2003-11-26 19:45:09

by Shantanu Goel

[permalink] [raw]
Subject: [NFS PATCH] 2.6.0-test10 Invalidate cached inode attributes after rename

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:



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2003-12-04 00:42:25

by Paul Smith

[permalink] [raw]
Subject: Re: [NFS PATCH] 2.6.0-test10 Invalidate cached inode attributes after rename

%% "Shantanu Goel" <[email protected]> writes:

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

Interesting: I see this exact same message when taring up the contents
of a ClearCase view (in 2.4.20-x)... even though I'm 100% positive that
no one but me is touching those files. Is this scenario relevant to a
kernel that old as well?

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Paul D. Smith <[email protected]> HASMAT--HA Software Mthds & Tools
"Please remain calm...I may be mad, but I am a professional." --Mad Scientist
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