From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Martin Steigerwald To: Michael Schmitz Cc: Jens Axboe , Geert Uytterhoeven , Joanne Dow , Linux/m68k , linux-block@vger.kernel.org Subject: Re: Subject: [PATCH RFC] block: fix Amiga RDB partition support for disks >= 2 TB Date: Thu, 28 Jun 2018 09:28:59 +0200 Message-ID: <1604984.EVDKEPedqG@merkaba> In-Reply-To: References: <20180627012421.80B8F24E094@nmr-admin> <3488210.nMeMqUQulA@merkaba> MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" List-ID: Hi Michael. Probably I was right with not submitting a patch myself. I=C2=B4d likely=20 would have been overwhelmed by the discussion and feedback :) Michael Schmitz - 28.06.18, 06:58: [=E2=80=A6] > >> In the interest of least surprises, we have to fix the 32 bit > >> overflow (so we can even detect that it would have happened), and > >> give the user the chance to carefully consider whether to accept > >> the new behaviour. That means refusing to make available any > >> partition that would have been affected by such overflow. > >=20 > > That is acceptable for me as I told before. Either mount or refuse > > to > > mount, but do not overflow and mount nonetheless :) > >=20 > > Mind you, I am not using my Amiga machines either at the moment. And > > I repurposed the 2 TB disk years ago. >=20 > That's fine - I understand the 'profile' image was a true binary copy > of the RDB, and placing that file at offset 0 in an image file is a > legitimate use? You actually ask me to remember about what that 'profile' image was? :) Well, in the attachment note on the bug report I wrote: "should be just=20 a binary copy", so I did not know exactly back then either. However the=20 file starts with "RDSK" and then it has "PART" headers and so on. That=20 looks pretty much like a binary copy of an RDB. I am a bit surprised by=20 its small size of 2 KiB. But I see three partitions in there. According=20 to the screenshot I also provided, the disk had three partitions. So=20 probably Media Toolbox has been intelligent enough to just copy the used=20 space of the reserved RDB area. Cause I think the reserved space must=20 have been higher than 2 KiB. However the RDB/disk geometry editing=20 screen does not display it and off hand I do not know where to look=20 inside the RDB to see how much space has been reserved. Interestingly=20 the "Total sectors" value in that Media Toolbox window also overflowed.=20 But from my memory this was just a cosmetic issue in Media Toolbox. The=20 "*.device" device drivers, the filesystems and the RDB handling code in=20 AmigaOS do their own math. That is what NSD64 / TD64 was about. https://bugzilla.kernel.org/show_bug.cgi?id=3D43511 > > I would not name the kernel option "eat_my_rdb", but use a less > > dramatizing name. > >=20 > > Maybe just: "allow_64bit_rdb" or something like that. >=20 > I don't expect to get away with that :-) Heh. :) > > How does the user come to know about this kernel option? Will you > > print its name in kernel log? >=20 > Depends on how easy we want to make it for users. If I put a BUG() > trap with the check, the resulting log section will point to a > specific line in block/partitions/amiga.c, from which the override > option will be obvious. But that might be a little too opaque for > some... kernel-parameters.txt or mentioning in the warning would also be an=20 option. Thanks, =2D-=20 Martin