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?
Technically none (i.e. edit gcc specs or glibc includes). But persuading
all distribution builders to use this version is impossible. Plus there
are many binary programs that are unchangable.
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.
I think the best solution would be to drop -EOVERFLOW on st_ino and let
legacy 32-bit programs live with coliding inodes. They'll have anyway.
Mikulas
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