From mboxrd@z Thu Jan 1 00:00:00 1970 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 Content-Type: text/plain; charset="UTF-8" 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 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.