Re: [PATCH 1/4] exportfs: add flag to indicate local file handles

[Christian Brauner]

On Mon, Dec 02, 2024 at 10:12:49AM +1100, Dave Chinner wrote:
> On Sun, Dec 01, 2024 at 02:12:25PM +0100, Christian Brauner wrote:
> > Some filesystems like kernfs and pidfs support file handles as a
> > convenience to use name_to_handle_at(2) and open_by_handle_at(2) but
> > don't want to and cannot be reliably exported. Add a flag that allows
> > them to mark their export operations accordingly.
> > 
> > Fixes: aa8188253474 ("kernfs: add exportfs operations")
> > Cc: stable <stable@xxxxxxxxxx> # >= 4.14
> > Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
> > ---
> >  fs/nfsd/export.c         | 8 +++++++-
> >  include/linux/exportfs.h | 1 +
> >  2 files changed, 8 insertions(+), 1 deletion(-)
> > 
> > diff --git a/fs/nfsd/export.c b/fs/nfsd/export.c
> > index eacafe46e3b673cb306bd3c7caabd3283a1e54b1..786551595cc1c2043e8c195c00ca72ef93c769d6 100644
> > --- a/fs/nfsd/export.c
> > +++ b/fs/nfsd/export.c
> > @@ -417,6 +417,7 @@ static struct svc_export *svc_export_lookup(struct svc_export *);
> >  static int check_export(struct path *path, int *flags, unsigned char *uuid)
> >  {
> >  	struct inode *inode = d_inode(path->dentry);
> > +	const struct export_operations *nop;
> >  
> >  	/*
> >  	 * We currently export only dirs, regular files, and (for v4
> > @@ -449,11 +450,16 @@ static int check_export(struct path *path, int *flags, unsigned char *uuid)
> >  		return -EINVAL;
> >  	}
> >  
> > -	if (!exportfs_can_decode_fh(inode->i_sb->s_export_op)) {
> > +	if (!exportfs_can_decode_fh(nop)) {
> 
> Where is nop initialised?

Yep, already fixed in tree yesterday. Thanks for catching this though!

> 
> >  		dprintk("exp_export: export of invalid fs type.\n");
> >  		return -EINVAL;
> >  	}
> >  
> > +	if (nop && nop->flags & EXPORT_OP_LOCAL_FILE_HANDLE) {
> 
> Also, please use () around & operations so we can understand that
> this is not an accidental typo. i.e:
> 
> 	if (nop && (nop->flags & EXPORT_OP_LOCAL_FILE_HANDLE)) {
> 
> clearly expresses the intent of the code, and now it is obviously
> correct at a glance.

Done.