Re: Large File support and blocks.

From: Matti Aarnio (
Date: Thu Aug 31 2000 - 15:34:23 EST

On Thu, Aug 31, 2000 at 01:13:09PM -0700, Linda Walsh wrote:
> Ooops....the time frame is closer to today on part of this.
> While it may be a while before we hit the 1T limit on 1 single device,
> things like readpage, do so based of the inode -- which on a metadisk
> could have a filesize much larger than current physical device limits.
> So it seems that at least at the vnode level this is something that may
> have to go into the 2.4 series fairly soon, or am I missing something?
> Why are blocks int's vs. unsigned's ? Was it to pass back errno's in
> some cases?

        It is propably from reasoning of:

                "there is really no point in it, as at 32bit systems
                 int and long are same size, thus same limit comes
                 with both types."

        At 64-bit machines there is, of course, definite difference.

        Now our page-cache subsystem is based on the page cluster
        size (2^n times machine page size, where n is non negative
        integer), thus at i386 the page-cache can support up to
        PAGE_SIZE*2^32 -1 file offsets. (4k*4G = 16 T, larger page
        clusters drive the adressability higher -- and 64-bit machines
        drive it into cosmic magnitudes..)

        Some underlying block device subsystems can address that
        currently, some others have inherent 512 byte "page_size"
        with signed indexes... I think SCSI is in the first camp,
        while IDE is in second. (And Ingo has assured us that RAID
        code should handle this just fine too.)

        That part of the system needs to be verified/revised.
        (Verification to determine which need revision can be done
         now with document writing regarding the status, actual
         revisions are 2.5 issue.)

> --
> Linda A Walsh | Trust Technology, Core Linux, SGI
> | Voice: (650) 933-5338

/Matti Aarnio
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