diff --git a/sys/fs/msdosfs/msdosfs_denode.c b/sys/fs/msdosfs/msdosfs_denode.c
--- a/sys/fs/msdosfs/msdosfs_denode.c
+++ b/sys/fs/msdosfs/msdosfs_denode.c
@@ -428,11 +428,12 @@
 	if ((boff = length & pmp->pm_crbomask) != 0) {
 		if (isadir) {
 			bn = cntobn(pmp, eofentry);
-			error = bread(pmp->pm_devvp, bn, pmp->pm_bpcluster,
+			error = breadb(pmp->pm_devvp, bntocbn(pmp, bn), bn, pmp->pm_bpcluster,
 			    NOCRED, &bp);
 		} else {
-			error = bread(DETOV(dep), de_cluster(pmp, length),
-			    pmp->pm_bpcluster, cred, &bp);
+			bn = de_cluster(pmp, length);
+			error = breadb(DETOV(dep), bntocbn(pmp, bn), bn, pmp->pm_bpcluster,
+			    cred, &bp);
 		}
 		if (error) {
 #ifdef MSDOSFS_DEBUG
@@ -503,6 +504,7 @@
 	struct msdosfsmount *pmp = dep->de_pmp;
 	struct vnode *vp = DETOV(dep);
 	struct buf *bp;
+	daddr_t bn;
 	off_t eof_clusteroff;
 	u_long count;
 	int error;
@@ -547,7 +549,8 @@
 	 * actual buffer content which might exist in the tail of the
 	 * already valid cluster.
 	 */
-	error = bread(vp, de_cluster(pmp, dep->de_FileSize), pmp->pm_bpcluster,
+	bn = de_cluster(pmp, dep->de_FileSize);
+	error = breadb(vp, bntocbn(pmp, bn), bn, pmp->pm_bpcluster,
 	    NOCRED, &bp);
 	if (error != 0)
 		goto rewind;
diff --git a/sys/fs/msdosfs/msdosfs_fat.c b/sys/fs/msdosfs/msdosfs_fat.c
--- a/sys/fs/msdosfs/msdosfs_fat.c
+++ b/sys/fs/msdosfs/msdosfs_fat.c
@@ -204,7 +204,8 @@
 		if (bn != bp_bn) {
 			if (bp)
 				brelse(bp);
-			error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp);
+			error = breadb(pmp->pm_devvp, bntocbn(pmp, bn), bn, bsize,
+			    NOCRED, &bp);
 			if (error) {
 				return (error);
 			}
@@ -509,7 +510,8 @@
 
 	byteoffset = FATOFS(pmp, cn);
 	fatblock(pmp, byteoffset, &bn, &bsize, &bo);
-	error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp);
+	error = breadb(pmp->pm_devvp, bntocbn(pmp, bn), bn, bsize,
+	    NOCRED, &bp);
 	if (error) {
 		return (error);
 	}
@@ -591,7 +593,8 @@
 	while (count > 0) {
 		byteoffset = FATOFS(pmp, start);
 		fatblock(pmp, byteoffset, &bn, &bsize, &bo);
-		error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp);
+		error = breadb(pmp->pm_devvp, bntocbn(pmp, bn), bn, bsize,
+		    NOCRED, &bp);
 		if (error) {
 			return (error);
 		}
@@ -845,7 +848,8 @@
 		if (lbn != bn) {
 			if (bp)
 				updatefats(pmp, bp, lbn);
-			error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp);
+			error = breadb(pmp->pm_devvp, bntocbn(pmp, bn), bn, bsize,
+			    NOCRED, &bp);
 			if (error) {
 				MSDOSFS_UNLOCK_MP(pmp);
 				return (error);
@@ -927,7 +931,8 @@
 			if (bp != NULL)
 				brelse(bp);
 			fatblock(pmp, byteoffset, &bn, &bsize, NULL);
-			error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp);
+			error = breadb(pmp->pm_devvp, bntocbn(pmp, bn), bn, bsize,
+			    NOCRED, &bp);
 			if (error != 0)
 				return (error);
 		}
@@ -1160,7 +1165,8 @@
 	 */
 	byteoffset = FATOFS(pmp, 1);
 	fatblock(pmp, byteoffset, &bn, &bsize, &bo);
-	error = bread(pmp->pm_devvp, bn, bsize, NOCRED, &bp);
+	error = breadb(pmp->pm_devvp, bntocbn(pmp, bn), bn, bsize,
+	    NOCRED, &bp);
 	if (error)
 		return (error);
 
