[linux-cifs-client] Corrupted data on write to Windows 2003 Server

[Shirish S Pargaonkar]

linux-cifs-client-bounces+shirishp=us.ibm.com at lists.samba.org wrote on
12/08/2006 01:24:24 PM:

> When copying a file from linux to windows, I noticed corrupted data
> whenever my data size is larger than about 100-200MB.  I ran a few
> tests, using 'dd', writing a 1GB file with varying block sizes (1, 10,
> 50, 100, and 200 megs).   Each one reported a different md5 when reading
> back.  Only the 200 MB block size was successful, but it may have been a
> fluke... I need to run the test a few more times.
>
> The actual number of bytes in the destination file is correct.  But
> running 'cmp' afterwards, I discovered that the destination ends up
> being 0 padded after a certain point.  The exact spot seems to wander,
> but it appears to be around the 800-900MB mark for these files.
>
> I don't get any error messages or anything from the actual 'dd' command.
>   The only message I get is a kernel message saying: "CIFS VFS: No
> writable handles for inode", which I suppose explains it all.  But it'd
> be nice if the user commands reported some sort of failure.
>
> I don't suppose there are any mount options I can give to cifs to make
> it do more checking or retries or anything?  Or how do I actually
> prevent the "no writable handles" problem?
>
> Of course, if I use rsync, that seems to get around the problem.  But it
> seems kind dumb to have to do that for mounted filesystems. =P
>
>
>
> Linux system: Fedora Core 5
> Linux aeolus.eng.lantronix.com 2.6.18-1.2200.fc5smp #1 SMP Sat Oct 14
> 17:15:35 EDT 2006 i686 i686 i386 GNU/Linux
>
>
> Windows System: Windows Server 2003 R2 Standard w/ SP1
>
> mount options:  cifs (rw,mand)
>
> I don't think this uses samba since cifs is a kernel module, but just in
> case, my samba version is: 3.0.23c
>
> Thanks for any assistance,
> Danny
>
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Danny,

We have seen this problem and are working on it.  Sizes of the source and
destination files are same but
md5sum would report different values.  I have seen this problem with large
files like 500MB+.
I have seen some (page) ranges in destination file filled with NUL bytes.
But we have observed this problem only with copying files to Windows server
and not with Samba server.

As a work-around, you may want to use option forcedirectio during mounts.

Regards,

Shirish S. Pargaonkar
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