From mboxrd@z Thu Jan  1 00:00:00 1970
From: Amir Goldstein <amir73il@gmail.com>
Subject: Re: [PATCH v3 5/5] ovl: consistent st_ino/d_ino
Date: Wed, 21 Jun 2017 12:05:38 +0300
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To: Miklos Szeredi <miklos@szeredi.hu>
Cc: Chandan Rajendra <chandan@linux.vnet.ibm.com>, "linux-unionfs@vger.kernel.org" <linux-unionfs@vger.kernel.org>

On Wed, Jun 21, 2017 at 11:53 AM, Miklos Szeredi <miklos@szeredi.hu> wrote:
> On Wed, Jun 21, 2017 at 10:49 AM, Amir Goldstein <amir73il@gmail.com> wrote:
>> On Wed, Jun 21, 2017 at 11:45 AM, Miklos Szeredi <miklos@szeredi.hu> wrote:
>>> On Wed, Jun 21, 2017 at 10:38 AM, Miklos Szeredi <miklos@szeredi.hu> wrote:
>>>> On Wed, Jun 21, 2017 at 10:20 AM, Miklos Szeredi <miklos@szeredi.hu> wrote:
>>>>
>>>>> Right.  The problem is when dir becomes impure due to rename between
>>>>> two getdents(2) calls.  We can't call ovl_dir_reset() because the
>>>>> offset is not zero.  We could do a "cache with head cut off" starting
>>>>> from the current offset in the dir and finish with that.  Yeah, it's
>>>>> probably less complexity than trying to intercept the actor...
>>>>
>>>> On the other hand, we'll need to accommodate the native directory
>>>> indexing (i.e. seekdir(3) hell) in the cache, which is going to add to
>>>> complexity.  Ugh.
>>>
>>> Another idea:  we are allowed to omit directory entries added after
>>> the opendir/rewinddir.  So if there was a simple way to filter out
>>> newly added entries which have origin then we are fine.
>>>
>>

Following up on your idea:
- check in ovl_iterate() if version has changed and if dir became impure
- if it did, populate od->cache, but keep the dir od->is_real
- iterate upper cache entries and call ovl_cache_update_ino()
- Then actor of real dir iterator can use the cache to ommit entries or use
  p->ino from cache if p->real_ino match real d_ino, but differs from p->ino.