Re: files of size larger than fs size

[Max <relf@unn.ac.ru>]

Bryan,

I'm not experienced in filesystems. But I've derived the testcase program from some buggy application that occasionally created huge files on my fs. That was not so easy to reproduce since not every sequence of seeks/reads/writes results in a huge file. But finally I got it 100% reproducible.

So I would appriciate if somebody make any good from that testcase code.

Different filesizes look strange to me. What I have so far:

JFS:    281474976706576  =  2**48 - 4080
XFS:  72057594037923856  =  2**56 - 4080
EXT3:     1099511627784  =  2**40 + 8

Thanks,
Max

P.S. direct link to the testcase program: http://bugzilla.kernel.org/attachment.cgi?id=4729

Bryan Henderson wrote:
>>But anyway it's interesting why the resulting sparse 
>>files have different size on different fs?
> 
> 
> That looks like a bug.  Assuming you didn't see any seeks or writes fail, 
> the file size on all filesystems should be 2^56 + 4.  I suspect this is 
> beyond the maximum file size allowed by the filesystem in some cases, so 
> the write isn't happening, which means you should get a failure return 
> code.
> 
> In the results you showed, the filesize ends up being a little less than 
> 2^48, which is not a place that you wrote ever.
> 
> --
> Bryan Henderson                          IBM Almaden Research Center
> San Jose CA                              Filesystems
> 
>