This patch removes the VOP_BWRITE() vector.

VOP_BWRITE() was a hack which made it possible for NFS client
side to use struct buf with non-bio backing.

This patch takes a more general approach and adds a bp->b_op
vector where more methods can be added.

The success of this patch depends on bp->b_op being initialized
all relevant places for some value of "relevant" which is not
easy to determine.  For now the buffers have grown a b_magic
element which will make such issues a tiny bit easier to debug.

6 files changed, 12 insertions, 19 deletions

diff --git a/sys/kern/vfs_bio.c b/sys/kern/vfs_bio.c
index 4705903..87a17a8 100644
--- a/sys/kern/vfs_bio.c
+++ b/sys/kern/vfs_bio.c
@@ -58,6 +58,11 @@ static MALLOC_DEFINE(M_BIOBUF, "BIO buffer", "BIO buffer");
 
 struct	bio_ops bioops;		/* I/O operation notification */
 
+struct	buf_ops buf_ops_bio = {
+	"buf_ops_bio",
+	bwrite
+};
+
 struct buf *buf;		/* buffer header pool */
 struct swqueue bswlist;
 struct mtx buftimelock;		/* Interlock on setting prio and timo */
@@ -1685,6 +1690,8 @@ restart:
 		bp->b_bcount = 0;
 		bp->b_npages = 0;
 		bp->b_dirtyoff = bp->b_dirtyend = 0;
+		bp->b_magic = B_MAGIC_BIO;
+		bp->b_op = &buf_ops_bio;
 
 		LIST_INIT(&bp->b_dep);
 
@@ -2088,7 +2095,7 @@ vfs_setdirty(struct buf *bp)
  *	case it is returned with B_INVAL clear and B_CACHE set based on the
  *	backing VM.
  *
- *	getblk() also forces a VOP_BWRITE() for any B_DELWRI buffer whos
+ *	getblk() also forces a BUF_WRITE() for any B_DELWRI buffer whos
  *	B_CACHE bit is clear.
  *	
  *	What this means, basically, is that the caller should use B_CACHE to
diff --git a/sys/kern/vfs_cluster.c b/sys/kern/vfs_cluster.c
index de6b67e..8a6e045 100644
--- a/sys/kern/vfs_cluster.c
+++ b/sys/kern/vfs_cluster.c
@@ -755,6 +755,8 @@ cluster_wbuild(vp, size, start_lbn, len)
 		 */
 		TAILQ_INIT(&bp->b_cluster.cluster_head);
 		bp->b_bcount = 0;
+		bp->b_magic = tbp->b_magic;
+		bp->b_op = tbp->b_op;
 		bp->b_bufsize = 0;
 		bp->b_npages = 0;
 		if (tbp->b_wcred != NOCRED) {
diff --git a/sys/kern/vfs_default.c b/sys/kern/vfs_default.c
index d0ed3bb..cdbf668 100644
--- a/sys/kern/vfs_default.c
+++ b/sys/kern/vfs_default.c
@@ -80,7 +80,6 @@ vop_t **default_vnodeop_p;
 static struct vnodeopv_entry_desc default_vnodeop_entries[] = {
 	{ &vop_default_desc,		(vop_t *) vop_eopnotsupp },
 	{ &vop_advlock_desc,		(vop_t *) vop_einval },
-	{ &vop_bwrite_desc,		(vop_t *) vop_stdbwrite },
 	{ &vop_close_desc,		(vop_t *) vop_null },
 	{ &vop_createvobject_desc,	(vop_t *) vop_stdcreatevobject },
 	{ &vop_destroyvobject_desc,	(vop_t *) vop_stddestroyvobject },
@@ -333,13 +332,6 @@ vop_stdpoll(ap)
 	return (vn_pollrecord(ap->a_vp, ap->a_p, ap->a_events));
 }
 
-int
-vop_stdbwrite(ap)
-	struct vop_bwrite_args *ap;
-{
-	return (bwrite(ap->a_bp));
-}
-
 /*
  * Stubs to use when there is no locking to be done on the underlying object.
  * A minimal shared lock is necessary to ensure that the underlying object
diff --git a/sys/kern/vfs_export.c b/sys/kern/vfs_export.c
index f10edb2..29dec8a 100644
--- a/sys/kern/vfs_export.c
+++ b/sys/kern/vfs_export.c
@@ -748,7 +748,7 @@ vinvalbuf(vp, flags, cred, p, slpflag, slptimeo)
 			 * believe there is a slight chance that a delayed
 			 * write will occur while sleeping just above, so
 			 * check for it.  Note that vfs_bio_awrite expects
-			 * buffers to reside on a queue, while VOP_BWRITE and
+			 * buffers to reside on a queue, while BUF_WRITE and
 			 * brelse do not.
 			 */
 			if (((bp->b_flags & (B_DELWRI | B_INVAL)) == B_DELWRI) &&
diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
index f10edb2..29dec8a 100644
--- a/sys/kern/vfs_subr.c
+++ b/sys/kern/vfs_subr.c
@@ -748,7 +748,7 @@ vinvalbuf(vp, flags, cred, p, slpflag, slptimeo)
 			 * believe there is a slight chance that a delayed
 			 * write will occur while sleeping just above, so
 			 * check for it.  Note that vfs_bio_awrite expects
-			 * buffers to reside on a queue, while VOP_BWRITE and
+			 * buffers to reside on a queue, while BUF_WRITE and
 			 * brelse do not.
 			 */
 			if (((bp->b_flags & (B_DELWRI | B_INVAL)) == B_DELWRI) &&
diff --git a/sys/kern/vnode_if.src b/sys/kern/vnode_if.src
index dd22b80..2fb59d3 100644
--- a/sys/kern/vnode_if.src
+++ b/sys/kern/vnode_if.src
@@ -484,14 +484,6 @@ vop_freeblks {
 };
 
 #
-#% bwrite	vp	L L L
-#
-vop_bwrite {
-	IN struct vnode *vp;
-	IN struct buf *bp;
-};
-
-#
 #% getacl	vp	L L L
 #
 vop_getacl {