mav@ has found that NFS servers exporting ZFS file systems

can perform better when using a 128K read/write data size.
This patch changes NFS_MAXDATA from 64K to 128K so that
clients can use 128K for NFS mounts to allow this.
The patch also renames NFS_MAXDATA to NFS_SRVMAXIO so
that it is clear that it applies to the NFS server side
only. It also avoids a name conflict with the NFS_MAXDATA
defined in rpcsvc/nfs_prot.h, that is used for userland RPC.

Tested by:	mav
Reviewed by:	mav
MFC after:	2 weeks

4 files changed, 18 insertions, 7 deletions

diff --git a/sys/fs/nfs/nfs.h b/sys/fs/nfs/nfs.h
index 6106de9..2ee9145 100644
--- a/sys/fs/nfs/nfs.h
+++ b/sys/fs/nfs/nfs.h
@@ -159,7 +159,7 @@
 	(t).tv_sec = time.tv_sec; (t).tv_nsec = 1000 * time.tv_usec; } while (0)
 #define	NFS_SRVMAXDATA(n) 						\
 		(((n)->nd_flag & (ND_NFSV3 | ND_NFSV4)) ? 		\
-		 NFS_MAXDATA : NFS_V2MAXDATA)
+		 NFS_SRVMAXIO : NFS_V2MAXDATA)
 #define	NFS64BITSSET	0xffffffffffffffffull
 #define	NFS64BITSMINUS1	0xfffffffffffffffeull
 
diff --git a/sys/fs/nfs/nfs_commonport.c b/sys/fs/nfs/nfs_commonport.c
index 27aca26..2406d34 100644
--- a/sys/fs/nfs/nfs_commonport.c
+++ b/sys/fs/nfs/nfs_commonport.c
@@ -281,11 +281,11 @@ nfsvno_getfs(struct nfsfsinfo *sip, int isdgram)
 	if (isdgram)
 		pref = NFS_MAXDGRAMDATA;
 	else
-		pref = NFS_MAXDATA;
-	sip->fs_rtmax = NFS_MAXDATA;
+		pref = NFS_SRVMAXIO;
+	sip->fs_rtmax = NFS_SRVMAXIO;
 	sip->fs_rtpref = pref;
 	sip->fs_rtmult = NFS_FABLKSIZE;
-	sip->fs_wtmax = NFS_MAXDATA;
+	sip->fs_wtmax = NFS_SRVMAXIO;
 	sip->fs_wtpref = pref;
 	sip->fs_wtmult = NFS_FABLKSIZE;
 	sip->fs_dtpref = pref;
diff --git a/sys/fs/nfs/nfsproto.h b/sys/fs/nfs/nfsproto.h
index 768dfcb..08e7b24 100644
--- a/sys/fs/nfs/nfsproto.h
+++ b/sys/fs/nfs/nfsproto.h
@@ -54,11 +54,10 @@
 #define	NFS_VER4	4
 #define	NFS_V2MAXDATA	8192
 #define	NFS_MAXDGRAMDATA 16384
-#define	NFS_MAXDATA	NFS_MAXBSIZE
 #define	NFS_MAXPATHLEN	1024
 #define	NFS_MAXNAMLEN	255
 #define	NFS_MAXPKTHDR	404
-#define	NFS_MAXPACKET	(NFS_MAXDATA + 2048)
+#define	NFS_MAXPACKET	(NFS_SRVMAXIO + 2048)
 #define	NFS_MINPACKET	20
 #define	NFS_FABLKSIZE	512	/* Size in bytes of a block wrt fa_blocks */
 #define	NFSV4_MINORVERSION	0	/* V4 Minor version */
@@ -67,6 +66,18 @@
 #define	NFSV41_CBVERS		4	/* V4.1 CB Version */
 #define	NFSV4_SMALLSTR	50		/* Strings small enough for stack */
 
+/*
+ * This value isn't a fixed value in the RFCs.
+ * It is the maximum data size supported by NFSv3 or NFSv4 over TCP for
+ * the server.  It should be set to the I/O size preferred by ZFS or
+ * MAXBSIZE, whichever is greater.
+ * ZFS currently prefers 128K.
+ * It used to be called NFS_MAXDATA, but has been renamed to clarify that
+ * it refers to server side only and doesn't conflict with the NFS_MAXDATA
+ * defined in rpcsvc/nfs_prot.h for userland.
+ */
+#define	NFS_SRVMAXIO	(128 * 1024)
+
 /* Stat numbers for rpc returns (version 2, 3 and 4) */
 /*
  * These numbers are hard-wired in the RFCs, so they can't be changed.
diff --git a/sys/fs/nfsserver/nfs_nfsdserv.c b/sys/fs/nfsserver/nfs_nfsdserv.c
index e6e02d7..bd0c2da 100644
--- a/sys/fs/nfsserver/nfs_nfsdserv.c
+++ b/sys/fs/nfsserver/nfs_nfsdserv.c
@@ -881,7 +881,7 @@ nfsrvd_write(struct nfsrv_descript *nd, __unused int isdgram,
 			i = mbuf_len(mp);
 	}
 
-	if (retlen > NFS_MAXDATA || retlen < 0)
+	if (retlen > NFS_SRVMAXIO || retlen < 0)
 		nd->nd_repstat = EIO;
 	if (vnode_vtype(vp) != VREG && !nd->nd_repstat) {
 		if (nd->nd_flag & ND_NFSV3)