dossrv: Implement support for != 512 sector and track sizes

The iotrack buffer layer always assumed 512 byte sector
size and 9 sectors per track.

To support 4K sector size fats, make the iotrack code
deal with it.

Instead of the fixed size Track structure, we just allocate
the pointers and buffers dynamically, and move the sector
size and tack size in the Xfs structure.

Tracks can still be reused between differnet file-systems
after a purgetrack().

The initial fat header has to be read with devread()
instead of getsect() to determine the sector/track size
of the file-system.

7 files changed, 204 insertions, 229 deletions

diff --git a/sys/src/cmd/dossrv/dat.h b/sys/src/cmd/dossrv/dat.h
index 80af491b0..7546d229f 100644
--- a/sys/src/cmd/dossrv/dat.h
+++ b/sys/src/cmd/dossrv/dat.h
@@ -118,7 +118,6 @@ struct Fatinfo
  */
 struct Dosbpb{
 	MLock;				/* access to fat */
-	int	sectsize;		/* in bytes */
 	int	clustsize;		/* in sectors */
 	int	nresrv;			/* sectors */
 	int	nfats;			/* usually 2; modified to 1 if fat mirroring disabled */
@@ -190,7 +189,7 @@ struct Dosptr{
 	Dosdir *d;
 };
 
-#define	QIDPATH(p)	((p)->addr*(Sectorsize/DOSDIRSIZE) + \
+#define	QIDPATH(p, xf)	((p)->addr*((xf)->sectsize/DOSDIRSIZE) + \
 			 (p)->offset/DOSDIRSIZE)
 
 struct Xfs{
@@ -203,6 +202,8 @@ struct Xfs{
 	uchar	isfat32;	/* is a fat 32 file system? */
 	short	dev;
 	short	fmt;
+	int	sectsize;
+	int	sect2trk;
 	vlong	offset;
 	void	*ptr;
 };
diff --git a/sys/src/cmd/dossrv/devio.c b/sys/src/cmd/dossrv/devio.c
index 5193bdafd..2caaaa064 100644
--- a/sys/src/cmd/dossrv/devio.c
+++ b/sys/src/cmd/dossrv/devio.c
@@ -7,7 +7,7 @@
 int readonly;
 
 static int
-deverror(char *name, Xfs *xf, long addr, long n, long nret)
+deverror(char *name, Xfs *xf, vlong addr, long n, long nret)
 {
 	errno = Eio;
 	if(nret < 0){
@@ -16,7 +16,7 @@ deverror(char *name, Xfs *xf, long addr, long n, long nret)
 		xf->dev = -1;
 		return -1;
 	}
-	fprint(2, "dev %d sector %ld, %s: %ld, should be %ld\n", xf->dev, addr, name, nret, n);
+	fprint(2, "dev %d sector %lld, %s: %ld, should be %ld\n", xf->dev, addr, name, nret, n);
 	return -1;
 }
 
@@ -27,7 +27,7 @@ devread(Xfs *xf, vlong addr, void *buf, long n)
 
 	if(xf->dev < 0)
 		return -1;
-	nread = pread(xf->dev, buf, n, xf->offset+addr*Sectorsize);
+	nread = pread(xf->dev, buf, n, xf->offset+addr*xf->sectsize);
 	if (nread == n)
 		return 0;
 	return deverror("read", xf, addr, n, nread);
@@ -43,23 +43,8 @@ devwrite(Xfs *xf, vlong addr, void *buf, long n)
 
 	if(xf->dev < 0)
 		return -1;
-	nwrite = pwrite(xf->dev, buf, n, xf->offset+addr*Sectorsize);
+	nwrite = pwrite(xf->dev, buf, n, xf->offset+addr*xf->sectsize);
 	if (nwrite == n)
 		return 0;
 	return deverror("write", xf, addr, n, nwrite);
 }
-
-int
-devcheck(Xfs *xf)
-{
-	char buf[Sectorsize];
-
-	if(xf->dev < 0)
-		return -1;
-	if(pread(xf->dev, buf, Sectorsize, 0) != Sectorsize){
-		close(xf->dev);
-		xf->dev = -1;
-		return -1;
-	}
-	return 0;
-}
diff --git a/sys/src/cmd/dossrv/dosfs.c b/sys/src/cmd/dossrv/dosfs.c
index 72c94768e..3acd0ea33 100644
--- a/sys/src/cmd/dossrv/dosfs.c
+++ b/sys/src/cmd/dossrv/dosfs.c
@@ -138,7 +138,7 @@ rwalk(void)
 				if(isroot(dp->addr))
 					f->qid.path = f->xf->rootqid.path;
 				else
-					f->qid.path = QIDPATH(dp);
+					f->qid.path = QIDPATH(dp, f->xf);
 			}
 		}else{
 			fixname(req->wname[rep->nwqid]);
@@ -155,7 +155,7 @@ rwalk(void)
 			if(r < 0)
 				goto error;
 			memmove(f->ptr, dp, sizeof(Dosptr));
-			f->qid.path = QIDPATH(dp);
+			f->qid.path = QIDPATH(dp, f->xf);
 			f->qid.type = QTFILE;
 			if(isroot(dp->addr))
 				f->qid.path = f->xf->rootqid.path;
@@ -457,7 +457,7 @@ badperm:
 	 */
 	f->ptr = ndp;
 	f->qid.type = QTFILE;
-	f->qid.path = QIDPATH(ndp);
+	f->qid.path = QIDPATH(ndp, f->xf);
 
