xref: /csrg-svn/sys/ufs/ffs/ufs_disksubr.c (revision 34102)

/*
 * Copyright (c) 1982, 1986 Regents of the University of California.
 * All rights reserved.  The Berkeley software License Agreement
 * specifies the terms and conditions for redistribution.
 *
 *	@(#)ufs_disksubr.c	7.6 (Berkeley) 04/24/88
 */

#include "param.h"
#include "systm.h"
#include "buf.h"
#include "disklabel.h"

#include "dir.h"
#include "user.h"

/*
 * Seek sort for disks.  We depend on the driver
 * which calls us using b_resid as the current cylinder number.
 *
 * The argument dp structure holds a b_actf activity chain pointer
 * on which we keep two queues, sorted in ascending cylinder order.
 * The first queue holds those requests which are positioned after
 * the current cylinder (in the first request); the second holds
 * requests which came in after their cylinder number was passed.
 * Thus we implement a one way scan, retracting after reaching the
 * end of the drive to the first request on the second queue,
 * at which time it becomes the first queue.
 *
 * A one-way scan is natural because of the way UNIX read-ahead
 * blocks are allocated.
 */

#define	b_cylin	b_resid

disksort(dp, bp)
	register struct buf *dp, *bp;
{
	register struct buf *ap;

	/*
	 * If nothing on the activity queue, then
	 * we become the only thing.
	 */
	ap = dp->b_actf;
	if(ap == NULL) {
		dp->b_actf = bp;
		dp->b_actl = bp;
		bp->av_forw = NULL;
		return;
	}
	/*
	 * If we lie after the first (currently active)
	 * request, then we must locate the second request list
	 * and add ourselves to it.
	 */
	if (bp->b_cylin < ap->b_cylin) {
		while (ap->av_forw) {
			/*
			 * Check for an ``inversion'' in the
			 * normally ascending cylinder numbers,
			 * indicating the start of the second request list.
			 */
			if (ap->av_forw->b_cylin < ap->b_cylin) {
				/*
				 * Search the second request list
				 * for the first request at a larger
				 * cylinder number.  We go before that;
				 * if there is no such request, we go at end.
				 */
				do {
					if (bp->b_cylin < ap->av_forw->b_cylin)
						goto insert;
					if (bp->b_cylin == ap->av_forw->b_cylin &&
					    bp->b_blkno < ap->av_forw->b_blkno)
						goto insert;
					ap = ap->av_forw;
				} while (ap->av_forw);
				goto insert;		/* after last */
			}
			ap = ap->av_forw;
		}
		/*
		 * No inversions... we will go after the last, and
		 * be the first request in the second request list.
		 */
		goto insert;
	}
	/*
	 * Request is at/after the current request...
	 * sort in the first request list.
	 */
	while (ap->av_forw) {
		/*
		 * We want to go after the current request
		 * if there is an inversion after it (i.e. it is
		 * the end of the first request list), or if
		 * the next request is a larger cylinder than our request.
		 */
		if (ap->av_forw->b_cylin < ap->b_cylin ||
		    bp->b_cylin < ap->av_forw->b_cylin ||
		    (bp->b_cylin == ap->av_forw->b_cylin &&
		    bp->b_blkno < ap->av_forw->b_blkno))
			goto insert;
		ap = ap->av_forw;
	}
	/*
	 * Neither a second list nor a larger
	 * request... we go at the end of the first list,
	 * which is the same as the end of the whole schebang.
	 */
insert:
	bp->av_forw = ap->av_forw;
	ap->av_forw = bp;
	if (ap == dp->b_actl)
		dp->b_actl = bp;
}

/*
 * Attempt to read a disk label from a device
 * using the indicated stategy routine.
 * The label must be partly set up before this:
 * secpercyl and anything required in the strategy routine
 * (e.g., sector size) must be filled in before calling us.
 * Returns null on success and an error string on failure.
 */
char *
readdisklabel(dev, strat, lp)
	dev_t dev;
	int (*strat)();
	register struct disklabel *lp;
{
	register struct buf *bp;
	struct disklabel *dlp;
	char *msg = NULL;

	if (lp->d_secperunit == 0)
		lp->d_secperunit = 0x1fffffff;
	lp->d_npartitions = 1;
	if (lp->d_partitions[0].p_size == 0)
		lp->d_partitions[0].p_size = 0x1fffffff;
	lp->d_partitions[0].p_offset = 0;

