linux-kernel - Re: [PATCH v2 2/2] FUSE: Retire superblock on force unmount

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Date:   Tue, 24 May 2022 16:22:24 +0200
From:   Miklos Szeredi <miklos@...redi.hu>
To:     Daniil Lunev <dlunev@...omium.org>
Cc:     Al Viro <viro@...iv.linux.org.uk>, linux-fsdevel@...r.kernel.org,
        Christoph Hellwig <hch@...radead.org>,
        fuse-devel <fuse-devel@...ts.sourceforge.net>,
        "Theodore Ts'o" <tytso@....edu>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] FUSE: Retire superblock on force unmount

On Mon, 23 May 2022 at 02:25, Daniil Lunev <dlunev@...omium.org> wrote:
>
> So, I tried this patchset with open bdi elements during force unmount
> and a random file open [1], and didn't see any major drama with
> force unmounting the node, after re-mounting, read on sysfs node
> returned "no such device", which is expected.
> With private bdi flag patch, unless bdi is unregister on force unmount
> in fuse, it will complain on name collision [2] (because the patch
> actually doesn't do much but unregisters the bdi on unmount, which
> seems to happen ok even if node is busy).

Calling bdi_unregister() might be okay, and that should fix this.  I'm
not familiar enough with that part to say for sure.

But freeing sb->s_bdi while the superblock is active looks problematic.

Thanks,
Miklos