From mboxrd@z Thu Jan 1 00:00:00 1970 From: Linus Torvalds Subject: Re: [RFC][PATCH] kernel.h: Add generic roundup_64() macro Date: Thu, 23 May 2019 09:51:29 -0700 Message-ID: References: <20190523100013.52a8d2a6@gandalf.local.home> <20190523112740.7167aba4@gandalf.local.home> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Return-path: In-Reply-To: <20190523112740.7167aba4-f9ZlEuEWxVcJvu8Pb33WZ0EMvNT87kid@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: nouveau-bounces-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org Sender: "Nouveau" To: Steven Rostedt Cc: Leon Romanovsky , "Darrick J. Wong" , David Airlie , nouveau-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org, LKML , dri-devel , linux-xfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Jason Gunthorpe , Doug Ledford , Ben Skeggs , Daniel Vetter , Andrew Morton , linux-rdma List-Id: linux-rdma@vger.kernel.org T24gVGh1LCBNYXkgMjMsIDIwMTkgYXQgODoyNyBBTSBTdGV2ZW4gUm9zdGVkdCA8cm9zdGVkdEBn b29kbWlzLm9yZz4gd3JvdGU6Cj4KPiBJIGhhdmVuJ3QgeWV0IHRlc3RlZCB0aGlzLCBidXQgd2hh dCBhYm91dCBzb21ldGhpbmcgbGlrZSB0aGUgZm9sbG93aW5nOgoKU28gdGhhdCBhdCBsZWFzdCBo YW5kbGVzIHRoZSBjb25zdGFudCBjYXNlIHRoYXQgdGhlIG5vcm1hbCAicm91bmR1cCgpIgpjYXNl IGFsc28gaGFuZGxlcy4KCkF0IHRoZSBzYW1lIHRpbWUsIGluIHRoZSBjYXNlIHlvdSBhcmUgdGFs a2luZyBhYm91dCwgSSByZWFsbHkgZG8Kc3VzcGVjdCB0aGF0IHdlIGhhdmUgYSAobm9uLWNvbnN0 YW50KSBwb3dlciBvZiB0d28sIGFuZCB0aGF0IHlvdQpzaG91bGQgaGF2ZSBqdXN0IHVzZWQgInJv dW5kX3VwKCkiIHdoaWNoIHdvcmtzIGZpbmUgcmVnYXJkbGVzcyBvZgpzaXplLCBhbmQgaXMgYWx3 YXlzIGVmZmljaWVudC4KCk9uIGEgc2xpZ2h0IHRhbmdlbnQuLiBNYXliZSB3ZSBzaG91bGQgaGF2 ZSBzb21ldGhpbmcgbGlrZSB0aGlzOgoKI2RlZmluZSBzaXplX2ZuKHgsIHByZWZpeCwgLi4uKSAo eyAgICAgICAgICAgICAgICAgICAgICBcCiAgICAgICAgdHlwZW9mKHgpIF9fcmV0OyAgICAgICAg ICAgICAgICAgICAgICAgICAgICAgICAgXAogICAgICAgIHN3aXRjaCAoc2l6ZW9mKHgpKSB7ICAg ICAgICAgICAgICAgICAgICAgICAgICAgIFwKICAgICAgICBjYXNlIDE6IF9fcmV0ID0gcHJlZml4 IyM4KF9fVkFfQVJHU19fKTsgYnJlYWs7ICBcCiAgICAgICAgY2FzZSAyOiBfX3JldCA9IHByZWZp eCMjMTYoX19WQV9BUkdTX18pOyBicmVhazsgXAogICAgICAgIGNhc2UgNDogX19yZXQgPSBwcmVm aXgjIzMyKF9fVkFfQVJHU19fKTsgYnJlYWs7IFwKICAgICAgICBjYXNlIDg6IF9fcmV0ID0gcHJl Zml4IyM2NChfX1ZBX0FSR1NfXyk7IGJyZWFrOyBcCiAgICAgICAgZGVmYXVsdDogX19yZXQgPSBw cmVmaXgjI2JhZChfX1ZBX0FSR1NfXyk7ICAgICAgXAogICAgICAgIH0gX19yZXQ7IH0pCgojZGVm aW5lIHR5cGVfZm4oeCwgcHJlZml4LCAuLi4pICh7ICAgICAgICAgICAgICAgICAgICAgICAgICAg ICAgXAogICAgICAgIHR5cGVvZih4KSBfX3JldDsgICAgICAgICAgICAgICAgICAgICAgICAgICAg ICAgICAgICAgICAgXAogICAgICAgIGlmICgodHlwZW9mKHgpKS0xID4gMSkgICAgICAgICAgICAg