Re: [PATCH 06/15] fuse: Fix mount options

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Tue, Mar 25, 2025 at 05:06:46PM +0100, Hanna Czenczek wrote:
> Since I actually took a look into how mounting with libfuse works[1], I
> now know that the FUSE mount options are not exactly standard mount
> system call options.  Specifically:
> - We should add "nosuid,nodev,noatime" because that is going to be
>   translated into the respective MS_ mount flags; and those flags make
>   sense for us.
> - We can set rw/ro to make the mount writable or not.  It makes sense to
>   set this flag to produce a better error message for read-only exports
>   (EROFS instead of EACCES).
>   This changes behavior as can be seen in iotest 308: It is no longer
>   possible to modify metadata of read-only exports.
> 
> In addition, in the comment, we can note that the FUSE mount() system
> call actually expects some more parameters that we can omit because
> fusermount3 (i.e. libfuse) will figure them out by itself:
> - fd: /dev/fuse fd
> - rootmode: Inode mode of the root node
> - user_id/group_id: Mounter's UID/GID
> 
> [1] It invokes fusermount3, an SUID libfuse helper program, which parses
>     and processes some mount options before actually invoking the
>     mount() system call.
> 
> Signed-off-by: Hanna Czenczek <hreitz@redhat.com>
> ---
>  block/export/fuse.c        | 14 +++++++++++---
>  tests/qemu-iotests/308     |  4 ++--
>  tests/qemu-iotests/308.out |  3 ++-
>  3 files changed, 15 insertions(+), 6 deletions(-)

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

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