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

[James Morris <jmorris@namei.org>]

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;
	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);


-- 
James Morris
<jmorris@namei.org>


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