Re: O_DIRECT

[Rogier Wolff]

On Tue, Jul 20, 2004 at 08:48:24PM +0200, bert hubert wrote:
> On Tue, Jul 20, 2004 at 10:27:57AM -0700, Shesha Sreenivasamurthy wrote:
> > I am having trouble with O_DIRECT. Trying to read or write from a block 
> > device partition.
> > 
> > 1. Can O_DIRECT be used on a plain block device partition say 
> > "/dev/sda11" without having a filesystem on it.
> 
> As fas as I know, yes, but be aware that O_DIRECT requires page aligned
> addresses! (an integral of 4096 on most systems).

Agreed, and I can tell you it works with raw disk devices. The code
we use is: 

  p = malloc (blocksize + PAGE_SIZE);
  buf = (void *) ((  ((long)p) + PAGE_SIZE -1 ) & ~(PAGE_SIZE-1));

		Roger. 

-- 
** R.E.Wolff@xxxxxxxxxxxx ** http://www.BitWizard.nl/ ** +31-15-2600998 **
*-- BitWizard writes Linux device drivers for any device you may have! --*
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