Messages in this thread | | | Date | Mon, 1 Jan 2007 23:47:06 +0100 (CET) | From | Mikulas Patocka <> | Subject | Re: Finding hardlinks |
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Hi!
>>>> 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. > > Ugh. Is it even legal to hardlink symlinks?
Why it shoudln't be? It seems to work quite fine in Linux.
> Anyway, cp -a is not the only application that wants to do hardlink > detection.
I tested programs for ino_t collision (I intentionally injected it) and found that CP from coreutils 6.7 fails to copy directories but displays error messages (coreutils 5 work fine). MC and ARJ skip directories with colliding ino_t and pretend that operation completed successfuly. FTS library fails to walk directories returning FTS_DC error. Diffutils, find, grep fail to search directories with coliding inode numbers. Tar seems tolerant except incremental backup (which I didn't try). All programs except diff were tolerant to coliding ino_t on files.
ino_t is no longer unique in many filesystems, it seems like quite serious data corruption possibility.
Mikulas
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