Re: Partitions: Amiga RDB partition on 2 TB disk way too big, whileOK in AmigaOS 4.1

[jdow]

On 2012/06/17 14:20, Martin Steigerwald wrote:
> Am Sonntag, 17. Juni 2012 schrieb jdow:
> > On 2012/06/17 09:36, Geert Uytterhoeven wrote:
> > > On Sun, Jun 17, 2012 at 2:58 PM, Martin Steigerwald
> <Martin@xxxxxxxxxxxx> wrote:
> > > > Am Sonntag, 17. Juni 2012 schrieb jdow:
> > > > | JXFS 64 bit file system
> > > > |
> > > > | With AmigaOS 4.x a new file system has been introduced called
> > > > | JXFS. It is a totally new 64 bit file system that supports
> > > > | partitions up to 16 TB in size. It is a modern journalling file
> > > > | system, which means that it reduces data loss if data writes to
> > > > | the disk are interrupted. It is the fastest and most reliable
> > > > | file system ever created for AmigaOS.
> > > >
> > > > http://www.amigaos.net/content/1/features
> > > >
> > > > Well I asked AmigaOS 4 developers about this issue as well. Lets see
> > > > what they say about 2 TB limits.
> > >
> > > 16 TB = 2 TB * 8. Perhaps they increased the block size from 512 to
> > > 4096?
> > >
> > > block/partitions/amiga.c reads the block size from
> > > RigidDiskBlock.rdb_BlockBytes,
> > > but after conversion to 512-byte blocks, all further calculations are
> > > done on "int", so it will overflow for disks larger than 2 TiB.
> > >
> > > Note that in your profile-binary.img, the field is 0x200, i.e. 512
> > > bytes per block,
> > > so I'll have to get a deeper look into your RDB first...
> […]
> > Note that the work I did on the Linux RDB code eons ago took full
> > cognizance of the physical and virtual block sizes.
> […]
> > I've asked Martin for a digital copy of his RDBs and what he thinks the
> > partition(s) should look like. I should also be told whether the disk
> > is supposed to be solely Amiga OSs or not. I gather it's not.
>
> Its all in the bug report. profile-binary.img should be it.
>
> Its small so I attach it.
>
> Meanwhile I try to get the currently supported maximum disk size out from
> the OS 4 developers. Maybe JXFS is playing tricks that other filesystems do
> not play or simply has a different implementation.
>
> Thanks,

I've sent Jens a proposed fix changing these lines in amiga.c.
===8<--- was
        struct PartitionBlock *pb;
        int start_sect, nr_sects, blk, part, res = 0;
        int blksize = 1;        /* Multiplier for disk block size */
===8<--- becomes changing line 338 into lines 338-339
        struct PartitionBlock *pb;
        sector_t start_sect, nr_sects;
        int blk, part, res = 0;
        int blksize = 1;        /* Multiplier for disk block size */
===8<---

(I'm working without proper tools at the moment or I'd make a real diff.
Sorry.)

This fix may not be complete. The RDBs contain provisions for describing
the physical disk block size and how many physical blocks are used in a
file system's logical blocks. This MAY not work quite right large physical
block sizes.

{^_^}   Joanne Dow
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