Re: Q about pagecache data never written to disk

[Andrey Savochkin <saw@saw.sw.com.sg>]

On Sun, Sep 05, 2004 at 02:00:40PM -0700, Andrew Morton wrote:
> Andrey Savochkin <saw@saw.sw.com.sg> wrote:
> > On Sun, Sep 05, 2004 at 03:52:33AM -0700, Andrew Morton wrote:
> > > That would be a retrograde step - it would be nice to move in the other
> > > direction: perform disk allocation at writeback time rather than at write()
> > > time, even for regular write() data.  To do that we (probably) need space
> > > reservation APIs.  And yes, we perhaps could reserve space in the
> > > filesystem when that page is first written to.
> > > 
> > > But then what would we do if there's no space?  SIGBUS?  SIGSEGV? 
> > > Inappropriate.  SIGENOSPC?
> > 
> > Should the space be allocated on close()?
> 
> What effect are you trying to achieve?

Sending a signal while there is still a process...

> > Who will get the signal if nobody accesses the file anymore?
> 
> Nobody.  That's the point.  Plus there _is_ no signal defined for this. 
> Neither in Linux nor in POSIX.
> 
> > I'm also thinking about various shell scripts with redirects to files...
> 
> ?  I doubt that they're writing files via MAP_SHARED.

I was deliberating on your idea about delayed allocation for regular write()s
also...