobert Morris // Copy a modified in-memory inode to disk. 201f9a06440SRuss Cox void 202f9a06440SRuss Cox iupdate(struct inode *ip) 203f9a06440SRuss Cox { 204f9a06440SRuss Cox struct buf *bp; 205f9a06440SRuss Cox struct dinode *dip; 206f9a06440SRuss Cox 207f9a06440SRuss Cox bp = bread(ip->dev, IBLOCK(ip->inum)); 208f9a06440SRuss Cox dip = (struct dinode*)bp->data + ip->inum%IPB; 209f9a06440SRuss Cox dip->type = ip->type; 210f9a06440SRuss Cox dip->major = ip->major; 211f9a06440SRuss Cox dip->minor = ip->minor; 212f9a06440SRuss Cox dip->nlink = ip->nlink; 213f9a06440SRuss Cox dip->size = ip->size; 214f9a06440SRuss Cox memmove(dip->addrs, ip->addrs, sizeof(ip->addrs)); 21513a96baeSFrans Kaashoek log_write(bp); 216f9a06440SRuss Cox brelse(bp); 217f9a06440SRuss Cox } 218f9a06440SRuss Cox 219f5527388Srsc // Find the inode with number inum on device dev 22038eee5bcSRobert Morris // and return the in-memory copy. Does not lock 22138eee5bcSRobert Morris // the inode and does not read it from disk. 22207090dd7Srsc static struct inode* 22311a9947fSrtm iget(uint dev, uint inum) 22411a9947fSrtm { 225bcca6c6bSrsc struct inode *ip, *empty; 22611a9947fSrtm 227bcca6c6bSrsc acquire(&icache.lock); 22811a9947fSrtm 22938eee5bcSRobert Morris // Is the inode already cached? 230bcca6c6bSrsc empty = 0; 231bcca6c6bSrsc for(ip = &icache.inode[0]; ip < &icache.inode[NINODE]; ip++){ 2320d6bbd31Srsc if(ip->ref > 0 && ip->dev == dev && ip->inum == inum){ 2330d6bbd31Srsc ip->ref++; 234bcca6c6bSrsc release(&icache.lock); 23507090dd7Srsc return ip; 23611a9947fSrtm } 237bcca6c6bSrsc if(empty == 0 && ip->ref == 0) // Remember empty slot. 238bcca6c6bSrsc empty = ip; 23911a9947fSrtm } 24011a9947fSrtm 24138eee5bcSRobert Morris // Recycle an inode cache entry. 242bcca6c6bSrsc if(empty == 0) 24332eea766Srsc panic("iget: no inodes"); 24411a9947fSrtm 245bcca6c6bSrsc ip = empty; 246bcca6c6bSrsc ip->dev = dev; 247bcca6c6bSrsc ip->inum = inum; 248bcca6c6bSrsc ip->ref = 1; 249f32f3638Srsc ip->flags = 0; 250bcca6c6bSrsc release(&icache.lock); 25111a9947fSrtm 25207090dd7Srsc return ip; 253f32f3638Srsc } 254f32f3638Srsc 255eaea18cbSrsc // Increment reference count for ip. 256eaea18cbSrsc // Returns ip to enable ip = idup(ip1) idiom. 25707090dd7Srsc struct inode* 25807090dd7Srsc idup(struct inode *ip) 259f32f3638Srsc { 260eaea18cbSrsc acquire(&icache.lock); 261eaea18cbSrsc ip->ref++; 262eaea18cbSrsc release(&icache.lock); 26307090dd7Srsc return ip; 264f32f3638Srsc } 265f32f3638Srsc 2661ddfbbb1SFrans Kaashoek // Lock the given inode. 26738eee5bcSRobert Morris // Reads the inode from disk if necessary. 