[Pvfs2-users] corrupted output

[Sam Lang]

Hi Chris,

This looks like it might be an issue with writev in the kernel.  Are you running RHEL5 by chance?
-sam

On Dec 15, 2010, at 8:39 AM, Chris Poultney wrote:

> Sure - it's attached. I ran exactly the code I posted earlier.
> 
> -crispy
> 
> 
> On 12/14/2010 07:25 PM, Sam Lang wrote:
>> 
>> Hi Chris,
>> 
>> Would you be willing to run your test with strace and post the output?  That will help us figure out what read/write system calls PVFS is getting from your app.
>> 
>> Thanks,
>> -sam
>> 
>> On Dec 14, 2010, at 4:29 PM, Chris Poultney wrote:
>> 
>>> All-
>>> 
>>> I'm having a problem where files written to a PVFS volume overwrite the beginning of the file after some output has already been generated, as if lseek() had been called mid-write. The overwriting behavior does not show up on a regular ext3 volume. Sample code is attached. I'd like to know if anyone can duplicate this behavior, because it looks like a bug.
>>> 
>>> Essentially what happens is this: given a large (1024+ character) string, I write some portion of the string using a C++ ostream, then write another line:
>>> 
>>> out<<  st.substr(0, N);
>>> out<<  "done";
>>> 
>>> If N<  1024, everything is fine. If N>= 1024, "done" is written at the beginning of the file, overwriting what was there before.
>>> 
>>> I'd love to figure this out!
>>> 
>>> Cheers,
>>> -crispy
>>> 
>>> <pvfstest.cpp>_______________________________________________
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>>> Pvfs2-users at beowulf-underground.org
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>> 
> <strace.out>