ICAgICAgICAgICAgICAgICAgICAgXAogICAgICAgICAgICAgICAgX19yZXQgPSBzaXplX2ZuKHgs IHByZWZpeCMjX3UsIF9fVkFfQVJHU19fKTsgICAgXAogICAgICAgIGVsc2UgICAgICAgICAgICAg ICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgXAogICAgICAgICAgICAgICAg X19yZXQgPSBzaXplX2ZuKHgsIHByZWZpeCMjX3MsIF9fVkFfQVJHU19fKTsgICAgXAogICAgICAg IF9fcmV0OyB9KQoKd2hpY2ggd291bGQgYWxsb3cgdHlwZWQgaW50ZWdlciBmdW5jdGlvbnMgbGlr ZSB0aGlzLiBTbyB5b3UgY291bGQgZG8Kc29tZXRoaW5nIGxpa2UKCiAgICAgI2RlZmluZSByb3Vu ZF91cCh4LCB5KSBzaXplX2ZuKHgsIHJvdW5kX3VwX3NpemUsIHgsIHkpCgphbmQgdGhlbiB5b3Ug ZGVmaW5lIGZ1bmN0aW9ucyBmb3Igcm91bmRfdXBfc2l6ZTgvMTYvMzIvNjQgKGFuZCB5b3UKaGF2 ZSB0b2kgZGVjbGFyZSAtIGJ1dCBub3QgZGVmaW5lIC0gcm91bmRfdXBfc2l6ZWJhZCgpKS4KCk9m IGNvdXJzZSwgeW91IHByb2JhYmx5IHdhbnQgdGhlIHVzdWFsICJhdCBsZWFzdCB1c2UgJ2ludCci IHNlbWFudGljcywKaW4gd2hpY2ggY2FzZSB0aGUgInR5cGUiIHNob3VsZCBiZSAiKHgpKzAiOgoK ICAgICAjZGVmaW5lIHJvdW5kX3VwKHgsIHkpIHNpemVfZm4oKHgpKzAsIHJvdW5kX3VwX3NpemUs IHgsIHkpCgogYW5kIHRoZSA4LWJpdCBhbmQgMTYtYml0IGNhc2VzIHdpbGwgbmV2ZXIgYmUgdXNl ZC4KCldlIGhhdmUgYSBsb3Qgb2YgY2FzZXMgd2hlcmUgd2UgZW5kIHVwIHVzaW5nICJ0eXBlIG92 ZXJsb2FkaW5nIiBieQpzaXplLiBUaGUgbW9zdCBleHBsaWNpdCBjYXNlIGlzIHBlcmhhcHMgImdl dF91c2VyKCkiIGFuZCAicHV0X3VzZXIoKSIsCmJ1dCB0aGlzIHdob2xlIHJvdW5kX3VwIHRoaW5n IGlzIGFub3RoZXIgZXhhbXBsZS4KCk1heWJlIHdlIG5ldmVyIHJlYWxseSBjYXJlIGFib3V0ICJj aGFyIiBhbmQgInNob3J0IiwgYW5kIGFsd2F5cyB3YW50Cmp1c3QgdGhlICJpbnQtdnMtbG9uZy12 cy1sb25nbG9uZyI/IFRoYXQgd291bGQgbWFrZSB0aGUgY2FzZXMgc2ltcGxlcgooMzIgYW5kIDY0 KS4gQW5kIG1heWJlIHdlIG5ldmVyIGNhcmUgYWJvdXQgc2lnbi4gQnV0IHdlIGNvdWxkIHRyeSB0 bwpoYXZlIHNvbWUgdW5pZmllZCBoZWxwZXIgbW9kZWwgbGlrZSB0aGUgYWJvdmUuLgoKICAgICAg ICAgICAgICAgICAgTGludXMKX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19f X19fX19fX18KTm91dmVhdSBtYWlsaW5nIGxpc3QKTm91dmVhdUBsaXN0cy5mcmVlZGVza3RvcC5v cmcKaHR0cHM6Ly9saXN0cy5mcmVlZGVza3RvcC5vcmcvbWFpbG1hbi9saXN0aW5mby9ub3V2ZWF1 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,T_DKIMWL_WL_HIGH autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CBB30C282DD for ; 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[209.85.167.50]) by smtp.gmail.com with ESMTPSA id d195sm15396lfd.10.2019.05.23.09.51.46 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 23 May 2019 09:51:46 -0700 (PDT) Received: by mail-lf1-f50.google.com with SMTP id n22so4896442lfe.12 for ; Thu, 23 May 2019 09:51:46 -0700 (PDT) X-Received: by 2002:a19:7d42:: with SMTP id y63mr41221787lfc.54.1558630305849; Thu, 23 May 2019 09:51:45 -0700 (PDT) MIME-Version: 1.0 References: <20190523100013.52a8d2a6@gandalf.local.home> <20190523112740.7167aba4@gandalf.local.home> In-Reply-To: <20190523112740.7167aba4@gandalf.local.home> From: Linus Torvalds Date: Thu, 23 May 2019 09:51:29 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [RFC][PATCH] kernel.h: Add generic roundup_64() macro To: Steven Rostedt Cc: LKML , Ben Skeggs , David Airlie , Daniel Vetter , Leon Romanovsky , Doug Ledford , Jason Gunthorpe , "Darrick J. Wong" , linux-xfs@vger.kernel.org, dri-devel , nouveau@lists.freedesktop.org, linux-rdma , Andrew Morton Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 23, 2019 at 8:27 AM Steven Rostedt wrote: > > I haven't yet tested this, but what about something like the following: So that at least handles the constant case that the normal "roundup()" case also handles. At the same time, in the case you are talking about, I really do suspect that we have a (non-constant) power of two, and that you should have just used "round_up()" which works fine regardless of size, and is always efficient. On a slight tangent.. Maybe we should have something like this: #define size_fn(x, prefix, ...) ({ \ typeof(x) __ret; \ switch (sizeof(x)) { \ case 1: __ret = prefix##8(__VA_ARGS__); break; \ case 2: __ret = prefix##16(__VA_ARGS__); break; \ case 4: __ret = prefix##32(__VA_ARGS__); break; \ case 8: __ret = prefix##64(__VA_ARGS__); break; \ default: __ret = prefix##bad(__VA_ARGS__); \ } __ret; }) #define type_fn(x, prefix, ...) ({ \ typeof(x) __ret; \ if ((typeof(x))-1 > 1) \ __ret = size_fn(x, prefix##_u, __VA_ARGS__); \ else \ __ret = size_fn(x, prefix##_s, __VA_ARGS__); \ __ret; }) which would allow typed integer functions like this. So you could do something like #define round_up(x, y) size_fn(x, round_up_size, x, y) and then you define functions for round_up_size8/16/32/64 (and you have toi declare - but not define - round_up_sizebad()). Of course, you probably want the usual "at least use 'int'" semantics, in which case the "type" should be "(x)+0": #define round_up(x, y) size_fn((x)+0, round_up_size, x, y) and the 8-bit and 16-bit cases will never be used. We have a lot of cases where we end up using "type overloading" by size. The most explicit case is perhaps "get_user()" and "put_user()", but this whole round_up thing is another example. Maybe we never really care about "char" and "short", and always want just the "int-vs-long-vs-longlong"? That would make the cases simpler (32 and 64). And maybe we never care about sign. But we could try to have some unified helper model like the above.. Linus