26807090dd7Srsc void 26907090dd7Srsc ilock(struct inode *ip) 270f32f3638Srsc { 271f32f3638Srsc struct buf *bp; 272f32f3638Srsc struct dinode *dip; 273eaea18cbSrsc 27407090dd7Srsc if(ip == 0 || ip->ref < 1) 27507090dd7Srsc panic("ilock"); 276f32f3638Srsc 277f32f3638Srsc acquire(&icache.lock); 2781ddfbbb1SFrans Kaashoek while(ip->flags & I_BUSY) 2791ddfbbb1SFrans Kaashoek sleep(ip, &icache.lock); 2801ddfbbb1SFrans Kaashoek ip->flags |= I_BUSY; 281f32f3638Srsc release(&icache.lock); 282f32f3638Srsc 283f32f3638Srsc if(!(ip->flags & I_VALID)){ 284f32f3638Srsc bp = bread(ip->dev, IBLOCK(ip->inum)); 2853341e30fSrsc dip = (struct dinode*)bp->data + ip->inum%IPB; 286bcca6c6bSrsc ip->type = dip->type; 287bcca6c6bSrsc ip->major = dip->major; 288bcca6c6bSrsc ip->minor = dip->minor; 289bcca6c6bSrsc ip->nlink = dip->nlink; 290bcca6c6bSrsc ip->size = dip->size; 291bcca6c6bSrsc memmove(ip->addrs, dip->addrs, sizeof(ip->addrs)); 29211a9947fSrtm brelse(bp); 293f32f3638Srsc ip->flags |= I_VALID; 294eaea18cbSrsc if(ip->type == 0) 295eaea18cbSrsc panic("ilock: no type"); 29611a9947fSrtm } 297bcca6c6bSrsc } 298bcca6c6bSrsc 299bcca6c6bSrsc // Unlock the given inode. 30007090dd7Srsc void 301bcca6c6bSrsc iunlock(struct inode *ip) 302bcca6c6bSrsc { 3031ddfbbb1SFrans Kaashoek if(ip == 0 || !(ip->flags & I_BUSY) || ip->ref < 1) 304bcca6c6bSrsc panic("iunlock"); 305bcca6c6bSrsc 306bcca6c6bSrsc acquire(&icache.lock); 3071ddfbbb1SFrans Kaashoek ip->flags &= ~I_BUSY; 3081ddfbbb1SFrans Kaashoek wakeup(ip); 309bcca6c6bSrsc release(&icache.lock); 310bcca6c6bSrsc } 311bcca6c6bSrsc 31238eee5bcSRobert Morris // Drop a reference to an in-memory inode. 31338eee5bcSRobert Morris // If that was the last reference, the inode cache entry can 31438eee5bcSRobert Morris // be recycled. 31538eee5bcSRobert Morris // If that was the last reference and the inode has no links 31638eee5bcSRobert Morris // to it, free the inode (and its content) on disk. 3172c565472SRobert Morris // All calls to iput() must be inside a transaction in 3182c565472SRobert Morris // case it has to free the inode. 319bcca6c6bSrsc void 32007090dd7Srsc iput(struct inode *ip) 321bcca6c6bSrsc { 322f32f3638Srsc acquire(&icache.lock); 323f32f3638Srsc if(ip->ref == 1 && (ip->flags & I_VALID) && ip->nlink == 0){ 324e2b4583dSRobert Morris // inode has no links and no other references: truncate and free. 3251ddfbbb1SFrans Kaashoek if(ip->flags & I_BUSY) 326eaea18cbSrsc panic("iput busy"); 3271ddfbbb1SFrans Kaashoek ip->flags |= I_BUSY; 328f32f3638Srsc release(&icache.lock); 329f32f3638Srsc itrunc(ip); 330f32f3638Srsc ip->type = 0; 331f32f3638Srsc iupdate(ip); 332f32f3638Srsc acquire(&icache.lock); 333ce72cadbSrsc ip->flags = 0; 3348970df0cSrsc wakeup(ip); 335f32f3638Srsc } 336f32f3638Srsc ip->ref--; 337f32f3638Srsc release(&icache.lock); 338bcca6c6bSrsc } 339bcca6c6bSrsc 3407895178dSrsc // Common idiom: unlock, then put. 34107090dd7Srsc void 34207090dd7Srsc iunlockput(struct inode *ip) 34307090dd7Srsc { 34407090dd7Srsc iunlock(ip); 34507090dd7Srsc iput(ip); 34607090dd7Srsc } 34707090dd7Srsc 3488d2e9a48Srsc //PAGEBREAK! 