Date: Thu, 30 Mar 2017 01:14:06 +0300 From: Toomas Soome <tsoome@me.com> To: Warner Losh <imp@bsdimp.com> Cc: Poul-Henning Kamp <phk@phk.freebsd.dk>, John Baldwin <jhb@freebsd.org>, Ngie Cooper <ngie@freebsd.org>, src-committers <src-committers@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>, "svn-src-head@freebsd.org" <svn-src-head@freebsd.org> Subject: Re: svn commit: r316132 - head/sys/boot/i386/boot2 Message-ID: <A4EC7D97-9C7C-4771-A044-ADA643FA0A6A@me.com> In-Reply-To: <CANCZdfr2eRRMQy-uwXDhxT0z88CBKwtkg2e_jFBOg%2Bs_L8=FYg@mail.gmail.com> References: <201703290930.v2T9U3x9087583@repo.freebsd.org> <7448826.asYms2TLO2@ralph.baldwin.cx> <46812.1490823365@critter.freebsd.dk> <CANCZdfr2eRRMQy-uwXDhxT0z88CBKwtkg2e_jFBOg%2Bs_L8=FYg@mail.gmail.com>
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> On 30. m=C3=A4rts 2017, at 0:55, Warner Losh <imp@bsdimp.com> wrote: >=20 > On Wed, Mar 29, 2017 at 3:36 PM, Poul-Henning Kamp = <phk@phk.freebsd.dk> wrote: >> -------- >> In message <7448826.asYms2TLO2@ralph.baldwin.cx>, John Baldwin = writes: >>> On Wednesday, March 29, 2017 09:30:03 AM Ngie Cooper wrote: >>=20 >>>> Log: >>>> Parameterize out 7680 (15 * 512) as BOOT2SIZE, similar to = sys/boot/i386/zfsboot/... >>>>=20 >>>> This is being done to make it easier to change in the future--this = action might be >>>> needed sooner rather than later because of gcc 6.3.0 bailing, = stating that there >>>> is negative free space left (deficit) in the boot2 bootloader. >>>>=20 >>>> MFC after: 2 months >>>> Sponsored by: Dell EMC Isilon >>>=20 >>> This can't be changed. It's baked into the BSD disklabel format. >>=20 >> No it is not, it is baked into FFS, and for UFS2 0, 8, 64 and 256K = works. >=20 > Technically, this is correct. Practically, I'm not sure we can ever > really change it. There are too many tools, scripts, etc that just > know it's 8k, even though most UFS2 systems start 64k into the volume. > UFS1 systems are still around, and there the limit is a hard limit. > And if we grow it, we run the risk of corrupting data beyond the 8k > area we've traditionally used for this. >=20 > So the constants are easy enough to change and it seems like it might > be OK. However, doing it in a safe, anti-foot-shooting way will be the > real elbow grease should someone seriously contemplate the change, > especially since the foot-shooting involved has the potential for > filesystem corruption... >=20 > But gcc 6.3 likely just needs a little TLC experimenting with its > different code generation flags... >=20 > Warner >=20 One thing is - for now we know the boot2 has not changed and we do not = really expect it to change in large scale anyhow. Second thing, yes the build process needs to be tested etc, and if = needed we can issue statement which compiler we support or not. And finally - if the space limit is really-really on the way and no = other way, then the alternate is to use freebsd-boot partition - nothing = new about it. rgds, toomas
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