 //ZZZ set type for excl, append?
 	if(req->perm & DMDIR){
@@ -567,7 +567,7 @@ doremove(Xfs *xf, Dosptr *dp)
 	}
 	if(prevdo < 0 && dp->prevaddr != -1){
 		p = getsect(xf, dp->prevaddr);
-		for(prevdo = ((Dosbpb*)xf->ptr)->sectsize-DOSDIRSIZE; prevdo >= 0; prevdo -= DOSDIRSIZE){
+		for(prevdo = xf->sectsize-DOSDIRSIZE; prevdo >= 0; prevdo -= DOSDIRSIZE){
 			if(p->iobuf[prevdo+11] != 0xf)
 				break;
 			p->iobuf[prevdo] = DOSEMPTY;
@@ -636,17 +636,17 @@ out:
 static int
 dostat(Xfile *f, Dir *d)
 {
-	Dosptr *dp;
+	Xfs *xf = f->xf;
+	Dosptr *dp = f->ptr;
 	Iosect *p;
 	char *name, namebuf[DOSNAMELEN];
 	int islong, sum, prevdo;
 
-	dp = f->ptr;
 	if(isroot(dp->addr)){
 		memset(d, 0, sizeof(Dir));
 		d->name = "/";
 		d->qid.type = QTDIR;
-		d->qid.path = f->xf->rootqid.path;
+		d->qid.path = xf->rootqid.path;
 		d->mode = DMDIR|0777;
 		d->uid = "bill";
 		d->muid = "bill";
@@ -664,17 +664,17 @@ dostat(Xfile *f, Dir *d)
 			name = getnamesect(namebuf, name, &dp->p->iobuf[prevdo], &islong, &sum, -1);
 		}
 		if(prevdo < 0 && dp->prevaddr != -1){
-			p = getsect(f->xf, dp->prevaddr);
+			p = getsect(xf, dp->prevaddr);
 			if(p == nil)
 				return -1;
-			for(prevdo = ((Dosbpb*)f->xf->ptr)->sectsize-DOSDIRSIZE; prevdo >= 0; prevdo -= DOSDIRSIZE){
+			for(prevdo = xf->sectsize-DOSDIRSIZE; prevdo >= 0; prevdo -= DOSDIRSIZE){
 				if(p->iobuf[prevdo+11] != 0xf)
 					break;
 				name = getnamesect(namebuf, name, &p->iobuf[prevdo], &islong, &sum, -1);
 			}
 			putsect(p);
 		}
-		getdir(f->xf, d, dp->d, dp->addr, dp->offset);
+		getdir(xf, d, dp->d, dp->addr, dp->offset);
 		if(islong && sum == -1 && nameok(namebuf))
 			strcpy(d->name, namebuf);
 	}
@@ -894,7 +894,7 @@ rwstat(void)
 		/*
 		 * relocate up other fids to the same file, if it moved
 		 */
-		f->qid.path = QIDPATH(dp);
+		f->qid.path = QIDPATH(dp, pf.xf);
 		if(oaddr != dp->addr || ooffset != dp->offset)
 			dosptrreloc(f, dp, oaddr, ooffset);
 
diff --git a/sys/src/cmd/dossrv/dossubs.c b/sys/src/cmd/dossrv/dossubs.c
index d77062554..eaabcd8bb 100644
--- a/sys/src/cmd/dossrv/dossubs.c
+++ b/sys/src/cmd/dossrv/dossubs.c
@@ -39,9 +39,10 @@ isdosfs(uchar *buf)
 int
 dosfs(Xfs *xf)
 {
-	Iosect *p, *p1;
-	Dosboot *b;
+	Iosect *p1;
 	Fatinfo *fi;
+	uchar	buf[512];
+	Dosboot *b;
 	Dosboot32 *b32;
 	Dosbpb *bp;
 	long fisec, extflags;
@@ -72,22 +73,28 @@ dosfs(Xfs *xf)
 		isdos['&'] = 1;
 	}
 
-	p = getsect(xf, 0);
-	if(p == nil)
+	/* don't use getsect() before we we determinted real values */
+	xf->sectsize = 512;
+	xf->sect2trk = 9;
+	devread(xf, 0, buf, sizeof(buf));
+
+	if(!isdosfs(buf))
 		return -1;
 
-	b = (Dosboot*)p->iobuf;
-	if(b->clustsize == 0 || isdosfs(p->iobuf) == 0){
-		putsect(p);
+	b = (Dosboot*)buf;
+
+	xf->sectsize = GSHORT(b->sectsize);
+	if(xf->sectsize < 32)
+		return -1;
+
+	xf->sect2trk = GSHORT(b->trksize);
+	if(xf->sect2trk < 1)
 		return -1;
-	}
 
 	bp = malloc(sizeof(Dosbpb));
 	memset(bp, 0, sizeof(Dosbpb));	/* clear lock */
 	xf->ptr = bp;
 	xf->fmt = 1;
-
-	bp->sectsize = GSHORT(b->sectsize);
 	bp->clustsize = b->clustsize;
 	bp->nresrv = GSHORT(b->nresrv);
 	bp->nfats = b->nfats;
@@ -102,13 +109,12 @@ dosfs(Xfs *xf)
 	bp->fatinfo = 0;
 
 	if(bp->fatsize == 0){	/* is FAT32 */
+		b32 = (Dosboot32*)buf;
 		if(chatty)
-			bootsecdump32(2, xf, (Dosboot32*)b);
+			bootsecdump32(2, xf, b32);
 		xf->isfat32 = 1;
-		b32 = (Dosboot32*)b;
 		bp->fatsize = GLONG(b32->fatsize32);
 		if(bp->fatsize == 0){
-			putsect(p);
 			if(chatty)
 				fprint(2, "fatsize 0\n");
 			return -1;
@@ -155,7 +161,7 @@ dosfs(Xfs *xf)
 			bootdump(2, b);
 		bp->rootaddr = bp->fataddr + bp->nfats*bp->fatsize;
 		bp->rootstart = 0;
-		bp->dataaddr = bp->rootaddr + (bp->rootsize*DOSDIRSIZE + bp->sectsize-1)/bp->sectsize;
+		bp->dataaddr = bp->rootaddr + (bp->rootsize*DOSDIRSIZE + xf->sectsize-1)/xf->sectsize;
 		bp->freeptr = FATRESRV;
 	}
 	bp->fatclusters = FATRESRV + (bp->volsize - bp->dataaddr)/bp->clustsize;
@@ -172,7 +178,6 @@ dosfs(Xfs *xf)
 		chat("fat %d: %lld...", i, bp->fataddr+i*bp->fatsize);
 	chat("root: %lld...", bp->rootaddr);
 	chat("data: %lld...", bp->dataaddr);
-	putsect(p);
 	return 0;
 }
 