34938eee5bcSRobert Morris // Inode content 350bcca6c6bSrsc // 35138eee5bcSRobert Morris // The content (data) associated with each inode is stored 35238eee5bcSRobert Morris // in blocks on the disk. The first NDIRECT block numbers 3537895178dSrsc // are listed in ip->addrs[]. The next NINDIRECT blocks are 35438eee5bcSRobert Morris // listed in block ip->addrs[NDIRECT]. 3559d3fb671Srtm 356bb207a1dSrsc // Return the disk block address of the nth block in inode ip. 35713ae8808Srsc // If there is no such block, bmap allocates one. 358eaea18cbSrsc static uint 35913ae8808Srsc bmap(struct inode *ip, uint bn) 36022bac2cbSkaashoek { 361bcca6c6bSrsc uint addr, *a; 362bcca6c6bSrsc struct buf *bp; 36322bac2cbSkaashoek 364ea2909b6Skaashoek if(bn < NDIRECT){ 36513ae8808Srsc if((addr = ip->addrs[bn]) == 0) 366bcca6c6bSrsc ip->addrs[bn] = addr = balloc(ip->dev); 367bcca6c6bSrsc return addr; 368bcca6c6bSrsc } 369bcca6c6bSrsc bn -= NDIRECT; 370bcca6c6bSrsc 371bcca6c6bSrsc if(bn < NINDIRECT){ 372bcca6c6bSrsc // Load indirect block, allocating if necessary. 37313ae8808Srsc if((addr = ip->addrs[NDIRECT]) == 0) 374ba6cd8a6Srsc ip->addrs[NDIRECT] = addr = balloc(ip->dev); 375bcca6c6bSrsc bp = bread(ip->dev, addr); 376bcca6c6bSrsc a = (uint*)bp->data; 377bcca6c6bSrsc if((addr = a[bn]) == 0){ 378bcca6c6bSrsc a[bn] = addr = balloc(ip->dev); 37913a96baeSFrans Kaashoek log_write(bp); 380bcca6c6bSrsc } 381bcca6c6bSrsc brelse(bp); 382bcca6c6bSrsc return addr; 38322bac2cbSkaashoek } 38422bac2cbSkaashoek 385bcca6c6bSrsc panic("bmap: out of range"); 386bcca6c6bSrsc } 387bcca6c6bSrsc 388bcca6c6bSrsc // Truncate inode (discard contents). 38938eee5bcSRobert Morris // Only called when the inode has no links 39038eee5bcSRobert Morris // to it (no directory entries referring to it) 39138eee5bcSRobert Morris // and has no in-memory reference to it (is 39238eee5bcSRobert Morris // not an open file or current directory). 393fbf91039Srsc static void 3942aa4c3bcSrtm itrunc(struct inode *ip) 39522bac2cbSkaashoek { 396ea2909b6Skaashoek int i, j; 397bcca6c6bSrsc struct buf *bp; 3987d4aef6cSrsc uint *a; 39922bac2cbSkaashoek 400bcca6c6bSrsc for(i = 0; i < NDIRECT; i++){ 401bcca6c6bSrsc if(ip->addrs[i]){ 40222bac2cbSkaashoek bfree(ip->dev, ip->addrs[i]); 40322bac2cbSkaashoek ip->addrs[i] = 0; 40422bac2cbSkaashoek } 40522bac2cbSkaashoek } 406bcca6c6bSrsc 407ba6cd8a6Srsc if(ip->addrs[NDIRECT]){ 408ba6cd8a6Srsc bp = bread(ip->dev, ip->addrs[NDIRECT]); 409bcca6c6bSrsc a = (uint*)bp->data; 410bcca6c6bSrsc for(j = 0; j < NINDIRECT; j++){ 411bcca6c6bSrsc if(a[j]) 412bcca6c6bSrsc bfree(ip->dev, a[j]); 413bcca6c6bSrsc } 414bcca6c6bSrsc brelse(bp); 415ba6cd8a6Srsc bfree(ip->dev, ip->addrs[NDIRECT]); 416ba6cd8a6Srsc ip->addrs[NDIRECT] = 0; 417bcca6c6bSrsc } 418bcca6c6bSrsc 41922bac2cbSkaashoek ip->size = 0; 42022bac2cbSkaashoek iupdate(ip); 42122bac2cbSkaashoek } 42222bac2cbSkaashoek 423bb207a1dSrsc // Copy stat information from inode. 