Re: [PATCH 1/5] fallocate() implementation in i86, x86_64 and powerpc

Mingming Cao
2007-05-09T17:07:34Z

On Wed, 2007-05-09 at 21:31 +0530, Amit K. Arora wrote:
> I have the updated patches ready which take care of Andrew's comments.
> Will run some tests and post them soon.
>
> But, before submitting these patches, I think it will be better to finalize
> on certain things which might be worth some discussion here:
>
> 1) Should the file size change when preallocation is done beyond EOF ?
> - Andreas and Chris Wedgwood are in favor of not changing the
> file size in this case. I also tend to agree with them. Does anyone
> has an argument in favor of changing the filesize ?
> If not, I will remove the code which changes the filesize, before I
> resubmit the concerned ext4 patch.
>

If we chose not to update the file size beyong EOF, then for filesystem
without fallocate() support (ext2,3 currently), posix_fallocate() will
follow the hard way(zero-out) to do preallocation. Then we will get
different behavior on filesystems w/o fallocate() support. It make sense
to be consistent, IMO.

My point of view, preallocation is just a efficient way to allocating
blocks for files without zero-out, other than this, the new behavior
should be consistent with the old way: file size update,mtime/ctime,
ENOSPC etc.

Mingming