Issues with delalloc->real extent allocation

[Christoph Hellwig]

On Tue, Jan 18, 2011 at 08:30:00AM -0600, Geoffrey Wehrman wrote:
> Glad you were able to understand what I meant.  Something I didn't think
> of earlier though:  What happens when I try to use an 8 GB on a system
> with only 4 GB of memory?  I'm not really worried about this pathological
> case, but I do wonder what the effects will be of allocating what could
> be significant quantities of memory in .aio_write.

I think for large regions we'd be much better off to only zero the
blocks on disk, not in-memory - for example like the code in
xfs_zero_remaining_bytes does.