[linux-cifs-client] Broken client-side caching - fixed by means of PATCH for 2.6 kern el (included)

[Vince Negri (ASL)]

Thanks to the co-operation of a number of people, notably Dave Stahl
and Esteban Salazar, I now have updated patches against recent 2.6.x
kernels that fix the issues both I and Dave were reporting. Dave in
particular has done a lot of real-world testing on multiple machines.

To recap, the original issue was that when using the cifs VFS module
on the client, an operation that required a read of the whole directory
(such as "ls -l *") would insert updated file size/time information
into the client-side inode without invalidating any cached data pages
related to that file. 

Dave Stahl came up with a reproducible test case:

--quote--
1) Export a share from a WinXP box - no patches, no domain membership. 
2) mount share on 2.6.10 linux system to /mnt/winxp  - mount.cifs version is
1.5 
3) On the linux box, type cat /mnt/winxp/testdir/*.txt >testfile1
(obviously assumes some text files exist) 
4) On windows box, modify one or more files in the exported testdir. 
5) cat /mnt/winxp/testdir/*.txt >testfile2 
6) testfile1 and testfile2 will be identical (incorrectly) 
7) mount -o remount /mnt/winxp (or wait some undefined (to me, anyway)
period of time greater than 15 minutes) 
8) cat /mnt/winxp/testdir/*.txt >testfile2 
9) testfile1 and testfile3 will now differ (correctly).
--end quote--


The problem existed both in the 2.6.11 kernel code, and the current
backport to 2.4 (which is where I first ran into the issue myself.)


 <<cifs_invalidate_inode_patch_2.6.10.diff>>  
<<cifs_invalidate_inode_patch_2.6.11.diff>> 

As well as inviting Steve to review the patch (he may well have a more
elegant way to achieve what the patch does) I'd appreciate any reports
from people running it even if they aren't having problems, as a way
of detecting regressions.

Regards,


Vince



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