	bp = geteblk((int)lp->d_secsize);
	bp->b_dev = dev;
	bp->b_blkno = LABELSECTOR;
	bp->b_bcount = lp->d_secsize;
	bp->b_flags = B_BUSY | B_READ;
	bp->b_cylin = LABELSECTOR / lp->d_secpercyl;
	(*strat)(bp);
	biowait(bp);
	if (bp->b_flags & B_ERROR) {
		u.u_error = 0;		/* XXX */
		msg = "I/O error";
	} else for (dlp = (struct disklabel *)bp->b_un.b_addr;
	    dlp <= (struct disklabel *)(bp->b_un.b_addr+DEV_BSIZE-sizeof(*dlp));
	    dlp = (struct disklabel *)((char *)dlp + sizeof(long))) {
		if (dlp->d_magic != DISKMAGIC || dlp->d_magic2 != DISKMAGIC) {
			if (msg == NULL)
				msg = "no disk label";
		} else if (dkcksum(dlp) != 0)
			msg = "disk label corrupted";
		else {
			*lp = *dlp;
			msg = NULL;
			break;
		}
	}
	if (lp->d_npartitions > MAXPARTITIONS)
		lp->d_npartitions = MAXPARTITIONS;
	bp->b_flags = B_INVAL | B_AGE;
	brelse(bp);
	return (msg);
}

/*
 * Check new disk label for sensibility
 * before setting it.
 */
setdisklabel(olp, nlp, openmask)
	register struct disklabel *olp, *nlp;
	u_long openmask;
{
	register i;
	register struct partition *opp, *npp;

	if (nlp->d_magic != DISKMAGIC || nlp->d_magic2 != DISKMAGIC ||
	    dkcksum(nlp) != 0)
		return (EINVAL);
	while ((i = ffs(openmask)) != 0) {
		i--;
		openmask &= ~(1 << i);
		if (nlp->d_npartitions <= i)
			return (EBUSY);
		opp = &olp->d_partitions[i];
		npp = &nlp->d_partitions[i];
		if (npp->p_offset != opp->p_offset || npp->p_size < opp->p_size)
			return (EBUSY);
		/*
		 * Copy internally-set partition information
		 * if new label doesn't include it.		XXX
		 */
		if (npp->p_fstype == FS_UNUSED && opp->p_fstype != FS_UNUSED) {
			npp->p_fstype = opp->p_fstype;
			npp->p_fsize = opp->p_fsize;
			npp->p_frag = opp->p_frag;
			npp->p_cpg = opp->p_cpg;
		}
	}
 	nlp->d_checksum = 0;
 	nlp->d_checksum = dkcksum(nlp);
	*olp = *nlp;
	return (0);
}

/* encoding of disk minor numbers, should be elsewhere... */
#define dkunit(dev)		(minor(dev) >> 3)
#define dkpart(dev)		(minor(dev) & 07)
#define dkminor(unit, part)	(((unit) << 3) | (part))

/*
 * Write disk label back to device after modification.
 */
writedisklabel(dev, strat, lp)
	dev_t dev;
	int (*strat)();
	register struct disklabel *lp;
{
	struct buf *bp;
	struct disklabel *dlp;
	int labelpart;
	int error = 0;

	labelpart = dkpart(dev);
	if (lp->d_partitions[labelpart].p_offset != 0) {
		if (lp->d_partitions[0].p_offset != 0)
			return (EXDEV);			/* not quite right */
		labelpart = 0;
	}
	bp = geteblk((int)lp->d_secsize);
	bp->b_dev = makedev(major(dev), dkminor(dkunit(dev), labelpart));
	bp->b_blkno = LABELSECTOR;
	bp->b_bcount = lp->d_secsize;
	bp->b_flags = B_READ;
	(*strat)(bp);
	biowait(bp);
	if (bp->b_flags & B_ERROR) {
		error = u.u_error;		/* XXX */
		u.u_error = 0;
		goto done;
	}
	for (dlp = (struct disklabel *)bp->b_un.b_addr;
	    dlp <= (struct disklabel *)
	      (bp->b_un.b_addr + lp->d_secsize - sizeof(*dlp));
	    dlp = (struct disklabel *)((char *)dlp + sizeof(long))) {
		if (dlp->d_magic == DISKMAGIC && dlp->d_magic2 == DISKMAGIC &&
		    dkcksum(dlp) == 0) {
			*dlp = *lp;
			bp->b_flags = B_WRITE;
			(*strat)(bp);
			biowait(bp);
			if (bp->b_flags & B_ERROR) {
				error = u.u_error;		/* XXX */
				u.u_error = 0;
			}
			goto done;
		}
	}
	error = ESRCH;
done:
	brelse(bp);
	return (error);
}

/*
 * Compute checksum for disk label.
 */
dkcksum(lp)
	register struct disklabel *lp;
{
	register u_short *start, *end;
	register u_short sum = 0;

	start = (u_short *)lp;
	end = (u_short *)&lp->d_partitions[lp->d_npartitions];
	while (start < end)
		sum ^= *start++;
	return (sum);
}