netdev - RE: [patch net-next 1/3] idr: Add new APIs to support unsigned long

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Date:   Tue, 29 Aug 2017 07:34:47 +0000
From:   Chris Mi <chrism@...lanox.com>
To:     Hannes Frederic Sowa <hannes@...essinduktion.org>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "jhs@...atatu.com" <jhs@...atatu.com>,
        "xiyou.wangcong@...il.com" <xiyou.wangcong@...il.com>,
        "jiri@...nulli.us" <jiri@...nulli.us>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "mawilcox@...rosoft.com" <mawilcox@...rosoft.com>
Subject: RE: [patch net-next 1/3] idr: Add new APIs to support unsigned long

Hi,

> -----Original Message-----
> From: Hannes Frederic Sowa [mailto:hannes@...essinduktion.org]
> Sent: Tuesday, August 29, 2017 3:14 PM
> To: Chris Mi <chrism@...lanox.com>
> Cc: netdev@...r.kernel.org; jhs@...atatu.com;
> xiyou.wangcong@...il.com; jiri@...nulli.us; davem@...emloft.net;
> mawilcox@...rosoft.com
> Subject: Re: [patch net-next 1/3] idr: Add new APIs to support unsigned long
> 
> Hello,
> 
> Chris Mi <chrism@...lanox.com> writes:
> 
> > The following new APIs are added:
> >
> > int idr_alloc_ext(struct idr *idr, void *ptr, unsigned long *index,
> >                   unsigned long start, unsigned long end, gfp_t gfp);
> > static inline void *idr_remove_ext(struct idr *idr, unsigned long id);
> > static inline void *idr_find_ext(const struct idr *idr, unsigned long
> > id); void *idr_replace_ext(struct idr *idr, void *ptr, unsigned long
> > id); void *idr_get_next_ext(struct idr *idr, unsigned long *nextid);
> >
> > Signed-off-by: Chris Mi <chrism@...lanox.com>
> > Signed-off-by: Jiri Pirko <jiri@...lanox.com>
> > ---
> >  include/linux/idr.h        | 16 ++++++++++
> >  include/linux/radix-tree.h |  3 ++
> >  lib/idr.c                  | 56 +++++++++++++++++++++++++++++++++++
> >  lib/radix-tree.c           | 73
> ++++++++++++++++++++++++++++++++++++++++++++++
> >  4 files changed, 148 insertions(+)
> >
> 
> [...]
> 
> > +int idr_alloc_ext(struct idr *idr, void *ptr, unsigned long *index,
> > +		  unsigned long start, unsigned long end, gfp_t gfp) {
> > +	void __rcu **slot;
> > +	struct radix_tree_iter iter;
> > +
> > +	if (WARN_ON_ONCE(radix_tree_is_internal_node(ptr)))
> > +		return -EINVAL;
> > +
> > +	radix_tree_iter_init(&iter, start);
> > +	slot = idr_get_free_ext(&idr->idr_rt, &iter, gfp, end);
> > +	if (IS_ERR(slot))
> > +		return PTR_ERR(slot);
> > +
> > +	radix_tree_iter_replace(&idr->idr_rt, &iter, slot, ptr);
> > +	radix_tree_iter_tag_clear(&idr->idr_rt, &iter, IDR_FREE);
> > +
> > +	if (index)
> > +		*index = iter.index;
> > +	return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(idr_alloc_ext);
> 
> Can you express idr_alloc in terms of idr_alloc_ext? Same for most of the
> other functions (it seems that signed int was used as return value to indicate
> error cases, thus it should be easy to map those).
In idr_alloc(), we have the following check:

        if (WARN_ON_ONCE(start < 0))
                return -EINVAL;

But in idr_alloc_ext(), since we are using unsigned long, we needn't such check.

In order to reuse several lines of code, I think it is not worth to express idr_alloc()
In terms of idr_alloc_ext. 

Thanks,
Chris
> 
> [...]
> 
> Thanks,
> Hannes