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Subject: Re: [PATCH] block: convert tasklets to use new tasklet_setup() API
From:   James Bottomley <James.Bottomley@HansenPartnership.com>
To:     Jens Axboe <axboe@kernel.dk>, Kees Cook <keescook@chromium.org>
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Date:   Wed, 19 Aug 2020 07:59:45 -0700
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On Wed, 2020-08-19 at 07:00 -0600, Jens Axboe wrote:
> On 8/18/20 1:00 PM, James Bottomley wrote:
[...]
> > Since both threads seem to have petered out, let me suggest in
> > kernel.h:
> > 
> > #define cast_out(ptr, container, member) \
> > 	container_of(ptr, typeof(*container), member)
> > 
> > It does what you want, the argument order is the same as
> > container_of with the only difference being you name the containing
> > structure instead of having to specify its type.
> 
> Not to incessantly bike shed on the naming, but I don't like
> cast_out, it's not very descriptive. And it has connotations of
> getting rid of something, which isn't really true.

Um, I thought it was exactly descriptive: you're casting to the outer
container.  I thought about following the C++ dynamic casting style, so
out_cast(), but that seemed a bit pejorative.  What about outer_cast()?

> FWIW, I like the from_ part of the original naming, as it has some
> clues as to what is being done here. Why not just from_container()?
> That should immediately tell people what it does without having to
> look up the implementation, even before this becomes a part of the
> accepted coding norm.

I'm not opposed to container_from() but it seems a little less
descriptive than outer_cast() but I don't really care.  I always have
to look up container_of() when I'm using it so this would just be
another macro of that type ...

James