Re: [PATCH v2 05/11] ovl: lookup redirect by file handle

[Amir Goldstein <amir73il@gmail.com>]

On Fri, Apr 28, 2017 at 1:05 PM, Miklos Szeredi <miklos@szeredi.hu> wrote:
> On Fri, Apr 28, 2017 at 11:57 AM, Amir Goldstein <amir73il@gmail.com> wrote:
>> On Fri, Apr 28, 2017 at 12:37 PM, Miklos Szeredi <miklos@szeredi.hu> wrote:
>>> On Fri, Apr 28, 2017 at 10:15 AM, Amir Goldstein <amir73il@gmail.com> wrote:
>>>
>>>> Well, we could add configuration options to decide if and how to follow
>>>> and verify fh for non-dir, but:
>>>>
>>>> 1. We agreed that trying to follow fh for non-dir is a no-loose situation
>>>>     for !redirect and hot cache case and a probable win for redirect with
>>>>     cold case
>>>
>>> Okay.  That also means that redirect is not actually needed for
>>> non-dir.  Well, except for the weird case of having to reconstruct a
>>> reverse mapping after copying the layers in order to properly handle
>>> copy up of hardlinks on the lower layer.  But lets not care about that
>>> for now (or ever, probably).
>>>
>>
>> It's needed for when we can't lookup by fh:
>> - lower has NULL uuid
>> - !same_lower_sb (may be relaxed going forward)
>>
>> Heh, it's hard too keep track of it all ;-)
>
> Since this is only for constant inode, we really shouldn't need to
> care about any of the above cases.

It's also going to be needed for preserving hardlinks
(even without copying layers) for !same_fs_with_uuid case.
But that is not fixed by this series, so I can introduce
"redirect non-dir on ovl_link() and ovl_rename()"
in the next series.

>
> Lets keep things as simple as possible.
>

OK, so I'll handle lookup for all layer on samefs with uuid
and leave the rest for later.

And will store overlay.origin in any configuration, which
may be FILEID_INVALID for lowers that don't support exportfs,
so we can make use of it later.

Amir.