Index: sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vfsops.c
===================================================================
--- sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vfsops.c
+++ sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vfsops.c
@@ -1393,6 +1393,7 @@
 	vfsp->mnt_kern_flag |= MNTK_SHARED_WRITES;
 	vfsp->mnt_kern_flag |= MNTK_EXTENDED_SHARED;
 	vfsp->mnt_kern_flag |= MNTK_NO_IOPF;	/* vn_io_fault can be used */
+	vfsp->mnt_kern_flag |= MNTK_NOMSYNC;
 
 	/*
 	 * The fsid is 64 bits, composed of an 8-bit fs type, which
Index: sys/fs/devfs/devfs_vfsops.c
===================================================================
--- sys/fs/devfs/devfs_vfsops.c
+++ sys/fs/devfs/devfs_vfsops.c
@@ -130,7 +130,8 @@
 
 	MNT_ILOCK(mp);
 	mp->mnt_flag |= MNT_LOCAL;
-	mp->mnt_kern_flag |= MNTK_LOOKUP_SHARED | MNTK_EXTENDED_SHARED;
+	mp->mnt_kern_flag |= MNTK_LOOKUP_SHARED | MNTK_EXTENDED_SHARED |
+	    MNTK_NOMSYNC;
 #ifdef MAC
 	mp->mnt_flag |= MNT_MULTILABEL;
 #endif
Index: sys/fs/nullfs/null_vfsops.c
===================================================================
--- sys/fs/nullfs/null_vfsops.c
+++ sys/fs/nullfs/null_vfsops.c
@@ -205,7 +205,7 @@
 		    (MNTK_SHARED_WRITES | MNTK_LOOKUP_SHARED |
 		    MNTK_EXTENDED_SHARED);
 	}
-	mp->mnt_kern_flag |= MNTK_LOOKUP_EXCL_DOTDOT;
+	mp->mnt_kern_flag |= MNTK_LOOKUP_EXCL_DOTDOT | MNTK_NOMSYNC;
 	mp->mnt_kern_flag |= lowerrootvp->v_mount->mnt_kern_flag &
 	    (MNTK_USES_BCACHE | MNTK_NO_IOPF | MNTK_UNMAPPED_BUFS);
 	MNT_IUNLOCK(mp);
Index: sys/fs/pseudofs/pseudofs.c
===================================================================
--- sys/fs/pseudofs/pseudofs.c
+++ sys/fs/pseudofs/pseudofs.c
@@ -368,6 +368,7 @@
 
 	MNT_ILOCK(mp);
 	mp->mnt_flag |= MNT_LOCAL;
+	mp->mnt_kern_flag |= MNTK_NOMSYNC;
 	MNT_IUNLOCK(mp);
 	mp->mnt_data = pi;
 	vfs_getnewfsid(mp);
Index: sys/fs/tmpfs/tmpfs_vfsops.c
===================================================================
--- sys/fs/tmpfs/tmpfs_vfsops.c
+++ sys/fs/tmpfs/tmpfs_vfsops.c
@@ -507,7 +507,7 @@
 	MNT_ILOCK(mp);
 	mp->mnt_flag |= MNT_LOCAL;
 	mp->mnt_kern_flag |= MNTK_LOOKUP_SHARED | MNTK_EXTENDED_SHARED |
-	    MNTK_TEXT_REFS;
+	    MNTK_TEXT_REFS | MNTK_NOMSYNC;
 	MNT_IUNLOCK(mp);
 
 	mp->mnt_data = tmp;
Index: sys/kern/vfs_subr.c
===================================================================
--- sys/kern/vfs_subr.c
+++ sys/kern/vfs_subr.c
@@ -4395,6 +4395,9 @@
 
 	CTR2(KTR_VFS, "%s: mp %p", __func__, mp);
 
+	if ((mp->mnt_kern_flag & MNTK_NOMSYNC) != 0)
+		return;
+
 	MNT_VNODE_FOREACH_ACTIVE(vp, mp, mvp) {
 		obj = vp->v_object;
 		if (obj != NULL && (obj->flags & OBJ_MIGHTBEDIRTY) != 0 &&
Index: sys/sys/mount.h
===================================================================
--- sys/sys/mount.h
+++ sys/sys/mount.h
@@ -396,6 +396,7 @@
 #define MNTK_UNMOUNTF	0x00000001	/* forced unmount in progress */
 #define MNTK_ASYNC	0x00000002	/* filtered async flag */
 #define MNTK_SOFTDEP	0x00000004	/* async disabled by softdep */
+#define MNTK_NOMSYNC	0x00000008	/* don't do vfs_msync */
 #define	MNTK_DRAINING	0x00000010	/* lock draining is happening */
 #define	MNTK_REFEXPIRE	0x00000020	/* refcount expiring is happening */
 #define MNTK_EXTENDED_SHARED	0x00000040 /* Allow shared locking for more ops */