Re: >2G files patch wanted

Matti Aarnio (
Fri, 31 Jul 1998 09:52:07 +0300 (EEST)

> On 1998.07.30, Christoph Lameter <> wrote:
> > It seems we need some way of handling files >2G. Could someone hack the
> > kernel to do so?
> Solaris has implemented this and called it their "largefile" support.
> Is that a POSIX-like thing or did they just invent it themselves?
> Is that an amenable way to provide "large file" support in Linux?

There are two things in here.
In the EXT2 code we could do it now, however there is this "tiny" stack
of layers in between the EXT2 filesystem code, and the user program.

User program
- libc
- syscalls
- Linux VFS/buffer cache
EXT2 filesystem

Now the problem is that if we go and change internal file offset, and
size references within the VFS, we have to also do matching changes into
the buffer cache, but more importanly, WE CAN'T change existing syscalls
to use differently sized offset/size variables.

At Alpha those offsets/sizes are 64-bit, thus it has been possible for
the EXT2 code to have over 4GB files NOW at that platform! (2.1.* series)
The actual test for not allowing it is: BITS_PER_LONG < 64
(Meaning that 64-bit UltraSPARCs could do it too?)

In 2.3.* series we will introduce new syscalls with 64-bit sizes/offsets,
and associated internal operations for 32-bit systems too.

> -Dossy
> --

/Matti Aarnio <>

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