2 files changed, 17 insertions, 3 deletions

diff --git a/sys/fs/devfs/devfs_vnops.c b/sys/fs/devfs/devfs_vnops.c
index 2ffaa1389d9fe..b75caa6af0a79 100644
--- a/sys/fs/devfs/devfs_vnops.c
+++ b/sys/fs/devfs/devfs_vnops.c
@@ -1435,3 +1435,16 @@ static struct vop_vector devfs_specops = {
 	.vop_symlink =		VOP_PANIC,
 	.vop_write =		VOP_PANIC,
 };
+
+/*
+ * Our calling convention to the device drivers used to be that we passed
+ * vnode.h IO_* flags to read()/write(), but we're moving to fcntl.h O_ 
+ * flags instead since that's what open(), close() and ioctl() takes and
+ * we don't really want vnode.h in device drivers.
+ * We solved the source compatibility by redefining some vnode flags to
+ * be the same as the fcntl ones and by sending down the bitwise OR of
+ * the respective fcntl/vnode flags.  These CTASSERTS make sure nobody
+ * pulls the rug out under this.
+ */
+CTASSERT(O_NONBLOCK == IO_NDELAY);
+CTASSERT(O_FSYNC == IO_SYNC);
diff --git a/sys/sys/vnode.h b/sys/sys/vnode.h
index 31156f69d7642..94873e78de24b 100644
--- a/sys/sys/vnode.h
+++ b/sys/sys/vnode.h
@@ -267,15 +267,16 @@ struct vattr {
 /*
  * Flags for ioflag. (high 16 bits used to ask for read-ahead and
  * help with write clustering)
+ * NB: IO_NDELAY and IO_DIRECT are linked to fcntl.h
  */
 #define	IO_UNIT		0x0001		/* do I/O as atomic unit */
 #define	IO_APPEND	0x0002		/* append write to end */
-#define	IO_SYNC		0x0004		/* do I/O synchronously */
+#define	IO_NDELAY	0x0004		/* FNDELAY flag set in file table */
 #define	IO_NODELOCKED	0x0008		/* underlying node already locked */
-#define	IO_NDELAY	0x0010		/* FNDELAY flag set in file table */
+#define	IO_ASYNC	0x0010		/* bawrite rather then bdwrite */
 #define	IO_VMIO		0x0020		/* data already in VMIO space */
 #define	IO_INVAL	0x0040		/* invalidate after I/O */
-#define	IO_ASYNC	0x0080		/* bawrite rather then bdwrite */
+#define	IO_SYNC		0x0080		/* do I/O synchronously */
 #define	IO_DIRECT	0x0100		/* attempt to bypass buffer cache */
 #define	IO_EXT		0x0400		/* operate on external attributes */
 #define	IO_NORMAL	0x0800		/* operate on regular data */