linux-kernel - Re: [PATCH] IB/mad: Use ID allocator routines to allocate agent number

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Message-ID: <20180530220934.GI30754@ziepe.ca>
Date:   Wed, 30 May 2018 16:09:34 -0600
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Håkon Bugge <haakon.bugge@...cle.com>
Cc:     Hans Westgaard Ry <hans.westgaard.ry@...cle.com>,
        jackm <jackm@....mellanox.co.il>,
        Doug Ledford <dledford@...hat.com>,
        Daniel Jurgens <danielj@...lanox.com>,
        Parav Pandit <parav@...lanox.com>,
        Pravin Shedge <pravin.shedge4linux@...il.com>,
        OFED mailing list <linux-rdma@...r.kernel.org>,
        linux-kernel@...r.kernel.org, Leon Romanovsky <leon@...nel.org>
Subject: Re: [PATCH] IB/mad: Use ID allocator routines to allocate agent
 number

On Wed, May 30, 2018 at 10:07:16PM +0200, Håkon Bugge wrote:
> 
> 
> > On 30 May 2018, at 17:10, Jason Gunthorpe <jgg@...pe.ca> wrote:
> > 
> > On Wed, May 30, 2018 at 02:22:56PM +0200, Hans Westgaard Ry wrote:
> > 
> >> We came up with this code snippet which we think handles both preventing
> >> immediate re-use and too big/wrapping...
> > 
> > Isn't this basically the same as idr_alloc_cyclic ?
> 
> I draw my statement back. The idr_alloc_cyclic() is the family of idr's that associates a pointer with the bit. Hence, each bit is a bit + 64b.
> 
> That's why we ended up with Hans' pseudo code.

Okay, fair enough.

Is it worth adding a ida_get_new_cyclic for this?

Jason