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From:   Amir Goldstein <amir73il@gmail.com>
Date:   Mon, 4 Jan 2021 17:22:07 +0200
Message-ID: <CAOQ4uxgiC5Wm+QqD+vbmzkFvEqG6yvKYe_4sR7ZUVfu-=Ys9oQ@mail.gmail.com>
Subject: Re: [PATCH 3/3] overlayfs: Report writeback errors on upper
To:     Vivek Goyal <vgoyal@redhat.com>
Cc:     Matthew Wilcox <willy@infradead.org>,
        Sargun Dhillon <sargun@sargun.me>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        overlayfs <linux-unionfs@vger.kernel.org>,
        Jeff Layton <jlayton@kernel.org>,
        Miklos Szeredi <miklos@szeredi.hu>, Jan Kara <jack@suse.cz>,
        NeilBrown <neilb@suse.com>, Al Viro <viro@zeniv.linux.org.uk>,
        Christoph Hellwig <hch@lst.de>,
        Chengguang Xu <cgxu519@mykernel.net>
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> > Since Jeff's patch is minimal, I think that it should be the fix applied
> > first and proposed for stable (with adaptations for non-volatile overlay).
>
> Does stable fix has to be same as mainline fix. IOW, I think atleast in
> mainline we should first fix it the right way and then think how to fix
> it for stable. If fixes taken in mainline are not realistic for stable,
> can we push a different small fix just for stable?

We can do a lot of things.
But if we are able to create a series with minimal (and most critical) fixes
followed by other fixes, it would be easier for everyone involved.

>
> IOW, because we have to push a fix in stable, should not determine
> what should be problem solution for mainline, IMHO.
>

I find in this case there is a correlation between the simplest fix and the
most relevant fix for stable.

> The porblem I have with Jeff's fix is that its only works for volatile
> mounts. While I prefer a solution where syncfs() is fixed both for
> volatile as well as non-volatile mount and then there is less confusion.
>

I proposed a variation on Jeff's patch that covers both cases.
Sargun is going to work on it.

Thanks,
Amir.