On Thursday 28 December 2006 10:06, Benny Halevy wrote: > Mikulas Patocka wrote: > >>> If user (or script) doesn't specify that flag, it doesn't help. I think > >>> the best solution for these filesystems would be either to add new syscall > >>> int is_hardlink(char *filename1, char *filename2) > >>> (but I know adding syscall bloat may be objectionable) > >> it's also the wrong api; the filenames may have been changed under you > >> just as you return from this call, so it really is a > >> "was_hardlink_at_some_point()" as you specify it. > >> If you make it work on fd's.. it has a chance at least. > > > > Yes, but it doesn't matter --- if the tree changes under "cp -a" command, > > no one guarantees you what you get. > > int fis_hardlink(int handle1, int handle 2); > > Is another possibility but it can't detect hardlinked symlinks. It also suffers from combinatorial explosion. cp -a on 10^6 files will require ~0.5 * 10^12 compares... > It seems like the posix idea of unique <st_dev, st_ino> doesn't > hold water for modern file systems and that creates real problems for > backup apps which rely on that to detect hard links. Yes, and it should have been obvious at 32->64bit inode# transition. Unfortunately people tend to think "ok, NOW this new shiny BIGNUM-bit field is big enough for everybody". Then cycle repeats in five years... I think the solution is that inode "numbers" should become opaque _variable-length_ hashes. They are already just hash values, this is nothing new. All problems stem from fixed width of inode# only. -- vda - 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
