From: Steve Dickson <SteveD@redhat.com>
Subject: [RHEL5.1][PATCH] NFS4: closes and umounts are racing. 
Date: Wed, 06 Jun 2007 15:32:41 -0400
Bugzilla: 225515
Message-Id: <46670BD9.5060909@RedHat.com>
Changelog: [nfs] closes and umounts are racing. 


The attached patch avoids an oops during a
race between that occurs between the rpciod daemon
trying to do a nfs4_close and the filesystem being unmounted.
The window is small and only happens when all of the NFS
debugging is turned (although i was never able to reproduce
the oops) but it does exist.

Note, the key word is 'avoids'. This patch does not fix the
problem, just avoids the oops...

The true fix is currently being worked on in upstream
which basically means there a patch but has very
little (i.e. none) testing. So I've decided to submit
this patch (since today is the deadline) with the idea
of updating the patch when the final solution is a bit
more baked.

The bz for this is:
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=225515


steved.

--- old/fs/nfs/inode.c	2007-01-17 17:19:48.994020288 -0500
+++ new/fs/nfs/inode.c	2007-01-17 17:20:26.570307824 -0500
@@ -914,7 +914,7 @@
 
 	server = NFS_SERVER(inode);
 	/* Update the fsid if and only if this is the root directory */
-	if (inode == inode->i_sb->s_root->d_inode
+	if ( inode->i_sb->s_root && inode == inode->i_sb->s_root->d_inode
 			&& !nfs_fsid_equal(&server->fsid, &fattr->fsid))
 		server->fsid = fattr->fsid;