> >> I've came across this problem: how can a userspace program (such as for > >> example "cp -a") tell that two files form a hardlink? Comparing inode > >> number will break on filesystems that can have more than 2^32 files (NFS3, > >> OCFS, SpadFS; kernel developers already implemented iget5_locked for the > >> case of colliding inode numbers). Other possibilities: > >> > >> --- compare not only ino, but all stat entries and make sure that > >> i_nlink > 1? > >> --- is not 100% reliable either, only lowers failure probability > >> --- create a hardlink and watch if i_nlink is increased on both files? > >> --- doesn't work on read-only filesystems > >> --- compare file content? > >> --- "cp -a" won't then corrupt data at least, but will create > >> hardlinks where they shouldn't be. > >> > >> Is there some reliable way how should "cp -a" command determine that? > >> Finding in kernel whether two dentries point to the same inode is trivial > >> but I am not sure how to let userspace know ... am I missing something? > > > > The stat64.st_ino field is 64bit, so AFAICS you'd only need to extend > > the kstat.ino field to 64bit and fix those filesystems to fill in > > kstat correctly. > > There is 32-bit __st_ino and 64-bit st_ino --- what is their purpose? Some > old compatibility code? Yes. > > SUSv3 requires st_ino/st_dev to be unique within a system so the > > application shouldn't need to bend over backwards. > > I see but kernel needs to be fixed for that. Would patches for changing > kstat be accepted? I don't see any problems with changing struct kstat. There would be reservations against changing inode.i_ino though. So filesystems that have 64bit inodes will need a specialized getattr() method instead of generic_fillattr(). Miklos - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
