alloc.c

著名的AT&T UNIX v6 源码

#include "../h/param.h"
#include "../h/systm.h"
#include "../h/mount.h"
#include "../h/filsys.h"
#include "../h/fblk.h"
#include "../h/conf.h"
#include "../h/buf.h"
#include "../h/inode.h"
#include "../h/ino.h"
#include "../h/dir.h"
#include "../h/user.h"
typedef	struct fblk *FBLKP;

/*
 * alloc will obtain the next available
 * free disk block from the free list of
 * the specified device.
 * The super block has up to NICFREE remembered
 * free blocks; the last of these is read to
 * obtain NICFREE more . . .
 *
 * no space on dev x/y -- when
 * the free list is exhausted.
 */
struct buf *
alloc(dev)
dev_t dev;
{
	daddr_t bno;
	register struct filsys *fp;
	register struct buf *bp;

	fp = getfs(dev);
	while(fp->s_flock)
		sleep((caddr_t)&fp->s_flock, PINOD);
	do {
		if(fp->s_nfree <= 0)
			goto nospace;
		if (fp->s_nfree > NICFREE) {
			prdev("Bad free count", dev);
			goto nospace;
		}
		bno = fp->s_free[--fp->s_nfree];
		if(bno == 0)
			goto nospace;
	} while (badblock(fp, bno, dev));
	if(fp->s_nfree <= 0) {
		fp->s_flock++;
		bp = bread(dev, bno);
		if ((bp->b_flags&B_ERROR) == 0) {
			fp->s_nfree = ((FBLKP)(bp->b_un.b_addr))->df_nfree;
			bcopy((caddr_t)((FBLKP)(bp->b_un.b_addr))->df_free,
			    (caddr_t)fp->s_free, sizeof(fp->s_free));
		}
		brelse(bp);
		fp->s_flock = 0;
		wakeup((caddr_t)&fp->s_flock);
		if (fp->s_nfree <=0)
			goto nospace;
	}
	bp = getblk(dev, bno);
	clrbuf(bp);
	fp->s_fmod = 1;
	return(bp);

nospace:
	fp->s_nfree = 0;
	prdev("no space", dev);
	u.u_error = ENOSPC;
	return(NULL);
}

/*
 * place the specified disk block
 * back on the free list of the
 * specified device.
 */
free(dev, bno)
dev_t dev;
daddr_t bno;
{
	register struct filsys *fp;
	register struct buf *bp;

	fp = getfs(dev);
	fp->s_fmod = 1;
	while(fp->s_flock)
		sleep((caddr_t)&fp->s_flock, PINOD);
	if (badblock(fp, bno, dev))
		return;
	if(fp->s_nfree <= 0) {
		fp->s_nfree = 1;
		fp->s_free[0] = 0;
	}
	if(fp->s_nfree >= NICFREE) {
		fp->s_flock++;
		bp = getblk(dev, bno);
		((FBLKP)(bp->b_un.b_addr))->df_nfree = fp->s_nfree;
		bcopy((caddr_t)fp->s_free,
			(caddr_t)((FBLKP)(bp->b_un.b_addr))->df_free,
			sizeof(fp->s_free));
		fp->s_nfree = 0;
		bwrite(bp);
		fp->s_flock = 0;
		wakeup((caddr_t)&fp->s_flock);
	}
	fp->s_free[fp->s_nfree++] = bno;
	fp->s_fmod = 1;
}

/*
 * Check that a block number is in the
 * range between the I list and the size
 * of the device.
 * This is used mainly to check that a
 * garbage file system has not been mounted.
 *
 * bad block on dev x/y -- not in range
 */
badblock(fp, bn, dev)
register struct filsys *fp;
daddr_t bn;
dev_t dev;
{

	if (bn < fp->s_isize || bn >= fp->s_fsize) {
		prdev("bad block", dev);
		return(1);
	}
	return(0);
}

/*
 * Allocate an unused I node
 * on the specified device.
 * Used with file creation.
 * The algorithm keeps up to
 * NICINOD spare I nodes in the
 * super block. When this runs out,
 * a linear search through the
 * I list is instituted to pick
 * up NICINOD more.
 */
struct inode *
ialloc(dev)
dev_t dev;
{
	register struct filsys *fp;
	register struct buf *bp;
	register struct inode *ip;
	int i;
	struct dinode *dp;
	ino_t ino;
	daddr_t adr;