@@ -215,8 +220,8 @@ getfile(Xfile *f)
 	 */
 	dp->d = nil;
 	if(!isroot(dp->addr)){
-		if(f->qid.path != QIDPATH(dp)){
-			chat("qid mismatch f=%#llux d=%#llux...", f->qid.path, QIDPATH(dp));
+		if(f->qid.path != QIDPATH(dp, f->xf)){
+			chat("qid mismatch f=%#llux d=%#llux...", f->qid.path, QIDPATH(dp, f->xf));
 			putsect(p);
 			errno = Enonexist;
 			return -1;
@@ -265,33 +270,29 @@ putstart(Xfs *xf, Dosdir *d, long start)
 long
 fileclust(Xfile *f, long iclust, int cflag)
 {
-	Dosbpb *bp;
-	Dosptr *dp;
-	Dosdir *d;
-	long start, clust, nskip, next;
-
-	bp = f->xf->ptr;
-	dp = f->ptr;
-	d = dp->d;
-	next = 0;
+	Xfs *xf = f->xf;
+	Dosbpb *bp = xf->ptr;
+	Dosptr *dp = f->ptr;
+	Dosdir *d = dp->d;
+	long start, clust, nskip, next = 0;
 
 	/* 
 	 * asking for the cluster of the root directory
 	 * is not a well-formed question, since the root directory
 	 * does not begin on a cluster boundary.
 	 */
-	if(!f->xf->isfat32 && isroot(dp->addr))
+	if(!xf->isfat32 && isroot(dp->addr))
 		return -1;
 
-	if(f->xf->isfat32 && isroot(dp->addr)){
+	if(xf->isfat32 && isroot(dp->addr)){
 		start = bp->rootstart;
 	}else{
-		start = getstart(f->xf, d);
+		start = getstart(xf, d);
 		if(start == 0){
 			if(!cflag)
 				return -1;
 			mlock(bp);
-			start = falloc(f->xf);
+			start = falloc(xf);
 			unmlock(bp);
 			if(start <= 0)
 				return -1;
@@ -315,7 +316,7 @@ fileclust(Xfile *f, long iclust, int cflag)
 	if(nskip > 0){
 		mlock(bp);
 		while(--nskip >= 0){
-			next = getfat(f->xf, clust);
+			next = getfat(xf, clust);
 			if(chatty > 1)
 				chat("->%#lx", next);
 			if(next > 0){
@@ -329,10 +330,10 @@ fileclust(Xfile *f, long iclust, int cflag)
 					break;
 				/* cfalloc will call putfat for us, since clust may change */
 			} else {
-				next = falloc(f->xf);
+				next = falloc(xf);
 				if(next < 0)
 					break;
-				putfat(f->xf, clust, next);
+				putfat(xf, clust, next);
 			}
 			clust = next;
 		}
@@ -353,14 +354,15 @@ fileclust(Xfile *f, long iclust, int cflag)
 vlong
 fileaddr(Xfile *f, long isect, int cflag)
 {
+	Xfs *xf = f->xf;
 	Dosbpb *bp;
 	Dosptr *dp;
 	long clust;
 
-	bp = f->xf->ptr;
+	bp = xf->ptr;
 	dp = f->ptr;
 	if(!f->xf->isfat32 && isroot(dp->addr)){
-		if(isect*bp->sectsize >= bp->rootsize*DOSDIRSIZE)
+		if(isect*xf->sectsize >= bp->rootsize*DOSDIRSIZE)
 			return -1;
 		return bp->rootaddr + isect;
 	}
@@ -512,14 +514,12 @@ searchdir(Xfile *f, char *name, Dosptr *dp, int cflag, int longtype)
 {
 	Xfs *xf;
 	Iosect *p;
-	Dosbpb *bp;
 	Dosdir *d;
 	char buf[261], *bname;
 	int isect, o, o1, islong, have, need, sum;
 	vlong addr, addr1, addr2, prevaddr, prevaddr1;
 
