Re: [PATCH] Add flags option to get xattr method paired to __vfs_getxattr

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Fri, Aug 16, 2019 at 05:20:36AM +1000, James Morris wrote:
> On Tue, 13 Aug 2019, Greg Kroah-Hartman wrote:
> 
> > On Mon, Aug 12, 2019 at 12:32:49PM -0700, Mark Salyzyn wrote:
> > > --- a/include/linux/xattr.h
> > > +++ b/include/linux/xattr.h
> > > @@ -30,10 +30,10 @@ struct xattr_handler {
> > >  	const char *prefix;
> > >  	int flags;      /* fs private flags */
> > >  	bool (*list)(struct dentry *dentry);
> > > -	int (*get)(const struct xattr_handler *, struct dentry *dentry,
> > > +	int (*get)(const struct xattr_handler *handler, struct dentry *dentry,
> > >  		   struct inode *inode, const char *name, void *buffer,
> > > -		   size_t size);
> > > -	int (*set)(const struct xattr_handler *, struct dentry *dentry,
> > > +		   size_t size, int flags);
> > > +	int (*set)(const struct xattr_handler *handler, struct dentry *dentry,
> > >  		   struct inode *inode, const char *name, const void *buffer,
> > >  		   size_t size, int flags);
> > 
> > Wow, 7 arguments.  Isn't there some nice rule of thumb that says once
> > you get more then 5, a function becomes impossible to understand?
> > 
> > Surely this could be a structure passed in here somehow, that way when
> > you add the 8th argument in the future, you don't have to change
> > everything yet again?  :)
> > 
> > I don't have anything concrete to offer as a replacement fix for this,
> > but to me this just feels really wrong...
> 
> How about something like:
> 
> struct xattr_gs_args {
> 	struct dentry *dentry;
> 	struct inode *inode;

As he said in a later message, dentry and inode is redundant, only 1 is
needed (dentry I think?)

> 	const char *name;
> 	const void *buffer;
> 	size_t size;
> 	int flags;
> };
> 
> int (*get)(const struct xattr_handler *handler, struct xattr_gs_args *args);
> int (*set)(const struct xattr_handler *handler, struct xattr_gs_args *args);

But yes, that would be much much better.

thanks,

greg k-h