Re: How can I force a read to hit the disk?

["Jörn Engel" <joern@wohnheim.fh-wedel.de>]

On Fri, 5 September 2003 14:49:15 -0400, Alan Stern wrote:
> On Fri, 5 Sep 2003, Andreas Dilger wrote:
> 
> > If you open the file with O_DIRECT, it should read/write directly on the
> > disk, and it will also invalidate any existing cache for the read/written
> > area.
> 
> Unfortunately that's not a good solution for me.  The file has already 
> been opened without O_DIRECT, and O_DIRECT wouldn't be appropriate because 
> most of the time I do want I/O to go through the cache.  It's just on a 
> few rare occasions that I need direct access to the disk.
> 
> Maybe simply opening a new struct file using O_DIRECT, for purposes of 
> the verification, while keeping the old struct file around for other uses 
> later, will work?  That would be awkward though -- and there's no 
> guarantee that the original filename would still exist.  It would be a lot 
> nicer to do everything using the original file reference.

Maybe these help you here:
man 3 fdopen
man 3 fileno

No filename needed for the second open.

Jörn

-- 
"Error protection by error detection and correction."
-- from a university class