xv6-cs450/fs.c

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#include "types.h"
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#include "stat.h"
#include "param.h"
#include "x86.h"
#include "mmu.h"
#include "proc.h"
#include "defs.h"
#include "spinlock.h"
#include "buf.h"
#include "fs.h"
#include "fsvar.h"
#include "dev.h"
// these are inodes currently in use
// an entry is free if count == 0
struct inode inode[NINODE];
struct spinlock inode_table_lock;
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uint rootdev = 1;
void
iinit(void)
{
initlock(&inode_table_lock, "inode_table");
}
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static uint
balloc(uint dev)
{
int b;
struct buf *bp;
struct superblock *sb;
int bi = 0;
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int size;
int ninodes;
uchar m;
bp = bread(dev, 1);
sb = (struct superblock *) bp->data;
size = sb->size;
ninodes = sb->ninodes;
for (b = 0; b < size; b++) {
if (b % BPB == 0) {
brelse(bp);
bp = bread(dev, BBLOCK(b, ninodes));
}
bi = b % BPB;
m = 0x1 << (bi % 8);
if ((bp->data[bi/8] & m) == 0) { // is block free?
break;
}
}
if (b >= size)
panic("balloc: out of blocks\n");
bp->data[bi/8] |= 0x1 << (bi % 8);
bwrite (bp, BBLOCK(b, ninodes)); // mark it allocated on disk
brelse(bp);
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return b;
}
static void
bfree(int dev, uint b)
{
struct buf *bp;
struct superblock *sb;
int bi;
int ninodes;
uchar m;
bp = bread(dev, 1);
sb = (struct superblock *) bp->data;
ninodes = sb->ninodes;
brelse(bp);
bp = bread(dev, b);
memset(bp->data, 0, BSIZE);
bwrite(bp, b);
brelse(bp);
bp = bread(dev, BBLOCK(b, ninodes));
bi = b % BPB;
m = ~(0x1 << (bi %8));
bp->data[bi/8] &= m;
bwrite (bp, BBLOCK(b, ninodes)); // mark it free on disk
brelse(bp);
}
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// returns an inode with busy set and incremented reference count.
struct inode *
iget(uint dev, uint inum)
{
struct inode *ip, *nip;
struct dinode *dip;
struct buf *bp;
acquire(&inode_table_lock);
loop:
nip = 0;
for(ip = &inode[0]; ip < &inode[NINODE]; ip++){
if(ip->count > 0 && ip->dev == dev && ip->inum == inum){
if(ip->busy){
sleep(ip, &inode_table_lock);
goto loop;
}
ip->count++;
ip->busy = 1;
release(&inode_table_lock);
return ip;
}
if(nip == 0 && ip->count == 0)
nip = ip;
}
if(nip == 0)
panic("out of inodes");
nip->dev = dev;
nip->inum = inum;
nip->count = 1;
nip->busy = 1;
release(&inode_table_lock);
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bp = bread(dev, IBLOCK(inum));
dip = &((struct dinode *)(bp->data))[inum % IPB];
nip->type = dip->type;
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nip->major = dip->major;
nip->minor = dip->minor;
nip->nlink = dip->nlink;
nip->size = dip->size;
memmove(nip->addrs, dip->addrs, sizeof(nip->addrs));
brelse(bp);
return nip;
}
void
iupdate (struct inode *ip)
{
struct buf *bp;
struct dinode *dip;
bp = bread(ip->dev, IBLOCK(ip->inum));
dip = &((struct dinode *)(bp->data))[ip->inum % IPB];
dip->type = ip->type;
dip->major = ip->major;
dip->minor = ip->minor;
dip->nlink = ip->nlink;
dip->size = ip->size;
memmove(dip->addrs, ip->addrs, sizeof(ip->addrs));
bwrite (bp, IBLOCK(ip->inum)); // mark it allocated on the disk
brelse(bp);
}
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struct inode *
ialloc(uint dev, short type)
{
struct inode *ip;
struct dinode *dip = 0;
struct superblock *sb;
int ninodes;
int inum;
struct buf *bp;
bp = bread(dev, 1);
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sb = (struct superblock *) bp->data;
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ninodes = sb->ninodes;
brelse(bp);
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for (inum = 1; inum < ninodes; inum++) { // loop over inode blocks
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bp = bread(dev, IBLOCK(inum));
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dip = &((struct dinode *)(bp->data))[inum % IPB];
if (dip->type == 0) { // a free inode
break;
}
brelse(bp);
}
if (inum >= ninodes)
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panic ("ialloc: no inodes left\n");
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dip->type = type;
bwrite (bp, IBLOCK(inum)); // mark it allocated on the disk
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brelse(bp);
ip = iget (dev, inum);
return ip;
}
static void
ifree(struct inode *ip)
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{
ip->type = 0;
iupdate(ip);
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}
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void
ilock(struct inode *ip)
{
if(ip->count < 1)
panic("ilock");
acquire(&inode_table_lock);
while(ip->busy)
sleep(ip, &inode_table_lock);
ip->busy = 1;
release(&inode_table_lock);
}
// caller is holding onto a reference to this inode, but no
// longer needs to examine or change it, so clear ip->busy.