424e958c538Skaashoek void 4251f544842Skaashoek stati(struct inode *ip, struct stat *st) 4261f544842Skaashoek { 4271dca3afbSrsc st->dev = ip->dev; 4281dca3afbSrsc st->ino = ip->inum; 4291dca3afbSrsc st->type = ip->type; 4301dca3afbSrsc st->nlink = ip->nlink; 4311dca3afbSrsc st->size = ip->size; 4321f544842Skaashoek } 4331f544842Skaashoek 434eaea18cbSrsc //PAGEBREAK! 435bb207a1dSrsc // Read data from inode. 436c59361f1Srtm int 43717a85657Srtm readi(struct inode *ip, char *dst, uint off, uint n) 438c59361f1Srtm { 439bcca6c6bSrsc uint tot, m; 440c59361f1Srtm struct buf *bp; 441c59361f1Srtm 442939f9edeSkaashoek if(ip->type == T_DEV){ 4431dca3afbSrsc if(ip->major < 0 || ip->major >= NDEV || !devsw[ip->major].read) 444939f9edeSkaashoek return -1; 445d844f0f9Srsc return devsw[ip->major].read(ip, dst, n); 446939f9edeSkaashoek } 447939f9edeSkaashoek 4487895178dSrsc if(off > ip->size || off + n < off) 449bcca6c6bSrsc return -1; 450bcca6c6bSrsc if(off + n > ip->size) 451bcca6c6bSrsc n = ip->size - off; 452bcca6c6bSrsc 453bcca6c6bSrsc for(tot=0; tot<n; tot+=m, off+=m, dst+=m){ 45413ae8808Srsc bp = bread(ip->dev, bmap(ip, off/BSIZE)); 455bcca6c6bSrsc m = min(n - tot, BSIZE - off%BSIZE); 456bcca6c6bSrsc memmove(dst, bp->data + off%BSIZE, m); 457c59361f1Srtm brelse(bp); 458c59361f1Srtm } 459bcca6c6bSrsc return n; 460ea2909b6Skaashoek } 461ea2909b6Skaashoek 462eaea18cbSrsc // PAGEBREAK! 463bb207a1dSrsc // Write data to inode. 464ea2909b6Skaashoek int 465bcca6c6bSrsc writei(struct inode *ip, char *src, uint off, uint n) 4666fa5ffb5Skaashoek { 467bcca6c6bSrsc uint tot, m; 4687d4aef6cSrsc struct buf *bp; 4697d4aef6cSrsc 4706fa5ffb5Skaashoek if(ip->type == T_DEV){ 4711dca3afbSrsc if(ip->major < 0 || ip->major >= NDEV || !devsw[ip->major].write) 472939f9edeSkaashoek return -1; 473d844f0f9Srsc return devsw[ip->major].write(ip, src, n); 4747d4aef6cSrsc } 4757d4aef6cSrsc 4761ddfbbb1SFrans Kaashoek if(off > ip->size || off + n < off) 477bcca6c6bSrsc return -1; 4781ddfbbb1SFrans Kaashoek if(off + n > MAXFILE*BSIZE) 4792e590463SRobert Morris return -1; 480bcca6c6bSrsc 481bcca6c6bSrsc for(tot=0; tot<n; tot+=m, off+=m, src+=m){ 48213ae8808Srsc bp = bread(ip->dev, bmap(ip, off/BSIZE)); 483bcca6c6bSrsc m = min(n - tot, BSIZE - off%BSIZE); 484bcca6c6bSrsc memmove(bp->data + off%BSIZE, src, m); 4852e590463SRobert Morris log_write(bp); 48628d9ef04Skaashoek brelse(bp); 48728d9ef04Skaashoek } 488bcca6c6bSrsc 489bcca6c6bSrsc if(n > 0 && off > ip->size){ 49048b82470Srsc ip->size = off; 49128d9ef04Skaashoek iupdate(ip); 49228d9ef04Skaashoek } 493bcca6c6bSrsc return n; 4946fa5ffb5Skaashoek } 4956fa5ffb5Skaashoek 496eaea18cbSrsc //PAGEBREAK! 