diff --git a/sys/fs/msdosfs/msdosfs_lookup.c b/sys/fs/msdosfs/msdosfs_lookup.c
--- a/sys/fs/msdosfs/msdosfs_lookup.c
+++ b/sys/fs/msdosfs/msdosfs_lookup.c
@@ -253,7 +253,8 @@
 				break;
 			return (error);
 		}
-		error = bread(pmp->pm_devvp, bn, blsize, NOCRED, &bp);
+		error = breadb(pmp->pm_devvp, bntocbn(pmp, bn), bn, blsize,
+		    NOCRED, &bp);
 		if (error) {
 			return (error);
 		}
@@ -678,7 +679,8 @@
 	diroffset = ddep->de_fndoffset;
 	if (dirclust != MSDOSFSROOT)
 		diroffset &= pmp->pm_crbomask;
-	if ((error = bread(pmp->pm_devvp, bn, blsize, NOCRED, &bp)) != 0) {
+	if ((error = breadb(pmp->pm_devvp, bntocbn(pmp, bn), bn, blsize,
+		    NOCRED, &bp)) != 0) {
 		brelse(bp);
 		return error;
 	}
@@ -711,8 +713,8 @@
 				if (error)
 					return error;
 
-				error = bread(pmp->pm_devvp, bn, blsize,
-					      NOCRED, &bp);
+				error = breadb(pmp->pm_devvp, bntocbn(pmp, bn),
+				    bn, blsize, NOCRED, &bp);
 				if (error) {
 					return error;
 				}
@@ -778,7 +780,8 @@
 				return (1);	/* it's empty */
 			return (0);
 		}
-		error = bread(pmp->pm_devvp, bn, blsize, NOCRED, &bp);
+		error = breadb(pmp->pm_devvp, bntocbn(pmp, bn), bn, blsize,
+		    NOCRED, &bp);
 		if (error) {
 			return (0);
 		}
@@ -834,6 +837,7 @@
 doscheckpath(struct denode *source, struct denode *target, daddr_t *wait_scn)
 {
 	daddr_t scn;
+	daddr_t bn;
 	struct msdosfsmount *pmp;
 	struct direntry *ep;
 	struct denode *dep;
@@ -866,7 +870,8 @@
 			break;
 		}
 		scn = dep->de_StartCluster;
-		error = bread(pmp->pm_devvp, cntobn(pmp, scn),
+		bn = cntobn(pmp, scn);
+		error = breadb(pmp->pm_devvp, bntocbn(pmp, bn), bn,
 		    pmp->pm_bpcluster, NOCRED, &bp);
 		if (error != 0)
 			break;
@@ -934,7 +939,8 @@
 	    && de_blk(pmp, diroffset + blsize) > pmp->pm_rootdirsize)
 		blsize = de_bn2off(pmp, pmp->pm_rootdirsize) & pmp->pm_crbomask;
 	bn = detobn(pmp, dirclust, diroffset);
-	if ((error = bread(pmp->pm_devvp, bn, blsize, NOCRED, bpp)) != 0) {
+	if ((error = breadb(pmp->pm_devvp, bntocbn(pmp, bn), bn, blsize,
+		    NOCRED, bpp)) != 0) {
 		brelse(*bpp);
 		*bpp = NULL;
 		return (error);
@@ -991,7 +997,8 @@
 		error = pcbmap(pdep, de_cluster(pmp, offset), &bn, 0, &blsize);
 		if (error)
 			return error;
-		error = bread(pmp->pm_devvp, bn, blsize, NOCRED, &bp);
+		error = breadb(pmp->pm_devvp, bntocbn(pmp, bn), bn, blsize,
+		    NOCRED, &bp);
 		if (error) {
 			return error;
 		}
@@ -1068,7 +1075,8 @@
 					return 0;
 				return error;
 			}
-			error = bread(pmp->pm_devvp, bn, blsize, NOCRED, &bp);
+			error = breadb(pmp->pm_devvp, bntocbn(pmp, bn), bn, blsize,
+			    NOCRED, &bp);
 			if (error) {
 				return error;
 			}
diff --git a/sys/fs/msdosfs/msdosfs_vfsops.c b/sys/fs/msdosfs/msdosfs_vfsops.c
--- a/sys/fs/msdosfs/msdosfs_vfsops.c
+++ b/sys/fs/msdosfs/msdosfs_vfsops.c
@@ -457,7 +457,8 @@
 		printf("rootdir_free: dirclu=%d dirleft=%d readsize=%lu\n",
 		       dirclu, dirleft, readsize);
 #endif
-		if (bread(pmp->pm_devvp, dirclu, readsize, NOCRED, &bp) != 0) {
+		if (breadb(pmp->pm_devvp, bntocbn(pmp, dirclu), dirclu, readsize,
+			NOCRED, &bp) != 0) {
 			printf("rootdir_free: read error\n");
 			if (bp != NULL)
 				brelse(bp);
@@ -757,6 +758,12 @@
 		goto error_exit;
 	}
 
