Re: [PATCH 3/5] exportfs: make ->encode_fh() a mandatory method for NFS export

[Amir Goldstein <amir73il@xxxxxxxxx>]

On Thu, Oct 19, 2023 at 5:40 PM Jan Kara <jack@xxxxxxx> wrote:
>
> On Wed 18-10-23 12:59:58, Amir Goldstein wrote:
> > export_operations ->encode_fh() no longer has a default implementation to
> > encode FILEID_INO32_GEN* file handles.
> >
> > Rename the default helper for encoding FILEID_INO32_GEN* file handles to
> > generic_encode_ino32_fh() and convert the filesystems that used the
> > default implementation to use the generic helper explicitly.
> >
> > This is a step towards allowing filesystems to encode non-decodeable file
> > handles for fanotify without having to implement any export_operations.
> >
> > Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
>
> Just one typo cleanup. Also I agree we need a "nop" variant of
> generic_encode_ino32_fh() or move this to fs/libfs.c like e.g.
> generic_fh_to_dentry().
>

I did this:

 /*
  * Generic helpers for filesystems.
  */
+#ifdef CONFIG_EXPORTFS
+int generic_encode_ino32_fh(struct inode *inode, __u32 *fh, int *max_len,
+                           struct inode *parent);
+#else
+#define generic_encode_ino32_fh NULL
+#endif

I like it better than moving to fs/libfs.c, because if CONFIG_EXPORTFS
is not defined, no code should be calling generic_encode_ino32_fh().

It might be a good idea to define exportfs_can_*() helpers to false
when CONFIG_EXPORTFS is not defined, but at least for fanotify,
this is not relevant because fanotify selects EXPORTFS.

> > diff --git a/Documentation/filesystems/porting.rst b/Documentation/filesystems/porting.rst
> > index 4d05b9862451..197ef78a5014 100644
> > --- a/Documentation/filesystems/porting.rst
> > +++ b/Documentation/filesystems/porting.rst
> > @@ -1045,3 +1045,12 @@ filesystem type is now moved to a later point when the devices are closed:
> >  As this is a VFS level change it has no practical consequences for filesystems
> >  other than that all of them must use one of the provided kill_litter_super(),
> >  kill_anon_super(), or kill_block_super() helpers.
> > +
> > +---
> > +
> > +**mandatory**
> > +
> > +export_operations ->encode_fh() no longer has a default implementation to
> > +encode FILEID_INO32_GEN* file handles.
> > +Fillesystems that used the default implementation may use the generic helper
>    ^^^ Filesystems
>

Thanks!
Amir.