Re: [PATCH 1/2] fs/ceph/debugfs: make all files world-readable

[Jeff Layton]

On Mon, 2023-09-25 at 12:41 +0200, Ilya Dryomov wrote:
> On Fri, Sep 22, 2023 at 8:26 AM Max Kellermann <max.kellermann@xxxxxxxxx> wrote:
> > 
> > I'd like to be able to run metrics collector processes without special
> > privileges
> 
> Hi Max,
> 
> A word of caution about building metrics collectors based on debugfs
> output: there are no stability guarantees.  While the format won't be
> changed just for the sake of change of course, expect zero effort to
> preserve backwards compatibility.
> 
> The latency metrics in particular are sent to the MDS in binary form
> and are intended to be consumed through commands like "ceph fs top".
> debugfs stuff is there just for an occasional sneak peek (apart from
> actual debugging).
> 

FWIW, I wish we had gone with netlink for this functionality instead of
a seqfile. Lorenzo has been working with netlink for some similar
functionality with nfsd[1], and it's much nicer for this sort of thing.

[1]: https://lore.kernel.org/linux-nfs/ZQTM6l7NrsVHFoR5@lore-desk/T/#t

-- 
Jeff Layton <jlayton@xxxxxxxxxx>