[sheepdog] [PATCH v3 3/3] journal: new journal flag JF_DELETE_OBJ for deleting object

[Hitoshi Mitake]

At Mon, 06 May 2013 22:20:08 +0800,
Liu Yuan wrote:
> 
> On 05/06/2013 10:15 PM, Hitoshi Mitake wrote:
> > Ah, I see. But the preallocated objects would consume disk
> > space. Removing them physically would be benefitical for thin
> > provisioning, I think. How do you think?
> 
> This is just the very unusual case and even if happens, only one extra
> object is created, no?

I'm not sure about that. A number of removed objects would not be
1. The number would depend on a way of using disks of guest OSes. How
do you think?

> By the way, if we don't log the delete operation,
> the 'discard command' doesn't return to the guest. So after restarting,
> the guest will see the file is still there because inode isn't updated
> successfully yet. Then people can re-delete the file, no?

Do you mean a failure during discard command? If so, I agree with your
opinion. But failures _after_ discard commands would cause problems
when the journaling mechanism is enabled.

Thanks,
Hitoshi