First cut of NFS direct IO support.

- NFS direct IO completely bypasses the buffer and page caches.
  If a file is open for direct IO all caching is disabled.
- Direct IO for Directories will be addressed later.
- 2 new NFS directio related sysctls are added. One is a knob to
  disable NFS direct IO completely (direct IO is enabled by default).
  The other is to disallow mmaped IO on a file that has at least one
  O_DIRECT open (see the comment in nfs_vnops.c for more details).
  The default is to allow mmaps on a file that has O_DIRECT opens.

Submitted by:	Mohan Srinivasan mohans at yahoo-inc dot com
Obtained from:	Yahoo!

1 files changed, 10 insertions, 4 deletions

diff --git a/sys/nfsclient/nfs_nfsiod.c b/sys/nfsclient/nfs_nfsiod.c
index d1ca197..8cbee10 100644
--- a/sys/nfsclient/nfs_nfsiod.c
+++ b/sys/nfsclient/nfs_nfsiod.c
@@ -243,10 +243,16 @@ nfssvc_iod(void *instance)
 		    nmp->nm_bufqwant = 0;
 		    wakeup(&nmp->nm_bufq);
 		}
-		if (bp->b_iocmd == BIO_READ)
-		    (void) nfs_doio(bp->b_vp, bp, bp->b_rcred, NULL);
-		else
-		    (void) nfs_doio(bp->b_vp, bp, bp->b_wcred, NULL);
+		if (bp->b_flags & B_DIRECT) {
+			KASSERT((bp->b_iocmd == BIO_WRITE), ("nfscvs_iod: BIO_WRITE not set"));
+			(void)nfs_doio_directwrite(bp);
+		} else {
+			if (bp->b_iocmd == BIO_READ)
+				(void) nfs_doio(bp->b_vp, bp, bp->b_rcred, NULL);
+			else
+				(void) nfs_doio(bp->b_vp, bp, bp->b_wcred, NULL);
+		}
+
 		/*
 		 * If there are more than one iod on this mount, then defect
 		 * so that the iods can be shared out fairly between the mounts