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Wed, 19 Aug 2020 06:17:24 -0700 (PDT) Subject: Re: [PATCH] block: convert tasklets to use new tasklet_setup() API To: Greg KH Cc: James Bottomley , Kees Cook , ulf.hansson@linaro.org, linux-atm-general@lists.sourceforge.net, manohar.vanga@gmail.com, airlied@linux.ie, Allen Pais , linux-hyperv@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, anton.ivanov@cambridgegreys.com, devel@driverdev.osuosl.org, linux-s390@vger.kernel.org, linux1394-devel@lists.sourceforge.net, maximlevitsky@gmail.com, richard@nod.at, deller@gmx.de, jassisinghbrar@gmail.com, 3chas3@gmail.com, intel-gfx@lists.freedesktop.org, kuba@kernel.org, mporter@kernel.crashing.org, jdike@addtoit.com, oakad@yahoo.com, s.hauer@pengutronix.de, linux-input@vger.kernel.org, linux-um@lists.infradead.org, linux-block@vger.kernel.org, broonie@kernel.org, openipmi-developer@lists.sourceforge.net, mitch@sfgoth.com, linux-arm-kernel@lists.infradead.org, linux-parisc@vger.kernel.org, netdev@vger.kernel.org, martyn@welchs.me.uk, dmitry.torokhov@gmail.com, linux-mmc@vger.kernel.org, sre@kernel.org, linux-spi@vger.kernel.org, alex.bou9@gmail.com, Allen Pais , stefanr@s5r6.in-berlin.de, daniel@ffwll.ch, linux-ntb@googlegroups.com, Romain Perier , shawnguo@kernel.org, davem@davemloft.net References: <20200817091617.28119-1-allen.cryptic@gmail.com> <20200817091617.28119-2-allen.cryptic@gmail.com> <202008171228.29E6B3BB@keescook> <161b75f1-4e88-dcdf-42e8-b22504d7525c@kernel.dk> <202008171246.80287CDCA@keescook> <1597780833.3978.3.camel@HansenPartnership.com> <20200819131158.GA2591006@kroah.com> From: Jens Axboe Message-ID: <4f5a225d-460f-978f-e3cf-3f505140a515@kernel.dk> Date: Wed, 19 Aug 2020 07:17:19 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200819131158.GA2591006@kroah.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-hyperv-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-hyperv@vger.kernel.org On 8/19/20 6:11 AM, Greg KH wrote: > On Wed, Aug 19, 2020 at 07:00:53AM -0600, Jens Axboe wrote: >> 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 >>>>>>>>> >>>>>>>>> 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. > > I agree, if we want to bike shed, I don't like this color either. > >> 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. > > Why are people hating on the well-known and used container_of()? > > If you really hate to type the type and want a new macro, what about > 'container_from()'? (noun/verb is nicer to sort symbols by...) > > But really, why is this even needed? container_from() or from_container(), either works just fine for me in terms of naming. I think people are hating on it because it makes for _really_ long lines, and it's arguably cleaner/simpler to just pass in the pointer type instead. Then you end up with lines like this: struct request_queue *q = container_of(work, struct request_queue, requeue_work.work); But I'm not the one that started this addition of from_tasklet(), my objection was adding a private macro for something that should be generic functionality. Hence I think we either need to provide that, or tell the from_tasklet() folks that they should just use container_of(). -- Jens Axboe