497bcca6c6bSrsc // Directories 498bcca6c6bSrsc 499eaea18cbSrsc int 500fbf91039Srsc namecmp(const char *s, const char *t) 501fbf91039Srsc { 502766ba5ccSrsc return strncmp(s, t, DIRSIZ); 503fbf91039Srsc } 504fbf91039Srsc 505bcca6c6bSrsc // Look for a directory entry in a directory. 506eaea18cbSrsc // If found, set *poff to byte offset of entry. 50707090dd7Srsc struct inode* 508fbf91039Srsc dirlookup(struct inode *dp, char *name, uint *poff) 509bcca6c6bSrsc { 510f32f3638Srsc uint off, inum; 511327cc21fSRobert Morris struct dirent de; 512bcca6c6bSrsc 513bcca6c6bSrsc if(dp->type != T_DIR) 51420365348Srtm panic("dirlookup not DIR"); 515bcca6c6bSrsc 516327cc21fSRobert Morris for(off = 0; off < dp->size; off += sizeof(de)){ 517327cc21fSRobert Morris if(readi(dp, (char*)&de, off, sizeof(de)) != sizeof(de)) 518327cc21fSRobert Morris panic("dirlink read"); 519327cc21fSRobert Morris if(de.inum == 0) 520bcca6c6bSrsc continue; 521327cc21fSRobert Morris if(namecmp(name, de.name) == 0){ 522bcca6c6bSrsc // entry matches path element 523e2a620daSrsc if(poff) 524327cc21fSRobert Morris *poff = off; 525327cc21fSRobert Morris inum = de.inum; 526f32f3638Srsc return iget(dp->dev, inum); 527f32f3638Srsc } 528f32f3638Srsc } 529327cc21fSRobert Morris 530bcca6c6bSrsc return 0; 531bcca6c6bSrsc } 532bcca6c6bSrsc 53313ae8808Srsc // Write a new directory entry (name, inum) into the directory dp. 534eaea18cbSrsc int 53513ae8808Srsc dirlink(struct inode *dp, char *name, uint inum) 536bcca6c6bSrsc { 537e2a620daSrsc int off; 538bcca6c6bSrsc struct dirent de; 53907090dd7Srsc struct inode *ip; 540f32f3638Srsc 541eaea18cbSrsc // Check that name is not present. 54207090dd7Srsc if((ip = dirlookup(dp, name, 0)) != 0){ 54307090dd7Srsc iput(ip); 544f32f3638Srsc return -1; 545f32f3638Srsc } 546bcca6c6bSrsc 547bcca6c6bSrsc // Look for an empty dirent. 548bcca6c6bSrsc for(off = 0; off < dp->size; off += sizeof(de)){ 549bcca6c6bSrsc if(readi(dp, (char*)&de, off, sizeof(de)) != sizeof(de)) 5507895178dSrsc panic("dirlink read"); 551bcca6c6bSrsc if(de.inum == 0) 552bcca6c6bSrsc break; 553bcca6c6bSrsc } 554bcca6c6bSrsc 555766ba5ccSrsc strncpy(de.name, name, DIRSIZ); 55613ae8808Srsc de.inum = inum; 557bcca6c6bSrsc if(writei(dp, (char*)&de, off, sizeof(de)) != sizeof(de)) 5587895178dSrsc panic("dirlink"); 559f32f3638Srsc 560f32f3638Srsc return 0; 561bcca6c6bSrsc } 562bcca6c6bSrsc 5638d2e9a48Srsc //PAGEBREAK! 564bcca6c6bSrsc // Paths 565bcca6c6bSrsc 566eaea18cbSrsc // Copy the next path element from path into name. 567eaea18cbSrsc // Return a pointer to the element following the copied one. 568eaea18cbSrsc // The returned path has no leading slashes, 569eaea18cbSrsc // so the caller can check *path=='\0' to see if the name is the last one. 570eaea18cbSrsc // If no name to remove, return 0. 