linux-kernel - Re: [PATCH] kernfs: attach uuid for every kernfs and report it in fsid

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Message-ID: <CABWYdi3s35QZXSeb95XUeLyOkM66po603-ows1n3np=Lt4g1nw@mail.gmail.com>
Date:   Mon, 31 Jul 2023 11:49:24 -0700
From:   Ivan Babrou <ivan@...udflare.com>
To:     Jan Kara <jack@...e.cz>
Cc:     Amir Goldstein <amir73il@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-fsdevel@...r.kernel.org, kernel-team@...udflare.com,
        linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
        Tejun Heo <tj@...nel.org>, Hugh Dickins <hughd@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Hellwig <hch@....de>,
        Zefan Li <lizefan.x@...edance.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Christian Brauner <brauner@...nel.org>
Subject: Re: [PATCH] kernfs: attach uuid for every kernfs and report it in fsid

On Mon, Jul 31, 2023 at 6:46 AM Jan Kara <jack@...e.cz> wrote:
> > I agree. I think it was a good decision.
> > I have some followup questions though.
> >
> > I guess your use case cares about the creation of cgroups?
> > as long as the only way to create a cgroup is via vfs
> > vfs_mkdir() -> ... cgroup_mkdir()
> > fsnotify_mkdir() will be called.
> > Is that a correct statement?
> > Because if not, then explicit fsnotify_mkdir() calls may be needed
> > similar to tracefs/debugfs.
> >
> > I don't think that the statement holds for dieing cgroups,
> > so explicit fsnotify_rmdir() are almost certainly needed to make
> > inotify/fanotify monitoring on cgroups complete.
>
> Yeah, as Ivan writes, we should already have all that is needed to
> generate CREATE and DELETE events for the cgroup filesystem. In theory
> inotify or fanotify for inodes could be already used with cgroupfs now.
> Thus I have no objection to providing fsid for it so that filesystem-wide
> notifications can be used for it as well. Feel free to add:
>
> Acked-by: Jan Kara <jack@...e.cz>
>
> to your patch.

Thank you, I just sent v2:

* https://lore.kernel.org/linux-fsdevel/20230731184731.64568-1-ivan@cloudflare.com/