RE: pread/pwrite bug on linux?

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On Tue, 2009-03-03 at 10:47 -0800, Qiuyang Wu wrote:
> Hi Jeff,
> 
> Attached the sample program. Should be able to compile as-is.
> 
> Let me know your findings or need additional info.
> 
> Thanks,
> Qiuyang

Are you compiling that on a 64-bit system? Otherwise you should note
that off_t is a signed 32-bit integer. You'd need to compile your test
program with -D_FILE_OFFSET_BITS=64 in order to make those pwrite()
calls work correctly past the 2Gb mark.
You also have potential 32/64-bit issues with the stat_file() routine.

Trond

> -----Original Message-----
> From: Jeff Moyer [mailto:jmoyer@xxxxxxxxxx]
> Sent: Tuesday, March 03, 2009 10:10 AM
> To: Qiuyang Wu
> Cc: linux-nfs@xxxxxxxxxxxxxxx; linux-fsdevel@xxxxxxxxxxxxxxx
> Subject: Re: pread/pwrite bug on linux?
> 
> Qiuyang Wu <Qiuyang.Wu@xxxxxxxxxxxx> writes:
> 
> > Hi All,
> >
> > Are there any known bugs with pread/pwrite on RHEL Linux when the disk
> > partition is close to full?
> >
> > Reduced a complex application fatal down to a simple program just
> > opens a regular file and performs 1M sequential pwrite() of size 8KB
> > blocks; at every 100th write, does a pread() to load the very first
> > 8KB block and validate its content still matching what was originally
> > written.
> 
> Could you attach your test program, please?
> 
> > BEHAVIOR: pwrite() works for many iterations, then pread() suddenly
> > returns data of the requested size but filled with 0's, and strerror
> > shows errno="No such file or directory", condition
> >       if(size_to_read != pread(fd, buf, size_to_read, ...)) ...
> > is not triggered and application has to check errno immediately after
> > every call to pread.
> 
> The value of errno is undefined if the pread call did not return -1.
> 
> Cheers,
> Jeff

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