svn commit: r246187 - stable/9/sys/fs/nfsserver

[Xin LI]

Author: delphij
Date: Fri Feb  1 00:32:01 2013
New Revision: 246187
URL: http://svnweb.freebsd.org/changeset/base/246187

Log:
  MFC r245613:
  
  Make it possible to force async at server side on new NFS server, similar
  to the old one's nfs.nfsrv.async.
  
  Please note that by enabling this option (default is disabled), the system
  could potentionally have silent data corruption if the server crashes
  before write is committed to non-volatile storage, as the client side have
  no way to tell if the data is already written.
  
  Submitted by:	rmacklem

Modified:
  stable/9/sys/fs/nfsserver/nfs_nfsdserv.c
Directory Properties:
  stable/9/sys/   (props changed)
  stable/9/sys/fs/   (props changed)

Modified: stable/9/sys/fs/nfsserver/nfs_nfsdserv.c
==============================================================================
--- stable/9/sys/fs/nfsserver/nfs_nfsdserv.c	Thu Jan 31 22:43:38 2013	(r246186)
+++ stable/9/sys/fs/nfsserver/nfs_nfsdserv.c	Fri Feb  1 00:32:01 2013	(r246187)
@@ -55,6 +55,11 @@ extern int nfs_rootfhset;
 extern int nfsrv_enable_crossmntpt;
 #endif	/* !APPLEKEXT */
 
+static int	nfs_async = 0;
+SYSCTL_DECL(_vfs_nfsd);
+SYSCTL_INT(_vfs_nfsd, OID_AUTO, async, CTLFLAG_RW, &nfs_async, 0,
+    "Tell client that writes were synced even though they were not");
+
 /*
  * This list defines the GSS mechanisms supported.
  * (Don't ask me how you get these strings from the RFC stuff like
@@ -912,7 +917,13 @@ nfsrvd_write(struct nfsrv_descript *nd, 
 			goto out;
 		NFSM_BUILD(tl, u_int32_t *, 4 * NFSX_UNSIGNED);
 		*tl++ = txdr_unsigned(retlen);
-		if (stable == NFSWRITE_UNSTABLE)
+		/*
+		 * If nfs_async is set, then pretend the write was FILESYNC.
+		 * Warning: Doing this violates RFC1813 and runs a risk
+		 * of data written by a client being lost when the server
+		 * crashes/reboots.
+		 */
+		if (stable == NFSWRITE_UNSTABLE && nfs_async == 0)
 			*tl++ = txdr_unsigned(stable);
 		else
 			*tl++ = txdr_unsigned(NFSWRITE_FILESYNC);