[Fwd: [NFS PATCH] 2.6.0-test10 Invalidate cached inode attributes after rename]

["Shantanu Goel" <Shantanu.Goel@lehman.com>]

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I initially mailed this to the NFS mailing list on sourceforge.net but 
it doesn't seem to have made it through.

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From: "Shantanu Goel" <Shantanu.Goel@lehman.com>
To: nfs@lists.sourceforge.net
Subject: [NFS PATCH] 2.6.0-test10 Invalidate cached inode attributes after rename
Date: Wed, 26 Nov 2003 14:41:45 -0500
Message-ID: <3FC501F9.1050306@lehman.com>

Hi Trond et al,

The following one line patch invalidates the attributes of the 
underlying inode when a file is renamed.  Some filesystems update ctime 
upon rename().  One such filesystem is ext3, and a comment in the 
relevant code there indicates this is true with other Unix filesystems 
as well.
The following problem was observed on Fedora Core 1 running a stock 
kernel.org 2.6.0-test10.
The server is running Solaris 2.8 but I have verified the same issue 
exists with a server running Linix 2.4.22.  These operations a done via 
a Perl script.

1. Check out a CVS repository into an NFS mounted directory.
2. Move files from CVS working directory into another directory in the 
same filesystem.
3. Tar up the resultant directory.
4. Tar prints lots of "file changed after we read it" messages.

Tar obtains ctime via stat() before reading the file and compares it to 
the ctime obtained via fstat() after having read the file.  The two 
differ because the intervening open() forces an attribute refresh due to 
CTO consistency at which time ctime is updated.  Forcing a cache 
invalidation during rename() eliminates this particular scenario.

Thanks,
Shantanu

--- 2.6.0-test10/fs/nfs/dir.c.~1~    2003-10-17 17:43:11.000000000 -0400
+++ 2.6.0-test10/fs/nfs/dir.c    2003-11-26 12:42:27.000000000 -0500
@@ -1257,6 +1257,7 @@
 
     nfs_zap_caches(new_dir);
     nfs_zap_caches(old_dir);
+    NFS_CACHEINV(old_inode);
     error = NFS_PROTO(old_dir)->rename(old_dir, &old_dentry->d_name,
                        new_dir, &new_dentry->d_name);
 out: