svn commit: r317986 - stable/10/sys/fs/nfsserver

[Rick Macklem]

Author: rmacklem
Date: Mon May  8 21:58:29 2017
New Revision: 317986
URL: https://svnweb.freebsd.org/changeset/base/317986

Log:
  MFC: r317382
  Allow use of a write open stateid for reading in the NFSv4 server.
  
  The NFSv4 RFCs give a server the option of allowing the use of an open
  stateid for write access to be used for a Read operation.
  This patch enables this by default and adds a sysctl to disable it,
  for anyone who does not want this capability.
  Allowing this is particularily useful for a pNFS Data Server (DS), since
  they are not permitted to allow the use of special stateids.
  Discovered during recent testing of the pNFS server under development.

Modified:
  stable/10/sys/fs/nfsserver/nfs_nfsdstate.c
Directory Properties:
  stable/10/   (props changed)

Modified: stable/10/sys/fs/nfsserver/nfs_nfsdstate.c
==============================================================================
--- stable/10/sys/fs/nfsserver/nfs_nfsdstate.c	Mon May  8 21:49:55 2017	(r317985)
+++ stable/10/sys/fs/nfsserver/nfs_nfsdstate.c	Mon May  8 21:58:29 2017	(r317986)
@@ -80,6 +80,11 @@ SYSCTL_INT(_vfs_nfsd, OID_AUTO, writedel
     &nfsrv_writedelegifpos, 0,
     "Issue a write delegation for read opens if possible");
 
+static int	nfsrv_allowreadforwriteopen = 1;
+SYSCTL_INT(_vfs_nfsd, OID_AUTO, allowreadforwriteopen, CTLFLAG_RW,
+    &nfsrv_allowreadforwriteopen, 0,
+    "Allow Reads to be done with Write Access StateIDs");
+
 /*
  * Hash lists for nfs V4.
  */
@@ -1869,7 +1874,8 @@ tryagain:
 		       mystp->ls_flags & NFSLCK_ACCESSBITS)) ||
 		    ((new_stp->ls_flags & (NFSLCK_CHECK|NFSLCK_READACCESS)) ==
 		      (NFSLCK_CHECK | NFSLCK_READACCESS) &&
-		     !(mystp->ls_flags & NFSLCK_READACCESS)) ||
+		     !(mystp->ls_flags & NFSLCK_READACCESS) &&
+		     nfsrv_allowreadforwriteopen == 0) ||
 		    ((new_stp->ls_flags & (NFSLCK_CHECK|NFSLCK_WRITEACCESS)) ==
 		      (NFSLCK_CHECK | NFSLCK_WRITEACCESS) &&
 		     !(mystp->ls_flags & NFSLCK_WRITEACCESS))) {