[PATCH 3/3] /dev/null: add IORING_OP_URING_CMD support

[Paul Moore]

On Tue, Aug 23, 2022 at 2:52 AM Greg Kroah-Hartman
<gregkh at linuxfoundation.org> wrote:
> On Mon, Aug 22, 2022 at 05:21:19PM -0400, Paul Moore wrote:
> > This patch adds support for the io_uring command pass through, aka
> > IORING_OP_URING_CMD, to the /dev/null driver.  As with all of the
> > /dev/null functionality, the implementation is just a simple sink
> > where commands go to die, but it should be useful for developers who
> > need a simple IORING_OP_URING_CMD test device that doesn't require
> > any special hardware.
>
> Also, shouldn't you document this somewhere?
>
> At least in the code itself saying "this is here so that /dev/null works
> as a io_uring sink" or something like that?  Otherwise it just looks
> like it does nothing at all.

What about read_null() and write_null()?  I can definitely add a
comment (there is no /dev/null documentation in the kernel source tree
that I can see), but there is clearly precedence for /dev/null having
"do nothing" file_operations functions.  If nothing else, it's pretty
much in the *name*; we're adding the "uring_cmd_null()" member
function to the "null_fops" struct for the "null" device ... come on
Greg :)

-- 
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