 	xf = f->xf;
-	bp = xf->ptr;
 	addr1 = -1;
 	addr2 = -1;
 	prevaddr1 = -1;
@@ -548,7 +548,7 @@ searchdir(Xfile *f, char *name, Dosptr *dp, int cflag, int longtype)
 		p = getsect(xf, addr);
 		if(p == nil)
 			break;
-		for(o=0; o<bp->sectsize; o+=DOSDIRSIZE){
+		for(o=0; o<xf->sectsize; o+=DOSDIRSIZE){
 			d = (Dosdir *)&p->iobuf[o];
 			if(d->name[0] == 0x00){
 				chat("end dir(0)...");
@@ -569,7 +569,7 @@ searchdir(Xfile *f, char *name, Dosptr *dp, int cflag, int longtype)
 					prevaddr1 = prevaddr;
 					o1 = o;
 				}
-				if(addr2 < 0 && (bp->sectsize-o)/DOSDIRSIZE + have < need){
+				if(addr2 < 0 && (xf->sectsize-o)/DOSDIRSIZE + have < need){
 					addr2 = fileaddr(f, isect+1, cflag);
 					if(addr2 < 0)
 						goto breakout;
@@ -641,7 +641,6 @@ int
 emptydir(Xfile *f)
 {
 	Xfs *xf = f->xf;
-	Dosbpb *bp = xf->ptr;
 	int isect, o;
 	vlong addr;
 	Iosect *p;
@@ -654,7 +653,7 @@ emptydir(Xfile *f)
 		p = getsect(xf, addr);
 		if(p == nil)
 			return -1;
-		for(o=0; o<bp->sectsize; o+=DOSDIRSIZE){
+		for(o=0; o<xf->sectsize; o+=DOSDIRSIZE){
 			d = (Dosdir *)&p->iobuf[o];
 			if(d->name[0] == 0x00){
 				putsect(p);
@@ -678,7 +677,6 @@ long
 readdir(Xfile *f, void *vbuf, vlong offset, long count)
 {
 	Xfs *xf;
-	Dosbpb *bp;
 	Dir dir;
 	int isect, o, islong, sum;
 	vlong addr;
@@ -691,7 +689,6 @@ readdir(Xfile *f, void *vbuf, vlong offset, long count)
 	buf = vbuf;
 	rcnt = 0;
 	xf = f->xf;
-	bp = xf->ptr;
 	if(count <= 0)
 		return 0;
 	islong = 0;
@@ -704,7 +701,7 @@ readdir(Xfile *f, void *vbuf, vlong offset, long count)
 		p = getsect(xf, addr);
 		if(p == nil)
 			return -1;
-		for(o=0; o<bp->sectsize; o+=DOSDIRSIZE){
+		for(o=0; o<xf->sectsize; o+=DOSDIRSIZE){
 			d = (Dosdir *)&p->iobuf[o];
 			if(d->name[0] == 0x00){
 				putsect(p);
@@ -763,15 +760,14 @@ readdir(Xfile *f, void *vbuf, vlong offset, long count)
 int
 walkup(Xfile *f, Dosptr *ndp)
 {
-	Dosbpb *bp;
-	Dosptr *dp;
+	Xfs *xf = f->xf;
+	Dosbpb *bp = xf->ptr;
+	Dosptr *dp = f->ptr;
 	Dosdir *xd;
 	Iosect *p;
 	long o, so, start, pstart, ppstart, st, ppclust;
 	vlong k;
 
-	bp = f->xf->ptr;
-	dp = f->ptr;
 	memset(ndp, 0, sizeof(Dosptr));
 	ndp->prevaddr = -1;
 	ndp->naddr = -1;
@@ -789,12 +785,12 @@ walkup(Xfile *f, Dosptr *ndp)
 	/*
 	 * find the start of our parent's directory
 	 */
-	p = getsect(f->xf, dp->paddr);
+	p = getsect(xf, dp->paddr);
 	if(p == nil)
 		goto error;
 	xd = (Dosdir *)&p->iobuf[dp->poffset];
 	dirdump(xd);
-	start = getstart(f->xf, xd);
+	start = getstart(xf, xd);
 	chat("start=%#lx...", start);
 	if(start == 0)
 		goto error;
@@ -808,7 +804,7 @@ walkup(Xfile *f, Dosptr *ndp)
 		goto error;
 	xd = (Dosdir *)p->iobuf;
 	dirdump(xd);
-	st = getstart(f->xf, xd);
+	st = getstart(xf, xd);
 	if(xd->name[0]!='.' || xd->name[1]!=' ' || start!=st)
 		goto error;
 
@@ -819,26 +815,26 @@ walkup(Xfile *f, Dosptr *ndp)
 	dirdump(xd);
 	if(xd->name[0] != '.' || xd->name[1] != '.')
 		goto error;
-	pstart = getstart(f->xf, xd);
+	pstart = getstart(xf, xd);
 	putsect(p);
 
 	/*
 	 * we're done if parent is root
 	 */
-	if(pstart == 0 || f->xf->isfat32 && pstart == bp->rootstart)
+	if(pstart == 0 || xf->isfat32 && pstart == bp->rootstart)
 		return 0;
 
 	/*
 	 * verify that parent's . points to itself
 	 */
-	p = getsect(f->xf, clust2sect(bp, pstart));
+	p = getsect(xf, clust2sect(bp, pstart));
 	if(p == nil){
 		chat("getsect %ld failed\n", pstart);
 		goto error;
 	}
 	xd = (Dosdir *)p->iobuf;
 	dirdump(xd);
-	st = getstart(f->xf, xd);
+	st = getstart(xf, xd);
 	if(xd->name[0]!='.' || xd->name[1]!=' ' || pstart!=st)
 		goto error;
 
@@ -849,7 +845,7 @@ walkup(Xfile *f, Dosptr *ndp)
 	dirdump(xd);
 	if(xd->name[0] != '.' || xd->name[1] != '.')
 		goto error;
-	ppstart = getstart(f->xf, xd);
+	ppstart = getstart(xf, xd);
 	putsect(p);
 
