When I was a kid my work table was one cluttered mess an cleaning it up

were a rather overwhelming task.  I soon learned that if you don't know
where you're going to store something, at least try to pile it next to
something slightly related in the hope that a pattern emerges.

Apply the same principle to the ffs/snapshot/softupdates code which have
leaked into specfs:  Add yet a buf-quasi-method and call it from the
only two places I can see it can make a difference and implement the
magic in ffs_softdep.c where it belongs.

It's not pretty, but at least it's one less layer violated.

sys/fs/specfs/spec_vnops.c

@@ -463,7 +463,6 @@ static int
 spec_xstrategy(struct vnode *vp, struct buf *bp)
 {
 	struct mount *mp;
-	int error;
 	struct cdevsw *dsw;
 	struct thread *td = curthread;
 	
@@ -481,25 +480,6 @@ spec_xstrategy(struct vnode *vp, struct buf *bp)
 		    PPAUSE | PCATCH | PDROP, "ioslow",
 		    td->td_ksegrp->kg_nice);
 	}
-	if (bp->b_iocmd == BIO_WRITE) {
-		if ((bp->b_flags & B_VALIDSUSPWRT) == 0 &&
-		    bp->b_vp != NULL && bp->b_vp->v_mount != NULL &&
-		    (bp->b_vp->v_mount->mnt_kern_flag & MNTK_SUSPENDED) != 0)
-			panic("spec_strategy: bad I/O");
-		bp->b_flags &= ~B_VALIDSUSPWRT;
-		if (LIST_FIRST(&bp->b_dep) != NULL)
-			buf_start(bp);
-		mp_fixme("This should require the vnode lock.");
-		if ((vp->v_vflag & VV_COPYONWRITE) &&
-		    vp->v_rdev->si_copyonwrite &&
-		    (error = (*vp->v_rdev->si_copyonwrite)(vp, bp)) != 0 &&
-		    error != EOPNOTSUPP) {
-			bp->b_io.bio_error = error;
-			bp->b_io.bio_flags |= BIO_ERROR;
-			biodone(&bp->b_io);
-			return (0);
-		}
-	}
 	/*
 	 * Collect statistics on synchronous and asynchronous read
 	 * and write counts for disks that have associated filesystems.

sys/kern/vfs_bio.c

@@ -886,10 +886,12 @@ ibwrite(struct buf * bp)
 	if (oldflags & B_ASYNC)
 		BUF_KERNPROC(bp);
 	bp->b_iooffset = dbtob(bp->b_blkno);
-	if (bp->b_vp->v_type == VCHR)
-		VOP_SPECSTRATEGY(bp->b_vp, bp);
-	else
+	if (bp->b_vp->v_type == VCHR) {
+		if (!buf_prewrite(bp->b_vp, bp))
+			VOP_SPECSTRATEGY(bp->b_vp, bp);
+	} else {
 		VOP_STRATEGY(bp->b_vp, bp);
+	}
 
 	if ((oldflags & B_ASYNC) == 0) {
 		int rtval = bufwait(bp);

sys/sys/buf.h

@@ -62,6 +62,7 @@ LIST_HEAD(workhead, worklist);
  * to each buffer.
  */
 extern struct bio_ops {
+	int	(*io_prewrite)(struct vnode *, struct buf *);
 	void	(*io_start)(struct buf *);
 	void	(*io_complete)(struct buf *);
 	void	(*io_deallocate)(struct buf *);
@@ -404,6 +405,15 @@ struct cluster_save {
 #ifdef _KERNEL
 
 
+static __inline int
+buf_prewrite(struct vnode *vp, struct buf *bp)
+{
+	if (bioops.io_start)
+		return (*bioops.io_prewrite)(vp, bp);
+	else
+		return (0);
+}
+
 static __inline void
 buf_start(struct buf *bp)
 {

sys/ufs/ffs/ffs_softdep.c

@@ -202,6 +202,7 @@ static	void add_to_worklist(struct worklist *);
 /*
  * Exported softdep operations.
  */
+static	int softdep_disk_prewrite(struct vnode *vp, struct buf *bp);
 static	void softdep_disk_io_initiation(struct buf *);
 static	void softdep_disk_write_complete(struct buf *);
 static	void softdep_deallocate_dependencies(struct buf *);
@@ -1152,6 +1153,7 @@ softdep_initialize()
 	softdep_fsync_hook = softdep_fsync;
 
 	/* initialise bioops hack */
+	bioops.io_prewrite = softdep_disk_prewrite;
 	bioops.io_start = softdep_disk_io_initiation;
 	bioops.io_complete = softdep_disk_write_complete;
 	bioops.io_deallocate = softdep_deallocate_dependencies;
@@ -3413,6 +3415,34 @@ handle_workitem_freefile(freefile)
 	WORKITEM_FREE(freefile, D_FREEFILE);
 }
 
+static int
+softdep_disk_prewrite(struct vnode *vp, struct buf *bp)
+{
+	int error;
+
+	if (bp->b_iocmd != BIO_WRITE) 
+		return (0);
+	if ((bp->b_flags & B_VALIDSUSPWRT) == 0 &&
+	    bp->b_vp != NULL && bp->b_vp->v_mount != NULL &&
+	    (vp->v_mount->mnt_kern_flag & MNTK_SUSPENDED) != 0)
+		panic("softdep_disk_prewrite: bad I/O");
+	bp->b_flags &= ~B_VALIDSUSPWRT;
+	if (LIST_FIRST(&bp->b_dep) != NULL)
+		buf_start(bp);
+	mp_fixme("This should require the vnode lock.");
+	if ((vp->v_vflag & VV_COPYONWRITE) &&
+	    vp->v_rdev->si_copyonwrite &&
+	    (error = (*vp->v_rdev->si_copyonwrite)(vp, bp)) != 0 &&
+	    error != EOPNOTSUPP) {
+		bp->b_io.bio_error = error;
+		bp->b_io.bio_flags |= BIO_ERROR;
+		biodone(&bp->b_io);
+		return (1);
+	}
+	return (0);
+}
+
+
 /*
  * Disk writes.
  * 

sys/ufs/ufs/ufs_vnops.c

@@ -1971,7 +1971,8 @@ ufs_strategy(ap)
 	vp = ip->i_devvp;
 	bp->b_dev = vp->v_rdev;
 	bp->b_iooffset = dbtob(bp->b_blkno);
-	VOP_SPECSTRATEGY(vp, bp);
+	if (!buf_prewrite(vp, bp)) 
+		VOP_SPECSTRATEGY(vp, bp);
 	return (0);
 }