Re: [PATCH v3 5/5] ovl: consistent st_ino/d_ino

Chandan Rajendra
2017-08-03T07:18:18Z

On Friday, July 28, 2017 2:55:56 PM IST Amir Goldstein wrote:
> On Thu, Jul 27, 2017 at 11:00 PM, Miklos Szeredi <miklos@szeredi.hu> wrote:
> > On Wed, Jun 21, 2017 at 11:48 AM, Miklos Szeredi <miklos@szeredi.hu> wrote:
> >> On Wed, Jun 21, 2017 at 11:36 AM, Amir Goldstein <amir73il@gmail.com> wrote:
> >>> On Wed, Jun 21, 2017 at 12:20 PM, Miklos Szeredi <miklos@szeredi.hu> wrote:
> >>>> On Wed, Jun 21, 2017 at 11:05 AM, Amir Goldstein <amir73il@gmail.com> wrote:
> >>>
> >>>>>
> >>>>> 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.
> >>>>
> >>>> For non-merge dirs we can have a simplified cache just containing the
> >>>> entries with origin, recreated when the version changes or updated in
> >>>> rename, whichever is simpler. A non-merge dir will never become a
> >>>> merge one, so we can keep the handling separate.
> >>>>
> >>>
> >>> And use this cache to ommit/fix entries with actor?
> >>
> >> Right. I think fixing up is better, because to correctly omit entries
> >> we'd need separate lists for each open directory. For fixing up we
> >> can use a common one, just like for the merged dir.
> >
> > And back to this, I pushed a branch named "ovl-d_ino" to my vfs tree.
> >
> > Please test.
> >
>
> I can confirm that xfstest overlay/017, the only test I have for
> constant d_ino,
> passes. Although it does not cover all cases handled by the patch set
> (e.g. d_ino of merge parent).
>
> Chandan,
>
> Can you take on the task of improving test coverage for constant d_ino?
> You should create a new xfstest and cover more cases of constant d_ino
> and possibly also a test for clearing of impure xattr.
>
> When the basic test is in place, I will be able to point at more corner cases
> to cover.
>
> Also need to prepare a test to verify constant d_ino for non samefs
> for after this patch is integrated with your work.
> overlay/017 is a good starting point, but can't use the standard _scratch_mount
> helpers that mount samefs overlay.

Hi Amir,

In ovl_calc_d_ino() we have the following code snippet,

if ((p->name[0] == '.' && p->len == 1) ||
ovl_test_flag(OVL_IMPURE, d_inode(rdd->dentry)))
return true;

At this point in the function, the directory which is being iterated must have
an entry in upperdir. W.r.t the case of processing "." directory entry, I
think we can limit it to be applicable only when rdd->dentry is either a merge
dir or an impure dir. For a directory which is both pure and non-merge, we can
return the value of p->ino as is.

The second part of the "if" condition takes care of the 'impure dir' part. So
the first part of the "if" condition can be written as,

(p->name[0] == '.' && p->len == 1 && !OVL_TYPE_MERGE(ovl_path_type(rdd->dentry)))

--
chandan