diff -r 7b8d88655640 -r ee687e1e0283 sys/geom/geom_vfs.c
--- a/sys/geom/geom_vfs.c	Wed May 11 19:34:11 2011 +0200
+++ b/sys/geom/geom_vfs.c	Tue May 31 00:47:16 2011 +0200
@@ -123,11 +123,26 @@
 	bip = g_alloc_bio();
 	bip->bio_cmd = bp->b_iocmd;
 	bip->bio_offset = bp->b_iooffset;
+	bip->bio_length = bp->b_bcount;
 	bip->bio_data = bp->b_data;
 	bip->bio_done = g_vfs_done;
 	bip->bio_caller2 = bp;
-	bip->bio_length = bp->b_bcount;
 	g_io_request(bip, cp);
+
+	if (bp->b_flags & B_FSYNC) {
+		bp->b_flags &= ~B_FSYNC;
+		/* Send a BIO_FLUSH to follow this request */
+		printf("fsync BIO candidate cmd: %d, offset: %ju, length: %lu\n",
+		    bp->b_iocmd, bp->b_iooffset, bp->b_bcount);
+		bip = g_alloc_bio();
+		bip->bio_cmd = BIO_FLUSH;
+		bip->bio_flags = BIO_ORDERED;
+		bip->bio_offset = bp->b_iooffset;
+		bip->bio_length = bp->b_bcount;
+		bip->bio_data = NULL;
+		bip->bio_done = g_destroy_bio;
+		g_io_request(bip, cp);
+	}
 }
 
 static void
diff -r 7b8d88655640 -r ee687e1e0283 sys/sys/buf.h
--- a/sys/sys/buf.h	Wed May 11 19:34:11 2011 +0200
+++ b/sys/sys/buf.h	Tue May 31 00:47:16 2011 +0200
@@ -211,7 +211,7 @@
 #define	B_CLUSTEROK	0x00020000	/* Pagein op, so swap() can count it. */
 #define	B_000400000	0x00040000	/* Available flag. */
 #define	B_000800000	0x00080000	/* Available flag. */
-#define	B_00100000	0x00100000	/* Available flag. */
+#define	B_FSYNC		0x00100000	/* Operation caused by fsync. */
 #define	B_DIRTY		0x00200000	/* Needs writing later (in EXT2FS). */
 #define	B_RELBUF	0x00400000	/* Release VMIO buffer. */
 #define	B_00800000	0x00800000	/* Available flag. */
diff -r 7b8d88655640 -r ee687e1e0283 sys/ufs/ffs/ffs_softdep.c
--- a/sys/ufs/ffs/ffs_softdep.c	Wed May 11 19:34:11 2011 +0200
+++ b/sys/ufs/ffs/ffs_softdep.c	Tue May 31 00:47:16 2011 +0200
@@ -709,6 +709,8 @@
 SYSINIT(sdproc, SI_SUB_KTHREAD_UPDATE, SI_ORDER_ANY, kproc_start,
     &softdep_kp);
 
+extern int ffs_fsync_flush;
+
 static void
 softdep_flush(void)
 {
@@ -5329,8 +5331,11 @@
 			FREE_LOCK(&lk);
 			if (waitfor == MNT_NOWAIT) {
 				bawrite(nbp);
-			} else if ((error = bwrite(nbp)) != 0) {
-				break;
+			} else {
+				if (ffs_fsync_flush)
+					nbp->b_flags |= B_FSYNC;
+				if ((error = bwrite(nbp)) != 0)
+					break;
 			}
 			ACQUIRE_LOCK(&lk);
 			continue;
@@ -5346,8 +5351,11 @@
 			FREE_LOCK(&lk);
 			if (waitfor == MNT_NOWAIT) {
 				bawrite(nbp);
-			} else if ((error = bwrite(nbp)) != 0) {
-				break;
+			} else {
+				if (ffs_fsync_flush)
+					nbp->b_flags |= B_FSYNC;
+				if ((error = bwrite(nbp)) != 0)
+					break;
 			}
 			ACQUIRE_LOCK(&lk);
 			continue;
@@ -5363,6 +5371,8 @@
 				if (nbp == NULL)
 					goto restart;
 				FREE_LOCK(&lk);
+				if (ffs_fsync_flush)
+					nbp->b_flags |= B_FSYNC;
 				if ((error = bwrite(nbp)) != 0) {
 					goto loop_end;
 				}
@@ -5415,8 +5425,11 @@
 			FREE_LOCK(&lk);
 			if (waitfor == MNT_NOWAIT) {
 				bawrite(nbp);
-			} else if ((error = bwrite(nbp)) != 0) {
-				break;
+			} else {
+				if (ffs_fsync_flush)
+					nbp->b_flags |= B_FSYNC;
+				if ((error = bwrite(nbp)) != 0)
+					break;
 			}
 			ACQUIRE_LOCK(&lk);
 			continue;
@@ -5436,8 +5449,11 @@
 			FREE_LOCK(&lk);
 			if (waitfor == MNT_NOWAIT) {
 				bawrite(nbp);
-			} else if ((error = bwrite(nbp)) != 0) {
-				break;
+			} else {
+				if (ffs_fsync_flush)
+					nbp->b_flags |= B_FSYNC;
+				if ((error = bwrite(nbp)) != 0)
+					break;
 			}
 			ACQUIRE_LOCK(&lk);
 			continue;
diff -r 7b8d88655640 -r ee687e1e0283 sys/ufs/ffs/ffs_vnops.c
--- a/sys/ufs/ffs/ffs_vnops.c	Wed May 11 19:34:11 2011 +0200
+++ b/sys/ufs/ffs/ffs_vnops.c	Tue May 31 00:47:16 2011 +0200
@@ -76,6 +76,7 @@
 #include <sys/mount.h>
 #include <sys/priv.h>
 #include <sys/proc.h>
+#include <sys/sysctl.h>
 #include <sys/resourcevar.h>
 #include <sys/signalvar.h>
 #include <sys/stat.h>
@@ -173,6 +174,11 @@
 	.vop_vptofh =		ffs_vptofh,
 };
 
+SYSCTL_DECL(_vfs_ffs);
+
+int ffs_fsync_flush = 1;
+SYSCTL_INT(_vfs_ffs, OID_AUTO, fsync_flush, CTLFLAG_RW, &ffs_fsync_flush, 0,
+	   "Issue BIO_FLUSH to devices on fsync");
 /*
  * Synch an open file.
  */
@@ -270,7 +276,6 @@
 		 * file or device, start the write on this buffer immediately.
 		 */
 		if (wait || (vp->v_type != VREG && vp->v_type != VBLK)) {
-
 			/*
 			 * On our final pass through, do all I/O synchronously
 			 * so that we can find out if our flush is failing
@@ -288,6 +293,8 @@
 			} else {
 				bremfree(bp);
 				splx(s);
+				if (ffs_fsync_flush)
+					bp->b_flags |= B_FSYNC;
 				if ((error = bwrite(bp)) != 0)
 					return (error);
 				s = splbio();