+	pmp->pm_cacheblockoffs = -pmp->pm_firstcluster % de_off2bn(pmp, PAGE_SIZE);
+#ifdef MSDOSFS_DEBUG
+	printf("logblockoffs: firstcluster=%lu bpcluster=%lu bnshift=%lu blockoffs=%lu\n",
+	    pmp->pm_firstcluster, pmp->pm_bpcluster, pmp->pm_bnshift, pmp->pm_cacheblockoffs);
+#endif
+
 	/*
 	 * Release the bootsector buffer.
 	 */
@@ -771,8 +778,10 @@
 	 */
 	if (pmp->pm_fsinfo) {
 		struct fsinfo *fp;
+		daddr_t bn;
 
-		if ((error = bread(devvp, pmp->pm_fsinfo, pmp->pm_BytesPerSec,
+		bn = pmp->pm_fsinfo;
+		if ((error = breadb(devvp, bntocbn(pmp, bn), bn, pmp->pm_BytesPerSec,
 		    NOCRED, &bp)) != 0)
 			goto error_exit;
 		fp = (struct fsinfo *)bp->b_data;
@@ -1073,6 +1082,7 @@
 {
 	struct fsinfo *fp;
 	struct buf *bp;
+	daddr_t bn;
 	int error;
 
 	MSDOSFS_LOCK_MP(pmp);
@@ -1080,7 +1090,8 @@
 		error = 0;
 		goto unlock;
 	}
-	error = bread(pmp->pm_devvp, pmp->pm_fsinfo, pmp->pm_BytesPerSec,
+	bn = pmp->pm_fsinfo;
+	error = breadb(pmp->pm_devvp, bntocbn(pmp, bn), bn, pmp->pm_BytesPerSec,
 	    NOCRED, &bp);
 	if (error != 0) {
 		goto unlock;
diff --git a/sys/fs/msdosfs/msdosfs_vnops.c b/sys/fs/msdosfs/msdosfs_vnops.c
--- a/sys/fs/msdosfs/msdosfs_vnops.c
+++ b/sys/fs/msdosfs/msdosfs_vnops.c
@@ -573,18 +573,19 @@
 				break;
 			} else if (error)
 				break;
-			error = bread(pmp->pm_devvp, lbn, blsize, NOCRED, &bp);
+			error = breadb(pmp->pm_devvp, bntocbn(pmp, lbn), lbn, blsize,
+			    NOCRED, &bp);
 		} else if (de_cn2off(pmp, rablock) >= dep->de_FileSize) {
-			error = bread(vp, lbn, blsize, NOCRED, &bp);
+			error = breadb(vp, bntocbn(pmp, lbn), lbn, blsize, NOCRED, &bp);
 		} else if ((vp->v_mount->mnt_flag & MNT_NOCLUSTERR) == 0) {
 			error = cluster_read(vp, dep->de_FileSize, lbn, blsize,
 			    NOCRED, on + uio->uio_resid, seqcount, 0, &bp);
 		} else if (seqcount > 1) {
 			rasize = blsize;
-			error = breadn(vp, lbn,
+			error = breadbn(vp, bntocbn(pmp, lbn), lbn,
 			    blsize, &rablock, &rasize, 1, NOCRED, &bp);
 		} else {
-			error = bread(vp, lbn, blsize, NOCRED, &bp);
+			error = breadb(vp, bntocbn(pmp, lbn), lbn, blsize, NOCRED, &bp);
 		}
 		if (error) {
 			brelse(bp);
@@ -758,7 +759,8 @@
 			/*
 			 * The block we need to write into exists, so read it in.
 			 */
-			error = bread(thisvp, bn, pmp->pm_bpcluster, cred, &bp);
+			error = breadb(thisvp, bntocbn(pmp, bn), bn, pmp->pm_bpcluster,
+			    cred, &bp);
 			if (error) {
 				break;
 			}
@@ -1237,10 +1239,10 @@
 		if (cn == MSDOSFSROOT) {
 			/* this should never happen */
 			panic("msdosfs_rename(): updating .. in root directory?");
-		} else
-			bn = cntobn(pmp, cn);
-		error = bread(pmp->pm_devvp, bn, pmp->pm_bpcluster,
-		    NOCRED, &bp);
+		}
+		bn = cntobn(pmp, cn);
+		error = breadb(pmp->pm_devvp, bntocbn(pmp, bn), bn,
