On Thu, Jan 04, 2007 at 12:43:20AM +0100, Mikulas Patocka wrote:
> On Wed, 3 Jan 2007, Frank van Maarseveen wrote:
> >Currently, large file support is already necessary to handle dvd and
> >video. It's also useful for images for virtualization. So the failing
> >stat()
> >calls should already be a thing of the past with modern distributions.
>
> As long as glibc compiles by default with 32-bit ino_t, the problem exists
> and is severe --- programs handling large files, such as coreutils, tar,
> mc, mplayer, already compile with 64-bit ino_t and off_t, but the user (or
> script) may type something like:
>
> cat >file.c <<EOF
> #include <sys/types.h>
> #include <sys/stat.h>
> main()
> {
> int h;
> struct stat st;
> if ((h = creat("foo", 0600)) < 0) perror("creat"), exit(1);
> if (fstat(h, &st)) perror("stat"), exit(1);
> close(h);
> return 0;
> }
> EOF
> gcc file.c; ./a.out
>
> --- and you certainly do not want this to fail (unless you are out of disk
> space).
>
> The difference is, that with 32-bit program and 64-bit off_t, you get
> deterministic failure on large files, with 32-bit program and 64-bit
> ino_t, you get random failures.
What's (technically) the problem with changing the gcc default?
Alternatively we could make the error deterministic in various ways. Start
st_ino numbering from 4G (except for a few special ones maybe such
as root/mounts). Or make old and new programs look differently at the
ELF level or by sys_personality() and/or check against a "ino64" mount
flag/filesystem feature. Lots of possibilities.
--
Frank
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