571ab5c2dbbSrsc // 572ab5c2dbbSrsc // Examples: 573eaea18cbSrsc // skipelem("a/bb/c", name) = "bb/c", setting name = "a" 5747895178dSrsc // skipelem("///a//bb", name) = "bb", setting name = "a" 57513ae8808Srsc // skipelem("a", name) = "", setting name = "a" 576eaea18cbSrsc // skipelem("", name) = skipelem("////", name) = 0 577ab5c2dbbSrsc // 578ab5c2dbbSrsc static char* 579fbf91039Srsc skipelem(char *path, char *name) 580ab5c2dbbSrsc { 581fbf91039Srsc char *s; 582fbf91039Srsc int len; 583fbf91039Srsc 584ab5c2dbbSrsc while(*path == '/') 585ab5c2dbbSrsc path++; 586ab5c2dbbSrsc if(*path == 0) 587ab5c2dbbSrsc return 0; 588fbf91039Srsc s = path; 589ab5c2dbbSrsc while(*path != '/' && *path != 0) 590ab5c2dbbSrsc path++; 591fbf91039Srsc len = path - s; 592fbf91039Srsc if(len >= DIRSIZ) 593fbf91039Srsc memmove(name, s, DIRSIZ); 594fbf91039Srsc else { 595fbf91039Srsc memmove(name, s, len); 596fbf91039Srsc name[len] = 0; 597fbf91039Srsc } 598ab5c2dbbSrsc while(*path == '/') 599ab5c2dbbSrsc path++; 600ab5c2dbbSrsc return path; 601ab5c2dbbSrsc } 602ab5c2dbbSrsc 603eaea18cbSrsc // Look up and return the inode for a path name. 604bf2932a6Srsc // If parent != 0, return the inode for the parent and copy the final 605bf2932a6Srsc // path element into name, which must have room for DIRSIZ bytes. 6062c565472SRobert Morris // Must be called inside a transaction since it calls iput(). 60707090dd7Srsc static struct inode* 608f9a06440SRuss Cox namex(char *path, int nameiparent, char *name) 6099d3fb671Srtm { 61007090dd7Srsc struct inode *ip, *next; 6119d3fb671Srtm 612ab5c2dbbSrsc if(*path == '/') 6132ce40d70Srtm ip = iget(ROOTDEV, ROOTINO); 614f32f3638Srsc else 61548755214SRuss Cox ip = idup(proc->cwd); 6169d3fb671Srtm 617fbf91039Srsc while((path = skipelem(path, name)) != 0){ 61807090dd7Srsc ilock(ip); 61907090dd7Srsc if(ip->type != T_DIR){ 62007090dd7Srsc iunlockput(ip); 621eaea18cbSrsc return 0; 622eaea18cbSrsc } 623f9a06440SRuss Cox if(nameiparent && *path == '\0'){ 624e2a620daSrsc // Stop one level early. 62507090dd7Srsc iunlock(ip); 62607090dd7Srsc return ip; 627ab5c2dbbSrsc } 6287895178dSrsc if((next = dirlookup(ip, name, 0)) == 0){ 62907090dd7Srsc iunlockput(ip); 630eaea18cbSrsc return 0; 631eaea18cbSrsc } 63207090dd7Srsc iunlockput(ip); 63307090dd7Srsc ip = next; 634ab5c2dbbSrsc } 635f9a06440SRuss Cox if(nameiparent){ 63607090dd7Srsc iput(ip); 6375051da6dSrtm return 0; 63820365348Srtm } 63907090dd7Srsc return ip; 6400633b971Skaashoek } 6419d3fb671Srtm 6427895178dSrsc struct inode* 6437895178dSrsc namei(char *path) 6447895178dSrsc { 6457895178dSrsc char name[DIRSIZ]; 64613ae8808Srsc return namex(path, 0, name); 6477895178dSrsc } 648bf2932a6Srsc 6497895178dSrsc struct inode* 6507895178dSrsc nameiparent(char *path, char *name) 6517895178dSrsc { 65213ae8808Srsc return namex(path, 1, name); 6537895178dSrsc } 654