Re: 2.4 and 2GB swap partition limit

[Andreas Dilger <adilger@turbolinux.com>]

Andi Kleen writes:
> On Mon, Apr 30, 2001 at 12:07:44PM -0700, David S. Miller wrote:
> But something must have been not working with it for mmaps/shlibs 
> (not executables); at least historically.
> At least I remember that all hell broke lose when you tried to update
> libc by cp'ing a new one to /lib/libc.so in the 1.2 days. cp should create a 
> new inode (it uses O_CREAT) so in theory it should be coherent by the inode 
> reference; but somehow it didn't use to work and random already running 
> programs started to segfault. This was long ago. I wonder if old
> GNU cp used O_TRUNC instead of O_CREAT, or was there some other kernel bug 
> with mappings (hopefully long since fixed). Anybody remembers? 

No, "cp" is still not a safe way to update libc, and I doubt it ever will be.
cp does _not_ create a new inode (unlike mv), so you are writing "garbage"
into the currently running executables.

NB: my open(2) says for O_CREAT "If the file does not exist it will be
created".  This is _not_ the same as O_EXCL, which will only mean that
open(2) will fail when it tries to create a new file.

Cheers, Andreas
-- 
Andreas Dilger                               Turbolinux filesystem development
http://sourceforge.net/projects/ext2resize/
http://www-mddsp.enel.ucalgary.ca/People/adilger/