Re: Latest AIO patchset

[Daniel McNeil <daniel@osdl.org>]

Are you checking the return value of write()?

O_DIRECT has alignment requirements since it writes directly from
user-space to disk by passing the page cache.  Also the size
of the write has to be a multiple of 512 (for 2.6).
Try using posix_memalign() with pagesize as the alignment arg
to allocated the data buffer.  O_DIRECT does work on ext3.

Daniel

On Thu, 2004-02-26 at 05:30, Hayim Shaul wrote:
> On Wed, 25 Feb 2004, Benjamin LaHaise wrote:
> 
> > On Wed, Feb 25, 2004 at 08:45:29PM +0200, Hayim Shaul wrote:
> > > What exactly is the O_DIRECT flag? When I add this flag to the open func
> > > it fails.
> > > 
> > > More specificaly, this function fails
> > >   open("filename", O_RDWR | O_DIRECT | O_LARGEFILE | O_CREAT, S_IRWXU);   
> > > 
> > > but this one succeeds
> > >   open("filename", O_RDWR | O_LARGEFILE | O_CREAT, S_IRWXU);   
> > > 
> > > I'm running linux 2.6.0 with libaio 0.3.92.
> > 
> > Which filesystem?  Not all support O_DIRECT.
> > 
> 
> ext3
> I'm think it does support ext3.
> 
> Actually, I was wrong. open does succeed. It return a valid fd
> but after writing and exiting, the file is still zero size.
> 
> removing the O_DIRECT with the same prog writes quite alot to the file.
> 
> Hayim.
> 
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