Re: [PATCH 4/4] ovl: alllow remote upper

On Mon, Mar 16, 2020 at 09:02:32PM +0200, Amir Goldstein wrote:
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Could you please make sure that the code in ovl-strict-upper branch
works as expected for virtio as upper fs?

Hi Amir,

Right now it fails becuase virtiofs doesn't seem to support tmpfile yet.

overlayfs: upper fs does not support tmpfile
overlayfs: upper fs missing required features.

Will have to check what's required to support it.

I also wanted to run either overlay xfstests or unionmount-testsuite. But
none of these seem to give me enough flexibility where I can specify
that overlayfs needs to be mounted on top of virtiofs.

I feel that atleast for unionmount-testsuite, there should be an
option where we can simply give a target directory and tests run
on that directory and user mounts that directory as needed.

Need to see how patches look.
Don't want too much configuration complexity, but I agree that some
flexibly is needed.
Maybe the provided target directory should be the upper/work basedir?

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I have rebased it on latest overlayfs-next merge into current master.

I would very much prefer that the code merged to v5.7-rc1 will be more
restrictive than the current overlayfs-next.

In general I agree that if we want to not support some configuration
with remote upper, this is the time to introduce that restriction
otherwise we will later run into backward compatibility issue.

Having said that, tmpfile support for upper sounds like a nice to
have feature. Not sure why to make it mandatory.

Agreed, I just went automatic on all the warnings.
tmpfile should not be a requirement for upper.
Could you please verify that if dropping the tmpfile strict check,
virtio can be used as upper.

I dropped tmpfile strict check and now I can mount overlayfs using
virtiofs as upper. Tried few basic file operations and these are
working.

Vivek