Messages in this thread | | | Date | Wed, 20 Dec 2006 10:03:33 +0100 (CET) | From | Mikulas Patocka <> | Subject | Finding hardlinks |
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Hi
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?
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