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[209.85.220.65]) by mx.google.com with SMTPS id 70sor2838989otl.86.2019.06.11.14.28.10 for (Google Transport Security); Tue, 11 Jun 2019 14:28:10 -0700 (PDT) Received-SPF: pass (google.com: domain of mayhs11saini@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=uikxw7Ut; spf=pass (google.com: domain of mayhs11saini@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=mayhs11saini@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=yfYsg0/cES0OHcG6fX5W9snm90ggOgAM9kXY3QBEhu4=; b=uikxw7UtyOptEVyjeY2qK4xy247KZZSlixb4FYF44cy5IOYuGfhYNz0auK7eAN3lSf RDykMi53c/UWnKOss3Gbf99f02SgcsLInyU9jZT7mZ9OHg9hKC6fNrTncVfEUwMvFzyT LcQoyh1B+GWH1wcVdCBdLQqRjW9xbNzL/XHVXJwKNd+h41OfOLBnxXrK/w2EGMY7Sdql Ev+iISe8afAaHYadIsKtGIEgMDX6CnpwHgbsBe+aUSzQIjTpiqosNwjLo3ub7MMP5bSh sv6W0b+fg0PHcDLs3IdJMwn13c7joqsHqAOaS3kYpN0/uUkfhOoBhUB3X+c5vOw3dtMp LbTg== X-Google-Smtp-Source: APXvYqwZE6DuGW97Wtdkbau380s5wncliqmuWNA2I8e3nRFVHn0Gyt7oiNVh7GBK4ctz/0QIVrifVcW0qHRMDnaPYKk= X-Received: by 2002:a9d:7b43:: with SMTP id f3mr18847440oto.337.1560288490020; Tue, 11 Jun 2019 14:28:10 -0700 (PDT) MIME-Version: 1.0 References: <20190611193836.2772-1-shyam.saini@amarulasolutions.com> <20190611134831.a60c11f4b691d14d04a87e29@linux-foundation.org> <6DCAE4F8-3BEC-45F2-A733-F4D15850B7F3@dilger.ca> <20190611140907.899bebb12a3d731da24a9ad1@linux-foundation.org> In-Reply-To: <20190611140907.899bebb12a3d731da24a9ad1@linux-foundation.org> From: Shyam Saini Date: Wed, 12 Jun 2019 02:57:58 +0530 Message-ID: Subject: Re: [PATCH V2] include: linux: Regularise the use of FIELD_SIZEOF macro To: Andrew Morton Cc: Andreas Dilger , Shyam Saini , Kernel Hardening , linux-kernel , Kees Cook , linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org, intel-gvt-dev@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, dri-devel , Network Development , linux-ext4 , devel@lists.orangefs.org, linux-mm , linux-sctp@vger.kernel.org, bpf , kvm@vger.kernel.org, Alexey Dobriyan Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hi Andrew, > > On Tue, 11 Jun 2019 15:00:10 -0600 Andreas Dilger wrote: > > > >> to FIELD_SIZEOF > > > > > > As Alexey has pointed out, C structs and unions don't have fields - > > > they have members. So this is an opportunity to switch everything to > > > a new member_sizeof(). > > > > > > What do people think of that and how does this impact the patch footprint? > > > > I did a check, and FIELD_SIZEOF() is used about 350x, while sizeof_field() > > is about 30x, and SIZEOF_FIELD() is only about 5x. > > Erk. Sorry, I should have grepped. > > > That said, I'm much more in favour of "sizeof_field()" or "sizeof_member()" > > than FIELD_SIZEOF(). Not only does that better match "offsetof()", with > > which it is closely related, but is also closer to the original "sizeof()". > > > > Since this is a rather trivial change, it can be split into a number of > > patches to get approval/landing via subsystem maintainers, and there is no > > huge urgency to remove the original macros until the users are gone. It > > would make sense to remove SIZEOF_FIELD() and sizeof_field() quickly so > > they don't gain more users, and the remaining FIELD_SIZEOF() users can be > > whittled away as the patches come through the maintainer trees. > > In that case I'd say let's live with FIELD_SIZEOF() and remove > sizeof_field() and SIZEOF_FIELD(). > > I'm a bit surprised that the FIELD_SIZEOF() definition ends up in > stddef.h rather than in kernel.h where such things are normally > defined. Why is that? Thanks for pointing out this, I was not aware if this is a convention. Anyway, I'll keep FIELD_SIZEOF definition in kernel.h in next version.