Re: Questions and notes about send/receive

[Alex Lyakas <alex.bolshoy.btrfs@gmail.com>]

Alexander,
thanks for addressing the issues.

>> __get_cur_name_and_parent()
>> if we decided to call get_first_ref() on the send_root (due to ino <
>> sctx->send_progress), do we really need to call did_overwrite_ref()?
>> Because it will just lookup the send root again. I mean if we know
>> that this inode has been already handled, then it's not an orphan
>> anymore, so no need for this additional check. If my understanding is
>> wrong, pls give some small example?
> get_first_ref does not return the current state. It returns the
> permanent state. The result of did_overwrite_ref however depends on
> the current send progress. There is however some room for optimization
> here. In many cases, I did not think much about double tree lookups
> due to the different calls, as I wanted it to work first and later
> optimize it. One possible optimization for example would be to cache
> the results of lookups. But only for functions which return permanent
> state, e.g. get_inode_info.
So do you think my understanding is correct that if (ino <
sctx->send_progress), then both functions will return the same value?
Or perhaps: if (ino < sctx->send_progress), then no need to check
anymore the did_overwrite_ref(), because we have handled that already?
I think that the call to did_overwrite_ref() is relevant only as long
as we haven't handled this ino. After that, we are good...I think.

I'm not saying the code has be changed/optimized at this point, just
testing my understanding:)


>> struct btrfs_root_item:
>> what is the difference between existing "generation" field that you
>> mimic in generation_v2 and "ctransid"? (I know I need to study the
>> root tree code).
> Did you read the comments for btrfs_root_item and
> btrfs_read_root_item? They should answer your question.
Yes, I read the comments, but they address only "generation" and
"generation_v2", which I understand. Basically, I don't understand how
"generation" differs from ctransid (I need to dig more there).

Thanks!
Alex.



>>
>> Thank you,
>> Alex.
> Big thanks for your reviews :)
> I pushed a new version of the kernel and progs side. The branches are
> now "for-chris"