linux-kernel - Re: [PATCH trivial] kernel.h: Make container_of

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Message-ID: <20190128184417.GM25120@mellanox.com>
Date:   Mon, 28 Jan 2019 18:44:24 +0000
From:   Jason Gunthorpe <jgg@...lanox.com>
To:     Christoph Hellwig <hch@...radead.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        NeilBrown <neilb@...e.com>, Jiri Kosina <trivial@...nel.org>
Subject: Re: [PATCH trivial] kernel.h: Make container_of_safe type safe

On Mon, Jan 28, 2019 at 05:42:42AM -0800, Christoph Hellwig wrote:
> On Thu, Jan 24, 2019 at 08:55:05PM +0000, Jason Gunthorpe wrote:
> > The final ternary expression is given void * and type * as arguments, so
> > the resulting type of the macro ends up being void *.
> > 
> > container_of returns a type which maches the argument, this provides type
> > safety and allows the expression to be immediately used as the target
> > type.
> > 
> > Explicitly cast ERR_CAST() to get the correct type.
> 
> I think we should just kill off container_of_safe - it has no user
> in the tree, is grossly misnamed and not really all that useful to start
> with.

I see it open coded from time to time, here someone sent a patch
open-coding it yesterday (with the same bug even):

https://patchwork.kernel.org/patch/10783535/

I noticed it didn't work right because I had a use for it..

Jason