Re: [RFC PATCH 12/19] famfs_fuse: Plumb the GET_FMAP message/response

[Amir Goldstein <amir73il@xxxxxxxxx>]

On Mon, May 12, 2025 at 6:28 PM John Groves <John@xxxxxxxxxx> wrote:
>
> On 25/05/01 10:48PM, Joanne Koong wrote:
> > On Sun, Apr 20, 2025 at 6:34 PM John Groves <John@xxxxxxxxxx> wrote:
> > >
> > > Upon completion of a LOOKUP, if we're in famfs-mode we do a GET_FMAP to
> > > retrieve and cache up the file-to-dax map in the kernel. If this
> > > succeeds, read/write/mmap are resolved direct-to-dax with no upcalls.
> > >
> > > Signed-off-by: John Groves <john@xxxxxxxxxx>
> > > ---
...
> > > diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
> > > index 7f4b73e739cb..848c8818e6f7 100644
> > > --- a/fs/fuse/inode.c
> > > +++ b/fs/fuse/inode.c
> > > @@ -117,6 +117,9 @@ static struct inode *fuse_alloc_inode(struct super_block *sb)
> > >         if (IS_ENABLED(CONFIG_FUSE_PASSTHROUGH))
> > >                 fuse_inode_backing_set(fi, NULL);
> > >
> > > +       if (IS_ENABLED(CONFIG_FUSE_FAMFS_DAX))
> > > +               famfs_meta_set(fi, NULL);
> >
> > "fi->famfs_meta = NULL;" looks simpler here
>
> I toootally agree here, but I was following the passthrough pattern
> just above.  @miklos or @Amir, got a preference here?
>

It's not about preference, this fails build.
Even though compiler (or pre-processor whatever) should be able to skip
"fi->famfs_meta = NULL;" if CONFIG_FUSE_FAMFS_DAX is not defined
IIRC it does not. Feel free to try. Maybe I do not remember correctly.

Thanks,
Amir.