 	/*
@@ -857,12 +853,12 @@ walkup(Xfile *f, Dosptr *ndp)
 	 * need this to find parent's parent's addr and offset
 	 */
 	ppclust = ppstart;
-	if(f->xf->isfat32 && ppclust == 0){
+	if(xf->isfat32 && ppclust == 0){
 		ppclust = bp->rootstart;
 		chat("ppclust 0, resetting to rootstart\n");
 	}
 	k = ppclust ? clust2sect(bp, ppclust) : bp->rootaddr;
-	p = getsect(f->xf, k);
+	p = getsect(xf, k);
 	if(p == nil){
 		chat("getsect %lld failed\n", k);
 		goto error;
@@ -870,12 +866,12 @@ walkup(Xfile *f, Dosptr *ndp)
 	xd = (Dosdir *)p->iobuf;
 	dirdump(xd);
 	if(ppstart){
-		st = getstart(f->xf, xd);
+		st = getstart(xf, xd);
 		if(xd->name[0]!='.' || xd->name[1]!=' ' || ppstart!=st)
 			goto error;
 	}
 	for(so=1;; so++){
-		for(o=0; o<bp->sectsize; o+=DOSDIRSIZE){
+		for(o=0; o<xf->sectsize; o+=DOSDIRSIZE){
 			xd = (Dosdir *)&p->iobuf[o];
 			if(xd->name[0] == 0x00){
 				chat("end dir\n");
@@ -883,14 +879,14 @@ walkup(Xfile *f, Dosptr *ndp)
 			}
 			if(xd->name[0] == DOSEMPTY)
 				continue;
-			st = getstart(f->xf, xd);
+			st = getstart(xf, xd);
 			if(st == pstart)
 				goto out;
 		}
 		if(ppclust){
 			if(so%bp->clustsize == 0){
 				mlock(bp);
-				ppclust = getfat(f->xf, ppclust);
+				ppclust = getfat(xf, ppclust);
 				unmlock(bp);
 				if(ppclust < 0){
 					chat("getfat %ld failed\n", ppclust);
@@ -899,12 +895,12 @@ walkup(Xfile *f, Dosptr *ndp)
 			}
 			k = clust2sect(bp, ppclust) + so%bp->clustsize;
 		}else{
-			if(so*bp->sectsize >= bp->rootsize*DOSDIRSIZE)
+			if(so*xf->sectsize >= bp->rootsize*DOSDIRSIZE)
 				goto error;
 			k = bp->rootaddr + so;
 		}
 		putsect(p);
-		p = getsect(f->xf, k);
+		p = getsect(xf, k);
 		if(p == nil){
 			chat("getsect %lld failed\n", k);
 			goto error;
@@ -926,7 +922,6 @@ long
 readfile(Xfile *f, void *vbuf, vlong offset, long count)
 {
 	Xfs *xf = f->xf;
-	Dosbpb *bp = xf->ptr;
 	Dosptr *dp = f->ptr;
 	Dosdir *d = dp->d;
 	int isect, o, c;
@@ -947,13 +942,13 @@ readfile(Xfile *f, void *vbuf, vlong offset, long count)
 		return 0;
 	if(offset+count >= length)
 		count = length - offset;
-	isect = offset/bp->sectsize;
-	o = offset%bp->sectsize;
+	isect = offset/xf->sectsize;
+	o = offset%xf->sectsize;
 	while(count > 0){
 		addr = fileaddr(f, isect++, 0);
 		if(addr < 0)
 			break;
-		c = bp->sectsize - o;
+		c = xf->sectsize - o;
 		if(c > count)
 			c = count;
 		p = getsect(xf, addr);
@@ -989,16 +984,16 @@ writefile(Xfile *f, void *vbuf, vlong offset, long count)
 	rcnt = 0;
 	addr = 0;
 	buf = vbuf;
-	isect = offset/bp->sectsize;
-	o = offset%bp->sectsize;
+	isect = offset/xf->sectsize;
+	o = offset%xf->sectsize;
 	while(count > 0){
 		addr = fileaddr(f, isect++, 1);
 		if(addr < 0)
 			break;
-		c = bp->sectsize - o;
+		c = xf->sectsize - o;
 		if(c > count)
 			c = count;
-		if(c == bp->sectsize){
+		if(c == xf->sectsize){
 			p = getosect(xf, addr);
 			p->flags = 0;
 		}else{
@@ -1020,7 +1015,7 @@ writefile(Xfile *f, void *vbuf, vlong offset, long count)
 	if(rcnt > 0)
 		length = offset+rcnt;
 	else if(dp->addr && dp->clust){
-		c = bp->clustsize*bp->sectsize;
+		c = bp->clustsize*xf->sectsize;
 		if(dp->iclust > (dlen+c-1)/c)
 			length = (ulong)c*dp->iclust;
 	}
@@ -1045,18 +1040,18 @@ truncfile(Xfile *f, vlong length)
 		return -1;
 
 	mlock(bp);
-	clust = getstart(f->xf, d);
+	clust = getstart(xf, d);
 	n = length;
 	if(n <= 0)
-		putstart(f->xf, d, 0);
+		putstart(xf, d, 0);
 	else
-		n -= bp->sectsize;
+		n -= xf->sectsize;
 	while(clust > 0){
 		next = getfat(xf, clust);
 		if(n <= 0)
 			putfat(xf, clust, 0);
 		else
-			n -= bp->clustsize*bp->sectsize;
+			n -= bp->clustsize*xf->sectsize;
 		clust = next;
 	}
 	unmlock(bp);
@@ -1089,7 +1084,7 @@ putdir(Dosdir *d, Dir *dp)
  * creation and access dates
  */
 void
-getdir(Xfs *xfs, Dir *dp, Dosdir *d, vlong addr, int offset)
+getdir(Xfs *xf, Dir *dp, Dosdir *d, vlong addr, int offset)
 {
 	if(d == nil || addr == 0)
 		panic("getdir on root");
@@ -1097,7 +1092,7 @@ getdir(Xfs *xfs, Dir *dp, Dosdir *d, vlong addr, int offset)
 	dp->dev = 0;
 	getname(dp->name, d);
 
-	dp->qid.path = addr*(Sectorsize/DOSDIRSIZE) +
+	dp->qid.path = addr*(xf->sectsize/DOSDIRSIZE) +
 			offset/DOSDIRSIZE;
 	dp->qid.vers = 0;
 
