Re: fuse mount failure when type contains '.'

Thanks for your response.

But, hold up. I demonstrated a(n apparently) valid use case, shared
links where other people have hit this problem over the years, and
proposed an implementation accommodating it (which I'm using in a
patched/forked version of `util-linux`, currently). Since the
requested change would allow for subtypes to include `.` in addition
to [a-zA-Z0-9_]* I don't see a theoretical restriction (even if the
implementation as proposed is unacceptable as-is based on style or
unforeseen edge cases). Users want to use `.` in subtypes, it's
backward-compatible, it doesn't violate any documentation/guarantee
(as far as I can tell) and a working solution has been provided.
What's the rationale for prohibiting this use case?

Thank you.

On Thu, Aug 22, 2024, 07:09 Miklos Szeredi <[email protected]> wrote:
>
> On Mon, 5 Aug 2024 at 11:49, Karel Zak <[email protected]> wrote:
> >
> >
> >  Hi John,
> >
> > On Thu, Aug 01, 2024 at 11:16:30AM GMT, John Rinehart wrote:
> > > `util-linux` seems to fail to handle a use case that users like me seem to
> > > be hitting with some frequency. The issue is around
> > > https://github.com/util-linux/util-linux/blob/86b6684e7a215a0608bd130371bd7b3faae67aca/libmount/src/context.c#L2115-L2121
> > > and seems rooted in the fact that `util-linux` operates on `type` where
> > > type is always of the form <a>.<b> but where <b> is apparently assumed to
> > > not contain Unicode U+002E (ASCII 2E): '.' ("dotless"). I say it "appears
> > > to assume" this since the logic which appears to remove the subtype does so
> > > by using `strrchr`, which addresses only the last period in the `helper`
> > > string. If the `subtype`, itself, has a U+002E character then this won't
> > > remove the subtype.
> > >
> > > As an example, if `helper` looks like
> > > `path/name.type./subtype/path/with/a.period` then the modified `helper`
> > > after `strrchr` will look like `path/name.type./subtype/path/with/a`
> > > instead of the apparently-intended `path/name.type`.
> >
> > the convention for filesystem names is (was):
> >
> >     <type>[.<subtype>]
> >
> > For example, for the "mount" helper, it is:
> >
> >     /path/mount.<type>[.<subtype>]
> >
> > I believe it is acceptable for the "path" to contain dots (or any
> > other characters). The important thing is the last segment of the path
> > (e.g. /mount.<type>[.<subtype>]). We should not be concerned with
> > anything else besides the last segment.
> >
> > It is strange to assume that <subtype> can also contain path-like
> > segments and dots. It seems like someone may want to use <subtype> to
> > encode additional information ...
> >
> > Miklos (CC:), what is your opinion? Is it correct to assume that <subtype>
> > is whatever?
>
> We can assume that subtype is just [a-zA-Z0-9_]*, I think.
>
> Thanks,
> Miklos
>
>
>
> >
> >     Karel
> >
> >
> > > This crops up for users like me because  I use NixOS which is a store-based
> > > Linux operating system using paths like:
> > > ```
> > > $ readlink -f $(which s3fs)
> > >
> > > /nix/store/xwbx0fbg65ml2qjl86p9p2w58kghqn8r-s3fs-fuse-1.94/bin/s3fs
> > > ```
> > > (So, paths like `/nix/store/<hash>-<name>-<version>/bin/<cmd>`). `version`
> > > is usually a dot-delimited string like `1.23`.
> > >
> > > I've generated a patch which seems to ameliorate this behavior. It's
> > > attached (sorry if attachments are not the way to go with this mailing
> > > list, specifically, or mailing lists, generally - this is my first time
> > > submitting a patch to a mailing list). The logic is simple, but it
> > > basically iterates through all possible substrings according to the number
> > > of U+002E characters in the `type` string. It's a more generic form of the
> > > logic already present, but it's a little heavy-handed. Happy with any and
> > > all changes which preserve the apparently-corrected behavior.
> > >
> > > Please let me know if I should make any changes or if a change like this
> > > won't be accepted for some reason or if I'm misunderstanding the
> > > problem/solution.
> > >
> > > Thank you!
> > >
> > > Cf.
> > > 1. https://discourse.nixos.org/t/how-to-setup-s3fs-mount/6283/5
> > > 2. https://github.com/NixOS/nixpkgs/issues/46529#issuecomment-655536831
> > >
> > > -- John Rinehart
> >
> >
> >
> > --
> >  Karel Zak  <[email protected]>
> >  http://karelzak.blogspot.com
> >