> 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. SUSv3 requires st_ino/st_dev to be unique within a system so the application shouldn't need to bend over backwards. 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