@@ -1116,7 +1111,7 @@ getdir(Xfs *xfs, Dir *dp, Dosdir *d, vlong addr, int offset)
 		dp->length = GLONG(d->length);
 	if(d->attr & DSYSTEM){
 		dp->mode |= DMEXCL;
-		if(iscontig(xfs, d))
+		if(iscontig(xf, d))
 			dp->mode |= DMAPPEND;
 	}
 
@@ -1308,7 +1303,6 @@ aliassum(Dosdir *d)
 int
 putlongname(Xfs *xf, Dosptr *ndp, char *name, char sname[13])
 {
-	Dosbpb *bp;
 	Dosdir tmpd;
 	Rune longname[DOSNAMELEN+1];
 	int i, first, sum, nds, len;
@@ -1317,7 +1311,6 @@ putlongname(Xfs *xf, Dosptr *ndp, char *name, char sname[13])
 	putname(sname, &tmpd);
 	sum = aliassum(&tmpd);
 
-	bp = xf->ptr;
 	first = 1;
 	len = utftorunes(longname, name, DOSNAMELEN);
 	if(chatty){
@@ -1330,7 +1323,7 @@ putlongname(Xfs *xf, Dosptr *ndp, char *name, char sname[13])
 		putnamesect(&ndp->p->iobuf[ndp->offset], longname, nds, first, sum);
 		first = 0;
 		ndp->offset += 32;
-		if(ndp->offset == bp->sectsize){
+		if(ndp->offset == xf->sectsize){
 			chat("long name moving over sector boundary\n");
 			ndp->p->flags |= BMOD;
 			putsect(ndp->p);
@@ -1368,15 +1361,15 @@ getfat(Xfs *xf, long n)
 		return -1;
 	fb = bp->fatbits;
 	k = (fb * n) >> 3;
-	if(k >= bp->fatsize*bp->sectsize)
+	if(k >= bp->fatsize*xf->sectsize)
 		panic("getfat");
-	sect = k/bp->sectsize + bp->fataddr;
-	o = k%bp->sectsize;
+	sect = k/xf->sectsize + bp->fataddr;
+	o = k%xf->sectsize;
 	p = getsect(xf, sect);
 	if(p == nil)
 		return -1;
 	k = p->iobuf[o++];
-	if(o >= bp->sectsize){
+	if(o >= xf->sectsize){
 		putsect(p);
 		p = getsect(xf, sect+1);
 		if(p == nil)
@@ -1426,12 +1419,12 @@ putfat(Xfs *xf, int n, ulong val)
 	if(n < FATRESRV || n >= bp->fatclusters)
 		panic("putfat n=%d", n);
 	k = (bp->fatbits * n) >> 3;
-	if(k >= bp->fatsize*bp->sectsize)
+	if(k >= bp->fatsize*xf->sectsize)
 		panic("putfat");
-	sect = k/bp->sectsize + bp->fataddr;
+	sect = k/xf->sectsize + bp->fataddr;
 	esect = sect + bp->nfats * bp->fatsize;
 	for(; sect<esect; sect+=bp->fatsize){
-		o = k%bp->sectsize;
+		o = k%xf->sectsize;
 		p = getsect(xf, sect);
 		if(p == nil)
 			continue;
@@ -1440,7 +1433,7 @@ putfat(Xfs *xf, int n, ulong val)
 			if(n&1){
 				p->iobuf[o] &= 0x0f;
 				p->iobuf[o++] |= val<<4;
-				if(o >= bp->sectsize){
+				if(o >= xf->sectsize){
 					p->flags |= BMOD;
 					putsect(p);
 					p = getsect(xf, sect+1);
@@ -1451,7 +1444,7 @@ putfat(Xfs *xf, int n, ulong val)
 				p->iobuf[o] = val>>4;
 			}else{
 				p->iobuf[o++] = val;
-				if(o >= bp->sectsize){
+				if(o >= xf->sectsize){
 					p->flags |= BMOD;
 					putsect(p);
 					p = getsect(xf, sect+1);
@@ -1633,7 +1626,7 @@ makecontig(Xfile *f, int nextra)
 				return -1;
 			wp = getosect(xf, ws);
 			assert(wp != nil);
-			memmove(wp->iobuf, rp->iobuf, bp->sectsize);
+			memmove(wp->iobuf, rp->iobuf, xf->sectsize);
 			wp->flags = BMOD;
 			putsect(rp);
 			putsect(wp);
@@ -1702,7 +1695,7 @@ falloc(Xfs *xf)
 	k = clust2sect(bp, n);
 	for(i=0; i<bp->clustsize; i++){
 		p = getosect(xf, k+i);
-		memset(p->iobuf, 0, bp->sectsize);
+		memset(p->iobuf, 0, xf->sectsize);
 		p->flags = BMOD;
 		putsect(p);
 	}
diff --git a/sys/src/cmd/dossrv/iotrack.c b/sys/src/cmd/dossrv/iotrack.c
index 6081a5509..f1833ae56 100644
--- a/sys/src/cmd/dossrv/iotrack.c
+++ b/sys/src/cmd/dossrv/iotrack.c
@@ -4,6 +4,9 @@
 #include "dat.h"
 #include "fns.h"
 
+static MLock	freelock;
+static Iosect *	freelist;
+
 #define	HIOB		31	/* a prime */
 #define	NIOBUF		80
 
@@ -19,6 +22,10 @@ static Iotrack	iobuf[NIOBUF];		/* the real ones */
 
 #define	TOFRONT(h, p)	((h)->next  != (p) && (UNLINK(p, next, prev), LINK(h,p, next, prev)))
 