void
iunlock(struct inode *ip)
{
if(ip->busy != 1 || ip->count < 1)
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panic("iunlock");
acquire(&inode_table_lock);
ip->busy = 0;
wakeup(ip);
release(&inode_table_lock);
}
uint
bmap(struct inode *ip, uint bn)
{
unsigned x;
if(bn >= NDIRECT)
panic("bmap 1");
x = ip->addrs[bn];
if(x == 0)
panic("bmap 2");
return x;
}
void
iunlink(struct inode *ip)
{
int i;
// free inode, its blocks, and remove dir entry
for (i = 0; i < NDIRECT; i++) {
if (ip->addrs[i] != 0) {
bfree(ip->dev, ip->addrs[i]);
ip->addrs[i] = 0;
}
}
ip->size = 0;
ip->major = 0;
ip->minor = 0;
iupdate(ip);
ifree(ip); // is this the right order?
}
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// caller is releasing a reference to this inode.
// you must have the inode lock.
void
iput(struct inode *ip)
{
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if(ip->count < 1 || ip->busy != 1)
panic("iput");
if ((ip->count == 1) && (ip->nlink == 0))
iunlink(ip);
acquire(&inode_table_lock);
ip->count -= 1;
ip->busy = 0;
wakeup(ip);
release(&inode_table_lock);
}
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void
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idecref(struct inode *ip)
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{
ilock(ip);
iput(ip);
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}
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void
iincref(struct inode *ip)
{
ilock(ip);
ip->count++;
iunlock(ip);
}
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void
stati(struct inode *ip, struct stat *st)
{
st->st_dev = ip->dev;
st->st_ino = ip->inum;
st->st_type = ip->type;
st->st_nlink = ip->nlink;
st->st_size = ip->size;
}
#define min(a, b) ((a) < (b) ? (a) : (b))
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int
readi(struct inode *ip, char *dst, uint off, uint n)
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{
uint target = n, n1;
struct buf *bp;
if (ip->type == T_DEV) {
if (ip->major < 0 || ip->major >= NDEV || !devsw[ip->major].d_read)
return -1;
return devsw[ip->major].d_read (ip->minor, dst, n);
}
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while(n > 0 && off < ip->size){
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bp = bread(ip->dev, bmap(ip, off / BSIZE));
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n1 = min(n, ip->size - off);
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n1 = min(n1, BSIZE - (off % BSIZE));
memmove(dst, bp->data + (off % BSIZE), n1);
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n -= n1;
off += n1;
dst += n1;
brelse(bp);
}
return target - n;
}
int
writei(struct inode *ip, char *addr, uint off, uint n)
{
if (ip->type == T_DEV) {
if (ip->major < 0 || ip->major >= NDEV || !devsw[ip->major].d_write)
return -1;
return devsw[ip->major].d_write (ip->minor, addr, n);
} else if (ip->type == T_FILE || ip->type == T_DIR) { // XXX dir here too?
struct buf *bp;
int r = 0;
int m;
int lbn;
uint b;
while (r < n) {
lbn = off / BSIZE;
if (lbn >= NDIRECT) return r;
if (ip->addrs[lbn] == 0) {
b = balloc(ip->dev);
if (b <= 0) return r;
ip->addrs[lbn] = b;
}
m = min(BSIZE - off % BSIZE, n-r);
bp = bread(ip->dev, bmap(ip, off / BSIZE));
memmove (bp->data + off % BSIZE, addr, m);
bwrite (bp, bmap(ip, off/BSIZE));
brelse (bp);
r += m;
off += m;
}
if (r > 0) {
if (off > ip->size) {
if (ip->type == T_DIR) ip->size = ((off / BSIZE) + 1) * BSIZE;
else ip->size = off;
}
iupdate(ip);
}
return r;
} else {
panic ("writei: unknown type\n");
return 0;
}
}
// look up a path name, in one of three modes.
// NAMEI_LOOKUP: return locked target inode.
// NAMEI_CREATE: return locked parent inode.
// but return 0 if name does exist.
