Alex Tomas wrote:

Good day,

please review ...

thanks, Alex


basic delayed allocation in VFS:

 * block_prepare_write() can be passed special ->get_block() which
   doesn't allocate blocks, but reserve them and mark bh delayed
 * a filesystem can use mpage_da_writepages() with other ->get_block()
   which doesn't defer allocation. mpage_da_writepages() finds all
   non-allocated blocks and try to allocate them with minimal calls
   to ->get_block(), then submit IO using __mpage_writepage()


Signed-off-by: Alex Tomas <redacted>

Is this based on Christoph's work?

Christoph, or some other XFS hacker, already did generic delalloc, 
modeled on the XFS delalloc code.

	Jeff