+static Iotrack *getiotrack(Xfs*, vlong);
+static Iosect *getiosect(Xfs*, vlong, int);
+static void purgetrack(Iotrack*);
+
 Iosect *
 getsect(Xfs *xf, vlong addr)
 {
@@ -31,19 +38,21 @@ getosect(Xfs *xf, vlong addr)
 	return getiosect(xf, addr, 0);
 }
 
-Iosect *
+static Iosect *
 getiosect(Xfs *xf, vlong addr, int rflag)
 {
-	Iotrack *t;
 	vlong taddr;
 	int toff;
+	Iotrack *t;
 	Iosect *p;
 
 	if(addr < 0)
 		return nil;
-	toff = addr % Sect2trk;
+	toff = addr % xf->sect2trk;
 	taddr = addr - toff;
 	t = getiotrack(xf, taddr);
+	if(t == nil)
+		return nil;
 	if(rflag && (t->flags&BSTALE)){
 		if(tread(t) < 0){
 			unmlock(&t->lock);
@@ -51,16 +60,31 @@ getiosect(Xfs *xf, vlong addr, int rflag)
 		}
 		t->flags &= ~BSTALE;
 	}
-	t->ref++;
-	p = t->tp->p[toff];
-	if(p == 0){
-		p = newsect();
-		t->tp->p[toff] = p;
+	p = t->tp[toff];
+	if(p == nil){
+		mlock(&freelock);
+		p = freelist;
+		if(p != nil)
+			freelist = p->next;
+		else {
+			p = malloc(sizeof(Iosect));
+			if(p == nil) {
+				unmlock(&freelock);
+				unmlock(&t->lock);
+				return nil;
+			}
+		}
+		p->next = nil;
+		unmlock(&freelock);
+
 		p->flags = t->flags&BSTALE;
 		p->lock.key = 0;
+		p->iobuf = ((uchar*)&t->tp[xf->sect2trk]) + toff*xf->sectsize;
 		p->t = t;
-		p->iobuf = t->tp->buf[toff];
+
+		t->tp[toff] = p;
 	}
+	t->ref++;
 	unmlock(&t->lock);
 	mlock(&p->lock);
 	return p;
@@ -87,7 +111,7 @@ putsect(Iosect *p)
 	unmlock(&p->lock);
 }
 
-Iotrack *
+static Iotrack *
 getiotrack(Xfs *xf, vlong addr)
 {
 	Iotrack *hp, *p;
@@ -142,8 +166,14 @@ loop:
 		goto loop;
 	}
 	purgetrack(p);
-	p->addr = addr;
+	p->tp = malloc(xf->sect2trk*sizeof(Iosect*) + xf->sect2trk*xf->sectsize);
+	if(p->tp == nil){
+		unmlock(&p->lock);
+		return nil;
+	}
+	memset(p->tp, 0, xf->sect2trk*sizeof(Iosect*));
 	p->xf = xf;
+	p->addr = addr;
 	p->flags = BSTALE;
 out:
 	mlock(&hp->lock);
@@ -155,39 +185,55 @@ out:
 	return p;
 }
 
-void
+static void
 purgetrack(Iotrack *t)
 {
-	int i, ref = Sect2trk;
-	Iosect *p;
-
-	for(i=0; i<Sect2trk; i++){
-		p = t->tp->p[i];
-		if(p == 0){
-			--ref;
-			continue;
-		}
-		if(canmlock(&p->lock)){
-			freesect(p);
-			--ref;
-			t->tp->p[i] = 0;
+	if(t->tp != nil){
+		Xfs *xf = t->xf;
+		int i, ref = xf->sect2trk;
+
+		for(i=0; i<xf->sect2trk; i++){
+			Iosect *p = t->tp[i];
+			if(p == nil){
+				--ref;
+				continue;
+			}
+			if(canmlock(&p->lock)){
+				t->tp[i] = nil;
+
+				mlock(&freelock);
+				p->next = freelist;
+				freelist = p;
+				unmlock(&freelock);
+				--ref;
+			}
 		}
+		if(t->ref != ref)
+			panic("purgetrack");
+		if(ref != 0)
+			return;
+
+		free(t->tp);
 	}
-	if(t->ref != ref)
-		panic("purgetrack");
+	assert(t->ref == 0);
+	t->tp = nil;
+	t->xf = nil;
+	t->addr = -1;
+	t->flags = 0;
 }
 
 int
 twrite(Iotrack *t)
 {
-	int i, ref;
+	Xfs *xf = t->xf;
 
-	chat("[twrite %lld...", t->addr);
+	chat("[twrite %lld+%lld...", t->addr, xf->offset);
 	if(t->flags & BSTALE){
-		for(ref=0,i=0; i<Sect2trk; i++)
-			if(t->tp->p[i])
+		int i, ref = 0;
+		for(i=0; i<xf->sect2trk; i++)
+			if(t->tp[i] != nil)
 				++ref;
-		if(ref < Sect2trk){
+		if(ref < xf->sect2trk){
 			if(tread(t) < 0){
 				chat("error]");
 				return -1;
@@ -195,7 +241,7 @@ twrite(Iotrack *t)
 		}else
 			t->flags &= ~BSTALE;
 	}
-	if(devwrite(t->xf, t->addr, t->tp->buf, Trksize) < 0){
+	if(devwrite(xf, t->addr, (uchar*)&t->tp[xf->sect2trk], xf->sect2trk*xf->sectsize) < 0){
 		chat("error]");
 		return -1;
 	}
@@ -206,33 +252,31 @@ twrite(Iotrack *t)
 int
 tread(Iotrack *t)
 {
+	Xfs *xf = t->xf;
 	int i, ref = 0;
-	uchar buf[Sect2trk][Sectorsize];
 
