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From: Rick Macklem <rmacklem@FreeBSD.org>
Date: Sun, 29 May 2011 20:55:23 +0000 (UTC)
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Subject: svn commit: r222464 - head/sys/nfsclient
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Author: rmacklem
Date: Sun May 29 20:55:23 2011
New Revision: 222464
URL: http://svn.freebsd.org/changeset/base/222464

Log:
  Add a check for MNTK_UNMOUNTF at the beginning of nfs_sync()
  in the old NFS client so that a forced dismount doesn't
  get stuck in the VFS_SYNC() call that happens before
  VFS_UNMOUNT() in dounmount(). Analagous to r222329 for the new NFS client.
  An additional change is needed before forced dismounts will work.
  
  PR:		kern/157365
  MFC after:	2 weeks

Modified:
  head/sys/nfsclient/nfs_vfsops.c

Modified: head/sys/nfsclient/nfs_vfsops.c
==============================================================================
--- head/sys/nfsclient/nfs_vfsops.c	Sun May 29 20:46:53 2011	(r222463)
+++ head/sys/nfsclient/nfs_vfsops.c	Sun May 29 20:55:23 2011	(r222464)
@@ -1408,10 +1408,20 @@ nfs_sync(struct mount *mp, int waitfor)
 
 	td = curthread;
 
+	MNT_ILOCK(mp);
+	/*
+	 * If a forced dismount is in progress, return from here so that
+	 * the umount(2) syscall doesn't get stuck in VFS_SYNC() before
+	 * calling VFS_UNMOUNT().
+	 */
+	if ((mp->mnt_kern_flag & MNTK_UNMOUNTF) != 0) {
+		MNT_IUNLOCK(mp);
+		return (EBADF);
+	}
+
 	/*
 	 * Force stale buffer cache information to be flushed.
 	 */
-	MNT_ILOCK(mp);
 loop:
 	MNT_VNODE_FOREACH(vp, mp, mvp) {
 		VI_LOCK(vp);