On Wed, 2020-08-19 at 07:00 -0600, Jens Axboe wrote:

On 8/18/20 1:00 PM, James Bottomley wrote:

[...]

quoted

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