-	for(i=0; i<Sect2trk; i++)
-		if(t->tp->p[i])
+	chat("[tread %lld+%lld...", t->addr, xf->offset);
+	for(i=0; i<xf->sect2trk; i++)
+		if(t->tp[i] != nil)
 			++ref;
-	chat("[tread %lld+%lld...", t->addr, t->xf->offset);
 	if(ref == 0){
-		if(devread(t->xf, t->addr, t->tp->buf, Trksize) < 0){
+		if(devread(xf, t->addr, (uchar*)&t->tp[xf->sect2trk], xf->sect2trk*xf->sectsize) < 0){
 			chat("error]");
 			return -1;
 		}
-		chat("done]");
-		t->flags &= ~BSTALE;
-		return 0;
-	}
-	if(devread(t->xf, t->addr, buf, Trksize) < 0){
-		chat("error]");
-		return -1;
-	}
-	for(i=0; i<Sect2trk; i++)
-		if(t->tp->p[i] == 0){
-			memmove(t->tp->buf[i], buf[i], Sectorsize);
+	} else {
+		for(i=0; i<xf->sect2trk; i++){
+			if(t->tp[i] != nil)
+				continue;
+			if(devread(xf, t->addr + i, ((uchar*)&t->tp[xf->sect2trk]) + i*xf->sectsize, xf->sectsize) < 0){
+				chat("error]");
+				return -1;
+			}
 			chat("%d ", i);
 		}
-	chat("done]");
+	}
 	t->flags &= ~BSTALE;
+	chat("done]");
 	return 0;
 }
 
@@ -285,34 +329,6 @@ iotrack_init(void)
 		p->hprev = p->hnext = p;
 		p->prev = p->next = p;
 		TOFRONT(mp, p);
-		p->tp = sbrk(sizeof(Track));
-		memset(p->tp->p, 0, sizeof p->tp->p);
+		purgetrack(p);
 	}
 }
-
-static MLock	freelock;
-static Iosect *	freelist;
-
-Iosect *
-newsect(void)
-{
-	Iosect *p;
-
-	mlock(&freelock);
-	if(p = freelist)	/* assign = */
-		freelist = p->next;
-	else
-		p = malloc(sizeof(Iosect));
-	unmlock(&freelock);
-	p->next = 0;
-	return p;
-}
-
-void
-freesect(Iosect *p)
-{
-	mlock(&freelock);
-	p->next = freelist;
-	freelist = p;
-	unmlock(&freelock);
-}
diff --git a/sys/src/cmd/dossrv/iotrack.h b/sys/src/cmd/dossrv/iotrack.h
index 921a75c3f..098677ab2 100644
--- a/sys/src/cmd/dossrv/iotrack.h
+++ b/sys/src/cmd/dossrv/iotrack.h
@@ -1,7 +1,6 @@
 typedef struct MLock	MLock;
 typedef	struct Iosect	Iosect;
 typedef	struct Iotrack	Iotrack;
-typedef struct Track	Track;
 typedef struct Xfs	Xfs;
 
 struct MLock
@@ -29,41 +28,23 @@ struct Iotrack
 	Iotrack	*hprev;
 	MLock	lock;
 	int	ref;
-	Track	*tp;
-};
-
-enum{
-	Sectorsize = 512,
-	Sect2trk = 9,
-	Trksize = Sectorsize*Sect2trk
-};
-
-struct Track
-{
-	Iosect *p[Sect2trk];
-	uchar	buf[Sect2trk][Sectorsize];
+	Iosect	**tp;
 };
 
 #define	BMOD		(1<<0)
 #define	BIMM		(1<<1)
 #define	BSTALE		(1<<2)
 
-Iosect*	getiosect(Xfs*, vlong, int);
 Iosect*	getosect(Xfs*, vlong);
 Iosect*	getsect(Xfs*, vlong);
-Iosect*	newsect(void);
-Iotrack*	getiotrack(Xfs*, vlong);
 int	canmlock(MLock*);
-int	devcheck(Xfs*);
 int	devread(Xfs*, vlong, void*, long);
 int	devwrite(Xfs*, vlong, void*, long);
 int	tread(Iotrack*);
 int	twrite(Iotrack*);
-void	freesect(Iosect*);
 void	iotrack_init(void);
 void	mlock(MLock*);
 void	purgebuf(Xfs*);
-void	purgetrack(Iotrack*);
 void	putsect(Iosect*);
 void	sync(void);
 void	unmlock(MLock*);
diff --git a/sys/src/cmd/dossrv/xfile.c b/sys/src/cmd/dossrv/xfile.c
index f734a7857..5a4c4c1f1 100644
--- a/sys/src/cmd/dossrv/xfile.c
+++ b/sys/src/cmd/dossrv/xfile.c
@@ -44,7 +44,8 @@ getxfs(char *user, char *name)
 			errno = Enofilsys;
 			return 0;
 		}
-		offset *= Sectorsize;
+		/* FIXME: should probably use devices sector size? */
+		offset *= 512;
 	}
 
 	if(readonly)
@@ -83,8 +84,6 @@ getxfs(char *user, char *name)
 			continue;
 		if(strcmp(xf->name, name) != 0 || xf->dev < 0)
 			continue;
-		if(devcheck(xf) < 0) /* look for media change */
-			continue;
 		if(offset && xf->offset != offset)
 			continue;
 		chat("incref \"%s\", dev=%d...", xf->name, xf->dev);
@@ -239,7 +238,7 @@ dosptrreloc(Xfile *f, Dosptr *dp, vlong addr, ulong offset)
 				memmove(xdp, dp, sizeof(Dosptr));
 				xdp->p = nil;
 				xdp->d = nil;
-				p->qid.path = QIDPATH(xdp);
+				p->qid.path = QIDPATH(xdp, f->xf);
 			}
 		}
 	}