+		    pmp->pm_bpcluster, NOCRED, &bp);
 		if (error != 0) {
 			printf("%s: block read error %d while renaming dir\n",
 			    pmp->pm_mountp->mnt_stat.f_mntonname,
@@ -1629,7 +1631,8 @@
 		error = pcbmap(dep, lbn, &bn, &cn, &blsize);
 		if (error)
 			break;
-		error = bread(pmp->pm_devvp, bn, blsize, NOCRED, &bp);
+		error = breadb(pmp->pm_devvp, bntocbn(pmp, bn), bn, blsize,
+		    NOCRED, &bp);
 		if (error) {
 			return (error);
 		}
diff --git a/sys/fs/msdosfs/msdosfsmount.h b/sys/fs/msdosfs/msdosfsmount.h
--- a/sys/fs/msdosfs/msdosfsmount.h
+++ b/sys/fs/msdosfs/msdosfsmount.h
@@ -91,6 +91,7 @@
 	u_long pm_rootdirblk;	/* block # (cluster # for FAT32) of root directory number */
 	u_long pm_rootdirsize;	/* size in blocks (not clusters) */
 	u_long pm_firstcluster;	/* block number of first cluster */
+	u_long pm_cacheblockoffs;	/* offset from physical block to buffer cache block number */
 	u_long pm_maxcluster;	/* maximum cluster number */
 	u_long pm_freeclustercount;	/* number of free clusters */
 	u_long pm_cnshift;	/* shift file offset right this amount to get a cluster number */
@@ -201,6 +202,13 @@
  */
 #define	de_bn2off(pmp, bn) \
 	((bn) << (pmp)->pm_bnshift)
+
+/*
+ * Convert offset to block number
+ */
+#define	de_off2bn(pmp, off) \
+	((off) >> (pmp)->pm_bnshift)
+
 /*
  * Map a cluster number into a filesystem relative block number.
  */
@@ -213,6 +221,12 @@
 #define	roottobn(pmp, dirofs) \
 	(de_blk((pmp), (dirofs)) + (pmp)->pm_rootdirblk)
 
+/*
+ * Calculate buffer cache block number from disk block number
+ */
+#define	bntocbn(pmp, bn) \
+	((pmp)->pm_cacheblockoffs + (bn))
+
 /*
  * Calculate block number for directory entry at cluster dirclu, offset
  * dirofs
diff --git a/sys/sys/buf.h b/sys/sys/buf.h
--- a/sys/sys/buf.h
+++ b/sys/sys/buf.h
@@ -542,12 +542,18 @@
 #define bread(vp, blkno, size, cred, bpp) \
 	    breadn_flags(vp, blkno, blkno, size, NULL, NULL, 0, cred, 0, \
 		NULL, bpp)
+#define breadb(vp, blkno, dblkno, size, cred, bpp) \
+	    breadn_flags(vp, blkno, dblkno, size, NULL, NULL, 0, cred, 0, \
+		NULL, bpp)
 #define bread_gb(vp, blkno, size, cred, gbflags, bpp) \
 	    breadn_flags(vp, blkno, blkno, size, NULL, NULL, 0, cred, \
 		gbflags, NULL, bpp)
 #define breadn(vp, blkno, size, rablkno, rabsize, cnt, cred, bpp) \
 	    breadn_flags(vp, blkno, blkno, size, rablkno, rabsize, cnt, cred, \
 		0, NULL, bpp)
+#define breadbn(vp, blkno, dblkno, size, rablkno, rabsize, cnt, cred, bpp) \
+	    breadn_flags(vp, blkno, dblkno, size, rablkno, rabsize, cnt, cred, \
+		0, NULL, bpp)
 int	breadn_flags(struct vnode *, daddr_t, daddr_t, int, daddr_t *, int *, 
 	    int, struct ucred *, int, void (*)(struct buf *), struct buf **);
 void	bdwrite(struct buf *);