On 8/18/20 1:00 PM, James Bottomley wrote: > On Mon, 2020-08-17 at 13:02 -0700, Jens Axboe wrote: >> On 8/17/20 12:48 PM, Kees Cook wrote: >>> On Mon, Aug 17, 2020 at 12:44:34PM -0700, Jens Axboe wrote: >>>> On 8/17/20 12:29 PM, Kees Cook wrote: >>>>> On Mon, Aug 17, 2020 at 06:56:47AM -0700, Jens Axboe wrote: >>>>>> On 8/17/20 2:15 AM, Allen Pais wrote: >>>>>>> From: Allen Pais <allen.lkml@xxxxxxxxx> >>>>>>> >>>>>>> In preparation for unconditionally passing the >>>>>>> struct tasklet_struct pointer to all tasklet >>>>>>> callbacks, switch to using the new tasklet_setup() >>>>>>> and from_tasklet() to pass the tasklet pointer explicitly. >>>>>> >>>>>> Who came up with the idea to add a macro 'from_tasklet' that >>>>>> is just container_of? container_of in the code would be >>>>>> _much_ more readable, and not leave anyone guessing wtf >>>>>> from_tasklet is doing. >>>>>> >>>>>> I'd fix that up now before everything else goes in... >>>>> >>>>> As I mentioned in the other thread, I think this makes things >>>>> much more readable. It's the same thing that the timer_struct >>>>> conversion did (added a container_of wrapper) to avoid the >>>>> ever-repeating use of typeof(), long lines, etc. >>>> >>>> But then it should use a generic name, instead of each sub-system >>>> using some random name that makes people look up exactly what it >>>> does. I'm not huge fan of the container_of() redundancy, but >>>> adding private variants of this doesn't seem like the best way >>>> forward. Let's have a generic helper that does this, and use it >>>> everywhere. >>> >>> I'm open to suggestions, but as things stand, these kinds of >>> treewide >> >> On naming? Implementation is just as it stands, from_tasklet() is >> totally generic which is why I objected to it. from_member()? Not >> great with naming... But I can see this going further and then we'll >> suddenly have tons of these. It's not good for readability. > > 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. 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. -- Jens Axboe