// NAMEI_DELETE: return locked parent inode, offset of dirent in *ret_off.
// return 0 if name doesn't exist.
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struct inode *
namei(char *path, int mode, uint *ret_off)
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{
struct inode *dp;
struct proc *p = curproc[cpu()];
char *cp = path, *cp1;
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uint off, dev;
struct buf *bp;
struct dirent *ep;
int i, atend;
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unsigned ninum;
if (*cp == '/') dp = iget(rootdev, 1);
else {
dp = p->cwd;
iincref(dp);
ilock(dp);
}
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while(*cp == '/')
cp++;
while(1){
if(*cp == '\0'){
if(mode == NAMEI_LOOKUP)
return dp;
iput(dp);
return 0;
}
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if(dp->type != T_DIR){
iput(dp);
return 0;
}
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for(off = 0; off < dp->size; off += BSIZE){
bp = bread(dp->dev, bmap(dp, off / BSIZE));
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for(ep = (struct dirent *) bp->data;
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ep < (struct dirent *) (bp->data + BSIZE);
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ep++){
if(ep->inum == 0)
continue;
for(i = 0; i < DIRSIZ && cp[i] != '/' && cp[i]; i++)
if(cp[i] != ep->name[i])
break;
if((cp[i] == '\0' || cp[i] == '/') && (i >= DIRSIZ || ep->name[i] == '\0')){
off += (uchar*)ep - bp->data;
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ninum = ep->inum;
brelse(bp);
cp += i;
goto found;
}
}
brelse(bp);
}
atend = 1;
for(cp1 = cp; *cp1; cp1++)
if(*cp1 == '/')
atend = 0;
if(mode == NAMEI_CREATE && atend)
return dp;
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iput(dp);
return 0;
found:
if(mode == NAMEI_DELETE && *cp == '\0'){
*ret_off = off;
return dp;
}
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dev = dp->dev;
iput(dp);
dp = iget(dev, ninum);
if(dp->type == 0 || dp->nlink < 1)
panic("namei");
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while(*cp == '/')
cp++;
}
}
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void
wdir(struct inode *dp, char *name, uint ino)
{
uint off;
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struct dirent de;
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int i;
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for(off = 0; off < dp->size; off += sizeof(de)){
if(readi(dp, (char *) &de, off, sizeof(de)) != sizeof(de))
panic("wdir read");
if(de.inum == 0)
break;
}
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de.inum = ino;
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for(i = 0; i < DIRSIZ && name[i]; i++)
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de.name[i] = name[i];
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for( ; i < DIRSIZ; i++)
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de.name[i] = '\0';
if(writei(dp, (char *) &de, off, sizeof(de)) != sizeof(de))
panic("wdir write");
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}
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struct inode *
mknod(char *cp, short type, short major, short minor)
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{
struct inode *ip, *dp;
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if ((dp = namei(cp, NAMEI_CREATE, 0)) == 0)
return 0;
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ip = ialloc(dp->dev, type);
if (ip == 0) {
iput(dp);
return 0;
}
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ip->major = major;
ip->minor = minor;
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ip->size = 0;
ip->nlink = 1;
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iupdate (ip); // write new inode to disk
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wdir(dp, cp, ip->inum);
iput(dp);
return ip;
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}
int
unlink(char *cp)
{
struct inode *ip, *dp;
struct dirent de;
uint off, inum, dev;
if ((dp = namei(cp, NAMEI_DELETE, &off)) == 0)
return -1;
dev = dp->dev;
if(readi(dp, (char*)&de, off, sizeof(de)) != sizeof(de) || de.inum == 0)
panic("unlink no entry");
inum = de.inum;
memset(&de, 0, sizeof(de));
if(writei(dp, (char*)&de, off, sizeof(de)) != sizeof(de))
panic("unlink dir write");
iupdate(dp);
iput(dp);
ip = iget(dev, inum);
ip->nlink--;
iupdate(ip);
iput(ip);
return 0;
}
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int
link(char *name1, char *name2)
{
struct inode *ip, *dp;
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if ((ip = namei(name1, NAMEI_LOOKUP, 0)) == 0)
return -1;
if(ip->type == T_DIR){
iput(ip);
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return -1;
}
iunlock(ip);
if ((dp = namei(name2, NAMEI_CREATE, 0)) == 0) {
idecref(ip);
return -1;
}
if(dp->dev != ip->dev){
idecref(ip);
iput(dp);
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return -1;
}
ilock(ip);
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ip->nlink += 1;
iupdate (ip);
wdir(dp, name2, ip->inum);
iput(dp);
iput(ip);
return 0;
}