On Tue, Jun 26, 2007 at 11:42:50AM -0400, Andreas Dilger wrote:

On Jun 26, 2007  16:15 +0530, Amit K. Arora wrote:

quoted

On Mon, Jun 25, 2007 at 03:52:39PM -0600, Andreas Dilger wrote:

quoted

In XFS one of the (many) ALLOC modes is to zero existing data on allocate.
For ext4 all this would mean is calling ext4_ext_mark_uninitialized() on
each extent.  For some workloads this would be much faster than truncate
and reallocate of all the blocks in a file.

In ext4, we already mark each extent having preallocated blocks as
uninitialized. This is done as part of following code (which is part of
patch 5/7) in ext4_ext_get_blocks() :  

What I meant is that with XFS_IOC_ALLOCSP the previously-written data
is ZEROED OUT, unlike with fallocate() which leaves previously-written
data alone and only allocates in holes.

In order to specify this for allocation, FA_FL_DEL_DATA would need to make
sense for allocations (as well as the deallocation).  This is farily easy
to do - just mark all of the existing extents as unallocated, and their
data disappears.

Ok, agreed. Will add the FA_ZERO_SPACE mode too.
Thanks!

--
Regards,
Amit Arora