	fp = getfs(dev);
	while(fp->s_ilock)
		sleep((caddr_t)&fp->s_ilock, PINOD);
loop:
	if(fp->s_ninode > 0) {
		ino = fp->s_inode[--fp->s_ninode];
		ip = iget(dev, ino);
		if(ip == NULL)
			return(NULL);
		if(ip->i_mode == 0) {
			for (i=0; i<NADDR; i++)
				ip->i_un.i_addr[i] = 0;
			fp->s_fmod = 1;
			return(ip);
		}
		/*
		 * Inode was allocated after all.
		 * Look some more.
		 */
		iput(ip);
		goto loop;
	}
	fp->s_ilock++;
	ino = 1;
	for(adr = SUPERB+1; adr < fp->s_isize; adr++) {
		bp = bread(dev, adr);
		if (bp->b_flags & B_ERROR) {
			brelse(bp);
			ino += INOPB;
			continue;
		}
		dp = bp->b_un.b_dino;
		for(i=0; i<INOPB; i++) {
			if(dp->di_mode != 0)
				goto cont;
			for(ip = &inode[0]; ip < &inode[NINODE]; ip++)
			if(dev==ip->i_dev && ino==ip->i_number)
				goto cont;
			fp->s_inode[fp->s_ninode++] = ino;
			if(fp->s_ninode >= NICINOD)
				break;
		cont:
			ino++;
			dp++;
		}
		brelse(bp);
		if(fp->s_ninode >= NICINOD)
			break;
	}
	fp->s_ilock = 0;
	wakeup((caddr_t)&fp->s_ilock);
	if(fp->s_ninode > 0)
		goto loop;
	prdev("Out of inodes", dev);
	u.u_error = ENOSPC;
	return(NULL);
}

/*
 * Free the specified I node
 * on the specified device.
 * The algorithm stores up
 * to NICINOD I nodes in the super
 * block and throws away any more.
 */
ifree(dev, ino)
dev_t dev;
ino_t ino;
{
	register struct filsys *fp;

	fp = getfs(dev);
	if(fp->s_ilock)
		return;
	if(fp->s_ninode >= NICINOD)
		return;
	fp->s_inode[fp->s_ninode++] = ino;
	fp->s_fmod = 1;
}

/*
 * getfs maps a device number into
 * a pointer to the incore super
 * block.
 * The algorithm is a linear
 * search through the mount table.
 * A consistency check of the
 * in core free-block and i-node
 * counts.
 *
 * bad count on dev x/y -- the count
 *	check failed. At this point, all
 *	the counts are zeroed which will
 *	almost certainly lead to "no space"
 *	diagnostic
 * panic: no fs -- the device is not mounted.
 *	this "cannot happen"
 */
struct filsys *
getfs(dev)
dev_t dev;
{
	register struct mount *mp;
	register struct filsys *fp;

	for(mp = &mount[0]; mp < &mount[NMOUNT]; mp++)
	if(mp->m_bufp != NULL && mp->m_dev == dev) {
		fp = mp->m_bufp->b_un.b_filsys;
		if(fp->s_nfree > NICFREE || fp->s_ninode > NICINOD) {
			prdev("bad count", dev);
			fp->s_nfree = 0;
			fp->s_ninode = 0;
		}
		return(fp);
	}
	panic("no fs");
	return(NULL);
}

/*
 * update is the internal name of
 * 'sync'. It goes through the disk
 * queues to initiate sandbagged IO;
 * goes through the I nodes to write
 * modified nodes; and it goes through
 * the mount table to initiate modified
 * super blocks.
 */
update()
{
	register struct inode *ip;
	register struct mount *mp;
	register struct buf *bp;
	struct filsys *fp;

	if(updlock)
		return;
	updlock++;
	for(mp = &mount[0]; mp < &mount[NMOUNT]; mp++)
		if(mp->m_bufp != NULL) {
			fp = mp->m_bufp->b_un.b_filsys;
			if(fp->s_fmod==0 || fp->s_ilock!=0 ||
			   fp->s_flock!=0 || fp->s_ronly!=0)
				continue;
			bp = getblk(mp->m_dev, SUPERB);
			if (bp->b_flags & B_ERROR)
				continue;
			fp->s_fmod = 0;
			fp->s_time = time;
			bcopy((caddr_t)fp, bp->b_un.b_addr, BSIZE);
			bwrite(bp);
		}
	for(ip = &inode[0]; ip < &inode[NINODE]; ip++)
		if((ip->i_flag&ILOCK)==0 && ip->i_count) {
			ip->i_flag |= ILOCK;
			ip->i_count++;
			iupdat(ip, &time, &time);
			iput(ip);
		}
	updlock = 0;
	bflush(NODEV);
}