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?
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?
Mikulas
Miklos
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
