linux-kernel - Re: [PATCH] radix-tree: must check __radix_tree

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Message-ID: <1504636475.15310.60.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Tue, 05 Sep 2017 11:34:35 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Matthew Wilcox <willy@...radead.org>,
        Matthew Wilcox <mawilcox@...rosoft.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        netdev <netdev@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] radix-tree: must check __radix_tree_preload() return
 value

On Tue, 2017-09-05 at 11:07 -0700, Linus Torvalds wrote:
> On Tue, Sep 5, 2017 at 10:59 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> > @@ -2104,7 +2104,10 @@ EXPORT_SYMBOL(radix_tree_tagged);
> >   */
> >  void idr_preload(gfp_t gfp_mask)
> >  {
> > -       __radix_tree_preload(gfp_mask, IDR_PRELOAD_SIZE);
> > +       int ret = __radix_tree_preload(gfp_mask, IDR_PRELOAD_SIZE);
> > +
> > +       if (ret)
> > +               preempt_disable();
> >  }
> >  EXPORT_SYMBOL(idr_preload);
> 
> Is there a reason for the "ret" variable that is entirely mis-named,
> since it's never actually used as a return value?
> 
> (Sure. it's the return value of a function, but that is entirely
> useless and pointless information, and adds no value. We should name
> variables by the data they contain or how they are used, not by "it
> was the return value of a function").
> 
> In other words, why isn't this just
> 
>         if (__radix_tree_preload(..))
>                 preempt_disable();
> 
> which is shorter and clearer and not confusing?


...

> Same issue, but this time strengthened by an additional "why doesn't
> this just use that idr_preload function then?" question..
> 

Yep, I will send a v2, thanks.