Re: [RFC PATCH v2 3/6] fuse: initial infrastructure for FUSE_LOOKUP_HANDLE support

[Miklos Szeredi]

On Tue, 16 Dec 2025 at 12:33, Luis Henriques <luis@xxxxxxxxxx> wrote:
>
> On Tue, Dec 16 2025, Miklos Szeredi wrote:
>
> > On Fri, 12 Dec 2025 at 19:12, Luis Henriques <luis@xxxxxxxxxx> wrote:
> >>
> >> This patch adds the initial infrastructure to implement the LOOKUP_HANDLE
> >> operation.  It simply defines the new operation and the extra fuse_init_out
> >> field to set the maximum handle size.
> >
> > Since we are introducing a new op, I'd consider switching to
> > fuse_statx for the attributes.
>
> So, just to clarify: you're suggesting that the maximum handle size should
> instead be set using statx.  Which means that the first time the client
> (kernel) needs to use this value it would emit a FUSE_STATX, and cache
> that value for future use.  IIUC, this would also require a new mask
> (STATX_MAX_HANDLE_SZ) to be added.  Did I got it right?

No, using statx as the output of LOOKUP_HANDLE is independent from the
other suggestion.

> What would be the advantages of using statx?  Keeping the unused bytes in
> struct fuse_init_out untouched?

Using fuse_statx instead of fuse_attr would allow btime (and other
attributes added to statx in the future) to be initialized on lookup.

Thanks,
Miklos